Differentiating the Spatiotemporal Distribution of Natural and Anthropogenic Processes on River Water–Quality Variation Using a Self-Organizing Map With Factor Analysis

Abstract

To elucidate the historical improvement and advanced measure of river water quality in the Taipei metropolitan area, this study applied the self-organizing map (SOM) technique with factor analysis (FA) to differentiate the spatiotemporal distribution of natural and anthropogenic processes on river water-quality variation spanning two decades. The SOM clustered river water quality into five groups: very low pollution, low pollution, moderate pollution, high pollution, and very high pollution. FA was then used to extract four latent factors that dominated water quality from 1991 to 2011 including three anthropogenic process factors (organic, industrial, and copper pollution) and one natural process factor [suspended solids (SS) pollution]. The SOM revealed that the water quality improved substantially over time. However, the downstream river water quality was still classified as high pollution because of an increase in anthropogenic activity. FA showed the spatiotemporal pattern of each factor score decreasing over time, but the organic pollution factor downstream of the Tamsui River, as well as the SS factor scores in the upstream major tributary (the Dahan Stream), remained within the high pollution level. Therefore, we suggest that public sewage-treatment plants should be upgraded from their current secondary biological processing to advanced treatment processing. The conservation of water and soil must also be reinforced to decrease the SS loading of the Dahan Stream from natural erosion processes in the future.

Comprehensive assessment of fertiliser-linked environmental externalities and its key determinants: IWRM approach

“…Inductively coupled plasma mass spectrometry results revealed that the toxic element Pb was 1.64 times and As was 2.78 times more than the maximum permissible limits of drinking water. Wang et al (2015) used self-organising map technique to study the impact of the natural and anthropogenic process on river water quality and found suspended solids to be a natural factor for polluting upstream tributaries.…”

“…The quality of water deteriorates with heavy metals, nitrate and radioactive elements present in it (Camargo and Alonso, 2006;Nikolaidis et al, 2008). There have been numerous instances of high nitrate level in groundwater across the world due to the agricultural activities (Alabdula'aly et al, 2010;Bernhard et al, 1992;Levallois et al, 1998;Spalding et al, 2001;Wang et al, 2015;Zhang et al, 1996). Several cases of high concentration of nitrate exceeding the threshold limit of 50 mg l -1 for drinking water have been reported in countries like the UK, Denmark, Belgium, France, the USA and India (Agrawal et al, 1999;Banks and Soldal, 2002;Fried, 1991;Hudak, 2000;Strebel et al, 1989;Nolan et al, 1997;Singh et al, 2006;Wakida and Lerner, 2005).…”

Assessment on urban lakes along the coastal region of Miri, NW Borneo: implication for hydrochemistry, water quality, and pollution risk

“…Correlation analysis (CA) represents the degree of relationship between two random variables, where interpretation of the correlation would provide a plan of quick monitoring method on water quality (Ghazaryan and Chen 2016 ). Wang et al ( 2015 ) stated that the relationship between observed parameters is indicated by FA through revealing multivariate patterns such as major factors that are used to simplify initial datasets. FA is generally used to narrow down and simplify outcomes obtained from PCA, where both methods are used to reduce data (Bilgin and Bayraktar 2021 ; Howladar et al 2017 ).…”