Water quality index of surface water bodies for fishing in the south of the state of veracruz, mexico, applying two methodologies

Abstract

The evaluation of water quality for protection of aquatic life from surface waters was carried out in 16 sampling points in a region between Jáltipan and Texistepec, Vera-cruz, Mexico, during a dry season, applying two methodologies. The characterization parameters were pH, temperature, dissolved oxygen (DO), conductivity, turbidity, total dissolved solids (TDS), total suspended solids (TSS), chlorides, hardness, alkalinity, biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total phospho-rus, total Kjeldahl nitrogen (TKN), organic nitrogen, ammonium nitrogen (N-NH4+), nitrite nitrogen (N-NO2–) and nitrate nitrogen (N-NO3–). The first methodology is a modification of the proposed by the US National Sanitation Foundation (NSF), which is based on eight parameters: DO, pH, temperature, BOD5, TDS, turbidity, N-NO3 and total phosphorus; while the second is based on the one proposed by CNA, which originally considers 18 parameters (only 13 were contemplated). From the application of both methodologies, water quality indexes were obtained for each point studied, observing that the quality fluctuated from contaminated to excellent. Contrasting with the Ecological Criteria of Water Quality for the protection of aquatic life, the parameters that most affect the quality of water for noncompliance with the recommendations are DO, total phosphorus and N-NH4+. A parameter that is not included in the methodologies used is the COD. According to the Water Quality Criteria from Conagua (less demanding than international regulations), the values reached for COD in the study area classify the water from contaminated to heavily contaminated.