Aufnahme von Cyanid in Pflanzen

Cyanides are waste products from the pyrolysis of coal and are frequent soil pollutants in cities nowadays. Prussic acid (HCN) is a fast acting, highly toxic poison, but iron-complexed cyanides in soil are far less toxic. The phytotoxicity of free CN to basket willows (Salix viminalis) was determined with the tree transpiration test. The EC₁₀ for t=72 h is 0.76 mg KCN (0.3 mg CN) per liter, the EC₅₀ is 4.47 mg/l. 5 mg/l KCN are ultimately lethal. Balsam poplars (Populus trichocarpa) can survive concentrations of up to 2500 mg/l ferroferricyanide (Prussian blue), although with reduced growth. Willows survived in gas work soils with up to 452 mg/kg total CN. More CN was taken up from nutrient solution than from the soil. Complexed cyanide is probably translocated into the leaves as well. Free CN was readily eliminated from Erlenmeyers with plants growing in nutrient solution. Planting appropriate vegetation might be a suitable solution for many former gas work and mining sites.     

Experimente zum Verbleib von Cyanid nach Aufnahme in Pflanzen

Free cyanide (prussic acid) can be degraded by many organisms. Experimental data on the kinetics of degradation by plants, however, are rare. We experimentally determined the mass balance of potassium cyanide in the system nutrient solution/plant/air In the presence of living willows (Salix alba) and light, free cyanide is almost completely eliminated from the nutrient solution, also by a willow cell suspension (> 99%) and even by a dried-out stem (> 80%). The loss is smaller when the willow is autoclaved (30%). Without a willow, the CN can be recovered to more than 89%. The loss depends on light and transpiration. Volatilization and the formation of complexed cyanide are of minor relevance for the elimination of free CN. The most plausible loss process is metabolism by plants. The transfer into the roots and stem does not change with the light/dark-rhythm. The transfer factor (mg CN/kg plant fw/mg CN/l solution) after 24 h, and related to the initial concentration in solution, is between 2 and 3 for roots, 0.1 to 0.6 for leaves and 0.2 for stems. In the roots of willows and elderberries which were growing on the former gas worksite in Holte, Denmark, high concentrations of cyanides were found. In leaves and fruits, concentrations are a factor of 10 to 1000-fold lower and up to as high as that found in non-exposed control plants. Due to these results, a cyanide-polluted site in Denmark has been remediated with poplar trees.     

Analytik von Umwandlungsprodukten des Schwefellosts (S-LOST)

The results of investigations of the aquatic ecotoxicity of sternutators and their metabolites (phenyl arsenic compounds) are presented. The standardized luminescence inhibition test (LumisTox, Dr. Lange) with the marine bacteriaVibrio fischeri was applied according to the German norm DIN 38412, part 34. All investigated organic AS(III) compounds exhibit EC₅₀-values (50 % inhibition of the luminescence) of less than 1 mg/l, whereas all investigated organic As(V) compounds and inorganic arsenic show EC₅₀-values exceeding 100 mg/l     

Evaluation of tests to assess the quality of mine-contaminated soils

An acid metal-contaminated soil from the Aljustrel mining area (a pyrite mine located in SW Portugal in the Iberian Pyrite Belt) was subjected to chemical characterisation and total metal quantification (Cd, Cr, Cu, Ni, Pb and Zn). Water-soluble metals were determined and a sequential extraction procedure was used to investigate metal speciation. Two bioavailable metal fractions were determined: a mobile fraction and a mobilisable fraction. Soil ecotoxicity was studied using a battery of bioassays: plant growth test and seed germination with cress (Lepidium sativum L.), earthworm (Eisenia fetida) mortality, E. fetida avoidance behaviour, luminescent inhibition of Vibrio fischeri and Daphnia magna immobilisation. Although the total content of Cu, Zn and Pb in the soil was large (362, 245 and 1,250 mg/kg dry matter, respectively), these metals were mostly structurally bound (87% for Cu, 81% for Zn and 89% for Pb) and, therefore, scarcely bioavailable. Nonetheless, the D. magna immobilization test using soil leachate showed an EC₅₀ (48 h) of 36.3% (v/v), and the luminescent inhibition of V. fischeri presented an EC₂₀ (15 min) of 45.2% and an EC₂₀ (30 min) of 10.7% (v/v), suggesting a considerable toxic effect. In the direct exposure bioassays, E. fetida avoided the mine soil at the highest concentrations (50%, 75% and 100% v/v). At the same soil concentrations, cress showed negligible growth. The results suggest the need to use a battery of toxicity tests, in conjunction with chemical methods, in order to assess the quality of mine-contaminated soils correctly.     

土壤水溶态铜对小白菜的毒害效应及其预测模型

土壤中铜(Cu)重金属的生物毒性/有效性主要取决于它们在土壤液相中含量和土壤溶液的性质。探寻土壤有效态Cu的生物毒害效应,表征量化其与土壤溶液性质关系,可为土壤Cu的环境风险评价提供参考。选取17种典型农田土壤,探讨了有效态Cu(土壤孔隙水以及CaCl_2浸提态)对小白菜生长的毒性效应及其预测模型。结果表明:土壤孔隙水中Cu对小白菜生长10%抑制的毒性阈值值(EC_(10))和50%抑制的毒性阈值(EC_(50)),最大值与最小值相差为14.7和14.6倍;同样,对于CaCl_2提取态Cu的EC_(10)和EC_(50),最大值与最小值相差12.7和7.7倍,表明土壤溶液性质对水溶性Cu对小白菜的毒性阈值影响很大。建立了土壤溶液的重要因子(溶解性有机碳、土壤溶液pH值、电导率、全硫含量、Ca~(2+)、Mg~(2+)、K~+、Na~+)和水溶性Cu阈值之间的多元回归关系,结果显示,土壤溶液性质可以较好地预测水溶性Cu对小白菜的毒性阈值。同时,土壤溶液中Mg~(2+)、K~+和S的含量是控制孔隙水中Cu对小白菜生长毒性的最重要因子,单一的S能分别解释34%的EC_(10)变异,K~+解释26%的EC_(50)变化。本研究结果可为陆地环境中水溶性Cu的风险评价提供基础。     

土壤Cd污染对跳虫Folsomia candida的生态毒性

采矿及冶炼等行为造成了严重的土壤重金属污染,其中Cd污染及其带来的健康风险近年来引起人们的高度重视。利用弹尾目跳虫开展土壤Cd污染的生态毒理研究,对Cd污染土壤的生态风险评价具有重要意义。本研究将跳虫Folsomia candida(F.candida)暴露在不同Cd浓度污染的人工土壤中,利用跳虫存活数量、繁殖数量及回避行为实验来评价重金属Cd污染对跳虫的生态毒性。结果表明,Cd对F.candida的急性毒性LC50值为2 086.93 mg·kg~(-1),慢性毒性的繁殖抑制(28 d)EC50值为224.95 mg·kg~(-1)。此外,Cd对跳虫回避行为影响的EC50(48 h)为721.26 mg·kg~(-1)。可以看出,慢性毒性的EC50值与Cd对回避行为影响的EC50值近似,但远低于急性毒性LC50值。因此,跳虫F.candida的回避行为和繁殖率对Cd污染土壤有较高的灵敏度,可用来表征土壤中Cd的生态毒性。     

Evaluation of the toxicity of tetrabromobisphenol A and some of its oxidation products using a micro-scale algal growth inhibition test

A micro-scale algal growth inhibition (μ-AGI) test using a common micro-plate based fluorometric detection was used to demonstrate the effects of humic substances (HSs) on the toxicity of tetrabromobisphenol A (TBBPA) and its oxidative decomposition products 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), 2,5-dibromohydroquinone (2,5-DBHQ), 2,6-dibromobenzoquinone (2,6-DBBQ), and 2,6-dibromophenol (2,6-DBP) to Pseudokirchneriella subcapitata. The EC₅₀ values were: EC_50(TBBPA) = 7 mg L^?1, EC_50(2,5-DBHQ) = 7 mg L^?1, EC_50(2,5-DBBQ) = 19 mg L^?1, EC_50(2,6-DBP) = 49 mg L^?1, and EC_50(2,6-DBBQ) = 13 mg L^?1. The toxicity of the chemicals was slightly lower in the presence of HA. The toxicity of TBBPA decomposed by a biomimetic catalytic system consisting of iron (III) 5,10,15,20-tetrakis (p-sulfonatophenyl) porphyrin (Fe(III)-TPPS) and KHSO₅ was also evaluated using P. subcapitata and Chlamydomonas reinhardtii.     

Effects of the insecticide sevin and its first hydrolytic product, 1-naphthol,on some early developmental stages of the bay mussel Mytilus edulis

Six developmental stages of the bay mussel Mutilus edulis, from fertilization to 32 h after fertilization, and also unfertilized eggs, were exposed for 1 h to different concentrations of the insecticide Sevin and its first hydrolytic product, 1-naphthol. After exposure, the larvae or eggs were separated from the pesticide solution and returned to clean water. At 48 h after fertilization, the numbers of normal and abnormal larvae were determined and 1-h EC₅₀ values (the effective concentrations that caused anomalous development of 50% of the test animals) were calculated. The most sensitive developmental stage was the one that occurred shortly after fertilization at the time of appearance of the first polar body. Thereafter, sensitivity decreased as age increased. The EC₅₀ of Sevin for the first polar body stage and 32-h stage were 5.3 and 24.0 mg/l of Sevin, respectively. The EC₅₀ of l-naphthol for the first polar body stage was 5.2 mg/l. Effects of the toxicants on development were characterized by disjunction of blastomeres, a reduction in the rate of development, and asynchronous and unaligned cleavages.     

Songbird response to increased willow (Salix spp.) growth in Yellowstone's northern range

After nearly a century of height suppression, willows (Salix spp.) in the northern range of Yellowstone National Park, U.S.A., are increasing in height growth as a possible consequence of wolf (Canis lupus) restoration, climate change, or other factors. Regardless of the drivers, the recent release of this rare but important habitat type could have significant implications for associated songbirds that are exhibiting declines in the region. Our objective was to evaluate bird response to releasing willows by comparing willow structure and bird community composition across three willow growth conditions: height suppressed, recently released, and previously tall (i.e., tall prior to the height increase of released willows). Released and previously tall willows exhibited high and similar vertical structure, but released willows were significantly lower in horizontal structure. Suppressed willows were significantly shorter and lower in horizontal cover than released or previously tall willows. Bird richness increased along a gradient from lowest in suppressed to highest in previously tall willows, but abundance and diversity were similar between released and previously tall willows, despite lower horizontal cover in the released condition. Common Yellowthroat (Geothlypis trichas) and Lincoln's Sparrow (Melospiza lincolnii) were found in all three growth conditions; however, Yellow Warbler (Dendroica petechia), Warbling Vireo (Vireo gilvus), Willow Flycatcher (Empidonax traillii), and Song Sparrow (Melospiza melodii) were present in released and previously tall willows only. Wilson's Warbler (Wilsonia pusilla) was found in previously tall willows only, appearing to specialize on tall, dense willows. The results of our a priori habitat models indicated that foliage height diversity was the primary driver of bird richness, abundance, and diversity. These results indicate that vertical structure was a more important driver of bird community variables than horizontal structure and that riparian and willow-dependent bird species have responded positively to increased willow growth in the region.     

Water budget and the consequent duration of canopy carbon gain in a teak plantation in a dry tropical region: Analysis using a soil–plant–air continuum multilayer model

A soil–plant–air continuum multilayer model was used to numerically simulate canopy net assimilation (A_n), evapotranspiration (ET), and soil moisture in a deciduous teak plantation in a dry tropical climate of northern Thailand to examine the influence of soil drought on A_n. The timings of leaf flush and the end of the canopy duration period (CDP) were also investigated from the perspective of the temporal positive carbon gain. Two numerical experiments with different seasonal patterns of leaf area index (LAI) were carried out using above-canopy hydrometeorological data as input data. The first experiment involved seasonally varying LAI estimated based on time-series of radiative transmittance through the canopy, and the second experiment applied an annually constant LAI. The first simulation captured the measured seasonal changes in soil surface moisture; the simulated transpiration agreed with seasonal changes in heat pulse velocity, corresponding to the water use of individual trees, and the simulated A_n became slightly negative. However, in the second simulation, A_n became negative in the dry season because the decline in stomatal conductance due to severe soil drought limited the assimilation, and the simultaneous increase in leaf temperature increased dark respiration. Thus, these experiments revealed that the leaflessness in the dry season is reasonable for carbon gain and emphasized the unfavorable soil water status for carbon gain in the dry season. Examining the duration of positive A_n (DPA) in the second simulation showed that the start of the longest DPA (LDPA) in a year approached the timing of leaf flush in the teak plantation after the spring equinox. On the other hand, the end appeared earlier than that of all CDPs. This result is consistent with the sap flow stopping earlier than the complete leaf fall, implying that the carbon assimilation period ends before the completion of defoliation. The model sensitivity analysis in the second simulation suggests that a smaller LAI and slower maximum rate of carboxylation likely extend the LDPA because soil water from the surface to rooting depth is maintained longer at levels adequate for carbon gain by decreased canopy transpiration. The experiments also suggest that lower soil hydraulic conductivity and deeper rooting depth can postpone the end of the LDPA by increasing soil water retention and the soil water capacity, respectively.     

柴油污染土壤生物修复对土壤酶活性的影响

在柴油污染土壤的生物修复过程中,分析了土壤中柴油降解菌数量和3种土壤酶活性(过氧化氢酶、脱氢酶和脂酶)等生物活性指标与土壤中柴油去除率的相关性.结果表明,土壤受到柴油污染后的一段时间后过氧化氢酶、脱氢酶和脂酶的活性上升,而后随着土壤中石油烃的降解,脂酶又不断降低.进一步分析表明脂酶活性与柴油降解率及柴油降解菌数量都具有很好的正相关性,可以采用土壤脂酶活性来指示柴油生物降解成效.     

The role of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans in arsenic bioleaching from soil

Bioleaching of As from the soil in an abandoned Ag–Au mine was carried out using Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. A. ferrooxidans is an iron oxidizer and A. thiooxidans is a sulfur oxidizer. These two microbes are acidophilic and chemoautotrophic microbes. Soil samples were collected from the Myoungbong and Songcheon mines. The main contaminant of the soil was As, with an average concentration of 4,624 mg/kg at Myoungbong and 5,590 mg/kg at Songcheon. A. ferrooxidans and A. thiooxidans generated lower pH conditions during their metabolism process. The bioleaching of As from soil has a higher removal efficiency than chemical leaching. A. ferrooxidans could remove 70 % of the As from the Myoungbong and Songcheon soils; however, A. thiooxidans extracted only 40 % of the As from the Myoungbong soil. This study shows that bioleaching is an effective process for As removal from soil.     

Future distribution modelling: A stitch in time is not enough

The last two decades have seen an increasing number of studies assessing the impact of climate change upon biodiversity. A central assumption underpinning research into the potential future habitat of terrestrial biota is that species are presently in equilibrium with their environments and that quantitative climate models adequately represent the distribution of species. Recently, many alarming predictions have emerged concerning the extinction and redistribution of species. Here, we show that even large-scale models of the climatic niche dimensions of species are temporally variable. Distributional models were developed for Salix (willow) species occurring in the province of Ontario, Canada, using three historical climate data sets. Although historical data very accurately represented the distributions of willows, the inherent variability within the models of species based on different periods greatly influenced the direction and magnitude of projected distributional change. We expose a fundamental uncertainty with respect to predicting the responses of species to climate change.     

Application of microcosm and species sensitivity distribution approaches in the ecological hazard assessment of 4-tert-butylphenol

In order to evaluate the ecological hazard of 4-tert-butylphenol (4-TBP), species abundances and physicochemical properties were monitored for 63 days in a microcosm system containing planktonic algae, rotifers, shrimps and Daphnia. The 63 days-NOEC (no observed effect concentration) of 4-TBP for this system was calculated. At the same time, species sensitivity distribution curves were constructed based on the toxicity data of EC₁₀, EC₅₀ and NOEC derived from laboratory single-species toxicity tests, which further gives no obvious hazard concentrations for 95% species in the ecosystem (HC₅). In both the microcosm and the single-species tests, the shrimp (Neocaridina sp.) was the most sensitive species to 4-TBP exposure, while most algae species were relatively insensitive compared to the zooplankton. For the microcosm exposed to 4-TBP, significant changes occurred to the community structure instead of the community function, resulting in a NOEC_microcosm of 265.38?μg?L^–1 which approached the EC₁₀-based HC₅ (0.376?mg?L^–1). Nevertheless, EC₅₀-based HC₅ was higher than the NOEC_microcosm, and the NOEC-based HC₅ was lower. The data showed that the EC₁₀-based HC₅ was protective at the similar level with the result of microcosm for 4-TBP, providing supportive data for chemical risk assessment.     

Evaluation and assessment of the efficacy of an abatement strategy in a former lead smelter community,Boolaroo, Australia

This study examines the recent soil Lead Abatement Strategy (LAS) in Boolaroo, New South Wales, Australia, that was designed to “achieve a reduction in human exposure to lead dust contamination in surface soils”. The abatement programme addressed legacy contamination of residential areas following closure of lead smelting operations in 2003 at the Pasminco Cockle Creek Smelter (PCCS). The principal objective of the LAS was to “cap and cover” lead-contaminated soils within the urban environment surrounding the PCCS. Soil lead concentrations of 2500–5000 mg/kg were scheduled for removal and replacement, while concentrations between 1500 and 2500 mg/kg were replaced only under limited circumstances. To date, there has been no industry, government or independent assessment of the clean-up programme that involved >2000 homes in the township of Boolaroo. Thus, by measuring post-abatement soil lead concentrations in Boolaroo, this study addresses this knowledge gap and evaluates the effectiveness of the LAS for reducing the potential for lead exposure. Soil lead concentrations above the Australian residential soil health investigation level value for residential soils (300 mg/kg) were identified at all but one of the residential properties examined (n = 19). Vacuum dust samples (n = 17) from the same homes had a mean lead concentration of 495 mg/kg (median 380 mg/kg). Bio-accessibility testing revealed that lead in household vacuum dust was readily accessible (% bio-accessible) (mean = 92 %, median = 90 %), demonstrating that the risk of exposure via this pathway remains. Assessment of a limited number of properties (n = 8) where pre-abatement soil lead levels were available for comparison showed they were not statistically different to post-abatement. Although the LAS did not include treatment of non-residential properties, sampling of community areas including public sports fields, playgrounds and schools (n = 32) was undertaken to determine the contamination legacy in these areas. Elevated mean soil lead concentrations were found across public lands: sports fields = 5130 mg/kg (median = 1275 mg/kg), playgrounds and schools = 812 mg/kg (median = 920 mg/kg) and open space = 778 mg/kg (median = 620 mg/kg). Overall, the study results show that the LAS programme that was dominated by a “cap and cover” approach to address widespread lead contamination was inadequate for mitigating current and future risk of lead exposures.     

镉对北京城郊土壤潜在硝化速率的影响

采集北京城郊5个区县的3种土壤褐土、潮土和山地棕壤,通过急性毒性实验,研究了外源添加镉(Cd)对土壤潜在硝化速率(PNR)的影响。结果表明,5个采样点土壤的PNR分别随土壤中总Cd和有效态Cd含量呈先增后减的趋势。所有处理土壤的有效态Cd含量与PNR的相关关系(R2=0.42,p0.001)优于土壤总Cd含量与PNR的相关关系(R2=0.27,p=0.001)。在土壤总Cd含量和PNR的逐步回归分析中,引入土壤有机质和阳离子交换量(CEC)2个变量可提高其相关性。基于土壤总Cd的EC50(PNR降低至对照50%时的土壤Cd浓度)和有效态Cd的EC50的最大值与最小值之间分别相差2.3倍和3.3倍,而EC10(PNR降低至对照10%的土壤Cd浓度)的最大值与最小值之间分别相差8.5倍和10.8倍。基于总Cd的EC50最低值出现在CEC最小的丰台土壤,而最高值出现在有机质含量最多的灵山土壤,但这2个EC50值未达到显著性差异,表明5个采样点的土壤有机质和CEC虽然在一定程度上影响Cd对PNR的毒性,但不足以引起EC50的显著变化。     

Hydrologic regime and herbivory stabilize an alternative state in Yellowstone National Park.

A decline in the stature and abundance of willows during the 20th century occurred throughout the northern range of Yellowstone National Park, where riparian woody-plant communities are key components in multiple-trophic-level interactions. The potential causes of willow decline include climate change, increased elk browsing coincident with the loss of an apex predator, the gray wolf, and an absence of habitat engineering by beavers. The goal of this study was to determine the spatial and temporal patterns of willow establishment through the 20th century and to identify causal processes. Sampled willows established from 1917 to 1999 and contained far fewer young individuals than was predicted from a modeled stable willow population, indicating reduced establishment during recent decades. Two hydrologically distinct willow establishment environments were identified: fine-grained beaver pond sediments and coarse-grained alluvium. Willows established on beaver pond sediment earlier in time, higher on floodplain surfaces, and farther from the current stream channel than did willows on alluvial sediment. Significant linear declines from the 1940s to the 1990s in alluvial willow establishment elevation and lateral distance from the stream channel resulted in a much reduced area of alluvial willow establishment. Willow establishment was not well correlated with climate-driven hydrologic variables, but the trends were consistent with the effects of stream channel incision initiated in ca. 1950, 20-30 years after beaver dam abandonment. Radiocarbon dates and floodplain stratigraphy indicate that stream incision of the present magnitude may be unprecedented in the past two millennia. We propose that hydrologic changes, stemming from competitive exclusion of beaver by elk overbrowsing, caused the landscape to transition from a historical beaver-pond and willow-mosaic state to its current alternative stable state where active beaver dams and many willow stands are absent. Because of hydrologic changes in streams, a rapid return to the historical state may not occur by reduction of elk browsing alone. Management intervention to restore the historical hydrologic regime may be necessary to recover willows and beavers across the landscape.     

Bark salicylates and condensed tannins reduce vole browsing amongst cultivated dark-leaved willows (<Emphasis Type="Italic">Salix myrsinifolia</Emphasis>)

Summary. Vole feeding amongst herbal willows that have a high concentration of salicylates in their bark and leaves, and may therefore be cultivated for use as raw material for herbal medicine was tested in the field and in laboratory conditions. Eight clones of dark-leaved willow (Salix myrsinifolia Salisb.) were cultivated for two years with six different methods combining three fertilisation levels (none, low and high), black plastic mulch applied for suppressing weed competition and unmulched control. Samples for the laboratory feeding trial were taken from the unfertilised plants during willow winter dormancy and twigs were fed to 16 voles as a multi-choice experiment. The bark area removed was calculated from image analysis of the material left by the voles. The diameter and the bark thickness of the twigs were measured. Concentrations of salicin, salicortin, HCH-salicortin, picein, triandrin, triandrin derivative, gallocatechin, (+)-catechin, luteolin-7-glucoside, hyperin, total condensed tannins and total nitrogen were measured from the twigs fed to voles in the laboratory. Browsing by a natural population of voles amongst winter-dormant willows was measured in the field. In the laboratory, voles browsed on 80% of the twigs and in the field voles browsed on 33% of the twigs. Vole feeding followed similar patterns in the field and in the laboratory experiment; feeding was clearly higher amongst the plants grown in unmulched control compared to those in plastic mulch. The same clones, 1, 2 and 6 were preferred in both experiments. Voles preferred thin twigs to thick ones. Feeding correlated negatively with concentrations of salicylates and tannins. As vole feeding seems to be highly affected by willow cultivation method and plant genotype, careful selection of cultivated clones and cultivation methods can enhance the reliability of herbal willow cultivation.     

Microcystin-LR biodegradation by Sphingopyxis sp. USTB-05

A promising bacterial strain for biodegrading microcystin-LR (MC-LR) as the sole carbon and nitrogen source was successfully isolated from Lake Dianchi, China. The strain was identified as Sphingopyxis sp. USTB-05, which was the first isolated MCs-biodegrading Sphingopyxis sp. in China. The average biodegradation rate of MC-LR by Sphingopyxis sp. USTB-05 was 28.8 mg??L^?1 per day, which was apparently higher than those of other bacteria reported so far. The optimal temperature and pH for both strain USTB-05 growth and MC-LR biodegradation were 30??C and 7.0, respectively. The release of MC-LR from the cyanobacterial cells collected from Lake Guishui and the biodegradation of MC-LR by both strain and cell-free extract (CE) were investigated. The results indicated that MC-LR with the initial concentration of 4.0 mg??L^?1 in water was biodegraded by Sphingopyxis sp. USTB-05 within 4 d, while MC-LR with the initial concentration of 28.8 mg??L^?1 could be completely removed in 3 h by CE of Sphingopyxis sp. USTB-05 containing 350 mg??L^?1 protein. During enzymatic biodegradation of MC-LR, two intermediate metabolites and a dead-end product were observed on an HPLC chromatogram. Moreover, the similar scanning profiles of MC-LR and its metabolic products indicate that the Adda side-chain of MC-LR was kept intact in all products.