Abstract
Water quality safety is the key factor to maintain the ecosystem service functions of lakes. Field investigations and statistical analyses were carried out to study the water quality of a large, agriculture-stressed lakes (e.g., Chagan Lake) in Northeast China. The hydro-chemical properties of the Chagan Lake are HCO3·CO3-Na. Nutrient (N and P) and non-nutrient (pH and F−) were found to be the major factors that threaten water quality safety of the lake. The concentration of total nitrogen (TN) and total phosphorus (TP) was found to vary seasonally and at different locations. The overall lake water had mean TN and TP values of 2.19 mg/L and 0.49 mg/L, respectively, in summer. TN was the major factor for water quality deterioration in the western region of the lake, while TP was the principal factor in the other regions, as determined by a principal component analysis (PCA). Fluoride (F−) concentration in the lake water were related to the values of total dissolved solid (TDS), pH, and electrical conductivity (EC). In addition, eutrophication is a fundamental index that has been affecting the ecological evaluation of water quality. The results showed that trophic level index (TLI), trophic state index (TSI), and eutrophication index (EI) were evaluated to quantify the risk of eutrophication. However, TLI and TSI can better describe the purification effect of the wetland. These indices showed that the lake water was hyper-eutrophic in summer, with TLI, TSI, and EI values of 60.1, 63.0, and 66.6, respectively. Disparities in water quality were observed among whole areas of the lake. Overall, this study revealed that controlling agriculture drainage is crucial for lake water quality management. The study generated critical data for making water quality management plans to control the risk.
Highlights
Eutrophication has caused a series of water quality problems for freshwater and marine ecosystems, which are caused by the response of natural waters to an excessive input of nutrients [1,2,3]
chemical oxygen demand (CODmn), Chl-a, and BOD5 were strongly positively correlated with total phosphorus (TP) and total nitrogen (TN) (p < 0.01), which showed that the organic contaminants such as bait was the major pollution source [65]
Most lake eutrophication were affected by the precipitation and evaporation, while the major meteorological elements of the Chagan Lake were evaporation, which was different from low latitude lakes such as the Dianchi [37,66,67,68]
Summary
Eutrophication has caused a series of water quality problems for freshwater and marine ecosystems, which are caused by the response of natural waters to an excessive input of nutrients [1,2,3]. The effect of eutrophication on global warming and growing human populations act in concert with increasing nutrients, especially in recent decades [4,5,6,7,8]. Systematic water quality monitoring, risk assessment, and preventative measures are important tools adopted by environmental protection agencies to tackle the problem of lake eutrophication. Studies of eutrophication have evolved from problem definitions to the identification of causes, and on to water quality management. Human activity had accelerated the eutrophication process
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