共查询到16条相似文献,搜索用时 15 毫秒
1.
Abstract The pervasiveness of the plasticizer di‐(2‐ethylhexyl) phthalate (DEHP) in the environment and especially in the laboratory results in a background that may cause severe interference with analytical studies. Animal‐to‐animal variability in the distribution of DEHP metabolites in excreta normally makes it necessary to use large groups of animals when different treatments are compared. Finally, radioactive tracers are usually considered undesirable for metabolic studies involving human subjects. All of these problems can be overcome through the use of muliple isotopic labels, especially 12C/ 13C/ 14C. Examples are given involving rats and monkeys, and applicability to humans is discussed. The principles involved are not limited to any particular class of test compounds. In rats, the competing pathways for metabolism of phthalate esters produce a different distribution of metabolites from a small intravenous dose of DEHP than from a large oral dose. 相似文献
2.
Abstract 14C‐p,p'‐DDT‐bound residues in soil can be released by treatment with concentrated sulphuric acid at ambient temperatures. Within 6 days, about 70% of the bound residues was released. Bound residues released after 9 months incubation with 14C‐DDT showed the presence of DDT and DDE only while bound residues released after 18 months, contained in addition 13% DDD. Release of bound 14C‐residues also occurs readily following inoculation of the soil‐bound residues with fresh soil or with individual microorganisms. Almost complete release of bound residues was observed after incubation for 45 days. The rate of release was rapid during the first two weeks and decreased thereafter. TLC and HPLC analysis showed that the released residues contained DDE (about 80%) and a smaller amount of DDD. The disappearance of DDT from the released residues may be attributed to its microbiological degradation to DDE and DDD, shortly after its release. 相似文献
3.
Abstract Metabolic fate of two dichloromethyl diaryl phosphonates ( 32P labelled) in/on rice plants was investigated. The test compounds were found to be less persistent on the surface of rice leaves with half lives 7.4 and 6.7 days respectively. Main degradation product from both the phosphonates were dichloromethyl phosphonic acid with trace of dichloromethyl‐O‐aryl phosphonate as a transitory intermediate product. 相似文献
4.
Abstract Sheep metabolized a single oral dose of 2‐chloro‐ N‐isopro‐pylacetanilide (propachlor) to four urinary metabolites. These were 2‐( S‐cysteinyl)‐ N‐isopropylacetanilide and 2‐[ S‐( N‐acetyl) cysteinyl]‐ N‐isopropylacetanilide and the glucuronide conjugates of 4'‐hydroxy‐ N‐isopropyl‐2‐methylsulfonylacetanilide and N‐(1‐hydroxyisopropyl)‐2‐methylsulfonylacetanilide. Residues (ppb equivalents of propachlor) from [ 14C]‐propachlor in the milk from a goat given daily oral doses (1.3 mg of propachlor three times daily for 15 days) plateaued at about 2 to 4 ppb equivalents of propachlor. In goat tissue, residues ranged from 1 ppb (fat) to 20 ppb (liver). Fecal and tissue metabolites were not identified. 相似文献
5.
Abstract [Carbonyl‐ C]methabenzthiazuron (MBT) was applied to growing winter wheat in an outdoor lysimeter. The amount applied corresponded to 4 kg Tribunil/ha. 140 days after application the 0–2,5 cm soil layer was removed from the lysimeter. This soil contained about 40 % of the applied radioactivity. Using 0,01 M CaCl 2 solution or organic solvents, the extractable residues were removed from the soil. The bioavailability of the non‐extractable as well as aged residues remaining in the soil was investigated in standardized microecosystems containing 1.5 kg of dry soil. During a 4 weeks period the total uptake (4 maize plants/pot) amounted up to 3,6; 2,2; and 0,9 % of the radioactivity from soils containing aged MBT residues, MBT residues non‐extractable‐with 0,01 MCaCl 2 or MBT residues non‐extractable with organic solvents, respectively. About 20 % of the radioactivity found in maize leaves represented chromatographically characterized parent compound. At the end of the plant experiment the soil was extracted again with 0,01 M CaCl 2 and with organic solvents. The soil extracts and also the organic phases obtained from the aqueous fulvic acid solution contained unchanged parent compound. 相似文献
6.
In addition to direct photolysis studies, in this work the second-order reaction rate constants of pesticides imidacloprid (IMD) and ametryn (AMT) with hydroxyl radicals (HO●), singlet oxygen (1O2), and triplet excited states of chromophoric dissolved organic matter (3CDOM*) were determined by kinetic competition under sunlight. IMD and AMT exhibited low photolysis quantum yields: (1.23?±?0.07)?×?10–2 and (7.99?±?1.61)?×?10–3 mol Einstein?1, respectively. In contrast, reactions with HO● radicals and 3CDOM* dominate their degradation, with 1O2 exhibiting rates three to five orders of magnitude lower. The values of kIMD,HO● and kAMT,HO● were (3.51?±?0.06)?×?109 and (4.97?±?0.37)?×?109 L mol?1 s?1, respectively, while different rate constants were obtained using anthraquinone-2-sulfonate (AQ2S) or 4-carboxybenzophenone (CBBP) as CDOM proxies. For IMD this difference was significant, with kIMD,3AQ2S*?=?(1.02?±?0.08)?×?109 L mol?1 s?1 and kIMD,3CBBP*?=?(3.17?±?0.14)?×?108 L mol?1 s?1; on the contrary, the values found for AMT are close, kAMT,3AQ2S*?=?(8.13?±?0.35)?×?108 L mol?1 s?1 and kAMT,3CBBP*?=?(7.75?±?0.80)?×?108 L mol?1 s?1. Based on these results, mathematical simulations performed with the APEX model for typical levels of water constituents (NO3?, NO2?, CO32?, TOC, pH) indicate that the half-lives of these pesticides should vary between 24.1 and 18.8 days in the waters of the Paranapanema River (São Paulo, Brazil), which can therefore be impacted by intensive agricultural activity in the region. 相似文献
7.
In this work, the effects of diatomite with 15% FeSO 4?7H 2O and 7.5% Ca(OH) 2 on sludge stabilization were investigated using batch leaching tests. The influence of cell rupture caused by freezing and thawing on stabilization was also evaluated. The results indicated that the optimal diatomite percentage was 2%. Cell rupture by freezing and thawing reduced heavy metal leachability, followed by cell death and decrease of organic groups. The concentration of heavy metals in sludge leachate increased after cell rupture, indicating that the heavy metal leachability was reduced after freezing and thawings. Moreover, the stabilization effects were generally improved after freezing and thawing. As compared with the stabilization of the original sludge, the unstable fractions decreased and the residual fractions of the heavy metals increased in the stabilized sludge after cell rupture. Implications: This study developed a method to stabilize heavy metals in municipal sewage sludge. Diatomite combined with FeSO 4·7H 2O and Ca(OH) 2 improved the treatment of sewage sludge contaminated by heavy metals. Cell lysis by freeze–thaw treatment reduced the risk of leaching heavy metals caused by cell death and decreased major organic groups in the sludge. 相似文献
8.
The aim of this study was to determine the trace elements, Pb, Cd, and Cr in honey samples from eight different regions from the state of Paraná (Brazil), using slurry sampling graphite furnace atomic absorption spectrometry. Chemometric analysis (principal component analysis (PCA)) was applied to classify honey samples according to their levels of the trace elements Pb, Cd, and Cr, which is also related to the geographical origin of honey samples. The mean concentration for the elements followed the order Pb?>?Cr >?>?Cd. The mean values were 200?±?76, 88?±?14, and 4.1?±?4 ng g ?1 for Pb, Cr, and Cd, respectively. It could be verified that honey samples are geographically separated, especially with regard to Pb and Cd contents. Thus, honey can be considered a bioindicator of environmental contamination, suggesting possible contamination in soil, water, and air. This contamination can be related to natural or anthropogenic sources present in the study regions. 相似文献
9.
Environmental Science and Pollution Research - The aim of this study was to analyze the occurrence of sulfonamide resistance genes (sul1–3) and other genetic elements as antiseptic resistance... 相似文献
10.
Concentrations and tissue distribution of organochlorine pesticides (OCPs) in different tissues of freshwater fish, silver carp ( Hypophthalmichthys molitrix) and bighead carp ( Aristichthys nobilis), collected from Poyang Lake, China’s largest shallow lake, and were studied. OCPs were detected with the observed concentrations ranging from 280.67 to 1,006.58 ng/g wet weight (ww) for bighead carp and from 67.28 to 930.06 ng/g ww for silver carp. Composition analysis demonstrated OCPs in both fish were from the same polluted environment, and then, the species-specific bioaccumulation might be mainly due to the different fish age as well as the different feeding habits elucidating from the stable carbon (δ 13C) and nitrogen (δ 15N) isotope analysis. Tissue distribution indicated that dietary intake was the major exposure route of OCPs for both fish and higher accumulation potency of OCPs by the hepatobiliary-related tissues (such as liver, kidney, bile, and heart). The higher metabolic activities of these tissues elucidating from the higher values of δ 15N might be the potential-determined factor responsible for the tissue-specific accumulation. 相似文献
11.
Emissions of CH 4 and N 2O related to private pig farming under a tropical climate in Uvéa Island were studied in this paper. Physicochemical soil parameters such as nitrate, nitrite, ammonium, Kjeldahl nitrogen, total organic carbon, pH and moisture were measured. Gaseous soil emissions as well as physicochemical parameters were compared in two private pig farming strategies encountered on this island on two different soils (calcareous and ferralitic) in order to determine the best pig farming management: in small concrete pens or in large land pens. Ammonium levels were higher in control areas while nitrate and nitrite levels were higher in soils with pig slurry inputs, indicating that nitrification was the predominant process related to N 2O emissions. Nitrate contents in soils near concrete pens were important (≥55 μg N/g) and can thus be a threat for the groundwater. For both pig farming strategies, N 2O and CH 4 fluxes can reach high levels up to 1 mg N/m 2/h and 1 mg C/m 2/h, respectively. CH 4 emissions near concrete pens were very high (≥10.4 mg C/m 2/h). Former land pens converted into agricultural land recover low N 2O emission rates (≤0.03 mg N/m 2/h), and methane uptake dominates. N 2O emissions were related to nitrate content whereas CH 4 emissions were found to be moisture dependent. As a result relating to the physicochemical parameters as well as to the gaseous emissions, we demonstrate that pig farming in large land pens is the best strategy for sustainable family pig breeding in Uvéa Islands and therefore in similar small tropical islands. 相似文献
12.
The Mar Piccolo is a semi-enclosed basin subject to different natural and anthropogenic stressors. In order to better understand plankton dynamics and preferential carbon pathways within the planktonic trophic web, an integrated approach was adopted for the first time by examining all trophic levels (virioplankton, the heterotrophic and phototrophic fractions of pico-, nano- and microplankton, as well as mesozooplankton). Plankton abundance and biomass were investigated during four surveys in the period 2013–2014. Beside unveiling the dynamics of different plankton groups in the Mar Piccolo, the study revealed that high portion of the plankton carbon (C) pool was constituted by small-sized (<2 μm) planktonic fractions. The prevalence of small-sized species within micro- and mesozooplankton communities was observed as well. The succession of planktonic communities was clearly driven by the seasonality, i.e. by the nutrient availability and physical features of the water column. Our hypothesis is that beside the ‘bottom-up’ control and the grazing pressure, inferred from the C pools of different plankton groups, the presence of mussel farms in the Mar Piccolo exerts a profound impact on plankton communities, not only due to the important sequestration of the plankton biomass but also by strongly influencing its structure. 相似文献
14.
Environmental Science and Pollution Research - Optimization of fuel injection strategies can maximize the utilization of ternary fuel by addressing the issues concerning fuel consumption, engine... 相似文献
|