Patterning ecological risk of pesticide contamination at the river basin scale

Assessment of the impact of chemical pollution on endangered migratory fish in two major rivers of France, including spawning grounds

Water pollution is a one of the most contributors to aquatic biodiversity decline. Consequently, ecological risk assessment methods have been developed to investigate the effects of existing stresses on the environment, including the toxic effects of chemicals. One of the existing approaches to quantify toxic risks is called "Potentially Affected Fraction of species" (PAF), which estimates the potential loss of species within a group of species studied. In this study, the PAF method was applied to the Garonne catchment (southwest France) due to the limited information available on the involvement of water pollution in the decline of diadromous fish populations. This approach was used to quantify the potential toxic risk associated with chemical contamination of water for fish species. The objectives were to quantify this risk (1) in the Garonne and Dordogne rivers and (2) in the spawning grounds of two endangered anadromous fish species: the allis shad and the European sturgeon during the development period of their early life stages. Environmental pollution data was provided for 21 sites within the Garonne catchment between 2007 and 2022, and toxicity data was obtained specifically from freshwater toxicity tests on fish species. Then, for each site and each year, the potential toxic risk for a single substance (ssPAF) and for a mixture of substances (msPAF) was calculated and classified as high (>5 %), moderate (>1 % and < 5 %) or low (<1 %). Potential toxic risks were mostly moderate and mainly associated with: metals > other industrial pollutants and hygiene and care products > agrochemicals. In summary, this study highlights the probable involvement of water contamination on the decline, fate and restoration of diadromous fish populations in the Garonne catchment, focusing notably on the toxic effects on early life stages, a previously understudied topic.

Heterogeneity in biological assemblages and exposure in chemical risk assessment: Exploring capabilities and challenges in methodology with two landscape-scale case studies

Chemical exposure concentrations and the composition of ecological receptors (e.g., species) vary in space and time, resulting in landscape-scale (e.g. catchment) heterogeneity. Current regulatory, prospective chemical risk assessment frameworks do not directly address this heterogeneity because they assume that reasonably worst-case chemical exposure concentrations co-occur (spatially and temporally) with biological species that are the most sensitive to the chemical's toxicity. Whilst current approaches may parameterise fate models with site-specific data and aim to be protective, a more precise understanding of when and where chemical exposure and species sensitivity co-occur enables risk assessments to be better tailored and applied mitigation more efficient. We use two aquatic case studies covering different spatial and temporal resolution to explore how geo-referenced data and spatial tools might be used to account for landscape heterogeneity of chemical exposure and ecological assemblages in prospective risk assessment. Each case study followed a stepwise approach: i) estimate and establish spatial chemical exposure distributions using local environmental information and environmental fate models; ii) derive toxicity thresholds for different taxonomic groups and determine geo-referenced distributions of exposure-toxicity ratios (i.e., potential risk); iii) overlay risk data with the ecological status of biomonitoring sites to determine if relationships exist. We focus on demonstrating whether the integration of relevant data and potential approaches is feasible rather than making comprehensive and refined risk assessments of specific chemicals. The case studies indicate that geo-referenced predicted environmental concentration estimations can be achieved with available data, models and tools but establishing the distribution of species assemblages is reliant on the availability of a few sources of biomonitoring data and tools. Linking large sets of geo-referenced exposure and biomonitoring data is feasible but assessment of risk will often be limited by the availability of ecotoxicity data. The studies highlight the important influence that choices for aggregating data and for the selection of statistical metrics have on assessing and interpreting risk at different spatial scales and patterns of distribution within the landscape. Finally, we discuss approaches and development needs that could help to address environmental heterogeneity in chemical risk assessment.

The spatial-temporal chemical footprint of pesticides in China from 1999 to 2018

The massive use of pesticides brings considerable environmental and human health impacts. This study conducted an overall assessment of the ecological impact of the extensive pesticide use in China from 1999 to 2018 through the Chemical Footprint (ChF) calculation. The results demonstrated that the primary ecological impacts caused by pesticides occurred in the most central and eastern regions in China, e.g., provinces of Shandong, Henan, Hubei, Anhui, and Jiangsu. The northeastern, some southern and central provinces, e.g., Heilongjiang, Jilin, Liaoning, Yunnan, Guangxi, Guangdong, Ningxia, and Shaanxi, got moderate impacts, whereas the northwest regions, e.g., Qinghai, Xinjiang, and Tibet, had much lighter impacts relatively. The agricultural soil in inland areas and surface sea waters in coastal provinces bore the major impacts of the pesticide pollution in China, shared above 80% of the ChF across all environmental compartments. Chlorpyrifos, pymetrozine, fenpropathrin, pyridaben, atrazine, etc., were the pesticides that had the greatest impacts on the ecosystem, which contributed over 95% of the total ChF of pesticides used in China, although the use amount of these pesticides accounted for less than 10% of the total use amount of all pesticides annually. The study also indicated that the overall ChF of pesticide use in China has been declining since 2010, which was corresponding with the control actions of highly hazardous pesticides, especially the elimination of high toxic organophosphorus insecticides during the past decade.

A critical review of effect modeling for ecological risk assessment of plant protection products

A wide diversity of plant protection products (PPP) is used for crop protection leading to the contamination of soil, water, and air, which can have ecotoxicological impacts on living organisms. It is inconceivable to study the effects of each compound on each species from each compartment, experimental studies being time consuming and cost prohibitive, and animal testing having to be avoided. Therefore, numerous models are developed to assess PPP ecotoxicological effects. Our objective was to provide an overview of the modeling approaches enabling the assessment of PPP effects (including biopesticides) on the biota. Six categories of models were inventoried: (Q)SAR, DR and TKTD, population, multi-species, landscape, and mixture models. They were developed for various species (terrestrial and aquatic vertebrates and invertebrates, primary producers, micro-organisms) belonging to diverse environmental compartments, to address different goals (e.g., species sensitivity or PPP bioaccumulation assessment, ecosystem services protection). Among them, mechanistic models are increasingly recognized by EFSA for PPP regulatory risk assessment but, to date, remain not considered in notified guidance documents. The strengths and limits of the reviewed models are discussed together with improvement avenues (multigenerational effects, multiple biotic and abiotic stressors). This review also underlines a lack of model testing by means of field data and of sensitivity and uncertainty analyses. Accurate and robust modeling of PPP effects and other stressors on living organisms, from their application in the field to their functional consequences on the ecosystems at different scales of time and space, would help going toward a more sustainable management of the environment. Graphical Abstract Combination of the keyword lists composing the first bibliographic query. Columns were joined together with the logical operator AND. All keyword lists are available in Supplementary Information at https://doi.org/10.5281/zenodo.5775038 (Larras et al. 2021).

Perceptions and Profiles of Young People Regarding Spa Tourism: A Comparative Study of Students from Granada and Aachen Universities

Spa tourism has undergone important changes in recent decades, actively embracing wellness and wellbeing. However, this transition is taking place in different ways in Europe, and this has led to varying perceptions of thermalism that have little to do with its original conception. The main aim of this study was to analyse current perceptions of spa tourism amongst university students, so as to identify profiles and compare the differences between two study cases: Granada (Spain) and Aachen (Germany). For this purpose, we applied a methodology that combines artificial intelligence techniques with questionnaires containing both quantitative and qualitative variables. This enabled us to identify and characterize a series of profiles, so as to acquire detailed knowledge of the perceptions of these students regarding spa tourism in Granada and Aachen. On the basis of the results, the interviewees were grouped together into seven profiles from which we deduced that young Germans from Aachen visit spas more frequently and have a more realistic perception of the thermal sector than young Spanish people from Granada. This situation could limit present and future demand for spas in southern Spain. With this in mind, in this paper we present an updated assessment of the demand for spas amongst university students, in order to design effective geomarketing strategies in two cities with long spa traditions.

Subchronic exposure to high-density polyethylene microplastics alone or in combination with chlortoluron significantly affected valve activity and daily growth of the Pacific oyster, Crassostrea gigas

Nowadays, pesticides and microplastics (MPs) are commonly found in coastal waters worldwide. Due to their widespread use, their persistence and toxicity, they may induce adverse effects on physiology and behaviour of marine organisms such as the Pacific oyster (Crassostrea gigas). This study explored the growth and valve activity of juvenile oysters exposed for 24 days to two frequently detected pollutants in the Pertuis Charentais (South West, France): a herbicide (chlortoluron, 85 µg.L^-1) and high-density polyethylene microparticles (HDPE 20-25 µm, 112 MP.mL^-1) alone or in combination (cocktail condition; 97 µg.L^-1 of chlortoluron + 108 MP. mL^-1). The valve activity of juvenile oysters recorded by using a High Frequency and Non-Invasive valvometer (HFNI) was characterized by three parameters: the number of valve micro-closures (VMC), the Valve Opening Amplitude (VOA), and the Valve Opening Duration (VOD). Additionally, daily shell growth and the oyster daily rhythm were assessed. The exposure to MPs of oysters led to a significant increase of VMC and a decrease of VOD and shell growth. The exposure to chlortoluron showed a significant increase of VOA and a decrease of VMC. In combination with MPs, chlortoluron still increased VOA and decreased VMC but also reduced the shell growth. Chronobiological analysis did not reveal any effects on the daily rhythm of both contaminants. This work highlighted significant effects of high environmental concentrations of MPs and Chlortoluron on the behaviour and growth of the Pacific oyster.

Biological and chemical monitoring of the ecological risks of pesticides in Lake Ziway, Ethiopia

Lake Ziway, a freshwater lake located in Ethiopia, is under the pressure of pesticide and nutrient pollution due to agricultural activity and urbanization. This study has analysed concentrations of insecticides, fungicides and nutrients in water and sediment samples of Lake Ziway taken in the wet and dry season at 13 sites expected to be under different environmental stress and assessed their expected ecological impacts. Malathion, dimethoate, metalaxyl, diazinon, chlorpyrifos, fenitrothion and endosulfan were detected in more than half of the water samples, while diazinon, α-cypermethrin and endosulfan were frequently detected (>25%) in sediment samples. Higher levels of physicochemical parameters were observed at sample locations proximate to agricultural and urban activities. Risk quotients (RQ) and multi-substance Potentially Affected Fraction (msPAF_RA) were calculated to assess the ecological risk of individual and mixture of pesticides, respectively. The majority of the pesticides detected in the water of the lake showed a potential acute risk (RQ > 1), specifically the insecticides chlorpyrifos, λ-cyhalothrin and α-cypermethrin for which high potential acute risks were calculated using a 2nd tier risk assessment. Levels of pesticides in sediment showed low ecological risks. Arthropods and fishes are expected to be highly affected by mixtures of pesticides (msPAF_RA = < 1-80%) detected at locations that are proximate to smallholders' farms, and receive largescale farms' wastewater and at sites where inflow rivers join the lake. Macroinvertebrates based redundancy analysis showed the effectiveness of EPT richness to assess ecological status of the lake. Training for smallholder farmers on pesticides safety and usage, and implementation of improved effluent management mechanisms by floriculture farms are urgently needed intervention measures to reduce the pollution.

Individual and mixture toxicity of carbofuran and diuron to the protozoan Paramecium caudatum and the cladoceran Ceriodaphnia silvestrii

The toxicity of the insecticide carbofuran and herbicide diuron (individually and in mixture) to the invertebrates Paramecium caudatum and Ceriodaphnia silvestrii was evaluated. Acute and chronic toxicity tests were carried out with the diuron and carbofuran active ingredients and their commercial products, Diuron Nortox® 500 SC and Furadan® 350 SC, respectively. Individual toxicity tests showed that C. silvestrii was more sensitive to both carbofuran and diuron than P. caudatum. In single exposures, both pesticides caused adverse effects to C. silvestrii in environmentally relevant concentrations (48 h EC₅₀ = 0.001 mg L^-1 and 8 d LOEC = 0.00038 mg L^-1 for formulated carbofuran; 8 d LOEC < 0.05 mg L^-1 for formulated diuron). For P. caudatum, carbofuran and diuron in single exposures were only slightly toxic (24 h IC₅₀ = 5.1 mg L^-1 and 6.9 mg L^-1 for formulated carbofuran and diuron, respectively). Acute and chronic exposures to diuron and carbofuran mixtures caused significant deviations of the toxicity predicted by the Concentration Addition and Independent Action reference models for both test species. For the protozoan P. caudatum, a dose-dependent deviation was verified for mortality, with synergism caused mainly by carbofuran and antagonism caused mainly by diuron. For protozoan population growth, however, an antagonistic deviation was observed when the active ingredient mixtures were tested. In the case of C. silvestrii, antagonism at low concentrations and synergism at high concentrations were revealed after acute exposure to active ingredient mixtures, whereas for reproduction an antagonistic deviation was found. Commercial formulation mixtures presented significantly higher toxicity than the active ingredient mixtures. Our results showed that carbofuran and diuron interact and cause different toxic responses than those predicted by the individually tested compounds. Their mixture toxicity should therefore be considered in risk assessments as these pesticides are likely to be present simultaneously in edge-of-field waterbodies.

Occurrence, source estimation and risk assessment of pharmaceuticals in the Chaobai River characterized by adjacent land use

This study investigated the occurrence of 27 pharmaceuticals with diverse physicochemical properties in a year-long monitoring campaign in the Chaobai River, China. The correlation between the distribution of pharmaceuticals in the river and the adjacent sources was elucidated. The results indicate that the agriculture area was the most polluted area with a median summed pharmaceutical concentration of 225.3 ng L^-1, followed by the urban area and the mountain area with the corresponding values of 136.9 and 29.9 ng L^-1, respectively. In terms of individual compounds, 22 out of 27 compounds were detected with concentrations ranging from <1 to 1972 ng L^-1. Caffeine, carbamazepine, azithromycin, bezafibrate, metoprolol, sulfadiazine, sulfamethoxazole, clarithromycin, erythromycin, roxithromycin, and trimethoprim were pharmaceuticals with relatively high levels, with median concentrations ranging from 3.3 to 25.6 ng L^-1 and detection frequencies ranging from 40% to 97%. Higher concentrations were mainly observed during cold seasons, with mean concentrations 1 to 52 times as high as those during warm seasons. Spatial analysis reveals that the pharmaceutical concentrations in different areas were impacted by different sources. A wastewater treatment plant was an important source in the urban area, while the agriculture area was impacted by various treated and untreated wastewater sources. The species sensitivity distribution model and risk quotient (RQ) method were combined in the ecological risk assessment. The results indicate that the multi-substance potentially affected fraction (msPAF) values of the sampling sites were below 0.04%, whereas nearly half of RQ values were higher than 1. Caffeine was proposed as a priority compound due to its high contribution rate (i.e., 79%) to the cumulative msPAF value, which implies that increased control and management of untreated wastewater sources along the Chaobai River is necessary.

Application of a Self-Organizing Map of Isotopic and Chemical Data for the Identification of Groundwater Recharge Sources in Nasunogahara Alluvial Fan, Japan

Paddy rice fields on an alluvial fan not only use groundwater for irrigation but also play an important role as groundwater recharge sources. In this study, we investigated the spatial distribution of isotopic and hydrochemical compositions of groundwater in the Nasunogahara alluvial fan in Japan and applied a self-organizing map (SOM) to characterize the groundwater. The SOM assisted with the hydrochemical and isotopic interpretation of the groundwater in the fan, and clearly classified the groundwater into four groups reflecting the different origins. Two groundwater groups with lower isotopic ratios of water than the mean precipitation values in the fan were influenced by the infiltration of river water flowing from higher areas in the catchments and were differentiated from each other by their Na+ and Cl− concentrations. A groundwater group with higher isotopic ratios was influenced by the infiltration of paddy irrigation water that had experienced evaporative isotopic enrichment. Groundwater in the fourth group, which was distributed in the upstream area of the fan where dairy farms dominated, showed little influence of recharge waters from paddy rice fields. The findings of this study will contribute to proper management of the groundwater resources in the fan.

Risk assessment framework for nitrate contamination in groundwater for regional management

Nitrate pollution in groundwater is now one of the most important environmental problems all over the world. For this purpose, a new framework for risk screening and assessment of groundwater nitrate was proposed according to source-pathway-receptor-response model to provide basic for defining environmental management strategies. The framework is composed of groundwater relative risk model (RRM), groundwater contamination risk assessment (CRA), and human health risk assessment (HHRA). The framework is applied in the lower Liaohe river basin plain, northeast of China. The results showed that the priority area with high groundwater relative risk in study area was successfully screened by RRM. Furthermore, the sites with high human health risk for public by groundwater nitrate were selected as hazardous areas. This framework promotes systematic integration of risk assessment of groundwater nitrate and expands traditional research on groundwater management from a scale-based approach to crucial insights into pollution.

Decision Model for Predicting Social Vulnerability Using Artificial Intelligence

Social vulnerability, from a socio-environmental point of view, focuses on the identification of disadvantaged or vulnerable groups and the conditions and dynamics of the environments in which they live. To understand this issue, it is important to identify the factors that explain the difficulty of facing situations with a social disadvantage. Due to its complexity and multidimensionality, it is not always easy to point out the social groups and urban areas affected. This research aimed to assess the connection between certain dimensions of social vulnerability and its urban and dwelling context as a fundamental framework in which it occurs using a decision model useful for the planning of social and urban actions. For this purpose, a holistic approximation was carried out on the census and demographic data commonly used in this type of study, proposing the construction of (i) a knowledge model based on Artificial Neural Networks (Self-Organizing Map), with which a demographic profile is identified and characterized whose indicators point to a presence of social vulnerability, and (ii) a predictive model of such a profile based on rules from dwelling variables constructed by conditional inference trees. These models, in combination with Geographic Information Systems, make a decision model feasible for the prediction of social vulnerability based on housing information.

Urban Shape and Built Density Metrics through the Analysis of European Urban Fabrics Using Artificial Intelligence

In recent decades, the concept of urban density has been considered key to the creation of sustainable urban fabrics. However, when it comes to measuring the built density, a difficulty has been observed in defining valid measurement indicators universally. With the intention of identifying the variables that allow the best characterization of the shape of urban fabrics and of obtaining the metrics of their density, a multi-variable analysis methodology from the field of artificial intelligence is proposed. The main objective of this paper was to evaluate the capacity and interest of such a methodology from standard indicators of the built density, measured at various urban scales, (i) to cluster differentiated urban profiles in a robust way by assessing the results statistically, and (ii) to obtain the metrics that characterize them with an identity. As a case study, this methodology was applied to the state of the art European urban fabrics (N = 117) by simultaneously integrating 13 regular parameters to qualify urban shape and density. It was verified that the profiles obtained were more robust than those based on a limited number of indicators, evidencing that the proposed methodology offers operational opportunities in urban management by allowing the comparison of a fabric with the identified profiles.

Identifying key landscape pattern indices influencing the ecological security of inland river basin: The middle and lower reaches of Shule River Basin as an example

Landscape pattern evolution leads to changes of landscape spatial structure, which are intuitively reflected in the changes of ecosystem structure and composition and finally affect ecological security. In this paper, we assessed the spatiotemporal variation of the ecological security and landscape pattern of the middle and lower reaches of Shule River Basin in 1987-2015. Further, we analyzed the correlation between the ecological security and landscape pattern of the study region and correlation coefficients were calculated. On this basis, the key landscape pattern indices influencing the ecological security of the study region were identified. This may provide useful information for ecological regulation and design. The results show that: (1) From 1987 to 2015, the ecological security in the middle and lower reaches of the Shule River Basin was of medium or low level, showing periodic "U" shaped fluctuations, and the fluctuation period was gradually shortened. In addition, there was an overall spatial pattern of "high ecological security in the west, middle and south and low ecological security in the east". (2) The landscape pattern showed clear stage characteristics. The complexity of landscape pattern increased from 1987 to 1996 and decreased after 1996. (3) Landscape size, shape, quantity, type and spatial configuration had important impacts on ecological security and showed significant temporal variation. In a period when the influence of human activities was weak, ecological security was mainly related to landscape area indices. With increase in human activities, landscape shape, fragmentation and connectivity changed greatly, which led to changes in the structure and composition of ecosystem, thus finally affecting ecological security.

Sensitivities of three tropical indigenous freshwater invertebrates to single and mixture exposures of diuron and carbofuran and their commercial formulations

As compared to their temperate counterparts, few toxicity tests have been conducted so far into the evaluation of the sensitivity of indigenous tropical species to pesticides. Especially mixture toxicity assessments appear to be scarce. To contribute to increase our knowledge in this arena, we evaluated the acute toxicity of diuron and carbofuran and their mixtures to the neotropical oligochaetes Allonais inaequalis and Dero furcatus, and the ostracod Strandesia trispinosa. Tests were performed with both the pure active ingredients, as well as their formulated products. The toxicity of the latter to the three test organisms was generally greater than that of the pure active ingredients, although absolute differences were rather small. The sensitivity of the indigenous species was slightly greater than temperate test species from the same taxonomic groups. The concentration addition conceptual model best described the results of the mixture toxicity data. Derived deviations of this model appeared to be dependent on the test organism and as to whether the pesticides were applied as active ingredients or their commercial products. Reported field concentrations of the two pesticides indicate risks to freshwater biota, especially if they are both present. The test species used in the present study are concluded to be suitable candidates as surrogate test organisms in local pesticide risk evaluations.

Acute and chronic toxicity of diuron and carbofuran to the neotropical cladoceran Ceriodaphnia silvestrii

In order to contribute to the increase of the body of knowledge on the sensitivity of tropical indigenous species to pesticides, acute and chronic toxicity tests were conducted with the neotropical cladoceran Ceriodaphnia silvestrii. Tests were carried out with the active ingredients diuron and carbofuran and one of their commercial formulations, the Diuron Nortox® 500 SC and the Furadan® 350 SC, respectively. For carbofuran, the active ingredient was more toxic than the commercial product, whereas for diuron, the commercial product appeared more toxic. In addition, hormetic effects on fertility were recorded for intermediate diuron concentrations. Acute and chronic toxicity data indicated that C. silvestrii was among the most sensitive invertebrate species for both test compounds. Based on concentrations measured in Brazilian water bodies, these compounds represent ecological risks for causing direct and indirect toxic effects on C. silvestrii and other aquatic organisms. Our results support previous claims on the advantages of using native species to better tune ecological risk assessment of chemicals in tropical ecosystems.

Effects of diuron and carbofuran and their mixtures on the microalgae Raphidocelis subcapitata

In aquatic environments, organisms are often exposed to mixtures of several pesticides. In this study, the effects of carbofuran and diuron and their mixtures on the microalgae Raphidocelis subcapitata were investigated. For this purpose, toxicity tests were performed with the single compounds (active ingredients and commercial formulations) and their combinations (only active ingredients). According to the results, the toxicity of active ingredients and their commercial formulations to R. subcapitata was similar. In the single exposures, both carbofuran and diuron inhibited significantly the R. subcapitata growth and caused physiological (chlorophyll a content) and morphological (complexity and cell size) changes in cells, as captured by flow cytometry single-cell properties. Regarding the mixture toxicity tests, data fitted to both reference models, concentration addition (CA) and independent action (IA), and evidenced significant deviations. After the CA fitting, dose-ratio dependent deviation had the best fit to the data, demonstrating synergism caused mainly by diuron and antagonism caused mainly by carbofuran. After fitting the IA model, a synergistic deviation represented the best fit for the diuron and carbofuran mixtures. In general, the two reference models indicated the occurrence of synergism in the mixtures of these compounds, especially when diuron was the dominant chemical in the combinations. The increased toxicity caused by the mixture of these pesticides could pose a greater environmental risk for phytoplankton. Thus, exposure to diuron and carbofuran mixtures must also be considered in risk assessments, since the combination of these compounds may result in more severe effects on algae population growth than single exposures.

Phenotypic variation as an indicator of pesticide stress in gudgeon: Accounting for confounding factors in the wild

The response of organisms to environmental stress is currently used in the assessment of ecosystem health. Morphological changes integrate the multiple effects of one or several stress factors upon the development of the exposed organisms. In a natural environment, many factors determine the patterns of morphological differentiation between individuals. However, few studies have sought to distinguish and measure the independent effect of these factors (genetic diversity and structure, spatial structuring of populations, physical-chemical conditions, etc.). Here we investigated the relationship between pesticide levels measured at 11 sites sampled in rivers of the Garonne river basin (SW France) and morphological changes of a freshwater fish species, the gudgeon (Gobio gobio). Each individual sampled was genotyped using 8 microsatellite markers and their phenotype characterized via 17 morphological traits. Our analysis detected a link between population genetic structure (revealed by a Bayesian method) and morphometry (linear discriminant analysis) of the studied populations. We then developed an original method based on general linear models using distance matrices, an extension of the partial Mantel test beyond 3 matrices. This method was used to test the relationship between contamination (toxicity index) and morphometry (PST of morphometric traits), taking into account (1) genetic differentiation between populations (FST), (2) geographical distances between sites, (3) site catchment area, and (4) various physical-chemical parameters for each sampling site. Upon removal of confounding effects, 3 of the 17 morphological traits studied were significantly correlated with pesticide toxicity, suggesting a response of these traits to the anthropogenic stress. These results underline the importance of taking into account the different sources of phenotypic variability between organisms when identifying the stress factors involved. The separation and quantification of the independent effect of such factors provides an interesting outlook regarding the use of these evaluation metrics as indicators of ecosystem health.

Risk assessment of agricultural pesticides in water, sediment, and fish from Owan River, Edo State, Nigeria

The distribution of pesticides in water, sediments, Clarias gariepinus, and Tilapia zilli from the Owan River was investigated to evaluate the pollution status and potential hazard in the river system. A total of 16 pesticides were analyzed using gas chromatography (GC) equipped with electron capture detector (ECD). The concentration of pesticide residues ranged from ND to 0.43 μg/l for water samples, 0.82 to 2.14 μg/kg/dw for sediment, 0.04 to 2.34 μg/kg/ww for C. gariepinus, and 0.02 to 1.73 μg/kg/ww for T. zilli. High concentrations of organochlorine pesticides, specifically benzenehexachloride (α-BHC, γ-BHC, and β-BHC) observed in all environmental media, are an indication of the current illegal use of banned pesticides for agricultural activities in the region. Analysis of data showed a strong correlation (r (2) = 0.7) between total organic carbon (TOC) and total pesticide residues in sediment samples. Meanwhile, risk quotient estimates for heptachlor epoxide, dieldrin, endrin, dichlorodiphenyltrichloroethane (4,4'-DDT), endosulfan I, endosulfan II, endosulfan aldehyde, and phosphomethylglycine showed potential risk to aquatic organism under observed mean concentrations (risk quotient (RQ) ≥ 1). Estimated average daily intake (EADI) for organochlorine pesticides (γ-BHC, heptachlor epoxide, aldrin, dieldrin, and endrin) was above their respective acceptable average daily intake (ADI), while hazard quotient for each of these pesticides was above the unity value (1). This indicates that there is a potential cancer risk for the local residents with life time consumption of pesticide-contaminated fish.

Predicting the aquatic risk of realistic pesticide mixtures to species assemblages in Portuguese river basins

Although pesticide regulatory tools are mainly based on individual substances, aquatic ecosystems are usually exposed to multiple pesticides from their use on the variety of crops within the catchment of a river. This study estimated the impact of measured pesticide mixtures in surface waters from 2002 and 2008 within three important Portuguese river basins ('Mondego', 'Sado' and 'Tejo') on primary producers, arthropods and fish by toxic pressure calculation. Species sensitivity distributions (SSDs), in combination with mixture toxicity models, were applied. Considering the differences in the responses of the taxonomic groups as well as in the pesticide exposures that these organisms experience, variable acute multi-substance potentially affected fractions (msPAFs) were obtained. The median msPAF for primary producers and arthropods in surface waters of all river basins exceeded 5%, the cut-off value used in the prospective SSD approach for deriving individual environmental quality standards. A ranking procedure identified various photosystem II inhibiting herbicides, with oxadiazon having the relatively largest toxic effects on primary producers, while the organophosphorus insecticides, chlorfenvinphos and chlorpyrifos, and the organochloride endosulfan had the largest effects on arthropods and fish, respectively. These results ensure compliance with European legislation with regard to ecological risk assessment and management of pesticides in surface waters.

Behavioral response of juvenile rainbow trout exposed to an herbicide mixture

Fish are capable of sensing water-borne chemicals at sub-lethal concentrations. Inadequate behavioral responses to physiological and environmental stimuli owing to adverse effects of aquatic toxicants can have serious implications for survival. In this study we exposed juvenile rainbow trout (Oncorhynchus mykiss) during 5 days to a low-concentration mixture of three co-occurring herbicides: atrazine, linuron and metolachlor, at maximum concentrations of 4.5, 4.9 and 13.4 μg L(-1), respectively. Our hypothesis was that fish behavior - swimming activity and interactions between individuals - would be modified due to exposure to the mixture. We studied these behaviors by observing fish twice-daily throughout the exposure period at 30-s intervals for 5 min, registering the vertical distribution of fish in the water column and the number of agoniztic acts between all individuals. Fish exposed to the mixture of herbicides were hypoactive and spent more time in the lower parts of the aquaria in comparison to non-exposed controls, reflecting inhibited swimming activity. Average swimming height of exposed fish decreased significantly with the number of agoniztic acts, whilst in control groups there was no significant relationship between the two behaviors. Overall, behavior of fish exposed for a short time to the herbicide mixture was altered in comparison to control-fish behavior. The behavioral endpoints chosen here were easily observed, simple to quantify, and of ecological relevance.

Developing a foundation for eco-epidemiological assessment of aquatic ecological status over large geographic regions utilizing existing data resources and models

Eco-epidemiological studies utilizing existing monitoring program data provide a cost-effective means to bridge the gap between the ecological status and chemical status of watersheds and to develop hypotheses of stressor attribution that can influence the design of higher-tier assessments and subsequent management. The present study describes the process of combining existing data and models to develop a robust starting point for eco-epidemiological analyses of watersheds over large geographic scales. Data resources from multiple federal and local agencies representing a range of biological, chemical, physical, toxicological, and other landscape factors across the state of Ohio, USA (2000-2007), were integrated with the National Hydrography Dataset Plus hydrologic model (US Environmental Protection Agency and US Geological Survey). A variety of variable reduction, selection, and optimization strategies were applied to develop eco-epidemiological data sets for fish and macroinvertebrate communities. The relative importance of landscape variables was compared across spatial scales (local catchment, watershed, near-stream) using conditional inference forests to determine the scales most relevant to variation in biological community condition. Conditional inference forest analysis applied to a holistic set of environmental variables yielded stressor-response hypotheses at the statewide and eco-regional levels. The analysis confirmed the dominant influence of state-level stressors such as physical habitat condition, while highlighting differences in predictive strength of other stressors based on ecoregional and land-use characteristics. This exercise lays the groundwork for subsequent work designed to move closer to causal inference.

Do predictions from Species Sensitivity Distributions match with field data?

Species Sensitivity Distribution (SSD) is a statistical model that can be used to predict effects of contaminants on biological communities, but only few comparisons of this model with field studies have been conducted so far. In the present study we used measured pesticides concentrations from streams in Germany, France, and Finland, and we used SSD to calculate msPAF (multiple substance potentially affected fraction) values based on maximum toxic stress at localities. We compared these SSD-based predictions with the actual effects on stream invertebrates quantified by the SPEARpesticides bioindicator. The results show that the msPAFs correlated well with the bioindicator, however, the generally accepted SSD threshold msPAF of 0.05 (5% of species are predicted to be affected) severely underestimated the observed effects (msPAF values causing significant effects are 2-1000-times lower). These results demonstrate that validation with field data is required to define the appropriate thresholds for SSD predictions.

Validation of the species sensitivity distribution in retrospective risk assessment of herbicides at the river basin scale-the Scheldt river basin case study

Species sensitivity distribution (SSD) is commonly used in prospective risk assessment to derive predicted no-effect concentrations, toxicity exposure ratios, and environmental quality standards for individual chemicals such as pesticides. The application of SSD in the retrospective risk assessment of chemical mixtures at the river basin scale (i.e., the estimation of "multiple substance potentially affected fractions" [msPAFs]) has been suggested, but detailed critical assessment of such an application is missing. The present study investigated the impact of different data validation approaches in a retrospective model case study focused on seven herbicides monitored at the Scheldt river basin (Belgium) between 1998 and 2009. The study demonstrated the successful application of the SSD approach. Relatively high impacts of herbicides on aquatic primary producers were predicted. Often, up to 40 % of the primary producer communities were affected, as predicted by chronic msPAF, and in some cases, the predicted impacts were even more pronounced. The risks posed by the studied herbicides decreased during the 1998-2009 period, along with decreasing concentrations of highly toxic pesticides such as simazine or isoproturon. Various data validation approaches (the removal of duplicate values and outliers, the testing of different exposure durations and purities of studied herbicides, etc.) substantially affected SSD at the level of individual studied compounds. However, the time-consuming validation procedures had only a minor impact on the outcomes of the retrospective risk assessment of herbicide mixtures at the river basin scale. Selection of the appropriate taxonomic group for SSD calculation and selection of the species-specific endpoint (i.e., the most sensitive or average value per species) were the most critical steps affecting the final risk values predicted. The present validation study provides a methodological basis for the practical use of SSD in the retrospective risk assessment of chemical mixtures.

Development of a relative risk model for evaluating ecological risk of water environment in the Haihe River Basin estuary area

Ecological risk assessment for water environment is significant to water resource management of basin. Effective environmental management and systems restoration such as the Haihe River Basin require holistic understanding of the relative importance of various stressor-related impacts throughout the basin. As an effective technical tool for evaluating the ecological risk, relative risk model (RRM) was applied in regional scale successfully. In this study, the risk transfer from upstream of basin was considered and the RRM was developed through introducing the source-stressor-habitat exposure filter (SSH), the endpoint-habitat exposure filter (EH) and the stressor-endpoint effect filter (SE) to reflect the meaning of exposure and effect more explicit. Water environment which includes water quality, water quantity and aquatic ecosystems was selected as the assessment endpoints. We created a conceptual model which depicting potential and effect pathways from source to stressor to habitat to endpoint. The Haihe River Basin estuary (HRBE) was selected as the model case. The results showed that there were two low risk regions, one medium risk region and two high risk regions in the HRBE. The results also indicated that urbanization was the biggest source, the second was shipping and the third was industry, their risk scores are 5.65, 4.71 and 3.68 respectively. Furthermore, habitat destruction was the largest stressor with the risk scores (2.66), the second was oxygen consuming organic pollutants (1.75) and the third was pathogens (1.75). So these three stressors were the main influencing factors of the ecological pressure in the study area. For habitats, open waters (9.59) and intertidal mudflat were enduring the bigger pressure and should be taken considerable attention. Ecological service values damaged (30.54) and biodiversity decreased were facing the biggest risk pressure.

Water toxicity assessment and spatial pollution patterns identification in a Mediterranean River Basin District. Tools for water management and risk analysis

In compliance with the requirements of the EU Water Framework Directive, monitoring of the ecological and chemical status of Catalan river basins (NE Spain) is carried out by the Catalan Water Agency. The large amount of data collected and the complex relationships among the environmental variables monitored often mislead data interpretation in terms of toxic impact, especially considering that even pollutants at very low concentrations might contribute to the total toxicity. The total dataset of chemical monitoring carried out between 2007 and 2008 (232 sampling stations and 60 pollutants) has been analyzed using sequential advanced modeling techniques. Data on concentrations of contaminants in water were pre-treated in order to calculate the bioavailable fraction, depending on substance properties and local environmental conditions. The resulting values were used to predict the potential impact of toxic substances in complex mixtures on aquatic biota and to identify hot spots. Exposure assessment with Species Sensitivity Distribution (SSD) and mixture toxicity rules were used to compute the multi-substances Potentially Affected Fraction (msPAF). The combined toxicity of the pollutants analyzed in the Catalan surface waters might potentially impact more than 50% of the species in 10% of the sites. In order to understand and visualize the spatial distribution of the toxic risk, Self Organising Map (SOM), based on the Kohonen's Artificial Neural Network (ANN) algorithm, was applied on the output data of these models. Principal Component Analysis (PCA) was performed on top of Neural Network results in order to identify main influential variables which account for the pollution trends. Finally, predicted toxic impacts on biota have been linked and correlated to field data on biological quality indexes using macroinvertebrate and diatom communities (IBMWP and IPS). The methodology presented could represent a suitable tool for water managers in environmental risk assessment and management.