Organotin compounds in precipitation, fog and soils of a forested ecosystem in Germany

Effect of prothioconazole on the degradation of microplastics derived from mulching plastic film: Apparent change and interaction with heavy metals in soil

Microplastic pollution is a major global environmental problem in both aquatic and terrestrial environments. Pesticides are frequently applied to agricultural soil to reduce the effects of pests on crops, but may also affect the degradation of plastics. In this study, we generated microplastics from polyethylene (PE) film and biodegradable poly(butylene adipate-co-terephthalate) (PBAT) film and determined (1) the effect of prothioconazole on degradation of the microplastics, and (2) the adsorption and release characteristics of heavy metals (Cr, Cu, As, Pb, Ba, and Sn) by the microplastics during degradation process. Changes of surface functional groups and morphologies were measured by FTIR and SEM, while metal concentrations were determined by ICPMS. Prothioconazole was found to promote plastic degradation. PBAT degraded faster and adsorbed more heavy metals from the soil than PE. Whether the microplastics adsorb or release heavy metals depended on the metal and their concentrations. Prothioconazole inhibited the adsorption of Cr, As, Pb and Ba by microplastics, promoted the adsorption of Cu, and had no significant effect for Sn. These results can help to assess the ecological risk of microplastic pollution from plastic mulch when combined with heavy metals.

An optimised sequential extraction scheme for the evaluation of vanadium mobility in soils

Reviewing the current state of knowledge about sequential extraction applied for soil vanadium (V) fractionation, we identified an urgent requirement of an sequential extraction (SE) specified for V. Namely, almost all previous SE extracted only 8.4%-48% of total V in soils (excluding residue). Thus, we proposed an eight-step SE for V fractionation in soils according to the knowledge gained from literature and our own dissolution experiments with model minerals. After extracting the mobilisable and adsorbed V with de-ionised water and 5mmol/L phosphate, 1mol/L pyrophosphate was applied to gather organic matter bound V which minimised the artefact dissolving Al and Fe (hydr)oxides occurred when using HNO₃-H₂O₂ for extraction. Extraction with 0.4mol/L NH₂OH⋅HCl was highly selective toward manganese oxides. Fractionation of different crystalline Al and Fe (hydr)oxides associated V with 1mol/L HCl, 0.2mol/L oxalate buffer and 4mol/L HCl at 95°C especially improved the extractability of V incorporated with crystalline phase associated V. The suitability of our new SE scheme was confirmed by its higher selectivity against the target phases and higher extraction efficiencies (55%-77% of total V) with model minerals and 6 soils of different properties than previous SE.

Assessment of background concentrations of organometallic compounds (methylmercury, ethyllead and butyl- and phenyltin) in French aquatic environments

The aim of this work is to estimate background concentrations of organometallic compounds, such as tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPhT), diphenyltin (DPhT), monophenyltin (MPhT), methylmercury (MeHg), inorganic mercury (iHg) and diethyllead (Et2Pb) in the aquatic environment at the French national scale. Both water and sediment samples were collected all over the country, resulting in 152 water samples and 123 sediment samples collected at 181 sampling points. Three types of surface water bodies were investigated: rivers (140 sites), lakes (19 sites) and coastal water (42 sites), spread along the 11 French river basins. The choice of sites was made on the basis of previous investigation results and the following target criteria: reference, urban sites, agricultural and industrial areas. The analytical method was properly validated for both matrices prior to analysis, resulting in low limits of quantification (LOQ), good precision and linearity in agreement with the Water Framework Directive demands. The results were first evaluated as a function of their river basins, type of surrounding pressure and water bodies. Later, background concentrations at the French national scale were established for both water and sediment matrices, as well as their threshold, i.e., the concentration that distinguishes background from anomalies or contaminations. Background concentrations in water are ranging between <0.04-0.14 ng Hg. L(-1) for MeHg, <0.14-2.10 ng Hg. L(-1) for iHg, <1.0-8.43 ng Pb. L(-1) for Et2Pb and 0.49-151 ng Sn. L(-1), <0.08-3.04 ng Sn. L(-1) and <0.08-0.25 ng Sn. L(-1) for MBT, DBT and TBT, respectively. For sediments, background concentrations were set as <0.09-1.11 ng Hg. g(-1) for MeHg, <0.06-24.3 ng Pb. g(-1) for Et2Pb and <1.4-13.4 ng Sn. g(-1), <0.82-8.54 ng Sn. g(-1), <0.25-1.16 ng Sn. g(-1) and <0.08-0.61 ng Sn. g(-1) for MBT, DBT, TBT and DPhT, respectively. TBT occurs in higher concentrations than the available environmental protection values in 24 and 38 sampling sites for both water and sediment samples, respectively. Other phenyltins (MPhT and TPhT) did not occur above their LOQ and therefore no background was possible to establish. Throughout this work, which is the first assessment of background concentrations for organometallic compounds at the French national level ever being published, it was possible to conclude that over the last 10-20 years organotin concentrations in French river basins have decreased while MeHg concentration remained stable.

Toxicity of tributyltin (TBT) to terrestrial organisms and its species sensitivity distribution

The contamination of the terrestrial environment by disposal of tributyltin (TBT) by contaminated harbour sediments, sewage sludge and/or biocide products has been raising concerns and it may pose a risk to soil invertebrates and plants. This study aimed to improve the amount and quality of data for TBT toxicity in soils in order to assess the ecological risk of TBT to the terrestrial ecosystems. For this, bioassays were performed with the species Porcellionides pruinosus, Folsomia candida, Brassica rapa and Triticum aestivum to evaluate the toxic effects of TBT (as chloride) on these species. Additionally, this study contributed to increase the amount of data concerning TBT toxicity on soil dwelling organisms. The results showed a dose-response relationship between TBT concentration and the increase of toxicity in all species tested. These results were collated with results from literature to construct species sensitivity distributions (SSDs) and to calculate the hazardous concentration at 5% (HC₅) for all data, for each type of soil and TBT formulation used. The HC₅ value for TBT in soil was 2.06 mg TBT/kg soil dw. Little information is available concerning the concentrations of TBT in soils. In addition the predicted no-effect concentration (PNEC) value was determined to be 30 μg/kg soil. Only one study was found referring to TBT contaminated soils, and where TBT concentrations were lower than 0.024 μg TBT/kg for the wetland soil. Therefore it can be concluded that the real TBT concentrations determined represent low risk for environmental effects. In conclusion, the construction of SSDs and the calculation of HC5 using all the data available showed to be a more suitable method rather than the construction of several SSDs for each soil and TBT types. Further investigations concerning TBT concentrations and toxicity on soil organisms need to be performed to increase data and improve risk calculations.

Evolution of chemical composition of fogwater in winter in Chengdu, China

Two sampling sites representing the urban and suburban area of Chengdu, China were sampled and analyzed for selected chemicals to characterize the evolution of the chemical composition of fogwater. A trend of total organic carbon (TOC) > total nitrogen (TN) > total inorganic carbon (TIC) was observed for both sites. Variation of inorganic ions indicated that inorganic pollutants were not accumulated in the fog. Concentrations of n-alkanes (C11-C37) at the urban site ranged from 7.58 to 27.75 ng/mL while at the suburban site concentrations were 2.57-21.55 ng/mL. The highest concentration of n-alkanes was observed in the mature period of fog (393.12 ng/mL) which was more than ten times that in the fog formation period (27.83 ng/mL) and the fog dissipation period (14.87 ng/mL). Concentrations of Sigma15PAHs were in the range of 7.27-38.52 ng/mL at the urban site and 2.59-22.69 ng/mL at the suburban site. Contents of PAHs in the mature period of fog (27.15 ng/mL) > fog dissipation period (11.59 ng/mL) > fog formation period (6.42 ng/mL). Concentrations of dicarboxylic acids (C5-C9) ranged from 10.92 to 40.78 ng/mL, with glutaric acid (C5) as the dominant dicarboxylic acid. These data provide strong indications of the accumulation of certain organic chemicals of environmental concern in fog and fog water, and provide additional insights about processes in urban and suburban air acting on organic chemicals with similar physical chemical properties.

Volatilization of organotin species from municipal waste deposits: novel species identification and modeling of atmospheric stability

Organotin compounds are used as pesticides and fungicides as well as additives in plastics. This study identifies the de novo generation of novel volatile organotins in municipal waste deposits and their release via landfill gas. Besides tetramethyltin (Me(4)Sn), a strong neurotoxin, and 5 previously reported organotins, 13 novel ethylated, propylated, and butylated tetraalkyltin compounds were identified. A concentration of 2-4 μg of Sn m(-3) landfill gas was estimated for two landfill sites in Scotland. The atmospheric stability of Me(4)Sn and methylated tin hydrides was determined empirically in a static atmosphere in the dark and under UV light to simulate night- and daytime conditions. Theoretical calculations were carried out to help predict the experimentally obtained stabilities and to estimate the relative stabilities of other alkylated species. Assuming first-order kinetics, the atmospheric half-life for Me(3)SnH was found to be 33 ± 16 and 1311 ± 111 h during day- and nighttime conditions, respectively. Polyalkylation and larger alkyl substitutes tend to reduce the atmospheric stability. These results show that substantial concentrations of neurotoxic organotin compounds can be released from landfill sites and are sufficiently stable in the atmosphere to travel over large distances in night- and daytime conditions to populated areas.

Isolation of Streptomyces sp. strain capable of butyltin compounds degradation with high efficiency

Dibutyltin (DBT), a widely used plastic stabilizer, has been detected in the environment as well as in human tissues. DBT is considered to be highly neurotoxic and immunotoxic. Hence, DBT needs to be considered as a potential toxic chemical. Degradation of butyltin compounds by Streptomyces sp. isolated from plant waste composting heaps was studied. Glucose grown cells degraded organotin from 10 to 40 mg l(-1). After 1 day of incubation 90% of DBT (added at 20 mg l(-1)) was converted to less toxic derivative--monobutyltin (MBT). DBT metabolism was inhibited by metyrapone addition, a known cytochrome P-450 inhibitor. It could provide evidence that cytochrome P-450 system is involved in DBT metabolism in Streptomyces sp. IM P102. Moreover, according to our knowledge, the degradation of DBT by actinobacterium has not been previously described.

Tributyltin and triphenyltin uptake by lettuce

This paper provides quantitative information on the transfer of TBT (tributyltin) and TPhT (triphenyltin) from sludged soil to cultivated lettuce. The effect of their initial concentrations in the soil (varying from 20 to 50 microg(Sn)kg(-1) for each triorganotin), sludge amount (between 1% and 9%), and cultivation duration (32-54 days) was evaluated by means of experimental designs. The impact of the cultivation temperature at 13 degrees C and 19 degrees C on organotin fate in the soil/plant system was also considered. The final concentration of a given organotin in the plant roots was found to depend directly on its initial concentration in the soil. A total of (85+/-15)% of initial TBT in the soil was still present at the end of the experiments, regardless of the cultivation duration. Consequently, TBT appeared to be taken up by lettuce continually. A total of (75+/-5)% of TPhT was found to be degraded in the soil at 54 days. So, this compound could have been taken up by the plant at the beginning of the cultivation. Sludge amount seemed to have a negative effect on TPhT concentration in a plant at 32 days. This could be due to the quantitative TPhT sorption onto the sludge, observed just after spiking. Organotin plant uptake appeared to be more important at 19 degrees C than at 13 degrees C. TBT and TPhT were mainly accumulated in the roots, and up to 2% and 10% of TPhT and TBT, respectively, were translocated to the shoots. Despite TPhT degradation, products in large amounts were present in the soil and were not significantly taken up by the plant. They possibly remained immobilized on solid phases of the sludged soil.

Kinetic degradation processes of butyl- and phenyltins in soils

The degradation of organotin compounds (OTC) in agricultural and forest soils is studied in sandy soil samples. Individual experiments involving the three butyl- and the three phenyltins were carried out during 90 d in controlled conditions (darkness, 28 degrees C, aerobic conditions, 13% moisture) and with spiking concentration representative of environmental levels (20-50 micrg(Sn) kg(-1)). After the validation of first-order degradation kinetic model, mechanisms involved throughout the study were considered. Degradation pathways are proposed for butyl- and phenyltins and discussed according to literature data. The degradation of mono- (MBT, MPhT), di-organotins (DBT, DPhT) and TBT is clearly identified as a single successive loss of an organic group whereas TPhT is directly degraded to MPhT. The half-life times were dependent on their substitution degree, ranging from 24 (TPhT) to 220 (MBT) d. The less substituted the OTC is, the more persistent it is. In the range 4.3-5.7, pH does not seem to influence OTC degradation under the present operating conditions. Finally this study shows the significant persistence in soil samples in our experimental conditions for most of studied organotins and highlights the potential impact on soil quality.

Organometals of tin, lead and mercury compounds in landfill gases and leachates from Bavaria, Germany

Organo-Sn, -Pb and -Hg compounds were monitored in gases and leachates of 11 municipal waste landfills and one hazardous waste landfill from Bavaria, Germany, with the objectives to estimate the methylation of Sn, Pb and Hg and to assess the risk of their release into the adjacent environment. In the gases, tetramethyl Sn predominated (>80% of total gaseous Sn) with concentrations up to 160 microg Sn m(-3). Dimethyl-Hg and tetramethyl-Pb were only occasionally detected with concentrations up to 2.9 and 2.1 microg m(-3) as Hg or Pb, respectively. In all leachates, trimethyl-Sn dominated with a maximum concentration of 2100 ng Sn L(-1). No organo-Pb compounds were found, and monomethyl-Hg was detected in only one leachate. The concentrations of trimethyl-Sn were up to 100-fold higher in the condensate water than in leachates, and the concentrations of organo-Sn compounds were lower in the adjacent groundwater than in the corresponding leachates. The high abundance of methylated Sn species in the gases and leachates indicates Sn methylation, suggesting the landfill as a source for organo-Sn compounds. In comparison, methylation of Hg and Pb was of little importance, probably due to low Hg concentrations and low rates of Pb methylation in the landfill. The risks of organo-Sn compounds release to the adjacent air is low due to flaring of landfill gases. However, there is probable release of organo-Sn compounds, especially trimethyl-Sn, to the adjacent groundwater.

Emissions of organo-metal compounds via the leachate and gas pathway from two differently pre-treated municipal waste materials -- A landfill reactor study

Due to their broad industrial production and use as PVC-stabilisers, agro-chemicals and anti-fouling agents, organo-metal compounds are widely distributed throughout the terrestrial and marine biogeosphere. Here, we focused on the emission dynamics of various organo-metal compounds (e.g., di,- tri-, tetra-methyl tin, di-methyl mercury, tetra-methyl lead) from two different kinds of pre-treated mass waste, namely mechanically-biologically pre-treated municipal solid waste (MBP MSW) and municipal waste incineration ash (MWIA). In landfill simulation reactors, the emission of the organo-metal compounds via the leachate and gas pathway was observed over a period of 5 months simulating different environmental conditions (anaerobic with underlying soil layer/aerated/anaerobic). Both waste materials differ significantly in their initial amounts of organo-metal compounds and their environmental behaviour with regard to the accumulation and depletion rates within the solid material during incubation. For tri-methyl tin, the highest release rates in leachates were found in the incineration ash treatments, where anaerobic conditions in combination with underlying soil material significantly promoted its formation. Concerning the gas pathway, anaerobic conditions considerably favour the emission of organo-metal compounds (tetra-methyl tin, di-methyl mercury, tetra-methyl lead) in both the MBP material and especially in the incineration ash.

TBT and TPhT persistence in a sludged soil

The persistence of tributyltin (TBT) and triphenyltin (TPhT) in soils was studied, taking into consideration the quantity of sewage sludge, TBT and TPhT concentrations in soil as well as the soil pH. The organotin compounds (OTC) were introduced into the soil via a spiked urban sludge, simulating agricultural practise. OTC speciation was achieved after acidic extraction of soil samples followed by gas chromatography-pulsed flame photometric analysis (GC-PFPD). Leaching tests conducted on a spiked sludge showed that more than 98% of TBT are sorbed on the sludge. TBT persistence in soil appeared to depend on its initial concentration in sludge. Thus, it was more important when concentration is over 1000 microg(Sn) kg(-1) of sludge. More than 50% of the initial TBT added into the soil were still present after 2 months, whatever the experimental conditions. The main degradation product appeared to be dibutyltin. About 90% of TPhT were initially sorbed on sludge, whatever the spiking concentration in sludge was. However, TPhT seemed to be quantitatively exchangeable at the solid/liquid interface, according to the leaching tests. It was also significantly degraded in sludged soil as only about 20% of TPhT remain present after 2 months, the monophenyltin being the main degradation product. pH had a significant positive effect on TBT and particularly TPhT persistence, according to the initial amounts introduced into the soil. Thus, at pH over 7 and triorganotin concentration over 100 microg(Sn) kg(-1), less than 10% of TBT but about 60% of TPhT were degraded. When the sludge was moderately contaminated by triorganotins (typically 50 microg(Sn) kg(-1) in our conditions) the pH had no effect on TBT and TPhT persistence.

Municipal landfills exhale newly formed organotins

For the first time we are able to report the identification and quantification of several unexpected alkylated tin compounds such as dimethyldiethyltin, trimethylethyltin and propyltrimethyltin in European municipal waste deposits, by using GC-ICP-MS. Future studies will reveal whether their origin is from the degradation of butyl-, or octyltin compounds or simply products of de novo synthesis within the landfill environment.

Methylated arsenic, antimony and tin species in soils

Methylated species of antimony, arsenic and tin were examined in urban soils of the Ruhr basin, near the cities of Duisburg and Essen, Germany. The main aim of this study was to investigate the occurrence of mono-, di- and trimethylated species of these elements in urban soils. The influence of historical and present land use upon the species content was examined. The distribution of inorganic As, Sb and Sn and their methylated species along the profile depth was investigated. As, Sb and Sn speciation was performed by pH-gradient hydride generation purge and trap gas chromatography, followed by inductively-coupled plasma mass spectrometry (HG-PT-GC/ICP-MS). Species' structures were confirmed by GC-EI/MS-ICP-MS. Monomethylated Sb and As were the dominant species detected: the concentration of these metal(loid) species varied between <0.07-56 microg kg(-1) per dry mass. All dimethylated species and monomethyltin concentrations were between <0.01-7.6 microg kg(-1) per dry mass, and for the trimethylated species of all examined elements, concentrations between <0.001-0.63 microg kg(-1) per dry mass were detected. The highest organometal(loid) concentrations were observed in agricultural soils and garden soils; lower concentrations were found in the soils of abandoned industrial sites (wasteland, primary forest and grassland) and a flood plain soil of the Rhine. This result can be ascribed to both the cultivation and the increased biological activity of the agricultural soils, and the generally higher contamination, the disturbed structure and the artificial substrates (deposits from industrial sources) of the abandoned industrial soils. Due to periodical sedimentation, the flood plain profile was the only one where no depth dependence of organometal(loid) species concentration was detected. The other soil profiles showed a decrease of species content with increasing depth; this was particularly noticeable in soils with a clear change from a horizon with an organic character towards a mineral horizon, i.e. decreasing vitality from profile top to bottom. It is not as yet clear whether the organometal(loid) species are formed in the mineral horizons of the profiles or whether they are displaced from the organic, biologically-active horizons towards the mineral horizons. Field studies revealed that soil parameters like pH, water content or temperature did not correlate significantly with the degree of biomethylation observed. In contrast to the lower in vitro biomethylation efficiency of Sb vs. As in microbial incubations, we consistently detected higher proportions of transformed Sb compounds in situ in soil samples. These data may indicate a need to re-examine the currently accepted model of Sb biogeochemical cycling in the real environment.

Biogeochemistry of organotin compounds and tin in a forested catchment in Germany

Organotin compounds (OTC) are highly toxic pollutants that have been shown to affect many aquatic ecosystems. Little is known about the input and fate of OTC in terrestrial ecosystems. Here, soil pools, concentrations and fluxes in bulk precipitation, throughfall, fog, litterfall and runoff of OTC and Sntotal were investigated in a forested ecosystem (Picea abies, Karst.) in NE Bavaria, Germany. The concentrations of OTC and Sntotal were generally in the order fog>throughfall>bulk precipitation. Average concentrations of OTCtotal ranged from 57 ng Sn l(-1) in fog to 5.8 ng Sn l(-1) in bulk precipitation. Concentrations of Sntotal were in the same order but between 490 ng Sn l(-1) in fog and 140 ng Sn l(-1) in bulk precipitation, on average. Average OTCtotal concentrations in litterfall were 12.9 ng Sn g(-1) and those of Sntotal in litterfall 38 ng Sn g(-1). All OTC concentrations in runoff were lower than in bulk precipitation, while those of Sntotal were similar to the concentrations in bulk precipitation. Monobutyltin was the dominating OTC in bulk precipitation, throughfall, fog and litterfall, but was seldom detected in the runoff. The annual total deposition of OTCtotal (calculated as throughfall + litterfall) was 172 mg Sn ha(-1) year(-1), with 45 mg Sn ha(-1) year(-1) represented by litterfall. The annual runoff from the catchment of OTCtotal amounted to 25 mg Sn ha(-1) year(-1). The total deposition of Sntotal was 4.9 g Sn ha(-1) year(-1), of which 0.2 g Sn ha(-1) year(-1) was litterfall. The annual runoff of Sntotal was 2.4 g Sn ha(-1) year(-1). The mass balance showed a high retention of OTC and Sntotal in the catchment. The forest soils act as a strong sink for OTC and Sntotal. Only small amounts of deposited OTC are released to runoff. The ratio of soil pools to annual accumulation for total OTC (46 years) indicates that OTC inputs have been occurring already for many decades or have been substantially higher in the past than today.