Avaliação da qualidade da água no furo do Muriá, Curuçá (Pará, Brasil).

Abstract

In order to reduce impacts in the estuaries, measures have been adopted to assess the trophic status and have developed indexes that facilitate the understanding of the abiotic and biotic data of the waters of these environments. The Trophic State Indexe (IET) and Trophic Indexe (TRIX) were used to evaluate the seasonal effect on the water quality of the Creek Muriá, located in the municipality of Curuçá, PA, and to identify alterations occurred and their probable origins. Water harvesting was carried out in 21 points distributed throughout the Creek the months of January, February, March, May, June, July, September, October and November, 2015, during low tide and flood. Abiotic variables (temperature, salinity, electrical conductivity, turbidity, pH) were determined in situ using probe and the others in the laboratory (dissolved oxygen, saturated oxygen saturation, nitrate, nitrite, N-ammoniacal, phosphate, total phosphorus, Chlorophyll a. The data obtained reflected the typical seasonality of the region, salinity ranged from 7.0 to 36.80, EC from 21730 to 55500, pH from 7.14 to 9.95, temperature from 27Â ° C to 29Â ° C, turbidity of 1 To 218, OD 2 to 4, OD% rate 46 to 105, phosphate 0 to 0.6, nitrite of 0.0007 to 0.1334, nitrate of 0 to 0.81, N-ammonium of 0, 02 to 2.80, chlorophyll a from 0.0033 to 197. However, changes occurred in the distribution of precipitation volumes in January (39.8 mm), February (193.4 mm), March (844.4 Mm) and April (577.8 mm), reflecting the influence of the El Nino phenomenon in the year 2015. The IET and TRIX indexes showed that the Creek Muriá is naturally susceptible to eutrophication in accordance with the hydrological characteristics and diffuse sources of pollution. The statistical evaluation of the environmental variables showed significant differences between the analyzed periods (p < 0.05), tending to a seasonal pattern, except for N-ammoniacal (p > 0.05), thus not having a seasonal influence. Taking into account the tides the concentrations of salinity, CE and chlorophyll a were significant during the flood tide. The turbidity was higher during tidal ebb tides (p < 0.05). The phosphate and N-ammonia parameters showed no significant difference between tides (p > 0.05). The effect of seasonality may restrict to the variation of the quality of the environment, so the joint approach of the evaluation and application of the indices was considered satisfactory, since each study brings new and complementary information making the monitoring of the environment relevant, thus serving as a tool in plans More efficient and rapid public policies to improve basic sanitation for the population.