Species Sensitivity Distribution Model Research Articles

Occurrence, distribution, and ecological risk assessment of heavy metals in Chao Phraya River, Thailand

Understanding heavy metals in rivers is crucial, as their presence and distribution impact water quality, ecosystem health, and human well-being. This study examined the presence and levels of nine heavy metals (Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn) in 16 surface water samples along the Chao Phraya River, identifying Fe, Mn, Zn, and Cr as predominant metals. Although average concentrations in both rainy and dry seasons generally adhered to WHO guidelines, Mn exceeded these limits yet remained within Thailand’s acceptable standards. Seasonal variations were observed in the Chao Phraya River, and Spearman’s correlation coefficient analysis established significant associations between season and concentrations of heavy metals. The water quality index (WQI) demonstrated varied water quality statuses at each sampling point along the Chao Phraya River, indicating poor conditions during the rainy season, further deteriorating to very poor conditions in the dry season. The hazard potential index (HPI) was employed to assess heavy metal contamination, revealing that during the dry season in the estuary area, the HPI value exceeded the critical threshold index, indicating the presence of heavy metal pollution in the water and unsuitable for consumption. Using the species sensitivity distribution model, an ecological risk assessment ranked the heavy metals’ HC5 values as Pb > Zn > Cr > Cu > Hg > Cd > Ni, identifying nickel as the most detrimental and lead as the least toxic. Despite Cr and Zn showing a moderate risk, and Cu and Ni posing a high risk to aquatic organisms, the main contributors to ecological risk were identified as Cu, Ni, and Zn, suggesting a significant potential ecological risk in the Chao Phraya River’s surface water. The results of this study provide fundamental insights that can direct future actions in preventing and managing heavy metal pollution in the river ecosystem.

Climate warming shifts riverine macroinvertebrate communities to be more sensitive to chemical pollutants.

Freshwaters are highly threatened ecosystems that are vulnerable to chemical pollution and climate change. Freshwater taxa vary in their sensitivity to chemicals and changes in species composition can potentially affect the sensitivity of assemblages to chemical exposure. Here we explore the potential consequences of future climate change on the composition and sensitivity of freshwater macroinvertebrate assemblages to chemical stressors using the UK as a case study. Macroinvertebrate assemblages under end of century (2080-2100) and baseline (1980-2000) climate conditions were predicted for 608 UK sites for four climate scenarios corresponding to mean temperature changes of 1.28 to 3.78°C. Freshwater macroinvertebrate toxicity data were collated for 19 chemicals and the hierarchical species sensitivity distribution model was used to predict the sensitivity of untested taxa using relatedness within a Bayesian approach. All four future climate scenarios shifted assemblage compositions, increasing the prevalence of Mollusca, Crustacea and Oligochaeta species, and the insect taxa of Odonata, Chironomidae, and Baetidae species. Contrastingly, decreases were projected for Plecoptera, Ephemeroptera (except for Baetidae) and Coleoptera species. Shifts in taxonomic composition were associated with changes in the percentage of species at risk from chemical exposure. For the 3.78°C climate scenario, 76% of all assemblages became more sensitive to chemicals and for 18 of the 19 chemicals, the percentage of species at risk increased. Climate warming-induced increases in sensitivity were greatest for assemblages exposed to metals and were dependent on baseline assemblage composition, which varied spatially. Climate warming is predicted to result in changes in the use, environmental exposure and toxicity of chemicals. Here we show that, even in the absence of these climate-chemical interactions, shifts in species composition due to climate warming will increase chemical risk and that the impact of chemical pollution on freshwater macroinvertebrate biodiversity may double or quadruple by the end of the 21st century.

Determining soil conservation strategies: Ecological risk thresholds of arsenic and the influence of soil properties

The establishment of ecological risk thresholds for arsenic (As) plays a pivotal role in developing soil conservation strategies. However, despite many studies regarding the toxicological profile of As, such thresholds varying by diverse soil properties have rarely been established. This study aims to address this gap by compiling and critically examining an extensive dataset of As toxicity data sourced from existing literature. Furthermore, to augment the existing information, experimental studies on As toxicity focusing on barley-root elongation were carried out across various soil types. The As concentrations varied from 12.01 to 437.25 mg/kg for the effective concentrations that inhibited 10% of barley-root growth (EC10). The present study applied a machine-learning approach to investigate the complex associations between the toxicity thresholds of As and diverse soil properties. The results revealed that Mn-/Fe-ox and clay content emerged as the most influential factors in predicting the EC10 contribution. Additionally, by using a species sensitivity distribution model and toxicity data from 21 different species, the hazardous concentration for x% of species (HCx) was calculated for four representative soil scenarios. The HC5 values for acidic, neutral, alkaline, and alkaline calcareous soils were 80, 47, 40, and 28 mg/kg, respectively. This study establishes an evidence-based methodology for deriving soil-specific guidance concerning As toxicity thresholds.

Ecological risk assessment for typical organophosphorus pesticides in surface water of China based on a species sensitivity distribution model

The ecological risks posed by widespread organophosphorus pesticide (OPs) pollution in the surface waters of China remain unclear. In this study, species sensitivity distribution (SSD) parametric statistical approaches were coupled with fully acute and chronic toxicity data to fit the sensitivity distributions of different aquatic species to five typical OPs: dimethoate, malathion, parathion-methyl, trichlorfon, and dichlorvos. Crustaceans exhibit the highest sensitivity to OPs, whereas algae are the least sensitive. The acute hazardous concentrations that affected 5 % of the species (HC5) were 0.112, 0.001, 0.001, 0.001, and 0.001 mg/L for dimethoate, malathion, parathion-methyl, trichlorfon, and dichlorvos, respectively, whereas their chronic HC5 values were 0.004, 0.004, 0.053, 0.001, and 0.0005 mg/L, respectively. Hence, dichlorvos is highly toxic and poses greater risk to non-target aquatic species. The evaluation data revealed varying geographical distribution characteristics of the ecological risks from OPs in 15 freshwater aquatic systems across different regions of China. Dichlorvos posed the highest risk in the basins of Zhejiang and Guangdong Provinces, with the highest chronic Risk Quotient (RQ) and Hazard Index (HI) at 9.34 and 9.92, respectively. This is much higher than what was collected and evaluated for foreign rivers (the highest chronic RQ and HI in foreign rivers were 1.65 and 2.24, respectively). Thus, dichlorvos in the surface waters of China poses a substantial ecological risk to aquatic organisms, and may endanger human health.

Legacy and alternative per-and polyfluoroalkyl substances (PFASs) in the Bohai Bay Rim: Occurrence, partitioning behavior, risk assessment, and emission scenario analysis

The use of alternative per- and polyfluoroalkyl substances (PFASs) has been practiced because of the restrictions on legacy PFASs. However, knowledge gaps exist on the ecological risks of alternatives and relationships between restrictions and emissions. This study systematically analyzed the occurrence characteristics, water-sediment partitioning behaviors, ecological risks, and emissions of legacy and alternative PFASs in the Bohai Bay Rim (BBR). The mean concentration of total PFASs was 46.105 ng/L in surface water and 6.125 ng/g dry weight (dw) in sediments. As an alternative for perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (GenX) had a concentration second only to PFOA in surface water. In sediments, perfluorobutyric acid (PFBA) and GenX were the two predominant contaminants. In the water-sediment partitioning system, GenX, 9-chlorohexadecafluoro-3-oxanone-1-sulfonic acid (F-53B), and 11-chloroeicosafluoro-3-oxaundecane-1-sulfonic acid (8:2 Cl-PFESA) tended to be enriched towards sediments. The species sensitivity distribution (SSD) models revealed the low ecological risks of PFASs and their alternatives in the BBR. Moreover, predicted no-effected concentrations (PNECs) indicated that short-chain alternatives like PFBA and perfluorobutane sulfonate (PFBS) were safer for aquatic ecosystems, while caution should be exercised when using GenX and F-53B. Due to the incremental replacement of PFOA by GenX, cumulative emissions of 1317.96 kg PFOA and 667.22 kg GenX were estimated during 2004–2022, in which PFOA emissions were reduced by 59.2 % due to restrictions implemented since 2016. If more stringent restrictions are implemented from 2023 to 2030, PFOA emissions will further decrease by 85.0 %, but GenX emissions will increase by an additional 21.3 %. Simultaneously, GenX concentrations in surface water are forecasted to surge by 2.02 to 2.45 times in 2023. This study deepens the understanding of PFAS alternatives and assists authorities in developing policies to administer PFAS alternatives.

The interactions between aquatic plants and antibiotics: Progress and prospects

Antibiotics have emerged as a widespread pollutant in the aquatic environment. Aquatic phytoremediation to remove antibiotic pollution in water has aroused increasing research. Due to complex interaction between aquatic plants and antibiotics in the aquatic environment, it is essential to summarize the present research progress and point out the shortcomings to better use aquatic plants to remediate antibiotic pollution. A growing body of evidence indicates roots are the most important tissues for aquatic plants to absorb and accumulate antibiotics and antibiotics can be transferred in aquatic plants. LogKow value is an important factor to affecting the antibiotic absorption by aquatic plant. The study showed that antibiotics have toxic effects on aquatic plants, including metabolic interference, oxidative damage, damage to photosynthetic system, and inhibition of growth. However, the species sensitivity distribution model indicated that the general environmental concentrations of antibiotics pose no risk to aquatic plant growth. Aquatic plants can significantly reduce the antibiotics concentration in water and the removal efficiency is affected by many factors, such as the type of aquatic plants and antibiotics. Macrolide antibiotics are most easily removed by plants. This study reviewed the current research progress and provides valuable scientific recommendations for further research.

Distribution, ecological risks and priority of pharmaceuticals in the coastal water of Qinhuangdao, China

Although there has been a surge of interest in research focused on the presence of pharmaceuticals in the marine environment, study on the distribution and risks of pharmaceuticals in coastal waters remains inadequately documented due to the specific features of the marine environment, such as strong dilution, high salinity, and complex hydrodynamics. In this study, thirty pharmaceuticals with diverse physicochemical properties were analyzed in a coastal sea with low hydrodynamic energy caused by various artificial structures. The results indicate that 14 compounds were detected in seawater, with concentrations ranging from <1 to 201.4 ng L−1, among which caffeine, metoprolol, and atenolol were detected at high levels. Statistical analysis reveals the prevalence of the most target pharmaceuticals with downward trends in concentrations from estuary to offshore region, demonstrating the significant impacts of riverine inputs on the coastal water. Nevertheless, the distribution patterns of caffeine and atenolol were intricate, suggesting that they may have also originated from other unknown sources. A newly-developed method combining risk quotient (RQ) and species sensitivity distribution (SSD) models was used in ecological risk assessment. The results indicate generally higher risks of target pharmaceuticals in the estuary compared to the offshore region, with caffeine, carbamazepine, and norfloxacin identified as the top three priority pollutants.

Estimating species sensitivity distributions for microplastics by quantitatively considering particle characteristics using a recently created ecotoxicity database

Estimation of a species sensitivity distribution (SSD) by fitting a statistical distribution to ecotoxicity data is a promising approach to deriving “safe” concentrations for microplastics. However, most existing SSDs do not quantitatively consider the diverse characteristics of microplastics, such as particle size and shape. To address this issue, based on 38 mass-based chronic no observed effect concentrations (NOECs) obtained from a recently created database, we estimated SSDs that quantitatively consider the influences of three types of microplastic characteristics (particle length, shape, and polymer type) and habitat of the test species (freshwater vs. marine) by using Bayesian modeling. We selected the best SSD model among all possible models using the widely applicable information criterion. The best SSD model included particle length (range: 0.05–280 μm) and a binary dummy variable corresponding to the fiber shape. Lower chronic NOECs were associated with decreasing particle size and with toxicity tests that included fibers in this model. Combined with the fact that the null model (i.e., an SSD model with no predictor variable) was ranked 27th among the 64 candidate SSD models, our results support the need to incorporate particle characteristics such as length and shape (e.g., fiber) into estimations of SSDs for microplastics. The medians of the hazardous concentration of 5% of species (HC5) for microplastic spheres and fragments, estimated by the posterior distributions of individual parameters in the best SSD model, ranged from 0.02 to 2 µg/L, depending on the particle length (0.1–100 μm). For microplastic fibers, the HC5 values were estimated to be approximately 100 times lower than those for microplastic spheres and fragments with the same particle length. However, the 95% Bayesian credible intervals for HC5 estimates for fibers were considerable, expanded by up to five orders of magnitude. Despite many remaining challenges, the Bayesian SSD modeling utilized in this study provides unique opportunities to simultaneously investigate the influences of multiple microplastic characteristics on the NOECs of multiple species, which would otherwise be difficult to discern.

Pollution Characteristics and Risk Evaluation of PAHs in Subsidence Water Bodies in Huainan Coal Mining Area, China

As a class of persistent organic pollutants (POPs), polycyclic aromatic hydrocarbons (PAHs) have mutagenic, teratogenic, and carcinogenic effects, so they can pose a greater threat to the natural environment and human health. Most of the PAHs in coal mining areas originate from the mining and utilization process of coal resources, which has a variety of carriers in the environment: atmosphere, water bodies, soil, sediments, etc. To study their pollution status in the subsidence waters of the Huainan coal mining area, sixteen priority control PAHs of sixteen surface water samples from seven subsidence water bodies were tested using gas chromatography–mass spectrometry (GC–MS), and their pollution characteristics were analyzed. Overall, the concentration of PAHs ranged from 212 to 283 ng·L−1, and benzo[b]fluoranthene (BbF) had the highest average concentration. In addition, the concentration of PAHs above four rings was relatively high. After statistical analysis, the Pearson correlation coefficient calculation showed a highly significant positive correlation between PAHs with the same number of rings. Three principal factors were selected using factor analysis, which could explain 88.37% of the total variance, to conduct the source identification. Coal combustion was found to be the main source of PAH pollution in the area. Then, ecological risk using the risk quotient (RQ) method was carried out. The results showed that PAH contamination was medium risk, among which, benzo[a]anthracene (BaA) and BbF had a high ecological risk. In addition, the results of biological toxicity evaluation using the species sensitivity distribution model (SSD) showed that benzo[a]pyrene (BaP) had a high proportion of potential effects on aquatic organisms. By using the response addition model, the evaluation results showed that the ecological risk of the subsidence water bodies in the Panyi mine was the highest. Finally, human health risks were evaluated from two pathways: dermal contact and ingestion. The carcinogenic health risks from the dermal contact exceeded the permissible limits, while the hazard entropy of non-carcinogenic risks from the above two pathways were less than 1.

Distribution Characteristics and Risk Assessment of Tetracycline Antibiotics (TCs) in Soil-Vegetable System with Soil Fertilized with Animal Manure

The effects of antibiotic contamination on vegetable safety and the ecological risks of soil after returning livestock and poultry manure to the land require sufficient future attention. Tetracycline antibiotics (TCs) are often detected at high concentrations in livestock manure and vegetable production soils. Recently, pot experiments and field investigation methods have often been used to understand the effects of TCs contamination on the vegetable safety and ecological risks of soil, whereas field experiments are employed less frequently. This study investigated the distribution characteristics of TCs in the soil-vegetable system following manure application using a combination of pot and field experiments. The human health risks of the edible parts of Chinese flowing cabbage were assessed using the health risk quotient method based on the acceptable daily intake (ADI-HQ), and the ecological risks of TCs-contaminated soils were evaluated using the risk quotient method associated with the species sensitivity distribution model (SSD-RQ). The results showed that oxytetracycline (OTC) was the major type of TCs in Chinese flowering cabbage based on both the pot and field experiments. The maximum contents (dry weight) of OTC in the aboveground parts of the Chinese flowering cabbage for the pot and field experiments were 29.25 μg·kg-1 and 45.03 μg·kg-1, respectively, whereas those of their underground parts were 87.32 μg·kg-1 and 135.44 μg·kg-1, respectively. Meanwhile, higher contents of TCs were detected in Chinese flowering cabbage collected from the field experiment than those from the pot experiment. OTC was also the major type of TCs in soil from both the pot and field experiments, with their contents up to 604.30 μg·kg-1 and 1013.68 μg·kg-1, respectively. Higher residual contents of three TCs were detected in soils collected from the field experiment than those from the pot experiment. Under the experimental conditions, with the except that OTC in Chinese flowering cabbage from the field experiment would pose medium health risks (HQ>0.1) to children, the contents of three TCs in other treated Chinese flowering cabbage would pose low health risks (HQ ≤ 0.1) to adults and children. In the pot experiments, three TCs present in Chinese flowering cabbage would pose low health risks (HQ ≤ 0.1) to adults and children. Additionally, the TCs in soils with manure application from the pot and field experiments may have posed both moderate or high levels of ecological risks (HQ>0.1 or HQ>1). Therefore, the effects of antibiotic contamination on vegetable safety and their potential ecological risks on soil following manure fertilization need to be given special attention.

Contamination Status and Ecological Security Thresholds of Fluoride in Farmland around a Phosphorus Chemical Plant in a Karst Area of Southwestern China.

The phosphorus chemical plant (PCP) production process leads to the substantial discharge of fluoride into the surrounding environment. However, there is limited research data regarding the pollution levels and ecological safety thresholds of farmland fluoride around PCPs in karst areas. This study evaluates the local contamination status and health risks by determining the fluoride content in farmland and vegetables in vicinity of a PCP in a karst area of Southwestern China. Farmland ecological security threshold was derived based on the species sensitivity distribution (SSD) model. Results showed that the fluoride contents in the soil ranged from 529.36 to 1496.02 mg kg-1, with the median value of 823.93 mg kg-1, which was higher than the national background value in China (478 mg kg-1) by 172.37%. Fluoride contents in vegetables ranged from 0.01 to 25.21 mg kg-1, with the median value of 1.29 mg kg-1, which was higher than the limits of contaminants in food (1 mg kg-1) by 129.00%, and 53.85% of vegetable samples were contaminated. Leafy vegetables showed a higher tendency of fluoride enrichment compared to non-leafy vegetables. Despite there being no significant health risk to the residents via the intake of vegetables overall, there may be potential health risks from the intake of sweet potato leaves. Based on the SSD model, the ecological safety thresholds of fluoride in local farmland was classified into the suitable for planting category (≤174.13 mg kg-1), safe plant utilization category (174.13-4005.42 mg kg-1), and strict control of planting category (≥4005.42 mg kg-1). These findings will provide valuable insights to facilitate the safe cultivation of local agricultural products and optimize the utilization of soil resources.

Determination of Perfluorooctanoic Acid and Perfluorooctane Sulfonate Water Quality Criteria for Ecosystem Protection of Laguna Lake, Philippines

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are organic chemicals which pose concerns in the environment due to their persistence and bioaccumulative properties. This study used Assessment Factors and Species Sensitivities Distributions to derive specific thresholds to protect the ecosystem in the Laguna Lake, Philippines from risks posed by the toxicity of PFOS and PFOA using available ecotoxicity data for local species. For Assessment Factor method, the U.S. Environmental Protection Agency guideline for the narrative Tier II criteria was suitable based on the available toxicity data with calculated maximum concentration threshold for PFOS and PFOA of 0.51 and 0.75 mg L-1, respectively, and continuous maximum concentration values of 0.06 and 0.08 mg L-1, respectively. For the methods using Species Sensitivity Distribution (SSD), PFOS and PFOA thresholds extrapolated using factors for small datasets were 0.046 and 0.088 mg L-1, respectively. Lastly, PFOS and PFOA Hazardous Concentration (HC5) extrapolated from the weighted average SSD model estimates were 0.061 and 0.078 mg L-1, respectively. The results can serve as the first regulatory and risk assessment basis for aquatic ecosystem protection against risks posed by emerging contaminants in the lake.

Water Quality Criteria and Ecological Risk Assessment of Typical Transition Metals in South Asia.

Transition metal pollution in rivers in South Asia is more serious than in other regions because of the lack of adequate freshwater management measures. Water quality criteria (WQC) for South Asia is urgently needed to protect regional aquatic environments because of the occurrence of transboundary rivers. The present study established non-parametric kernel density estimation species sensitivity distribution (NPKDE-SSD) models and then derived the acceptable hazardous concentration for protection of 95% of all aquatic species (HC5) and WQC of six typical transition metals in South Asia. The results showed that the order of acute and chronic WQC was Mn > Fe > Cd > Zn > Cu > Hg and Cu > Fe > Cd, respectively. A risk assessment of these metals in the Indus River, the Ganges River, the Brahmaputra River, the Meghna River, and the Bagmati River was also carried out. Based on the results, these major rivers in South Asia were highly polluted with transition metals, with significant ecological risks for a large number of aquatic species. This study can contribute to a better understanding of ecological risks in South Asia and provide a scientific basis for the updating of water quality standards and the increase in overall water quality.

Occurrence and ecological risk assessment of 2,2′,4,4′-tetrabromodiphenyl ether and decabromodiphenyl ether in surface waters across China

Polybrominated diphenyl ethers (PBDEs) are efficient brominated flame retardants and are released into various environmental media via usage, recycling and disposal. This study investigated the concentrations and ecological risks of two typical PBDEs, 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) and decabromodiphenyl ether (BDE-209), in surface waters across China from 2011 to 2018. The results showed that the concentration of BDE-209 (8.25 ng L−1) was higher than that of BDE-47 (1.02 ng L−1), and the concentrations of BDE-47 and BDE-209 in the lakes (2.56 ng L−1 and 22.19 ng L−1, respectively) were higher than those in the rivers (0.58 ng L−1 and 7.05 ng L−1, respectively). In addition, the concentration of BDE-209 in the wet season (2.61 ng L−1) was lower than that in the dry season (10.83 ng L−1), whereas the concentration of BDE-47 in the wet season (0.24 ng L−1) was a little lower than that in the dry season (0.99 ng L−1). BDE-47 and BDE-209 concentrations showed a gradual decrease in surface waters across China during the eight-year period. Based on the species sensitivity distribution (SSD) models, the 5% hazardous concentration (HC5) and predicted no-effect concentration (PNEC) values were derived using the acute and chronic toxicity data of BDE-47 and BDE-209. Results showed that the PNEC values based on the acute and chronic toxicity data were 2.08 μg L−1 and 0.52 μg L−1 for BDE-47, respectively and 370 μg L−1 and 0.34 μg L−1 for BDE-209, respectively. The risk quotient (RQ) values of BDE-47 in surface waters across China were far smaller than 0.1 (low ecological risk). Similarly, the RQ values of BDE-209 were also smaller than 0.1, except for those at Baiyangdian Lake and Chaohu Lake, where the probability of 0.1 ≤ RQ < 1.0 (medium ecological risk) was approximately 10% based on 10,000 Monte Carlo simulations.

Development of seawater quality criteria for phenanthrene based on toxicity data of native species in the Bohai Sea.

Phenanthrene (Phe), one of the most commonly detected polycyclic aromatic hydrocarbons, poses a potential threat to marine ecosystems due to its strong toxicity to aquatic organisms. Developing marine water quality criteria (WQC) is critical to effectively control Phe pollution. This study conducted 10 acute toxicity tests and 4 chronic toxicity tests using native species in the Bohai Sea, China and found that the half-lethal/effective concentrations (LC50/EC50) of Phe for all tested organisms were in the range of 0.198-50.142mg/L. Among them, the mysid Neomysis awatschensis was the most sensitive species, and the rotifer Brachionus plicatilis was the least sensitive. In terms of chronic toxicity, the range of no-observed-effect concentrations (NOECs) for the four tested organisms was 0.0156-4.00mg/L. Based on the toxicity data and other data collected from existing databases and literature, the established species sensitivity distribution (SSD) model revealed that the marine WQC for Phe was 39.55μg/L. Furthermore, the reliability of the derived criteria was verified by measuring multiple endpoints of Skeletonema costatum and Brachionus plicatilis after chronic exposure to Phe. Finally, the environmental concentrations of Phe in the Bohai Sea were determined to be 8.0-318ng/L, and the joint probability curve (JPC) results showed that the ecological risk of Phe was acceptable. This study provides a reference for developing seawater quality standards for Phe.

Assessment of soil heavy metal pollution in provinces of China based on different soil types: From normalization to soil quality criteria and ecological risk assessment

Ecological risks can vary dramatically depending on abiotic factors, such as soil properties and the background values of elements. This study developed a framework for an integrated risk assessment system to derive soil quality criteria (SQC) for heavy metals (HMs) applicable to different soil types and to assess ecological risks at a multi-regional scale. Through the construction of normalization and species sensitivity distribution models, 248 SQC values for Cd, Pb, Zn, As, Cu, Cr, Sb, and Ni in 31 Chinese provinces were derived. These SQC considered the soil types and background values of the elements and effectively reduced the uncertainty caused by spatial heterogeneity. Using the derived SQC values, the qualitative and quantitative ecological risks of HMs in the terrestrial environment of China were comprehensively assessed using a three-level ecological risk assessment (ERA) approach. Compared to traditional ERA methods, the new methodology reached a more quantitative conclusion. The mean overall probabilities of ecological risk in China were 2.42 % (Cd), 2.82 % (Pb), 12.17 % (Zn), 14.89 % (As), 10.42 % (Cu), 32.20 %(Cr), and 8.88 % (Ni). The new framework could be useful for the ERA of various soil types.

A QSAR-ICE-SSD model prediction of the PNECs for alkylphenol substances and application in ecological risk assessment for rivers of a megacity.

Alkylphenols (APs) are ubiquitous and generally present in higher residue levels in the environment. The present work focuses on the development of a set of in silico models to predict the aquatic toxicity of APs with incomplete/unknown toxicity data in aquatic environments. To achieve this, a QSAR-ICE-SSD model was constructed for aquatic organisms by combining quantitative structure-activity relationship (QSAR), interspecies correlation estimation (ICE), and species sensitivity distribution (SSD) models in order to obtain the hazardous concentrations (HCs) of selected APs. The research indicated that the keywords "alkylphenol" and "nonylphenol" were most commonly studied. The selected ICE models were robust (R2: 0.70-0.99; p-value < 0.01). All models had a high reliability cross- validation success rates (>75%), and the HC5 predicted with the QSAR-ICE-SSD model was 2-fold than that derived with measured experimental data. The HC5 values demonstrated nearly linear decreasing trend from 2-MP to 4-HTP, while the decreasing trend from 4-HTP to 4-DP became shallower, indicates that the toxicity of APs to aquatic organisms increases with the addition of alkyl carbon chain lengths. The ecological risks assessment (ERA) of APs revealed that aquatic organisms were at risk from exposure to 4-NP at most river stations (the highest risk quotient (RQ) = 1.51), with the highest relative risk associated with 2.9% of 4-NP detected in 82.9% of the sampling sites. The targeted APs posed potential ecological risks in the Yongding and Beiyun River according to the mixture ERA. The potential application of QSAR-ICE-SSD models could satisfy the immediate needs for HC5 derivations without the need for additional in vivo testing.

Development of ecological risk assessment for Diisobutyl phthalate and di-n-octyl phthalate in surface water of China based on species sensitivity distribution model

Phthalic acid esters (PAEs) are commonly used as plasticizer and are emerging concern worldwide for potent adverse effects of aquatic organisms. Certain PAEs were often detected in different environmental matrices but related toxicity data were still lacking to support their risk assessment. The study investigated the acute toxicity of Diisobutyl phthalate (DiBP) and Di-n-octyl phthalate (DnOP) using 6 Chinese resident aquatic organisms from 3 phyla and 6 species and constructed the species sensitivity distribution (SSD) models for ecological risk assessment. Lethal concentration 50% (LC50) ranges of DiBP and DnOP were 4.89–21.45 mg/L and 1.45–1200 mg/L, respectively. The derived acute and chronic predicted no-effect concentrations (PNECs) based on log-normal model of water were 0.54 and 0.04 mg/L for DiBP and 0.23 and 0.05 mg/L for DnOP, respectively. The ERA for DiBP and DnOP in the surface water and sediment of China was conducted. Water samples of Haihe Rive (RQ = 0.41) and Hun River (RQ = 0.16) of DiBP showed medium risk. And sediment samples of Yellow River (RQ = 0.71) and Chao Hu Lake (RQ = 0.42) of DiBP showed medium risk. Meanwhile, the above water and sediment samples (RQ＜0.1) of DnOP showed low risk.

Study on Safe Usage of Agricultural Land in Typical Karst Areas Based on Cd in Soil and Maize: A Case Study of Northwestern Guizhou, China

Cadmium (Cd) is an unnecessary dietary toxin that is harmful to human health. The Cd translocation in soil-crops system varies greatly depending on different soil matrices; therefore, a valuable method that could accurately evaluate soil Cd thresholds needs to be proposed immediately. In the southwestern part of China, a typical karst mountainous area of east Asia, the results of our survey of 492 soil-maize samples in the region showed high Cd accumulation in the soil, with concentrations ranging from 0.07 to 31.95 mg kg−1. The Cd concentrations in maize kernels planted in those fields, however, were quite low, and only 4 samples exceeded the national standard. A comparative study with nonkarst areas revealed a low bioaccumulation factor for soil Cd. This may be interpreted as the weathering soil-forming process of mineral-bearing rock systems, leading to high accumulation as well as low bioavailability of Cd in karst soils. A total of 172 soil-maize samples were evaluated inaccurately by the national standard evaluation procedure, accounting for 34.96% of the total. Therefore, we proposed the species sensitivity distribution model to address this inaccurate assessment. The results show that the hazardous concentrations of 95% and 5% in maize fields were 2.2 and 85.1 mg kg−1 for soil pH ≤ 5.5, 2.5 and 108.5 mg kg−1 for 5.5 &lt; pH ≤ 6.5, and 3.0 and 161.8 mg kg−1 for 6.5 &lt; pH ≤ 7.5, respectively. The total number of unsuitable samples according to the evaluation results decreased from 172 to 2 after modification. Therefore, this result could be considered a more accurate assessment threshold.

Health Risk Assessment and Environmental Benchmark of Heavy Metals in Cultivated Land in Mountainous Area of Northwest Guizhou Province

An extensive investigation of heavy metal (Cd, Hg, As, Pb, and Cr) levels in 137 pairs of soil-maize/rice samples was conducted in cultivated land from a typical karst mountain area in the Northwest of Guizhou Province. A health risk assessment model was used to assess the health risks of those areas, and the environmental benchmarks of heavy metals in soils were evaluated using the species sensitivity distribution (SSD) model. The results showed that the soils of maize and rice were polluted by heavy metals. Cd was the primary pollutant, with an exceeding rate ranging from 87% to 445%. The contaminated level of maize fields was higher than those of rice fields. In contrast, only 3.51% and 13.4% of Cd content in maize kernels and rice grains exceeded the national threshold, and the Cd heavy metal accumulation ability of rice was higher than that of maize. The carcinogenic and non-carcinogenic risks of heavy metals for adults and children in the study area were at a low level. The carcinogenic risk of rice consumption was slightly higher than that of maize, and the health risk to children was higher than that to adults. The results derived from the SSD method showed that the 95% and 5% hazardous concentrations (HC5 and HC95) of maize fields were 0.67 for Cd, 771.99 for As, 40.85 for Pb and 609.88 for Cr mg·kg-1, and HC95were 48.47 for Cd, 159.67 for As, 1735.68 for Pb and 1671.74 for Cr mg·kg-1, respectively. The HC5 values of rice fields were 2.42 for Cd, 8.88 for As, 41.41 for Pb and 27.84 for Cr mg·kg-1, and the HC95 values were 48.47 for Cd, 159.67 for As, 1735.68 for Pb and 1671.74 for Cr mg·kg-1, respectively. The HC5 values of Cd, As, and Cr in maize fields and Cd in rice fields were significantly higher than the soil risk screening values in the current standard, and the HC95 values of the two fields were higher than the soil risk intervened values. The results indicated that the current standard would be too strict to evaluate the actual pollution level of soil heavy metals in this area.