Shi-Lei Sun

Microbial PAH-Degradation in Soil: Degradation Pathways and Contributing Factors

Adverse effects on the environment and high persistence in the microbial degradation and environmental fate of polycyclic aromatic hydrocarbons (PAHs) are motivating interest. Many soil microorganisms can degrade PAHs and use various metabolic pathways to do so. However, both the physio-chemical characteristics of compounds as well as the physical, chemical, and biological properties of soils can drastically influence the degradation capacity of naturally occurring microorganisms for field bioremediation. Modern biological techniques have been widely used to promote the efficiency of microbial PAH-degradation and make the biodegradation metabolic pathways more clear. In this review microbial degradation of PAHs in soil is discussed, with emphasis placed on the main degradation pathways and the environmental factors affecting biodegradation.

A Comparative Analysis of Environmental Quality Assessment Methods for Heavy Metal-Contaminated Soils

Abstract Four assessment methods (two pollution indexes and two fuzzy mathematical models) were employed to investigate the environmental quality of four soils around a ferroalloy plant in Nanjing City. Environmental quality was assessed as class IV (moderately polluted) for each soil with single-factor index method, and was identifled to be classes IV, III (slightly polluted), III, and III for soils A, B, C, and D, respectively, with the comprehensive index model. In comparison with the single-factor index method, the comprehensive index model concerned both dominant parameter and average contribution of all factors to the integrated environmental quality. Using the two fuzzy mathematical methods (single-factor deciding and weighted average models), the environmental risks were determined to be classes IV, III, II (clean), and II for soils A, B, C, and D, respectively. However, divergence of the membership degree to each pollution class still occurred between the two methods. In fuzzy mathematical methods, membership functions were used to describe the limits between difierent pollution degrees, and difierent weights were allocated for the factors according to pollution contribution. Introduction of membership degree and weight of each factor to fuzzy mathematical models made the methods more reasonable in the fleld of environmental risk assessment.

Toxicity of purified terephthalic acid manufacturing wastewater on reproductive system of male mice (Mus musculus)

Reproductive toxicity of purified terephthalic acid (PTA) manufacturing wastewater on the male mice (Mus musculus) was investigated after 35-day intragastric perfusion treatment with the wastewater. Fluorescein diacetate and propidium iodide staining, and flow cytometry were used to assess the toxicity of PTA wastewater on spermatogenic cells. PTA wastewater induced significant variations in the relative percentages of immature haploid, diploid, tetraploid and S-phase spermatogonia. Percentage of viable spermatogenic cells was reduced from 93.1+/-2.3 in control group to 90.4+/-1.9 in the wastewater-treated group. Testicular histopathology revealed expansion of interstitial space and reduction in the number and size of Leydig cells induced by the wastewater, which was further certified by the decrease (10.6%) in relative testes weight and the increase (101.3%) in sperm shape abnormality in the wastewater-treated group. In this study, PTA wastewater was found to have reproductive toxicity on male mice, and public health problems may potentially arise from the discharge of the wastewater into the environment.

Toxicity of Pharmaceutical Wastewater on Male Reproductive System of Mus musculus

This study reports on the toxic effects of 35-days intragastric perfusion of pharmaceutical wastewater on the male reproductive system of Mus musculus. Flow cytometric analyses and staining with fluorescein diacetate (FDA) and propidium iodide (PI) were used to assess the toxicity on spermatogenic cells. Significant depletions in the relative percentages of elongated spermatid (HC), diploid spermatogonia (2C), and S-phase cells were observed. These alterations in different germ cell populations were reflected in the various germ cell ratios. The ratios of 1C : 4C and HC : 2C showed a significant decline after pharmaceutical wastewater treatment, while the 4C : 2C and 1C : 2C ratios increased significantly. FDA and PI staining displayed reduced viability of spermatogenic cells in wastewater treated group. Statistically significant percentages of sperm abnormalities showed the genotoxic potential of this pharmaceutical wastewater. Testicular histopathological studies of treated animals revealed expansion of interstitial space and reduction in the number and size of Leydig cells. Thus, the present study has established the toxicity of pharmaceutical wastewater on the reproductive biology of male mice. Toxicology and Industrial Health 2007; 23: 47—54.