Abstract
AbstractContamination of land by persistent organic pollutants has significant implications for human health and for future development potential. Bioremediation is an effective method for reducing the concentrations of such contaminants to below harmful levels, but the presence of co‐contaminants may hinder this process. Here, we present the results of a 40‐week microcosm study in which the biodegradation of 16 United States Environmental Protection Agency (USEPA) polycyclic aromatic hydrocarbons (PAHs; total: 2,166 mg kg−1) was followed in the presence of 3 different concentrations of cadmium (up to 620 mg kg−1) and lead (up to 782 mg kg−1) in a high organic matter soil. In the absence of metal treatment, 82% of PAHs were removed during the study period. Lead exerts a greater negative effect on total PAH removal than cadmium at low concentrations (approximately 100 mg kg−1) whilst cadmium exerts the greatest effect at higher concentrations (up to −27.7% reduction). Mercury, intended as the abiotic control (approximately 1,150 mg kg−1), exerts the greatest effect overall (−37%). Principal Component Analysis showed that PAH degradation was strongly associated with soil respiration rate, biomass content, and Ecoplate Average Well Colour Development. During the initial phase of the experiment, reduced microbial diversity was associated with increased PAH removal, consistent with literature observations for other organic contaminants, though this association was reversed after Week 12. Degradation of higher molecular weight PAHs showed the greatest sensitivity to the health of the microbial community. The effect of metal treatments on biotic parameters in microcosms without PAH amendment is also presented.
Highlights
Land degradation due to pollution from organic and inorganic contaminants is a significant issue, affecting both human health and the potential for future development and use (Chen et al, 2017, Roy &Mcdonald, 2015)
The results described in this paper represent a substantial study of the biodegradation of 16 US EPA polycyclic aromatic hydrocarbons (PAHs) over a 40‐week period, adding to the limited body of work involving PAH removal in long‐term studies, and in particular, in soils of high OM
The additional consideration of the effects of metal treatments on biodegradation and the relationship between PAH removal and various measures of microbial community function gives a useful insight into the processes occurring in sites that are cocontaminated with metals and PAHs
Summary
Land degradation due to pollution from organic and inorganic contaminants is a significant issue, affecting both human health and the potential for future development and use Many former industrial sites, those with a history of coal gasification or waste incineration (Cerniglia, 1997) These toxic and in many cases, carcinogenic and mutagenic substances (Baird, Hooven, & Mahadevan, 2005) can be present in contaminated sites at concentrations of thousands of mg kg−1 and may pose a significant environmental health risk. Cd concentrations reported in these same studies were somewhat lower (up to 112 mg kg−1) than used in the present study; in choosing our concentration range, we felt it was important to compare relative effects for similar concentrations of Pb and Cd. Principal Component Analysis (PCA) was used to relate the extent of PAH degradation (16 individual USEPA PAHs), in the metal‐ amended soils, to trends in simultaneously measured biotic parameters that are indicative of the health and diversity of soil microbial communities. The effect of Cd, Pb, and mercury (Hg) on control microcosms, containing no PAHs, was studied
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