A influência de obras de adequação da capacidade rodoviária na qualidade da água dos corpos hídricos

Abstract

This study verified the influence of the duplication works of the BR-101 highway on the water quality of twenty water courses intercepted in the state of Alagoas in Brazil, through statistical evaluation on the physical-chemical analyzes and microbiological examinations of the water carried out between the years of 2011 and 2018, considering Conama Resolution 357/2005. The temporal variation of 26 parameters related to water quality, through analysis of variance, indicated significant and favorable changes for dissolved oxygen, electrical conductivity, BOD, total dissolved solids, pH, fixed solids, total solids, thermotolerant coliforms, total coliforms , chlorophyll-a, nitrite, phosphorus, iron and mercury. In the other water bodies, no significant changes were observed, even so, there were changes in the classification of some, both favorable and unfavorable. The values of the parameters obtained were used to evaluate the Water Quality Index (WQI), which varied between 51 and 79 in practically all rivers. On average, this index increased by 23.52% in 8 of the 11 water bodies that had their works completed, when compared to the period prior to the works. This fact is due to the improvement in some parameters, mainly in the increase of DO, and in the reduction of BOD and Thermotolerant Coliforms, provided by the works due to the limited access of the local population to the bed of water bodies. The main environmental problems identified throughout the project are related to external factors such as contamination of faecal origin basically due to the discharge of domestic and industrial effluents, in addition to agricultural activities and animal feed.