Impact of copper sulfate application at an urban Brazilian reservoir: A geostatistical and ecotoxicological approach

Abstract

A landscape ecotoxicology approach was used to assess the spatial distribution of copper in the recent bottom sediment (surficial sediment) of a Brazilian subtropical reservoir (the Guarapiranga reservoir) and its potential ecotoxicological impacts on the reservoir ecosystem and the local society. We discuss the policies and procedures that have been employed for the management of this reservoir over the past four decades. Spatial heterogeneity in the reservoir was evaluated by means of sampling design and statistical analysis based on kriging spatial interpolation. The sediment copper concentrations have been converted into qualitative categories in order to interpret the reservoir quality and the impacts of management policies. This conversion followed the Canadian Water Framework Directive (WFD) ecotoxicological concentration levels approach, employing sediment quality guidelines (SQGs). The SQG values were applied as the copper concentration thresholds for quantitative-qualitative conversion of data for the surficial sediment of the Guarapiranga. The SQGs used were as follows: a) interim sediment quality guideline (ISQG), b) probable effect level (PEL), and c) regional reference value (RRV). The quantitative results showed that the spatial distribution of copper in the recent bottom sediment reflected the reservoir's management policy and the copper application protocol, and that the copper concentrations varied considerably, ranging from virtually-zero to in excess of 3g/kg. The qualitative results demonstrated that the recent bottom sediment was predominantly in a bad or very bad condition, and could therefore have impacts on the local society and the ecosystem. It could be concluded that the management policy for this reservoir was mainly determined by the desire to minimize short-term costs, disregarding long-term socioeconomic and environmental consequences.

Metals and limnological variables in an urban reservoir: compartmentalization and identification of potential impacted areas

“…This practice has resulted in concentrations of copper in sediments up to 46-fold (Pompêo et al 2013) background, and up more than tenfold the PEL (probable effect level-137 mg kg −1 ) value for copper, which suggest toxicity is likely to occur in sediments (Leal et al 2017). Leal et al (2017) evaluated copper concentrations along Guarapiranga sediments and through a geostatistical approach estimated the sediment copper stock in the reservoir. The stock was estimated in a value of 1158.85 t (copper) , corresponding to 11 years of copper sulfate application.…”

Bench-scale assessment of three copper-based algaecide products for cyanobacteria management in source water

“…Although not all HABs are toxic, the excess biomass is still problematic for the aquatic system [7,12,33]. The frequency, magnitude, and toxicity of blooms are expected to increase as the impacts from climate change worsen [20,26,31,35], indicating a critical demand to increase the understanding of cHABs and provide best management practices to ensure safe access to potable water. It is important to know the site-specific system parameters (i.e., nutrient levels, pH, phytoplankton population dynamics, etc.)…”

“…There are many new and modified copper-based algaecides entering the market to meet the demand for mitigating cHABs. The EPA limits the maximum amount of copper (1 mg/L) that can be applied as the active ingredient as it is toxic to nontarget aquatic organisms [4,20]. The exact time that the copper will remain in the applied area and water column will depend on many factors (water chemistry, weather, etc.).…”

“…The exact time that the copper will remain in the applied area and water column will depend on many factors (water chemistry, weather, etc.). Laboratory and field studies have found that the Cu 2+ concentration is elevated within the water column for only 2-3 h [20,21]. The Cu 2+ ion interacts with aqueous carbonate and biocarbonate ions to form a copper carbonate precipitant that drops out of the water column [9,30].…”

“…The long-term use of copper-based algaecides in large quantities increases the risk of eco-toxicological affects and copper accumulation in the sediment [20,28]. Copper accumulation in sediment can be problematic, since concentrations as low as 40 μg/L exhibit a toxic effect on fish [20] and 60 mg/kg copper was toxic to 22 different prokaryotes [29]. The adverse risks of copper accumulation in sediments from algaecide applications are greatly influenced by site-specific sediment characteristics (sediment type, biogeochemistry, organic content quantity/ quality, available ligands, etc.).…”