Impacto de los efluentes mineros en los macroinvertebrados acuáticos en la cabecera del río Tingo, Cajamarca, Perú

Abstract

Water quality in high Andean rivers is threatened by increased mining activities that affect related ecosystem services. The study's main objective was to evaluate the physicochemical parameters, heavy metals and aquatic macroinvertebrates as indicators of the ecological status of the Tingo River during the dry, transition and rainy seasons. Three monitoring points were established, taking into account the mining intervention in the area. The physicochemical parameters analyzed were flow, pH, temperature, dissolved oxygen, total dissolved solids and electrical conductivity. The heavy metals analyzed were aluminum, cadmium, copper, iron, magnesium and lead. In addition, with the macroinvertebrate data, the Biotic Index for the rivers of northern Peru (nPeBMWP) was calculated to determine the ecological quality of the headwaters of the Tingo River. In the sources of the Tingo River, changes in spatial dynamics were more noticeable than changes in temporal dynamics. The most critical parameters of the study were flow, pH, electrical conductivity, copper, iron and manganese. On the other hand, both flow and pH were the parameters that correlated the most with the rest of the parameters, finding four correlations for each one. The pH, dissolved oxygen, and lead parameters did not meet the Environmental Quality Standards for Category 4. As for macroinvertebrates, they were only found in the station without mining influence. Three hundred sixty-six individuals were recorded, belonging to 12 families distributed in three classes and seven orders. The most abundant class was Insecta with 99.5% of the total number of individuals, highlighting the order Diptera with 79.5%. According to the nPeBMWP, the ecological quality is generally poor, highlighting the change in rate according to the time of sampling in the season without influence (from fair to poor). All these results were statistically significant (p<0.05). The evaluation of all parameters and macroinvertebrates shows that mining effluents have a significant impact on the headwaters of the Tingo River, eliminating 100% of the macroinvertebrates by altering the physicochemical properties of the water.