A biological loss of endosulfan and related chlorinated organic compounds from aqueous systems in the presence and absence of oxygen.

Endosulfan is a cyclodiene organochlorine currently widely used as an insecticide throughout the world. This study reports that the endosulfan isomers can be readily dissipated from aqueous systems at neutral pH in the absence of biological material or chemical catalysts, in the presence or absence of oxygen. The study showed that aldrin, dieldrin, and endosulfan exhibit bi-phasic loss from water in unsealed and butyl rubber sealed vessels. Half-lives are substantially increased for endosulfan I when oxygen is removed from the incubation vessel. The study conditions, where PTFE was used, were such that loss due to volatilization and alkaline chemical hydrolysis was eliminated. Half-lives determined from these data indicate that the parent isomers are much less persistent than the related cyclodienes, aldrin and dieldrin, confirming the findings of previous studies. The major oxidation product of endosulfans I and II, endosulfan sulfate, is less volatile and can persist longer than either of the parent isomers. Endosulfan sulfate was not formed in any of the treatments suggesting that it would not be formed in aerated waters in the absence of microbial activity or strong chemical oxidants. Since endosulfan sulfate is formed in many environments through biological oxidation, and is only slowly degraded (both chemically in sterile media and biologically), it represents a predominant residue of technical grade endosulfan, which finds its way into aerobic and anaerobic aquatic environments. The data obtained contributes to and confirms the existing body of half-life data on endosulfan I and II and its major oxidation product, endosulfan sulfate. The half-life data generated from the current study can be used in models for predicting the loss of chlorinated cyclodiene compounds from aqueous systems. The findings also highlight the importance of critically reviewing half-life data, to determine what the predominant processes are that are acting on the compounds under study.

Co-composting of pharmaceutical wastes in soil.

AIMS: Soils at a commercial facility had become contaminated with the pharmaceutical chemical residues, Probenecid and Methaqualone, and required remediation. METHODS AND RESULTS: Soil composting was investigated as an alternative to incineration for treatment. In laboratory trials, a factorial experimental design was used to evaluate organic matter amendment type and concentration, and incubation temperature. In pilot scale trials, Probenecid was reduced from 5100 mg kg(-1) to < 10 mg kg(-1) within 20 weeks in mesophilic treatments. An 8 tonne pilot scale treatment confirmed that thermophilic composting was effective under field conditions. In the full-scale treatment, 180 tonnes of soil were composted. Initial concentrations of the major contaminants in the full-scale compost treatment were 1160 mg kg(-1) and 210 mg kg(-1), for Probenecid and Methaqualone, respectively. Probenecid concentration reached the target level of 100 mg kg(-1) in 6 weeks, and removal of Methaqualone to < 100 mg kg(-1) was achieved after 14 weeks. CONCLUSION: Co-composting was effective in reducing soil concentrations of Probenecid and Methaqualone residues to acceptable values. SIGNIFICANCE AND IMPACT OF THE STUDY: Co-composting is a technology that has application in the remediation of pharmaceutical contaminants in soil.

Environmental monitoring in soil contamination and remediation programs: how practitioners are using the Internet to share knowledge.

Internet listservers provide a means for professionals from all sectors of the industry and profession, to communicate and collaborate with each other, as well as other stakeholders (e.g., suppliers, academics, the general public and community members) in real time. This article highlights key Internet listservers in the field of environmental monitoring in soil contamination and remediation and how to subscribe to them. The most active and relevant listservers for environmental scientists, technologists and professionals in the soil contamination and remediation profession are the Bioremediation Discussion Group (BioGroup), Phytonet, Phytoremediation listserver, Groundwater listserver and Environmental Forensics listserver. Other observations and lessons so far from the use of Internet listservers are: (i) that moderators provide an important role in maintaining the level of quality and participation, (ii) do not underestimate the knowledge base held within these, and (iii) if not selected and managed properly, e-mail from listservers can generate an excess of e-mail and waste time.

Application of resazurin for estimating abundance of contaminant-degrading micro-organisms.

AIMS: The aim of the current study was to test whether resazurin changed colour when incubated with a range of organic chemicals used as growth substrates in bioremediation studies and to determine whether resazurin was more effective in estimating microbial growth than turbidity alone (i.e. no resazurin) or use of the dye, methylene blue. METHODS AND RESULTS: Resazurin was incubated with a range of organic chemicals that were used as substrates in an MPN assay. Only 1,2-dichlorobenzene, 2,4-D, glycol sulphite and sulphinol reacted to generate false positives. Resazurin was also used to estimate micro-organisms in a series of bioremediation studies. CONCLUSION: The results showed that resazurin was more sensitive than methylene blue or turbidity alone as an indicator of microbial growth. SIGNIFICANCE AND IMPACT OF THE STUDY: The significance of the current study is that resazurin should be used in MPN assays for estimating contaminant-degrading micro-organisms instead of turbidity alone or other dyes such as methylene blue.

Bioremediation of phenols and polycyclic aromatic hydrocarbons in creosote contaminated soil using ex-situ landtreatment.

Soil from a former creosoting plant containing phenols and polycyclic aromatic hydrocarbons, was remediated using an ex-situ landtreatment process. Total 16 USEPA priority PAH and total phenol were reduced from 290 mg/kg and 40 mg/kg to < 200 mg/kg and 2 mg/kg, respectively. The bioremediation process involved soil mixing, aeration, and slow release fertilizer addition. The indigenous populations of PAH and phenol utilizing populations of microorganisms were shown to increase during the treatment process, indicating that biostimulation was effective. The most extensive degradation was apparent with the 2- and 3-ring PAH, with decreases of 97% and 82%, respectively. The higher molecular weight 3- and 4-ring PAH were degraded at slower rates, with reductions of 45% and 51%, respectively. Six-ring PAH were degraded the least with average reductions of < 35%. The residual concentrations of PAH and total phenol obtained in the study allowed the treated soil to be disposed of as low level contaminated landfill.

The extraction of aged polycyclic aromatic hydrocarbon (PAH) residues from a clay soil using sonication and a Soxhlet procedure: a comparative study.

A sonication method was compared with Soxhlet extraction for recovering polycyclic aromatic hydrocarbons (PAH) from a clay soil that had been contaminated with tar materials for several decades. Using sonication over an 8 h extraction period, maximum extraction of the 16 US EPA priority PAH was obtained with dichloromethane (DCM)-acetone (1 + 1). The same procedure using hexane-acetone (1 + 1) recovered 86% of that obtained using DCM-acetone (1 + 1). PAH recovery was dependent on time of extraction up to a period of 8 h. The sonication procedure showed that individual PAH are extracted at differing rates depending on the number of fused rings in the molecule. Soxhlet extraction [with DCM-acetone (1 + 1)] over an 8 h period recovered 95% of the PAH removed by the sonication procedure using DCM-acetone (1 + 1), indicating that rigorous sonication can achieve PAH recoveries similar to those obtained by Soxhlet extraction. The lower recovery with the Soxhlet extraction was explained by the observed losses of the volatile PAH components after 1-4 h of extraction. The type of solvent used, the length of time of extraction and extraction method influenced the quantification of PAH in the soil. Therefore, the study has implications for PAH analyses in soils and sediments, and particularly for contaminated site assessments where the data from commercial laboratories are being used. The study emphasizes the importance of establishing (and being consistent in the application of) a vigorous extraction, particularly for commercial laboratories that handle samples of soil in batches (at different times) from a single site investigation or remediation process. The strong binding of PAH to soil, forming aged residues, has significant implications for extraction efficiency. This paper illustrates the problem of the underestimation of PAH using the US EPA method 3550, specifically where a surrogate spike is routinely employed and the efficiency of the extraction procedure for aged residues is unknown. The implications of this study for environmental monitoring, particularly where numerous batches of samples from a single site assessment or remediation program are submitted to commercial laboratories, is that it would be advisable for these laboratories to check their existing method's extraction efficiencies by conducting a time course sonication extraction on their particular soil to determine the optimum extraction time.

The anaerobic degradation of endosulfan by indigenous microorganisms from low-oxygen soils and sediments.

Indigenous mixed populations of anaerobic microorganisms from an irrigation tailwater drain and submerged agricultural chemical waste pit readily biodegraded the major isomer of endosulfan (endosulfan I). Endosulfan I was biodegraded to endosulfan diol, a low toxicity degradation product, in the presence of organic carbon sources under anaerobic, methanogenic conditions. While there was extensive degradation (>85%) over the 30 days, there was no significant enhancement of degradation from enriched inocula. This study demonstrates that endosulfan I has the potential to be biodegraded in sediments, in the absence of enriched microorganisms. This is of particular importance since such sediments are prevalent in cotton-growing areas and are typically contaminated with endosulfan residues. The importance of minimizing non-biological losses has also been highlighted as a critical issue in determining anaerobic biodegradation potential. Seals for such incubation vessels must be both oxygen and pollutant impermeable. Teflon-lined butyl rubber provides such a seal because of its resistance to the absorption of volatiles and in preventing volatilization. Moreover, including a 100 mM phosphate buffer in the anaerobic media has reduced non-biological losses from chemical hydrolysis, allowing biodegradation to be assessed.