Research Status of Water Quality Criteria and Standards and Analysis on the Transformation Methods

Under the vision of development for the new era,China has entered a stage of high-quality economic development and an important window period in which we have the conditions and ability to address the prominent issue of economic development and ecological protection in a coordinated way.However,all kinds of environmental benchmark values in China are lacking and need to be constantly supplemented and improved.Therefore,exploring and putting forward a simple and efficient method for the transformation of environmental criteria into environmental standards is an important basis for the rapid establishment of relevant environmental criteria system and the effective promotion of the development of environmental standards system towards a scientific and reasonable direction.In this paper,the water environment is taken as the research object.By analyzing the research progress of environmental criteria and standards at home and abroad,and the foreign method of transforming environmental criteria into environmental standards,combined with the problems faced in the process of transforming environmental criteria into environmental standards in China,an effective method to transform China's environmental criteria into environmental standards is analyzed.After analysis and comparison,it is found that the pollution reduction accounting method could achieve their simple and efficient conversion.Under the premise of obtaining environmental criteria for certain pollutants,environmental criteria for certain pollutants could be obtained by distributing pollutants reduction costs,and accounting economic benefits after reaching standard,thus obtaining the environmental standard of this type of pollutant,which provides reference to determine the environmental standard limits of such pollutants.

Derivation of water quality criteria for representative water-body pollutants in China

In this study, toxicological data for zinc （Zn）, cadmium （Cd）, hexavalent chromium （Cr （VI））, benzene, and nitrobenzene were collected from various databases and publications, screened and then constructed into species sensitivity distribution （SSD） curves. Then water quality criteria （WQC） were derived for protection of the freshwater aquatic life in China against five representative pollutants. The values derived in this study were compared with those issued by the US Environmental Protection Agency and the Chinese national environmental standard for surface water to identify factors underlying the differences. The results showed that the SSD curves for the five pollutants differed significantly, with the examined aquatic species being gen- erally more sensitive to Zn, Cd, and Cr （VI） than benzene and nitrobenzene. The acute WQC were： 48.43 μg L-1 for Zn, 0.4218 μg L-1 for Cd, 45.79μg L-1 for Cr （VI）, 2651 μg L-1 for benzene, and 1426 μg L-1 for nitrobenzene. The chronic WQC were： 20.01μg L-1 for Zn, 0.2428 μg L-j for Cd, 14.22 μg L-1 for Cr （VI）, 530.2 μg L J for benzene, and 286.2 μg L-1 for nitroben- zene. The results of this comparative study of representative pollutants may offer guideline values for future WQC studies for China.

Water quality criteria research and progress

Water quality criteria (WQC) are threshold limits for pollutants or other hazard factors in the ambient water environment, which are based on scientific experiments and extrapolations. Until now, there is limited information available regarding the study of water quality criteria in China. It is imperative to launch national-level systematic WQC studies that focus on the regional characteristics of China and provide scientific support for the enactment or revision of water quality standards and environmental management. This article reviews the concept of WQC and discusses the methodology and global progress of WQC research. The article also summarizes the key scientific issues in WQC research, including species sensitivity distribution, toxicological endpoint selection, and models selection. Furthermore, we can adopt the derivation method used in the USA and divide WQC into acute and chronic criteria. Finally, considering the current status of WQC research in China, we point out important directions for future national studies, including the selection of native species and the comprehensive use of models.

Human health ambient water quality criteria for 13 heavy metals and health risk assessment in Taihu Lake

Heavy metals are widely concerning because of their toxicity,persistence,non-degradation and bioaccumulation ability.Iluman health ambient water quality criteria(AWQC)are specific levels of chemicals that can occur in water without harming human health.At present,most countries do not consider the effects of aquatic vegetables in deriving human health AWQC.Therefore,the intake of aquatic vegetables(Brasenia schreberi)was added to the derivation of human health AWQC and a health risk assessment for 13 heavy metals in Taihu Lake.The human health AWQC(consumption of water,fish and aquatic vegetables)values of 13 heavy metals ranged from 0.04(Cd)to 710.87μg/L(Sn),and the intake of B.schreberi had a very significant effect on the human health AWQC for Cu,with a more than 62-fold difference.The hazard quotients of As(2.8),Cd(1.6),Cr(1.4)and Cu(4.86)were higher than the safe level(HQ=1),indicating that As,Cd,Cr and Cu in Taihu Lake posed a significant health risk.Sensitivity analysis showed that the contribution rate of B.schreberi intake to the human health risk from Cu was 91.6%,and all results indicated that the risk of Cu in B.schreberi to human health should be of particular concern.This study adds the consideration of aquatic vegetable consumption to the traditional method of human health AWQC derivation and risk assessments for the first time,and this approach can promote the development of risk assessments and water quality criteria.

Water quality criteria for 4-nonylphenol in protection of aquatic life

Here reproduction and death toxicity data were selected for 4-nonylphenol based on endocrine disrupting properties of the re- productive system. Assessment factor （AF） and species sensitivity distribution （SSD） curve were employed to derive criteria maximum concentration （CMC） and criteria continuous concentration （CCC） of three different 4-nonylphenols for protection of aquatic life. The results showed that the CMC and CCC based on SSD method and death toxicity data for three different 4-nonylphenols （CAS No： 104405, 25154523, 84852163） were 26.7, 13.6, 3.84μg L-1 and 8.86, 2.21, 0.97 μg L-1, respectively. Based on SSD and reproductive toxicity data, the CCC values of different 4-nonylphenols （CAS No： 104405, 25154523） were 1.59 and 1.34μg L-l, respectively. The CCC values obtained by the AF for three different 4-nonylphenol （CAS No： 104405, 25154523, 84852163） were 0.165, 1.03, 0.74 μg L -1 and 0.5, 0.5, 0.1μg L-1, respectively, based on death toxicity data and re- productive toxicity data. The CCC values obtained by AF were all lower than the corresponding criteria values obtained by SSD, and the CCC values based on reproductive toxicity data were less than those based on the death toxicity data. This study provides a useful method for deriving water quality criteria for endocrine disruptors.

Developing sediment quality criteria for heavy metal pollution in the Le An River with equilibrium partitioning approach

Equilibrium partitioning(EqP) approach was selected to establish the sediment quality criteria(SQC) in the Le An River near Dexing Copper Mine. Both freshwater quality criteria (WQC) for some heavy metals regulated by USEPA and national quality standards of surface water recommended by CNEPA were used as protective levels of aquatic organisms in this study. Meanwhile, the partitioning coefficients were derived directly from measured data. Comparison between SQC in this region and concentrations of contaminants in situ clearly indicated the distribution characteristics of metal contamination along the river. And the results also illustrated that measures of some metals exceeded their SQC levels in different degree, especially Cu.

Deriving freshwater quality criteria of sulphocyanic sodium for the protection of aquatic life in China

The freshwater quality criteria of sulphocyanic sodium (NaSCN) were studied on the basis of the features of the aquatic biota in China, and with reference to U.S.EPA's guidelines. Acute tests were performed on twelve different domestic species to determine 48h EC 50 /96h EC 50 (or 96h LC 50 ) values for NaSCN. 21d survival reproduction test with Daphnia magna, 60d fry juvenile part life stage test with Carassius auratus gibelio and 96h growth inhibition test with Lemna minor were also conducted to estimate lower chronic limit/upper chronic limit values. In the acute tests, D.magna was the most sensitive species to NaSCN followed by Tilapia mossambia, Cyprinus carpio and C.auratus gibelio in turn. The final acute value of NaSCN was 2.699 mg/L. In the chronic tests, reproduction of daphnids were significantly reduced by NaSCN at 1.0 mg/L. Acute to chronic ratios ranged from 5.96 to 19.1. A final chronic value of 0.2530 mg/L was obtained and a final plant value was 1346 mg/L. A criterion maximum concentration (1.349 mg/L) and a criterion continuous concentration (0.2530 mg/L) were derived respectively. The results of this study may provide useful data to derive national WQC for NaSCN as well as the procedures of deriving WQC of other chemicals for the protection of aquatic biota in China.

Sediment quality criteria for heavy metal pollution in the Le An River with triad approach

In this study, integrative traid was used to sediment quality in the Le An River, which has been strongly contaminated by large amount of Cu, Pb, Zn,Cd, As and Cr discharging from mining activities. All available data collected from chemical analyses,toxic tests and field survey on benthic macroinvertebrates were transformed into ratio to reference(RTR) and relevant scales.The responses of receiving environment to mining impacts were illustrated by traid graphs. Traid results indicated that a sectional distribution pattern existed from upstream to downstream:(a) relative clean upstream;(b) serious contaminated middle stream;(c) gradual recovery downstream. This situation was closely related with local mining activities, which caused obvious degradation of sediment quality in some sections, therefore, remediation was required urgently.

Determination of water environment standards based on water quality criteria in China:Limitations and feasibilities

There is a need to formulate water environment standards（WESs） from the current water quality criteria（WQC） in China.To this end,we briefly summarize typical mechanisms applied in several countries with longer histories of developing WESs,and three limitations to formulating WESs in China were identified.After analyzing the feasibility factors including economic development,scientific support capability and environmental policies,we realized that China is still not ready for a complete change from its current nation-wide unified WES system to a local-standard-based system.Thus,we proposed a framework for transformation from WQC to WESs in China.The framework consists of three parts,including responsibilities,processes and policies.The responsibilities include research authorization,development of guidelines,and collection of information,at both national and local levels;the processes include four steps and an impact factor system to establish water quality standards;and the policies include seven specific proposals.

The Derivation of Nutrient Criteria for the Adjacent Waters of Yellow River Estuary in China

Ecological protection and high-quality development of the Yellow River basin are becoming part of the national strategy in recent years.The Yellow River Estuary has been seriously affected by human activities.Especially,it has been severely polluted by the nitrogen and phosphorus from land sources,which have caused serious eutrophication and harmful algal blooms.Nutrient criteria,however,was not developed for the Yellow River Estuary,which hindered nutrient management measures and eutrophication risk assessment in this key ecological function zone of China.Based on field data during 2004-2019,we adopted the frequency distribution method,correlation analysis,Linear Regression Model(LRM),Classification and Regression Tree(CART)and Nonparametric Changepoint Analysis(nCPA)methods to establish the nutrient criteria for the adjacent waters of Yellow River Estuary.The water quality criteria of dissolved inorganic nitrogen(DIN)and soluble reactive phosphorus(SRP)are recommended as 244.0μg L^(−1) and 22.4μg L^(−1),respectively.It is hoped that the results will provide scientific basis for the formulation of nutrient standards in this important estuary of China.

Applications of Graph Theory to Gross Error Detection for GPS Geodetic Control Networks

This paper describes a broad perspective of the application of graph theory to establishment of GPS control networks whereby the GPS network is considered as a connected and directed graph with three components.In this algorithm the gross error detection is undertaken through loops of different spanning trees using the "Loop Law" in which the individual components Δ X, Δ Y and Δ Z sum up to zero.If the sum of the respective vector components ∑X,∑Y and ∑Z in a loop is not zero and if the error is beyond the tolerable limit (ε>w),it indicates the existence of gross errors in one of the baselines in the loop and therefore the baseline must be removed or re_observed.After successful screening of errors by graph theory,network adjustment can be carried out.In this paper,the GPS data from the control network established as reference system for the HP Dam at Baishan county in Liaoning province is presented to illustrate the algorithm.

Mixing Zone Guidelines Application in a Smelter in Northern Sweden with Discharge to the Baltic Sea

This pilot study intended to investigate the application of Mixing Zone Guidelines in northern Sweden. The EC （European Commission）-Mixing Zone Guidelines were applied to seven effluent discharges. The effluents were from industrial processes used in the Ronnskar smelter, in northern Sweden. Each outlet in the smelter area discharges water into the Bothnian bay of the Baltic Sea. Cadmium （Cd）, mercury （Hg）, nickel （Ni） and lead （Pb） were the primary substances present in the effluents. A ＂Tiered Approach＂ was followed for mixing zone assessments in each of the discharge points. Discharge Test was used at Tier 2 and CORMIX （Cornell Mixing Zone Expert System model）, version 7, at Tier 3. At each discharge point, the AA-EQS （annual average-environmental quality standard） for each metal was met within a distance of 500 m from the outfalls. This distance was exceeded to meet the MAC-EQS （maximum allowable concentration-environmental quality standard） criteria at points 1 and 3 for total Hg concentrations. However, for the proper application of Mixing Zone Guidelines, a version of the Discharge Test for coastal waters should be developed and used. The decision at which tier the dissolved metal concentration should be compared with EQS values could depend on the effluent characteristics. For Swedish coastal waters, some consideration should be given to the background concentration of metals.

Resilient water quality management: Insights from Japan's environmental quality standards for conserving aquatic life framework

Currently,chemicals and waste are recognized as key drivers of habitat degradation and biodiversity loss in aquatic ecosystems.To ensure vibrant habitats for aquatic species and maintain a sustainable aquatic food supply system,Japan promulgated its Environmental Quality Standards for the Conservation of Aquatic Life(EQS-CAL),based on its own aquatic life water quality criteria(ALWQC)derivation method and application mechanism.Here we overview Japan's EQS-CAL framework and highlight their best practices by examining the framework systems and related policies.Key experiences from Japan's EQS-CAL system include:(1)Classifying six types of aquatic organisms according to their adaptability to habitat status;(2)Using a risk-based chemical screening system for three groups of chemical pollutants;(3)Recommending a five-step method for determining ALWQC values based on the most sensitive life stage of the most sensitive species;(4)Applying site-specific implementation mechanisms through a series of Plan-Do-Check-Act loops.This paper offers scientific references for other jurisdictions,aiding in the development of more resilient ALWQC systems that can maintain healthy environments for aquatic life and potentially mitigate ongoing threats to human societies and global aquatic biodiversity.

Preliminary analysis of species sensitivity distribution based on gene expression effect

Species sensitivity analysis is one of the major techniques applied to derive water quality criteria. Presently, the toxicity data used for development of water quality criteria are mainly in the biological individual level. With the increase of ecotoxicogenomics toxicity data, it is worth studying whether the gene expression effect data can be used to derive water quality criteria. Taking cadmium, copper and zinc as examples, we analyzed the toxic effects of the three heavy metals by constructing the species sensitivity distribution curves on the basis of extensive toxicity data. The results showed that the rank of species sensitivity for the acute, chronic and gene expression effect toxicity data of cadmium is "chronic>gene>acute". Although the gene expression effect data of copper and zinc are insufficient, the trend of data sensitivity of zinc is similar to cadmium. However, the trend of species sensitivity of copper is different from that of cadmium and zinc with higher sensitivity of gene expression data. It suggested that though the existing data of gene expression effects are not sufficient enough, they have the potential to be used in the development of chronic water quality criteria. For application in the derivation of water quality criteria, illogical test concentration design and insufficient target genes are two main weaknesses in the study of gene expression effects.