Appropriate control measure design by rapidly identifying risk areas of volatile organic compounds during the remediation excavation at an organic contaminated site.

Many organic contaminated sites require on-site remediation; excavation remediation processes can release many volatile organic compounds (VOCs) which are key atmospheric pollutants. It is therefore important to rapidly identify VOCs during excavation and map their risk areas for human health protection. In this study, we developed a rapid analysis and assessment method, aiming to and reveal the real-time distribution of VOCs, evaluate their human health risks by quantitative models, and design appropriate control measures. Through on-site diagonal distribution sampling and analysis, VOCs concentration showed a decreasing trend within 5 m from the excavation point and then increased after 5 m with the increase in distance from the excavation point (p < 0.05). The concentrations of VOCs near the dominant wind direction were higher than the concentrations of surrounding pollutants. In contrast with conventional solid-phase adsorption (SPA) and thermal desorption gas chromatography-mass spectrometry (TD-GC/MS) methods for determining the composition and concentration of VOCs, the rapid measurement of VOCs by photo-ionization detector (PID) fitted well with the chemical analysis and modeling assessment of cancer/non-cancer risk. The targeting area was assessed as mild-risk (PID < 10 ppm), moderate-risk (PID from 10 to 40 ppm), and heavy-risk (PID > 40 ppm) areas. Similarly, the human health risks also decreased gradually with the distance from the excavation point, with the main risk area located in the dominant wind direction. The results of rapid PID assessment were comparable to conventional risk evaluation, demonstrating its feasibility in rapidly identifying VOCs releases and assessing the human health risks. This study also suggested appropriate control measures that are important guidance for personal protection during the remediation excavation process.

Effects of bioaugmentation by isolated Achromobacter xylosoxidans BP1 on PAHs degradation and microbial community in contaminated soil.

Polycyclic aromatic hydrocarbons (PAHs) are a group of organic pollutants ubiquitous and persistent in soil. In order to provide a viable solution for bioremediation of PAHs-contaminated soil, a strain of Achromobacter xylosoxidans BP1 with superior PAHs degradation ability was isolated from contaminated soil at a coal chemical site in northern China. The degradation of phenanthrene (PHE) and benzo[a]pyrene (BaP) by strain BP1 was investigated in three different liquid phase cultures, and the removal rates of PHE and BaP by strain BP1 were 98.47% and 29.86% after 7 days under the conditions of PHE and BaP as the only carbon source, respectively. In the medium with the coexistence of PHE and BaP, the removal rates of BP1 were 89.44% and 9.42% after 7 days, respectively. Then, strain BP1 was investigated for its feasibility in remediating PAH-contaminated soil. Among the four PAHs-contaminated soils treated differently, the treatment inoculated with BP1 exhibited higher removal rates of PHE and BaP (p < 0.05), especially the CS-BP1 treatment (inoculation of BP1 into unsterilized PAHs-contaminated soil) showed 67.72%, 13.48% removal of PHE and BaP, respectively, over 49 days of incubation. Bioaugmentation also significantly increased the activity of dehydrogenase and catalase in the soil (p＜0.05). Furthermore, the effect of bioaugmentation on the removal of PAHs was investigated by measuring the activity of dehydrogenase (DH) and catalase (CAT) during incubation. Among them, the DH and CAT activities of CS-BP1 and SCS-BP1 (inoculation of BP1 into sterilized PAHs-contaminated soil) treatments inoculated with strain BP1 were significantly higher than those of treatments without BP1 addition during incubation (p < 0.01). The structure of the microbial community varied among treatments, but the Proteobacteria phylum showed the highest relative abundance in all treatments of the bioremediation process, and most of the bacteria with higher relative abundance at the genus level also belonged to the Proteobacteria phylum. Prediction of microbial functions in soil by FAPROTAX analysis showed that bioaugmentation enhanced microbial functions associated with the degradation of PAHs. These results demonstrate the effectiveness of Achromobacter xylosoxidans BP1 as a PAH-contaminated soil degrader for the risk control of PAHs contamination.