Jianyao Chen

• Sun Yat-sen University

Exploration of the remobilization mechanism of trace metals in estuarine sediments remain challenging because of dynamic hydrochemical conditions. This study integrated a chemical sequential extraction procedure (BCR), the diffusive gradient in thin films (DGT) and high-resolution dialysis techniques, and Visual MINTEQ ver.3.1 to identify the seaso...

Sequential extraction was used to study the mobility and ecological risk of chemical fractions of six heavy metals in sediments collected from the Pearl River Delta (PRE) in China. Results revealed that residual fractions (F4) were the dominant forms for Cr and Ni in surface sediments, indicating that they were primarily stable in nature and had lo...

Aquatic ecological problems caused by pharmaceutical and personal care products (PPCPs) are increasingly becoming an issue of concern. In this study, the seasonal and spatial occurrence and environmental risk of 20 PPCPs were studied at 19 sampling points in the surface waters of the Lianjiang River basin (southern of China); its watershed is about...

Study region Zhanjiang City District, southwest of Guangdong Province, China, was selected as the case study area owing to its relatively frequent occurrence of droughts and groundwater overexploitation. Study focus This study presents a useful framework to characterize the propagation from meteorological drought (MD) to groundwater drought (GD) i...

Elucidating environmental evolution and its influencing factors in estuarine areas is essential to coastal and marine ecological management. In this study, the spatiotemporal distributions of organic carbon (OC), total nitrogen (TN), total phosphorus (including geochemical speciation), δ13C and nutrient ratios in sediments were explored to interpre...

Little is known about how microbial activity affects the hydraulic properties of karst aquifers. To explore the potential impacts of microbial activity on the hydraulic properties of karst aquifers, microbiological analysis, heat tracer, isotope (dissolved inorganic carbon isotope, δ13CDIC) and aqueous geochemical analyses were conducted at six mon...

Investigation of the speciation and remobilization mechanisms of chromium (Cr) in sediment is essential for accurate estimation of its ecological risks in aquatic systems. In this work, a three-step chemical extraction procedure and diffusive gradient in thin films (DGT) technique were combined to investigate the geochemical speciation, mobility po...

Estimates of change in global land evapotranspiration (ET) are necessary for understanding the terrestrial hydrological cycle under changing environment. However, large uncertainties still exist in our estimates, mostly related to the uncertainties in upscaling in-situ observations to large scale under non-stationary surface conditions. Here we use...

Land-atmosphere interactions play an important role in the changes of extreme climates, especially in hot spots of land-atmosphere coupling. One of the linkages in land-atmosphere interactions is the coupling between air temperature and surface energy fluxes associated with soil moisture variability, vegetation change, and human water/land manageme...

During the writing process, r a was omitted from Eq. (9) in Sect. 2.5 (p. 3809). The correct formula and derivation are as follows:

Heavy metal accumulation in marine sediments is associated with changes in both the natural environment and human activities. This study used heavy metals and Pb isotopes in a precisely dated (by 210Pb and 137Cs) sediment core from the Macao Sea to reconstruct the historical changes in anthropogenic activities and the environment in the western Pea...

Understanding the speciation and mobilization mechanisms of potentially toxic metals in sediments is critical to aquatic ecosystem health and contamination remediation in urban rivers. In this study, chemical sequential extraction, a thermodynamic chemical equilibrium model (Visual MINTEQ ver. 3.1), diffusive gradient in thin films (DGT), and high-...

Due to rapid economic development in the Pearl River Delta, South China, trace metals pose a significant threat to the coastal ecosystems. In this study, we investigated the spatial distribution, contamination status, ecological risk, and possible sources of trace metals in 150 surface sediment samples from the Macao sea area. The results showed th...

Evapotranspiration (ET) accompanied by water and heat transport in the hydrological cycle is a key component in regulating surface aridity. Existing studies documenting changes in surface aridity have typically estimated ET using semi-empirical equations or parameterizations of land surface processes, which are based on the assumption that the para...

Phosphorus (P) cycling present in sediments associated with iron (Fe), manganese (Mn) and sulfur (S) geochemical processes may cause secondary pollution in overlying water. Understanding the mechanisms of P release from sediments should help to restore water quality. This study used the diffusive gradients in thin film (DGT) technique to investigat...

In this study, we investigated the historical variation, source identification, and distribution of heavy metal pollution in sediments of the Pearl River Estuary (PRE) using 210Pb dating. Our results suggest that the heavy metal concentrations were higher in the western part of the estuary. For all heavy metals, Cd was significantly enriched in the...

The impact of anthropogenic activity on chemical weathering is still an open and significant topic that requires clarification to improve the understanding of watershed evolution. We analyzed river water and rainwater samples to characterize the variation in hydrochemical characteristics and influencing factors. Samples were taken from the Liuxi Ri...

Identifying the mobilization mechanisms and predicting the potential toxicity risk of metals in sediment are essential to contamination remediation in river basins. In this study, a sequential extraction procedure and diffusive gradients in thin film (DGT) were employed to investigate the mobilization mechanisms, release characteristics, and potent...

Vegetation carbon phenology is a key indicator of vegetation actual photosynthesis activity and regulates terrestrial ecosystem carbon balance. A comprehensive understanding of the structural difference of carbon phenology and greenness phenology is still lacking. This study evaluated the structural difference of vegetation greenness phenology and...

The characterization of groundwater (GW) and surface water (SW) interaction in riparian zones is of decisive importance for purifying and maintaining the water quality, and for protecting the riverine ecosystem. Through intensive monitoring using a combination of hydrochemical and biological analyses of the riparian GW and SW in the Liuxi River bas...

The concentrations, composition, sources, and risks of polycyclic aromatic hydrocarbons (PAHs) in topsoil and surface water of the Liuxi River basin, south China were analyzed in this study. The total concentrations of 16 PAHs ranged from 296.26 to 888.14 ng/g in topsoil and from 156.73 to 422.03 ng/L in surface water, indicating mild pollution. Th...

Fine particulate matter is associated with adverse health effects, but exactly which characteristics of PM2.5 are responsible for this is still widely debated. We evaluated seasonal dynamics of the composition and chemical characteristics of PM2.5 in Zhuhai, China. PM2.5 characteristics at five selected sites within Zhuhai city were analyzed. Sampl...

Nitrate (NO3-) pollution is a serious problem worldwide. Identification of NO3- sources and transformation processes in aquifers is a key step in effectively controlling and mitigating NO3- contamination. In this study, hydrochemical, microbial, and dual isotopic approaches were integrated to elucidate the sources and processes influencing NO3- con...

We developed a numerical model, RFLUX, which uses the heat tracer method for vertical groundwater flux estimation, and applied it to the Leizhou Peninsula, South China, to provide information to inform local groundwater resource utilization and management. The temperature–depth (TD) profiles of 24 boreholes, along with the observed ground surface t...

The purpose of this study was to evaluate the current status of metal concentrations in soil from Zhuhai City. We detected the concentrations of eight metal elements in 67 topsoil samples collected from three typical land use types (water source land, n = 27; industrial land, n = 25; and farmland, n = 15) in Zhuhai. Multivariate geostatistical anal...

The Pearl River Delta (PRD) has undergone rapid urban growth and industrial development during the past four decades, and human activities have become one of the most important factors affecting the environment in the region. Therefore, there is an urgent need to examine the influence of urbanization on surface water and groundwater systems. Based...

Submarine groundwater discharge (SGD) is an important source of freshwater, nutrients, and other chemicals to the coastal water, and has significant impacts and implications for the coastal environment and ecology. Here, we combined geochemical tracers and hydrologic modeling to investigate the spatial patterns and quantities of SGD and submarine f...

In karst areas, groundwater is an important water source for drinking and irrigation purposes; however, karst aquifers are vulnerable and recovery from damage is difficult. We collected surface water (pond and river water) and groundwater (hand-pump well, dug well, and borehole water) samples in Qingyuan city, China, to determine the major chemical...

Identifying contamination sources of environmental media and revealing their changing trends over time is useful for regional contamination control and environmental improvements. Four sediment cores (S1-S4) were collected from the Shima River to determine lead (Pb) concentrations, geochemical fractions and isotopic compositions, as well as the geo...

The concentrations of Cu, Zn, Pb, Cd, and As varied quite differently in the water, suspended particulate matter (SPM), and sediment along the middle reach of the Beijiang River in southern China. The total concentrations of trace metals and As in the water column were significantly affected by the concentration of SPM, while the metals and As in t...

Differentiating contribution of natural sources and anthropogenic inputs to soil element concentrations can provide important basis for pollution and risk assessments. Fifty-five surface soil samples were collected from farmland (n = 33) and forest land (n = 22) in the Leizhou Peninsula for the measurement of trace elements (Cr, Co, Ni, Cu, Zn, As,...

Five sediment cores (S1-S5) were collected from the Shima River to determine the bioavailability of trace metals (Cd, Cr, Cu, Ni, and Zn) using the modified European Community Bureau of Reference (BCR) procedure. The toxic effects of polluted sediment were assessed using the LUMISTox(®) bioassay with Vibrio fischeri and chemical models such as the...

Based on daily precipitation data sets of Leizhou Peninsula during 1984-2013, comparison between effective drought index (EDI) and standardized precipitation index (SPI) was performed in this paper. And then the spatiotemporal characteristics of drought events in different seasons. The results indicate that daily EDI and SPI for six-months time sca...

The spatio-temporal variability of precipitation extremes was investigated over the southeast coastal region of China, based on daily precipitation records from 73 meteorological stations for the period of 1960–2014. The standardized precipitation index (SPI), rotated empirical orthogonal function (REOF), and wavelet analysis methods were used to a...

Typhoon-related heavy rain has unique structures in both time and space, and use of satellite-retrieved products to delineate the structure of heavy rain is especially meaningful for early warning systems and disaster management. This study compares two newly-released satellite products from the Integrated Multi-satellitE Retrievals for Global Prec...

Reconstructing historical sedimentary records is essential for better understanding the effects of anthropogenic activities on river environments. We used lead-210 to date riverine sediment core from the Shima River in China. We obtained a sedimentary history of 34 years (1982–2015) for core S2, which had a length of 34 cm. The sedimentation rate o...

Metal pollution in sediments from the Shima River, a typical transboundary watercourse in the Pearl River Delta area, was investigated. Sediment cores were collected at eight sites from the upper to the lower reaches crossing Shenzhen, Dongguan and Huizhou cities. Sediment physicochemical properties and the total concentrations of trace metals (V,...

Groundwater sources supply fresh drinking water to almost half of the World's population and are a main source of water for irrigation across world. Characterization of groundwater resources, surfacegroundwater interactions and their link to the global water cycle and modern global change are important themes in hydrogeological research, whereas li...

The distribution, migration and potential risk of heavy metals in water and soil environments, related to city water supply, were investigated. Heavy metal concentrations in waters from the Shima River water ranged from not detected (n.d.) to 749 μg L(-1) for Mn, n.d. to 151 μg L(-1) for Ni, 7.00 to 494 μg L(-1) for Zn, n.d. to 93.0 μg L(-1) for Cu...

An analysis of the stable isotopes and the major ions in the surface water and groundwater in the Leizhou Peninsula was performed to identify the sources and recharge mechanisms of the groundwater. In this study, 70 water samples were collected from rivers, a lake, and pumping wells. The surface water was considered to have a lower salinity than th...

Anthropogenic activities in the Pearl River Delta (PRD) have caused a deterioration of groundwater quality over the past twenty years as a result of rapid urbanization and industrial development. In this study, the hydrochemical characteristics, quality, and sources of heavy metals in the groundwater of the PRD were investigated. Twenty-five ground...

Nitrogen aspects and hydrological processes need to be integrated in order to understand sources and relevant mechanisms. Landfills are the dominant disposal approach to deal with solid waste in urban areas in China. Landfills require adequate land and pose a potential threat to aquifer contamination, particularly in the humid zone, such as Guangzh...

Key Points Influence of model uncertainty on threshold

An experimental granitic catchment in southern China was instrumented to continuously monitor the hydrologic processes, within which two plots (5 m × 10 m) were equipped. Observed rainfall and corresponding responses of surface water, soil water, and groundwater were used to examine the hydrological threshold behaviors. New hydrological thresholds...

As the world's largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (d...

Rainwater percolation into bedrock and the contribution of bedrock groundwater flow to streamflow have been reported for several experimental catchments in China, Japan and the US. On the basis of previous studies, the particular runoff characteristics of granitic catchments were determined: (i) fast rainwater infiltration, (ii) obviously saturated...

Groundwater responses to tide fluctuations in different hydrogeological situations have been investigated for many years. Various solutions have been derived using the assumption that tides are composed of sinusoidal components, neglecting non-periodic variables. This approach has resulted in the introduction of some inaccuracy in predictions of gr...

Soil texture characteristics of a small coastal granite catchment in the Pearl River Basin in southern China were analyzed, revealing loamy sand and sandy loam as the main soil types in this catchment. Rainfall-runoff processes were then analyzed on the basis of the observation of precipitation, runoff yield, and soil water content at two experimen...

In order to understand the distribution and behavior of selected endocrine-disrupting chemicals (EDCs) in the Pearl River Delta, China, the concentrations of EDCs in water and suspended solid of rivers were quantified in agricultural, urban, and industrial zones of Dongguan watershed by GC/MS. In the last two zones, the concentration of EDCs in riv...

Water balance components of the North China Plain (NCP) were analyzed, indicating the decrease both in precipitation and evaporation. The decreased precipitation and expansion of water use for agriculture, industrial and domestic purposes have caused a water crisis, which was managed until now by diverting water from the Yellow River and over explo...

Groundwater discharge flux to the sea plays an important role in the environmental change of the coastal zone, but little research has been done on the relationships among groundwater, surface water and sea water in the Pearl River Delta area in southern China. This paper establishes a three-dimensional groundwater flow model focused on the Zhuhai...

The great spatial and temporal variability of nitrogen (N) processing introduces large uncertainties for quantifying N cycles in large scales, e.g. a watershed scale, and hence challenges the present techniques in measuring ecosystem N mass balance. The dual isotopes of nitrate (δ18O and δ15N) integrate signals for both nitrate sources and N proces...

Resistivity survey and measurement of groundwater conductivity were performed in 2003 and 2004, to investigate the distribution of fresh and salt groundwater in the Yellow River Delta where due to rapid increasing of river sedimentation and over irrigation, water environment problems such as temporary zero-flow of the river occur. Radiocarbon datin...

In light of the current problems facing the Yellow River and surrounding areas (e.g., periods of zero river discharge, increasing nitrate concentrations of the Bohai Sea), we examined the coastal mixing dynamics around the mouth of the Yellow River. Naturally occurring radium isotopes (223Ra, 224Ra, 226Ra, and 228Ra) and other geochemical tracers (...

1] Naturally occurring chemical tracers were used to assess the magnitude of submarine groundwater discharge (SGD) during two different sampling periods at a coastal site south of the Yellow River delta, China. We used salinity and pH as indicators of the terrestrial and recirculated seawater components of discharging groundwater and radium isotope...

The groundwater flow system and the flow velocity in the alluvial fan plain of the Hutuo River, China, have been studied, with an emphasis on relating geochemical characteristics and isotopes factors. Seven stretches of one river, six springs and 31 wells, with depths ranging from 0 m (river waters) to 150 m, were surveyed. The groundwater has a ve...

Spatial and temporal variations of submarine groundwater discharge (SGD) have been evaluated by automated seepage meters from the Yellow River delta to 7 km offshore in the Bohai Sea, China. We identified three zones from the coast to offshore based on different relationships between tidal and SGD changes. Our results indicate that the point of max...

Located at southern coast of China, the Pearl River Delta (PRD) is facing serious water problems in both quantity and quality after its rapid urbanization in the last decade. Most remarkably, the local groundwater, that was used to be the source of drinking water before the urbanization was polluted due to poor management of the septic tanks. In or...

Nitrate pollution of groundwater in the Yellow River delta, China is an important issue related not only to nitrate dispersion and health concerns but also to mass transport and interactions of groundwater, sea, and river waters in the coastal area. The spatial distribution of nitrate, nitrate sources, and nitrogen transformation processes were inv...

Wastewater irrigation was initiated as early as 1958 in the suburb of Shijiazhuang, China. This has resulted in groundwater becoming contaminated by nitrate to a depth of about 100 m with an average concentration of 40 mg . The annual average irrigation rate of wastewater in this area is about 430 mm, and the water table is relatively stable in con...

A survey of the quality of groundwater across a broad area of the North China Plain, undertaken in 1998 to 2000, indicates that nitrate pollution is a serious problem affecting the drinking water for a vast population. The use of nitrogen (N)-fertilizer in agriculture has greatly increased over the past 20 years to meet the food needs of the rapidl...

The North China Plain (NCP) is an important agricultural area in China and has a high population density. Serious water shortages have occurred in this region over the last 20 years. Water transfer from the Yangtze River (the east route) was initiated in the year 2002 to provide water for the major cities of the NCP. This study was carried out befo...

The energy balance components were measured above the surface of an irrigated wheat and maize field over three successive years using the Bowen ratio technique. The experiments were carried out at Luancheng Experimental Station of Agro-ecosystem (LESA), Heibei, China, from December 1999 through to September 2001. The seasonal course of energy balan...

Urban wastewater has been used for irrigation in regions where water is scarce. Re-use of wastewaters is therefore a challenging possibility for managing regional water resources. It is important to re-assess the long term impacts of wastewater irrigation practices on regional groundwater quality. Wastewater irrigation practices in the North China...

The characteristics of evapotranspiration and canopy surface conductance of winter wheat have been measured and analysed by using the Bowen ratio–energy balance (BREB) method. In order to understand better the effect of soil water status on evapotranspiration and conductance of wheat, the daily and seasonal variations of leaf stomatal resistance un...

Hydrological and geomorphological information can be extracted from digital terrain models (DTMs), based on the assumed single or multiple flow directions of each pixel. A traditional time-area graph and a unit Hydrograph can be constructed for either a spatially varied or a uniform given velocity field, and therefore a formula has been proposed to...