钙、氯对磷酸盐稳定污染土壤中铅的促进作用研究

为探讨促进磷酸盐稳定污染土壤中铅的方法,在全铅含量为517 mg·kg-1的铅冶炼污染土壤中加入5 mmol·kg-1磷酸盐,同时加入10mmol·kg-1硝酸钙或5 mmol·kg-1氯化钾,在15%或30%的含水率下培养40 d,之后种植黑麦草.结果表明,与单独施用磷酸盐相比,采用磷酸盐与钙、氯结合或增加培养期间的土壤含水率后,土壤DTPA-Pb含量下降3.92%~26.1%;对于同一添加剂处理,培养期间土壤含水率从15%增加到30%,土壤有效铅(DTPA-Pb)含量下降8.83%~24.4%.增加土壤含水率后,土壤有效磷(Olsen-P)含量均显著升高(p0.05).土壤铅的EXAFS分析表明,与未施用磷酸盐的对照相比,土壤中加入磷酸盐后矿物态铅的比例由57%上升至81%,加施钙、氯或增加土壤含水率后,多数处理矿物态铅的比例有所下降,而有机结合态铅比例上升.与对照相比,污染土壤中施用磷酸盐后,植物产量大幅增加,但施用钙、氯或增加培养期间含水率后,部分处理植物产量有所下降.以上结果表明,在铅冶炼污染土壤中加入磷酸盐时,加入钙、氯或者增加土壤含水率均有利于铅的稳定,但以上措施可能对植物生长产生不利影响.     

Uptake studies of environmentally hazardous (51)Cr in Mung beans

Attempt has been made to study the accumulation behaviour of a common plant, Mung bean (Vigna radiata) towards Cr(III) and Cr(VI) to have an insight on the migration and bio-magnification of Cr. For this purpose healthy germinated Mung bean seeds were sown in the sand in the presence of Hoagland's nutrient solution containing measured amount of K(2)(51)Cr(2)O(7) and (51)Cr(NO(3))(3).9H(2)O. Growth rate was also studied in the presence and absence of phosphate salts in the medium. It has been found that the transfer of chromium from soil to plant is significantly low (maximum 5% for both Cr(III) and Cr(VI)). Maximum accumulation of Cr occurs in the root with respect to the total chromium accumulation by the plant. Other parts of the Mung bean plant, e.g. cotyledons, shoot and leaves, show negligible accumulation. Therefore, the chance of direct intake of Cr through food as well as through the grazing animals to human body is less.     

Spatial and temporal variations of mercury levels in Okefenokee invertebrates: southeast Georgia

Accumulation of mercury in wetland ecosystems has raised concerns about impacts on wetland food webs. This study measured concentrations of mercury in invertebrates of the Okefenokee Swamp in Georgia, focusing on levels in amphipods, odonates, and crayfish. We collected and analyzed total mercury levels in these invertebrates from 32 sampling stations across commonly occurring sub-habitats. Sampling was conducted in December, May, and August over a two-year period. The highest levels of mercury were detected in amphipods, with total mercury levels often in excess of 20 ppm. Bioaccumulation pathways of mercury in invertebrates of the Okefenokee are probably complex; despite being larger and higher in the food chain, levels in odonates and crayfish were much lower than in amphipods. Mercury levels in invertebrates varied temporally with the highest levels detected in May. There was a lack of spatial variation in mercury levels which is consistent with aerial deposition of mercury.     

Short- and medium-term effects of experimental nitrogen fertilization on arthropods associated with Calluna vulgaris heathlands in north-west Spain

We studied the short- and medium-term effects of experimental nitrogen fertilization (3 and 15 months after the treatment) on the arthropods of Calluna vulgaris heathlands in NW Spain. Three heathland sites were selected with two permanent plots per site: control and fertilized. Ammonium nitrate fertilizer (56 kg N ha(-1) yr(-1)) was applied monthly and insects were caught using pitfall traps. We found mainly species-level responses to nitrogen addition. Seven species (e.g. Lochmaea suturalis) showed a consistent trend (benefited or harmed) in both periods and were proposed as possible reliable indicators of the effects of nitrogen deposition in these ecosystems. We also found variable arthropod trophic-group responses: (a) herbivores (leaf beetles, true bugs) increased in abundance on a short-term scale; (b) predators (carabid beetles, true bugs) showed opposite and less clear responses in both periods. Further long-term studies are needed to determine the mechanisms underlying the observed arthropod responses.     

Seasonal and particle size-dependent variations in gas/particle partitioning of PCDD/Fs

This study monitored particle size-dependent variations in atmospheric polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Two gas/particle partitioning models, the subcooled liquid vapor pressure (P(L)(0)) and the octanol-air partition coefficient (K(OA)) model, were applied to each particle sizes. The regression coefficients of each fraction against the gas/particle partition coefficient (K(P)) were similar for separated particles within the same sample set but differed for particles collected during different periods. Gas/particle partitioning calculated from the integral of fractions was similar to that of size-segregated particles and previously measured bulk values. Despite the different behaviors and production mechanisms of atmospheric particles of different sizes, PCDD/F partitioning of each size range was controlled by meteorological conditions such as atmospheric temperature, O(3) and UV, which reflects no source related with certain particle size ranges but mixed urban sources within this city. Our observations emphasize that when assessing environmental and health effects, the movement of PCDD/Fs in air should be considered in conjunction with particle size in addition to the bulk aerosol.     

U and Th in some brown coals of Serbia and Montenegro and their environmental impact

GOAL, SCOPE AND BACKGROUND: The objective of this paper is to determine and compare the concentrations of U and Th in soft to hard brown (lignite to sub-bituminous) coals of Serbia and Montenegro. It also presents comparison of the obtained data on U and Th concentrations with the published data on coals located in some other countries of the world. Almost the whole coal production of Serbia and Montenegro is used as feed coals for combustion in thermal power plants. METHODS: Channel samples from open pit and underground mines and core samples were collected for hard and soft brown coals. For the analysis the samples were decomposed using microwave technique. Obtained solutions containing U and Th were analyzed by inductively coupled plasma mass spectroscopy (ICP-MS) using NIST standards. RESULTS: Concentration of U from the investigated basins and the corresponding mine fields ranges within 0.60-70.10 mg/kg, 0.65-3.20 mg/kg, 0.95-6.59 mg/kg, 1.20-6.05 mg/kg, 0.80-6.66 mg/kg, 0.18-89.90 mg/kg, 0.19-4.14 mg/kg, and 0.28-3.52 mg/kg for the Kostolac, Kolubara, Krepoljin, Sjenica, Soko Banja, Bogovina East field, Senje-Resavica and Pljevlja basins, respectively. Concentration of Th ranges within 0.20-2.60 mg/kg, 0.84-6.57 mg/kg, 1.48-6.48 mg/kg, 0.12-2.71 mg/kg, 0.13-4.95 mg/kg, 0.14-3.48 mg/kg, 0.29-3.56 mg/kg, and 0.17-1.89 mg/kg for the Kostolac, Kolubara, Krepoljin, Sjenica, Soko Banja, Bogovina East field, Senje-Resavica and Pljevlja basins, respectively. DISCUSSION: Brown coal from Senje-Resavica, Kolubara, Kostolac and Pljevlja is characterized by low U concentration. Coals form the Krepoljin, Soko Banja and Sjenica basins have slightly higher U concentrations than the mentioned group. The highest concentration of U is characteristic for the coal from the Bogovina East field. Concentration of Th in coals from Serbia and Montenegro has proved to be low. Out of all investigated coal basins, only the coal from the Krepoljin and Kolubara basins has high concentration of Th. The hydrothermally altered rocks of the Timok dacite-andesite complex, representing the basement of the Bogovina basin, could be a potential source of U, especially at the bottom part of the Lower seam of the Bogovina East field. CONCLUSIONS: This study shows that brown coals in Serbia and Montenegro (soft to hard brown coals or lignite to sub-bituminous) contain low levels of U (5.30 mg/kg, average value and 2.10 mg/kg geometric mean value) and Th (1.80 mg/kg, average value and 1.12 mg/kg geometric mean value). There are some obvious differences in concentration of U and Th in coals from different basins in Serbia and Montenegro. The approximate value for U and Th release mainly from power plants was 644.33 t and 983.46 t, respectively within the period 1965-2000 for the studied mines in Serbia, and 23.76 t and 15.05 t for the Potrlica mine (Montenegro) within the period 1965-1997. RECOMMENDATIONS: The coals in Serbia and Montenegro show no identifiable unfavourable impact on the surrounding environment, due to low natural radioactive concentration of U and Th, but further investigations concerning human health should be performed. PERSPECTIVES: Preliminary research revealed that in some Serbian coals (and, particularly, parts of the coal seam) U and Th content are rather high. Such coals should be carefully studied, as well as U and Th concentrations in ash, fly ash, waste disposals, nearby soil and ground water. Further studies should include determination of the radioactivity of all these products, and estimation of possible health impact.     

Hepatic monooxygenase (CYP1A and CYP3A) and UDPGT enzymatic activities as biomarkers for long-term carbofuran exposure in tench (Tinca tinca L)

The effect of a long-term exposure of tenchs to different concentrations (10 and 100 micro g/L) of the pesticide carbofuran has been evaluated. Microsomal hepatic cytochrome P450 subfamily 1A (CYP1A) and 3A (CYP3A) activities, as well as the phase II enzyme uridine diphospho-glucuronosyltransferase (UDPGT) activity were evaluated as adequate biomarkers of fish exposure to environmentally relevant concentrations of the pesticide carbofuran in freshwater ecosystems. A clear time-dependent inhibition of both CYP1A and UDPGT activities was observed in fish exposed to the highest dose of carbofuran with respect to controls, whereas in the case of CYP3A activity, values of exposed animals did not show a clear pattern of alteration during the experiment. The results of the present study demonstrated that hepatic CYP1A and UDPGT activities from tench could be considered as sensitive biomarkers for carbamate pesticides in polluted water, thus allowing future and ecologically relevant biomonitoring studies with this species.     

A preliminary in vitro assessment of GroBiotic-A, brewer's yeast and fructooligosaccharide as prebiotics for the red drum Sciaenops ocellatus

This study examined the effects of brewers yeast, fructooligosaccharide (FOS), and GroBiotic-A, a mixture of partially autolyzed brewers yeast, dairy components and dried fermentation products, on the intestinal microbial community of red drum, Sciaenops ocellatus. Gastrointestinal (GI) tracts were aseptically removed from three sub-adult red drum previously maintained on a commercial diet and placed in an anaerobic chamber. Intestinal contents were removed, diluted and incubated in vitro in one of four liquid media: normal diet alone, diet + 2% (w/w) GroBiotic-A, diet + 2% brewers yeast, and diet + 2% FOS. After 24 and 48 h of incubation at 25 degrees C, supernatants were removed for volatile fatty acid (VFA) analysis and DNA was extracted for denaturing gradient gel electrophoresis (DGGE) analysis. Polymerase chain reaction (PCR) was performed on a highly conserved region of M 16S rDNA and the amplicons were subjected to DGGE. The microbial community (MC) fingerprint was used to distinguish microbial populations. The intestinal contents incubated with GroBiotic-A had significantly (P<0.05) higher acetate and total VFA concentrations at 48 h compared to the other treatments. DGGE analysis demonstrated that the microbial community was significantly altered by Grobiotic-A and brewers yeast.     

Is the integration of hormesis and essentiality into ecotoxicology now opening Pandora's Box?

Hormesis and essentiality are likely real and common effects at the level of the individual. However, the widespread incorporation of stimulatory effects into applications of ecotoxicology requires the acceptance of assumptions, value judgements and possibly lowering of water/sediment quality standards. There is also currently little data appropriate for considering hormetic effects in the ecotoxicological context. Except perhaps in the case of fitting concentration-response curves, it is not clear that incorporation of hormetic and essentiality type responses into ecotoxicology is necessary. Furthermore, its incorporation presents considerable intellectual and practical changes for ecotoxicology and could have unanticipated consequences.     

In field arsenic removal from natural water by zero-valent iron assisted by solar radiation

An in situ arsenic removal method applicable to highly contaminated water is presented. The method is based in the use of steel wool, lemon juice and solar radiation. The method was evaluated using water from the Camarones River, Atacama Desert in northern Chile, in which the arsenic concentration ranges between 1000 and 1300 μg L⁻¹. Response surface method analysis was used to optimize the amount of zero-valent iron (steel wool) and the citrate concentration (lemon juice) to be used. The optimal conditions when using solar radiation to remove arsenic from natural water from the Camarones river are: 1.3 g L⁻¹ of steel wool and one drop (ca. 0.04 mL) of lemon juice. Under these conditions, removal percentages are higher than 99.5% and the final arsenic concentration is below 10 μg L⁻¹. This highly effective arsenic removal method is easy to use and inexpensive to implement.