Assessing the ecotoxicological impact of surface water contamination from concentrated animal feeding operations in WoodCounty Ohio

Abstract

Application of manure from agricultural livestock operations to the crop fields has become an important approach towards the improvement of soil fertility. However, if overapplied or inefficiently managed, animal waste from confined animal feeding operations can become a potential source of water resources contamination, particularly in terms of nutrient pollution. The purpose of this study was to apply a toxicity testing evaluation approach as a complementary tool to assess the impact on surface water quality of application of manure, from two dairy CAFOs in Wood County, OH, to cropland. To fully evaluate the impact of manure, this study examined whether nutrient enrichment and bacteriological parameters are factors related to water and sediment toxicity. Samples of water and sediments were collected in spring and summer from sites selected according to manure application fields and drainage patters. First set of samples have been collected from fields that have had manure applied six months before the beginning of the study, and the second set of samples were taken right after summer application of manure to the cropfields. At the time of sample collection, at each site, measurements for water temperature, pH, dissolved oxygen, electrical conductivity, and turbidity were recorded. In addition to that, lab analysis of total coliform and E. coli bacteria, and the concentration of nitrate, soluble reactive phosphorus (orthophosphate), and ammonia have been performed. The toxicity of water samples was assessed using 48-hours Brachionus calyciflorus growth assay. The ecotoxicity of sediments was assessed by performing 6-days Heterocypris incongruens growth assay. Mortality and growth inhibition of neonates of the ostracod crustacean were measured. The final results revealed some toxic effects of the water and sediment to the test organisms. II Sites that have been affected for a long period of time by runoff from fields treated with manure have exhibited elevated toxicity, which was worsen in summer months, possibly by the combined effect of the manure application and physicochemical factors. Chemical and bacteriological analyses did not reveal particularly high concentrations of any chemical or fecal indicator bacteria that are very toxic. As a result no direct causal relationship could be established between the detected toxic effects and the chemical composition of the surface waters. The outcome of this study brings out the need to complement chemical analyses with toxicity tests to determine the toxic hazard to aquatic environments that may be threatened by animal waste from confined animal feeding operations.

Aplicação de estrume de gado de operações agrícolas para os campos de cultivo tornou-se uma abordagem importante para a melhoria da fertilidade do solo. Contudo, se aplicado em demasia ou gerido ineficientemente, os resíduos das indústrias de produção de animais confinados pode tornar-se uma fonte potencial de contaminação dos recursos hídricos, particularmente em termos de poluição por nutrientes. O objetivo deste estudo foi aplicar uma abordagem de avaliação de testes de toxicidade como uma ferramenta complementar para avaliar o impacto da aplicação do estrume na qualidade das águas superficiais, a partir de duas leitarias em Wood County, Ohio, EUA. Para avaliar o impacto do estrume, este estudo analisou se o enriquecimento em nutrientes e parâmetros bacteriológicos são factores relacionados com a toxicidade da água e de sedimentos. Amostras de água e de sedimentos foram recolhidas na primavera e verão, nas localizações selecionados de acordo com os campos de aplicação de estrume e padrões de drenagem. O primeiro conjunto de amostras foram recolhidas em campos onde do estrume aplicado seis meses antes do início do estudo, e o segundo conjunto de amostras foram recolhidas, no verão, logo após a aplicação de estrume nos campos de cultivo. Aquando a recolha das amostras, em cada local, medições da temperatura da água, pH, oxigênio dissolvido, condutividade eléctrica, turbidez foram registrados. Para além disso, análises de laboratório de coliformes totais e bactérias E. coli, bem como a concentração de nitrato, ortofosfato e amónia foram realizadas. A toxicidade das amostras de água foi avaliada através do ensaio de crescimento de Brachionus calyciflorus durante 48 horas. A ecotoxicidade dos sedimentos foi avaliada através de ensaios de crescimento de Heterocypris incongruens durante seis dias.