Water Quality Criteria Research Articles

Determining water quality of the lower basin of the Usumacinta River in Tabasco, Mexico

Objective: The objective of this study was to determine the water quality of the lower basin of the Usumacinta River, based on its physicochemical and microbiological characteristics. Design/methodology/approach: There were taken 11 monthly samplings of surface water during the rainy season, from June to December, 2017 and in the dry season, from April to May, 2018, in three different sites. The parameters of temperature, pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Suspended Solids (TSS), total phosphorus (TP) and Nitrogen nitrate (N-nitrate) were evaluated. Significant statistical differences (p≤0.05) between seasons and between sites were determined. Results: The results obtained were compared with Mexican regulations and Ecological Criteria for water quality. The parameters such as EC, TDS, TSS and total phosphorus showed substantial differences among seasons. The temperature, pH, EC and N-nitrate, did not exceed the maximum permissible limits for the use of irrigation water, urban public use and protection of aquatic life. However, the presence of E. coli and total coliforms from 530 to> 24 196 MPN/100 ml was recorded throughout the study period. Findings/conclusions: Parameters under study did not show significant differences between sites. The rainy season had an important effect on the increase in concentrations of TSS, TP, N-nitrate and total coliforms. Also, that maximum concentrations were recorded during the study period in the sampling sites of Boca del Cerro (R1) and Puente Chablé (R2).

Use of Interspecies Correlation Estimation (ICE) Models to Derive Water Quality Criteria of Microplastics for Protecting Aquatic Organisms.

Microplastics (MPs) in the water environment pose a potential threat to aquatic organisms. The Species Sensitivity Distribution (SSD) method was used to assess the ecological risks of microplastics on aquatic organisms in this study. However, the limited toxicity data of aquatic organisms made it impossible to derive water quality criteria (WQC) for MPs and difficult to implement an accurately ecological risk assessment. To solve the data gaps, the USEPA established the interspecies correlation estimation (ICE) model, which could predict toxicity data to a wider range of aquatic organisms and could also be utilized to develop SSD and HC5 (hazardous concentration, 5th percentile). Herein, we collected the acute toxicity data of 11 aquatic species from 10 families in 5 phyla to fit the metrical-based SSDs, meanwhile generating the ICE-based-SSDs using three surrogate species (Oncorhynchus mykiss, Hyalella Azteca, and Daphnia magna), and finally compared the above SSDs, as well as the corresponding HC5. The results showed that the measured HC5 for acute MPs toxicity data was 112.3 μg/L, and ICE-based HC5 was 167.2 μg/L, which indicated there were no significant differences between HC5 derived from measured acute and ICE-based predicted values thus the ICE model was verified as a valid approach for generating SSDs with limited toxicity data and deriving WQC for MPs.

Kualitas Air Sungai

This study aims to analyze the water quality of the Barumun river in Pinang City based on water quality criteria and formulate a pollution control strategy that needs to be implemented. The method used is descriptive and quantitative by analyzing river water quality status based on the pollution index. The results showed that the PI value of Barumun river water ranged from 0.82 to 1.71. The recommended pollution control strategies are: 1) maintaining river border protection zones involving environmental cadres and green communities in monitoring; 2) supervision and control of water pollution along the river; 3) improving monitoring of river water quality and supervision of wastewater discharge into rivers; 4) the granting of a wastewater disposal permit (IPLC) to the river must pay attention to the condition of the capacity of the river's pollution load capacity and enforce environmental laws against business actors who violate the established environmental quality standards. In conclusion, the Barumun River in Kota Pinang has decreased in quality, with the status of water quality being lightly polluted. The recommendations for water pollution control strategies that need to be implemented are progressive strategies.
 Keywords: Water Quality, Water Pollution Control, Water Quality Status

Flexible decision-making framework for developing operation protocol for water distribution systems

Past water distribution systems (WDS) management studies derived operation protocols to maximize WDS reliability by using residual chlorine as the sole surrogate parameter for water quality reliability. Albeit the advancement in mechanistic modeling to examine the WDS water quality, emerging water quality parameters of concern are not yet involved in solving WDS management problems. This paper attempts to overcome this limitation by developing a flexible decision-making framework -integrating EPANET-C, a mechanistic modeling tool for WDS water quality, with Analytic Hierarchy Process (AHP), a multi-criteria decision-making method - to rank the possible water quality parameter-based operating alternatives (organic matter and residual chlorine levels at the source points) for WDS. The uncertainty analysis was incorporated into the mechanistic modeling using the Monte Carlo method to realize insufficient knowledge about the complex biological and physicochemical interactions inside WDS. Six cases, each ranking the alternatives diversely, were applied to reflect the expert judgment impressions on the AHP outcomes. The consistency of the proposed decision-making framework was verified by deriving the operation protocol for two test networks by making trade-offs between the multiple and conflicting microbiological, chemical, and organoleptic quality criteria. The disinfection by-products formation control and taste and odor problems control emerged as the most critical water quality criteria determining the WDS performance under the operating alternatives examined. Altogether, the obtained results suggested the practicality of adopting a flexible operation protocol to maintain the water quality benchmarks over various plausible WDS performance scenarios, ranging from worst to best.

Methodology for evaluation of potential sites for large-scale riverbank filtration

Despite being a simple and inexpensive pretreatment technology, the cost-effectiveness of riverbank filtration (RBF) depends on complex hydrogeological and hydrogeochemical variables. One of the most important issues for decision makers regarding RBF is optimal site selection. Therefore, a methodology for multicriteria site evaluation for large-scale RBF schemes is offered. The methodology is primarily designed as a prescreening method, applied over a wide area, but can also serve as a guide for evaluating individual RBF sites. To facilitate further discussion about improvements on the methodology, the reasoning behind each relevant factor and its weight in the evaluation is presented. The methodology is divided into three sequential steps through which a site can be assessed. The first step is to establish the existence of connectivity between the river and aquifer. This is termed the essential criterion, and is a binary determination of site suitability. If the site is determined to be suitable, it is then assessed via a set of quantity criteria, which measure the aquifer capacity and amount of bank filtrate that can be effectively abstracted. Lastly, water quality criteria are assessed by means of surface-water and groundwater quality. The quantity and quality criteria form a result expressed as the site suitability index (SSI), which ranges from 0 to 1, where higher scores represent increased suitability. Finally, the methodology is applied to evaluate existing sites of large-scale RBF application as a demonstration of its applicability. The success of these existing sites is compared to the calculated SSI value and discussed.

An analysis of the use of the relative source contribution term in derivation of drinking water standards using perfluorooctanoic acid as an example.

The relative source contribution (RSC) term has long been used by the US Environmental Protection Agency (USEPA) and state regulatory agencies in setting criteria in water. The RSC reflects the proportion of the total daily intake of a chemical that can be derived from water when all other sources of exposure (e.g., food, air) are considered. This term is applied by the USEPA and state regulatory agencies when deriving ambient water quality criteria, maximum contaminant level goals, and drinking water health advisories for noncarcinogenic and threshold carcinogenic compounds. The value assigned to the RSC term affects the calculated criteria directly, with the allowable concentration in water decreasing with a decreasing RSC. A default RSC value of 20%-applied by regulatory entities in the USA for more than 40 years-assumes that 80% of an individual's exposure to a chemical's reference dose is from nonwater sources. Although the RSC is a chemical-specific parameter, there are few instances where a value other than the default of 20% has been approved and used. In 2000, USEPA outlined the process for developing chemical-specific RSC values, yet primary use of the default RSC value has continued since then. This article reviews USEPA's methodology for deriving chemical-specific RSC values and provides a case example using perfluorooctanoic acid (PFOA) to explore how the USEPA and state regulatory agencies are applying USEPA's guidance. The case study highlights inconsistent derivation of the RSC term, rooted in limitations in the current methodology. We suggest additional clarification of and more thoughtful use of the available data that may not meet USEPA's current adequacy requirements. We also recommend that the USEPA discuss recommendations for using biomonitoring data to set RSCs. Integr Environ Assess Manag 2023;19:605-612. © 2022 SETAC.

First record of red-tide in Elba protectorate coast using Sentinel-3 and its impacts on ecosystem

This study is the first to document an algal bloom caused by Noctiluca scintillans, which was detected using remote sensing techniques and confirmed in the field along the coast of Elba National Park. Noctiluca scintillans is a phytoplankton species that accumulate toxic ammonia that endangers various organisms, including fish, birds, mammals, and human. Therefore, monitoring red tide is essential for water pollution control and management. This study aims to evaluate the potential of the recent launch of the Ocean and Land Color Instrument (OLCI) onboard the Sentinel-3 satellite to identify chlorophyll-a (Chl-a) as a proxy for an algal bloom event and study its impacts on the ecosystem. To fulfill the aim, OLCI images were collected over the study area from the 25th of May to the 13th of June 2017. Satellite images were converted from level 1 to level 2 through radiometric and atmospheric correction, and Chl-a maps were produced from the level 3 data during product development using standard Ocean Color 4 for MERIS (OC4Me) model. The time-series analyses of the Sentinel-3 satellite images indicated that the algal blooms (Red tide) event occurred four days at the studied sites (7th to 10th of June). The current findings reveal a strong relationship between the deterioration in water quality criteria and Noctiluca scintillans cell counts (×104) /L (0.05 > P ≤ 0.01). This study strongly urges routine monitoring of the physicochemical characteristics of coastal waters and using remote sensing techniques for early rid tide detection to control the phenomenon.

Occurrence, health risk assessment and water quality criteria derivation of six personal care products (PCPs) in Huangpu River, China.

Personal care products (PCPs) have shown adverse health effects on humans. However, their health risk associated with fish consumption and relevant water quality criteria are still not well documented. This study investigated the occurrence and health risk of six PCPs (triclosan, bisphenol-A, and four commonly used organic ultraviolet (UV) filters, i.e., homosalate (HMS), 4-methylbenzylidene camphor (4-MBC), oxybenzone (BP-3), and octocrylene (OC)). River water and three trophic levels of fish species were collected from Huangpu River in Shanghai. The concentration range of the six PCPs were 1.48-89.76ng/L in water and 0.40-10.75ng/g dry weight in fish. Estimated daily intake (EDI) and target hazard quotient (THQ) of the PCPs indicated that consuming these fish would not pose non-carcinogenic risks. The maximum allowable fish consumption rates ranged from 85 to 1760 and 155 to 3230 meals per month for children and adults, respectively. As to the four organic UV filters, it is the first time to report the fish consumption advisories. Finally, the human health ambient water quality criteria (AWQC) values of HMS, 4-MBC, BP-3, OC, TCS, and BPA (i.e., 0.1218, 0.7311, 0.3494, 0.0477, 235.8, and 154.7μg/L, respectively) were proposed, and they can serve as a valuable technical reference for global development and revision of aquatic environmental quality standards for these emerging contaminants.

Assessing the impact of wastewater treatment works effluent on downstream water quality

The impact of wastewater treatment works (WwTW) effluent on downstream river water quality is of increasing concern, particularly owing to the presence in effluents of a range of trace substances. In the case of contamination by metals the question of bioavailability has recently been accounted for in setting water quality standards for several metals. In the UK over the past decade the Chemical Investigations Programme (CIP) has generated upstream and downstream river quality data as well as associated WwTW effluent monitoring for over 600 sites, for the main contaminants of regulatory interest under the Water Framework Directive. Data presented here show that at a local level WwTW discharges have little impact for many contaminants. Soluble reactive phosphorus, hexabromocyclododecane (HBCDD), cypermethrin, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) have been shown to be the principal substances where downstream concentrations were at least 10 % larger than the upstream value. Otherwise, poor compliance with riverine water quality standards tends to be associated with contamination at the river catchment scale, with corresponding implications for the nature of remedial actions that are likely to be successful. Compliance with water quality criteria for metals, taking account of bioavailability, is high overall.

Levels of metals and elements in tissues of fish species in the Kızılırmak River (Turkey) and assessment of health risks and nutritional benefits

Although the Kızılırmak River, the longest river in Turkey, is home to many fish species, there are a few studies reporting metal levels in fish in the river. The contents of 17 metals and elements (MEs) in various tissues of three fish species and surface water from the river were investigated. Significant differences in the ME levels among tissues were recorded, and the highest levels of most MEs were recorded in the gills and liver. The results revealed that correlations between MEs in tissues and fish size were not clear and consistent. Among the MEs, P (6058–109489) and Zn (933–47556) had the highest bioconcentration factor values. The levels of As and Cd in the river water exceeded water quality criteria. Health risk assessment methods (Target Hazard Quotient, Estimated Daily Intake and Lifetime Carcinogenic Risk) indicated that consumption of the studied fish species is safe. It was estimated that a weekly consumption of 490 g of C. gibelio, or 350 g of C. carpio or 280 g of T. tinca would not cause any health risks. Furthermore, it was found that fish species would provide significant benefits in terms of intake of nutrients such as P, K, Ca, Mg, Cu, Zn, Fe and Mn. These findings revealed that nutritional benefits from consumption of fish species outweigh the health risks posed by metals in fish.

Enhancement of nitrogen removal by a modular design of vertical flow constructed wetlands with a plant carbon source: Optimization of carbon dosage for nitrogen removal, practicability evaluation and strategy exploration for water quality control

The requirement of artificial aeration for increasing nitrogen removal in vertical flow constructed wetlands (VFCWs) brings extra energy consumption and complex maintenance. The feasibility of a modular design to replace artificial aeration for partially saturated VFCWs with palm bark as a carbon source (PSVFCW-pb) to achieve water quality control, especially nitrogen removal was evaluated. The PSVFCW-pb with a spatially separate structure and perforated peripheries for better oxygen diffusion had a promising total nitrogen removal (e.g., 66.4% at a dosage of 1.435 g/L of palm bark pretreated at 120 °C for 40 min) without additional aeration, while organic carbon removal was nearly unaffected. An appropriate increase of the palm bark dosage (≤1.435 g/L) resulted in higher nitrogen removal; however, a more palm bark (1.875 g/L) could not further increase nitrogen removal but caused color pollution. In addition, the removal of nitrogen by the modularized PSVFCW-pb was more sensitive to the ambient temperature than the removal of organic carbon and phosphorus, and the higher temperature was preferable. Notably, the more attractive property of the modular design is its great potential to improve nitrogen removal by conveniently altering the number and/or scale of oxic and oxygen-free modules. Finally, the relationships between the hydraulic load and inflow concentration were explored, by which the suitable hydraulic load could be flexibly adjusted based on real-time water quality to meet the specified surface water quality criteria in different seasons. This study provides a reliable CW design for controlling nutrient pollution in surface waters.

Effects of anthropogenic activities on nutrient parameters in the North Eastern Mediterranean Sea (Bay of Sığacık/Aegean Sea)

This study aims to examine the physicochemical parameters of seawater (temperature, pH, salinity, dissolved oxygen, suspended particulate matter, ammoniumnitrogen, nitrite-nitrogen, nitrate-nitrogen, and phosphatephosphorus, burnable organic matter in the sediment), and possible effects of pollution in Sığacık Bay where different anthropogenic activities are carried out. Samples of surface seawater (0 m), bottom seawater (2 m), and sediment were collected monthly from four sampling sites between September 2013 and September 2014. Annual mean nutrient values were determined as 1.6 ± 0.14 µg.at.NH4 +-N l-1, 0.1 ± 0.01 µg.at.NO2 - -N l-1, 0.8 ± 0.08 µg.at.NO3 - -N l-1, 0.7 ± 0.08 µg.at.PO4 3--P l-1, SPM 21.4 ± 0.33 mg l-1. The BOM content in the sediment was 5.6 ± 0.39%. As a result of the study, it was determined that Sığacık Bay was polluted by anthropogenic point and non-point source pollution. According to the water quality criteria, the bay was found to be in the group of polluted seawater in terms of phosphate phosphorus.

Distribusi dan Keanekaragaman Makrozoobentos

This study aims to determine the distribution and diversity of macrozoobenthos species in the Barumun River, Kota Pinang District, South Labuhanbatu Regency. The method used is an exploratory method with purposive sampling. The data analyzed were longitudinal distribution, diversity index, evenness index and dominance index. The results showed that there were 15 types of macrozoobenthos with a low diversity index value at all stations. In conclusion, the diversity of macrozoobenthos in the Barumun River is relatively small, so the water quality criteria for this river are categorized as moderately polluted.
 Keywords: Diversity, Water Quality, Macrozoobenthos, Barumun River

Derivation of copper water quality criteria in the Bohai Sea of China considering the effects of multiple environmental factors on copper toxicity

Copper has become one of the most important heavy metal pollutants in the environment because of its wide application and high toxicity, but research on water quality criteria (WQCs) on copper is limited, especially the derivation of seawater WQC. In addition, the toxicity of copper in the seawater system is affected by various environmental factors. Therefore, establishing a WQC that meets the characteristics of the regional environment is a top priority. The correlations between four factors of temperature, salinity, pH, dissolved organic carbon (DOC) and the toxic effect values of copper were analyzed in this study, and the temperature was determined as the most influential factor among the four factors in the Bohai Sea. A specific correlation between temperature and the toxic effects of copper was identified, and WQCs were derived based on the identified correlation and the variations of the Bohai Sea's temperature in different seasons by species sensitivity distribution (SSD) method. Under the condition of the winter, spring, autumn, and summer with an average water temperature of 0.09, 15.96, 17.83, and 24.87 °C, the obtained short-term water quality criteria (SWQCs) were 44.29, 4.70, 4.31, and 3.33 μg/L; the long-term water quality criteria (LWQCs) were 18.14, 1.93, 1.77 and 1.36 μg/L. The findings indicated the importance of introducing specific environmental conditions during the derivation process. This work could provide valuable information for pollution prevention and aquatic life protection in the Bohai Sea and provide a valuable reference for the derivation of criteria in other regions alike.

Establishment of a comprehensive method to derive seawater quality criteria of BDE-47 in China

2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) is an emerging toxic organic pollutant widely detected in territorial waters. Accordingly, establishing the seawater quality criteria (SWQC) for BDE-47 is of significant importance to protect the marine ecosystems. In this study, published ecotoxicity data of BDE-47 to aquatic species in China were collected, and acute and chronic toxicity tests were carried out on saltwater aquatic organisms from 5 phyla and 8 families widely existed in the Chinese marine environment. Static acute toxicity tests and renewed chronic toxicity tests were adopted. The scientific theories and technical methods of the United States Environmental Protection Agency (US EPA), Canada, the European Union (EU), and the Netherlands on water quality criteria guidelines, as well as the Chinese freshwater quality criteria guidelines were compared. Then an integrated method of SWQC derivation was introduced through comprehensive consideration. Afterward, the SWQC of BDE-47 was derived based on the ecotoxicity data. The SWQC includes short-term seawater quality criteria (S-SWQC), long-term seawater quality criteria (L-SWQC), and serious risk concentration for the ecosystem (SRCeco). And they were derived and recommended as 7.90 μg/L, 0.217 μg/L, and 3.65 μg/L, respectively. This study served as a specific example to quantitatively studies the differences between different scientific theories and technique methods. The derivation process and improvement of SWQC for BDE-47 provide support for the future revision of water quality criteria in China.

Deriving optimal hydraulic, water quality and habitat quality criteria against a predefined reference state of urban canals via an analytical method: Implications on ecological rehabilitation

The aim of this study was to showcase derivation of numerical ranges of important environmental variables (hydraulics, water quality and habitat quality) for a predefined reference state of canals in an area where ecological rehabilitation is sought. The reference state was defined based on pollution tolerance index (PTI) of macroinvertebrates. From data collected for two years from three canals with varying levels of pollution for different seasons, detrended correspondence and redundancy analysis ordination plots revealed moderate to weak spatiotemporal gradients. Relationships were built via multiple linear regression (MLR) and by linear or quadratic bivariate models. MLR models managed to explain over 70% of the PTI variation and was significant at P < 0.1. Solving single parameter models with co-efficient of determination >0.3 and P < 0.1 with a targeted PTI of 11, gave season dependent feasible solutions and were mostly hydraulic and habitat quality variables. Out of 24 environmental variables, dry and wet seasons gave 15 and eight feasible solutions, respectively. This study validated the importance of certain environmental variables that are debatable in the context of a healthy stream (e.g., mesoscale physical habitats), showed instances where hydraulics became the defining factor of stream health, and also provided pros and cons of a widely discussed method in ecological rehabilitation.

Predicting the Thermal Regime of the Sebou River Estuary (Morocco) Using a One-Dimensional Model (HEC-RAS 5.0)

Temperature is regarded as one of the most important variables for aquatic life, as well as a key physical criterion of water quality, due to its role in a variety of chemical, physical, and biological processes. We chose the HEC-RAS tool to model the thermal regime of the Sebou-Kenitra river estuary because it is impossible to determine the spatiotemporal evolution of temperature in watercourses using traditional methods such as single measurements or interpolation due to the influence of several factors, including hydraulic, tidal rhythm, upstream contributions, and intrusion. The main goal of this research is to develop and test the “HEC-RAS” model with the aim of better understanding thermal dynamics and predicting the spatiotemporal variation of the Sebou river estuary temperature, using the energy transport equation and a variety of input data such as initial temperature, air temperature, wind speed, and dispersion coefficient. The HEC-RAS model, which takes into account many meteorological and geophysical elements and provides an overview of the thermal situation at our study site “the Sebou river estuary,” has also been acknowledged for its deterministic role. We illustrated the impact of meteorological and tidal data on spatiotemporal temperature change at numerous places in the Sebou river estuary by using this model.

Water quality criteria for lanthanum for freshwater aquatic organisms derived via species sensitivity distributions and interspecies correlation estimation models

The increasing exploitation and application of rare earth elements (REEs) may induce hazardous risks to freshwater aquatic organisms. Due to the lack of water quality criteria (WQC) and sufficient reliable toxicity data, little information is available on the ecological risk of REEs in surface water. In this study, lanthanum (La) toxicity data were collected from published toxicological studies, and the data quality was assessed using a toxicological data reliability assessment tool. To obtain more toxicity data, Daphnia magna, Cyprinus carpio, and Dania rerio embryos were selected as surrogate species, and an interspecies correlation estimation (ICE) model was used to predict the toxicity of La for untested species. The species sensitivity distributions (SSDs) of La toxicity and WQC were investigated. Differences were observed in the hazardous concentrations for 5% of species (HC5), but no statistically significant differences were noted in the SSD curves between the measured acute toxicity data and the predicted data. For the SSDs constructed from the measured toxicity data, the ICE-predicted toxicity data and all acute data supplemented with the ICE-predicted data, the acute WQC values of La were 88, 1022 and 256 μg/L, respectively. According to the SSD and corresponding HC5 of chronic toxicity data, the chronic WQC was 14 μg/L. The results provide a scientific reference for establishing WQC for freshwater aquatic organisms and ecological risk assessments of REEs.

Índices de calidad de agua en México y Colombia. Evolución, criterios y cambios

The Water Quality Index (WQI) is a simple and easy-to-understand tool for analyzing and reporting quality trends. Water quality is not static and depends on multiple factors, in this sense; globally various indices have been developed based on local water quality criteria. This paper explores and discusses about water quality assessment and their steps taking into account the widely used index models in the world. These steps include selecting the parameters, sub-index generation, weightings of the parameters, and sub-indices aggregation. The advantages and disadvantages of each index identified,and the main limitations that arise in the calculation of the different methodologies detected. These limitations are the subjectivity in selecting and weighing the parameters and the ambiguity and eclipsing in the aggregation stage. Objectivemethodological tools to solve these limitations consider the use of statistical and fuzzy logic techniques. The CCMEWQI is a versatile water quality index, since it allows the determination of the temporal and spatial conditions for the different uses in a specific way, achieving with regulations, and based on the analysis of monitoring data for each region.

Hardness-Dependent Water Quality Criteria for Protection of Freshwater Aquatic Organisms for Silver in China.

Silver is toxic to freshwater aquatic organisms and aquatic ecosystems, and it is necessary to develop regional water quality criteria (WQC) for silver to protect the freshwater aquatic organisms in China. The toxicity database of silver for freshwater aquatic organisms involved 121 acute toxicity values for 35 species (6 phyla and 27 families) and 15 chronic toxicity values for 4 species (2 phyla and 4 families). Teleost fish showed the most sensitivity to silver after both short-term and long-term exposure. Significant correlations between the natural logarithms of hardness and the natural logarithms of acute silver toxicity were found for Daphnia magna, Oncorhynchus mykiss, and Pimephales promelas. The criterion maximum concentration (CMC) was calculated by the species sensitivity distribution method with sigmoid as the best fitting model (Adj R2 0.9797), and the criterion continuous concentration (CCC) was obtained by the acute-to-chronic ratio method. The CMC and CCC of silver were , and respectively, in China, with water hardness (, mg/L) as an independent variable. This research can provide a basis and reference for the management of silver to protect freshwater aquatic organisms in China.