Degradation Of Tributyltin Research Articles

Study of photocatalytic degradation of tributyltin, dibutylin and monobutyltin in water and marine sediments

This study reports on the first assessment of the treatment of sediments contaminated by organotin compounds using heterogeneous photocatalysis. Photocatalysis of organotins in water was carried out under realistic concentration conditions (μgL−1). Degradation compounds were analyzed by GC-ICP-MS; a quasi-complete degradation of tributyltin (TBT) in water (99.8%) was achieved after 30min of photocatalytic treatment. The degradation by photolysis was about (10%) in the same conditions. For the first time decontamination of highly polluted marine sediments (certified reference material and harbor sediments) by photocatalysis proves that the use of UV and the production of hydroxyl radicals are an efficient way to treat organotins adsorbed onto marine sediment despite the complexity of the matrix. In sediment, TBT degradation yield ranged from 32% to 37% after only 2h of irradiation (TiO2–UV) and the by-products: dibutyltin (DBT) and monobutyltin (MBT) were degraded very rapidly in comparison with TBT. It was shown that during photocatalysis of organotins in sediments, the hydroxyl radical attack and photolysis are the two ways for the degradation of adsorbed TBT.

The use of isotopically enriched tin tracers to follow the transformation of organotin compounds in landfill leachate

Landfill leachates are an important pool of organotin compounds (OTCs). Several studies have been performed on the occurrence of OTCs in landfill leachates, but only a few of them report degradation and biomethylation processes by bacteria. In the present study transformation of OTCs in landfill leachate was investigated under simulated landfill conditions over a time span of six months. The degradation and biomethylation processes of OTCs were followed by the use of isotopically enriched tin tracers, namely 117Sn-enriched tributyltin (TBT), 119Sn-enriched dibutyltin (DBT), 117Sn-enriched SnCl2, 117Sn-enriched SnCl4 and a 119Sn-enriched butyltin mix containing TBT, DBT and monobutyltin (MBT). Transformation of OTCs in spiked leachates was followed at m/z of the enriched spikes and at m/z 120, which allowed simultaneous observation of the transformation of OTCs in the leachate itself and of the added spike. In parallel, these processes were also monitored in a non-spiked leachate sample at m/z 120. Quantification of OTCs was performed by gas chromatography – inductively coupled plasma mass spectrometry (GC-ICP-MS). To discriminate the biotic and abiotic transformations of OTCs and inorganic tin species, sterilization of leachate was also performed and data compared to non-sterilized samples. During the course of the experiment the microbial degradation of TBT was clearly manifested in Sn-enriched spiked leachate samples, while abiotic pathway of degradation was observed for DBT. Biomethylation process was also observed in the leachate spiked with Sn-enriched Sn2+ or Sn4+, in concentrations close to those found for total tin in landfill leachates. Monomethyltin (MMeT) was formed first. Stepwise alkylation resulted in dimethyltin (DMeT) and trimethyltin (TMeT) species formation. Hydrolysis of Sn2+ and Sn4+ species was found to be a limiting factor which controlled the extent of methyltin formation. The results of the present investigation importantly contribute to a better understanding of the processes that OTCs undergo in leachates, and provide useful information to managers of landfills in taking measures necessary to prevent the release of toxic methyltin species to the nearby environment.

Baseline of the butyltin distribution in surface sediments (0–20 cm) of the Elbe estuary (Germany, 2011)

The concentrations of the butyltin (BT) species tributyltin (TBT), dibutyltin (DBT), and monobutyltin (MBT) were measured in the surface sediments (0–20cm) at 29 sites of the Elbe estuary in 2011. TBT values ranged from ‘undetectable’ to 41ngSng−1 dry weight (d.w.) with the two highest values measured in the inner section of the estuary near the port of Hamburg (32 and 41ngSng−1 d.w.). TBT, DBT, and MBT showed significant decreases towards the estuarine mouth (Spearman’s rho −0.660, −0.685, and −0.583, respectively, p<0.001). The degradation of TBT, assessed by the BT degradation index (BDI), showed a rising trend from the port of Hamburg towards the mouth of the estuary, though not a significant one (Spearman’s correlation, p=0.066). Annual sedimentation rates did not show any significant correlations (Spearman’s correlation) to BT pollution or to the butyltin degradation index (BDI).

An easy, rapid and inexpensive method to monitor tributyltin (TBT) toxicity in the laboratory

Tributyltin (TBT) contamination remains a major problem worldwide. Many laboratories are committed to the development of remediation methodologies that could help reduce the negative impact of this compound in the environment. Furthermore, it is important to have at hand simple methodologies for evaluating TBT toxicity in the laboratory, besides the use of complex and costly analytical instrumentation. With that purpose, a method was adapted that is based on the inhibition of growth of an indicator strain, Micrococcus luteus ATCC 9341, under TBT. Different types of matrices, of TBT concentrations and sample treatments were tested. The results herein reported show that the bioassay method can be applied for both aqueous and soil samples and also for a high range of TBT concentrations (at least up to 500 μmol/L). Besides being cheap and easy to perform, it can be performed in any laboratory. Additionally, one possible application of the method to monitor TBT degradation is presented as an example.

Trace elements in the sediments of a large Mediterranean marina (Port Camargue, France): Levels and contamination history

The study of trace elements (Cu, Zn, Pb, As, Hg) and butyltin concentrations in the sediments of Port Camargue enabled assessment of the levels and history of the contamination of the largest European marina linked with the use of antifouling paints. Surface sediments near the boat maintenance area were heavily contaminated with up to 1497μgg−1 of Cu, 475μgg−1 of Zn, 0.82μgg−1 of Hg, 94μgg−1 of Pb and over 10,000ngSng−1 of tributyltin (TBT). High concentrations of Hg and TBT indicate ongoing sources of these elements despite the ban on their use as biocides in paints. Sediment cores provided records of contamination since 1969. The peak concentrations of As, Hg, Pb and TBT in the sediment profile reflect their presence on boat hulls when the marina was built at the end of the 1960s. Degradation of TBT in the sediments near the boat maintenance area is slow compared to other less contaminated area of the marina.

Removal Processes for Tributyltin During Municipal Wastewater Treatment

The fate and behaviour of tributyltin (TBT) at two wastewater treatment works was examined. Both sites had two inlet streams, and each utilised high rate biological filters (biofilters) on one the streams, before treatment of the combined flows on trickling filters, with one having additional tertiary processes, installed to remove ammonia and solids. The study was designed to determine if these processes enhanced the removal of TBT. Degradation of TBT was observed in one of the biofilters, possibly as a result of temperature and hydraulic loading. At the treatment works with tertiary processes, the mass flux showed the overall removal of TBT was 68 %, predominantly due to removal with solids in the primary settlement processes. However, overall removal of 95 % was observed in the conventional trickling filter works with 94 % of this due to biodegradation in the trickling filter. The two works both removed TBT, but at different treatment stages and by different processes. Differences in the form (solubility) of TBT in the influent may have attributed to this, although further understanding of factors controlling degradation would allow for a more complete assessment of the potential of biological processes to remove hazardous compounds from wastewaters.

Anionic surfactant enhanced bacterial degradation of tributyltin in soil

The effect of an anionic surfactant, sodium dihexylsulfosuccinate (SDHS) addition on remediation of tributyltin (TBT) contaminated soil was investigated. Aerobic soil-slurry batch experiments were used to determine the adsorption, desorption, and bacterial degradation of TBT as well as its metabolites such as dibutyltin (DBT) and monobutyltin (MBT). The extent of butyltin adsorption over the concentration range of 1–100 mg Sn l−1 was in the order of MBT > DBT > TBT. The sub-critical micelle concentration (CMC) of SDHS (i.e., 10 mM) did not increase the amounts of desorbed TBT at the beginning of experiment, however, it enhanced the bacterial degradation of 100 mg Sn kg−1 TBT as seen from the increasing amounts of DBT and MBT in the liquid phase after 2 weeks. At the same time, the desorbed TBT was re-adsorbed to the soil in the experiment without SDHS. The complex of TBT and SDHS monomers was expected to enhance the interaction of TBT with indigenous soil bacteria. At supra-CMC SDHS (i.e., 70 mM), the desorbed TBT was not degraded because high concentrations of TBT and SDHS posed synergistic toxic effects to the bacteria. Consequently, the presence of anionic surfactant at sub-CMCs will be beneficial for the cleanup of TBT contaminated sites.

Hermit crabs as bioindicators of recent tributyltin (TBT) contamination

Evaluation of the assimilation pathway and depuration time of a given pollutant by aquatic species is important to understand the dynamics of this substance in the biota, and to search for potential ecological indicators. In the present study, the uptake pathway and depuration time and rate of the pollutant tributyltin (TBT) were investigated in the omnivorous hermit crab ( Clibanarius vittatus). The assimilation and uptake pathway were investigated using hermit crabs collected in an area free of TBT. The crabs were held in the laboratory for 45 days, under one of four treatments: procedural control (PC) – water and food without TBT; T1 – water with and food without TBT; T2 – water without and food with TBT; and T3 – water and food with TBT. To determine the depuration time, the crabs were collected in a contaminated area, maintained in the laboratory with clean water, and removed every 15 days for 120 days. The concentrations of TBT and DBT (dibutyltin) were determined by chromatographic analysis. The TBT was taken up by the crabs mainly via food, and the presence of DBT in crab tissues was hypothesized to result from internal TBT degradation. TBT (as well as DBT) was depurated rapidly by C. vittatus. After approximately 30 days, the initial concentration of 111 ± 36 ng Sn g −1 w. w. decreased to 3 ± 3 ng Sn g −1 w. w., and after 75 days the TBT concentration was below the detection limit. The same pattern was recorded for DBT, which showed a higher depuration rate than TBT. The rapid TBT and DBT depuration is useful information, since C. vittatus and possibly other hermit crabs may be used as indicators of recent or recycled environmental contamination.

Baseline of butyltin contamination in sediments of Sundarban mangrove wetland and adjacent coastal regions, India

The study reports the first assessment for the quantification and speciation of butyltins (BTs) in surface marine sediment samples (0-5 cm) from intertidal mudflats of Sundarban mangrove wetland along with the Hugli (Ganges) river basin, eastern coastal part of India. Concentrations of tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) were monitored at 16 stations and present at all study areas, in concentrations in sediments up to 84.2, 26.4 and 48.0 ng g(-1) of TBT, DBT and MBT, respectively. Significant correlations were obtained between MBT and DBT (r = 0.62, p = 0.01) and DBT and TBT (r = 0.54, p = 0.03). Calculated BT degradation index (BDI) values indicated recent contamination of BTs at 8 stations, and suggested either no degradation of TBT or very recent degradation at a 4 further stations. Additionally, BDI values also indicated no recent inputs of BTs in 4 stations (only MBT present in one of these stations). High concentrations of BTs, particularly TBT, have the potential to induce ecotoxicological impacts based on levels specified in Australian Sediment Quality Guidelines (SQGs). This study indicated that the majority of the analyzed stations were in the highest range of priority, due to high TBT concentrations.

Biochemistry of TBT-Degrading Marine Pseudomonads Isolated from Indian Coastal Waters

Tributyltin (TBT) is a very effective biocide and an active ingredient in antifouling paints. Screening along the Indian coast yielded 49 bacterial isolates capable of TBT assimilation. The screening was done based on the ability of bacteria to grow in mineral salt medium (MSM) containing TBT as the sole source of carbon. All the isolates produced exopolysaccharides (biosurfactants) in the medium which aid in emulsification and thus ease bioavailability of TBT. Five isolates were identified as potent TBT degraders (namely, Pseudomonas pseudoalcaligenes, Pseudomonas stutzeri, Pseudomonas mendocina, Pseudomonas putida, and Pseudomonas balearica) based on their biomass production in MSM containing TBT as the sole source of carbon. In addition to evaluating the potential of individual bacterial strains, the study also focused on using a consortium of bacteria to explore their synergistic effect when grown on TBT. Further tests like growth profile, rhamnolipid secretion profile, extracellular protein secretion profile, and detection of siderophores were performed on these isolates when grown in MSM supplemented with 2 mM TBT concentration. Emulsification activity of the crude extracellular polysaccharides against kerosene was evaluated. It can be therefore inferred that TBT degradation by these marine pseudomonads is a two-step process: (a) dispersion of TBT in the aqueous phase and (b) tin–carbon bond cleavage by siderophores affecting debutylation of TBT. The consortium of bacteria may be effective in the treatment of TBT-contaminated waste water in dry docks.

Distribution of Different Organotin and Organolead Compounds in Sediment of Suez Gulf

Organotin and organolead compounds were determined in sediments of the Suez Gulf The concentrations of Tributyltin (TBT) ranged from 0.27 to 2.77 with an average value of 1.37 µgg-1; dry wt. However, the concentrations of dibutyltin (DBT) ranged from 0.07 to 2.27 with an average value of 0.58 µgg-1; dry wt. A significant correlation was found between TBT and DBT with r = 0.82, (p = 0.05) indicating that the occurrence of DBT is mainly related to the degradation of TBT. Generally, the high concentration of TBT was attributed to shipping activity in harbours. In addition, Diphenyltin (DPhT) concentrations ranged from not detected to 2.09 with an average of 1.10 µgg-1 dry wt. Antifouling agents, industrial discharge and the influence of sewage discharge are the main sources of pollution by DPhT compounds in Suez Gulf. On the other side, organolead (OLC) concentrations ranged from 10.88 - 440.2 with an average of 168.7 ngg-1; dry wt. A significant setting of OLC recorded in sediments of Suez Gulf was mainly attributed to cars exhaust and/or spelling and direct evaporation of fuels.

Effects of organic nutrients and growth factors on biostimulation of tributyltin removal by sediment microorganisms and Enterobacter cloacae

Natural attenuation can reduce contamination of tributyltin (TBT), but persistence of the xenobiotic can cause long-term issues in the environment. Biostimulation is used to accelerate biodegradation. This study investigated the ability of individual organic nutrients and growth factors to enhance TBT biodegradation by sediment microorganisms (SED) and Enterobacter cloacae strain TISTR1971 (B3). The supplements that produced high biomass yield were selected for degradation enhancement. For TBT degradation at initial concentration of 0.1 mg/l, negative or limited degradation was observed in some selected supplements indicating that increasing the biomass did not necessarily promote degradation. Consequently, the addition of nutrients was expected to increase both dioxygenase activity and the degrader population. At different concentrations of supplements, a mixture of succinate/glycerol showed the highest removal for SED which reduced TBT by 77%, 75%, and 68% for 0.1×, 1×, and 10× supplement concentration, respectively. For B3, the addition of succinate showed degradation of 49% (0.1×), 75% (1×), and 77% (10×). Most nutrients and amino acids had an inhibitory effect at 1× or 10× levels. Excess amount of the nutrients added can inhibit the initial degradation of TBT. Therefore, TBT biostimulation requires supplements that increase the capability of TBT degraders at an appropriate amount.

Tributyltin Solubilization and Degradation from Spiked Kaolin Using Different Reagents

Conditions for tributyltin (TBT) solubilization and degradation were investigated. These conditions were optimized to remove or degrade organotin compounds (OTC) in spiked kaolin. TBT-spiked kaolin and reagents with specific chemical properties were tested in a batch reactor using a solid matrix model. The final concentrations of butyltin compounds in kaolin were determined by gas chromatography coupled with a pulsed flame photometric detector. Best results were obtained under acidic conditions (2 < pH < 5) with up to 87% TBT removal from the spiked kaolin. Acids with reducing properties were more effective (ascorbic and formic acid: 87% and 82% of TBT abatement, respectively). Moreover, final monobutyltin and dibutyltin concentrations were analyzed to determine which species predominate in the solid matrix after batch experiments. OTC speciation shows that degradation of TBT occurs simultaneously with solubilization in the presence of several reagents. These results allow choosing favorable/optimal operating conditions for OTC elimination.

Effect of nutrients on the biodegradation of tributyltin (TBT) by alginate immobilized microalga, Chlorella vulgaris, in natural river water

The removal and degradation of tributyltin (TBT) by alginate immobilized Chlorella vulgaris has been evidenced in our previously published work. The present study was further to investigate the effect of spiked nutrient concentrations on the TBT removal capacity and degradation in the same alginate immobilized C. vulgaris. During the 14-d experiment, compared to the control (natural river water), the spiked nutrient groups (50% or 100% nutrients of the commercial Bristol medium as the reference, marked as 1/2N or 1N) showed more rapid cell proliferation of microalgae and higher TBT removal rate. Moreover, significantly more TBT was adsorbed onto the alginate matrix, but less TBT was taken up by the algal cells of the nutrient groups than that of the control. Mass balance data showed that TBT was lost as inorganic tin in the highest degree in 1N group, followed by 1/2N group and the least was in the control, but the relative abundance of the intermediate products of debutylation (dibutyltin and monobutyltin) were comparable among three groups. In conclusion, the addition of nutrients in contaminated water stimulated the growth and physiological activity of C. vulgaris immobilized in alginate beads and improved its TBT degradation efficiency.

Enhancement of tributyltin degradation under natural light by N-doped TiO2 photocatalyst

Photo-degradation of tributyltin (TBT) has been enhanced by TiO2 nanoparticles doped with nitrogen (N-doped TiO2). The N-doped catalyst was prepared by a sol–gel reaction of titanium (IV) tetraisopropoxide with 25% ammonia solution and calcined at various temperatures from 300 to 600°C. X-ray diffraction results showed that N-doped TiO2 remained amorphous at 300°C. At 400°C the anatase phase occurred then transformed to the rutile phase at 600°C. The crystallite size calculated from Scherrer's equation was in the range of 16–51nm which depended on the calcination temperature. N-doped TiO2 calcined at 400°C which contained 0.054% nitrogen, demonstrated the highest photocatalytic degradation of TBT at 28% in 3h under natural light when compared with undoped TiO2 and commercial photocatalyst, P25–TiO2 which gave 14.8 and 18% conversion, respectively.

Baseline of butyltin pollution in coastal sediments within the Basque Country (northern Spain), in 2007–2008

Tributyltin (TBT), dibutyltin (DBT) and monobutyltin (MBT) were measured in surficial sediments at, the ports of Pasaia and Bilbao, together with other mid- and small-size harbours of the Basque Country (northern Spain), in 2007–2008. The highest values of the sum of the three measured butyltin species (3523–3640ngg−1, as Sn) were found at sampling stations near to shipyards located within the port of Pasaia. The highest value of TBT concentration (3143ngg−1, as Sn) was found at the marina of Getxo, in the port of Bilbao. The degree of TBT degradation varied greatly between sampling stations, being found to be generally higher in those sediments with higher values of redox potential and lower values of TBT concentration (normalized by organic matter content).

Butyltin contamination in sediments and seawater from Kaohsiung Harbor, Taiwan

The distribution of butyltin (BT) compounds in the sediments and seawater, at the river outfalls, fishing ports, shipyards, and industrial zone docks of Kaohsiung Harbor, Taiwan were investigated. Twenty sediment and seawater samples were collected from various locations in the Harbor in 2006 and analyzed for monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT). Results showed that the concentration of total BTs varied from 1.5 to 151 ng/g in sediment samples, with TBT being the major component of the sediment samples. This suggests that sediments could be the most possible sink of TBT brought by the sorption mechanism. The concentrations of BTs ranged from 9.7 to 270 ng/L in seawater samples, whereas DBT and MBT, the degradation byproducts of TBT, were mainly the most abundant BT compounds of the seawater samples. This indicates that the abiotic or biotic degradation potential of TBT was significant. Spatially, the highest concentrations of BTs were observed in both water and sediment samples collected from the shipyard and fishing port areas. This indicates that the shipping-related activities (e.g., navigation, ship repair, and ship building) would contribute most of BTs in the environment. Results show that the concentrations of degradation products (DBT and MBT) were related closely to temperature, salinity, dissolved oxygen (DO), and chlorophyll-a of the seawater. This implies that seasonal changes of the water parameters controlled the degradation of TBT in seawater. The observed levels of BT compounds in both seawater and sediments were much higher than those required to induce toxic effects on marine organisms, suggesting that appropriate TBT control strategies should be taken in Kaohsiung Harbor.

Distribution of butyltins (TBT, DBT, MBT) in sediments of Gulf of Cádiz (Spain) and its bioaccumulation in the clam Ruditapes philippinarum

Surface sediment samples were analyzed for organotins namely tributyltin (TBT), dibutyltin and monobutyltin from six areas located in the Gulf of Cádiz (14 stations), Spain. The total butyltin ranged between undetected and 1,580 ng Sn g(-1). TBT generally prevailed in most of the samples, suggesting fresh inputs of butyltin compounds and/or less degradation of TBT. The observed levels of butyltins at several sites are much higher than that required to induce toxic effect on marine organisms, suggesting that these sediments are polluted with butyltin compounds. The clam Ruditapes philippinarum was used for studying bioaccumulation of butyltins by exposing them to contaminated sediments from the Gulf of Cádiz over a period of 28 days under laboratory conditions. Biota-sediment accumulation factor (BSAF) ranged from 0.44 to 3.99.

The stability of butyltin compounds in a dredged heavily-contaminated sediment

A treatment process for marine sediment heavily contaminated with tributyltin (TBT) was designed that included dehydrating, sunlight drying and dumping processes. The time course in butyltin (BTs) compounds, TBT, dibutyltin (DBT) and monobutyltin concentrations were investigated in the sediment treated under various conditions (light (UV, sunlight and light exclusion), moisture (air-drying and water saturation) and wetting and drying cycles). Significant changes in all the BT compound concentrations with time were not found regardless of the sediment conditions for light and moisture. The results indicated the high stabilities of TBT and DBT in the sediments versus light and moisture condition changes, probably taking place in the treatment process. It is also estimated that the BTs in the sediment are resistant to photo-degradation and biochemical degradation and their half lives are relatively long. In contrast, the decreases in the TBT and DBT were observed during the wetting and drying cycle treatment for the water saturated sediment both during exposure to sunlight and under a dark condition. This result suggested the hypothesis that the TBT degradation could be accelerated by the high microbial activity induced by the moisture changing treatments.

Accumulation of Organotin Compounds in Tissues and Organs of Stranded Whales Along the Coasts of Thailand

Concentrations of butyltin (BT) and phenyltin (PT) compounds were measured in organs and tissues of five species of whales (Bride's whale [Balaenoptera edeni], false killer whale [Pseudorca crassidens], pygmy sperm whale [Kogia breviceps], short-finned pilot whale [Globicephala macrorhynchus], and sperm whale [Physeter macrocephalus]) found stranded on the coasts of Thailand. The mean concentrations of BTs in various whales were in the range of 0.157 to 1.03 mg kg(-1 )wet weight, which were higher levels than the reported concentrations in whales from other countries. PT concentrations were also detected in the range of 0.022 to 1.14 mg kg(-1) wet weight. The concentrations of BTs and PTs in whales were higher than those in mussels from the coastal area of Thailand. Concentrations of tributyltin (TBT) and triphenyltin (TPT) compounds in whale organs and tissues were also compared, and it was found that TBT concentrations were generally higher in liver and lower in lung. TPT concentrations were higher in liver and blubber and lower in lung. Ratios of TBT degradation products in whale liver, namely monobutyltin (MBT) and dibutyltin (DBT), were higher than the ratios of TBT. TPTs in liver were found to be dominant among PTs. The patterns of BTs and PTs in false killer whale liver were different from those in the other whales by cluster analysis. Their concentrations in false killer whales were the highest among all whales in this study. False killer whales feed on squid and large pelagic fish containing higher concentrations of organotin (OT) compounds, so the differences in patterns and concentrations of OTs in liver between false killer whales and the other whales may be caused by difference in diet.