Potencial tóxico da água intersticial de lagoas costeiras e água subterrânea sobre caenorhabditis elegans, Osório - Rio Grande do Sul

Abstract

Coastal lakes provide several environmental services both to local communities and tourists, especially during summer. Osório city’s 23 lakes are used for leisure activities, fishery, crops irrigation, and public supply. As a result, they are subject to different anthropic impacts. In water bodies receiving wastewater, a complex mixture of pollutants tends to get accumulated in the bottom sediment over time. More and more, groundwater is becoming a relevant source for population supply, since increasing pollution amounts restrict surface water use. In Osório region, little is known about groundwater quality. Hence, this study aimed to provide a diagnosis about coastal lakes toxicity based on analysis of the lakes’ sediment pore water and groundwater. Concentrations of sixteen metals (Al, Ba, Cd, Ca, Pb, Co, Cu, Cr, Fe, Mg, Mn, Hg, Ni, K, Ag and Zn) in pore water and groundwater were determined using procedures described in Standard Methods 21, EPA 245-1, EPA 3050/ICPOES and EPA 7471. Lakes and groundwater toxic potential were evaluated by exposing the bioindicator Caenorhabditis elegans to seven sediment pore water samples and 30 well water samples. Sampling took place between May 2015 and January 2016, encompassing four seasons. Toxicity rates were estimated by growth and reproduction endpoints (ISO 10782/2010). Data were analyzed using IBM Statistics SPSS 22 software. The chronic toxicity essay results suggest that pore water samples do not inhibit C. elegans growth, but affect its reproduction. These deleterious effects could either be related to the presence of metals, a fact already reported for other coastal freshwater lakes, or to unidentified compounds. Hormetic effects on C. elegans growth, observed in all lake samples, may be caused by metabolic changes stemming from exposure to contaminated water. The results show that water from some of the studied wells is unfit for human consumption due it chronic toxicity to C. elegans and metals (Fe, Mn and Al) exceeding the thresholds established by Brazil’s Ministry Health Ordinance (n.2914/11) putting in evidence the groundwater critical situation and threatening this resource sustainability. C. elegans proved its efficiency in detecting pore water and groundwater toxicity, offering a practical, rapid, and easy-to-interpret response for chronic toxicity evaluation. The study’s findings highlight the need for lakes and well water toxicity monitoring, as well as warning the public about possible bioavailable contaminants that may pose a risk to human health. [resumo fornecido pelo autor]