Uptake of Tributyltin into Willow Trees

BACKGROUND: Organotins have been used world-wide as antifoulants in ship paints. Repeatedly, severe effects on aquatic species have resulted. The use of organotins for this purpose was ruled out, and dumping of contaminated harbor sludge into the sea was prohibited. Land-based dumping is seen as an alternative. OBJECTIVE: This study investigates sorption, uptake and translocation of tributyltin (TBT) to willow trees in order to evaluate phytoremediation as treatment option. The study considers the influence of pH on the plant uptake of organotins. EXPERIMENTAL SET-UP: Chemicals investigated were the weak base tributyltin chloride (TBTCl) and the neutral tributyltin hydride (TBTH). Organotins were extracted from solution and plant material with toluene, and analyzed as tin by AAS with graphite oven. The pH in solution varied from pH 4 to pH 7. The sorption to living and dead roots, stems and leaves was measured in shaking experiments. The uptake into intact trees was measured at nominal levels of 1 and 10 mg TBT/l for TBTH and TBTCl at low and high pH. RESULTS: The sorption to roots and leaves dropped for dead tissue, but did not vary much with pH. The sorption to stems increased for dead stems and with pH. The solubility of TBTCl in water was below 10 mg/l and lowest at pH 4. Concentrations of TBTCl and TBTH in solutions with trees dropped rapidly to low values. Highest TBT contents in trees were found in roots and lower stems. The concentrations followed the concentrations in solution. The pH had only a small effect on the plant uptake of TBTCl, and no effect on the uptake of TBTH. No effective translocation to higher stems or leaves was found. DISCUSSION: An ion trap mechanism that accumulates the weak base TBTCl in the xylem sap of plants and leads to upward translocation could not be detected. Neither TBTCl at low or high pH, nor the neutral lipophilic chemical TBTH, were translocated effectively to leaves. The TBT+ cation sorbed strongly to plant tissue. The exact mechanism for the strong sorption of the cation is unknown, but similar effects have been observed for algae, liposomes and isolated biomembranes. CONCLUSIONS: Both the uptake of the neutral TBTH and the uptake of the neutral molecule form of TBTCl into willows was as is to be expected from theory. The cation TBT+ showed an unexpected behavior which has been observed before. No ion trap occurs, and the phytoextraction of TBT is not feasible. OUTLOOK: Planting trees, or other appropriate vegetation, could have a beneficial remediation effect by aeration of the TBT-contaminated soil or sludge. In a follow-up paper, the toxicity of TBT to willow trees will be described.     

海洋环境中的有机锡及其对海洋生物的影响

本文综述了有机锡化占物对海洋环境的冲击及其对海洋生物的影响，介绍了有机锡化合物的分析方法，讨论了有机锡污染的预防和控制措施，并展望了有机锡研究的前景。     

Growth of Plants on TBT-contaminated Harbour Sludge and Effect on TBT Removal (10 pp)

Background Worldwide, large amounts of sediments have to be dredged annually from waterways and harbours. These sediments are sometimes polluted with a variety of toxic compounds. In some countries, including Belgium, the load with the biocide tributyltin (TBT) from ship coatings prohibits the dumping of harbour sludge into the sea. Land-based dumping is a commonly used alternative. Objective This research investigated the feasibility to use land-deposited harbour sludge for plant production. In a field trial, the growth of 38 more or less salt-tolerant plant species on low and high TBT-contaminated sediments was studied. The elimination of TBT from sludge with and without vegetation was compared. The uptake of TBT and its degradation products di- and monobutyltin (DBT and MBT) into harvest products under field conditions was determined. - Experimental Set-up. Sediments dredged in May 2003 from the brackish waters of the port of Antwerp were analysed in the laboratory for soil texture, pH, electroconductivity, sodium, magnesium, potassium, calcium, ammonium, nitrate, total nitrogen, chloride, sulphur and the organotins TBT, DBT and MBT. The sediments were lagooned for one year to dewater, desalinate and improve their structure. Salt-tolerant domestic and wild plants were selected and sown in May 2004. In August 2004, plants were harvested and the produced biomass was determined. Samples were taken from vegetated and non-vegetated top and bottom sediments and from plants growing above soil and analysed for TBT, DBT and MBT. Results The fresh sediments showed a good supply with nutrients and a neutral pH, but were rather saline (EC 14 mS cm-1 of the saturated paste extract). The salinity decreased to 3.7 mS cm-1 during lagoonation. The high and the low contaminated sediment had initially 43 and 1.6 mg TBT kg-1 dry weight, respectively. Besides TBT, several other contaminants were present in the sediments at critical levels. The biomass production of the plant species from the field trial ranged from 0.2 to 13 tons dry mass per hectare. Plants performing excellently were barley, sorghum, rape seed, a clover/grass mix and reed. If at all, a positive influence of TBT on plant growth was seen. TBT was degraded significantly faster (>40%) below barley. The uptake of TBT, DBT and MBT into stem and leaves of reed, grass and clover was very low, but measurable and not related to concentrations in soil. No uptake of TBT or its metabolites into corn of barley was found. Discussion This study confirmed former results: the toxicity of TBT to higher plants is low, and even high levels in soils would not be a hindrance for crop production. The removal of TBT seemed to be increased by both lagooning and plant growth, although the target values for sea dumping in use in certain European countries were not reached. A plausible explanation for the faster degradation of TBT under vegetation is that oxygen is a limiting factor, and plants dewater the soil, thus aerating it. The uptake of the organotins TBT, DBT and MBT into harvest products is probably due to attached soil particles. Conclusions To summarize, barley was the optimal species: it grew very well despite the salinity of the dredged sediments, it had a significantly positive effect on TBT removal; it showed no measurable uptake of TBT or the other butyltins into the harvested product; and it is a cash crop well established in European agriculture. Outlook The amounts of dredged sediments are high, and good soils are becoming increasingly rare. The feasibility of using dredged sediments for non-food production, such as energy crops, should be investigated by a critical risk assessment.     

Assessment of Antifouling Effectiveness of two Natural Product Antifoulants by Attachment Study with Freshwater Bacteria (7 pp)

- Goal, Scope, Background. The traditional solution for keeping unwanted organisms from attaching to submerged surfaces is to apply anti-fouling coatings. The most common antifoulant was tributyltin (TBT). TBT systems were highly effective but were also toxic to non-target organisms. The use of the TBT based coatings will be completely banned by January 1, 2008. Therefore, there is an urgent need to seek out suitable non-toxic alternatives. Methods The aim of this work was to evaluate the effectiveness of capsaicin and zosteric acid as natural product antifoulants (NPAs) in deterring bacterial attachment. Two fresh water bacteria systems Pseudomonas putida (Pp) and bacteria isolated from Lake Erie (LE) were used to assess the attachment when the NPAs dispersed in the water. Effectiveness was ascertained based on the decrease in microbial attachment, limited toxicity, and minimum alteration of the coatings properties. Results and Discussion A significant inhibition of bacteria attachment was achieved when aqueous capsaicin concentration was increased from 0 to 40 mg/L. For instance, after 14 days the LE system depicted 93.5% and 98.5% less biofilm coverage for 20 mg/L and 40 mg/L capsaicin, respectively when compared to systems without NPA. Biofilm coverage was reduced by 92.5% and 98.2%, respectively with 50 mg/L and 500 mg/L zosteric acid. Conclusions Both capsaicin and zosteric acid was effective at preventing bacteria attachment. As the NPA aqueous concentration increased, biofilm formation decreased. Evaluating changes in aqueous pH, conductivity, dissolved oxygen, aqueous microbial population and biofilm formation suggested that the primary antifoulant mechanism of these two NPAs was to block the bacteria's active sites versus posing a lethal level. Recommendation and Perspective From the attachment study, zosteric acid appeared to be more effective in preventing bacterial attachment when the NPAs were dispersed in the aqueous environment. For practical applications, the antifoulant needs to be incorporated into a coating and have a slow release rate. Thus the ability to successfully incorporate zosteric acid into a coating, without deterring bacterial attachment, needs to be investigated.     

Phytotoxicity of Cyanide to Weeping Willow Trees

Background Cyanide is found predominantly in industrial effluents generated by metallurgical operations. It is an extremely toxic compound, so that problems and catastrophic accidents have recently occurred all around the globe. The goal of this study was to determine the toxicity of cyanide to a Chinese willow species, and to determine the removal capacity. Methods The toxicity of potassium cyanide (KCN) to weeping willow trees (Salix babylonica L.) was tested. The normalized, relative transpiration of the plants was used to determine the phytotoxicity of cyanide. The cyanide removal capacity of weeping willows was also determined. Results and Discussion In hydroponic solution, no chlorosis of leaves and only a small reduction in normalized relative transpiration was observed when weeping willows were exposed to low doses of cyanide (0.93 mg CN/L). Severe signs of toxicity were found for the treatment groups exposed to higher doses of cyanide (9.3 mg CN/L). Weeping willows grown in sandy soils survived the entire period (216 hours) without any toxic effect when irrigated with low doses of cyanide (3.72 mg CN/L). High doses of cyanide (18.6 mg CN/L) in irrigation water were fatal for the weeping willows within 216 hours. EC50 values for a 50% inhibition of the transpiration of the trees were estimated to be between 3.27 and 8.23 mg CN/L, depending on the duration of the exposure. Conclusions The results obtained for the Chinese willow species Salix babylonica were very similar to those obtained for the European species S. viminalis in earlier studies. Phytotoxic effects were only found at high doses of cyanide. A large proportion of applied cyanide was removed from the contaminated media in the presence of weeping willows. This gives rise to the conclusion that the metabolism of cyanide by weeping willows is possible. Recommendations and Outlook Cyanide elimination with trees seems to be a feasible option for cleaning soils and water contaminated with cyanide. A full-scale treatment has been installed in Denmark. For phytoremediation projects in China, weeping willow could be a suitable species. The tree can tolerate and remove cyanide, and it is a native Chinese species. Besides, the tree is of outstanding beauty and is planted as a common park tree in many parts of the world.     

Butyltin compounds in sediment and fish from the Polish Coast of the Baltic Sea

Concentrations of mono- (MBT), di- (DBT), and tri-(TBT) butyltin compounds were measured in eggs, liver, and muscle of nine species of fish from four regions of the Baltic Sea - the Firth of Vistula, the Gulf of Gdańsk, Puck Bay, and the mouth of the Vistula River. The overall concentration ranges among all the fish sampled from the four sites were: < 7 to 79 ng/g for MBT, 6 to 1100 ng/g for DBT, 7 to 3600 ng/g for TBT, and 16 to 4800 ng/g for total BTs, on a wet wt basis. The highest concentration of total BTs was found in herring liver from the Firth of Vistula (4800 ng/g, wet wt) and in roach muscle from Puck Bay (3300 ng/g, wet wt), while the least concentration was found in burbot eggs and liver from the Vistula River (39 and 32 ng/g, wet wt, respectively). TBT was the major form of BTs present in most samples analyzed. Sediment samples collected from shipyards in the Gulf of Gdańsk contained butyltin concentrations ranging from 1.2 to 46 μg/g (dry wt) for MBT, 2.0 to 42 μg/g for DBT, and 2.6 to 40 μg/g for TBT. As with the fish, the majority of the BTs in sediment were present as TBT, which suggested recent exposure of the aquatic environment of the region to TBT.     

Metabolic responses of weeping willows to selenate and selenite

Goal, Scope and Background Selenium (Se) is one of the most widely distributed elements of the earth’s crust at low concentrations. The extensive use of Se-containing chemicals due to anthropogenic activities has increased the ecological risk to environmental compartments. Plants, under unfavorable environmental conditions, often increase the formation of reactive oxygen species (ROS), and consequently plant antioxidant enzymatic systems have been proposed to be important in plant stress tolerance. The goal of this study was to find out the metabolic responses of plants to Se, to provide quantitative information whether exogenous Se has a beneficial role in plants, and to investigate the potential of vegetation management of Se for potential phytoremediation. Material and Methods Pre-rooted plants of weeping willows (Salix babylonica L.) were grown hydroponically in growth chambers and treated with Na₂SeO₄ or Na₂SeO₃ at 24.0 ± 1°C for 168 h. Five different treatment concentrations were used, ranging from 0.44 to 8.72 mg Se/L for the treatments exposed to SeO₄²⁻ and from 0.50 to 10.0 mg Se/L for the treatments exposed to SeO₃²⁻, respectively. Transpiration rates, soluble protein contents and antioxidative enzyme activities of the plants were monitored to evaluate toxicity from exogenous Se exposure. At the end of the study, total Se in the hydroponic solution was analyzed by hydride generation-atomic fluorescence spectrometry (HG-AFS). Results Both chemical forms of Se at low concentrations showed growth-promoting effects on plants. A significant decrease of transpiration rates and of soluble protein contents of plants was observed at higher Se concentrations after 168 h of exposure. Measurable change of superoxide dismutases (SOD) activity in leaves was only detected under high Se treatments. Catalase (CAT) activity was significantly affected by the Se application. Slight change of peroxidase (POD) activity was measured in all treatments, whereas significant inhibition of POD activity was detected for the plants exposed to SeO₃²⁻ of 10.0 mg Se/L. Se-induced stress appeared in all treatments, thus resulting in measurable increase of glutathione peroxidase (GSH-Px) activity of the plants. Although both chemical forms of Se were taken up by weeping willows efficiently, their uptake rates were different. Discussion Of all measured parameters, POD and CAT activities in leaves were noted the most sensitive indicator for the plants exposed to SeO₄²⁻ and SeO₃²⁻, respectively. Deleterious effects on plant physiological functions due to Se application were not observed over 168 h of exposure. This is largely due to the fact that well-established antioxidant enzymatic systems in plants and higher activities of GSH-Px largely reduced the negative effects on plants; SeO₃²⁻ caused much more severe stress to plants than SeO₄²⁻ at higher Se application rates. The uptake mechanisms between the two chemical species were quite different. Conclusions Neither visible toxic symptoms nor metabolic lesions were observed at low concentrations of Se, probably due to the effective established enzymatic systems in weeping willows. All selected parameters for toxicity determination were significantly correlated to Se application, but metabolic responses of plants to SeO₄²⁻ and SeO₃²⁻ were quite different. GSH-Px in leaves was probably the principle enzyme responsible for stress reduction from Se exposure. Due to their different chemical properties, weeping willows showed a faster uptake rate for SeO₄²⁻ than for SeO₃²⁻. Recommendations Exogenous Se has a beneficial role in plants and vegetation management of Se is a potential remediation strategy in cleaning up Se-contaminated sites. Further investigation on the biochemical mechanism of Se metabolism will provide insight to the specific interactions between Se and plants on the molecular level. Perspectives Weeping willow has a sound potential for phytoremediation of Se-contaminated sediment and groundwater because the tree is not only tolerant to Se but also uptakes chemical species from the environment.     

垃圾焚烧飞灰中不同粒径的毒性特性

对广州市某垃圾焚烧发电厂的焚烧飞灰进行粒径分级毒性分析研究。主要研究了粒径在35～1 000μm范围内的飞灰的腐蚀性和短期浸出毒性,包括Cr、Cd、Mg、Pb、Mn、Fe、Cu、Zn、Ni、Co等重金属,SO24-,Cl-,NO3--N和NO2--N,同时也研究了飞灰的物质组成和矿物特性。研究结果表明,所有粒径飞灰的浸出液pH值在12.3～12.5之间,属于有腐蚀性的危险废物,重金属Mg、Pb、Zn的浸出浓度最高,分别为168.78、53.94和86.40 mg/L。飞灰浸出液和含量最高分别达到8.87g/L和1.38 g/L,同时浸出液中测出一定量的硝态氮和亚硝态氮,证明飞灰吸附了垃圾焚烧过程中产生的氮氧化物气体。另外,研究得出飞灰的基本组成元素为Ca、Si、Cl、K、Na、S、Al、Mg和Fe,而重金属则以Zn、Pb、Mn、Cu、Cr等为主。矿物相主要为含硅和钙的化合物及NaCl和KCl等氯化物。     

Toxicity of road salt to Nova Scotia amphibians

The deposition of chemical pollutants into roadside wetlands from runoff is a current environmental concern. In northern latitudes, a major pollutant in runoff water is salt (NaCl), used as de-icing agents. In this study, 26 roadside ponds were surveyed for amphibian species richness and chloride concentration. Acute toxicity tests (LC₅₀) were performed on five locally common amphibian species using a range of environmentally significant NaCl concentrations. Field surveys indicated that spotted salamanders (Ambystoma maculatum) and wood frogs (Rana sylvatica) did not occupy high chloride ponds. American toads (Bufo americanus) showed no pond preference based on chloride concentration. Acute toxicity tests showed spotted salamanders and wood frogs were most sensitive to chloride, and American toads were the least. Spring peepers (Pseudacris crucifer) and green frogs (Rana clamitans) showed intermediate sensitivities. We concluded that chloride concentrations in ponds due to application of de-icing salts, influenced community structure by excluding salt intolerant species.     

Persistence of methyl <Emphasis Type="Italic">tertiary</Emphasis> butyl ether (MTBE) against metabolism by Danish vegetation

BACKGROUND: Methyl tertiary butyl ether (MTBE) is the second most highly produced industrial chemical in the US and a frequent groundwater pollutant. At the same time, MTBE is quite persistent to biotic and abiotic decomposition. The goal of this study was to find plant species that could degrade MTBE and might be used in phytoremediation. METHODS: Excised roots and leaves (0.3 g) from more than 24 Danish plant species out of 15 families were kept in glass vessels with 25 ml spiked aqueous solution for 2 to 4 days. MTBE concentrations were 1 to 5 mg/L. Samples were taken directly from the solution with a needle and injected to a purge and trap unit. MTBE and the main metabolite, TBA, were measured by GC/FID. RESULTS AND DISCUSSION: Solutions with roots of poplar (Populus robusta) and a willow hybrid (Salix viminalis x schwerinii) produced TBA in trace amounts, probably stemming from bacteria. Significant MTBE reduction (> 10%) was not observed in any of the tests. Leaves from none of the species (trees, grasses and herbs) reduced the concentration of MTBE in the solution and no TBA, nor any other known metabolite of MTBE, was detected. CONCLUSION: It was not possible to find plants capable of efficiently degrading MTBE. This gives rise to the conclusion that plants probably cannot degrade MTBE at all, or only very slowly. RECOMMENDATIONS AND OUTLOOK: For phytoremediation projects, this has, as consequence, that the volatilization by plants (except with genetically engineered plants) is the only relevant removal process for MTBE. For risk assessment of MTBE, degradation by the plant empire is not a relevant sink process.     

苯并三唑在土壤中的吸附特性

为了解苯并三唑(BTA)在水-土系统中的迁移转化,通过批实验方法研究了BTA在华北平原土样(GSS13)中的吸附,考察了平衡时间、土壤投加量、溶液初始pH以及共存阳离子对吸附的影响。结果表明,在初始阶段,土壤对BTA的吸附速率较快,之后随着吸附点位的减少,吸附逐渐变慢;吸附过程符合准二级反应动力学方程。土壤对BTA的平衡吸附为非线性吸附,吸附等温线为Freundlich型;随着土壤投加量的增大,单位质量土壤吸附BTA的量减少,可能原因是所选土壤对BTA的吸附存在"固体浓度效应"。溶液的pH通过改变BTA的存在形式和土壤表面的带电性而影响吸附,当溶液pH在BTA的pKa2(8.6)附近时,土壤对BTA的吸附效果最好。此外,溶液中共存阳离子对土壤吸附BTA有不同的影响, Na+对吸附影响不明显,而不同浓度Ca2+对BTA的吸附有不同程度的促进作用。     

Mixture Toxicity of the Antifouling Compound Irgarol to the Marine Phytoplankton Species Dunaliella tertiolecta

This study examined the toxicity of irgarol, individually and in binary mixtures with three other pesticides (the fungicide chlorothalonil, and the herbicides atrazine and 2,4-D), to the marine phytoplankton species Dunaliella tertiolecta. Standard 96-h static algal bioassays were used to determine pesticide effects on population growth rate. Irgarol significantly inhibited D. tertiolecta growth rate at concentrations ≥ 0.27 μ g/L. Irgarol was significantly more toxic to D. tertiolecta than the other pesticides tested (irgarol 96 h EC₅₀ = 0.7 μ g/L; chlorothalonil 96 h EC₅₀ = 64 μ g/L; atrazine 96 h EC₅₀ = 69 μ g/L; 2,4-D 96 h EC₅₀ = 45,000 μ g/L). Irgarol in mixture with chlorothalonil exhibited synergistic toxicity to D. tertiolecta, with the mixture being approximately 1.5 times more toxic than the individual compounds. Irgarol and atrazine, both triazine herbicides, were additive in mixture. The toxicity threshold of 2,4-D was much greater than typical environmental levels and would not be expected to influence irgarol toxicity. Based on these interactions, overlap of certain pesticide applications in the coastal zone may increase the toxicological risk to resident phytoplankton populations.     

Toxicity of carbaryl,diquat dibromide,and fluoranthene,individually and in mixture,to larval grass shrimp,Palaemonetes pugio

This study examined the toxicity of two pesticides (carbaryl and diquat dibromide) and one polycyclic aromatic hydrocarbon (fluoranthene), both singly and in mixture, to grass shrimp larvae (Palaemonetes pugio). These three chemicals are all present in coastal environments and can easily enter estuarine ecosystems. Fluoranthene was the most toxic chemical with a 96-h LC₅₀ value of 32.45 μ g/L, followed by carbaryl (43.02 μ g/L) and diquat dibromide (1624 μ g/L). In the chemical mixture tests, the binary carbaryl/diquat dibromide mixture and the ternary carbaryl/diquat dibromide/fluoranthene mixture had additive results.     

Predicting molybdenum toxicity to higher plants: Influence of soil properties

The effect of soil properties on the toxicity of molybdenum (Mo) to four plant species was investigated. Soil organic carbon or ammonium-oxalate extractable Fe oxides were found to be the best predictors of the 50% effective dose (ED₅₀) of Mo in different soils, explaining > 65% of the variance in ED₅₀ for four species except for ryegrass (26-38%). Molybdenum concentrations in soil solution and consequently plant uptake were increased when soil pH was artificially raised because sorption of Mo to amorphous oxides is greatly reduced at high pH. The addition of sulphate significantly decreased Mo uptake by oilseed rape. For risk assessment, we suggest that Mo toxicity values for plants should be normalised using soil amorphous iron oxide concentrations.     

The critical levels and the maximum metal uptake for wheat and rice plants when applying metal oxides to soil

Abstract

Wheat is more sensitivity to CdO and ZnO compared with rice plant. The yield of wheat decreased by 30% in the presence of 30 ppm Cd, but that of rice plants by only 8%. The critical levels of meal uptake by wheat and rice plants for applying metal oxides to soil (CdO, ZnO, PbO) were determined. The highest concentration obtained for wheat grain was 141 μg/g Cd at the Cd 10,000 ppm in soil. This value is higher the value of 4.97 μg/g for unpolished rice and higher than any other we have seen in the reports for treatment with CdO. Also, as concentration of more than 1.0 μg/g Cd in wheat was obsertced at 5 ppm Cd, while similar concentrations for rice plants were observed at 30 ppm Cd in soil.     

COD、pH值和运行周期对好氧瞬时补料工艺合成聚羟基脂肪酸酯的影响

聚羟基脂肪酸酯（PHA）是一种可生物降解塑料,具有良好的应用前景。混合菌种生产PHA是目前PHA生产的研究重点。以乙酸钠为碳源用好氧瞬时补料（ADF）工艺驯化出了生产聚羟基脂肪酸酯（PHA）的混合菌种。PHA含量在加入营养液后4和10 h达到最大值。研究了营养液COD、pH值和SBR运行周期对PHA生产的影响。COD=12 000 mg·L-1和运行周期12 h均会引发污泥膨胀;COD=3 000 mg·L-1和运行周期48 h会导致污泥流失。pH=7的中性环境下PHA生产菌不具备竞争优势;pH=10时微生物细胞活性受抑制。最适条件为COD=6 000 mg·L-1,pH=8.5,运行周期=24 h,此时得到PHA含量最大值31.1%。     

pH、盐度对微生物还原硫酸盐的影响研究

采用厌氧生物处理工艺,研究了在不同盐度下pH连续降低对硫酸盐还原和有机物去除率的影响。实验结果表明,硫酸盐还原菌有很强的适应pH变化的能力,在pH值达到4以下仍有60％的硫酸盐去除率。NaCl浓度由4g／L增加到50g／L抑制了各厌氧菌的活性,导致硫酸盐和有机物去除率的下降,但硫酸盐还原菌耐受性高于产甲烷菌等其他厌氧菌,在NaCl浓度为50g／L下,硫酸盐去除率能达到50％,而有机物去除率则低于30％。qRT—PCR表明了系统菌落中SRB随着环境的变化情况与化学指标结果相一致,该反应器体系中SRB在整个厌氧菌群落中只占了很小部分。     

Influence of Phenanthrene on Cadmium Toxicity to Soil Enzymes and Microbial Growth (5 pp)

Background Many contaminated sites contain a variety of toxicants. Risk assessment and the development of soil quality criteria therefore require information on the interaction among toxicants. Interactions between heavy metals are relatively well studied, but little is known about those between heavy metals and polycyclic aromatic hydrocarbons (PAHs). Methods 0.1 mg/kg dry soil phenanthrene alone or phenanthrene plus 10 mg/kg cadmium (Cd) were added to soil to determine the influence of phenanthrene on Cd toxicity to soil enzymes (invertase, urease, dehydrogenase and phosphatase) and microorganisms (fungi, bacteria and actinomycete) in paddy soil. Results and Discussion 0.1 mg/kg phenanthrene did not reduce the number of microorganisms. However, the addition of phenanthrene to soil with Cd enhanced the Cd toxicity to soil enzymes and microorganisms. This deleterious effect was seen to mainly affect the growth of fungi and the activity of invertase, urease and dehydrogenase. The order of combined inhibition of Cd and phenanthrene was fungi>bacteria>actinomycete. Conclusion The presence of phenanthrene might enhance the toxicity of Cd to soil microorganisms. Phenanthrene can easily be used by the soil actinomycetes as a source of carbon and energy and the finding may be supportive to the development of bioremediation techniques.     

Application of encapsulation (pH-sensitive polymer and phosphate buffer macrocapsules): a novel approach to remediation of acidic ground water

Macrocapsules, composed of a pH-sensitive polymer and phosphate buffer, offer a novel remediation alternative for acidic ground waters. To test their potential effectiveness, laboratory experiments were carried out followed by a field trial within a coal pile runoff (CPR) acidic contaminant plume. Results of traditional limestone and macrocapsule treatments were compared in both laboratory and field experiments. Macrocapsules were more effective than limestone as a passive treatment for raising pH in well water from 2.5 to 6 in both laboratory and field experiments. The limestone treatments had limited impact on pH, only increasing pH as high as 3.3, and armoring by iron was evident in the field trial. Aluminum, iron and sulfate concentrations remained relatively constant throughout the experiments, but phosphate increased (0.15-32 mg/L), indicating macrocapsule release. This research confirmed that macrocapsules may be an effective alternative to limestone to treat highly acidic ground water.     

Toxicity of synthetic pyrethroid insecticides to the grass shrimp,Palaemonetes pugio,parasitized with the bopyrid isopod,Probopyrus pandalicola

The grass shrimp, Palaemonetes pugio, plays a large role in the marine ecosystem, serving as a vital link in the food web between many other species. Marine parasites such as the bopyrid isopod, Probopyrus pandalicola, reduce shrimp growth and reproductive output and may also cause P. pugio to be more vulnerable to the lethal effects of contaminants. The purpose of this study was to determine the toxicity of resmethrin and bifenthrin on the grass shrimp, P. pugio, infected with the bopyrid isopod, Probopyrus pandalicola. A 96-h static renewal test was conducted to determine the toxicity of the pyrethroid insecticides resmethrin and bifenthrin to grass shrimp, Palaemonetes pugio, parasitized with the bopyrid isopod, Probopyrus pandalicola. The results were then compared to similar tests utilizing unparasitized P. pugio. Parasitized P. pugio had lower 24-h LC₅₀ (1.08 μg/L) and 96-h LC₅₀ (0.43 μg/L) values for resmethrin than unparasitized P. pugio. However, LC₅₀ ratio tests found that there was no significant difference between parasitized and unparasitized shrimp when affected by resmethrin (p = 0.1751 and 0.1108, respectively). In contrast, an LC₁₀ ratio test indicated that there was a significant difference between parasitized and unparasitized P. pugio after 96 h (p < 0.0001). When subjected to bifenthrin, parasitized P. pugio had a higher 24-h LC₅₀ (0.049 μg/L6) than unparasitized P. pugio. The LC₅₀ ratio test established that the effects of bifenthrin on parasitized P. pugio when compared to unparasitized P. pugio were significantly different at 24 h (p = 0.0065). However, there were no significant differences between parasitized and unparasitized after 96 h (p = 0.4229). In conclusion, both resmethrin and bifenthrin are toxic to the grass shrimp, P. pugio, regardless of parasite presence, and parasitized shrimp may be more susceptible to lower doses of resmethrin (when exposed in the field).