خيارات البحث
النتائج 221 - 230 من 798
Application of bioassays to evaluate a copper contaminated soil before and after a pilot-scale electrokinetic remediation النص الكامل
2009
Wang, Quan-Ying | Zhou, Dong-Mei | Cang, Long | Sun, Tian-Ran
Remediation programmes are considered to be complete when human risk-based criteria are met. However, these targets are often unsatisfied with the ecological parameters that may be important with regard to future soil use. Five soil subsamples, collecting along a pilot-scale soil column after electrokinetic treatment, were studied, from which about 42.0%-93.3% soil Cu had been successfully removed. A series of biological assays including soil microbial biomass carbon, basal soil respiration, soil urease activity, earthworm assays, and seed assays were used to evaluate their ecological risks. The results showed that the bioassay data from the treatment variants did not supposedly reflecting the decreased soil Cu concentrations after the electrokinetic treatment, but were highly correlated with some soil physicochemical characteristics. It suggests that bioassays are necessary to assess the ecotoxicity of soil after electrokinetic treatment.
اظهر المزيد [+] اقل [-]Geochemical processes of mercury in Wujiangdu and Dongfeng reservoirs, Guizhou, China النص الكامل
2009
Feng, Xinbin | Jiang, Hongmei | Qiu, Guangle | Yan, Haiyu | Li, Guanghui | Li, Zhonggen
The geochemical processes of mercury in Dongfeng (DF) and Wujiangdu (WJD) reservoirs, which were constructed in 1992 and 1979, respectively in Wujiang River, which is the upper branch of Yangtze River were investigated. One sampling site was chosen upriver of 1 km from the dam for each reservoir. Three sampling campaigns were conducted at these sampling sites in December 2003, April 2004 and July 2004, respectively. The distributions of different mercury species in the water column, sediment, and sediment pore water were studied. We found that the sediment is the net source of both inorganic and MeHg to the water column for both reservoirs. The MeHg diffusion fluxes in WJD reservoir at all sampling campaigns were significantly higher than those in DF reservoir. Our study demonstrated that the high primary productivity in the reservoir produced elevated organic matter content that would favor the methylmercury production in sediment. Surface sediment in the reservoirs is the active mercury methylating sites in the systems.
اظهر المزيد [+] اقل [-]Effects of a herbicide-insecticide mixture in freshwater microcosms: Risk assessment and ecological effect chain النص الكامل
2009
Brink, Paul J van den | Crum, Steven J.H. | Gylstra, Ronald | Bransen, Fred | Cuppen, Jan G.M. | Brock, Theo C.M.
Effects of chronic application of a mixture of the herbicide atrazine and the insecticide lindane were studied in indoor freshwater plankton-dominated microcosms. The macroinvertebrate community was seriously affected at all but the lowest treatment levels, the zooplankton community at the three highest treatment levels, with crustaceans, caddisflies and dipterans being the most sensitive groups. Increased abundance of the phytoplankton taxa Cyclotella sp. was found at the highest treatment level. Threshold levels for lindane, both at population and community level, corresponded well with those reported in the literature. Atrazine produced fewer effects than expected, probably due to decreased grazer stress on the algae as a result of the lindane application. The safety factors set by the Uniform Principles for individual compounds were also found to ensure protection against chronic exposure to a mixture of a herbicide and insecticide at community level, though not always at the population level. Effects of chronic application of a herbicide-insecticide mixture were studied in indoor freshwater plankton-dominated microcosms. Effects could well be explained by the effects of the individual chemicals alone, no synergetic effects were reported.
اظهر المزيد [+] اقل [-]PCB accumulation in osprey exposed to local sources in lake sediment النص الكامل
2009
De Solla Shane R. | Martin, Pamela A.
We examined the accumulation of PCBs in ospreys (Pandion haleaetus) that were exposed to local sediment sources. Eggs, chick plasma, and sediment samples were collected over a range of 14 km (0.2-14.2 km) from a PCB source in Sturgeon Lake, ON. Sum PCB concentrations declined in chick plasma (range 422.5-58.3 ng/g) as distance from the PCB source increased, but there was a poor relationship with sum PCBs in eggs. Both tissues indicated an Aroclor 1248/1254 source. Aroclor 1254 comprised an average of 66.9% of sum PCBs in chick plasma from Sturgeon Lake, but comprised only from 27.0 to 44.4% in plasma from other Great Lake colonies. Dietary differences among osprey colonies were not sufficient to explain the PCB patterns observed. There was weak evidence that the ability to metabolize PCBs may differ between juveniles and adults, based upon the PCB profile in eggs and chick plasma. PCBs in plasma and eggs of osprey reflect local sources of PCBs in sediment.
اظهر المزيد [+] اقل [-]Sampling atmospheric pesticides with SPME: Laboratory developments and field study النص الكامل
2009
Wang, Junxia | Tuduri, Ludovic | Mercury, Maud | Millet, Maurice | Briand, Olivier | Montury, Michel
To estimate the atmospheric exposure of the greenhouse workers to pesticides, solid phase microextraction (SPME) was used under non-equilibrium conditions. Using Fick's law of diffusion, the concentrations of pesticides in the greenhouse can be calculated using pre-determined sampling rates (SRs). Thus the sampling rates (SRs) of two modes of SPME in the lab and in the field were determined and compared. The SRs for six pesticides in the lab were 20.4-48.3 mL min-1 for the exposed fiber and 0.166-0.929 mL min-1 for the retracted fiber. In field sampling, two pesticides, dichlorvos and cyprodinil were detected with exposed SPME. SR with exposed SPME for dichlorvos in the field (32.4 mL min-1) was consistent with that in the lab (34.5 mL min-1). SR for dichlorvos in the field (32.4 mL min-1) was consistent with that in the lab (34.5 mL min-1). The trends of temporal concentration and the inhalation exposure were also obtained.
اظهر المزيد [+] اقل [-]The impact of semiconductor, electronics and optoelectronic industries on downstream perfluorinated chemical contamination in Taiwanese rivers النص الكامل
2009
Lin, Angela Yu-Chen | Panchangam, Sri Chandana | Lo, Chao-Chun
This study provides the first evidence on the influence of the semiconductor and electronics industries on perfluorinated chemicals (PFCs) contamination in receiving rivers. We have quantified ten PFCs, including perfluoroalkyl sulfonates (PFASs: PFBS, PFHxS, PFOS) and perfluoroalkyl carboxylates (PFCAs: PFHxA, PFHpA, PFOA, PFNA, PFDA, PFUnA, PFDoA) in semiconductor, electronic, and optoelectronic industrial wastewaters and their receiving water bodies (Taiwan's Keya, Touchien, and Xiaoli rivers). PFOS was found to be the major constituent in semiconductor wastewaters (up to 0.13 mg/L). However, different PFC distributions were found in electronics plant wastewaters; PFOA was the most significant PFC, contributing on average 72% to the effluent water samples, followed by PFOS (16%) and PFDA (9%). The distribution of PFCs in the receiving rivers was greatly impacted by industrial sources. PFOS, PFOA and PFDA were predominant and prevalent in all the river samples, with PFOS detected at the highest concentrations (up to 5.4 μg/L). The semiconductor, electronics and optoelectronic industries are the primary source of PFC contamination in downstream aqueous environments.
اظهر المزيد [+] اقل [-]Chelating agent-assisted electrokinetic removal of cadmium, lead and copper from contaminated soils النص الكامل
2009
Giannis, Apostolos | Nikolaou, Aris | Pentari, Despina | Gidarakos, Evangelos
An integrated experimental program was conducted to remove Cd, Pb and Cu from contaminated soil. The chelate agents nitrilotriacetic acid (NTA), diethylenetriamine pentaacetic acid (DTPA) and ethyleneglycol tetraacetic acid (EGTA) were used as washing solutions under different pH conditions and concentrations. Results showed that the extraction efficiency for Cd in decreasing order was NTA > EGTA > DTPA, while for Pb and Cu it was DTPA > NTA > EGTA. The use of higher chelate concentrations did not necessarily result in greater extraction efficiency. Electrokinetic remediation was applied by conditioning anolyte–catholyte pH to neutral values in order to avoid any potential alterations to the physicochemical soil properties. The removal efficiency for Cd was 65–95%, for Cu 15–60%, but for Pb was less than 20%. The phytotoxicity of the treated soil showed that the soil samples from the anode section were less phytotoxic than the untreated soil, but the phytotoxicity was increased in the samples from the cathode section. Cadmium, lead and copper were extracted from contaminated soil by integrated electrokinetic and soil washing studies.
اظهر المزيد [+] اقل [-]Comparing differential tolerance of native and non-indigenous marine species to metal pollution using novel assay techniques النص الكامل
2009
Piola, Richard F. | Johnston, Emma L.
Recent research suggests anthropogenic disturbance may disproportionately advantage non-indigenous species (NIS), aiding their establishment within impacted environments. This study used novel laboratory- and field-based toxicity testing to determine whether non-indigenous and native bryozoans (common within marine epibenthic communities worldwide) displayed differential tolerance to the common marine pollutant copper (Cu). In laboratory assays on adult colonies, NIS showed remarkable tolerance to Cu, with strong post-exposure recovery and growth. In contrast, native species displayed negative growth and reduced feeding efficiency across most exposure levels. Field transplant experiments supported laboratory findings, with NIS growing faster under Cu conditions. In field-based larval assays, NIS showed strong recruitment and growth in the presence of Cu relative to the native species. We suggest that strong selective pressures exerted by the toxic antifouling paints used on transport vectors (vessels), combined with metal contamination in estuarine environments, may result in metal tolerant NIS advantaged by anthropogenically modified selection regimes.
اظهر المزيد [+] اقل [-]Bags with oven-dried moss for the active monitoring of airborne trace elements in urban areas النص الكامل
2009
Giordano, S. | Adamo, P. | Monaci, F. | Pittao, E. | Tretiach, M. | Bargagli, R.
To define a harmonized methodology for the use of moss and lichen bags as active monitoring devices of airborne trace elements in urban areas, we evaluated the element accumulation in bags exposed in Naples in different spring weather conditions for 6- and 12-weeks. Three different pre-exposure treatments were applied to moss and lichen materials: water-washing, acid-washing and oven-drying. During the different exposure periods in the Naples urban environment the moss accumulated always higher amounts of elements (except Hg) than lichens and the element accumulation increased during wetter weather and higher PM10 conditions. The oven pre-treatment did not substantially modify the morphology and element composition of moss and the exposure in bags of this material for 6-weeks was sufficient to detect the pattern of airborne trace elements.
اظهر المزيد [+] اقل [-]Occurrence and behaviour of selected hydrophobic alkylphenolic compounds in the Danube River النص الكامل
2009
Micić, Vesna | Hofmann, Thilo
Six hydrophobic alkylphenolic compounds were investigated for the first time simultaneously in four different matrices in the Danube River. Maximum sediment concentrations were 2.83, 2.10, 0.28, and 0.035 mg kg⁻¹ for nonylphenol, nonylphenol monoethoxylate, nonylphenol diethoxylate and octylphenol. Maximum levels in suspended particulate matter (SPM) were 0.18, 0.12, 0.10, and 0.003 mg kg 1. No correlation between concentrations in SPM and sediments was found. Octylphenol monoethoxylate and octylphenol diethoxylate were recorded only in sediment at one location. In mussels and water only nonylphenol and octylphenol were found. Nonylphenol concentrations in mussels (up to 0.34 mg kg⁻¹) correlate with concentrations found in SPM and indicate a slight bioaccumulation. Concentrations in water were close to the limit of quantification. We assume in situ formation of nonylphenol monoethoxylate and nonylphenol in sediments at some locations. In some cases nonylphenol in sediments exceeded the provisional EU environmental quality standards.
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