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241.
The influence of preozonization, coagulation and double layer filtration on formation and removal of mutagenic activity was studied using XAD-8 extracts collected from neutral and acidic solutions and assaying them in the Salmonella typhimurium microsomal assay.Preozonization of surface water produced direct acting frame shift mutagens which were adsorbed on XAD-8 from neutral solutions. This phenomenon was shown to be dependent on the ozone dose applied. Coagulation with different chemicals and subsequent direct filtration partially reduced the mutagenic activity. 相似文献
242.
A statistical correlative study (simple and multiple) between 14 herbicides and insecticides and composition of 51 soil samples has been performed by considering top- and sub-soil horizons, separately. Results point out the suitability of these regression models as a predictive tool to determine quantitatively the adsorption of numerous pesticides in soils mainly the more soluble compounds. 相似文献
243.
Brown DJ Van Overmeire I Goeyens L Denison MS De Vito MJ Clark GC 《Chemosphere》2004,55(11):1509-1518
Brominated flame-retardants (BFRs) are used as additives in plastics to decrease the rate of combustion of these materials, leading to greater consumer safety. As the use of plastics has increased, the production and use of flame-retardants has also grown. Many BFRs are persistent and have been detected in environmental samples, raising concerns about the biological/toxicological risk associated with their use. Most BFRs appear to be non-toxic, however there is still some concern that these compounds, or possible contaminants in BFRs mixtures could interact with cellular receptors. In this study we have examined the interaction of decabromodiphenyl ether, Firemaster BP4A (tetrabromobisphenol A), Firemaster PHT4 (tetrabromophthalic anhydride), hexabromobenzene, pentabromotoluene, decabromobiphenyl, Firemaster BP-6 (2,2′,4,4′,5,5′-hexabromobiphenyl) and possible contaminants of BFR mixtures with the Ah receptor. Receptor binding and activation was examined using the Gel Retardation Assay and increased expression of dioxin responsive genes was detected using the reporter gene based CALUX assay. The results demonstrate the ability of BFRs to activate the AhR signal transduction pathway at moderate to high concentrations as assessed using both assays. AhR-dependent activation by BFRs may be due in part to contaminants present in commercial/technical mixtures. This was suggested by our comparative analysis of Firemaster BP-6 versus its primary component 2,2′,4,4′,5,5′-hexabromobiphenyl. Some technical mixtures of brominated flame-retardants contain brominated biphenyls, dioxins or dibenzofurans as contaminants. When tested in the CALUX assay these compounds were found to be equivalent to, or more active than their chlorinated analogues. Relative effective potency values were determined from dose response curves for these brominated HAHs. 相似文献
244.
A limited number of different foods were analysed for dioxin-like compounds by the CALUX bioassay which is an in vitro luciferase reporter gene assay measuring chemical activation of the aryl hydrocarbon receptor. Sixty-two milk samples were obtained from a surveillance campaign, 34 meat samples and 34 fishery products were purchased from the Belgian market. Bio-analytical and chemo-analytical dioxin toxicity equivalents (TEQ) values of the same milk samples were compared. Spearman's Rank correlation coefficients of 0.72, 0.67, 0.73 were obtained respectively between CALUX-TEQ and PCDD/F-TEQ, DL-PCB-TEQ and PCDD/F+DL-PCB-TEQ. The bioassay limit of detection was 0.1 pg TEQ from 1 g animal lipid, the limit of quantification was 0.4 pg TEQ. The repeatability of the CALUX bioassay (variability of butter fat samples analysed in the same run) showed a coefficient of variation (CV) of 10%, intra laboratory reproducibility based on independent runs of the same butter fat samples showed more variation (CV of 26% for samples above 2 pg TEQ/g lipid). All milk samples with a chemical TEQ value above the current limit value in Belgium showed an elevated CALUX-TEQ concentration, above 6 pg TEQ/g lipid. No false negative results were obtained. Based on the good correlation between CALUX-TEQ and chemically measured TEQ levels, the CALUX bioassay can be recommended as a screening tool for routine measurement of potentially toxic PHAHs in milk samples. Chemical analyses could then largely be restricted to positive samples, in order to identify the nature and to quantify the concentration of the chemicals that give the positive signal. Meat samples showed lower CALUX-TEQ values per gram lipid compared to fish samples. The fish samples showed a wider range of CALUX-TEQ values than the meat samples. 相似文献
245.
Diffusion coefficients (T=23±2 °C) and accessible porosities for HTO, 36Cl− and 125I− were measured on Opalinus Clay (OPA) samples from the Mont Terri Underground Rock Laboratory (URL) using the through-diffusion technique. The direction of transport (diffusion) was perpendicular to bedding. Special cells that allowed the application of confining pressure were designed and constructed. The pressures ranged from 1 to 5 MPa, the latter value simulating the overburden at the Mont Terri URL (about 200 m). The test solution used in the experiments was a synthetic version of the Opalinus Clay pore water, which has Na+ and Cl− as the main components (I=0.42 M).The measured values of the effective diffusion coefficients (De) and rock capacity factors (α) are: De=1.2–1.5×10−11 m2 s−1 and α=0.09–0.11 for HTO, De=4.0–5.5×10−12 m2 s−1 and α=0.05 for 36Cl− and De=3.2–4.6×10−12 m2 s−1 and α=0.07–0.10 for 125I−. For non-sorbing tracers (HTO, 36Cl) the rock capacity factor α is equal to the diffusion-accessible porosity . The experimental results showed that pressure only had a small effect on the value of the diffusion coefficients. Increasing the pressure from 1 to 5 MPa resulted in a decrease of the diffusion coefficient of 17% for HTO, 28% for 36Cl− and 30% for 125I−. Moreover, the diffusion coefficients for 36Cl− and 125I− are smaller than for HTO, which is consistent with an effect arising from anion exclusion.The diffusion coefficients of HTO and 125I− measured in this study are in good agreement with recent measurements at three other laboratories performed within the framework of a laboratory comparison exercise. The values of the diffusion-accessible porosities show a larger degree of scatter. 相似文献
246.
G.P.J. Draaijers E.P. Van Leeuwen P.G.H. De Jong J.W. Erisman 《Atmospheric environment (Oxford, England : 1994)》1997,31(24):4139-4157
Deposition of base cations (Na+, Mg2+, Ca2+, K+) in Europe was mapped for 1989 with a spatial resolution of 10 x 20 km using the so-called inferential modeling technique. Deposition fields resembled the geographic variability of sources, land-use and climate. Dry deposition constituted on average 45% of the total base cation deposition in Europe. Modeled deposition estimates compared reasonably well with deposition estimates derived from throughfall and bulk-precipitation measurements made at 174 sites scattered over Europe. Using error propagation, the random and systematic error in total deposition for an average grid cell of 10 x 20 km was estimated to equal 35–50% and 25–40%, respectively. Within individual grids a relatively large variability in deposition is expected. 相似文献
247.
Discrimination of factors influencing biota of a stream receiving multiple-source perturbations 总被引:1,自引:0,他引:1
Van Hassel JH Cherry DS Hendricks JC Specht WL 《Environmental pollution (Barking, Essex : 1987)》1988,55(4):271-287
Blaine Creek is a fifth-order stream located in eastern Kentucky that has been subject to contamination by oil brines, surface mining, and a coal fly ash settling pond discharge. Toxicity tests, effluent and receiving water chemical monitoring, and Blaine Creek benthic sampling were used to evaluate the effect of the ash pond effluent on the creek. Reproductive impairment of Ceriodaphnia was demonstrated at effluent concentrations ranging from 30 to 100%, but no instream impact on benthic invertebrates could be found at effluent flows that provided up to 65% of the creek's discharge. Correlation and regression analysis of physicochemical versus benthic monitoring data indicated that upstream oil brine contamination and scouring of the creek's predominately shifting sand substrate during rainfall events were the primary factors affecting the benthic fauna, and appeared to override potential effects from other sources. These results demonstrated the value of integrated field/laboratory investigations for effluent impact assessments. 相似文献
248.
Van Stempvoort DR Lesage S Novakowski KS Millar K Brown S Lawrence JR 《Journal of contaminant hydrology》2002,54(3-4):249-276
The enhanced solubility of petroleum-derived compounds in humic acid solutions is the basis for a new groundwater remediation technology. In this unique pilot-scale test, a stationary contaminant source consisting of diesel fuel was placed below the water table in a model sand aquifer (1.2 x 5.5 x 1.8-m deep) and flushed with water at a flow rate of 2 cm/h over 5 years. At 51 days, laboratory grade humic acid was added to the water and maintained at a level of approximately 0.8 g/l. The addition of humic acid had only a small impact on the aqueous transport of the BTEX components, which were rapidly dissolved from the diesel, but had a large effect on the flushing of PAHs, including methylated naphthalenes (MNs). Binding to aqueous humic acid enhanced the solubilization of MNs two- to tenfold. During aqueous transport, biodegradation of the BTEX and PAHs occurred, limiting the lateral and longitudinal extent of the diesel contaminant plume in the model aquifer. It appears that through enhanced solubilization, the overall biodegradation rate of the MNs was increased. As the various MNs were depleted from the diesel source, the MN plume shrank and then disappeared. 相似文献
249.
ABSTRACT The signing of Colombia’s peace agreement in 2016 signaled the end of a decades-long war between the government and the FARC (Las Fuerzas Armadas Revolucionarias de Colombia), but also an emerging assault against the country’s forests. This article aims to understand the interactions between forests and peace. In doing so, it traces landscape transformations of deforestation and possibilities for making landscapes livable in the midst of disturbance. Drawing on field research, including interviews and participant observation carried out in Colombia from 2016 to 2018, it reveals how deforestation is driven by ongoing colonization and land grabbing, mostly dedicated to extensive cattle ranching, coca cultivation, and campesinos’ transition to ‘licit’ agricultural alternatives. The article also shows how emerging coordination among farmers and forests following forest disturbance contributes to an interpretation of peace in which forests are integral. The article concludes with a call to incorporate forests in the construction of peace. 相似文献
250.
Effect of environmental factors on byssal thread formation 总被引:1,自引:0,他引:1
W. Van Winkle Jr. 《Marine Biology》1970,7(2):143-148
The effects of various factors on byssal thread formation have been examined in the laboratory using Modiolus demissus and Mytilus edulis. With M. demissus thread formation (threads/mussel/h0 and proportion of mussels forming threads decreased with increasing size; prior exposure to air enhanced subsequent thread formation; mechanical agitation reduced thread formation. In addition, low salinity acclimated mussels adapted more rapidly to 32 ppt than high salinity acclimated mussels did to 16 ppt; threads were not formed in the absence of calcium and/or magnesium; and there was no reduction in thread formation at temperatures as high as 27° to 28°C. M. edulis died and thread formation approached zero at temperatures exceeding 26°C. 相似文献