A methodological approach for spatiotemporally analyzing water-polluting effluents in agricultural landscapes using partial triadic analysis (PTA)

Abstract

Multivariate techniques for two-dimensional data matrices are normally used in water quality studies. However, if the temporal dimension is included in the analysis, other statistical techniques are recommended. In this study, partial triadic analysis (PTA) was used to investigate the spatial and temporal variability in water-quality variables sampled in a northeastern Spain river basin. The results highlight the spatiality of the physical and chemical properties of water at different sites along a river over one year. PTA allowed us to clearly identify the presence of a stable spatial structure that was common to all sampling dates across the entire catchment. Variables such as electrical conductivity (EC) and Na⁺ and Clˉ ions were associated with agricultural sources, whereas total dissolved nitrogen (TDN), NH₄⁺-N concentrations and NO₂ˉ-N concentrations were linked to polluted urban sites; differences were observed between irrigated and non-irrigated periods. The concentration of NO₃ˉ-N was associated with both agricultural and urban land uses. Variables associated with urban and agricultural pollution sources were highly influenced by the seasonality of different activities conducted in the study area. In analyzing the impact of land use and fertilization management on water runoff and effluents, powerful statistical tools that can properly identify the causes of pollution in watersheds are important. PTA can efficiently summarize site-specific water chemistry patterns in an applied setting for land- and water-monitoring schemes at the landscape level. The method is recommended for land-use decision-making processes to reduce harmful environmental effects and promote sustainable watershed management.