Nutrients, emerging pollutants and pesticides in a tropical urban reservoir: Spatial distributions and risk assessment.

Reservoirs located in urban areas suffer specific pressures related to human activities. Their monitoring, management, and protection requirements differ from reservoirs situated in non-urbanized areas. The objectives of this study were: (a) to determine the concentrations of select pesticides and emerging pollutants (EPs) present in an urban reservoir; (b) to describe their possible spatial distributions; and (c) to quantify the risks for aquatic life and safeguard drinking water supplies. For this purpose, the Guarapiranga reservoir was studied as an example of a multi-stressed urban reservoir in a tropical region. A total of 31 organic compounds (including pesticides, illicit drugs, pharmaceuticals, and endocrine disruptors) were analyzed twice over a period of one year, together with classical indicators of water quality. The physical and chemical data were treated using principal component analysis (PCA) to identify possible temporal or spatial patterns. Risk assessment was performed for biota and drinking water use, comparing maximum environmental concentrations (MECs) with the predicted no-effect concentrations (PNECs) or drinking water quality criteria (DWC), respectively. The results demonstrated the presence of pesticides and EPs, as well as pollution by high levels of nutrients and Chlorophyll a (Chl. a), during the study period. The nutrients and Trophic State Index (TSI) showed gradients in the reservoir and regional distributions, while the pesticides and EPs only clearly showed this pattern in the dry season. The concentrations and distributions of the pesticides and EPs therefore showed seasonality. These findings suggested that the two groups of pollutants (EPs+pesticides and nutrients) possessed different sources and behavior and were not always correlated in the reservoir studied. In the studied period, no risk was observed in raw water for drinking water use, but carbendazim, imidacloprid, and BPA showed risks for the biota in the reservoir.

Ecotoxicological risk assessment of chemical pollution in four Iberian river basins and its relationship with the aquatic macroinvertebrate community status.

Ecotoxicological risk assessment of chemical pollution in four Iberian river basins (Llobregat, Ebro, Júcar and Guadalquivir) was performed. The data set included more than 200 emerging and priority compounds measured at 77 sampling sites along four river basins studied. The toxic units (TU) approach was used to assess the risk of individual compounds and the concentration addition model (CA) to assess the site specific risk. Link between chemical pollution and aquatic macroinvertebrate communities in situ was examined by using four biological indexes; SPEAR ("Species at Risk Index") as the indicator of decline of sensitive species in relation to general organic (SPEARorganic) and pesticides (SPEARpesticides) pollution; and Shannon and Margalef biodiversity indexes. The results of the study suggested that organic chemicals posed the risk of acute effects at 42% of the sampling sites and the risk of chronic effects at all the sites. Metals posed the acute risk at 44% of the sites. The main drivers of the risk were mainly pesticides and metals. However, several emerging contaminants (e.g. the antidepressant drug sertraline and the disinfectant triclosan) were contributing to the chronic effects risk. When risk associated with metals and organic chemicals was compared, the latter dominated in 2010, mainly due to the presence of highly toxic pesticides, while metals did in 2011. Compounds that are not regulated on the European level were posing the risk of chronic effects at 23% of the sites. The decline of sensitive macroinvertebrate taxa expressed in terms of SPEAR index was correlated with the increase of toxic stress related to organic compounds Biodiversity indexes were negatively correlated with the metals and the urban land use type in the catchment.

Assessment of multi-chemical pollution in aquatic ecosystems using toxic units: compound prioritization, mixture characterization and relationships with biological descriptors.

Chemical pollution is typically characterized by exposure to multiple rather than to single or a limited number of compounds. Parent compounds, transformation products and other non-targeted compounds yield mixtures whose composition can only be partially identified by monitoring, while a substantial proportion remains unknown. In this context, risk assessment based on the application of additive ecotoxicity models, such as concentration addition (CA), is rendered somewhat misleading. Here, we show that ecotoxicity risk information can be better understood upon consideration of the probabilistic distribution of risk among the different compounds. Toxic units of the compounds identified in a sample fit a lognormal probability distribution. The parameters characterizing this distribution (mean and standard deviation) provide information which can be tentatively interpreted as a measure of the toxic load and its apportionment among the constituents in the mixture (here interpreted as mixture complexity). Furthermore, they provide information for compound prioritization tailored to each site and enable prediction of some of the functional and structural biological variables associated with the receiving ecosystem. The proposed approach was tested in the Llobregat River basin (NE Spain) using exposure and toxicity data (algae and Daphnia) corresponding to 29 pharmaceuticals and 22 pesticides, and 5 structural and functional biological descriptors related to benthic macroinvertebrates (diversity, biomass) and biofilm metrics (diatom quality, chlorophyll-a content and photosynthetic capacity). Aggregated toxic units based on Daphnia and algae bioassays provided a good indication of the pollution pattern of the Llobregat River basin. Relative contribution of pesticides and pharmaceuticals to total toxic load was variable and highly site dependent, the latter group tending to increase its contribution in urban areas. Contaminated sites' toxic load was typically dominated by fewer compounds as compared to cleaner sites where more compounds contribute.

Analysis of monitoring programmes and their suitability for ecotoxicological risk assessment in four Spanish basins.

Data from four Spanish basin management authorities were analysed. Chemical and biological data from four Spanish basin management authorities were analysed, focusing on three consecutive years. Aims were to i) determine the chemicals most likely responsible for the environmental toxicological risk in the four Spanish basins and ii) investigate the relationships between toxicological risk and biological status in these catchments. The toxicological risk of chemicals was evaluated using the toxic unit (TU) concept. With these data we considered if the potential risk properly reflects the risk to the community or, alternatively, if new criteria should be developed to improve risk assessment. Data study revealed inadequacies in processing and monitoring that should be improved (e.g., site coincidence for chemical and biological sampling). Analysis of the chemical data revealed high potential toxicological risk in the majority of sampling points, to which metals were the main contributors to this risk. However, clear relationships between biological quality and chemical risk were found only in one river. Further investigation of metal toxicity may be necessary, and future analyses are necessary to accurately estimate the risk to the environment.