Sorption of tributyltin in seawater by municipal solid waste compost

The use of municipal solid waste (MSW) compost as a sorbent for tributyltin (TBT) in seawater was investigated. TBT‐contaminated seawater, both artificially prepared and that collected from Msida Creek yacht marina (Malta), was allowed to percolate through untreated and water‐washed columns of compost and then analysed for organotins using gas chromatography‐flame photometric detection. About 90% of dissolved TBT ranging in concentration from about 800 to 8000 ng_Snl^?1 was sorbed by treating 500 ml solutions with 100 g untreated compost. On the other hand, no detectable breakthrough of TBT was observed from compost that had previously been washed by water to remove soluble organic matter. Breakthrough of TBT from unwashed compost is thought to be due to formation of complexes between the soluble organic matter in compost and aquated TBT, which renders the organotin more hydrophilic. The use of washed MSW compost as sorbent for the purification of TBT‐contaminated waters generated in large quantity during hull‐cleaning activities in drydocks is suggested as a mitigatory measure against the impact of TBT on the coastal marine environment. Copyright © 2001 John Wiley & Sons, Ltd.     

Tributyltin biomonitoring using prosobranchs as sentinel organisms

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produce a variety of pathological reactions in animals. A reliable biomonitoring method to assess the degree of environmental TBT pollution has been described based on investigations of virilization phenomena in prosobranch snails (Mollusca: Gastropoda). Examples are the imposex phenomenon in marine and freshwater species, the intersex reaction in littorinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. The degree of imposex or intersex in populations is determined by different biomonitoring indices which allow to assess the TBT pollution of the environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Ireland indicating that there is still a continuing threat to sensitive marine organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena seem due to an inhibition of the cytochrome P-450 dependent aromatase by this organotin compound.     

Tributyltin biomonitoring using prosobranchs as sentinel organisms

Tributyltin (TBT) compounds, some of the most toxic xenobiotics, produce a variety of pathological reactions in animals. A reliable biomonitoring method to assess the degree of environmental TBT pollution has been described based on investigations of virilization phenomena in prosobranch snails (Mollusca: Gastropoda). Examples are the imposex phenomenon in marine and freshwater species, the intersex reaction in littorinids and the reduction of female sexual glands and offspring numbers in further species resulting mainly in a sterilization of females. The degree of imposex or intersex in populations is determined by different biomonitoring indices which allow to assess the TBT pollution of the environment at low costs with high precision. The effectiveness of TBT legislations is analysed by extensive surveys in France and Ireland indicating that there is still a continuing threat to sensitive marine organisms. TBT disturbs the biosynthesis of steroid hormones on the level of estrogen biosynthesis. The observed virilization phenomena seem due to an inhibition of the cytochrome P-450 dependent aromatase by this organotin compound.     

Bioremediation of hydrocarbons contaminated waters and soils: monitoring by luminescent bacteria test

Bioremediation has proven successful in numerous applications to petroleum hydrocarbons or chlorinated aromatic hydrocarbons contaminated soils. There is increasing interest in application of biotoxicity tests for ecological assessment and for supporting management decisions for remediation. Luminescent assays, light-emitting bacteria in particular, can be a suitable tool for environmental analysis, and in vivo luminescence is a rapid and precise indicator of the toxic effects of xenobiotic on micro-organisms. In this study, three different strains of marine bioluminescent bacteria have been employed to follow the changes in biotoxicity occurring during the laboratory scale bioremediation of water and soil samples contaminated by hydrocarbons and collected at an industrial area. The degradation was made by hydrocarbons degrading bacteria, both of commercial sources and isolated from polluted water and soils. The samples were treated for 45 days. The toxicity of the samples, before and after the bioremediation, was determined directly on water samples or on the extracts of soil samples. The yield of extraction by different solvents (acetone, dioxane, ethanol and dichloromethane) was evaluated by the bioluminescent test. The measurements were carried out using a microplate format both for short time of contact (60?minutes, acute toxicity) and for longer time intervals (24 hours, chronic toxicity). The results have been expressed as percentage of inhibition with respect to the blank emission (100% emission). Original and treated samples have been analysed by gas chromatography to assess the hydrocarbons (C?>?12 and Poly Chlorinated Biphenyls, PCB) content. The autochthonous bacteria isolated from polluted samples proved less effective, due to the short time for selection in remediation activity with respect to the commercial ones, but their capacity to degrade long chain hydrocarbons was satisfactory. The presented laboratory study can be applied also in case of on-field conditions.     

Isotope dilution analysis mass spectrometry for the routine measurement of butyltin compounds in marine environmental and biological samples

The highly qualified primary method of species-specific isotope dilution analysis has been employed in this work to evaluate for the first time the levels of butyltin compounds in the estuary of the river Eo (Northwest Spain) where there is, since many years, a high oyster farming activity. A spike solution containing mono-, di- and tributyltin enriched in ¹¹⁹Sn allowed the simultaneous determination of the three compounds in different marine environmental and biological samples collected in this area (seawater samples, sediments and biological tissues of four different marine species). The results obtained in this work showed toxic TBT levels for many marine species in 45% of the seawater samples analyzed whereas significant organotin concentrations were found to be obtained only in one of the sediments analyzed. On the other hand, TBT levels ranging from 20 to almost 200 ng g^− 1 (dry weight) were obtained in the different biological tissues analyzed demonstrating the bioaccumulation of organotin compounds in certain marine species.     

Toxicity of butyltin,phenyltin and inorganic tin compounds to sulfate‐reducing bacteria isolated from anoxic marine sediments

The toxicity of butyltin, phenyltin and inorganic tin compounds to three pure strains of sulfate‐reducing bacteria (SRB), isolated from a tributyltin (TBT)‐polluted sediment, was determined. The isolated strains were identified as belonging to the genus Desulfovibrio. A new toxicological index (GR₂₅) was developed to assay the toxicity of organotin compounds. Deleterious effects on suspended anaerobic cell cultures were observed for concentrations ranging between 500 and 600 µM for tin tetrachloride, 55 and 260 µM for triorganotins, 30 and 90 µM for diorganotins, and 1 and 6 µM for mono‐organotins. Whereas the number of substituents influenced the toxicity of organotins, the type of substituent (butyl or phenyl) proved to have little or no impact. Trisubstituted compounds (tributyl‐ and triphenyl‐tin) were less toxic to these strains of SRB than the monosubstituted forms (monobutyl‐ and monophenyl‐tin). This is the opposite trend to that currently reported for aerobic organisms. Under the given anoxic conditions, the toxicity of organotin compounds obtained yielded a significant negative correlation with the total surface area (TSA) of the tested molecules. Comparison of the TBT toxicity data observed for different microbial groups suggests that the tolerance of bacteria to organotin compounds might be related to organotin–cell wall interactions as well as to aerobic or anaerobic metabolise pathways. Copyright © 2000 John Wiley & Sons, Ltd.     

Life‐cycle toxicity of dibutyltin to the sheepshead minnow (Cyprinodon variegatus) and implications of the ubiquitous tributyltin impurity in test material

Dibutyltin (DBT) is used in the plastics polymerization process as a catalyst in polyvinyl chloride (PVC) products and is the primary degradation product of tributyltin (TBT), an antifoulant in marine paint. DBT and other organotin compounds make their way into the environment through antifoulants, PVC processing plants, and PVC products maintained in water and water‐handling systems. A flow‐through saltwater life‐cycle toxicity test was conducted to determine the chronic effect of DBT to the sheepshead minnow (Cyprinodon variegatus Lacepede), an estuarine species. Embryos were monitored through hatch, maturation, growth, and reproduction in DBT concentrations of 158, 286, 453, 887, and 1510 µg l^?1. Progeny were monitored for survival as embryos and fry/juveniles, and growth for 30 days post‐isolation. Mean length of parental generation fish was significantly reduced on day 30 at DBT concentrations ≥887 µg l^?1, setting the lowest observable effect concentration (LOEC) at 887 µg l^?1 and the no observable effect concentration (NOEC) at 453 µg l^?1. Fecundity, as egg viability, was significantly reduced at the LOEC. Survival of parental and progeny generation embryos and mean length, wet weight and dry weight of progeny generation juveniles were not significantly affected at concentrations ≤LOEC. TBT, a toxic impurity in DBT reversibly produced in DBT by the process of comproportionation, was also monitored throughout this study. Comparing measured levels of TBT in this study with levels exerting toxic effects in an earlier TBT life‐cycle study with C. variegatus suggests biological responses in this study were likely due to the TBT impurity and not to DBT alone. Results indicate that TBT impurity as low as 0.1% may have a significant influence on the perceived toxicity of DBT and that spontaneous production of TBT in DBT may be the major source of biological toxicity of DBT. Copyright © 2003 John Wiley & Sons, Ltd.     

Biodegradation of Crude Oil from the BP Oil Spill in the Marsh Sediments of Southeast Louisiana, USA

The significant challenges presented by the April 20, 2010 explosion, sinking, and subsequent oil spill of the Deepwater Horizon drilling platform in Canyon Block 252 about 52 miles southeast of Venice, LA, USA greatly impacted Louisiana??s coastal ecosystem including the sea food industry, recreational fishing, and tourism. The short-term and long-term impact of this oil spill are significant, and the Deepwater Horizon spill is potentially both an economic and an ecological disaster. Microbes present in the water column and sediments have the potential to degrade the oil. Oil degradation could be enhanced by biostimulation method. The conventional approach to bioremediation of petroleum hydrocarbon is based on aerobic processes. Anaerobic bioremediation has been tested only in a very few cases and is still considered experimental. The currently practiced conventional in situ biorestoration of petroleum-contaminated soils and ground water relies on the supply of oxygen to the subsurface to enhance natural aerobic processes to remediate the contaminants. However, anaerobic microbial processes can be significant in oxygen-depleted subsurface environments and sediments that are contaminated with petroleum-based compounds such as oil-impacted marshes in Louisiana. The goal of this work was to identify the right conditions for the indigenous anaerobic bacteria present in the contaminated sites to enhance degradation of petroleum hydrocarbons. We evaluated the ability of microorganisms under a variety of electron acceptor conditions to degrade petroleum hydrocarbons. Researched microbial systems include sulfate-, nitrate-reducing bacteria, and fermenting bacteria. The results indicated that anaerobic bacteria are viable candidates for bioremediation. Enhanced biodegradation was attained under mixed electron acceptor conditions, where various electron-accepting anaerobes coexisted and aided in degrading complex petroleum hydrocarbon components of marsh sediments in the coastal Louisiana. Significant degradation of oil also occurred under sulfate-reducing and nitrate-reducing conditions.     

Potential use of cyclodextrins in soil bioremediation

Bioavailability and toxic effect of contaminants are the main limitations during soil bioremediation. Cyclodextrins may influence bioavailability of the contaminants during biodegradation and also toxicity of the pollutant on soil microbes and plants since their ability to form inclusion complei with organic compounds. The effect of cyclodextrins on bioremediation and on toxic effect of hydrocarbons was investigated by testing the activity of hydrocarbon degrading microflora and of plant growth. The effect of cyclodextrins could be demonstrated in both cases: biodegradation of hydrocarbons could be enhanced and toxic effect of hydrocarbons on plants and soil microbes could be decreased by adding cyclodextrins.     

Respirometric analysis of the biodegradation of organic contaminants in soil and water

Client-funded bench-scale investigations concerning the likelihood of successfully applying biological remediation to hazardous wastes must be cost-effective, and they usually need only determine if biodegradation is likely to occur on site. To assess the potential for stimulating biodegradation, biochemical oxygen demand (BOD) was used to continuously monitor bacterial respiration during growth on mixed organic wastes from contaminated water and soil. Continuously collected oxygen-consumption data provided information on the overall metabolic activity of the resident bacterial population and permitted direct observation of the cessation of microbial respiratory activity and, thus, the termination of aerobic degradation. The correlation of biological oxygen utilization with biodegradation was confirmed using independent analytical methods. Continuous, long-term BOD analysis was applied to bench-scale studies to assess the biodegradation of mixed organic wastes from contaminated sites and industrial waste effluents. This information was used to make an initial determination regarding the need to further explore bioremediation as a potential remedial-action technology using on-site, pilot-scale testing.     

Pollutant Degrading Enzyme: Catalytic Mechanisms and Their Expanded Applications

The treatment of environmental pollution by microorganisms and their enzymes is an innovative and socially acceptable alternative to traditional remediation approaches. Microbial biodegradation is often characterized with high efficiency as this process is catalyzed via degrading enzymes. Various naturally isolated microorganisms were demonstrated to have considerable ability to mitigate many environmental pollutants without external intervention. However, only a small fraction of these strains are studied in detail to reveal the mechanisms at the enzyme level, which strictly limited the enhancement of the degradation efficiency. Accordingly, this review will comprehensively summarize the function of various degrading enzymes with an emphasis on catalytic mechanisms. We also inspect the expanded applications of these pollutant-degrading enzymes in industrial processes. An in-depth understanding of the catalytic mechanism of enzymes will be beneficial for exploring and exploiting more degrading enzyme resources and thus ameliorate concerns associated with the ineffective biodegradation of recalcitrant and xenobiotic contaminants with the help of gene-editing technology and synthetic biology.     

Kinetic monitoring of trisubstituted organotins in soil after sewage sludge application

Organotin compounds (OTC) are widely used for their biocidal effects in various agricultural or industrial activities, leading to their environmental presence. Among the organotin species, tributyltin (TBT) and triphenyltin (TPhT) are the most used and are generally considered the most toxic. So it is important to understand their behaviour in soils and obtain data about their persistence and phytoavailability. Many works deal with OTC speciation in various matrices, but few are concerned with OTC degradation in soil. The present study focuses on kinetic monitoring of TBT and TPhT in an agricultural soil. These compounds were introduced into the soil by the way of spiked sewage sludge, simulating agricultural practice and diffuse contamination. The influence of time and initial OTC concentration on the species preservation was evaluated. TBT concentration was shown to have a positive effect on TBT preservation. Corresponding half‐lives were calculated. They were 6 ± 1 days and over 39 days for TPhT and TBT, respectively. Degradation compounds, mono‐ and dibutyltin, and mono‐ and diphenyltin, were produced by both direct and successive dealkyl and dearylation processes. Copyright © 2008 John Wiley & Sons, Ltd.     

Adsorption characteristics of tributyltin on municipal solid waste compost

The sorption behaviour of tributyltin (TBT) from reconstituted seawater onto municipal solid waste (MSW) compost was investigated to give first insights into the equilibrium and kinetic behaviour of this process. The rate of adsorption, the influence of pH, and the adsorbate hydrophobicity on the partitioning process were investigated. Adsorption kinetics indicated an initial fast rate of adsorption of TBT followed by a slower rate. The similarity of Freundlich sorption and desorption coefficients for TBT showed that the sorption process is also reversible, similar to that for the adsorption of TBT onto marine sediments. It was found that the adsorption capacity for TBT onto compost was highest at pH 6.7, and for other organotins it increased with increasing adsorbate hydrophobicity, following the trend tripropyltin < TBT < tripentyltin. The use of washed MSW compost as a sorbent for the purification of TBT‐contaminated wash waters as generated in large quantities during hull cleaning in dry docks is suggested as a mitigatory measure against pollution of the marine environment by TBT. Calculations suggest that modest amounts of compost will likely be required to treat the contaminated wastewaters generated from the Malta dry docks if a multiple batch system is adopted. Copyright © 2005 John Wiley & Sons, Ltd.     

Anthracene and Pyrene Biodegradation Performance of Marine Sponge Symbiont Bacteria Consortium

Every petroleum-processing plant produces sewage sludge containing several types of polycyclic aromatic hydrocarbons (PAHs). The degradation of PAHs via physical, biological, and chemical methods is not yet efficient. Among biological methods, the use of marine sponge symbiont bacteria is considered an alternative and promising approach in the degradation of and reduction in PAHs. This study aimed to explore the potential performance of a consortium of sponge symbiont bacteria in degrading anthracene and pyrene. Three bacterial species (Bacillus pumilus strain GLB197, Pseudomonas stutzeri strain SLG510A3-8, and Acinetobacter calcoaceticus strain SLCDA 976) were mixed to form the consortium. The interaction between the bacterial consortium suspension and PAH components was measured at 5 day intervals for 25 days. The biodegradation performance of bacteria on PAH samples was determined on the basis of five biodegradation parameters. The analysis results showed a decrease in the concentration of anthracene (21.89%) and pyrene (7.71%), equivalent to a ratio of 3:1, followed by a decrease in the abundance of anthracene (60.30%) and pyrene (27.52%), equivalent to a ratio of 2:1. The level of pyrene degradation was lower than that of the anthracene due to fact that pyrene is more toxic and has a more stable molecular structure, which hinders its metabolism by bacterial cells. The products from the biodegradation of the two PAHs are alcohols, aldehydes, carboxylic acids, and a small proportion of aromatic hydrocarbon components.     

Preliminary evidence for in vitro methylation of tributyltin in a marine sediment

Recent reports from our laboratory on the occurrence of methylbutyltins in marine sediments and seawater suggest that these compounds are formed in the environment by the methylation of both tributyltin (TBT) and that­of its degradation products, i.e. dibutyltin and monobutyltin, to give Me_nBu_(4?n)Sn for which n = 1, 2 and 3 respectively. We investigated the possibility of inducing methylation of TBT in seawater–sediment mixtures in experiments carried out in vitro using environmental materials collected from a yacht marina in Msida, Malta. Three water–sediment mixtures, which were shown to contain TBT, dibutyltin and monobutyltin but no other organotins, were spiked with tributyltin chloride (90 mg in 100 ml sea‐water/100 ml sediment); to one mixture was added sodium acetate and to another methanol, to act as possible additional carbon sources, and all mixtures were allowed to stand at 25 °C in stoppered clear‐glass bottles in diffused light for a maximum of 315 days. Speciation and quantification of organotins was performed using aqueous phase boroethylation with simultaneous solvent extraction followed by gas chromatography with flame photometric detection. The atmosphere inside the bottles quickly became reducing with abundant presence of H₂S, and after an induction period of about 112 days, and only in the reaction mixture containing methanol, methyltributyltin (MeBu₃Sn) was observed in both sediment (maximum concentration 0.87 µg_Sn g^?1) and overlying water (maximum concentration 6.0 µg_Sn l^?1). The minimum conversion yield of TBT into MeBu₃Sn was estimated to be 0.3%. MeBu₃Sn has a significantly lower affinity for sediment than TBT and, therefore, is more mobile in the marine environment, possibly also migrating into the atmosphere to generate a hitherto unsuspected flux of organotin into that phase. Copyright © 2001 John Wiley & Sons, Ltd.     

Application of Biosurfactant from Sphingobacterium spiritivorum AS43 in the Biodegradation of Used Lubricating Oil

This study aimed at investigating the application of biosurfactant from Sphingobacterium spiritivorum AS43 using molasses as a substrate and fertilizer to enhance the biodegradation of used lubricating oil (ULO). The cell surface hydrophobicity of bacteria, the emulsification activity, and the biodegradation efficiency of ULO were measured. The bacterial adhesion in the hydrocarbon test was used to denote the cell surface hydrophobicity of the used bacterial species. The results indicate a strong correlation between cell surface hydrophobicity, emulsification activity, and the degree of ULO biodegradation. The maximum degradation of ULO (62 %) was observed when either 1.5 % (w/v) of biosurfactant or fertilizer was added. The results also revealed that biosurfactants alone are capable of promoting biodegradation to a large extent without added fertilizer. The data indicate the potential for biosurfactant production by using low-cost substrate for application in the bioremediation of soils contaminated with petroleum hydrocarbons or oils.     

Cyanide Biodegradation by Trichoderma harzianum and Cyanide Hydratase Network Analysis

Cyanide is a poisonous and dangerous chemical that binds to metals in metalloenzymes, especially cytochrome C oxidase and, thus, interferes with their functionalities. Different pathways and enzymes are involved during cyanide biodegradation, and cyanide hydratase is one of the enzymes that is involved in such a process. In this study, cyanide resistance and cyanide degradation were studied using 24 fungal strains in order to find the strain with the best capacity for cyanide bioremediation. To confirm the capacity of the tested strains, cyano-bioremediation and the presence of the gene that is responsible for the cyanide detoxification was assessed. From the tested organisms, Trichoderma harzianum (T. harzianum) had a significant capability to resist and degrade cyanide at a 15 mM concentration, where it achieved an efficiency of 75% in 7 days. The gene network analysis of enzymes that are involved in cyanide degradation revealed the involvement of cyanide hydratase, dipeptidase, carbon–nitrogen hydrolase-like protein, and ATP adenylyltransferase. This study revealed that T. harzianum was more efficient in degrading cyanide than the other tested fungal organisms, and molecular analysis confirmed the experimental observations.     

Emission to air of volatile organotins from tributyltin‐contaminated harbour sediments

An analytical method for determining the presence in air of volatile forms (e.g. chlorides) of tributyltin (TBT) and that of methylbutyltins Me _nBu_(4?n)Sn (n = 1–3) was developed and used to establish whether dredged harbour sediments contaminated with TBT served as sources of air pollution with respect to organotin compounds. The method was based on active sampling of the air being analysed and sorption of analytes onto Poropak‐N. Sorbed methylbutyltins were extracted with dichloromethane and analysed by gas chromatography using flame photometric detection. Other butyltins were converted into butyltin hydrides prior to analysis by gas chromatography. It was shown that TBT‐contaminated sediments from Marsamxett Harbour, Malta, placed in 0.5 l chambers through which air was displaced by continuous pumping for 11 days released mainly methylbutyltins, with concentrations (as tin) reaching maximum 48 h mean values of 8.7 (Me₃BuSn), 22.1 (Me₂Bu₂Sn) and 93.0 ng m^?3(MeBu₃Sn) being measured. Other volatile forms of TBT, dibutyltin and monobutyltin were detected in the headspace air, but very infrequently and at much lower tin concentrations (<2 ng m^?3). It was also shown that methylbutyltins dissolved in sea‐water ([Sn] = 0.2 to 400 ng l^?1) were very difficult to exsolve from this medium, even on prolonged evaporation of the solutions using mechanical agitation and active ventilation. The results suggest that emission of methylbutyltins from contaminated sediments probably occurs only from the surface of the material. The environmental implications of these findings in the management of TBT‐polluted harbour sediments are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Speciation of butyltin compounds in marine sediments with headspace solid phase microextraction and gas chromatography mass spectrometry

A method for the determination of organotin compounds (monobutyl = MBT, dibutyl = DBT, and tributyltin = TBT) in marine sediments by headspace Solid Phase Microextraction (SPME) has been developed. The analytical procedure involved 1) extraction of TBT, DBT and MBT from sediments with HCl and methanol mixture, 2) in situ derivatization with sodium tetraethylborate and 3) headspace SPME extraction using a fiber coated with poly(dimethylsiloxane). The derivatized organotin compounds were desorbed into the splitless injector and simultaneously analyzed by gas chromatography - mass spectrometry. The analytical method was optimized with respect to derivatization reaction and extraction conditions. The detection limits obtained for MBT, DBT and TBT ranged from 730 to 969 pg/g as Sn dry weight. Linear calibration curves were obtained for all analytes in the range of 30-1000 ng/L as Sn. Analysis of a standard reference sediment (CRM 462) demonstrates the suitability of this method for the determination of butyltin compounds in marine sediments. The application to the determination of TBT, DBT and MBT in a coastal marine sediment is shown.