Development Of Soil Quality Indices Based On Biological Indicators To Assess Chemical Soil Degradation By Metal(Loid)S In Soils Near To A Copper Smelter

Abstract

In recent years, soil quality assessment takes into account some ecologic topics such as soil multifunctionality, resistant, resilience and ecosystem services, which can be a useful approach to evaluate disturbed soils such as metal(loid) contaminated soils such as the Puchuncaví Valley in Chile. Despite this, soil quality based on biological indicators for metal(loid) contaminated soils has been scarcely. This Doctoral Thesis aims to develop soil quality indices (SQIs) to assess the chemical degradation by metal(loid)s in soils. For this, a review and meta-analysis were firstly performed with data from literature, which showed enzyme activity decreasing on metal(loid) contaminated soils. Endoenzymes such as dehydrogenase (DHA) and arylsulfatase (ARY) were the most negatively affected compared to other exoenzymes such as urease, phosphatases, and catalase. Additionally, the negative metal(loid) effect on enzyme activities decreased at higher clay contents and soil depth, showing also effects of several experimental factors. Based on these results, a laboratory experiment showed that DHA and ARY were clearly negatively affected by copper (Cu) contamination. Also, the community level physiological profile (CLPP) showed a catabolic shift by Cu contamination, with less functional microbial communities in higher contaminated soils. Similarly, a field study in the Puchuncaví Valley showed an increasing biological activity (enzyme activities and CLPP) at farther distances of the contamination source; however, soil properties, such as organic matter and clay contents, apparently strongly buffered the negative effect of metal(loid)s on microbial communities. In this study, CLPP and DHA, ARY, and arginine ammonification were the most sensitive to metal(loid) contamination and total organic carbon changes, which suggest a strong effect of soil degradation on the active and general microbial activity instead of specific enzyme processes. Finally, some SQIs were developed based on some biological and physic-chemical indicators, selecting the Multifunctionality and the Area SQI as the most reliable soil quality indices. Nevertheless, these indices explained a portion of the variability in a particular field (Puchuncaví Valley), by which their applicability should be based on the method beyond the selected indicators. This Doctoral Thesis is the first approach to assess the soil biological functioning in metal(loid) contaminated through SQIs soils in Chile.