The river basin sediments are deposited during the late Pleistocene and Holocene and are loess-like type of soils dominated by Argiudolls, Natraqualfs, and Natraquolls.
A number of studies have been conducted to investigate the environmental status in both the river sediments and the water column. Research of the sediment composition states that it's mostly composed of clay and clay loam. The geochemical analysis has shown high metal concentrations of Cu, Zn, Pb, Cd and Cr much above recommendation values and a significant number of cancerogenic and mutagenic toxins present in the river. The contamination are highest in the lower urbanized and industrialized part of the river basin. The upper and middle peri-urban and agricultural areas are also contaminated but not in the same extent. But high concentrations was found close to Chacon river which, is located in the middle part of basin in several studies, this is believed to be due to leaching from a dump site. The metal concentrations in the sediment cores are decreasing in temporal dimension indicating an increase in contaminants during the last decades.
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As previous studies have shown the surface sediment in the river consists of clay and clayey loam and the sentimental distribution does not change much throughout the upper, middle and lower parts of the basin. This means that the metal concentrations are not changing due to sediment distribution, since it is similar sedimentary conditions throughout the entire river. In addition, the concentration variability are largely due to the location of contaminant sources. That is, the highest concentrations are found in the vicinity of the most urbanized and industrial active areas. These places show as well a higher content of organic matter which is believed to come from dumpsites and industries.
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It's clear that the river system has been heavily contaminated during the last century since the industrialization of the region. No larger remediation actions has been carried out so far, and the area has no effective regulations of pollution from industries and urban run-off. Other issues in the area is the lack of sewage treatment, only 75 % of the population within the catchment area is connected to the public sewerage. One action proposed to improve the situation is dredging, however, this is not considered as an appropriated sustainable solution due to the highly contaminated surface sediments. Dredging would only re-mobilize the pollutants elsewhere.