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Contrasting Eutrophication Risks and Countermeasures in Different Water Bodies: Assessments to Support Targeted Watershed Management


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Eutrophication is a major problem in China. To combat this issue, the country needs to establish water quality targets, monitoring systems, and intelligent watershed management. This study explores a new watershed management method. Water quality is first assessed using a single factor index method. Then, changes in total nitrogen/total phosphorus (TN/TP) are analyzed to determine the limiting factor. Next, the study compares the eutrophication status of two water function districts, using a comprehensive nutritional state index method and geographic information system (GIS) visualization. Finally, nutrient sources are qualitatively analyzed. Two functional water areas in Tianjin, China were selected and analyzed: Qilihai National Wetland Nature Reserve and Yuqiao Reservoir. The reservoir is a drinking water source. Results indicate that total nitrogen (TN) and total phosphorus (TP) pollution are the main factors driving eutrophication in the Qilihai Wetland and Yuqiao Reservoir. Phosphorus was the limiting factor in the Yuqiao Reservoir; nitrogen was the limiting factor in the Qilihai Wetland. Pollution in Qilihai Wetland is more serious than in Yuqiao Reservoir. The study found that external sources are the main source of pollution. These two functional water areas are vital for Tianjin; as such, the study proposes targeted management measures.
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International Journal of
Environmental Research
and Public Health
Contrasting Eutrophication Risks and
Countermeasures in Different Water Bodies:
Assessments to Support Targeted
Watershed Management
Tong Li, Chunli Chu *, Yinan Zhang, Meiting Ju and Yuqiu Wang
College of Environmental Science and Engineering, Nankai University, Tianjin 300350, China; (T.L.); (Y.Z.); (M.J.); (Y.W.)
*Correspondence:; Tel.: +86-138-2138-5387; Fax: +86-222-350-6446
Academic Editor: Yunlin Zhang
Received: 19 May 2017; Accepted: 25 June 2017; Published: 29 June 2017
Eutrophication is a major problem in China. To combat this issue, the country needs
to establish water quality targets, monitoring systems, and intelligent watershed management.
This study explores a new watershed management method. Water quality is first assessed using
a single factor index method. Then, changes in total nitrogen/total phosphorus (TN/TP) are
analyzed to determine the limiting factor. Next, the study compares the eutrophication status
of two water function districts, using a comprehensive nutritional state index method and geographic
information system (GIS) visualization. Finally, nutrient sources are qualitatively analyzed. Two
functional water areas in Tianjin, China were selected and analyzed: Qilihai National Wetland
Nature Reserve and Yuqiao Reservoir. The reservoir is a drinking water source. Results indicate that
total nitrogen (TN) and total phosphorus (TP) pollution are the main factors driving eutrophication
in the Qilihai Wetland and Yuqiao Reservoir. Phosphorus was the limiting factor in the Yuqiao
Reservoir; nitrogen was the limiting factor in the Qilihai Wetland. Pollution in Qilihai Wetland is
more serious than in Yuqiao Reservoir. The study found that external sources are the main source of
pollution. These two functional water areas are vital for Tianjin; as such, the study proposes targeted
management measures.
eutrophication; single factor evaluation; comprehensive eutrophication state index;
watershed management
1. Introduction
Eutrophication is a significant worldwide environmental problem. Eutrophication is a form
of water pollution, caused by excessive loading of dissolved and particulate organic matter and
inorganic nutrients (C, N, and P). Eutrophication risk refers to the possibilities and consequences of
eutrophication [
]. Visible effects of eutrophication include the development of planktonic scum and
rooted plant biomass, increased algal growth, the death of fish, increased sedimentation, decreased
dissolved oxygen concentration, and reductions in water transparency [2].
As the population has increased in coastal watersheds, there has been an increase in the transport
of nutrients to lakes, ponds, and estuaries [
]. The resulting eutrophication has had many adverse
effects within the estuaries [
]. For example, increased nitrogen loading can lead to phytoplankton
blooms [
]. These blooms, in turn, lead to the loss of important estuarine habitats, such as sea grass
meadows. Sea grass meadow loss is associated with the loss of important commercial shell fish and
finfish species, such as cod [
], bay scallops [
], and blue crabs [
]. Eutrophic estuaries can also
Int. J. Environ. Res. Public Health 2017,14, 695; doi:10.3390/ijerph14070695
Int. J. Environ. Res. Public Health 2017,14, 695 2 of 18
suffer from anoxia [
], harmful algal blooms, and brown tides [
]. Regime shifts from macrophyte
dominance to phytoplankton dominance have also been widely reported, in locations such as Lake
Christina, Lake Karibaand and Lake Krankesjon [
]. These changes are driven by various factors,
such as climate, nutrients, lake depth, and lake size [16].
China is a rapidly developing country, and eutrophication has become the most widespread water
quality problem [
]. The eutrophication of most lakes and reservoirs in China seriously threatens the
regional ecological environment and water security, and has restricted the sustainable development of
society and the economy. In past decades, excessive nutrient loading has led to algal blooms in Lake
Chao [
], Lake Dianchi [
], and Lake Tai [
]. The rapidly accelerating pace of eutrophication
in lakes across the country has forced the government to set ambitious lake restoration goals [23].
In general, phosphorus (P) supply is thought to regulate algal production in freshwater
lakes [
]. In contrast, nitrogen (N) supply is the predominant constraint in many estuaries
and shallow marine environments [
]. Integrating numerical modeling of P and N based on
monitoring, assessing, and predicting the state and changes in watershed nutrients is needed to control
eutrophication and management [30].
In China, management tools and policies are proposed and implemented at the provincial
level [
]. Therefore, management strategies are best considered within a single region. Compliance
with water quality indicators has historically been used as the standard threshold for triggering
management measures. This approach does not consider the differences in system responses in
different regions. Further, few eutrophication control strategies reflect the differences in lake basin
characteristics [
]. Many past studies have considered the quality of a specific water body; however,
few studies have considered different functional water areas in a region. Further, using traditional
water quality criteria alone is insufficient to measure eutrophication levels. Traditional water quality
standards are generally based on toxicological tests. Toxic or harmful substance concentrations or
thresholds have served as an assessment baseline; however, there is a negative feedback mechanism
between these concentrations and the health of aquatic organisms [
]. The lake nutrient standard
is a nutrient variable threshold that corresponds with lake ecosystems; this value reflects the most
natural conditions (the state before the large-scale interference of human activity) [
], at which N, P,
and other nutrients have fewer toxic effects on aquatic organisms.
This background highlights the importance of developing targeted management measures to
reduce eutrophication and potentially harmful phytoplankton activity. Different water bodies have
different water quality targets, hydrological characteristics, and different surroundings. Different
water quality targets should be set based on different water uses, allowing the adoption of targeted
management measures.
This study investigated two different water bodies within one region, to assess their different
water targets. These water bodies are located in Tianjin Province in north China, and have different
water functions and quality targets. This study selected and analyzed their eutrophication indicators,
to identify water quality responses to load reduction and other appropriate management measures.
The first water body is the Yuqiao Reservoir, a lake that provides drinking water. It has second class
water quality requirements under the GB3838 Chinese water quality standard. The second water body
is a core area of the Qilihai Reserve, which is one of the National Nature Reserves. It has first class
water quality requirements under the GB3838 Chinese water quality standard.
The goal of this study was to develop an effective watershed management method. First, water
quality was assessed using the single factor index method, and then reassessed by analyzing changes of
TN/TP to determine the limiting factor. The eutrophication statuses of the two water bodies were then
compared based on the comprehensive nutritional state index method and geographic information
system (GIS) visualization. Finally, nutrient sources were qualitatively analyzed and management
measures were proposed. This included exploring different eutrophication treatment and management
measures based on specific loads. There were three key study components: (A) an entrophic index
system was established; (B) a time series analysis was conducted to reflect eutrophication trends;
Int. J. Environ. Res. Public Health 2017,14, 695 3 of 18
and (C) recommendations were made based on contrasts between the eutrophication analysis and
nutrient source analysis.
2. Materials and Methods
2.1. Study Area
Two water bodies with different functions were selected as the study areas. Figure 1shows their
locations. One is the Yuqiao Reservoir, which provides drinking water and it is located in the north of
Tianjin. The other is the Qilihai Wetland, which preserves natural ecological diversity as a national
nature protection area. It is located in the middle of Tianjin. The two reservoirs provide different water
functions and have separate water quality requirements.
Int.J.Environ.Res.PublicHealth2017,14,695 3of17
Figure 1. Location of the two studied water bodies located in Tianjin Province in China.
The Yuqiao Reservoir, located in Ji County in China’s Tianjin Province (40
02’ N, 117
25’ E),
was formed in 1965 to meet water needs, mainly hydropower and irrigation. It has been the only
water supply in Tianjin City (population of more than 10 million) since 1983. The river’s total area is
1627 km
. The average water depth is 4.3 m; the total capacity is 1.559 billion m
; and the controlled
drainage area is approximately 2060 km
. The Shahe River, the Lin River and the Li River are the
main tributaries. The south bank of the reservoir is steep and the north shore is a relatively flat
plain. The reservoir-controlled watershed is a temperate continental monsoon sub-humid climate.
The annual average temperature is 10.4 to 11.5
C; and the annual average precipitation is 748.5 mm,
mainly concentrated from June to September [35].
Water safety poses a serious threat in this area. According to the “Regulations on the Protection of
Drinking Water Sources” of China, drinking water source protection areas should be classified based on
different water quality standards and protection requirements. As a drinking water source protection
area, Yuqiao Reservoir is generally divided into primary protected areas and secondary protected
areas; if necessary, quasi-protected areas can be added. The regulations note that protected areas at all
levels should have clear geographical boundaries, and all levels of protected areas and quasi-protected
areas should provide clear water quality standards and deadlines for achieving them. Cross-regional
Int. J. Environ. Res. Public Health 2017,14, 695 4 of 18
rivers, lakes, reservoirs, water transport channels in the region’s upper reaches should not affect
the downstream water quality standards of the Yuqiao Reservoir. Water in the Yuqiao Reservoir is
considered a primary protected area. The regulations state that quality standards for primary protected
areas should not be lower than those of the “GB3838-88 Surface Water Environmental Quality Standard”
Class II standard.
In the protected area of the Yuqiao Reservoir, all activities that may damage or destroy the
ecological balance of the environment and forests, water, vegetation and water sources are prohibited.
This includes dumping industrial waste, garbage, feces, and other city wastes into the waters; the
use of highly toxic and high pesticide residues; the abuse of fertilizers; planting and raising livestock,
poultry, and aquaculture activities; and all tourism activities and other activities that may cause water
pollution. In addition, no construction may discharge pollutants into the water body; reconstruction
projects must reduce pollutant discharges; and original sewage outfalls must cut sewage discharge to
ensure that the water quality in the protected area meets prescribed water quality standards.
Wetlands are known as the “kidney of the earth.” Each wetland is a natural community, formed
by the interaction of land and water systems [
], and having multiple ecological functions. The Qilihai
Wetland (39
17’ N, 117
34’ E) is located in Ninghe County in eastern Tianjin, on the west bank of the
Bohai Bay. In 1992, the Qilihai Wetland was approved by the government as a national marine nature
reserve. The government is responsible for protecting and managing the natural environment and
ecosystems of the Shell embankment, which is an oyster reef containing rare ancient coastal relics
and wetlands in China [
]. The Qilihai Wetland covers 45.15 km
and has many ecological functions.
It provides water for surrounding rivers, controls flooding, and prevents soil from desertification.
The Qilihai Wetland is a national marine area with precious ancient coastal ruins; the wetland’s natural
environment and its ecosystem are clear targets for protection and management.
As wetlands have become over-developed by human activities, the biological diversity has
decreased, and ecosystem services and other functions have been degenerated [
]. The water
environment has been polluted with heavy eutrophication and significant nitrogen, and the water
resources have decreased. Based on these factors, the Qilihai Wetland national nature reserve should be
managed by the appropriate administrative department within the provincial people’s government or
under the State Council [
]. All units and individuals should be obligated to protect nature resources
in Qilihai Wetland, and the government should have the right to report and prosecute any unit or
individual that has destroyed or occupied the reserve. No production facilities should be built in the
core area and buffer zone of the Qilihai Wetland.
As in the reservoir area, in the Qilihai Wetland, it is prohibited to build production facilities that
may pollute the environment and destroy resources or landscapes; for other construction projects, the
pollutant emissions should not exceed national and local pollutant emission standards. For facilities
already built in the study area, any pollutant discharges that exceed state and local government
standards should be treated within a prescribed time limit. If damage has been caused, remedial
action must be taken. These rules should keep water quality in Qilihai Wetland at or above the first
grade of Environmental Quality Standard for Surface Water. The following activities are prohibited in
the wetland: logging, grazing, hunting, and fishing, reclamation, burning, quarrying and dredging.
In addition, it is prohibited to visit and conduct tourism projects in the Qilihai Wetland. Construction
in the peripheral protection zone must not damage the environmental quality of the Qilihai Wetland.
If damage has been caused, it must be corrected within a set time limit.
2.2. Water Quality of the Two Reservoirs
Many scholars have developed different water quality evaluation methods [
]. Single factor
assessment methods are widely used for rivers [
], reservoirs, and lakes. For example, Yang et al. [
assessed groundwater quality using a single factor and concluded that the groundwater quality in the
southern region Ordos basin was generally poor when considered in terms of national groundwater
quality standards. A comprehensive index approach, such as the Water Quality Monitor (WQM), was
Int. J. Environ. Res. Public Health 2017,14, 695 5 of 18
developed by the National Sanitation Foundation (NSF) [
]; other modified, but sound, water quality
indicators have been developed based on this approach [
]. Most studies use physical, chemical, and
biological characteristics to evaluate existing water quality and pollution statuses [
]. For example,
physical characteristics include dissolved oxygen (DO), hydrogen ion concentration (PH), transparency
(SD) and temperature [
]. Chemical characteristics include total nitrogen (TP), total phosphorus
(TN), chemical oxygen demand (COD), biochemical oxygen demand (BOD), petroleum, and heavy
metals [
]. Biological characteristics include chlorophyll a, benthos biomass, and diversity of rare
species [
]. TN and TP are often used to indicate the degree of nutrient contamination in a water
body; transparency reflects the clarity of the water body; the permanganate index (COD
) reflects
organic and inorganic oxidizable substance pollution in the water; and chlorophyll a (Chl-a) reflects
the amount of phytoplankton in the water. We have used these as indicators to assess the water quality
of the two reservoirs.
Based on the hydraulic characteristics of the surface water, three monitoring points (Figure 2a)
were established in the Yuqiao Reservoir. We collected data from the three monitoring points in
the Sanchakou, the reservoir center, and the dam. The average measures across the three locations
provided the data for analysis. In addition, we set up three monitoring points around Bird Island
(Figure 2b) in Qilihai Wetland Nature Reserve and used the annual average of the three monitoring
points to reflect water quality.
Int.J.Environ.Res.PublicHealth2017,14,695 5of17
nitrogen(TP),totalphosphorus(TN),chemicaloxygendemand(COD), biochemical oxygen demand
(a) (b)
, ,
GradeII40.50.025‐ ‐
GradeIII610.05‐ ‐
Figure 2.
) Sampling points for Yuqiao Reservoir; (
) Sampling points for Qilihai Wetland
Nature Reserve.
The single factor index method is a relatively simple and useful method to assess water quality [
and is used to evaluate the water quality in this study.
The single factor index evaluation method is presented as:
In this expression, S
is the standard index of the water quality parameter iat point j.C
is the
concentration of water quality parameter iat jpoint (mg/L); C
is water quality standard i, (mg/L),
whose value is regulated by the standard of “surface water environmental quality” (GB3838-2002) in
Table 1.
Table 1. Cs,j of the two reservoirs (mg/L).
Indicators CODMn TN TP Chl-a SD
Grade I 2 0.2 0.02 - -
Grade II 4 0.5 0.025 - -
Grade III 6 1 0.05 - -
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2.3. Eutrophication Situation
Different scholars have proposed many eutrophication evaluation models [
]. Yang et al. used
a series of artistic neural networks to develop an eutrophication assessment model for aquaculture
water areas [
]. Wu et al. established a hybrid model combining water quality indicators and
ecological response indicators to assess eutrophication, and then applied it to assess the status
of eutrophication from 2007 to 2008 in the southwest Bohai Sea [
]. Huo et al. established a
region-specific lake eutrophication assessment standard using a frequency distribution method based
on Chl-a concentration [
]. Liu et al. used a water quality modeling-based scenario analysis approach
to quantitatively evaluate how eutrophication in Lake Dianchi responded to an under-construction
water diversion project [
]. These evaluation methods have advantages and disadvantages; many are
subjective, and calculations are complex, error-prone, and inconvenient.
Based on the China Environmental Monitoring Center’s “Lake Reservoir eutrophication
evaluation methods and classification of technical requirements,” many scholars use an integrated
nutritional status index method to assess eutrophication in lakes. The comprehensive nutritional status
index method has matured and the evaluation range is more comprehensive than other nutritional
index methods. The evaluation factors comprehensively consider indexes such as TN, TP, SD, Chl-a
and COD
. Further, the method has mitigated the single evaluation factor ’s lack of evaluation.
We used the eutrophication index to assess the eutrophication of the two reservoirs. The equation is:
TLI () =
In this expression, TLI (
) is the comprehensive nutritional status index; W
is a normalized
weighted value of index j; and TLI (j) is the eutrophication evaluation universal index of index j.
Studies by Jin summarize the correlation coefficient between the Chl-a and other parameters in
China’s lakes and reservoirs; these provide an important basis for calculating weights [
]. With Chl-a
as the reference parameter, the normalized correlation weight of the index j parameter is calculated
as follows:
In this expression, r
is the correlation coefficient between the index j parameter and the reference
parameter Chl-a; m is the number of evaluation parameters. Table 2shows the correlation between the
Chl-a and other parameters in Chinese lakes (reservoirs).
Table 2. The correlation between lake parameters (reservoir), Chl-a, and rij, r2ij and weights (Wj).
Parameter Chla TP TN SD CODMn
rij 1 0.84 0.82 0.83 0.83
r2ij 1 0.7056 0.6724 0.6889 0.6889
Wj0.26626 0.18787 0.17903 0.18342 0.18342
After calculating the eutrophication index, we classified reservoir eutrophication into five different
grades according to the grading standards. Table 3lists these grades. In the same nutritional state,
the higher the index value, the more severe the nutritional level.
Table 3. Grading standards of eutrophication.
Grades Values
Oligotrophic TLI () < 30
Mesotrophic 30 TLI ()50
light eutrophic 50 < TLI ()60
middle eutrophic 60 < TLI ()70
hyper eutrophic TLI (op) > 70
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3. Results and Discussion
3.1. Physical and Chemical Characteristics of Water Quality
Tables 4and 5show the physicochemical characteristics of the water samples; Figure 3a,b show
the Single Factor Pollution Index. According to the surface water environmental quality standard
classification and water environment basic project standard limit (National Standard of the People’s
Republic of China, Environmental Quality Standards for Surface Water, GB3838-2002), the Yuqiao
Reservoir’s surface water quality is consistent with second class water environmental quality standards.
For the Qilihai Wetland, the surface water quality is consistent with first class water environmental
quality standards.
Table 4. Monitoring results of the water environment single indices in Yuqiao Reservoir.
Test Items 2010 2011 2012 2013 Standard Interval
CODMn 3.933333 3.733333 4.603333 3.2 II 4
TN 1.013667 0.816667 4.266667 2.333333 II 0.5
TP 0.023333 0.033333 0.056667 0.05 II 0.025
III 0.05
Chl-a 13.53333 10.41 16.4 10.66667 -
SD 0.5 0.8 0.83 0.9 -
Table 5.
Monitoring results of the water environment single indices in Qilihai Wetland Nature Reserve.
Test Items 2010 2011 2012 2013 Standard Interval
CODMn 22.30 17.53 28.33 14.99 I2
TN 1.69 2.45 2.43 3.08 I0.2
1.5 < V 2.0
TP 0.192 0.168 0.268 0.167 I0.02
0.2 < IV 0.3
Chl-a 87.209 33.45 92.85 54.70
SD 0.38 0.18 1.23 0.27
The average concentration of COD
in the Yuqiao Reservoir ranged from 3.2 to 4.6 mg/L; the
single factor pollution index of COD
ranged from 0.800 to 1.151 with an average value of 0.967.
In 2012, the average concentration of COD
exceeded the limit for water quality criteria Grade II,
but in 2013 there was a significant decline. The COD
pollution index at the sampling stations met
the expected class of water quality standards except in 2012. The TN concentration was higher than
the limit for water quality criteria Grade II during the monitoring period. The single factor pollution
index of TN ranged from 1.633 to 8.533, with an average value of 4.215. The single factor pollution
index exceeded Grade II of the water quality standards for four years. This indicates the significance
of nitrogen pollution.
In recent years, the TP concentration continued to rise. The single factor pollution index of TP
ranged from 0.933 to 2.267 with an average value of 1.633. From 2011 to 2013, the single factor pollution
index exceeded the Grade II of water quality standards. Further, the transparency value was lower
than the lake eutrophication standard of 2.4 m, indicating that the reservoir was eutrophic. Table 4and
Figure 3b show the COD
TN and TP concentration trends in the Qilihai Wetland Nature Reserve;
the concentrations fluctuate, but all of them exceed the surface water environmental quality standards
of the first Grade and some exceed Grade IV. In 2011 to 2013, the nitrogen concentration significantly
exceeded Grade V of the surface water environmental quality standard.
Int. J. Environ. Res. Public Health 2017,14, 695 8 of 18
Figure 3.
) Trend in the single factor pollution index for Yuqiao Reservoir; (
) Trend in the single
factor pollution index for Qilihai Wetland Nature Reserve.
The single factor pollution index of COD
ranged from 7.495 to 14.165 with an average value
of 10.390. The single factor pollution index of TN ranged from 8.45 to 15.40 with an average value
of 12.06. The single factor pollution index of TP ranged from 8.35 to 13.40, with an average value
of 9.91. And the transparency was also lower than the lake eutrophication standard which is 2.4 m.
Of these values, the nitrogen concentration is particularly significant, indicating the serious pollution
impacting the water quality of Qilihai Wetland. TN and TP were the main factors in these two water
areas that exceed the standard.
As mentioned above, the single factor indexes of COD
and TP in Qilihai Wetland were almost
10 times the indexes of Yuqiao Reservoir. There are many reasons for high COD
concentrations in
Qilihai Wetland, including industrial and agricultural activities, other discharges, domestic sewage,
and rubbish. In addition, the chlorophyll concentration in Qilihai Wetland is much higher than the
concentration in Yuqiao Reservoir. This may be because the industrial wastewater and domestic
sewage surrounding Qilihai Wetland and the farmland shore generated more surface runoff with more
nutrients. This supports algae growth and reproduction. The results of the single factor pollution
index method follow in Figure 3.
3.2. Ratio Changes of TN/TP
The TN/TP ratio continuously fluctuated in the two water bodies. The total nitrogen levels were
related to ammonia nitrogen and nitrite levels in water. Ammonia nitrogen in the water was also
Int. J. Environ. Res. Public Health 2017,14, 695 9 of 18
not stable. After biological assimilation, the remaining dissolved oxygen was present in sufficient
conditions. Many nitrifying bacteria oxidized to nitrite nitrogen. In the flood season, a variety of
nitrifying bacteria and dissolved oxygen were reduced, leading to ammonia nitrogen and nitrite
nitrogen conversion. The transformation process resulted in excessively large ammonia and nitrite
nitrogen concentrations over the course of a few months. Therefore, the total nitrogen increased;
on the contrary, it decreased. However, during the drought period, due to the role of denitrification,
anaerobic, or hypoxia, nitrate nitrogen (NO
) served as an acceptor. This reduced other gaseous
oxides of nitrogen or nitrogen. This leads to the reduction of nitrate nitrogen and total nitrogen in
water, gradually reducing the water storage capacity. The reservoir’s water storage capacity affects
TP changes, because when the water storage capacity is gradually reduced, it promotes sediment
redox, mineral dissolution and adsorption, and bacteria and microbe metabolism. This includes
hydrodynamics or bioturbation [
]. This resulted in phosphorus being released from the sediments;
the phosphorous then becomes an endogenous source contributing to the water phosphorus load.
Many factors modify the demand and supply of N and P for phytoplankton in the upper
lake waters. However, the TN/TP ratio helps predict which of the two most commonly limiting
macronutrients will become the most growth limiting under well-illuminated, stratified conditions [
In addition, the TN/TP ratio is an important factor affecting algal growth; it reflects the production
cycle and phytoplankton production in the water body [
]. Researchers generally believe that when
the TN/TP ratio is 10:1–25:1, there is a linear correlation between algae growth and nitrogen and
phosphorus concentration. This benefits algae growth, which is prone to eutrophication [62].
During the monitoring period, the TN/TP ratios in the Yuqiao Reservoir progressed from 43, 25,
75, and 47 from 2010 to 2013. The TN/TP ratios in the Qilihai Wetland progressed from 9, 15, 9, and
18 from 2010 to 2013. The TN/TP ratios in Qilihai Wetland ranged 10:1 and 25:1 from 2010 to 2013,
favoring algae growth. The TN/TP ratio in the Yuqiao Reservoir did not support algae growth during
the monitoring period. Algae growth and reproduction processes require a variety of nutritional
elements. If a certain nutrient is relatively low, growth and reproduction processes will be limited.
This element is called the “main limiting nutrient” [
]. Laguna et al. [
] noted that when TN/TP
exceeds 16, the phosphorus is in a restricted state; when TN/TP is less than 16, the nitrogen is in a
restricted state. Thus, phosphorus was the limiting factor in the Yuqiao Reservoir; nitrogen was the
limiting factor in the Qilihai Wetland.
3.3. Eutrophication Evaluation
Table 6shows the TLI of Yuqiao Reservoir from 2010 to 2013. TN, Chl-a, and SD level (the three
nutritional status indexes) were high. The degree of eutrophication in the Yuqiao Reservoir was highest
in 2012, with levels decreasing in decreasing degrees in 2013, 2010, and 2011. Water quality was in a
mesotrophic state (30
50) except during 2012 and 2013. The water quality in 2012 and 2013
was in light eutrophic state (50 < TLI (
60). This shows that from 2010 to 2013, Yuqiao Reservoir
water quality ranged between a mesotrophic and light eutrophic state. Eutrophication in 2012 was the
most serious. This may have been because of the self-purification capacity [
] of the Yuqiao Reservoir,
leading to an overall declining trend for the reservoir. Overall, the Yuqiao Reservoir water quality in
2010 to 2013 was still relatively good.
Table 7shows the TLI of the Qilihai Wetland Nature Reserve from 2010 to 2013. The nutritional
status index of TN showed a significant upward trend; strict measures are recommended to regain
and maintain control. The nutritional status index of TP, COD
, Chl-a, and SD fluctuated frequently
across the four years, indicating an unstable water environment. The degree of eutrophication of
Qilihai Wetland was highest in 2013, and declined across 2011, 2012, and 2010. The wetland was
in a hyper eutrophic state (TLI (
) > 70) for a long time, and the eutrophication trend continues to
rise. The nutritional indexes all significantly exceeded the standard. This shows that from 2010 to
2013, the water quality of Qilihai Wetland Reserve was significantly polluted, and already in a hyper
eutrophic state.
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According to Environmental Quality Standards for Surface Water (GB3838-2002), Qilihai Wetland
Nature Reserve falls within the scope of the first class. Yuqiao Reservoir falls within the second or
third class. With respect to monitoring results, the degree of eutrophication of Qilihai Wetland Nature
Reserve was far above the Yuqiao Reservoir (Figure 4).
Figure 4. Cont.
Int. J. Environ. Res. Public Health 2017,14, 695 11 of 18
Figure 4.
) Eutrophication trends in Yuqiao Reservoir in 2010 and 2011; (
) Eutrophication trends in
Yuqiao Reservoir in 2012 and 2013; (
) Eutrophication trends in Qilihai Wetland Nature Reserve from
2010 to 2013.
Table 6. Nutrient state index of Yuqiao Reservoir from 2010 to 2013.
Year TN TP CODMn Chl-a SD TLI (
2010 54.75995 33.33215 37.53206 53.29199 64.62706 48.99333
2011 51.09924 39.12455 36.14339 50.44245 55.50898 46.74031
2012 79.10711 47.74196 41.71763 55.37848 54.79479 55.57921
2013 68.88323 45.70931 32.04144 50.70696 53.22399 50.06019
Table 7. Nutrient state index of Qilihai Wetland Nature Reserve from 2010 to 2013.
Year TN TP CODMn Chl-a SD TLI (
2010 63.4189 67.55978 83.70305 73.52582 69.95113 70.80658
2011 69.70973 65.39123 77.29874 63.11916 84.44709 71.23871
2012 69.57088 72.97568 90.07175 74.2065 47.16393 71.09521
2013 73.58631 65.29427 77.23796 68.46024 76.58107 71.8827
3.4. Analysis of Nutrient Sources
The information above indicates that nutrients are the main cause of eutrophication. However,
the nutrient inputs differ between different water areas. As such, we analyzed nutrient sources from
both internal and external sources.
Int. J. Environ. Res. Public Health 2017,14, 695 12 of 18
3.4.1. Internal Sources
Sediment is an internal source of eutrophication, both in the Qilihai Wetland and in the Yuqiao
Reservoir. Sediments contain abundant nutrients and accumulate year to year. Accumulation is
particularly high in the summer, when there is more light, the water temperature is high, and nutrients
are easily released [65]. Therefore, the nutrients in the sediments are a driver for eutrophication.
Cheng [
] determined the total amount of contaminated sediment in Yuqiao Reservoir, which
contributes less to the water pollution than other sources. Past studies have shown that the total
nitrogen in the Qilihai wetland sediments was relatively enriched [
]. However, the nitrogen
analysis presented above is the limiting factor in the Qilihai Wetland, which is a relatively low
nutrient level relative to algae growth. Therefore, the sediment pollution contributes less to the
nutrient source. Nitrogen accumulation in the Qilihai Wetland is also due to human activities [
The sediment contributes little to the nutrient sources of the two water areas; the main source comes
from external sources.
3.4.2. External Sources
Point source controls around the Qilihai Wetland and the Yuqiao Reservoir have achieved certain
results, gradually reducing industrial point source pollution around the Qilihai Wetland and Yuqiao
Reservoir [
]. Non-point source pollution in the region comes from different sources, the pollution
load is large, and the pollution rate is very high.
In the Yuqiao Reservoir, where water inflow is generally stable, all nutrient types increased. There
are 129 villages close to the reservoir’s water environment [
]. As the number of urban residents
has increased, the amount of phosphorus containing detergents and domestic sewage discharge has
also increased, but the sewage treatment rate remained at almost zero. As the economy developed,
there was an increase in the cultivated land upstream of the Yuqiao Reservoir, with extended planting
times [
]. This increased the use of different chemical fertilizers and pesticide varieties; as the dosage
increased, farmland fertilizer was lost through surface runoff into the Yuqiao Reservoir. More recently,
the rapid development of aquaculture has led to the discharge of fish bait, small amounts of fertilizer,
and other fish products into the reservoir. This has accelerated the eutrophication rate. In addition,
there has been a decrease in the area of the Yuqiao Reservoir covered by aquatic plants [
], narrowing
the aquatic plant growth range. One plant species dominates the area, providing a basis for the further
algae growth.
The Qilihai Wetland Nature Reserve is one of the most eco-diverse ecological landscapes in Tianjin.
As such, it attracts tourists from all over the world, and tourism has been rapidly developing [
However, excessive tourism and tourists transfer the metabolites of tourist activities into the Qilhai
Wetland system, destroying the water environment. Tourism development has also expanded the
number and variety of dining establishments around the wetland. The wastes produced by dining
establishments further pollute the Qilihai Wetland’s water quality. Because of rapid aquaculture
development, there is also fishpond pollution in the Qilihai Wetland Nature Reserve [
]. The fish
bait and other fertilizer used to feed fish hinder water resources flow. This reduces the water’s
self-purification capacity, giving rise to water contamination. Similarly, the poor management of
aquatic organism distribution has also increased eutrophication of the Qilihai Wetland.
3.5. Management and Measures
Because it is the only water source in Tianjin, the water quality in the Yuqiao Reservoir is closely
linked to the life and health of its residents. This has attracted the attention of both government agencies
and residents, who work together to protect the Yuqiao Reservoir water quality. Several industries
around the reservoir that significantly polluted the water have been dismantled [
]. In addition,
residents work to consciously enhance reservoir awareness.
Int. J. Environ. Res. Public Health 2017,14, 695 13 of 18
There are many laws and regulations governing nature reserves, however, there are not enough
management institutions in the Qilihai Wetland to fully implement relevant conservation policies.
Due to a decentralized protection approach, the lack of sufficient infrastructure, and a lack of strong
financial support, the water pollution has become more serious. In addition, outreach about protected
areas has been insufficient; residents lack a sense of protection consciousness [
]. These factors
have resulted in greater pollution in the Qilihai Wetland than in the Yuqiao Reservoir. To prevent the
deterioration of eutrophication in Yuqiao Reservoir and in the Qilihai Wetland natural reserve, stricter
treatment methods and management measures are needed.
Appropriate control and management measures are needed; however, it is unwise to control
either nitrogen or phosphorus pollution alone. Based on the situation around the two water areas,
management policies are needed to improve water quality.
Appropriate measures are needed to introduce controls for different pollution sources. For
industrial pollution, the government should allocate special funds to address the pollution, close
polluting enterprises, and use advanced technology to reduce pollution emissions and production.
With respect to urban waste, the government should unify garbage collection and establish sites for
sanitary landfills. To address source pollution, the government can remediate water quality through
ecological restoration, dredging, and other technical means [
]. We recommend rehabilitating water
quality based on wetland type and water characteristics [
]. This may include establishing relevant
laws and regulations to regulate aquaculture and fisheries, strengthening poultry manure management,
applying the rational use of fertilizers and pesticides, strengthening the ability of vegetation to absorb
excess nutrients, paying attention to the rational distribution of aquatic organisms, and controlling
soil erosion.
In addition to these steps, the government should strengthen governance and management,
and at the same time, strengthen awareness. This includes encouraging local people to learn more
about environmental protection. Further, increasing the application of remote sensing, GIS and other
technical means will assist in eutrophication management, improve the targeted effects of management,
and promote effective management. In addition, due to the location and other characteristics of the
Yuqiao Reservoir, it is important to pay attention to and control nitrogen and phosphorus pollution
in the upstream river and around the river. It is also important to prohibit the development of
unsustainable tourism and to plan wetland structures rationally in the Qilihai Wetland.
Wetland water quality parameters are often related to hydrological processes and the growth
season of wetland vegetation [
]. Effective management requires carrying out dynamic monitoring
of the Qilihai Wetland water quality, establishing automatic prediction and alarm systems, and
strengthening research. Managing water functions is an important way to manage water resources.
A hierarchical management system combines river basin management and regional management to
form a water resources management system. Therefore, for the Qilihai Wetland Nature Reserve, which
has higher water quality requirements, management should be strengthened. At the same time, the
government cannot ignore the Yuqiao Reservoir management. To improve water quality in the long
term and bring water quality in line with water quality standards, governments and stakeholders
must restore and protect environmental quality through management tools, scientific research, and
technology projects. The government should also establish a protection target responsibility system
and quantitative assessment management approach. For different functional water areas in a region,
the government should be hierarchically managed and water areas should be managed to achieve
higher water quality standards.
This study does have a few limitations. First, the water quality assessment indicators could be
increased, allowing a more comprehensive analysis of results. In addition, while this article proposes
unilateral solutions, a more detailed quantitative or qualitative analysis would better determine
pollution mechanisms and more specific solutions. As the self-purification capacity of the Yuqiao
Reservoir and Qilihai Wetland Nature Reserve decline, further study of the ecological evaluation index
could accurately describe the problems. This highlights additional areas for future study.
Int. J. Environ. Res. Public Health 2017,14, 695 14 of 18
4. Conclusions
This study analyzed two typical water bodies in Tianjin, China, with different water quality
targets. Water quality was first assessed using the single factor index method; changes in TN/TP were
then analyzed to determine the limiting factor. Next, the eutrophication status of the two water areas
were compared, using a comprehensive nutritional state index method and geographic information
system (GIS) visualization. Finally, nutrient sources were qualitatively analyzed and management
measures were proposed.
In the Yuqiao Reservoir, the COD
concentration met the water quality standard every year
except 2012. The TN concentration fluctuated frequently; it consistently exceeded the standard.
The overall TP concentration exceeded the standard from 2011 to 2013. The Chl-a concentration
was consistent with the regular pattern .In contrast, the COD
, TN, and TP concentrations in the
Qilihai Wetland Nature Reserve fluctuated, but they all exceeded the surface water environmental
quality standards of the first level, as well as standards at Grade III or Grade IV. The change of Chl-a
concentration was particularly problematic. The water quality in the Qilihai Wetland was particularly
serious. The single factor index indicates that TN and TP were the main factors in the two areas that
led to the standard being exceeded.
The TN/TP ratio in the water bodies in the two study areas fluctuated continuously. During
the monitoring period, the TN/TP ratios in the Yuqiao Reservoir from 2010 to 2013 were 43, 25, 75,
and 47 respectively. The TN/TP ratios in the Qilihai Wetland from 2010 to 2013 were 9, 15, 9, and
18 respectively. Thus, phosphorus was the limiting factor in the Yuqiao Reservoir; nitrogen was the
limiting factor in the Qilihai Wetland.
From 2010 to 2011, the eutrophication level of the Yuqiao Reservoir was consistently in the
mesotrophic state. In 2012 and 2013, it was in a light eutrophic state. Because the surface water
environmental quality standard was classified as the first class, the Qilihai Wetland Nature Reserve
was consistently in a hyper eutrophic state from 2010 to 2013. Although there were some eutrophication
problems in the Yuqiao Reservoir, the pollution in the Qilihai Wetland was more serious.
The analysis shows that external pollution is the main source of pollution in the Yuqiao Reservoir
and the Qilihai Wetland. The main nutrient sources for the Yuqiao Reservoir come from the upper
reaches of the rivers that feed it; the nutrient load is excessive due to aquaculture development and the
poorly managed distribution of aquatic organisms. In the Qilihai Wetland, nutrients are mainly caused
by excessive tourism, aquaculture, and agriculture development.
Targeted management measures are needed to prevent the water quality of the Yuqiao Reservoir
and the Qilihai Wetland from continuing to deteriorate. These measures should be driven based
on different pollution sources; they require, however, an improvement in the area’s hierarchical
management system.
Water quality needs to meet the requisite standards and prevent harm to the human body. This
involves protecting water quality, and maintaining the economic and ecological benefits of wetlands
and reservoirs. To maintain both ecological and socio-economic significance, it is important to learn and
master the status quo and improve management efficiencies before implementing local government
policies. This is the primary message from this study.
Research was supported by National Key Technology R&D Program (Grant
No.2015BAJ01B00) and Key Project of Tianjin Municipal Education Commission (Study on the strategy and
countermeasures of promoting the transformation and upgrading of industry to green low-carbon and service in
Tianjin, 2014ZD). The authors would also like to thank the editors and anonymous reviewers for their insightful
comments and suggestions.
Author Contributions:
Chunli Chu conceived and designed the framework; Tong Li and Yuqiu Wang analyzed
the data; Tong Li and Yinan Zhang wrote the paper; Chunli Chu and Meiting Ju contributed to improving
the article.
Conflicts of Interest: The authors declare no conflict of interest.
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... Fishpond sediment contains nutrients and organic residues. Thus, nutrients such as phosphorous released from sediment and/or sludge over time may contaminate and eutrophicate groundwater and surface water [5][6][7]. ...
Wastewater and catfish pond sediment of catfish breeding in Mekong Delta Vietnam directly discharge into rivers or canals that is a cause of environmental problems. To solve this problem, the integrated catfish breeding was applied to reuse wastes from catfish pond as raw materials for other purposes. The method of material flow accounting (MFA) is used to assess the materials and wastes fluxes. The results show that wastewater form catfish pond can reuse for water morning glory and maize as water supply. Catfish pond sediment could make com-posting to supply for maize as organic fertilizer. Discharging wastewater into receiving canal was 74.1%, the rest is evaporated into the air (21.17%) and accumulated in the compost and biomass of cultivation plants (4.73%). The organic matters accumulated in cultivation plants and soil are 1.95% and 9.6% respectively, and the remaining amount is accumulated in the compost. Scaling up for 9 households have been assessed. The present research suggests that the integrated catfish system can reduce the discharging wastes into environment and prevents environmental pollution.
... Eutrophication is a major problem globally that has to be addressed by the definition of water quality targets, and establishment of monitoring systems and intelligent watershed management plans (Abell et al., 2020). Although it is critical to prevent water quality deterioration in lake catchment environments (Li et al., 2017c); conflict between environmental protection and economic development makes the task challenging (Mueller et al., 2019). Nevertheless, to improve lake water quality, and in turn aquatic ecosystem health, numerous strategies could be adopted. ...
Increasing cases of lake eutrophication globally have raised concerns among stakeholders, and particularly in China. Evaluating the causes of eutrophication in waterways is essential for effective pollution prevention and control. Xiao Xingkai Lake is part of and connected to Xingkai (Khanka) Lake, a boundary lake between China and Russia. In this study, we investigated the spatio-temporal variabilities in water quality (i.e., dissolved oxygen (DO), total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn) and ammonium-nitrogen (NH +4 -N)) in Xiao Xingkai Lake, from 2012 to 2014, after which a Trophic Level Index was used to evaluate trophic status, in addition to the factors influencing water quality variation in the lake. The DO, TN, TP, CODMn and NH +4 -N concentrations were 0.44–15.57, 0.16–5.11, 0.01–0.45, 0.16–18.31, and 0.19–0.78 mg/L, respectively. Compared to the Environmental Quality Standards for surface water (GB 3838-2002) in China, the lake transitioned to an oligotrophic status in 2013 and 2014 from a mesotrophic status in 2012, TN and TP concentrations were the key factors influencing water quality of Xiao Xingkai Lake. Non-parametric test results showed that sampling time and sites had significant effects on water quality. Water quality was worse in summer and in tourism and aquaculture areas, followed by agricultural drainage areas. Furthermore, lake water trophic status fluctuated between medium eutrophic and light eutrophic status from September 2012 to September 2014, and was negatively correlated with water level. Water quality in tourism and aquaculture sites were medium eutrophic, while in agricultural areas were light eutrophic. According to the results, high water-level fluctuations and anthropogenic activities were the key factor driving variability in physicochemical parameters associated with water quality in Xiao Xingkai Lake.
... This is caused mainly by human operations such as the excess P in fertilizers from farms, food for aquaculture, untreated, treated sewage, and industrial wastewater inputs. P enhancing the water environment (eutrophication) should be monitored (Bennett et al., 2006;Li et al., 2017). ...
Phosphorus (P) is a limited yet essential resource. P cannot be replaced, but it can be recovered from waste. We proposed the TRIZ approach (Teoria reszenija izobretatielskich zadacz - Rus., Theory of Inventive Problem Solving - Eng.) to identify a feasible solution. We aimed at minimizing the environmental impact and, by eliminating contradictions, proposed viable technical solutions. P recovery can be more sustainable based on circular economy and 4Rs (reduction, recovery, reuse, and recycling). The TRIZ approach identified sewage sludge (SS) as waste with a large potential for P recovery (up to 90%). Successful selection and application of SS management and P recovery require a transdisciplinary approach to overcome the various socio-economic, environmental, technical, and legal aspects. The review provides an understanding of principles that must be taken to improve understanding of the whole process of P recovery from wastewater while building on the last two decades of research.
... This is caused mainly by human operations such as the excess P in fertilizers from farms, food for aquaculture, untreated, treated sewage, and industrial wastewater inputs. P enhancing the water environment (eutrophication) should be monitored (Bennett et al., 2006;Li et al., 2017). ...
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Phosphorus (P) is a limited yet essential resource. P cannot be replaced, but it can be recovered from waste. We proposed the TRIZ approach (Teoria reszenija izobretatielskich zadacz-Rus., Theory of Inventive Problem Solving-Eng.) to identify a feasible solution. We aimed at minimizing the environmental impact and, by eliminating contradictions, proposed viable technical solutions. P recovery can be more sustainable based on circular economy and 4Rs (reduction, recovery, reuse, and recycling). The TRIZ approach identified sewage sludge (SS) as waste with a large potential for P recovery (up to 90%). Successful selection and application of SS management and P recovery require a transdisciplinary approach to overcome the various socioeconomic , environmental, technical, and legal aspects. The review provides an understanding of principles that must be taken to improve understanding of the whole process of P recovery from wastewater while building on the last two decades of research.
... The direct disposal of pond bottom sludge causes environmental degradation, nitrate accumulation in the aquifer, and surface water nutrient enrichment being of concern to pond bottom sludge aquaculture. Nutrients and organic residues tend to accumulate at the bottom and are thus to some extent removed from the water phase while nutrients such as phosphorous released from sediment over time may contaminate and euthrophicate groundwater and surface water (Avnimelech and Ritvo, 2003;Li et al., 2017). ...
This study develops a method to reuse aquaculture wastewater and sediment from a catfish pond in order to increase agricultural productivity and protect the environment. Material flow analysis (MFA) is a central concept of this study that involves collecting catfish pond wastewater (CPW) and reusing it to irrigate five water spinach (Ipomoea aquatic) ponds before discharging it into a river. Typically, catfish pond sediment (CPS) was collected and composted to produce organic fertilizer for cornfields. The results revealed that pollutant removal efficiency of wastewater from CPW (by using water spinach) were total organic carbon (TOC) = 38.78%, nitrogen (N) = 27.07%, phosphorous (P) = 58.42%, and potassium (K) = 28.64%. By adding 20 tons of CPS compost per hectare of the cornfield, the corn yield boosted 15 % compared to the control field. In addition, the water spinach grew and developed well in the medium of wastewater from the fish pond. Altogether, the results illustrate that catfish pond wastewater and sediment can act as organic fertilizers for crops meanwhile reduce environmental pollution from its reuse.
... Furthermore, P accumulation in farmland soil likely caused environmental pollution, and P was commonly regarded as the limiting factor driving eutrophication compared to nitrogen ( Li et al., 2017). Excessive application of P fertilizer is an important reason ( Powers et al., 2016). ...
Successive application of phosphorus (P) fertilizer under different cropping systems could result in remarkable changes in soil P fractions, accompanied by inducing soil P accumulation and increasing eutrophication risks. However, relatively little attention has been paid to annual changes in soil P fractions and P losses via runoff in drought-rewetting paddy fields. In the present study, we explored inter-annual variations in soil P speciation, availability and runoff P in a five-year field trial in a winter wheat and summer rice rotations system, and in different rice-growth stages. Four P fertilization treatments were applied, including P fertilization in both farming seasons (wheat and rice) (PR + W), application of P fertilizer only in rice-growing seasons (PR), application of P fertilizer only in wheat-growing seasons (PW), and no P fertilization (Pzero). Our results showed that P fertilization treatments (PW, PR, and PR + W) significantly altered the proportions of inorganic P (Pi) fractions, while no P fertilization in the wheat-growing seasons (Pzero, PR) significantly decreased NaHCO 3-Pi contents in the wheat-growing seasons and decreased NaHCO 3-Pi and NaOH-Pi concentrations in the rice-growing seasons (p < 0.05). Application of P fertilizer in the wheat-growing seasons treatments (PW, PR+W) maintained the stability of soil P fractions both in the wheat-and rice-growing seasons. Moreover, compared to the PR+W treatment, the PW treatment reduced total P (TP) losses from runoff. For inter-annual drought-rewetting variation in P speciation and availability, there was a significant correlation between Olsen-P and NaHCO 3-Pi and NaOH-Pi contents in the wheat-growing seasons, and Olsen-P was significantly correlated with NaHCO 3-Pi, NaOH-Pi, and HCl-P in the rice-growing seasons. Furthermore, we focused on the change in detailed rice-growth stages, and found aeration significantly increased NaHCO 3-Pi, NaOH-Pi, NaOH-Po and HCl-P contents, and there was a significant correlation between soil Olsen-P and the P fractions in the A-aeration growth stage in rice, which could be attributed to the short-term drought-rewetting cycle facilitating the release of soil P. The present study revealed changes in soil P speciation and availability in a drought-rewetting cycle in paddy soils, and indicated the optimized agricultural P management strategies had the potential to reduce environmental risks.
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As a typical pollutant, methylene blue poses a serious threat to the environment and human health. Oily sludge pyrolysis residue loaded with metal oxides could be used to prepare composite materials, which is not only an effective way to treat oily sludge, but also a possible method to treat methylene blue pollutants. In this paper, composite materials (AC-CuO, AC-ZnO, and AC-TiO2) were prepared by oily sludge pyrolysis residue-loaded CuO, ZnO, and TiO2 directly, and characterized by XRD, SEM, EDS, BET, FT-IR, and XPS, and it was shown that the metal oxides were successfully supported on the pyrolysis residue. Then, the composite materials were applied to the removal of methylene blue solution. The removal effect of composite materials on methylene blue with respect to the impregnation time, impregnation ratio and dosage, and the contact time and number of regenerations were investigated, and the removal parameters were optimized by response surface methodology. The removal process for methylene blue was described by applying Lagergren, McKay, Langmuir isotherm, Freundlish isotherm and intraparticle diffusion models. According to the response surface methodology and the main factors affecting the removal effect of methylene blue, the results indicate that the removal effect of 5 mg/L methylene blue could reach 95.28%, 94.95%, and 96.96%, respectively, and the corresponding removal capacities were 4.76, 4.75, and 4.85 mg/g. In addition, kinetic studies showed that the removal process of methylene blue was mainly constituted by chemical adsorption. The intraparticle diffusion showed that the removal of methylene blue may be controlled by both liquid film diffusion and intraparticle diffusion. The isotherms showed that the adsorption sites of composites for methylene blue were uniformly distributed and had the same affinity. Furthermore, regeneration experiments showed that the composite materials were stable and had relatively reusability.
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In the current study, water from Chuho springs used as the main water source in Kisoro municipality, Uganda were assessed for their suitability as drinking water. The temperature, turbidity, conductivity, total dissolved solids, dissolved oxygen, biological oxygen demand, total hardness, total alkalinity, calcium, magnesium, phosphates, iron, copper, arsenic, chlorides and the fluoride content of the water samples were determined. Not all the parameters met World Health Organizations’ guidelines for drinking water. Temperature, dissolved oxygen and fluorides were outside the recommended limits of 15 ℃, 10-12 mg/L and 1.5 mg/L, respectively. Further studies should assess the microbiological and sanitary profile of the springs.
Surface water quality is currently matter of serious concern in developing countries, due to growing populations, rapid industrialization, urbanization and agricultural modernization. Since contaminants are primarily related to anthropogenic activities, pollution by heavy metals in surface water bodies
Water forms an essential resource for life on earth since all living things on earth depend on water for life activities. However, with the increase in the human population which is coupled with intense urbanization and agricultural activities, global water pollution has increased over the past decades. In China, agricultural activities mainly in the planting fields have been listed as the main source of surface water and groundwater pollution. This review focuses on the major factors that influence pollution from planting fields in China mainly as a result of farming activities such as flood irrigation, excessive application of fertilizers and pesticides and poor management practices. At present, good results have achieved by adopting soil fertilization test formula, biodegradable pesticides, proper irrigation, and agroforestry interventions. In the future, pollution from planting fields as a non‐point source of water pollution can be improved and resolved by perfect nutrient management, best management practices, organic amendments, restoring water environment and intelligent assessment management. This article is protected by copyright. All rights reserved
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Eutrophication is expanding worldwide, but its implication for production and bioaccumulation of neurotoxic monomethylmercury (MeHg) is unknown. We developed a mercury (Hg) biogeochemical model for the Baltic Sea and used it to investigate the impact of eutrophication on phytoplankton MeHg concentrations. For model evaluation we measured total methylated Hg (MeHgT) in the Baltic Sea and found low concentrations (39±16 fM) above the halocline and high concentrations in anoxic waters (1249±369 fM). To close the Baltic Sea MeHgT budget we inferred an average normoxic water column MeHg production rate of 2×10⁻⁴ d⁻¹. We used the model to compare Baltic Sea’s present-day (2005-2014) eutrophic state to an oligo/mesotrophic scenario. Eutrophication increases primary production and export of organic matter and associated Hg to the sediment effectively removing Hg from the active biogeochemical cycle; this results in a 27% lower present-day water column Hg reservoir. However, increase in organic matter production and remineralization stimulates microbial Hg methylation resulting in a seasonal increase in both water and phytoplankton MeHg reservoirs above the halocline. Previous studies of systems dominated by external MeHg sources or benthic production found eutrophication to decrease MeHg levels in plankton. This Baltic Sea study shows that in systems with MeHg production in the normoxic water column eutrophication can increase phytoplankton MeHg content.
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Due to climate change impacts and the resulting sea-level rise, saline waters have been found further inland in tropical riverine estuaries such as the Godineau wetland, Trinidad. The saline water intrusion could constrain mangrove vegetation distribution. We investigated the surface water quality of two river channels (2 km and 6 km), emanating from a tropical wetland and from forest/agriculture at high-tide, respectively. Using a novel boat-mounted geophysical approach, spatially exhaustive river/estuarine salinity data was collected. Water quality parameters-salinity, pH and dissolved oxygen (DO)-were compared with vegetation surveyed along the course of the rivers to determine relationships between plant zonation and water quality. Our findings showed similar trends for salinity and apparent electrical conductivity, which were higher in the 2 km channel (27.10 to 31.80 dS/m) than in the 6 km channel (17.80 to 27.10 dS/m), while pH and DO levels were lower in the 2 km channel than in the 6 km channel due to higher levels of decomposition in the stagnant shorter channel. Red mangrove (Rhizophora mangle) was found in areas with little oxygen, high salinities and high acidity, making it more adaptable to conditions resulting from saline intrusion. Therefore, to replace the mangrove that has been lost due to die-off, the red mangrove maybe used in viable restoration efforts for the protection of inland areas from floods, as well as to provide ecosystem goods and services. © 2016, South African Water Research Commission. All rights reserved.
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Hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) tend to persist in the environment for long periods of time. The concentration and distribution of HCHs and DDTs were investigated in surface sediments of Yongdingxinhe wetland and Binhai wetland by gas chromatography-mass spectrometer (GC-MS). All isomers of HCHs and DDTs were detected in all of the samples. The concentrations of total HCHs (ΣHCHs) in two wetland sediments ranged from 69.81 to 379.28 ng · g (-1), with a mean value of 224.55 ng · g (-1). The concentrations of total DDTs (ΣDDTs) ranged from 98.32 to 129.10 ng · g (-1), with a mean value of 113.71 ng · g (-1). The results of an ecological risk assessment demonstrated that there was high-risk ecological effect of organochlorine pesticides (OCPs) on the estuary wetlands. Lindane and technical DDTs were found to be the main sources of OCPs.
Urban lakes in China, particularly those with relatively small surface areas and closed watersheds, have suffered from severe eutrophication over the past few years. To investigate the causes and to examine the underlying mechanisms, a two-dimensional uncertainty eutrophication model was developed. The model reflected the interactions between nutrients, phytoplankton and zooplankton. Moreover, it can be utilized to describe seasonal and regional water quality changes. The two-dimensional hydraulic model was set up using Navier-Stokes equations and was calculated by applying the finite volume method. The Bayesian method was employed to calibrate the model parameters and obtain the parameter posterior distribution. The two-dimensional hydraulic information and the parameter posterior distribution were utilized to calculate a two-dimensional uncertainty eutrophication model, for which the 95% confidence interval (uncertainty bounds which can provide the trend and range for water quality changes) and mean value of every water quality index (nitrate, ammonia, phosphate, Chl. a and dissolved oxygen) were simulated. Comparisons between the model simulations and the field data indicated that the models were able to calculate the hydrodynamic information and the eutrophication dynamics with reasonable accuracy (all the relative errors lower than 11%). The simulated concentrations of water quality indexes (nitrate, ammonia, phosphate and Chl. a) in the vicinity of the lake were higher than that in the middle of the lake during the simulation period, indicating that the nutrient load of the rainwater runoff had significant impacts on algal blooms and water quality. Therefore, the urban lake was vulnerable to the influence of rainwater runoff. To reduce the eutrophication risk, rainwater runoff needs to be controlled. Two-dimensional uncertainty eutrophication models, such as those used in this study, can provide a powerful management tool that will continue to improve prediction reliability.
Insufficient understanding of the hydrogeochemistry of aquifers makes it necessary to conduct a preliminary water quality assessment in the southern region of Ordos Basin, an arid area in the world. In this paper, the major ions of groundwater have been studied aiming at evaluating the hydrogeochemical processes that probably affect the groundwater quality using 150 samples collected in 2015. The two prevalent hydrochemical facies, HCO3Mg·Na·Ca and HCO3Mg·Ca·Na type water, have been identified based on the hydrochemical analysis from Piper trilinear diagram. Compositional relations have been used to assess the origin of solutes and confirm the predominant hydrogeochemical processes responsible for the various ions in the groundwater. The results show that the ions are derived from leaching effect, evaporation and condensation, cation exchange, mixing effect and human activities. Finally groundwater quality was assessed with single factor and set pair methods, the results indicate that groundwater quality in the study region is generally poor in terms of standard of national groundwater quality. The results obtained in this study will be useful to understand the groundwater quality status for effective management and utilization of the groundwater resource.
The problem of eutrophication, and the subsequent reduction in the utility value of water bodies, is a worldwide problem. This book addresses the aspects of the eutrophication issue that can have practical applications for water quality management. Chapters address the following topics: principles of energy and materials balances that determine eutrophication levels; determining the status of a water body; predicting changes in water quality; causes and effects of eutrophication; and the various methods available for the rehabilitation of eutrophicated water bodies. Potential for legislative applications to water management are considered. The societal benefits and the future potential for water rehabilitation schemes are evaluated. This book is an English edition of a book originally published in German. -N.Davey
Water quality analysis and assessment of national nature reserve in Ruoergai wetland were studied using a method of single-factor assessment index to provide scientific guide for the protection of water quality in Ruoergai Nature Reserve. The results indicated that the determining values of more than 80% of analysis item reached the quality assessment standard of the first-class surface water, there was no dangers to the organism of the reserve although that of a little of items exceeded standard value. The concentration of Fe 2+ and pH value were higher for the natural factor, the value of COD Cr, NH 3-N and oil exceeded standard value, eutrophication and organic pollution of the lake water were serious because of the interaction of natural and anthropogenic factor. Some countermeasures for protection of water quality were put forward such as (a) to decrease the drain amount of life sewage and dispose sewage water; (b) to dredge the inlet and outlet of lake for water turnover cycle in Ruoergai National Nature Reserve.