Water Environmental Quality Standards Research Articles

Surface water quality assessment based on the Integrated Water Quality Index in the Maozhou River basin, Guangdong, China

Rivers are a vital component of both urban and rural aquatic ecosystems, and the rapidly increasing pollution in rivers severely threatens the security of these ecosystems. In this study, the surface water quality in the Maozhou River basin, Guangdong Province, China, was assessed from 2018 to 2020 using multivariate statistical techniques and the Integrated Water Quality Index (IWQI). In addition, spatial trends in surface water quality were studied using a geographic information system. The results indicated that the water quality in 82.17% of the studied section met the Class V standard for surface water quality, with IWQI values ranging from 12.157 to 3.650. The surface water quality was clustered into eight groups and further divided into unsuitable (low quality) and suitable (acceptable quality) according to standard surface water quality thresholds (China in Environmental quality standards for surface water, 2002). Four groups (G1, G2, G3, and G4) were classified as unsuitable, because they fell short of the Class V standard for surface water quality. In these groups, industrial sewage, endogenous pollution, domestic sewage, and rainfall runoff, were the primary sources of pollution, and the main background pollutants for the water quality target of the functional zones were COD, NH3-N, TP, and LAS. The other four groups were classified as suitable. In these groups, endogenous pollution and rainfall runoff were the primary sources of pollution, and the main background pollutants for the water quality target of the functional zones were NH3-N and TP. Among them, NH3-N and LAS were recognized as responsive and sensitive to the surface water quality and spatio-temporal variability. Owing to pollution treatment and management measures undertaken by the Chinese government, the black-odorous water in the Maozhou River basin has disappeared, and the water quality in the Maozhou River basin has been maintained at the “medium and good” level. However, the surface water quality in the estuary region and the southwest tributary in the basin requires further improvement. This calls for further efforts to improve surface water quality and to properly deal with various sources of pollution in the watershed. This combined method has proved to be effective for surface water quality evaluation and management at river or basin scales. The results of this work are expected to provide a scientific foundation for aquatic ecosystem management and planning.

Changes in the footprint of grey water from 2005 to 2017 in Fuzhou City

Based on the concept of grey water footprint, this study quantified the pollutants generated by agricultural, industrial and tertiary industries in Fuzhou City from 2005 to 2017 using the diluted water demands. The results showed: 1) the mean agricultural grey water footprint of Fuzhou City was 15.88×108 m3/a at the study period, which is about 16.69% of the water consumption; 2) among three sectors, grey water footprint in the living sectorsis the largest, and agricultural grey water footprint is the smallest; 3) the grey water footprint of Fuzhou City shows a declining trend from 2005 to 2017, with the agricultural, industrial and living sectors decreasing by 24.92%, 60.78% and 17.11%, respectively; 4) the footprint of Fuzhou City’s grey water showed a downward trend, while the water quality in urban areas also showed a downward trend. The footprint of grey water is greater than the amount of water resources, implying the limited water resources in Fuzhou City can not fully dilute the pollutants for the environmental water quality standards.

Research on Hazardous Waste Removal Management: Identification of the Hazardous Characteristics of Fluid Catalytic Cracking Spent Catalysts.

Fluid catalytic cracking (FCC) spent catalysts are the most common catalysts produced by the petroleum refining industry in China. The National Hazardous Waste List (2016 edition) lists FCC spent catalysts as hazardous waste, but this listing is very controversial in the petroleum refining industry. This study collects samples of waste catalysts from seven domestic catalytic cracking units without antimony-based passivation agents and identifies their hazardous characteristics. FCC spent catalysts do not have the characteristics of flammability, corrosiveness, reactivity, or infectivity. Based on our analysis of the components and production process of the FCC spent catalysts, we focused on the hazardous characteristic of toxicity. Our results show that the leaching toxicity of the heavy metal pollutants nickel, copper, lead, and zinc in the FCC spent catalyst samples did not exceed the hazardous waste identification standards. Assuming that the standards for antimony and vanadium leachate are 100 times higher than that of the surface water and groundwater environmental quality standards, the leaching concentration of antimony and vanadium in the FCC spent catalyst of the G set of installations exceeds the standard, which may affect the environmental quality of surface water or groundwater. The quantities of toxic substances in all spent FCC catalysts, except those from G2, does not exceed the standard. The acute toxicity of FCC spent catalysts in all installations does not exceed the standard. Therefore, we exclude “waste catalysts from catalytic cracking units without antimony-based passivating agent passivation nickel agent” from the “National Hazardous Waste List.”

Pollution Characteristics and Health Risk Assessment of Heavy Metals in the Water of Lijiang River Basin

In order to clarify the pollution levels of heavy metals in the drinking water sources of the Lijiang River Basin, surface water samples were collected from 62 sites throughout the Lijiang River during May 2019. Heavy metals, including As, Cd, Cr, Mn, Cu, Zn, Hg, Co, and Sb, in the water samples were analysed. Health risk assessments associated with these nine heavy metals were conducted using the health risk assessment model from the US EPA. The results indicated that the order of the average concentrations of heavy metals in the water samples were Mn > Zn > As > Cr > Cu > Sb > Co > Cd > Hg. No heavy metals exceeded the limit values of the drinking water health standards in China (GB 5749-2006), and the concentrations were lower than the limitations of Grade Ⅰ level in the environmental quality standards for surface water (GB 3838-2002). According to the spatial distribution, the high contents areas of As, Cr, Zn, and Sb were predominantly distributed downstream of the Lijiang River, while the high contents areas of Cd, Cu, Hg, Co, and Mn were mostly distributed in the upper reaches. Multivariate analysis indicated that Cd, Mn, Cu, and Co were primarily from agricultural production; Cr, Zn, and Sb were mainly from tourism transportation; As was predominantly from the weathering of rock parent material and soil erosion; Hg was mainly from the improper disposal of domestic garbage and atmospheric deposition. The results of the health risk assessment indicated that children were more susceptible to the threat of heavy metal pollution than adults, and the average annual risk of carcinogenic heavy metals to human health through drinking water ingestion were higher than those of non-carcinogenic metals. The maximum personal average annual health risk of Cr was higher than the maximum allowance levels recommended by the International Commission on Radiological Protection (5×10-5 a-1). The average annual risk of non-carcinogenic heavy metals (10-14-10-9 a-1) decreased in the order of Co > Cu > Hg > Zn > Sb > Mn, which were far below the maximum allowance levels recommended by the ICRP.

Impact assessment of water diversion project on urban aquatic ecological environment

Water diversion project (WDP) plays an increasingly important role in improving the water quality of urban rivers along the Yangtze Delta megalopolis of China. However, their effects on the water ecological environment has generated extensive debates. Water quality variables and phytoplankton community dynamics were tracked and monitored during the summer–winter water diversions to explore the comprehensive effects of WDP on the urban aquatic ecological environment. The multi-index comprehensive evaluation model (MCEM) was adopted for further quantitative assessment, together with a newly proposed progressive degree calculation model (PDCM), which broke the limitations of the traditional ways using Markov chains. The grade evaluation was based on the Environmental Quality Standards for Surface Water (GB 3838–2002) in China. The comprehensive water quality evaluated by MCEM was improved with the largest improvement of two grades after WDP in summer, which on the contrary was worsened because of water transfers in winter by a maximum decrement of one grade. The PDCM evaluation on water quality index indicated that WDP has improved the water quality to some extent but without grade changes. Also, the proportion of Cyanobacteria and Chlorophyta decreased in the phytoplankton community of the three rivers after WDP, whereas the proportion of Bacillariophyta increased, indicating that the community structure was more inclined to the Yangtze River. The comprehensive water pollution situation evaluated by MCEM was improved with the largest improvement from middle pollution to lower pollution (one grade) because of water transfers. The changes in aquatic biological indexes evaluated by PDCM were more obvious than those of water quality indexes, which were improved by one grade.

Estimation of Polycyclic Aromatic Hydrocarbons Pollution in Mediterranean Sea from Volturno River, Southern Italy: Distribution, Risk Assessment and Loads.

This study reports the data on the contamination caused by polycyclic aromatic hydrocarbons (PAHs) drained from the Volturno River. The seasonal and spatial distribution of PAHs in water and sediment samples was assessed. The 16 PAHs were determined in the water dissolved phase (DP), suspended particulate matter (SPM), and sediments. A multidimensional statistical approach was used to identify three pollution composite indicators. Contaminant discharges of PAHs into the sea were calculated in about 3158.2 kg/year. Total concentrations of PAHs varied in ranges 434.8 to 872.1 ng g−1 and 256.7 to 1686.3 ng L−1 in sediment samples and in water (DP + SPM), respectively. The statistical results indicated that the PAHs mainly had a pyrolytic source. Considering the sediment quality guidelines (SQGs), the water environmental quality standards (USEPA EQS), and risk quotient (RQ), the Volturno River would be considered as an area in which the environmental integrity is possibly at risk.

Community Structure, Function, and Influencing Factors of Planktonic Fungi in the Danjiangkou Reservoir

Planktonic fungi are important components of aquatic ecosystems, and analyses of their community composition and function have far-reaching significance for the ecological management and maintenance of the Danjiangkou reservoir. The composition and function of the planktonic fungal community in the surface water layer of the Danjiangkou Reservoir in October 2019 was investigated using Illumina MiSeq sequencing combined with FUNGuild analyses. According to the results, the reservoir community is primarily composed of 6 phyla 213 genera, with Ascomycota and Basidiomycota being the dominant phyla. The water quality monitoring results for the Danjiangkou Reservoir met the Grade Ⅰ or Ⅱ water quality standards for the Environmental Quality Standards for Surface Water (GB 38382-2002). A redundancy analysis (RDA) of the planktonic fungal community and environmental factors showed that TN, TP, T, ORP, and TLI are important factors influencing the distribution of planktonic fungi. The Spearman correlation analysis showed that Alternaria, Cladosporium, Penicillium, Lodderomyces, and Acremonium were significantly correlated with physical and chemical water quality parameters. FUNGuild was used to predict the nutritional and functional groups of planktonic fungi, and the results showed that pathotrophs, saprotrophs, and pathotroph-saprotrophs were the major components. The pathotroph composition analysis showed that the proportions of plant pathogens and animal pathogens in the Heijizui samples were significantly higher than those observed in the other monitoring sites. The community composition, function, and influencing factors of the planktonic fungi community in the Danjiangkou Reservoir were investigated and indicated that it is potentially at ecological risk and more attention needs to be paid to planktonic fungi in the biological monitoring of water quality.

Impact of the Mining Activity on the Water Quality in Peru Applying the Fuzzy Logic with the Grey Clustering Method

Mining activity in the department of Junín, Peru, is intense, due to the great existing mining-metallic potential that exists in the place, the Yauli and Andaychagua rivers, located in the Yauli Province, belonging to Junín, receive a large volume of discharges causing deterioration in the quality of the water of these rivers. To evaluate this quality in an integral way, fuzzy logic will be applied with the Grey Clustering methodology, defining the central point triangular whitening weight functions (CTWF), having as grey classes the Environmental Quality Standards for water (ECA-Water), Category 3, which were modified for research purposes. Four monitoring points were evaluated, both upstream (point PY-01) and downstream (PY-02) of the Yauli River; as upstream (PA-01) and downstream (PA-02) of the Andaychagua river. From the analysis it was determined that the water quality in PY-01 is 0.7302, 0.8795 in the dry season and 0.5980 in the wet season; in PY-02, 0.5448, 0.6448 in dry season and 0.5628 in wet season were obtained. At point PA-01 it is 0.8213, 0.8691 in dry season and 0.7902 in wet season; In PA-02, 0.8385, 0.8827 in the dry season and 0.8118 in the wet season were obtained, concluding that there is good water quality, decreasing in wet seasons, this due to the influence of the rains in the contact waters. The research provides an integration of the parameters that are considered in the ECA-Water with other international standards allowing to determine a more precise evaluation of the quality status of the Yauli and Andaychagua rivers after receiving the effluents generated by the mining activity, benefiting the relevant authorities for decision making and providing a methodology that improves the analysis of the results obtained by the specific parameters that are evaluated in the environmental monitoring.

Performance of innovative granular sponge city growing media based on field monitoring

The growing media in the planting layer of sponge city facilities has an important influence on stormwater runoff control, pollutant removal and plant growth. This study consists of field tests that include the continuous monitoring to evaluate the performance of runoff control and pollutant removal of the innovative granular sponge city growing media during wet season. The results show that the lowest average permeability of innovative granular sponge city growing mediais 500 mm·h^-1, and the pollutant removal effect is good, the removal rate of solid suspended solids is more than 80%, and the main effluent quality indexes (total nitrogen, TN; total phosphorus, TP; ammonia, NH₃-N; chemical oxygen demand, COD) sampled from the outflow of the testing bioretention cells show that the water quality of discharged runoff meets the Class-Ⅲ indices of the Environmental quality standards for surface water (GB 3838—2002). Combination of local landscape plants such as evergreen shrubs, deciduous shrubs, perennial ground cover and other native plants in South China all grow well during the field tests. The overall life-cycle cost of this new type of growing media also needs to be further verified by different projects in different climate regions, generally it is 1/3-3/4 of that of traditional media. In summary, compared with the traditional sponge city media, the innovative granular sponge city growing media has better permeability and pollutantremoval effect, low cost, and convenient operationand maintenancein the later stage.It can be widely applied in areas without heavy metal pollution, and is expected to replace the traditional media to a certain extent.

Method for lake eutrophication levels evaluation: TOPSIS-MCS

Monte Carlo simulation (MCS) is applied in the engineering with great fuzziness and uncertainty. Technique for order preference by similarity to an ideal solution (TOPSIS) method is used to deal with multi-criteria decision-making issue. Membership function is used to determine the membership degree of evaluated index. This paper presents the method for lake eutrophication level evaluation. The developed approach merges MCS method, TOPSIS method and membership function. The evaluated results are consistent with real eutrophication level in Lake Erhai, China. Global sensitivity analysis (GSA) is conducted. Results show that potassium permanganate index (CODMn) displays the highest negative correlation with the evaluated results and Secchi disc (SD) performs the highest positive correlation under different errors in measured data. The novelty of this work are: (1) the application of TOPSIS considers Surface water environmental quality standards and measured data. Besides, the Monte Carlo simulation method is applied to generate a normal distributed dataset to overcome the errors caused by human and equipment in data collection. The approach is utilized in the article, titled “Approach based on TOPSIS and Monte Carlo simulation methods to evaluate lake eutrophication levels” (Lin et al., 2020) [1].•Developed approach merges TOPSIS and MCS method.•It can increase the reliability of evaluated result.

The simulation of water quality control of Fengping section in Mangshi River

The assessment of water quality is mainly based on Environmental Quality Standards for Surface Water (GB3838-2002), which divided surface water into five classes (Class I to Class V) according to its purpose for use and protection target. In April 2015, the State Council issued an Action Plan for the Prevention and Control of Water Pollution, which is a law formulated to effectively increase the prevention and control of water pollution and ensure national water safety. In 2016, the Yunnan Provincial People’s Government and the Dehong Prefecture People’s Government successively proposed work plans for the prevention and control of water pollution, requiring the Fengping Section (State Control) in Mangshi River to reach Class III of surface water by 2020. But the current water quality fluctuates between Class III and V. Based on the current status of water quality and pollution sources, the paper uses HD (hydrodynamic model) and AD (hydrodynamics advection diffusion model) in MIKE 21 FM model to establish the two-dimensional water quality model to simulate the distribution characteristic of different water quality parameters, which are Biochemical Oxygen Demand (BOD5), Total Phosphorus (TP), Ammonium Nitrogen (NH3-N). The conclusion is that reduction targets of BOD5, TP and NH3-N are namely 40%, 30% and 10% to ensure water quality, which guides the formulation of pollutant emission reduction plans more scientifically.

Seasonal variation of heavy metals in surface water of the Ananea river contaminated by artisanal mining, Peru

The objective of this research work is to evaluate the effects of mining tailings leak on the water quality of the Ananea river, which contain heavy metals. For which techniques such as taking surface water samples were applied at five strategic points, programming two sampling campaigns; one in the rainy season (March) and the other in the dry season (June). Heavy metal concentrations were determined by the EPA METHOD 200.7 Atomic Emission Spectrometry method; The results show that the highest concentrations were recorded at the M-1 sampling point for both the dry season and the rainy season. These concentrations are well above the peruvian Environmental Quality Standards (WQS) for water. In the same way, point M-1 was identified as the most critical and vulnerable to contamination in the study area by heavy metals that are above WQS. Likewise, the survey technique was applied, for which a question sheet was prepared for the surrounding population according to the activities carried out in this part of the basin, obtaining data to determine the effects caused by mining pollution on the surrounding life. In conclusion, the quality of the waters of the Ananea River are contaminated by the presence of heavy metals and these have been causing negative effects to all the surrounding life found in the study area.

Study on Heavy Metal Contamination in High Water Table Coal Mining Subsidence Ponds That Use Different Resource Reutilization Methods

Heavy metals accumulate in high water table coal mining subsidence ponds, resulting in heavy metal enrichment and destruction of the ecological environment. In this study, subsidence ponds with different resource reutilization methods were used as study subjects, and non-remediated subsidence ponds were collectively used as the control region to analyze the heavy metal distributions in water bodies, sediment, and vegetation. The results revealed the arsenic content in the water bodies slightly exceeded Class III of China’s Environmental Quality Standards for Surface Water. The lead content in water inlet vegetation of the control region and the Anguo wetland severely exceeded limits. Pearson’s correlation, PCA, and HCA analysis results indicated that the heavy metals at the study site could be divided into two categories: Category 1 is the most prevalent in aquaculture pond B and mainly originate from aquaculture. Category 2 predominates in control region D and mainly originates from atmospheric deposition, coal mining, and leaching. In general, the degree of heavy metal contamination in the Anguo wetland, aquaculture pond, and fishery–solar hybrid project regions is lower than that in the control region. Therefore, these models should be considered during resource reutilization of subsidence ponds based on the actual conditions.

Experimental study on the simultaneous nitrification and denitrification of limited aeration biofilm reactor

To improve the nitrogen removal effects of domestic sewage and reactive mode, the two-stage limited aeration biofilm reactor was used to carry out an experiment. The pollutants removal effects and influencing factors were analyzed. The results indicate: Under the condition that the 1st reaction chamber DO of 1.5∼2 mg/L, the 2nd reaction chamber DO of 1∼1.5 mg/L, HRT=5 h, and influent ρ(COD) = 147∼181 mg/L, ρ(NH4 +-N) = 35.1∼43.6 mg/L, ρ(TN) = 36.3∼44.1 mg/L, the maximal concentration of COD, NH4 +-N, and TN in the last effluent were 18.8 mg/L, 0.35 mg/L and 14.2 mg/L, with the mean removal rates of 91.1%, 99.5%, 66.6% and the SND ratio of 62.7% ∼ 68.9%. Under the condition of 4.17h≤HRT≤5h, the effluent concentration of COD, NH4 +-N met the Category III of environmental quality standards for surface water (GB3838-2002), and the effluent concentration of TN met the Class A discharge standard of pollutants for municipal wastewater treatment plant (GB18918-2002) with the SND ratio of 65.7%. Under the condition that the 1st reaction chamber DO of 1.5∼2 mg/L, the 2nd reaction chamber DO of 1∼1.5 mg/L, HRT=4.17 h, the SND effects can be improved by the means of additional sodium acetate in the 2nd reaction chamber. The TN removal rate and SND ratio were respectively 75.4% and 75.8% at the optimal dosage of 40 mg/L.

Three-dimensional water scarcity assessment by considering water quantity, water quality, and environmental flow requirements: Review and prospect

The increasing population, improving living standards, and expanding economic activities are responsible for rising water demands. In recent decades, the imbalance between water supply and demand has become increasingly prominent. Coupled with the unreasonable use of water resources, this has led to serious water scarcity problems that affect the sustainable development of modern society. Under this background, water scarcity has become an important environmental issue for our sustainable planet. Water scarcity is affected by regional water resource endowments and the ways in which water resources are developed and utilized by human beings. Quantity-induced water scarcity occurs when the quantity of water resources is insufficient. Meanwhile, pollution can cause water scarcity as the services provided by polluted water are not equivalent to that of clean water. Quality-induced water scarcity occurs when the pollutants exceed the environmental carrying capacity. Since Marlin Falkenmark first proposed the concept and assessment method of water scarcity in the 1980s, water scarcity assessment has developed for nearly 40 years. With the development of new theories, progress has been made, such as development of different approaches for assessing water scarcity, identification of influencing factors of water scarcity, revealing the formation mechanism, and exploring strategies to cope with water scarcity. As a result, water scarcity assessment has experienced an evolutionary pathway from a one-dimensional model emphasizing only quantity-induced water scarcity to a two-dimensional model (considering both quantity-induced and quality-induced water scarcity), toward a three-dimensional (3D) model (or 3D water scarcity theory) that considers water quantity, water quality, and environmental flows simultaneous. Based on a systematic review of water scarcity assessment in the literature, this study demonstrates the 3D water scarcity theory and elaborates on its basic concepts, principles, and core methods. The 3D water scarcity theory was first proposed by Chinese scholars and then accepted by international scholars. The quantity-induced water scarcity is assessed based on the ratio of water consumption to water availability, and the quality-induced water scarcity is quantified by comparing gray water footprint (the amount of water required to dilute pollutants in wastewater sufficiently to meet environmental water quality standards) with local available water resources. Environmental flow requirements are quantified based on the characteristics of climatic and hydrological conditions rather than the traditionally adopted simple approach by assuming that they are equal to 80% of water resources. Hence, the 3D water scarcity theory and assessment method can consider water quantity, water quality, and environmental flow requirements comprehensively. Finally, four main future research directions of water scarcity assessment are summarized: The further development and improvement of the theoretical framework of 3D water scarcity, applications of the assessment methods on multiple spatial scales, explicit consideration of the impacts of physical and virtual water flow, and mechanism of the evolution of water scarcity. 3D water scarcity is a key to achieving sustainable and harmonious development between humanity and water resources, and its assessment framework can break through the limitations of the traditional one- or two-dimensional models. Water scarcity theory provides methodological support for measuring the state of water resources on global, national, and regional scales, and it will help formulate appropriate water mitigation measures for integrated water resources management.

The study on optimal design of river monitoring network using modified approaching degree model: a case study of the Liaohe River, Northeast China.

This paper proposes a quantitative method to optimize the existing river monitoring network based on a modified approaching degree model, T test, and Euclidean distance. In this study, the Liaohe River located in Liaoning province, China, was taken as a research object. Samples were collected from 8 sampling sites throughout the monitoring network, and water quality parameters were analyzed every 2months from January 2009 to December 2010. The results show that the average concentrations of the ammonia nitrogen (NH4+-N) and chemical oxygen demand (COD) were beyond grade III of the Environmental Quality Standards for Surface Water of China (GB3838-2002), and they were the main water quality parameters. After optimization, the number of monitoring sections along the Liaohe River was reduced to five from the original eight, thus saving 37.5% of the monitoring cost; meanwhile, there is no significant difference between the un-optimized and optimized monitoring networks, and the optimized monitoring network remains to be able to perform as good as the original one. In addition, the total data attainment rate was improved greatly, and the duplicate setting degree of monitoring points decreased significantly compared with other optimal methods. The optimized monitoring network proves to be more efficient, reasonable, and economically feasible, so this quantitative method can help optimize the changing orderly river monitoring networks.

Investigating selection for antimicrobial resistance by non-antibiotic drugs (NADs)

A recent study screening over 1000 drugs has shown that non-antibiotic drugs (NADs), including human targeted drugs, have been shown to have antimicrobial effects on representative strains of human gut bacteria. NADs are present in both wastewater effluent and freshwater systems, where they may only be partially metabolised. Concentrations of antibiotics found in the environment have been shown to select for resistance in complex microbial communities, and it is thought that concentrations of NADs in the environment may also select for resistance. This project aims to determine if NADs select for antimicrobial resistance, by investigating effects in a complex bacterial community. Pharmaceuticals from 7 different drug classes have been screened for antimicrobial activity. The most potent compounds will be used in exposure experiments to identify any existing antimicrobial resistance genes that confer cross-resistance to both antibiotics and NADs using a metagenomics approach. In addition, changes in community composition will be investigated to determine if there is enrichment for opportunistic pathogens after exposure to NADs. This project ultimately aims to inform on environmental water quality standards and environmental risk assessment of wastewater treatment effluent in order to mitigate the growing problem of environmental antimicrobial resistance.

Understanding the risks from diffuse pollution on wetland eco-systems: The effectiveness of water quality classification schemes

Eco-environmental safety and health is an important concept for the protection of flora and fauna in the wetland eco-system. Identifying impacts of human activities on wetland ecology and risk factors of environmental decline have become significant components of habitat protection. In this study, the Qixing River wetland, one of the Ramsar Sites, was taken as the research area. Seven water quality indices, including dissolved oxygen (DO), chemical oxygen demand (COD), ammonia nitrogen (NH3−N), total phosphorus (TP), total nitrogen (TN), nitrates and nitrites were monitored at fifteen sampling locations. Entropy weight-set pair analysis, combined with discriminant analysis, was used to identify the most sensitive indicators for changes in water quality. Average concentrations for the indicators measured were: DO 7.24 (4.64–9.98) mg/L; COD 21.67 (5–50) mg/L; NH3-N 1.09 (0.41–2.15) mg/L; TP 0.18 (0.10–0.73) mg/L; TN 1.38 (0.76–2.17) mg/L, nitrite 0.016 (ND ~ 0.030) mg/L and nitrate concentration was 0.420 (0.315–0.613) mg/L. Water quality was found to be poorest at locations closer to sources of diffuse pollution such as agricultural land. In contrast, the more remote buffer zone and core zone of the wetland was characterized by improved indicators of water quality. The results of entropy weight-set pair analysis showed that the overall water quality grade of Qixing River wetland conforms to Class III of the “Environmental Quality Standards for Surface Water” of China (GB3838-2002). Discriminant analysis indicated that TP was the main contributory factor to reduced water quality classification while COD, ammonia nitrogen and total nitrogen were the key drivers of improving water quality grade and responsible for the Class III award. The prominence of these indicators is indicative of long-term use of fertilizers and pesticides in agricultural production. The more remote core area of the wetland was less affected by human activities, reflected in improved water quality results. The results showed that entropy weight-set pair analysis coupled with discriminant analysis adds value to widely used water environment quality indices and helps identify the main environmental factors driving water quality classification. In the case of the Qixing River wetland, there is clear potential to protect wetland eco-system safety by improving the water quality classification and reforming agronomic and land management practices.

Assessment of medium and small river health based on macroinvertebrates habitat suitability curves: a case study in a tributary of Yangtze River, China

Abstract The health of medium and small river ecosystems is threatened by increasing hydropower development and human activities. How to properly diagnose rivers has become a global concern. As a well-accepted theory, the aquatic organism density can be an indicator of river health. A new river health assessment method based on macroinvertebrates habitat suitability curves (M-HSC) was proposed. In this study, the health of Qiaobian River (QBR), a tributary of Yangtze River, China was evaluated by investigating the distribution of macroinvertebrates, chemical and physical parameters during winter 2018 (low flow season) and summer 2019 (high flow season). Based on habitat suitability of dominant macroinvertebrates, the key habitat factors were screened by canonical correspondence analysis (CCA) and Pearson correlation analysis. Suitability curves were determined by Generalized Additive Model (GAM). Ecosystem health comprehensive index method was used to evaluate the health status. The results show most suitable conditions for Corbicula fluminea containing chemical oxygen demand (CODMn) of 1.48 mg L−1, total nitrogen (TN) of 0.27 mg L−1, dissolved oxygen (DO) of 11.17 mg L−1, pH of 8.42, turbidity of 1.76 NTU, and water depth (Dep) of 0.35 m. The health status of QBR is spatially heterogeneous with the apparently better upstream than the downstream. In general, 25, 12.5, 12.5% of the samples were classified as nature, health and sub-health status, respectively and the rest 50% were lower than sub-health. The results are consistent with the environmental quality standards for surface water in China (GB3838-2002), suggesting the applicability of macroinvertebrates habitat suitability for evaluating river health. By minimizing the temporal and spatial limitations of comprehensive evaluation method and indicator species method, this study, for the first time, used macroinvertebrates habitat suitability curves to assess the health of medium and small rivers. The study will provide new insights for future river health assessments.

The fuzzy comprehensive evaluation (FCE) and the principal component analysis (PCA) model simulation and its applications in water quality assessment of Nansi Lake Basin, China

The Fuzzy Comprehensive Evaluation (FCE) and the Principal Component Analysis (PCA) were simulated to assess water quality of the Nansi Lake Basin, China. The membership functions were established via the Nor-Half Sinusoidal Distribution Method, and the weight was calculated via the Exceeding Standard Multiple Method. To enhance the efficiency of extracting principal pollutant, the eigenequation was solved through the Jacobi Method, and the principal components were extracted based on eigenvalue, contribution ratio, accumulating contribution ratio, principal component loading and score. Water quality classification based on “National Surface Water Environmental Quality Standards of China (GB3838-2002) was used to assess the water quality. Considering the difference of the temporal and spatial distribution in average, water quality of Level I was 28.9%, 28.1%, 25.1%, 25.6%, respectively in spring, summer, autumn, and winter, which suggested that water quality in spring and summer was better than in autumn and winter. The order of water quality was Zhaoyang Lake (Level I) > Nanyang Lake (Level I) > Dushan Lake (Level III) > Weishan Lake (Level III and IV). There were four extracted principal components that can replace the fourteen pollutant indexes for assessing water quality. According to the annual mean data of the 1st principal components, the most important pollutions were heavy metals, including As (0.933), Hg (0.931), Cd (0.929), Cr(VI) (0.926), Pb (0.925), and Cu (0.534). It is proved that the combined FCE-PCA model could provide valuable information in the water quality assessment for the Nansi Lake Basin.