Abstract
Determination of the bioavailability of the hydrophobic organic contaminant benzo[a]pyrene (B[a]P) is extremely important for assessing its environmental risk. The effect of addition manner of B[a]P on the bioavailability and toxicity of B[a]P in soil remains unclear. In this study, soil samples, spiked with B[a]P by one-time or multiple-time additions, were tested to investigate the available fraction of B[a]P in soils, the uptake of B[a]P by red wiggler worms (Eisenia fetida), as well as superoxide dismutase (SOD) and peroxidase (POD) activities in earthworm coelomocytes at different periods. Results showed that the available fraction of B[a]P in soils and the amount of B[a]P assimilated by earthworms declined sharply from 1 d to 28 d during the incubation period and then decreased slowly from 28 to 56 d in both the one-time and the multiple-time addition tests. The available fraction of B[a]P in soils and its uptake by earthworms were significantly lower in multiple-time addition samples than those in one-time addition samples, a finding which was consistent with the SOD and POD activities in earthworms during the whole 56-d incubation period. These variations in the characteristics of the two addition treatments may be due to the differences in the way the B[a]P aged in the soil. These results indicated that the addition method was an important factor influencing the bioavailability of organic contaminants in soils.
Highlights
Polycyclic aromatic hydrocarbons (PAHs) are degradation-resistant and hydrophobic organic pollutants, posing a serious threat to human health due to their carcinogenic, mutagenic, and teratogenic natures[1,2]
The available B[a]P content in the multiple-time treatment was 72% and 76% of that in the one-time addition treatment on day 1 and day 56, respectively. These results showed that the one-time addition treatment resulted in B[a]P being easier to be desorbed from soil than in the multiple-time addition treatment
The present study showed that the concentration of the Tenax-TA adsorbed fraction of B[a]P in soil was positively (P < 0.01) correlated with the amount of B[a]P assimilated in earthworms, indicating that the Tenax-TA extractable fraction of B[a]P in soil was a good indicator of the bioavailability of B[a]P in the two addition treatments
Summary
Polycyclic aromatic hydrocarbons (PAHs) are degradation-resistant and hydrophobic organic pollutants, posing a serious threat to human health due to their carcinogenic, mutagenic, and teratogenic natures[1,2]. The addition method by which the pollutant was added to the soil needs to be considered in the risk assessment of B[a]P-contaminated soils[10,11]. Little information is known about the effect of B[a]P spiked in different methods on its bioavailability in soils and on antioxidants in earthworms. The purpose was to obtain a more comprehensive understanding of the effects of B[a]P on earthworms when spiked using different addition methods, which might help to more accurately assess the risk of B[a]P in the soil environment
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