Predicting bioremediation of hydrocarbons: Laboratory to field scale

There are strong drivers to increasingly adopt bioremediation as an effective technique for risk reduction of hydrocarbon impacted soils. Researchers often rely solely on chemical data to assess bioremediation efficiently, without making use of the numerous biological techniques for assessing microbial performance. Where used, laboratory experiments must be effectively extrapolated to the field scale. The aim of this research was to test laboratory derived data and move to the field scale. In this research, the remediation of over thirty hydrocarbon sites was studied in the laboratory using a range of analytical techniques. At elevated concentrations, the rate of degradation was best described by respiration and the total hydrocarbon concentration in soil. The number of bacterial degraders and heterotrophs as well as quantification of the bioavailable fraction allowed an estimation of how bioremediation would progress. The response of microbial biosensors proved a useful predictor of bioremediation in the absence of other microbial data. Field-scale trials on average took three times as long to reach the same endpoint as the laboratory trial. It is essential that practitioners justify the nature and frequency of sampling when managing remediation projects and estimations can be made using laboratory derived data. The value of bioremediation will be realised when those that practice the technology can offer transparent lines of evidence to explain their decisions.     

Long-range atmospheric transport of three toxaphene congeners across Europe. Modeling by chained single-box FATEMOD program

Background, aims, and scope  Since toxaphene (polychlorocamphene, polychloropinene, or strobane) mixtures were applied for massive insecticide use in the 1960s to replace the use of DDT, some of their congeners have been found at high latitudes far away from the usage areas. Especially polychlorinated bornanes have demonstrated dominating congeners transported by air up to the Arctic areas. Environmental fate modeling has been applied to monitor this phenomenon using parallel zones of atmosphere around the globe as interconnected environments. These zones, shown in many meteorological maps, however, may not be the best way to configure atmospheric transport in air trajectories. The latter could also be covered by connecting a chain of simple model boxes. We aim to study this alternative approach by modeling the trajectory chain using catchment boxes of our FATEMOD model. Polychlorobornanes analyzed in biota of the Barents Sea offered one case to study this modeling alternative, while toxaphene has been and partly still is used massively at southern East Europe and around rivers flowing to the Aral Sea. Materials and methods  Pure model substances of three polychlorobornanes (toxaphene congeners P26, P50, and P62) were synthesized, their environmentally important thermal properties measured by differential scanning calorimetry, as evaluated from literature data, and their temperature dependences estimated by the QSPR programs VPLEST, WATSOLU, and TDLKOW. The evaluated property parameters were used to model their atmospheric long-range transport from toxaphene heavy usage areas in Ukraine and Aral/SyrDarja/AmuDarja region areas, through East Europe and Northern Norway (Finnmarken) to the Barents Sea. The time period used for the emission model was June 1997. Usual weather conditions in June were applied in the model, which was constructed by chaining FATEMOD model boxes of the catchment’s areas along assumed maximal air flow trajectories. Analysis of the three chlorobornanes in toxaphene mixtures function as a basis for the estimates of emission levels caused by its usage. High estimate (A) was taken from contents in a Western product chlorocamphene and low estimate (B) from mean contents in Russian polychloroterpene products to achieve modeled water concentrations. Bioaccumulation to analyzed lipid of aquatic biota at the target region was estimated by using statistical calculation for persistent organic pollutants in literature. Results  The results from model runs A and B (high and low emission estimate) for levels in sea biota were compared to analysis results of samples taken in August 1997 at Barents Sea. The model results (ng g⁻¹ lw): 4–95 in lipid of planktovores and 7–150 in lipid of piscivores, were in fair agreement with the analysis results from August 1997: 21–31 in Themisto libellula (chatka), 26–42 in Boreocadus saida (Polar cod), and 5–27 in Gadus morhua (cod) liver. Discussion  The modeling results indicate that the application of chained simple multimedia catchment boxes on predicted trajectory is a useful method for estimation of volatile airborne persistent chemical exposures to biota in remote areas. For hazard assessment of these pollutants, their properties, especially temperature dependences, must be estimated by a reasonable accuracy. That can be achieved by using measurements in laboratory with pure model compounds and estimation of properties by thermodynamic QSPR methods. The property parameters can be validated by comparing their values at an environmental temperature range with measured or QSPR-estimated values derived by independent methods. The chained box method used for long-range air transport modeling can be more suitable than global parallel zones modeling used earlier, provided that the main airflow trajectories and properties of transported pollutants are predictable enough. Conclusions  Long-range air transport modeling of persistent, especially photo-resistant organic compounds using a chain of joint simple boxes of catchment’s environments is a feasible method to predict concentrations of pollutants at the target area. This is justified from model results compared with analytical measurements in Barents Sea biota in August 1997: three of six modeled values were high and the other three low compared to the analysis results. The order of magnitude level was similar in both modeled (planktovore and piscivore) and observed (chatka and polar cod) values of lipid samples. The obtained results were too limited to firm validation but are sufficient to justify feasibility of the method, which prompts one to perform more studies on this modeling system. Recommendations and perspectives  For assessment of the risk of environmental damages, chemical fate determination is an essential tool for chemical control, e.g., for EU following the REACH rules. The present conclusion of applicability of the chained single-box multimedia modeling can be validated by further studies using analyses of emissions and target biota in various other cases. To achieve useful results, fate models built with databases having automatic steps for most calculations and outputs accessible to all chemical control professionals are essential. Our FATEMOD program catchments at environments and compound properties listed in the database represent a feasible tool for local, regional, and, according our present test results, for global exposure predictions. As an extended use of model, emission estimates can be achieved by reversed modeling from analysis results of samples corresponding to the target area. This article is dedicated to the memory of Professor Alexander B Terentiev (who passed away in November 2006), our true friend. With his Institute of Organo-Element Compounds, Russian Academy of Science, Moscow, he was an important main organizer of the six joint Finnish–Russian seminars (every third year since 1989) on the field (‘Chemistry and Ecology of Organo-Element Compounds’). He prompted us especially to search properties and environmental fates for various polyhalogen compounds. We remember him for his friendly character and great sense of humor.     

Removal of an anionic dye (Acid Blue 92) by coagulation–flocculation using chitosan

Chitosan (a biopolymer) is an aminopolysaccharide that can be used for the treatment of colored solutions by coagulation–flocculation (as an alternative to more conventional processes such as sorption). Acid Blue 92 (a sulfonic dye) was selected as a model dye for verifying chitosan's ability to treat textile wastewater. A preliminary experiment demonstrated that chitosan was more efficient at color removal in tap water than in demineralized water, and that a substantially lower concentration of chitosan could be used with tap water. Dye removal reached up to 99% under optimum concentration; i.e., in terms of the acidic solutions and the stoichiometric ratio between the amine groups of the biopolymer and the sulfonic groups in the dye. The flocs were recovered and the dye was efficiently removed using alkaline solutions (0.001–1 M NaOH solutions) and the biopolymer, re-dissolved in acetic acid solution, was reused in a further treatment cycle.     

Methanogenic activity of woody debris

The paper is devoted to the phenomenon of methanogenic activity of woody debris, i.e., methane production in the course of wood decomposition by fungi, which are not directly involved in methane synthesis but form an initial link in the trophic chain leading to methanogenic archaea. Expert evaluation of probable amounts of methane emission is made. The results show that woody debris is an important global source of this greenhouse gas.     

白腐真菌修复多环芳烃污染土壤及其降解机理的研究进展

介绍了白腐真菌对多环芳烃(PAHs)的代谢途径、降解机理,阐述了白腐真菌修复PAHs污染土壤的影响因素和生态效应,并提出了提高白腐真菌修复效率的措施.白腐真菌主要通过分泌木质素降解酶系(木质家过氧化物酶、锰过氧化物酶和漆酶)来降解PAHs,这些胞外酶可通过开环作用把PAHs代谢成为水溶性较强的醌类中间产物,再由其他微生物降解这些中间产物直至矿化.在白腐真菌的培养过程中.通过对环境因素及营养条件(如温度、pH值、C/N比、微量元素和转速)的优化可提高胞外酶产量.在修复PAHs污染土壤过程中,生物竞争、营养条件和环境因素等均会影响白腐真菌的修复效果.同时,归纳总结了改善白腐真菌修复效果的一些措施,如真菌-细菌联合修复、添加适当的培养基质、添加表面活性剂、直接施用酶制剂和改善营养条件等.     

The effects of residual tetracycline on soil enzymatic activities and plant growth

A pot trial was carried out to investigate the adverse effects of tetracycline (TC) on soil microbial communities, microbial activities, and the growth of ryegrass (Lolium perenne L). The results showed that the presence of TC significantly disturbed the structure of microbial communities and inhibited soil microbial activities in terms of urease, acid phosphatase and dehydrogenase (p < 0.05). Plant biomass was adversely influenced by TC, especially the roots with a reduction of 40% when compared with the control. Furthermore, TC decreased the assimilation of phosphorus by the plant although the concentration of phosphorus was increased by 20% due to decreased plant biomass. TC seemed to increase the concentration of dissolved organic carbon (by 20%) in soil. The findings implied that the agricultural use of animal manure or fishpond sediment containing considerable amounts of antibiotics may give rise to ecological risks.     

Application of Forensic Techniques for Age Dating and Source Identification in Environmental Litigation

A multitude of forensic techniques are available for age dating and source identification, including corrosion models for underground storage tanks, the commercial availability of a compound, chemical associations with discrete types of manufacturing processes, chemical profiling, proprietary additives, stable isotope analysis, degradation models, biomarkers and contaminant transport models. The selection and use of these techniques in environmental litigation must be thoroughly understood and applied to be effective as forensic evidence. When introduced as scientific evidence, the governing assumptions and quality of the data are critically evaluated and frequently successfully challenged. The purpose of this paper is to present an overview of commonly used environmental forensic techniques and their possible applications so that a user can decide which technique or combination of methods is most appropriate for their case.     

Age-dating Diesel Fuel Spills: Using the European Empirical Time-based Model in the U.S.A.

In 1993, a paper was published by Christensen and Larsen that offered a method for determining the age of diesel oil spills in soil (Christensen and Larsen, 1993 Ground Water Mount. R . Fall , 142-149). It presented an empirical time-based model of the degradation of diesel fuel in soils using chemical data gathered at petroleum release sites in Denmark and the Netherlands. Now, evaluation of the validity of the application of this work to subsurface petroleum releases in other countries remains. In the U.S.A., investigations assessing date(s) of release of diesel fuel in soils, e.g. age dating of subsurface petroleum contamination, have considerable interest. Litigation-driven scientific investigations with accompanying expert testimony in a court of law are underway. The number of instances where application of the Christensen and Larsen empirical time-based model to petroleum-contaminated properties is growing in the U.S.A. This paper presents two case studies which evaluate the applicability of the Christensen and Larsen empirical time-based model to petroleum-contaminated properties in general. It illustrates the approach using gas chromatographic data from two recently-completed projects evaluating the applicability of the Christensen and Larsen model to a No. 2 fuel oil/diesel fuel surface spill in the U.S.A. Results showed that the application of the model to petroleum-contaminated soils was scientifically valid, provided its applicability was evaluated using hypothesis testing for specific changes in the characteristics of the petroleum hydrocarbon distribution in a number of soil samples collected over time at one site. The paper offers observations on the application of the Christensen and Larsen model to petroleum found in the light non-aqueous phase liquid (LNAPL) phase and groundwater.     

Biotic transformation of anticoccidials in soil using a lab-scale bio-reactor as a precursor-tool

Two anticoccidial agents, salinomycin and robenidine, heavily used in the worldwide veterinary meat production, were investigated for their potential biotic degradation by cultured soil bacteria. The degradation-study was performed in lab-scale bio-reactors under aerobic and anaerobic conditions incubated for 200 h with a mixed culture of soil bacteria. Samples were analyzed by LC-MS/MS and potential transformation products were tentatively identified. Salinomycin was degraded under aerobic conditions and traces could be found after 200 h, however, seems more persistent under anaerobic conditions. Four transformation products of salinomycin were discovered. Robenidine was degraded under aerobic and anaerobic conditions, however, traces of robenidine were observed after 200 h. Five biotic transformation products of robenidine were discovered.     

Propiconazole inhibits the sterol 14α-demethylase in Glomus irregulare like in phytopathogenic fungi

The increasing concentrations impact (0.02, 0.2 and 2 mg L⁻¹) of a Sterol Biosynthesis Inhibitor (SBI) fungicide, propiconazole, was evaluated on development and sterol metabolism of two non-target organisms: mycorrhizal or non-mycorrhizal transformed chicory roots and the arbuscular mycorrhizal fungus (AMF) Glomus irregulare using monoxenic cultures. In this work, we provide the first evidence of a direct impact of propiconazole on the AMF by disturbing its sterol metabolism. A significant decrease in end-products sterols contents (24-methylcholesterol and in 24-ethylcholesterol) was observed concomitantly to a 24-methylenedihydrolanosterol accumulation indicating the inhibition of a key enzyme in sterol biosynthesis pathway, the sterol 14α-demethylase like in phytopathogenic fungi. A decrease in end-product sterol contents in propiconazole-treated roots was also observed suggesting a slowing down of the sterol metabolism in plant. Taken together, our findings suggest that the inhibition of the both AM symbiotic partners development by propiconazole results from their sterol metabolism alterations.