Modification of the Relative Abundance of Constituents Dissolved in Drinking Water Caused by Organic Pollution: a Case of the Toluca Valley, Mexico

Abstract

Drinking water contains geogenic elements to which human beings are exposed; in the long term, these elements can be either harmful (As) or beneficial (Mg and Ca) to health. The composition and relative abundance of the constituents in groundwaters are conditioned by the balance between dissolution, precipitation, and oxide-reduction processes also by the nature and spatial arrangement of the materials interacting with the water. In recent decades, human activities and changes in the use of land have led to the accumulation of organic materials and their degradation into nitrogen and phosphorus, which has resulted in a change of the physicochemical composition and quality of drinking water. The main target of the study was to evaluate the effect of contamination by nitrogen and phosphate organic matter on the physicochemical composition of water used for human consumption. The study was conducted in the Toluca Valley aquifer. The determination of parameters in situ and analysis in the laboratory of physicochemical parameters revealed the presence of NO3− (1.0–119 mg L−1), SO42− (6.81–24.70 mg L−1), PO43− (2.50–32.20 mg L−1), and N-NH4+ (0–5.40 mg L−1), which suggested the presence of punctual anthropogenic contamination; this was confirmed using 3D fluorescence to identify the presence of organic matter. The results of Na+ (15.75 mg L−1), K+ (2.66 mg L−1), Ca2+ (8.73 mg L−1), and Mg2+ (8.01 mg L−1) using the ICP technique showed that the water supplied in the area has a low mineral content. Correlation between P and cations Ca2+ (0.844) > Na+ (0.720) > Mg2+ (0.694) > K+ (0.60) indicates that anthropic contamination affects the relative abundance of dissolved constituents in water. The scarcity of essential nutrients in water impacts on public health; it has been reported that deficiency of Ca2+ and Mg2 implies a wide variety of clinical conditions, mainly in the development of cardiovascular diseases.