Abstract
Spatiotemporal variations of ten physicochemical parameters in the water quality of Atoyac River basin, Central Mexico, were obtained from 22 sampling sites (66 samples in total) located all along the basin for three different seasons (dry, rainy and winter). Multivariate statistical techniques such as correlation matrix, factor analysis (FA) and cluster analysis (CA) were used as a tool to understand the process. Physicochemical parameters such as temperature (T), pH, conductivity (λ), dissolved oxygen (DO), spectral absorption coefficient (SAC), oxidation–reduction potential (ORP), turbidity, 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS) were analyzed. Extremely high values of pH (10.24), conductivity (1870 µS/cm) and reduced redox potential (−370.1 mV) were observed in the dry season, whereas elevated TSS of 2996 mg/L was detected during the rainy season. The results elucidated high influence from the adjoining industrial, agricultural and urban zones, making the river unsuitable for life. FA generated varifactors, which accounted for cumulative % of 75.04 (dry), 76.22 (rainy) and 79.96 (winter) clearly grouping the external factors responsible for these significant values indicating the source of contamination. Cluster analysis facilitated the ease of classifying the sampling sites based on the similarities of physicochemical parameters. This study carried out in different seasons using multivariate statistical techniques would definitely prove to be an efficient tool for the restoration and establishing the real-time monitoring stations along this important river basin of Mexico.
Highlights
A river is a well-defined geomorphological structure encompassing the main stream and several tributaries with a unidirectional flow of substantial loads of dissolved and suspended matter from both natural and human-induced activities (Shrestha and Kazama 2007)
The results suggest that the studies on surface water quality drive the need for a regular monitoring program for the improvement in river ecosystem and the identification of the possible sources of pollutants
The physicochemical characteristics of the river basin revealed the influence of the small-scale changes associated with the active Popocatepetl Volcano, supplemented by intense human activities
Summary
A river is a well-defined geomorphological structure encompassing the main stream and several tributaries with a unidirectional flow of substantial loads of dissolved and suspended matter from both natural and human-induced activities (Shrestha and Kazama 2007). The present global scenario of intense demographic growth and urban practices has resulted in degrading water resources, calling for instant remedial actions by construing a precise study of its physical characteristics and water quality. Influential factors that determine the river water quality include precipitation inputs, erosion and weathering of crustal materials as well as human-induced activities like urban development and expansion, industrial and agricultural practices (Carpenter et al 1998; Muangthong and Shrestha 2015), whereas many processes like synergies of pollution loads, hydrological characteristics, sediment and metabolic activities in the water are 95 Page 2 of 15. The river water quality is interpreted using various approaches such as computational models and mathematical formulas, and the most efficient one is through the integration of water quality parameters into one single index (Boyacioglu 2007; Sowlat 2011; Bakan et al 2010; Wanda et al 2016)
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