How much do the conventional parameters contribute to the biological toxicity of surface water in different types of villages?

Abstract

Background: In rural areas, the surface water quality is seriously threatened by pollution from agriculture, breeding, industrial and tourism activities. Even though many strategies and programs were launched for rural environment management, it is challenging to tackle the serious surface water pollution in villages. Since pollution status varies with the type of villages, there is no single parameter that defines environment quality completely. Until recently, most of rural surface water quality monitoring programs focus only on the conventional parameters, while can these conventional parameters reflect comprehensive status of water quality? To study how much the conventional parameters contribute to biological toxicity of surface water in villages, the in situ parameters of pH, DO, EC, ORP, laboratorial parameters of COD, TN, NO3−-N, NO2−-N, NH4+-N, TP, and PO43−-P and acute toxicity were analyzed for the surface water samples those were collected from six types of villages, named breeding, agricultural, handicraft, industrial, agricultural and breeding, and tourism. The correlation analysis was applied to establish the linkages and contributions of each parameter. Results: The results showed that all detected surface waters were alkaline, and the concentration of TN and most of COD concentrations in all six types of villages were higher than the Class V limits specified in environmental quality standards for surface water (GB3838-2002). Pearson’s correlation analysis showed that significantly positive correlations were found for the acute toxicity effects and laboratorial parameters of NO2−-N, NH4+-N and PO43−-P in agricultural villages, and negative correlations were found for the acute toxicity effects and laboratorial parameters of TN and NO3−-N. No significant correlation was observed in breeding villages and industrial villages. Conclusion: The problems of nitrogen pollution and aerobic pollution are still serious in villages, and more attention should be paid in further rural environment management. NH4+-N could contribute to the acute toxicity of surface water in the most of investigated villages, while no significant correlation was observed between acute toxicity and conventional parameters in industrial villages and tourism villages. Environmental monitoring programs focusing just on the classical conventional parameters are far from sufficient, since the main toxic contributors are quite different in diverse villages. The outcomes of the present study contribute to demonstrate the performance and usefulness of bioanalytical techniques for water quality assessment.