Using chemometric tools to assess anthropogenic effects in river water: A case study: Guadalquivir River (Spain)

Abstract

The Guadalquivir River is the major water source of the south of Spain. In this work, we have selected an area, about 115 km long, from Alcalá del Rı́o to the mouth of the river, to study the effects caused by human activities on water quality. The area under study includes several sensible points as the town of Seville, the Guadiamar River (where an important mine spill took place on April 1998) and the Doñana National Park. We measured several physico-chemical variables in the 26 sampling stations located along the river, and in three different campaigns from 2001 to 2002. With the results we built the data matrix, which was analysed by factor analysis/principal components analysis (FA/PCA) and cluster analysis (CA). This analysis allowed the identification of four different zones in the river, with different water quality. The first zone (zone 1A) comprised from Alcalá del Rı́o to Seville. The second zone (zone 1B) was the city of Seville, and as a consequence, presented higher concentrations of several variables such as nitrite, ammonium or manganese. The third zone (zone 2) included from Seville to the Guadiamar River. In this area, agriculture is the main activity, and then, higher concentrations of suspended solids and phosphate were measured. In terms of water quality, this zone was partially similar to zone 1A, and partially similar to the fourth zone, starting in the Guadiamar River and finishing in the mouth of the Guadalquivir River. The water in this last zone (zone 3) is mainly estuarine water. Thus, its quality is influenced by seawater input, and also by the inputs from the Guadiamar River (coming from a mining area), and presented higher copper concentration. Three principal components were extracted, explaining the 79.1% of the data variance. PC1 (46.9% variance) was mainly associated with nitrite, ammonium and manganese. PC2 (22.5% variance) was mainly associated with suspended solids and phosphates. PC3 (9.7% variance) was mainly correlated to nitrate and copper concentration.