Compost-mediated removal of polycyclic aromatic hydrocarbons from contaminated soil.

Compost-assisted remediation of a manufactured-gas plant soil contaminated with polycyclic aromatic hydrocarbons (PAHs) was performed in thermally insulated composting chamber using mushroom compost consisting wheat straw, chicken manure, and gypsum. The degradation of individual PAHs was in range of 20-60% at the end of 54 days of composting followed by further increase of PAH removal (37-80%) after another 100 days of maturation. Both chemical analysis of the contaminated soil for PAHs and ecotoxicity tests on bioluminescent bacteria, earthworms, and plant seeds were performed before and after the composting. After the composting, inhibition of bioluminescence decreased, whereas no significant change in toxicity was observed for earthworm survival and seed germination. Using bacterial culture of Escherichia coli K12 genotoxicity tests were performed on samples taken from different parts of the composting pile; after the composting the decrease in genotoxicity was observed only in the sample taken from upper part of the composted pile.

Mutagenicity tests on the bacteria and the detection of genotoxicity of industrial complex mixtures containing PAHs.

The study summarizes the results of an evaluation of mutagenicity of heterogeneous complex mixtures of substances, the main mutagenic component of which consists of polycyclic aromatic hydrocarbons. The testing was performed using bacterial assays of mutagenicity--the SOS chromotest and the S. typhimurium His-test (in modifications without and with metabolic activation in vitro). It was found that samples of tested tar mixtures (crude tar, pitch, anthracene oils III and II, granulated pitch and some of its extraction portions) induced SOS repair functions and frameshift mutations in tests with metabolic activation. Some of samples as tar, pitch and anthracene oils III, granulated pitch and two its extraction portions--LRAC and LRBe--induced also frameshift mutations, and SOS repairs in tests without the metabolic activation. In one sample--LRBe--the ability to induce mutations in all variants of both tests, was also proved. The evaluation of mutagenicity of fly ashes showed that differences in the mutagenic activity of samples can be directly dependent on the extraction method chosen and on the type of extraction agent used. The study results demonstrate that the bacterial tests Salmonella typhimurium His- and the SOS chromotest are uninterchangeable and quite independent. Both tests can be used for orientative screening for genotoxicity in a wide range of various complex mixtures arising from industrial production and contaminating the environment.