Spatiotemporal distribution of physicochemical parameters and toxic elements in Lake Pomacochas , Amazonas, Peru

Abstract

Lakes are water bodies that play an essential role as water sources for humanity, as they provide a wide range of ecosystem services. Therefore, this study aimed to evaluate Lake Pomacochas, a high Andean lake in the north of Peru. A variety of parameters were studied, including physicochemical parameters such as temperature (T°C), dissolved oxygen (DO), potential hydrogen (pH), electrical conductivity (EC), turbidity, total dissolved solids (TDS), biochemical oxygen demand (BOD), alkalinity, and chlorides hardness; the concentrations of nitrates, nitrites, sulfates, and ammonium; elements such as aluminum (Al), calcium (Ca), magnesium (Mg), sodium (Na), potassium (K), and boron (B); as well as metals and metalloids such as zinc (Zn), cadmium (Cd), copper (Cu), lead (Pb), and arsenic (As). In addition, pH, Zn, and Cu were evaluated at the sediment level. It is important to note that all parameters evaluated in the water matrix showed significant differences in the seasonal period and depth levels. In comparison, the parameters evaluated at the sediment level had no significant differences between the seasonal period and sampling points. As for the seasonal period, the variables that were higher for the dry season were electrical conductivity, total dissolved solids, and lead while that for the wet season were biochemical oxygen demand, zinc, magnesium, turbidity, calcium, dissolved oxygen, temperature, and potential hydrogen. At the depth levels, parameters such as total dissolved solids, lead, and arsenic had similar behavior for the three depths evaluated. According to national standards, latent contamination by cadmium and lead was found in the lake water from the ecological risk assessment. However, by international standards, all sampling stations showed a high level of contamination by cadmium, lead, zinc, copper, and arsenic, which represents a potential risk for the development of socioeconomic activities in the lake. At the same time, the evaluation of sediments did not present any potential risk.