Abstract
The rainwater chemistry within the Metropolitan Area of Monterrey (MAM) was studied during a one-year period (January 2019–January 2020) in seven sampling sites. The metal concentration of Zn, Fe, Cd, Cu, Ni, and Mn was analyzed in bulk samples and the toxicity potential (TP) was calculated for each metal. A canonical correspondence analysis (CCA) was applied to identify the relationship between environmental variables and metals concentrations. An average of 26.6 ± 10 mm of rainfall was obtained. A mean pH of 7.2 ± 0.3 and a mean electrical conductivity of 177.8 ± 8.7 µS cm−1 were observed. The average concentration of metals in all sites follows a descending order of Fe> Zn > Mn > Cu > Ni > Cd. The university site shows the highest averages of Fe, Zn, Cu, and Mn, which is attributed to its proximity to the metallurgical industry. The TP value of Cd reflects a risk in all sites and Fe only for the Universidad, Obispado, Pastora, and Santa Catarina sites, using as a reference value the Environmental Protection Agency (EPA) Drinking Water Regulations and Mexican norm NOM-127-SSA1-1994. The CCA analysis showed that only Ni and Cd had a strong correlation with the environmental variable of relative humidity of air.
Highlights
The chemical composition of rainwater is highly dependent on the concentration of atmospheric pollutants and particulate matter; it can be used as an indicator of air quality in a given area [1]
The local emissions are not significant for the levels of air contamination reported, or in some cases the chemical compounds found in the air do not correspond to local emission sources; this is because the air mass transports pollutants from other regions [10]
Given the elements analyzed and the previously described particle characteristics of the Metropolitan Area of Monterrey (MAM), it can be understood that the influence of long-distance sources of emission have little relevance when compared to local emission sources, at least for the metals investigated in this study
Summary
The chemical composition of rainwater is highly dependent on the concentration of atmospheric pollutants and particulate matter; it can be used as an indicator of air quality in a given area [1]. The analysis of rainwater provides important information for the atmospheric chemical composition, mechanisms that influence the distribution and transport of atmospheric chemical species and their possible source of origin [2]. The type and concentrations of chemical species in rainwater vary between locations and regions It reflects the influence of local sources, atmospheric transport conditions, atmospheric temporal development, and its level of contamination [8]. In order to improve the policies that regulate the emission of air pollutants and to understand the behavior of the movement of regional or global emissions, some studies in recent decades have focused on the analysis of long-range transport of pollutants, potential sources, and meteorological conditions, combing these parameters to provide a precise modeling of air mass and contaminant trajectories [1,5,11]
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