Article

Improving water quality in China: Environmental investment pays dividends

Authors:
  • Nanjing Institute of Geography and Limnology Chinese Academy of Sciences
  • Chongqing Institute of Green and Intelligent Technology,Chinese Academy of Sciences
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Abstract

This study highlights how Chinese economic development detrimentally impacted water quality in recent decades and how this has been improved by enormous investment in environmental remediation funded by the Chinese government. To our knowledge, this study is the first to describe the variability of surface water quality in inland waters in China, the affecting drivers behind the changes, and how the government-financed conservation actions have impacted water quality. Water quality was found to be poorest in the North and the Northeast China Plain where there is greater coverage of developed land (cities + cropland), a higher gross domestic product (GDP), and higher population density. There are significant positive relationships between the concentration of the annual mean chemical oxygen demand (COD) and the percentage of developed land use (cities + cropland), GDP, and population density in the individual watersheds (p < 0.001). During the past decade, following Chinese government-financed investments in environmental restoration and reforestation, the water quality of Chinese inland waters has improved markedly, which is particularly evident from the significant and exponentially decreasing GDP-normalized COD and ammonium (NH4⁺-N) concentrations. Our results demonstrate that the increasing GDP in China over the past decade did not occur at the continued expense of its inland water ecosystems. This offers hope for the future, also for other industrializing countries, that with appropriate environmental investments a high GDP can be reached and maintained, while simultaneously preserving inland aquatic ecosystems, particularly through management of sewage discharge.

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... Lakes have been a hot-spot for environmental studies, notably investigations of anthropogenic eutrophication, nutrient cycling (e.g., nitrogen, phosphorus, and carbon), and carbon dioxide emissions (CO 2 ) [1][2][3][4][5][6]. Inland lakes are sensitive to external changes induced by anthropogenic activities in their surrounding catchments, and are often characterized as sentinels of terrestrial environmental changes [7][8][9]. ...
... However, reductions in nutrients (e.g., in sewage discharge and agricultural fertilizer) at the catchment scale significantly enhance the quality of surface water. Previous studies have revealed that environmental investment can enhance inland water quality in China [6,14]. Tong et al., (2020Tong et al., ( , 2017 realized that advancements in municipal wastewater treatment reduced phosphorus concentrations and altered the nitrogen to phosphorus ratio in Chinese lakes [15,16]. ...
... In this study, quindecinnial observations of water quality in Taihu Lake were made, and indicators of development in its catchment were collected, including gross domestic product (GDP) and WD [6]. Spatiotemporal patterns of CO 2 and primary water parameters in Taihu Lake were analyzed. ...
Article
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Lakes are considered sentinels of terrestrial environmental change. Nevertheless, our understanding of the impact of catchment anthropogenic activities on nutrients and the partial pressure of carbon dioxide (pCO2, an important parameter in evaluating CO2 levels in water) is still restrained by the scarcity of long-term observations. In this study, spatiotemporal variations in nutrient concentrations (total nitrogen: TN, total phosphorus: TP, nitrate: NO3−–N, and ammonium: NH4+–N) pCO2 in Taihu Lake were analyzed from 1992 to 2006, along with the gross domestic product (GDP) and wastewater discharge (WD) of its catchment. The study area was divided into three zones to characterize spatial heterogeneity in water quality: the inflow river mouth zone (Liangxi River and Zhihugang River), transition zone (Meiliang Bay), and central Taihu Lake, respectively. It is abundantly obvious that external nutrient inputs from the catchment have a notable impact on the water parameters in Taihu Lake, because nutrient concentrations and pCO2 were substantially higher in the inflow river mouth zone than in the open water of Meiliang Bay and central Taihu Lake. The GDP and WD of Taihu Lake’s catchment were significantly and positively correlated with the temporal variation in nutrient concentrations and pCO2, indicating that catchment development activities had an impact on Taihu Lake’s water quality. In addition, pCO2 was negatively correlated with chlorophyll a and the saturation of dissolved oxygen, but positively correlated with nutrient concentrations (e.g., TN, TP, and NH4+–N) in inflow river mouth zone of Taihu Lake. The findings of this study reveal that the anthropogenic activities of the catchment not only affect the water quality of Taihu Lake but also the CO2 concentrations. Consequently, catchment effects require consideration when modeling and estimating CO2 emissions from the extensively human-impacted eutrophic lakes.
... China's landscape covers a wide spatial extent of 73.5 -135.1 • E and 3.8 -53.6 • N ( Fig. 1). Across China, natural and anthropogenic conditions exhibit wide spatiotemporal variations (Liu et al., 2020;Tong et al., 2017;Zhou et al., 2017). On the whole, air temperature is high in summer (June-August) but low in winter (December-February) under Fig. 1. ...
... The national border and river network data were sourced from the National Geomatics Center of China (www.ngcc.cn). The river codes are also shown (Table 1). the influence of the East Asian monsoon; precipitation decreases from the southeast to the northwest; the east has a low terrain but high population and cropland densities (Liu et al., 2020;Zhou et al., 2017). Moreover, along with China's rapid economic development and water pollution alleviation strategies, inland water quality has presented poor but gradual improvements over the past two decades (Tong et al., 2017;Zhou et al., 2017). ...
... The river codes are also shown (Table 1). the influence of the East Asian monsoon; precipitation decreases from the southeast to the northwest; the east has a low terrain but high population and cropland densities (Liu et al., 2020;Zhou et al., 2017). Moreover, along with China's rapid economic development and water pollution alleviation strategies, inland water quality has presented poor but gradual improvements over the past two decades (Tong et al., 2017;Zhou et al., 2017). ...
Article
Rivers serve as regulators of global climate by releasing greenhouse gases, burying particulate carbon, and connecting different ecosystem carbon pools. However, long-term organic carbon (OC) transport features across different Asian rivers are not well known due to unavailable data. Based on routinely monitored environmental and hydrological data during 2004-2018, this study investigated the spatiotemporal variations in dissolved (DOC) and particulate OC (POC) transport across 41 rivers in China. Across different rivers, both DOC (1.35 – 16.8 mg/L) and POC (0.27 – 4.48 mg/L) concentrations covered wide ranges. The DOC content was high in the north and low in the south, with significantly higher (t test, p < 0.01) values for rivers north of 30°N (5.39 ± 3.66 mg/L vs. 2.39 ± 1.14 mg/L). Human activities greatly influenced the riverine DOC and POC distributions. The riverine ammonia nitrogen (NH+ 4-N) content was positively correlated with DOC (r = 0.81 and p < 0.01) and explained 85.59% of its spatial variation. High vegetation coverage had significant effects on decreasing the riverine POC content, with r = -0.55 and p < 0.05. During 2004-2018, water pollution prevention and control strategies decreased DOC concentrations in 60.98% of rivers; meanwhile, anthropogenic vegetation restoration and dam construction led to POC content decreases in 90.48% of rivers. Importantly, along with DOC and POC changes, increasing DOC/POC ratios were found in 90.48% of the rivers, with 42.86% being significant, which indicated that Chinese rivers are losing their Asian features of low DOC/POC ratios due to artificial disturbance. This study is significant for accurately quantifying greenhouse gas emissions, carbon burial, and OC export to estuaries by Chinese rivers.
... Following the the 'reform and opening-up' policy implemented by the national government in 1978 to vigorously develop the economy, China's extensive socioeconomic development over the past several decades has taken place at the expense of the natural environment (Liu and Yang 2012, Liu et al 2013, Zhou et al 2017, Ma et al 2020b. The general deterioration of river water quality has become one of the most serious environmental threats to human health and ecosystem services nationwide (Zhou et al 2017, Ma et al 2020b, Huang et al 2021. ...
... Following the the 'reform and opening-up' policy implemented by the national government in 1978 to vigorously develop the economy, China's extensive socioeconomic development over the past several decades has taken place at the expense of the natural environment (Liu and Yang 2012, Liu et al 2013, Zhou et al 2017, Ma et al 2020b. The general deterioration of river water quality has become one of the most serious environmental threats to human health and ecosystem services nationwide (Zhou et al 2017, Ma et al 2020b, Huang et al 2021. This situation is more serious in North China, where deficient water resources increasingly impede the control of water pollution and the improvement of water quality , Ma et al 2020a, Huang et al 2021, Sun et al 2021, leading to water-pollution-induced severe water scarcity, for which this area has become a hot spot on a worldwide scale (Liu and Raven 2010, Guan et al 2014, Zhao et al 2015, Sun et al 2021. ...
... For example, from 2006 to 2010, more than 500 water pollution control projects were built, and in 2015 (MEE 2008), the water pollution control action plan (10-point water plan) demanded increased investment to ensure acceptable water quality and a reclaimed water utilization rate of up to 30% in the HRB by 2020 (TSC 2015). Although these efforts have yielded notable results (Liu and Yang 2012, Tong et al 2017, Huang et al 2021, the current water pollution situation is relatively severe compared to that in other regions due to a chronic water shortage (Zhou et al 2017, Ma et al 2020b. Considering that inadequate water quality can cause significant limitations to water availability (van Vliet et al 2017, Ma et al 2020a), the HRB is still facing increasing pressures on water security due to the scarcity of the available water resources (Zhang et al 2016, Sun et al 2021. ...
Article
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Rapid urbanization, population growth, and other intensive human activities have greatly altered natural hydrological conditions and matter cycling, which are the main causes of water quality deterioration in North China’s rivers. With the help of a 15-year (2005–2019) dataset of river water quality (1043 records from nine sites), this study investigated the spatiotemporal water quality patterns in the Yongding River Basin (YRB) in North China using a new water quality index (WQI-DET), which has been customized for China’s water quality classification scheme. Our results showed that the river water quality of the YRB has significantly improved due to the decreased surface runoff and an abrupt change of WQI-DET was observed in 2011. The elimination of anoxic conditions and the mitigation of nitrogen and phosphorus resulting from the construction of wastewater treatment plants and the improvement of treatment capacity are the main reasons for the improvement in river water quality. We also found that eutrophication is still not completely eradicated because of the high concentrations of NH4 ⁺ and total phosphorus. Our study suggests that for rivers in which runoff has decreased sharply, the water quality could be improved significantly by wastewater treatment facilities. At present, for the YRB, more effort is needed to eliminate eutrophication and dried-up river sections and thereby finally improve the river ecosystem. We concluded that more attention and effort should be given to river hydrological conditions, specific river ecological characteristics, and the increasingly important non-point source pollutants during the design of river restoration measures in North China.
... To mitigate the severe ecosystem degradation, the Chinese government initiated major investments in eco-environmental conservation and restoration projects in 2000. The investment in total environmental restoration across the China mainland has increased from almost nothing in 1994 to 1 trillion RMB Yuan in 2014 (Zhou et al., 2017). Whilst these factors have made China one of the world's leading investors in ecosystem restoration, there is also a general perception that the national restoration policies and actions have contributed a lot to improve the status of water quality across China (Zhou et al., 2017). ...
... The investment in total environmental restoration across the China mainland has increased from almost nothing in 1994 to 1 trillion RMB Yuan in 2014 (Zhou et al., 2017). Whilst these factors have made China one of the world's leading investors in ecosystem restoration, there is also a general perception that the national restoration policies and actions have contributed a lot to improve the status of water quality across China (Zhou et al., 2017). However, no study has yet attempted to describe the quantitative relationship between the indices of different restoration projects targeting either pollution sources (the place when pollution was generated) or pollution sinks (natural aquatic ecosystems like rivers) and ecosystem indices (nutrients, biological communities, etc.) across large space and time scale. ...
... The effects of urbanization (hydromorphology and hydrological alteration, run off pollution) are likely to have suppressed the level of biotic recovery of freshwater macroinvertebrates that may have occurred from restoration efforts in isolation by increasing the role of other stressors (Gál et al., 2019). Despite this urban cover growth, water quality of Chinese inland waters has clearly improved generally over recent decades with restoration efforts (Zhou et al., 2017). ...
Article
Ecosystem degradation and biodiversity loss have been caused by economic booms in developing countries over recent decades. In response, ecosystem restoration projects have been advanced in some countries but the effectiveness of different approaches and indicators at large spatio-temporal scales (i.e. whole catchments) remains poorly understood. This study assessed the effectiveness of a diverse array of 440 aquatic restoration projects including wastewater treatment, constructed wetlands, plant/algae salvage and dredging of contaminated sediments implemented and maintained from 2007 to 2017 across more than 2000km² of the northwest Taihu basin (Yixing, China). Synchronized investigations of water quality and invertebrate communities were conducted before and after restoration. Our analysis showed that even though there was rapid urbanization at this time, nutrient concentrations (NH4+-N, TN, TP) and biological indices of benthic invertebrate (taxonomic richness, Shannon diversity, sensitive taxon density) improved significantly across most of the study area. Improvements were associated with the type of restoration project, with projects targeting pollution-sources leading to the clearest ecosystem responses compared with those remediating pollution-sinks. However, in some locations, the recovery of biotic communities appears to lag behind nutrients (e.g. nitrogen and phosphorus), likely reflecting long-distance re-colonization routes for invertebrates given the level of pre-restoration degradation of the catchment. Overall, the study suggests that ecological damage caused by recent rapid economic development in China could potentially be mitigated by massive restoration investments synchronized across whole catchments, although these effects could be expected to be enhanced if urbanization rates were reduced at the same time.
... Firstly, due to the influence of different economic, social and environmental factors, there are significant differences in industrial water pollution among different regions in China Huang et al., 2019). Such spatial heterogeneity of industrial water pollution has alo been revealed in prior studies (e.g., Becker and Randy, 2016;Duan et al., 2012;Zhou et al., 2017) which demonstate that the distribution of industrial water pollution intensity is affected by many macro and micro factors, including the level of regional economic development, the degree of industrialization, the urbanization level, the amount of enterprise aggregation and market competition. Therefore, a first challenge we need to address is the spatial heterogeneity of industrial water pollution across different regions in China. ...
... Secondly, due to the significant challenge of obtaining data that accurately represents all geographical regions in China, prior relevant studies focused on watershed land use and lake morphology, and their spatial and temporal resolution was usually limited (Chen et al., 2015;Huang et al., 2019;Zhou et al., 2017). Some policies may work in a wide range of regions, but some are not effective in all places, and the governance of such policies-such as the Clean Water Act in the United States-may vary depending on location Fuller and Font, 2019;Schmalensee and Stavins, 2019). ...
... China's central and western regions have taken on too many heavily polluting enterprises; however, limited by water resources and technical conditions, the central and western regions of China are facing a huge risk of industrial water pollution . Due to the limitations of the available data, most of the current research on industrial water pollution are based on river basins and lakes, and they do not comprehensively point out the overall spatial differences of industrial water pollution in China (Chen et al., 2015;Huang et al., 2019;Zhou et al., 2017). Therefore, from the perspective of industrial water pollution intensity, we study the industrial pollution situation in China's central and western regions. ...
Article
The Action Plan for Water Pollution Prevention and Control (i.e., the "10-Point Water Plan") is a regulation formulated by China to prevent and control water pollution and ensure China's water safety. To test the policy effect of the "10-Point Water Plan", we use data from 269 cities for the period from 2012 to 2017 to examine whether the implementation of the plan can help reduce the intensity of industrial water pollution. The results show that the industrial water pollution intensity in Central and Western China is significantly higher than that in other regions, and the implementation of the "10-Point Water Plan" significantly reduces industrial water pollution intensity in China. We further find that upgrading industrial structures and technological innovation are effective ways to ameliorate the intensity of industrial water pollution. In terms of spatial heterogeneity, the impact of the "10-Point Water Plan" on reducing industrial water pollution is smaller in areas with high environmental regulation intensity than in areas with low environmental regulation intensity. We also find a strong inhibitory effect of environmental regulations on industrial water pollution intensity in areas with low environmental regulation intensity. Our findings support the positive policy effect of the "10-Point Water Plan" and provide significant policy implications for water pollution prevention and control actions in China and other countries.
... Spatial measurements of dissolved carbon (DC) contribute to our understanding of C sources and cycling in aquatic systems. Several factors govern dissolved carbon in lakes, including mineralization rates, electrical conductivity (EC), soil types and landscapes, agricultural activities, hydrology, and anthropogenic discharge (Kothawala et al., 2014;Song et al., 2017;Zhou et al., 2017). It has been found that N and P are strongly associated with eutrophication in lakes. ...
... We included the following three stochiometric indicators in water bodies: dissolved carbon, total nitrogen, and total phosphorus concentrations, hereafter abbreviated to [DC], [TN], and [TP] respectively. Data for water temperature, chlorophyll-a concentration, Secchi disk depth, and EC were included because these variables are generally assumed to affect water chemistry (Song et al., 2017;Wang & Du, 1998;Zhou et al., 2017). Because chlorophyll-a is common to all photosynthetic organisms, and it is relatively easy and rapid to quantify (Felip & Catalan, 2000), here we replaced the phytoplankton biomass by chlorophyll-a. ...
Article
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Given the differences in geomorphology, climate, hydrology, and human activities in various regions, lake chemometrics may also vary. However, the spatial distribution of lake chemistry and the factors affecting such pattern are still unclear. Here, we collected data for carbon, nitrogen, and phosphorus from published literature and databases in 224 lakes and calculated the trophic status index to represent the nutrient classification state of lakes. We found that lakes with high carbon concentrations were located in the Tibet-Qinghai Limnetic Region of western China, whereas lakes with high nitrogen and phosphorus concentrations were located in the Inner Mongolia-Xinjiang Limnetic Region and Northeast Limnetic Region of northern China. Areas with larger cropland and urban residential land (such as the junction of the three lake regions, i.e., the Northeast Limnetic Region, East Limnetic Region, and Inner Mongolia-Xinjiang Limnetic Region) tended to have lakes with high nitrogen and phosphorus concentrations. Our analysis suggested that spatial distribution of carbon, nitrogen, and phosphorus concentrations reflect the effect of climate, geomorphology, and land use in each lake region and nationwide.
... However, urbanization and economic development has brought an acute problem of natural ecosystem degradation, especially water pollution (Liu et al., 2016). To ameliorate the negative impacts of accelerated aquatic environmental degradation, investments in ecosystem restoration for improving China's natural water quality increased dramatically from being negligible in 1994 to 1000 billion RMB in 2014 (Zhou et al., 2017). Based on national records of dissolved oxygen (DO), chemical oxygen demand (COD), and ammonium (NH 4 + ), Zhou et al. (2017) claimed that China's increasing gross domestic product (GDP) during the 2006-2015 period was not at the expense of its inland waters due to concurrent restoration efforts. ...
... To ameliorate the negative impacts of accelerated aquatic environmental degradation, investments in ecosystem restoration for improving China's natural water quality increased dramatically from being negligible in 1994 to 1000 billion RMB in 2014 (Zhou et al., 2017). Based on national records of dissolved oxygen (DO), chemical oxygen demand (COD), and ammonium (NH 4 + ), Zhou et al. (2017) claimed that China's increasing gross domestic product (GDP) during the 2006-2015 period was not at the expense of its inland waters due to concurrent restoration efforts. However, the wider extent of improvement remains unknown as the study did not consider any changes in biological status, whilst other studies incorporating biotic indices (e.g. ...
Article
Understanding how abiotic and biotic components respond to aquatic ecosystem restoration is pivotal for sustainable development in the face of economic development and global environmental change. However, the post-restoration monitoring and evaluation of aquatic ecosystems across large spatial and temporal scales is underfunded or not well documented, especially outside of Europe and North America. We present a meta-analysis of abiotic and biotic indices to quantify post-restoration (2 month–13 years) effects from reported aquatic restoration projects throughout the China-mainland, incorporating 39 lentic and 36 lotic ecosystems. Decreases in dissolved nutrients (total nitrogen, ammonia nitrogen and total phosphorus) post-restoration were rapid, but tended to slow after about 9.3 years. Response ratios summarizing biodiversity responses (incorporating phytoplankton, invertebrates, vascular plants, fish and birds) typically lagged behind abiotic changes, suggesting longer timescales are needed for biotic indices to recover. Time since restoration interacted with lentic project size, showing even with the same proportional efforts of restoration, larger lentic ecosystems responded much more slowly than smaller ones. Spatial heterogeneity, reflecting the effects of different restoration approaches (e.g., sewage interception, polluted sediment dredging, artificial wetlands, etc.), had a significantly stronger effect on biotic than abiotic indices, particularly in rivers compared to standing waters. This reflects the complexity of fluvial ecosystem dynamics, and hints at a limitation in the reinstatement of ecological processes in these systems to overcome issues such as dispersal limitations. Overall, the different timelines and processes by which abiotic and biotic indices recover after restoration should be taken into account when defining restoration targets and monitoring programs. Our study illustrates the value of long-term aquatic ecosystem monitoring, especially in China given the scale and magnitude of ongoing restoration investments in the country.
... Moreover, Li et al. (2020a) have found that restoration projects in urban river networks can reduce CH 4 production in water column and emission at the water-air interface. With the continuous improvement of infrastructure and the increase of environmental protection investment, urban rivers that used to be heavily polluted have been extensively restored and improved (Mi et al., 2015;Zhou et al., 2017). Such relevant ecological restoration measures may further alter the potential of riverine CH 4 and N 2 O emissions and lead to their strong variability Smith et al., 2017). ...
... The comprehensive treatment of the water environment is the most important content for the sustainable development of contemporary cities . With the development of the social economy, a large number of urban rivers have been effectively protected, especially in China (Tang et al., 2022;Xu et al., 2019;Zhou et al., 2017). This study showed a clear relevance of CH 4 and N 2 O concentrations in urban polluted streams with watershed comprehensive improvements (Figs. 5 and 6). ...
Article
Streams draining urban areas are usually regarded as hotspots of methane (CH4) and nitrous oxide (N2O) emissions. However, little is known about the coupling effects of watershed pollution and restoration on CH4 and N2O emission dynamics in heavily polluted urban streams. This study investigated the CH4 and N2O concentrations and fluxes in six streams that used to be heavily polluted but have undergone different watershed restorations in Southwest China, to explore the comprehensive influences of pollution and restoration. CH4 and N2O concentrations in the six urban streams ranged from 0.12 to 21.32 μmol L⁻¹ and from 0.03 to 2.27 μmol L⁻¹, respectively. The calculated diffusive fluxes of CH4 and N2O were averaged of 7.65 ± 9.20 mmol m⁻² d⁻¹ and 0.73 ± 0.83 mmol m⁻² d⁻¹, much higher than those in most previous reports. The heavily polluted streams with non-restoration had 7.2 and 7.8 times CH4 and N2O concentrations higher than those in the fully restored streams, respectively. Particularly, CH4 and N2O fluxes in the fully restored streams were 90% less likely than those found in the unrestored ones. This result highlighted that heavily polluted urban streams with high pollution loadings were indeed hotspots of CH4 and N2O emissions throughout the year, while comprehensive restoration can effectively weaken their emission intensity. Sewage interception and nutrient removal, especially N loadings reduction, were effective measures for regulating the dynamics of CH4 and N2O emissions from the heavily polluted streams. Based on global and regional integration, it further elucidated that increasing environment investments could significantly improve water quality and mitigate CH4 and N2O emissions in polluted urban streams. Overall, our study emphasized that although urbanization could inevitably strengthen riverine CH4 and N2O emissions, effective eco-restoration can mitigate the crisis of riverine greenhouse gas emissions.
... Evaluation of both the negative and positive effects of anthropogenic activities on water quality in coastal embayments or estuaries requires an understanding of the dynamic trends in environmental variation and eutrophication (Kennish, 2002;Lotze et al., 2006;Lu et al., 2018). Although proper management strategies (e.g., reduction in both N and P inputs and/or habitat remediation) are of equal importance for the health of coastal water quality (Zhou et al., 2017), exploring the source of pollution and the impacts of human pressures are urgent for many coastal ecosystems, as the adverse effects from environmental problems usually predate protection measures. Previous studies on the water quality of Laizhou Bay have mostly focused on several biochemical parameters, such as N and P Jiang et al., 2018). ...
... Various human activities, such as pollution inputs, the destruction of wetlands, the alteration of coastal habitats, and overfishing, have contributed greatly to the environmental changes of extensive coastal zones worldwide (Kennish, 2002), which gradually develop into many serious environmental pollution problems and thereby inversely impact humans (Zhou et al., 2017;Zhu et al., 2020). To date, the riverine inflow remains a primary pathway by which pollutants enter coastal environments, accounting for ~50 % of the pollutant inputs (Kennish, 2002;Radach and Pätsch, 2007). ...
Article
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Laizhou Bay is plagued by many environmental problems (e.g., acidification and eutrophication) that are likely to increase in the coming decades along with social and demographic trends. We thus conducted 12 cruises from July 2019 to December 2021 in the Laizhou Bay to evaluate the potential influences of human activities on its eutrophication status. The results showed that the parameters of dissolved inorganic nitrogen (DIN) and oxygen (DO) exceeded the water quality standard in some cases during the past 3 years, suggesting DIN and DO were the crucial factors controlling water quality in the bay. Meanwhile, DIN was identified as a major pollutant in the region, and played an important role in driving the phytoplankton dynamics. Furthermore, with the increases in human-related nutrient inputs (especially DIN), the bay environment reached the mild eutrophication level and was probably at risk from excessive nutrient loads at present, further evidencing the ecosystem degradation.
... This could be attributable to the strict control of NH 3 -N since the government implemented a three-level zoning system (basin-control area-control unit) and treated NH 3 -N as a binding indicator for total control during the 12th 5-year plan ). In addition, it was found that NH 3 -N was negatively correlated with I in WEPM (r = − 0.2193, p < 0.05) (Fig. 3), indicating that increased government financing investments for the environment in recent years have contributed much to the reduction NH 3 -N concentration, which agrees with the finding of Zhou et al. (2017). ...
... Hence, during mining and fertilizer production, sewage and wastewater discharges would increase the TP concentration and affect the water environment. Additionally, environmental investment was significantly correlated with TP control (r = − 0.00023, p < 0.01) ( Table S4), indicating that national environmental investment paid dividends for the improving water quality of China (Zhou et al. 2017). ...
Article
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Water quality deterioration is a prominent issue threatening water security worldwide. As the largest river in China, the Yangtze River Basin is facing severe water pollution due to intense human activities. Analyzing water quality trends and identifying the corresponding driver factors are important components of sustainable water quality management. Thus, spatiotemporal characteristics of the water quality from 2008 to 2020 were analyzed by using a Mann-Kendall test and rescaled range analysis (R/S). In addition, multi-statistical analyses were used to determine the main driving factors of variation in the permanganate index (CODMn), ammonia nitrogen (NH3-N) concentration, and total phosphorus (TP) concentration. The results showed that the mean concentrations of NH3-N and TP decreased from 0.31 to 0.16 mg/L and 0.16 to 0.07 mg/L, respectively, from 2008 to 2020, indicating that the water quality improved during this period. However, the concentration of CODMn did not reduce remarkably. Based on R/S analysis, the NH3-N concentration was predicted to continue to decrease from 2020 to 2033, whereas the CODMn concentration was forecast to increase, highlighting an issue of great concern. In terms of spatial distribution, water quality in the upstream was better than that of the mid-downstream. Multi-statistical analyses revealed that the temporal variation in water quality was predominantly influenced by tertiary industry (TI), the nitrogen fertilizer application rate (N-FAR), the phosphate fertilizer application rate (P-FAR), and the irrigation area of arable land (IAAL), with contribution rates of 15.92%, 14.65%, 3.46%, and 2.84%, respectively. The spatial distribution of CODMn was mainly influenced by TI, whereas that of TP was primarily determined by anthropogenic activity factors (e.g., N-FAR, P-FAR). This study provides deep insight into water quality evolution in the Yangtze River Basin that can guide water quality management in this region.
... NH 3 -N was negatively associated with I in WEPM (r=-0.2193, p<0.05), which demonstrated that increasing government nanced investments in environment recent years have contributed much to the decrease of the concentration of NH 3 -N, which was in highly consistent with the view from Zhou, et al(Zhou et al. 2017).In China's inland surface water, COD Mn and NH 3 -N that indicating concentration of organic matter and nitrogen were the major types of pollutants(You et al. 2019). Thus, it is quite signi cant to detect the drivers of the COD Mn and NH 3 -N spatiotemporal variation in Yangtze River Basin. ...
... Additionally, environmental investment was signi cantly associated with TP control (r=-0.00025, p<0.05), which indicated that national environmental investment paid dividends for the improving water quality of China(Zhou et al. 2017). However, the pollution of TP caused by imperfect mining facilities would also threaten the surface water environment. ...
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Water quality deterioration is a prominent issue threatening water security throughout the world. Yangtze River Basin, as the largest river in China, is facing severe water pollution due to the intensive human activities. The analysis of water quality trends and identification of driver factors are significant for sustainable water quality management. Thus, spatiotemporal characteristics of the water quality from 2008 to 2020 were analyzed by using Mann–Kendall test and Rescaled Range analysis (R/S), respectively. Also, the drivers of the key monitoring indicators including permanganate index (COD Mn ), ammonia nitrogen (NH 3 -N) and total phosphorus (TP) were detected by multi-statistical analyses. The results showed that water quality was significantly improved, which was reflected from its mean concentration of NH 3 -N and TP, decreasing from 0.31 mg/L to 0.16 mg/L and 0.16 mg/L to 0.07 mg/L, respectively. However, the concentration of COD Mn did not remarkably decline in the past 13 years. The R/S analysis indicated that the concentration of NH 3 -N would continue to decrease in the next 13 years, while COD Mn might continue to increase, which should be of great concern to us. In terms of spatial distribution, the water quality in the upstream was significantly better than that of the mid-downstream. Multi-statistical analyses revealed that the temporal evolution of water quality was predominantly influenced by tertiary industry (TI), nitrogen fertilizer application rate (N-FAR), phosphate fertilizer application rate (P-FAR) and irrigation area of arable land (IAAL), with a contribution rate of 15.92%, 14.65%, 3.46% and 2.84% respectively. The spatial distinction of COD Mn was mainly influenced by TI, while TP is primarily determined by anthropogenic activity factors including N-FAR, P-FAR and so on. This study was expected to provide deep insights into water quality evolution and foundations for water quality management in Yangtze River Basin.
... Both of these suggest that the substantial interannual variability in CO 2 was partly explained by the changing nutrient loading. It is worth to note that large interannual variability in inland water nutrient loadings have been found (Zhou et al. 2017; Fig. S2), suggesting the importance of long-term measurements to accurately estimate lake CO 2 budgets and better understand their roles in the carbon cycle. For example, the CO 2 emission flux of the eutrophic part of the lake was estimated to be 30 mmol m À2 d À1 based on measurements from 2000 to 2015 (Xiao et al. 2020a), which was lower than the value in the presented study (42.1 mmol m À2 d À1 ). ...
... Our results showed that the pCO 2 and CO 2 fluxes decreased with increasing temperature, especially for Meiliang Bay, which is affected by frequent algal blooms. Meanwhile, the temperature effect was amplified with an increasing ratio of Chl a to TN. Decreasing lake N loadings have been reported due to environmental protection actions to improve water quality (Zhou et al. 2017;Qin et al. 2019), but algal blooms have increased with climate warming (Kosten et al. 2012;Ho et al. 2019). Considering the significant role of algal blooms in lake CO 2 variability (Balmer and Downing 2011;Pacheco et al. 2014), future warmer climate would have a large role in lake CO 2 flux via stimulating algal blooms. ...
Article
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Eutrophication and warming are changing the functioning of lake ecosystems, and their impacts on lake carbon dioxide (CO2) variability have received increasing attention. However, how eutrophication and warming change lakes' carbon cycle has not been determined. Here, the surface partial pressure of CO2 (pCO2) and CO2 flux in Lake Taihu, a large and eutrophic lake in eastern China, was investigated based on monthly samplings over a 24‐yr period (1992–2015), during which the lake experienced profound anthropogenic and climate changes. The results showed that eutrophication caused by nutrient enrichment plays a role in three aspects: (1) nutrient concentrations controlled the CO2 variability on decadal scales; (2) peak pCO2 and CO2 fluxes occurred in river mouths due to large external nutrient loading inputs; and (3) eutrophication effects on CO2 varied among subzones, which was linked to external inputs and in‐lake primary production. Meanwhile, temperature controls the seasonal variation in CO2 by stimulating primary production, leading to significantly lower pCO2 and CO2 fluxes in warm seasons with algal blooms. Further analysis suggested that temperature effects varied spatially and temporally, high nutrient loading may confound the temperature effects via stimulating CO2 production. To our knowledge, this study presents the longest field measurements (24 yr) of CO2 from such large and ice‐free freshwater lakes with monthly surveys, which may provide a powerful example to demonstrate that eutrophication and warming can shape CO2 variability from a temporal perspective. Future studies should focus on the interactive warming and eutrophication effects to accurately predict future CO2 emission.
... In addition, a recent nationwide assessment revealed that 29% of the 107 surveyed lakes experienced eutrophication problems (Ministry of Ecology and Environment, 2019). Since 2000, China has made considerable efforts to mitigate the pollution of lakes, including the introduction of a wide range of strict laws, the establishment of national wastewater discharge standards and pollutant cap-control targets, and the initiation of the National Water Pollution Control Action Plan (Zhou et al., 2017;Tong et al., 2017). Lake Dianchi is one of the three most hyper-eutrophic large lakes in China (Huang et al., 2019), and has received considerable attention owing to its severe pollution and the dire ramifications for people living in the surrounding watersheds. ...
... Lake Dianchi is one of the three most hyper-eutrophic large lakes in China (Huang et al., 2019), and has received considerable attention owing to its severe pollution and the dire ramifications for people living in the surrounding watersheds. Previous studies have shown that, after decades of intensive restoration efforts (Tong et al., 2017;Zhou et al., 2017), the lake water quality has steadily improved, although not to the degree expected (Wu et al., 2017). However, for eutrophic lakes during the recovery period, there are several aspects that are largely unknown: (a) What are roles of internal nutrient fluxes in interannual and seasonal variations of nutrient concentration and algal biomass? ...
Article
Nutrient dynamics in lakes are determined by the combined effects of external and internal nutrient fluxes. However, the feedback loop of nutrient fluxes and water quality changes is still an open question. An integrated three-dimensional flux tracking approach based on the Environmental Fluid Dynamics Code model was established to quantify the long-term dynamic changes in external and internal processes in Lake Dianchi (one of the three most hyper-eutrophic lakes in China), and to explore the potential causes of water quality improvement during 2012–2018. The long-term trends and relative influences of nutrient fluxes on water quality were identified. The results showed that the inflow flux was the largest input source and declined by 50% between 2003 and 2012, which was followed by a stable trend from 2012 to 2018. The second largest input source was benthic release, which exhibited a significant interannual reduction. Algae sedimentation was the largest removal process, and declined by 45% between 2012 and 2018. An integrated analysis demonstrated that, following an external loading reduction prior to 2012, the positive feedback of internal fluxes promoted water quality improvement during 2012–2018. Considering the long timescale of the nutrient-flux feedback mechanism, reducing external loading is still the top priority for a long-term virtuous cycle of water quality in the process of eutrophic lake restoration.
... and positively affecting drinking-water quality (Zhou et al., 2017;Mo, 2007). ...
... Zhang et al. (2010) qualitatively analyzed the implementation of China's green credit policy at the national and provincial levels and pointed out that the implementation of the policy had an impact on high pollution and high energy consumption industries. However, due to the ambiguous details and inconsistent implementation standards of China's green credit policy at this step, the policy effect was not fully realized (Zhou et al., 2017). used an evolutionary game model to examine the government, businesses, and banks' behavior choices in implementing green credit. ...
Article
Green credit policy (GCP) can achieve economic growth and environmental conservation, notably by lowering air pollutants (PM2.5). Green credit is a significant component of China's green financing for environmental regulation and achieving carbon neutrality. In this paper, to understand the causal relationship between GCP and PM2.5, we apply a bootstrap full-sample Granger causality test, parameter stability test, and quantile-on-quantile test for the period between 2003:M01 to 2019:M12. The result shows a bidirectional relationship and reveals that GCP has varied environmental implications in its early and mature stages because of a low percentage of green credit and a lack of motivation for financial institutions. In the long run, GCP and PM2.5 interaction confirm the favorable effects of GCP on PM2.5 as the green credit system improves. For robustness, we used quantile-based granger causality to evaluate the causative link between GCP and PM2.5. In light of the findings, this research advises legislative reforms and stresses the relevance of green credit in improving air quality. This study adds additional evidence that air pollution affects green credit policies. Air quality being a leading indicator helps firms anticipate changes in bank credit preferences and alter financing techniques.
... Analysis of the correlation between river environmental quality and pollutant emissions, national economic development level, and environmental pollution control investment revealed that the reduction of ammonia nitrogen and COD emissions [20] and the increase in GDP and environmental pollution control investment are the main reasons for the improvements that have occurred in surface water quality [21,22]. ...
Article
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To investigate the monitoring history and long-term change trends in surface water quality in China since the reform and opening up, the history of surface water environment monitoring is summarized, including monitoring scope, monitoring methods, and technical requirements. Temporal and spatial patterns of surface water quality in China were analyzed based on the monitoring results. In the past 40 years, the monitoring targets for surface water quality have been continuously improved, the frequency of monitoring has become more science-based, and the monitoring indicators are now comprehensive. Overall, the temporal change trend in surface water quality has followed a “fluctuating changes stage—rapid deterioration stage—fluctuations stalemate stage—rapid improvement stage” pattern. However, the current regional surface water quality is still in a polluted status, and there is a gap between surface water quality status and the goal of building a well-off society. At present, China’s surface water pollution is prone to high numbers of incidents and the treatment of surface water pollution has entered a crucial stage. The potential for the continuous reduction of major pollutant discharges has become more challenging, and the marginal cost for pollution control has increased. It is very difficult to comprehensively solve the outstanding water environment problems. In addition to strengthening the existing work on surface water quality control, it is also necessary to strengthen the work of risk identification, early warning, and regulation implementation of the surface water environment. During the 14th year plan period (2021–2025), the overall planning on water resources, water ecology, and water quality will be implemented, and beautiful rivers and lakes will be created.
... The Eastern Plain Region (EP) and Northeast China Region (NC) were typical high anthropogenic impact regions ( Fig. 3 ). However, the trophic status of lakes in the better developed EP region was, surprisingly lower than NC, as significant efforts have been made in EP to restore and conserve aquatic ecosystems (Appendix A Fig. S4), leading to improved water quality throughout the recent decade ( Tong et al., 2017 ;Zhou et al., 2017 ;Huang et al., 2019 ). However, the lake catchments in NC are mainly used for agriculture and fishery ( Wang and Dou, 1998 ), and amble use of fertilizer has considerably reduced water quality ( Piao and Wang, 2011 ;Song et al., 2012 ;Xue et al., 2019 ;Yuan et al., 2018 ). ...
Article
Anthropogenic and natural disturbance to inland aquatic ecosystems displays a notable spatial difference, yet data to measure these differences are scarce. This study encompasses 217 lakes distributed over five lake regions of China and elucidates the environmental factors determining the spatial variability of the water quality and trophic status. A significant correlation between human modification index in surrounding terrestrial systems (HMT) and trophic status of lake ecosystems (TSI) was found, and the regression slope in each region was similar except in the Qinghai-Tibet Plateau region. It was further noted that the pattern of environmental factor network (EF network) differed among freshwater and saline lakes. The EF network was complex for freshwater lakes in less human-influenced areas, but intensive man-made influence disrupted most relationships except for those between total nitrogen, total phosphorus, chlorophyll- a , and water turbidity. As for regions including saline lakes, correlations among water salinity and organic forms of carbon and nitrogen were apparent. Our results suggest that HMT and EF network can be useful indicators of the ecological integrity of local lake ecosystems, and integrating spatial information on a large scale provides conservation planners the option for evaluating the potential risk on inland aquatic systems.
... Common symptoms of eutrophication include turbid water, dense algal blooms, loss of biodiversity and loss of recreation and esthetic value (Huisman et al., 2018;Ho et al., 2019). To mitigate these negative effects of eutrophication, the Chinese government is working to reduce nutrient inputs and restore the functionality of lake ecosystems since 2000 (Zhou et al., 2017;Fu et al., 2021). However, eutrophication remains a major problem, either because external loading has not been reduced to sufficiently low levels or because of internal lake mechanisms, chemical or biological, that prevent or delay recovery (Søndergaard et al., 2007;Van Meter et al., 2018;Xu et al., 2021). ...
Article
Response of aquatic organisms to eutrophication have been well reported, while less studies are available for the recovery of eutrophic lakes following a reduction in the external loading, especially for systems where nitrogen is reduced but the phosphorus concentration is maintained high due to internal loading. Diatoms are nitrate (NO3-N) opportunists but can also use ammonium (NH4-N). They may, therefore, be more sensitive to nitrogen reduction than other algae that typically prefer NH4-N. We document the variations of nutrients and diatoms in subtropical, eutrophic Lake Taihu over 28 yr during which a reduction of the external loading resulted from lake management. According to the results of change point analysis, data on environmental variables were divided into two periods (P1: 1992-2006; P2: 2007-2019) with two different seasons (WS: Winter-Spring; SA: Summer-Autumn), respectively. Compared with P1-WS, the concentration of NH4-N decreased significantly whereas NO3-N showed no significant change in P2-WS. In contrast, NH4-N concentrations were low and showed no significant changes in P1-SA and P2-SA and NO3-N decreased significantly in the latter period. Accordingly, NO3-N: NH4-N mass ratios in P1-SA and P2-WS were all significantly higher than those in P2-SA and P1-WS, respectively. The biomass of WS diatom increased significantly and the timing of the peak biomass shifted from P1-SA to P2-WS since 2007. The SEM analysis showed that NO3-N was retained as a statistically significant predictor for diatom biomass in P1-SA and significant effects of windspeed, zooplankton and NH4-N on diatom biomass in P2-WS. Windspeed and zooplankton have further changed the biomass of diatoms in the case of declining inorganic nitrogen. We conclude that the magnitude of vernal suppression or stimulation of diatom assemblages has increased, concomitant with the variations of NH4-N and NO3-N: NH4-N mass ratios. Diatoms response to NH4-N or NO3-N is apparently changing in response to water temperature in this eutrophic shallow lake. Thus, parallel reductions in external nitrogen loading, along with variations in dominant inorganic nitrogen, will stimulate the growth of diatom and therefore increase the total biomass of phytoplankton in still high internal phosphorus loading, which is should be regarded as a good sign of restoration measures.
... Mainly, garment production requires higher water consumption, especially the dyeing stage. From this stage, large amounts of water resources are used and polluted [148]. There are various ways to apply circularity in the supply chain. ...
Chapter
The textile and food industries are two sectors whose water consumption generates a significant environmental footprint. The production of industries must be focused on sustainability if the organizations for these sectors are improved. Therefore, it is necessary to focus the analysis on the sustainable alternatives applied in the supply chain by applying circular strategies. This chapter presents water use and its water footprint in the industries above. In addition, some strategies applied to improve water footprint levels—which involve water consumption and pollution—through circular strategies are presented. Finally, some trends and external and internal factors that can determine the successful implementation of a sustainable supply chain are presented. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
... However, the WQS may not be suitable for the circumstances in China (Zhao et al., 2016). Thus, although a series of regulation to reduce environmental pollution were implemented by Chinese government, it appears to have little effect, which to some extent indicated a dilemma for the environmental regulation in China (Zhou et al., 2017). The lack of strong scientific bases for China's WQS pose major limitations of current WQS. ...
Article
Error estimation and data fusion are critical to improving the accuracy of global model- and satellite-based precipitation products for practical applications. However, they face challenges over vast areas of the world due to limited ground observations. Triple collocation (TC) method can overcome this limitation and provide an efficient way for error estimation without the “ground truth” and thus also for data fusion, by leveraging multi-source observations and model outputs, which have been increasingly available in recent years. In this work, we conducted a comprehensive study on error estimation and data fusion of a number of global gridded precipitation products over the Yangtze River basin from 2015 to 2018 using TC and multiplicative TC (MTC) methods. We use three satellite-based precipitation products such as the IMERG Final (IMERG-F), PERSIANN-CDR (PCDR) and SM2RAIN-ASCAT (SM2R), and one reanalysis dataset ERA5 which contains precipitation estimates. They were grouped into two TC triplets based on different combinations: IMERG-F+SM2R+ERA5 and PCDR+SM2R+ERA5. For performance evaluation, the TC-based error estimation methods were compared to the traditional method using rain gauge data, and the TC-based data fusion methods were compared with two widely-used data fusion methods Bayesian Model Averaging (BMA) and Random Forest based MErging Procedure (RF-MEP). Results showed that ERA5 had the best performance with the largest correlation coefficient (CC, 0.435), while PCDR had the worst accuracy with the smallest CC (0.304) and the largest absolute relative bias (RB, 0.365). TC tended to underestimate the root mean square error (RMSE) with respect to the traditional gauged-based method, but MTC showed a consistent result owing to the employment of a multiplicative error model. The performance of TC-based data fusion methods had no significant difference from BMA and RF-MEP. All data fusion results were better than the original triplets, as the mean CC value increased from 0.38 to 0.47 and the mean RMSE decreased from 15.0 to 13.5 mm/day. In addition, we found that the zero value replacement in MTC had great influence on error estimation, while had limited impacts on data fusion.
... Over the last several decades, lakes in China have faced worrisome aquatic problems, and the water quality on the North China Plain is the worst (Zhou et al., 2017). As the largest shallow lake in the North China Plain, Baiyangdian Lake (BYDL) is facing serious environmental problems (Zhang et al., 2021). ...
Article
The food web structure (FWS) and ecosystem functioning (EF) of lakes worldwide are impacted by multiple disturbances. The historical evolution of the FWS and EF are not well understood due to the lack of sufficient long-term records of biotic variations. This study reconstructed the food web models in the 1950s, 1980s, 1990s, 2000s, and 2010s for Baiyangdian Lake (BYDL), the largest shallow lake in northern China, using the Linear Inverse Modeling (LIM) and investigated EF in different periods. Our results confirmed that the FWS and EF of BYDL have undergone significant changes. The biomass of phytoplankton continuously increased, and the primary productivity of phytoplankton began to replace the primary productivity of submerged macrophytes in the 2000s and became the largest energy flow in the food web. Changes in the energy flow of primary producers are transmitted to high-trophic functional groups, which affects the diet composition of fish. Based on the ecological network analysis indices and food web stability indicators, it was concluded that after a turning point in the 1990s, the ecosystem showed initial stability and then gradually became unstable. Water level fluctuations and nutrient enrichment may be the key driving factors for changes in ecosystem state. Therefore, to maintain a good state of the ecosystem, we recommend implementing comprehensive management measures of hydrological management, nutrient-loading reduction, and biomanipulation. Furthermore, this study extended LIM to lake ecosystems, which may provide a new method for lake ecological environment management.
... Most studies that investigated β-diversity of benthic algae, specifically focused on diatoms, emphasized taxonomic composition; comparisons between taxonomically and trait-based β-diversity relative to multiple environmental stressors at a catchment scale are still limited (Branco et al., 2020;Jamoneau et al., 2018;Perez Rocha et al., 2019). Among the few existent studies, most were carried out in Europe (e.g., France, Finland and Norway; Jamoneau et al., 2018;Perez Rocha et al., 2019) and South America (e.g., Brazil; Branco et al., 2020), whereas no study, to our best knowledge, has focused on Asian countries, such as China, where rapid environmental changes (e.g., urbanization and K E Y W O R D S convergence, diatom, Hun-Tai River, nestedness, periphyton, taxonomy, trait, turnover, βdiversity partitioning dam construction) have occurred in freshwater ecosystems during the last few decades (Zhou et al., 2017). ...
Article
Aim Understanding the variation in biodiversity and its underlying drivers and mechanisms is a core task in biogeography and ecology. We examined (a) the relative contributions of species replacement (i.e., turnover) and richness difference (i.e., nestedness) to taxonomically and trait-based β-diversity of stream benthic algae; (b) whether these two facets of β-diversity are correlated with each other; and (c) the relative contributions of local environmental, geo-climatic and spatial factors to the two facets of β-diversity and their components. Location Hun-Tai River Basin, northeastern China. Taxon Stream benthic algae. Methods A total of 157 sites were sampled. Mantel tests were used to examine the complementarities between the two facets of β-diversity and their components. Distance-based redundancy analysis and variation partitioning were utilized to investigate the relative contributions of local environmental, geo-climatic and spatial factors to each facet of β-diversity and their components. Results Weak correlations between taxonomically and trait-based β-diversity and their components were detected, which indicated complementarity of ecological information. Taxonomically based total β-diversity was largely driven by turnover, whereas trait-based total β-diversity was more driven by nestedness. Variation partitioning results indicated that local environmental and spatial factors contributed more than geo-climatic variables to the total explained variation in taxonomically and trait-based β-diversity. Main conclusions Different facets of β-diversity and their decomposition are important for understanding diversity patterns of benthic algae relative to abiotic factors. A high level of trait-based convergence among benthic algae communities, despite high taxonomic divergence, demonstrated turnover of species with similar biological traits across our study region. Our study provides a trait-based insight into stream benthic algae communities, which was less documented by previous freshwater studies that focused on regions undergoing recovery following human disturbances.
... Compared to highly vegetated watersheds, an increase in agriculture land use fraction would dramatically increase runoff, sediment and more prone to result in water quality deterioration (Allan et al., 1997;Park and Lee, 2020). Environmental invest on water quality in China has paid off during the past decade (Ongley et al., 2010;Shen et al., 2012;Zhou et al., 2017). However, nonpoint source pollution is still the dominant factor resulting in water quality degradation in agricultural plain basins (Guo et al., 2004;Zhang and Huang, 2011;Shen et al., 2012). ...
Article
Water crisis across the globe has placed high pressure on social development due to the need to balance the water consumption between sustainable economy and functioning ecosystem. Integrated process-based modeling has been reported as an effective tool to better understand the complex mechanisms of water issues on a basin scale. Considering that it is still relatively difficult to simulate the water quantity-quality processes simultaneously, this study proposed an integrated modelling framework by coupling a hydrological model with a water quality model. Taking the Xiaoqing River Basin in the Shandong Province of northern China as an example, this study coupled a distributed hydrological model, SWAT, with a one-dimensional hydrodynamic-water quality model, HEC-RAS, to investigate its ability to simulate water quality and quality at the basin scale. The coupling of the two models adopted the “output-input” scheme, where the runoff modeling results from SWAT are input into HEC-RAS for hydrodynamic and water quality simulations of the river channel. The results show that the SWAT model can adequately reproduce runoff with accepted accuracy for the calibration and validation periods with acceptable R² and Nash-Sutcliffe coefficients for the two hydrological stations. Further analysis also shows that the coupled model can simulate the concentration of ammonia nitrogen (NH4-N) and the chemical oxygen demand (COD) in the middle and upper stream of the river for both low and high flow periods. The coupling of the hydrological and hydraulic models in this study provides a good tool for identifying the spatial patterns of the water pollutants over the basin and, thus, helps simplify precision water management.
... Valle Junior et al., (2015) used distance-based linear models to assess areas of conflict in the watershed. In contrast, Zhou et al., (2017) analyzed the impact on water quality of investments, made by the Chinese government, for environmental remediation after decades of natural resource use. ...
Conference Paper
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The organic matter (OM) is an essential part for the maintenance of the aquatic life. However, effluent discharges into water bodies have a significant negative impact on the environment through anthropogenic OM. In this context, land use and occupation plays an important role on water quality management. Several studies focused on the relationship between land use, its occupation and the respective water quality through conventional parameters such as nitrogen, phosphorous, turbidity, solids, BOD and COD. However, only a few studies consider the OM composition through spectroscopic analysis, which could facilitate field monitoring activities and be helpful for more efficient strategies in water resources planning and management.
... It originates from the Qinghai-Tibetan Plateau and flows 6300 km eastward before entering the East China Sea and encompasses a watershed of 1.80 × 10 6 km 2 . During the past four decades, the economic development in the Yangtze watershed, especially in the middle and lower reaches, has led to rapid conversion of forests into agricultural and urban land (Zhou et al. 2017a). Seventeen years have passed since the initial commissioning in 2003 of the Three Gorges Dam whose impoundment significantly altered the river's hydrology and geomorphology, and it is therefore relevant to consider how the carbon dynamics differ above and below this dam. ...
Article
Large rivers are the main arteries for transportation of carbon to the ocean; yet, how hydrology and anthro-pogenic disturbances may change the composition and export of dissolved organic matter along large river continuums is largely unknown. The Yangtze River has a watershed area of 1.80 × 10 6 km 2. It originates from the Qinghai-Tibet Plateau and flows 6300 km eastward through the center of China. We collected samples (n = 271) along the river continuum and analyzed weekly samples at the most downstream situated gauging station in 2017-2018 and gathered long-term (2006-2018) water quality data. We found higher gross domestic product, population density, and urban and agricultural land use downstream than upstream of the Three Gorges Dam, coinciding with higher dissolved organic carbon (DOC), UV absorption (a 254), specific ultraviolet absorbance (SUVA 254), parallel factor analysis-derived C1-C5, aliphatic compounds, and lower a 250 :a 365 and spectral slope (S 275-295). Chemical oxygen demand, humic-like C1-C2 and C6, and protein-like C4 and C7 increased, while dissolved oxygen and ammonium decreased with increasing discharge at most of the sites studied, including the intensively monitored downstream site. The annual DOC fluxes were ca. 1.5-1.8 Tg yr −1 , and 12-18% was biodegradable in a 28-d bio-incubation. Our results highlight that urbanization and stormwater periods enhanced the export of both terrestrial organic-rich substances and household effluents from nearshore residential areas. Our study emphasizes the continued need to protect the Yangtze River watershed as increased organic carbon loading or altered composition and bio-lability may change the ecosystem function and carbon cycling.
... When discussing the spatial characteristics of NH 4 + -N pollution in the watershed, the influence of socio-economic factors on water quality should also be considered along with the influence of land use type (Yang et al. 2019;Zhou et al. 2017). Resource depletion and pollutant discharge that result from socio-economic factors will inevitably lead to environmental degradation (Xiao et al. 2011). ...
Article
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Rapid socio-economic development has led to a significant deterioration in the water environment, which has limited sustainable regional development. The soil and water assessment tool (SWAT) and statistical regression method were used to model the ammonia nitrogen (NH4⁺-N) pollution and explore the impacts of land use and socio-economic factors on NH4⁺-N pollution within the Weihe River watershed in China from 2015 to 2018. The result of SWAT model revealed that the NH4⁺-N concentrations were usually relatively high under low runoff conditions and relatively low under high runoff conditions. The average NH4⁺-N concentration in the upper reaches was 0.77 mg/L, whereas it was 0.87 mg/L in the middle and lower reaches of the watershed. Serious NH4⁺-N pollution mainly occurred in 2015 and 2016, and the V (2.0 mg/L) and V+ (>2.0 mg/L) water quality classes were associated with approximately 6.67% and 28.94% of the total watershed area, respectively. The multiple linear regression indicated that the building land and secondary industry were the significant controlling factors (P < 0.01). According to the scenario analysis, modelled scenarios for interception measures reduced the NH4⁺-N load to a greater degree than scenarios for source control measures. To improve the surface water quality in the Weihe River, it is recommended to adjust industrial structure, increase sewage treatment, and strengthen the rural management of the watershed.
... Previous researches did not combine three different water quality indices and also did not estimate and forecast future water quality. In addition previous researches, such as (Clasen et al., 2015 andZhou et al., 2017), did not consider and did not analyze future water quality for different seasons. However, this paper applied three different water quality indices and estimated future characteristics of water quality (based on water quality indices) under climate change and scenarios (based on CMIP5 climate model and RCP scenario).Also, this study assessed future water quality for various seasons. ...
Article
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Background: Providing fresh water suitable for drinking and farming and living organisms in the ecosystem is essential. To evaluate water quality, qualitative indicators are often employed for managing water resources and water quality protection and pollution abatement. Aim: This study evaluated the quality of Borkhar basin water resources using three different water quality indices, including National Institutes of Health Water Quality Index (NIHWQI) having nine parameters, the Oregon Water Quality Index (OWQI) having eight parameters, and the Canadian Water Quality Indices (CWQI) with 22 main parameters. Material and methods: Using data for a period of 30 years, NIHWQI, OWQI and CWQI were used. To analyze water quality of the entire basin for current and future time. New findings: Results showed that water quality of the basin was in a very moderate range according to NSFWQI, and was in a very bad range accordingly to OWQI. Water quality forecasts showed that future water quality would be bad, based on OWQI and moderate based on NSFWQI, whereas based on CWQI, it will be good for drinking, and bad for aquatic animals, recreation, irrigation, and livestock use.
Article
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Freshwater lakes across the world have undergone dramatic changes in biological components and water quality over the past several decades. Previous studies focused on potential drivers mainly on nutrient enrichment in the catchment. However, the relative importance of climate change and the top-down cascade effects of fish stocking on water quality is not fully understood. Here, by compiling 155 lakes data with four periods of field investigation in subtropical lakes in China, we found no significant changes in water total nitrogen and total phosphorus in the past two decades. However, the phytoplankton abundance increased significantly, and the water clarity declined by 44.1%. We further found that carp stocking and climate change are potentially more important than nutrients driving water quality change, which is also evidenced in two lakes (Lake Donghu and Qiandao) with long-term monitoring histories. Specifically, carp stocking can decrease the water clarity directly by stirring up sediment and indirectly by trophic cascade along the food web. For climatic factors, mean annual temperature (MAT) has a positive effect on phytoplankton abundance, while mean annual precipitation has a negative one, with climates overall having little effect on water clarity. In addition, nutrient enrichment and climate change also have strong interactions with carp stocking, which may enhance the top-down effects on water quality. Our findings highlight that either MAT or carp stocking may become an overwhelming driver of water clarity decline, which provides new insights into the conservation strategy for water quality management in the subtropical lakes in China.
Article
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Water clarity (Secchi disk depth, SDD) provides a sensitive tool to examine the spatial pattern and historical trend in lakes’ trophic status. However, this metric has been insufficiently explored despite the availability of remotely-sensed data. Based on the published SDD datasets derived from Landsat images, we analyzed the spatial and inter-annual variations in water clarity and examined the impact of natural and anthropogenic factors on these trends at multiple scales, i.e., five lake regions, provinces, and watersheds. Lake clarity was lowest in Northeast (0.60 ± 0.09 m) and East China (1.23 ± 0.17 m) and highest in the Tibet Plateau (3.32 ± 0.38 m). Over the past 35 years, we found a significant trend of increased SDD in 18 (out of 32) provinces (only Yunnan province exhibited a significant decreasing trend) and in 77 (out of 155) watersheds (only 5 watersheds showed a significant decreasing trend). Lakes in eastern-northeastern China exhibited a higher probability of decreasing trend, while the trend was inverse for lakes in the Tibet-Qinghai region. The results of water clarity interannual change trends showed they were closely related to the spatial scale of analysis. At the watershed level, these trends were mainly driven by anthropogenic factors, with night-time brightness (13.84%), agricultural fertilizer use (11.17%), and wastewater (9.64%) being the most important. Natural factors (temperature, wind, and NDVI) explained about 18.2% of the SDD variance. Our findings for the SDD spatio-temporal trend provide valuable information for guiding water protection management policy-making and reinforcement in China.
Article
Seasonal variations in surface water quality are essential for assessing temporal variations in wetlands pollution due to natural or anthropogenic inputs from both point and non-point sources. The goal of this study was to use established methodologies to estimate the water quality of the Tianfu National Wetland Park based on physicochemical features; sampling was done from eight monitoring locations throughout the wetland region in the summer of 2019 and winter of 2020. The water quality index (WQI) is calculated using the following parameters: Turbidity (NTU), Nitrate, Chlorophyll, TOC, DOC, COD, BOD, Chroma, Ammonium nitrogen, pH, Electric Conductivity, and Total Phosphorus. One-way ANOVA and Tukey’s pairwise comparisons with a 5% significance level were used to compare water quality parameters among the monitoring point’s data. T-test analysis was used to compare the parameters between summer 2019 and winter 2020 and the difference between the water inlet and the water outlet. Cluster analysis was done on the WQI results using Ward’s linkage approach. The analyses of variance (ANOVA) of data revealed statistically significant differences between points of sampling (p < 0.05). The paired t-test revealed significant differences in parameters between summer 2019 and winter 2020; however, all parameters in summer show higher values in the water inlet than water outlet. In winter, TOC, DOC, COD, BOD, Chroma, pH, and Electric Conductivity showed higher values than Turbidity (NTU), Nitrate, Chlorophyll, Ammonium Nitrogen, and Total Pospurus. In general, summer showed higher pollution than winter, and water inlets were more polluted than water outlets indicating that other factors may affect the water quality, such as vegetation cover, temperature, water level, and activities in the wetland during the seasons.
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Gaining a deeper understanding of factors that influence changes in phytoplankton community has significant implications for shallow lake management. The present study examined changes in the algae community of three shallow eutrophic lakes of the Taoge water system between 2008 and 2018 and the related factors influencing these changes. The composition of the algal community varied significantly during this period with the relative diatom biomass in lakes Changdanghu and Gehu increasing between 2014 and 2016 and again decreasing after 2017. However, relative cyanobacteria biomass initially decreased and later increased; meanwhile, the proportion of biomass of other phyla decreased continuously in the study period. Lake Zhushanhu showed similar trends, although it eventually returned to its initial state with absolute Microcystis dominance. Furthermore, the analysis of driving factors revealed that the concentrations of total nitrogen (TN), nitrate (NO3), and orthophosphate (PO4) were significantly associated with a significant increase in Microcystis biomass. Meteorological conditions also influenced changes in total algal and diatom biomasses, which were inversely related to the daily mean and daily maximum wind speeds. Monthly cumulative precipitation was only significantly associated with diatom biomass. Meanwhile, rainfall primarily affected the algal community structure between 2013 and 2017; an increase in the relative biomass of diatoms coincided with increased precipitation. Coordinating nitrogen and phosphorous use within the Taoge water system should improve lake habitat management; a broader perspective in attempts to control global and regional climate change may be needed.
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Chinese lakes have been affected by climate change, agricultural intensification and population increases since 1850. However, the spatiotemporal variations in nitrogen and phosphorus in lake sediments and the factors influencing these variations are poorly understood. This research analysed the spatiotemporal variations in the mass accumulation rate (MAR) and total nitrogen (TN) and total phosphorus (TP) concentrations of sediments since 1850 and the responses of these factors to the influence of natural and anthropic factors through the collection of data from 56 lake sediment samples in China. After 2000, the average MAR value (2794 g/m²/yr), TN concentration (0.35%) and TP concentration (0.96‰) of lake sediments were significantly higher than the average values during 1850–1900 (p < 0.05). During the study period, the MAR of the lake sediments in the eastern plain (EP) was the highest in the country, and the increase was also largest in this region. The TN concentrations of lake sediments in the Northeast Plain (NEP) were the highest in the country, and the TN concentrations of lakes in the Yunnan-Guizhou Plateau (YGP) underwent the largest increase. The TP concentrations in the sediments of the YGP were higher than the national average during the study period, and the lakes in the NEP had the highest increase in TP concentrations. The result showed climate and lake morphology are important factors controlling the indices in lakes' sediment in Qinghai-Tibet Plateau (QTP) since 1900. Climate and lake morphology are major impact factors for lakes’ sediment indices in NEP, EP, Mongolia- Xinjiang Plateau (MXP) and YGP in 1900–1950. After 1950, anthropic factors gradually replaced natural factors and became the main factors affecting these four regions and anthropic factors promoted the increase of nutrient concentration in lake sediments. The results of this study show that sustainable agricultural development policies and population policies can help control the quality of nutrients entering lakes, thereby reducing the concentrations of nutrients in lake sediments in the future.
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Pollution in inflow rivers seriously endangers the water environment in downstream lakes. In this study, an inflow river system of the Baiyangdian–Fuhe river system (FRS) was investigated to display timely pollution patterns of eutrophication and heavy metals after the establishment of Xiongan New Area, aiming to reveal the weak parts in current pollution treatments and guide the further water quality management. The results showed that the pollution of eutrophication was worse than the heavy metals in FRS, with serious eutrophic parameters of ammonia nitrogen (NH 4 ⁺ -N) and chemical oxygen demand (COD). There were greatly spatiotemporal variations of the pollution in FRS. (1) Concentrations of NH 4 ⁺ -N and total phosphorus were all higher in summer and autumn, whereas, COD contents were higher in spring; the water quality index ( WQI ) of eutrophication linearly increased along FRS in summer and autumn, with pollution hotspots around the estuary area. (2) The pollution levels of plumbum exceeded cadmium (Cd) and chromium (Cr) but without strongly spatiotemporal changes; however, Cd and Cr in the town area and Cd in spring showed higher concentrations; the WQI of heavy metals showed single peak curves along FRS, with significantly higher values around the town area. Additionally, the four potential pollution sources: domestic sewage, traffic pollution, agricultural wastewater and polluted sediments were identified based on the pollution patterns and pollutant associations. These findings demonstrated current treatments failed to eliminate the pollution in some hotspots and periods, and the in-depth understanding of the pollution spatiotemporal patterns in this study, especially the pollution hotspots, serious periods and potential sources, are crucial to furtherly develop spatiotemporally flexible pollution treatment strategies.
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Understanding of how changes in diverse human activities and climate contribute to water quality dynamics is crucial for sustainable water environment management especially in the arid and semi-arid regions. This study conducted a comprehensive estimation of the surface water quality change in the Yellow River basin during 2003–2017 and its responses to varied pollution sources and water volumes under socioeconomic and environmental influences. Basin-wide measurements of chemical oxygen demand (COD), ammonium nitrogen (NH+ 4-N) and dissolved oxygen (DO) concentrations were used in trend detection. Annual anthropogenic (covering six sectors) and natural (sediment-induced, flow-in from the upstream and stored last year) pollution sources and water components (inflow, natural runoff, water consumption, reservoir storage and evaporation) were compiled for each sub-basin. Bottom-up hierarchical analysis was then performed to differentiate individual contributions. Results showed significant decreasing trends in COD and NH+ 4-N concentrations and increasing trends in DO concentrations. The middle reaches that traverse the Loess Plateau however remained severely polluted with 11.3–39.0% inferior to level III in 2017. The pollutant load played major positive contributions that gradually increased from upper to lower reaches. Declines in urban, rural and industrial pollution discharges following environmental investments and rural depopulation contributed the most: 78–96% for COD and 55–100% for NH+ 4-N. The total surface water volume had dilution effects in the upper and middle reaches (3–28%) and condensing effects in the lower reaches (2–37%). Precipitation and vegetation dynamics contributed slightly. The primary unfavorable factors were the growing agricultural pollution discharges and water consumption in the upper and middle reaches that also threatened the lower reaches. This study is expected to provide in-depth insights for the systematic response of regional water quality to combined human interventions and references for water quality management in other arid and semi-arid river basins worldwide.
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Meeting the ever-growing demands of humans while ensuring sustainability is one of the great challenges of this century. China has made significant economic progress in recent decades and is increasingly engaged in international activities. This economic prosperity, however, has resulted in substantial contaminant discharge and damage to domestic aquatic ecosystems. Considerable efforts have been made to address these issues through developments in wastewater services infrastructure. Here, we provide an overview of wastewater infrastructure development in the Yangtze River Economic Zone during 2007–2017 and analyze diverse long-term monitoring data. These analyses trace and capture the key drivers affecting the restoration of water quality and determine how such restoration may be sustained or even accelerated in future. We find that there has been a decoupling trend between the economy and environmental variables since 2013, which coincides with the substantial implementation of improved wastewater treatment systems. While further developments in sewerage facilities and phosphorus discharge reduction may continue restoration, a paradigm shift toward a circular economy remains necessary to integrate these developments with wastewater resources management. Overall, this study advances the current understanding of the impact of wastewater services facilities on the balance between economic development and environmental protection.
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Purpose This paper examines pre- and post-production water treatment practices among food processors and investigates factors, especially managerial perceptions of environmental pressure that encourage or preclude either process. Design/methodology/approach To consider potential spillover effects across two water-treatment practices, the bivariate probit model based on random utility theory is used to investigate how practices are influenced by managerial perceptions of environmental pressure and measured by manager perceptions on water costs, water availability, water safety and quality. Findings Results indicate that firms with a managerial perception that water costs are low are less likely to conduct both pre- and post-production water treatment practices, while the perception of high water quality has a negative effect on water treatment prior to use. This study also confirms the positive correlation of the pre- and post-water treatment practices among food processors. Practices also change with firm features including production scope, scale, target market and expected future sales growth. Practical implications This study provides unique insights about water treatment practices and generates knowledge to enhance food safety and environmental sanitation in the food industry. Results are helpful to design and provide additional training and educational programs that target the enhancement of environmental and water quality awareness among food company managers and modify food safety policy instruments and environmental regulations pertaining to surface water resources. Originality/value Research exploring water-treatment practices in the food industry has been limited. Using a representative sample of food processors in the city of Shanghai, this study contributes to the literature on the examination of internal drivers of voluntary environmental management (VEM) with a focus on managerial perceptions of environmental pressure, establishes the correlation between pre- and post-production water treatment practices and identifies and quantifies the effects of relevant factors.
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China's current water quality standards (WQS) were first established in the 1980s referring the other countries' experience in setting environmental criteria and may not be suitable for the circumstances in China. Thus, it is necessary to improve the theories and methodologies of WQS. This paper provided a promising method to determine water quality categories based on biotic index of macroinvertebrates. Firstly, systematic ecological investigations were conducted and the biotic index of macroinvertebrates were used to assess the river health. Then, the statistical analyses and the driving effects of water quality factors on biological communities were identified. Futhermore, the relationship between cumulative mean of biotic index of macroinvertebrates and its derived factor was established. Finally, ecological thresholds for water quality base on biotic index of macroinvertebrates were obtained. The novel method was carried out in the Yangzhou city of the Yangtze River Delta, China. The biological samples were comprised of total 59 invertebrate taxa from 30 sites in Yangzhou city. Biotic index assessment shown that 16.7% of the sites were very healthy in summer and 8.3% of the sites were very healthy in winter. The most important hydrological factor affecting macroinvertebrate species was NH4-N in summer and CODMn in winter. Finally, the benchmark of NH4-N and CODMn deriving from macroinvertebrates tolerance values was obtained. This work can provide important information for pollution management in ambient aquatic ecosystem for decision makers.
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Due to the vertical migration of cyanobacteria and frequent wind waves disturbance, the floating, mixing, migration and accumulation of cyanobacteria bloom in Lake Taihu occur rapidly. It is very difficult to accurately capture cyanobacteria bloom occurrence and appearance using the traditional lake positioning and cross-section monitoring due to low temporal and spatial observation frequency and resolution, which limits the in-depth understanding of cyanobacteria bloom formation process, driving mechanism, prevention and control. Satellite remote sensing can realize the synchronous observation of the spatial distribution of cyanobacteria bloom, but it is difficult to capture the rapid dynamics of cyanobacteria bloom due to the limitation of observation frequency. Using independently developed land-based (ground-based, shore-based, or fixed on the platform, ship and pile foundation) hyperspectral water quality remote sensing instrument by the Hangzhou Hikvision Digital Technology Co., Ltd and Nanjing Zhongke Deep Insight Technology Research Institute Co., Ltd installed in Taihu Laboratory for Lake Ecosystem Research (TLLER) of Chinese Academy of Sciences, the short-term sudden and rapid cyanobacteria bloom dynamics in a day was effectively captured through the continuous observation of chlorophyll-a concentration and other key water quality parameters at the second-minute level. The results show that cyanobacteria are easy to float in the surface water under the conditions of breeze and light wind, and the prevailing northwest wind drives the cyanobacteria bloom in the open water area of the lake to float and accumulate to the shore of TLLER quickly. Chlorophyll-a concentration in surface water can rapidly rise from 10 μg/L to more than 100 μg/L in just half an hour. Several chlorophyll-a peaks are recorded in a day from 8:30 to 18:30. All these results clearly show that cyanobacteria have a rapid hourly dynamic change process. Affected by the rapid hourly variations of cyanobacteria, water quality parameters such as secchi disc depth, total nitrogen, total phosphorus and chemical oxygen demand also show rapid hourly variations. Significantly negative relationship between chlorophyll-a and secchi disc depth but significantly positive relationships between chlorophyll-a and total nitrogen, total phosphorus, chemical oxygen demand are found, which indicate short-term floating and gathering of cyanobacteria have a profound impact on the water quality of lakes.
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Algal blooms, the rapid proliferation of algal biomass often to nuisance or harmful levels, diminish aquatic ecosystem services. Freshwater blooms can cause substantial economic damage by interrupting water supply, limiting recreation, and reducing property values. The interaction between eutrophication and climate change has been hypothesized to drive widespread intensification of blooms in inland waters, although there is little empirical evidence that this trend is pervasive. Here, we show that bloom intensification in inland waterbodies – defined as trends in chlorophyll‐a of increasing bloom magnitude, severity, or duration – has not been widespread for hundreds of lakes in the US. Only 10.8% of the 323 waterbodies analyzed had significant bloom intensification. Conversely, 16.4% of the waterbodies had significant decreasing trends during the same period. While it is encouraging that bloom intensification is not currently widespread, continued efforts toward aquatic ecosystem protection and restoration are imperative for maintaining ecosystem services into the future.
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Water level fluctuation and modification in human activities induced by dam construction have significantly affected the production and input of nutrients in the tributary watersheds. In this study, numerical simulation and time series analysis methods are used to explore the input of phosphorus (P) in different types of tributary watersheds around the reservoirs in river reservoir systems and the impact of dam construction on reservoir water quality. Watersheds within a reservoir were divided into larger and smaller tributary watersheds according to whether their area was greater than or less than 1000 km². The results showed that smaller tributary watersheds, which account for 29% of the area of the Three Gorges Reservoir Region (TGRR), transported approximately 36%∼45% of P and 43.7%∼47.8% of sediment deposited into the mainstream from 2003 to 2017. P from the smaller tributary watersheds of the reservoir had a stronger influence on the aquatic environment of the river-reservoir system than that from the larger tributary watersheds. In addition, the annual mean contributions of the P inputs from the “three rivers” (the Yangtze River, the Jialingjiang River and the Wujiang River) and tributary watersheds within the reservoir were 68.76% and 31.18% from 2003 to 2017, respectively. The dam altered the composition of the form of P in the river-reservoir system, and the waterbody close to the dam was identified as the main area containing dissolved P (DP) enrichment. Accordingly, the risk of eutrophication remains high in head area of the dam due to the relatively high and stable P concentration. This study provides critical information for the management of nutrients in a river-reservoir system and the prevention of eutrophication of water bodies.
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Water clarity, denoted by the Secchi disk depth (SDD), is one of the most important indicators for monitoring water quality. In the Songhua River basin (SHRB), few studies have used Landsat to monitor long-term (3–4 decades) changes in lake SDD and explore the impact of natural and human factors on SDD interannual variation at the watershed scale. Lakes in the SHRB are of great significance to local populations. Understanding the spatiotemporal dynamics of SDD could help policymakers manage, protect, and predict lake water quality. We utilized the Landsat red/blue band ratio in the Google Earth Engine to estimate the SDD of 77 lakes and generated annual mean SDD maps from 1990 to 2018. The results of the SDD interannual changes showed that the water quality in the SHRB has improved since 2005. Specifically, the SDD in the SHRB displayed a significant increasing trend (p<0.05) from 0.29 m in 2005 to 0.37 m in 2018. Moreover, the number of lakes displaying a significant increasing trend for SDD increased from 18 between 1990-2005 to 31 between 2005-2018. We also found that use of chemical fertilizer significantly impacted lakes, followed by wastewater discharge and normalized difference vegetation index. Improvements in the quantity and ability of wastewater discharge treatment and increased vegetation cover have alleviated water pollution; however, the non-point pollution of agriculture still poses a threat to some lakes in the SHRB. Therefore, more efforts should be made to further improve the aquatic ecological environment of SHRBs.
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As different algae growths responding to a set of nutrients can occur under different conditions, the nutrient load management based on the relationship between chlorophyll a (Chla) and total phosphorus (TP) alone may not always effective for lake algae bloom control. It is not clear whether the lagged response of algae to reduced nutrients related to the utilization efficiency of algae to phosphorus (UEAP), and how UEAP could response to climate and water quality factors. Here we analyzed over 20 years monitoring data in two lakes with similar geology but different nutrient levels by using statistical and modeling methods. The aim was to reveal the impact of UEAP on lake algae dynamics and the driving factors of UEAP changes. The results showed that UEAP is one of the key factors affecting algae dynamics, the incorporation UEAP and its driving factors achieved greater modeling reliability. UEAP, Nitrogen phosphorus ratio (NPr) was the key driving factor in Dianchi Lake, while total nitrogen (TN) and air temperature (AT) were the key driving factors in Erhai Lake. The changes of nutrients and climate drove UEAP into the paralysis or sensitive phase depending on lake specific factors and conditions. This correlated to algae density dynamics, in particular to those characteristic of algae growth thresholds. The future trend of climate change will continue to promote the increase of UEAP in both lakes, but severer in Erhai Lake. The key finding here is of the value of a proxy index (UEAP) for phosphorus utilization was associated with the lagged response of algae to nutrient reduction. We demonstrated the related modeling procedures with two-function variable (UEAP) of both prediction and response can predict the trend of algae growth and determine the states of the lake ecosystem. Hence, the approaches are of great value for lake management policy making.
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The removal of nitrogen compounds from a pretreated explosives wastewater in vertical flow constructed wetland planted with Vetiveria zizanioides (0.24 m²× 0.70 m), filled with light expanded clay aggregates (Leca®NR 10/20), was studied. Experiments under constant hydraulic load, 50±4 L m⁻² d⁻¹ and 83±5 L m⁻² d⁻¹ without and with flooding level (25%), respectively, were made at different ammonium (3 to 48 mg NH4⁺-N L⁻¹), nitrate (56 to 160 mg NO3⁻-N L⁻¹) and nitrite (0.3 to 1.1 mg NO2⁻-N L⁻¹) concentrations. Results indicate that without flooding level (unsaturated) the removal efficiencies obtained were 30±9, 7±1 and 96±2%, respectively to NH4⁺-N, NO3⁻-N and NO2⁻-N. When using flooding level and an external carbon source (C/N ratio from 1.3±0.19 to 2.5±0.20), the organic matter (COD) removal efficiencies were above 90%, 75% for NH4⁺-N and 55% to NO3⁻-N. Increasing the C/N ratio from 2.9±0.21 to 4±0.22 did not contributed to upgrade the efficiencies of COD, NH4⁺-N and NO3⁻-N removal. The denitrification process was occurred in aerobic conditions and nitrite production have ben occurred, probably due to the presence of aerobic conditions that inhibited partially denitrification.
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The transport and deposition of phosphorus (P) in large-scale basin are closely associated with the spatial distribution characteristics and nutritional status of river sediments. Samples of surface water (SW), suspended sediment (SS), bed sediment (BS), and sediment cores from the Yellow River (YR) were collected. The different fractions including total phosphorus (TP), organic P (OP), inorganic P (IP), HCl–P and NaOH–P were determined by standard measurement and testing method. The results showed that upper, middle, and downstream sedimentary texture exhibit spatial heterogeneity. Pearson correlation analysis and redundancy analysis revealed that medium grain size (Mz) is the most negative factor that influence P and fractions, indicating the importance of silt content. Additionally, TP and HCl-P content were positively and significantly correlated, and the calculated correlation coefficient was 0.96 (p < 0.05). Fe oxides had the greatest positive effect on the absorption of NaOH–P in sediments, followed by Al and Mn oxides. From the sediment cores perspective, the rose figure and logistic regression curve showed that significant growth trend, which indicates that vertical pollution status becomes more severe with increasing silt content. Overall, due to the strong adsorption ability of finer particle as silt that driving the P distribution, this study suggests a greater focus on the effects of fine sediment particles transport for the diffuse pollution control towards the whole basin.
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A challenge for current surface water restoration and management in China is acquiring the source information for complex pollution scenarios in order to develop effective control strategies. As an important part of dissolved organic matter, chromophoric dissolved organic matter (CDOM) contains unique chemical signals related to various pollution sources. Spectral methods such as fluorescence excitation-emission matrices coupled with parallel factor analysis enable rapid and low-cost CDOM characterization for source tracking. In this study, a typical small-sized river flowing through mixed land-use regions in southeastern China, the Lujiang River, was investigated to determine the responses of CDOM to spatiotemporal factors. The effects of land-use patterns were reflected by the fluorescent components of terrestrial and sewage substances. A high and stable proportion of terrestrial-like components (C1 + C2) in each sampling period (i.e., March: 47.6 ± 5.7% and October: 44.3 ± 2.7%) indicated a high input of non-point source (NPS) pollution from both agriculture and urban areas. In addition, the difference in solar radiation intensity induced by climate and air quality changes was also reflected by variability in the photodegradation product component (C3) of terrestrial precursors between October (24.8 ± 2.6%) and March (4.5 ± 2.0%), suggesting that terrestrial components could be a sensitive indicator for NPS pollutant monitoring. Increased sewage impact in downstream regions was reflected by a spike in the tryptophan-like component (C4); temporal variations in C4 (paired t-Test, p < 0.005) also indicated that sewage substances were more prone to removal by microbial activity in warmer seasons. The dynamics of C4 could serve as a good indicator of sewage disposal performance. The results of this study demonstrate that CDOM data have important practical applications for existing water restoration campaigns in southeastern China, as well as substantial potential for routine water quality monitoring.
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In China, most rural areas lack specific sewage discharge standards. Even though China governments proposed a series of local standards, the most of the existing China's rural sewage discharge standards are still similar to urban discharge standards. This research analyses comprehensively the data of rural sewage discharge standards in the 31 provinces and cities in China in terms of grade and indicator, and forms a structural framework for the formulation and revised standards in rural areas of China. In the formulation, we use 2 components, end-use and environmental capacity, to reflect local characteristics of the grades and indicators, and also propose the methods of combining discharge standards with relevant water quality standards to save energy. And we also use the mathematical model to illustrate environmental capacity in different regions. The paper shows the great potential in guiding the design of discharge standards formulation and revision for rural wastewater treatment in China and other developing countries as well.
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Qinghai-Tibet Plateau (QTP) Lake Region has largest abundance and size distribution of lakes in China. Being relatively away from major human activities, the water quality of these lakes has not attracted concerns in the past. However, dramatic climate change and intensified anthropogenic activities over the past 30 years have exerted multiple pressures on the water environment of the lakes, resulting in elevated nutrient concentrations in major freshwater lakes of the region. Rapid water quality deterioration and eutrophication of the lakes were first found in Lake Hurleg in the northeast of the plateau. Analyses of driving forces associated with these changes indicate that both the intrinsic characteristics of the QTP lakes and climate change were responsible for the vulnerability to human activities than other lakes in different regions of China, with accelerated urbanization and extensive economic development in the lake basin playing a decisive role in creating water pollution events. Under combination pressures from both natural and anthropogenic effect, the increasing rate of nutrient concentrations in Lake Hurleg has been 53–346 times faster than in Lake Taihu and Lake Dianchi during the deterioration stage. The result suggests the current development mode of Lake Hurleg basin is not suitable for setting protection targets for the QTP lake region more broadly due to its extremely poor environmental carrying capacity. To stop worsening the lake water environment condition, it is necessary to review the achievements made and lessons learned from China’s fight against lake pollution and take immediate measures, inform policies into the development mode in the QTP lake region, and avoid irreversible consequences and ensure good water quality in the "Asian Water Tower."
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The erosion, transport and redeposition of sediments shape the Earth's surface, and affect the structure and function of ecosystems and society. The Yellow River was once the world's largest carrier of fluvial sediment, but its sediment load has decreased by approximately 90% over the past 60 years. The decline in sediment load is due to changes in water discharge and sediment concentration, which are both influenced by regional climate change and human activities. Here we use an attribution approach to analyse 60 years of runoff and sediment load observations from the traverse of the Yellow River over China's Loess Plateau-the source of nearly 90% of its sediment load. We find that landscape engineering, terracing and the construction of check dams and reservoirs were the primary factors driving reduction in sediment load from the 1970s to 1990s, but large-scale vegetation restoration projects have also reduced soil erosion from the 1990s onwards. We suggest that, as the ability of existing dams and reservoirs to trap sediments declines in the future, erosion rates on the Loess Plateau will increasingly control the Yellow River's sediment load.
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The "Grain for Green Project" is a country-wide ecological program to converse marginal cropland to forest, which has been implemented in China since 2002. To quantify influence of this significant vegetation change, Guansihe Hydrological (GSH) Model, a validated physically-based distributed hydrological model, was applied to simulate runoff responses to land use change in the Guansihe watershed that is located in the upper reaches of the Yangtze River basin in Southwestern China with an area of only 21.1 km2. Runoff responses to two single rainfall events, 90 mm and 206 mm respectively, were simulated for 16 scenarios of cropland to forest conversion. The model simulations indicated that the total runoff generated after conversion to forest was strongly dependent on whether the land was initially used for dry croplands without standing water in fields or constructed (or walled) paddy fields. The simulated total runoff generated from the two rainfall events displayed limited variation for the conversion of dry croplands to forest, while it strongly decreased after paddy fields were converted to forest. The effect of paddy terraces on runoff generation was dependent on the rainfall characteristics and antecedent moisture (or saturation) conditions in the fields. The reduction in simulated runoff generated from intense rainfall events suggested that afforestation and terracing might be effective in managing runoff and had the potential to mitigate flooding in southwestern China.
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Fresh waters make a disproportionately large contribution to greenhouse gas (GHG) emissions, with shallow lakes being particular hotspots. Given their global prevalence, how GHG fluxes from shallow lakes are altered by climate change may have profound implications for the global carbon cycle. Empirical evidence for the temperature dependence of the processes controlling GHG production in natural systems is largely based on the correlation between seasonal temperature variation and seasonal change in GHG fluxes. However, ecosystem-level GHG fluxes could be influenced by factors, which whilst varying seasonally with temperature are actually either indirectly related (e.g. primary producer biomass) or largely unrelated to temperature, for instance nutrient loading. Here, we present results from the longest running shallow-lake mesocosm experiment which demonstrate that nutrient concentrations override temperature as a control of both the total and individual GHG flux. Furthermore, testing for temperature treatment effects at low and high nutrient levels separately showed only one, rather weak, positive effect of temperature (CH4 flux at high nutrients). In contrast, at low nutrients, the CO2 efflux was lower in the elevated temperature treatments, with no significant effect on CH4 or N2 O fluxes. Further analysis identified possible indirect effects of temperature treatment. For example, at low nutrient levels increased macrophyte abundance was associated with significantly reduced fluxes of both CH4 and CO2 for both total annual flux and monthly observation data. As macrophyte abundance was positively related to temperature treatment, this suggests the possibility of indirect temperature effects, via macrophyte abundance, on CH4 and CO2 flux. These findings indicate that fluxes of GHGs from shallow lakes may be controlled more by factors indirectly related to temperature, in this case nutrient concentration and the abundance of primary producers. Thus, at ecosystem scale response to climate change may not follow predictions based on the temperature dependence of metabolic processes. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
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Riverine export of particulate organic carbon (POC) to the ocean affects the atmospheric carbon inventory over a broad range of timescales. On geological timescales, the balance between sequestration of POC from the terrestrial biosphere and oxidation of rock-derived (petrogenic) organic carbon sets the magnitude of the atmospheric carbon and oxygen reservoirs. Over shorter timescales, variations in the rate of exchange between carbon reservoirs, such as soils and marine sediments, also modulate atmospheric carbon dioxide levels. The respective fluxes of biospheric and petrogenic organic carbon are poorly constrained, however, and mechanisms controlling POC export have remained elusive, limiting our ability to predict POC fluxes quantitatively as a result of climatic or tectonic changes. Here we estimate biospheric and petrogenic POC fluxes for a suite of river systems representative of the natural variability in catchment properties. We show that export yields of both biospheric and petrogenic POC are positively related to the yield of suspended sediment, revealing that POC export is mostly controlled by physical erosion. Using a global compilation of gauged suspended sediment flux, we derive separate estimates of global biospheric and petrogenic POC fluxes of 157(+74)(-50) and 43(+61)(-25) megatonnes of carbon per year, respectively. We find that biospheric POC export is primarily controlled by the capacity of rivers to mobilize and transport POC, and is largely insensitive to the magnitude of terrestrial primary production. Globally, physical erosion rates affect the rate of biospheric POC burial in marine sediments more strongly than carbon sequestration through silicate weathering. We conclude that burial of biospheric POC in marine sediments becomes the dominant long-term atmospheric carbon dioxide sink under enhanced physical erosion.
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The large shallow eutrophic Lake Taihu in China has long suffered from eutrophication and toxic cyanobacterial blooms. Despite considerable efforts to divert effluents from the watershed, the cyanobacterial blooms still reoccur and persist throughout summer. To mitigate cyanobacterial bloom pollution risk, a large scale integrated monitoring and forecasting system was developed, and a series of emergency response measures were instigated based on early warning. This system has been in place for 2009-2012. With this integrated monitoring system, it was found that the detectable maximum and average cyanobacterial bloom area were similar to that before drinking water crisis, indicating that poor eutrophic status and cyanobacterial bloom had persisted without significant alleviation. It also revealed that cyanobacterial bloom would occur after the intense storm, which may be associated with the increase in buoyance of cyanobacterial colonies. Although the cyanobacterial blooms had persisted during the monitoring period, there had been a reduction in frequency and intensity of the cyanobacterial bloom induced black water agglomerates (a phenomenon of algal bloom death decay to release a large amount black dissolved organic matter), and there have been no further drinking water crises. This monitoring and response strategy can reduce the cyanobacterial bloom pollution risk, but cannot reduce eutrophication and cyanobacterial blooms, problems which will take decades to resolve. Copyright © 2015 Elsevier B.V. All rights reserved.
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Eastern China has experienced substantial agricultural expansion and deforestation in recent decades. We modeled the influence of land use/cover changes (LUCCs) over eastern China on the regional climate using the Weather Research and Forecasting (WRF) model with the Noah-MP land surface scheme. Two 21-year (1980-2000) experiments were performed using the same settings, except for the land use/cover data for the 1980s and 2000s. The results showed that in northern China, decreases in the surface air temperature of approximately 0.3 ~ 0.5 °C and decreases (increases) in rainfall over the lower reaches of the Yangtze River valley (southern China, northeastern China and the Korean Peninsula) of approximately 3 % (6 ~ 7 %) in the summer were associated with LUCCs in eastern China from the 1980s to 2000s. The cooling effect in northern China, which was primarily attributable to an increase in the surface latent heat flux of approximately 7.3 ~ 9.6 W m-2, weakened the land-ocean thermal contrast, suggesting the presence of a weaker summer monsoon over eastern China. As a result, rainfall over the lower reaches of the Yangtze River valley (southern China) tended to decrease (increase). In addition, the cooling effect may have produced an anomalous cyclonic circulation from the surface to the mid-troposphere over northeastern China and the Korean Peninsula, resulting in increased rainfall over this area.
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Despite the small continental coverage of lakes, they are hotspots of carbon cycling, largely due to the processing of terrestrially derived dissolved organic matter (DOM). As DOM is an amalgam of heterogeneous compounds comprising gradients of microbial and physicochemical reactivity, the factors influencing DOM processing at the molecular level and the resulting patterns in DOM composition are not well understood. Here we show, using ultrahigh-resolution mass spectrometry to unambiguously identify 4,032 molecular formulae in 120 lakes across Sweden, that the molecular composition of DOM is shaped by precipitation, water residence time and temperature. Terrestrially derived DOM is selectively lost as residence time increases, with warmer temperatures enhancing the production of nitrogen-containing compounds. Using biodiversity concepts, we show that the molecular diversity of DOM, or chemodiversity, increases with DOM and nutrient concentrations. The observed molecular-level patterns indicate that terrestrially derived DOM will become more prevalent in lakes as climate gets wetter.
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The Changjiang Estuary is a large bifurcated estuary where different hydrodynamic processes influence its South Branch compared to its North Branch. The South Branch is the dominant pathway of Changjiang River discharge, while the shallower and narrower North Branch is dominated by salt water intrusion, especially in the dry season. Absorption and fluorescence spectroscopy were measured along with dissolved organic carbon (DOC) concentrations to characterize the properties of DOM collected in different seasons during an extreme drought year in 2011. The refractory DOM from the Changjiang River flowed mainly through the South Branch. While in the lower South Branch, the input from the polluted Huangpu River contributed a large amount of biolabile DOM, demonstrating an anthropogenic perturbation from megacities. The DOM properties in the North Branch showed conservative behavior in the wet season, while noticeable addition was observed in the dry season, accompanied by the reversed flux of DOM from the North Branch to the South Branch, emphasizing the regular seasonal oscillation of the DOM dynamics in this monsoon-controlled bifurcated estuary. The estuarine turbidity maximum zones played distinct roles on DOM dynamics in different estuarine environments. The DOC and CDOM abundance in the Changjiang River and other Chinese rivers were at lower levels compared to other world rivers, showing a characteristic of the regional CDOM-poor features for many East Asia rivers.
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