Monitoramento da poluição da água das galerias pluviais e do mar por meio de avaliações físico-químicas e microbiológicas

Abstract

The present paper was designed to monitor the water quality in stormwater sewers and the onshore of three beaches off Natal, Rio Grande do Norte State, namely do Meio, Areia Preta and Ponta Negra. A total of 144 samples were analyzed, 72 from the stormwater sewers and 72 from the adjacent sea water, during the rainy and dry seasons in the year 2002, at different tide phases and under the influence of the water temperature, salinity, electric conductivity and pH. The biological water quality was evaluated through the MPN of fecal coliforms (FC) and frequency of Escherichia coli, the results being expressed as medians. During the survey, temperature, salinity and pH kept constant whereas electric conductivity, MPN of FC and E. coli frequency showed variation trends. The Areia Preta beach proved to be the most contaminated, with median values of 1.1 x 106 and 2.4 x 106 per 100 mL of FC, for stormwater sewers, and 3.3 x 105 and 6.8 x 105 per 100 mL of FC, for the onshore water, in the rainy and dry seasons, respectively, followed by do Meio and Ponta Negra beaches. During the rainy season, the MPN of FC showed statistically-significant correlation with salinity (r = 0.68; P < 0.05), pH (r = 0.73; P < 0.05), conductivity (r = 0.73; P < 0.05) and tide phase (r = 0.63; P < 0.05), on the onshore water of do Meio beach. During the dry season, statistically-significant correlation was found to take place between MPN of FC values in the stormwater sewers and the adjacent sea water, on Areia Preta beach (r = 0.58; P < 0.05), a finding which may be related to the distance between the stormwater sewer and the coastline