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Результаты 81-90 из 1,310
Persistent organic pollutant in a fish community of a sub-alpine lake Полный текст
2011
Villa, Sara | Bizzotto, Elisa Chiara | Vighi, M.
This study investigated the presence of organochlorine pollutants in abiotic and biotic samples from Lake Como (Italy). DDTs and PCBs were found to be the major contaminants, ranging from 0.04 to 4.25 and from 0.25 to 40.8 μg/g lipid respectively. Evidence of biomagnification according to the trophic role of the investigated organisms was highlighted by means of Stable Isotope Analysis. A Trophic Magnification Factor (TMF) was calculated for the chemicals of interest and the applicability of the method for global use was confirmed. Statistically significant correlation has been found between the calculated trophic level and the concentrations of more lipophilic compounds, while for the less lipophilic (e.g., HCH, 3CBs) the relationship is no statistically significant and the TMF is close to 1. The role of the foraging area in affecting PCB and DDT concentrations within aquatic ecosystems has been highlighted by a Principal Component Analysis (PCA).
Показать больше [+] Меньше [-]The performance of passive flow monitors and phosphate accumulating passive samplers when exposed to pulses in external water flow rate and/or external phosphate concentrations Полный текст
2011
O’Brien, Dominique | Hawker, Darryl | Shaw, Melanie | Mueller, Jochen F.
Passive samplers are typically calibrated under constant flow and concentration conditions. This study assessed whether concentration and/or flow pulses could be integrated using a phosphate passive sampler (P-sampler). Assessment involved three 21-day experiments featuring a pulse in flow rate, a pulse of filterable reactive phosphate (FRP) concentration and a simultaneous concentration and flow pulse. FRP concentrations were also determined by parallel grab sampling and the P-sampler calibrated with passive flow monitors (PFMs) and direct measurement of flow rates. The mass lost from the PFM over the deployment periods predicted water velocity to within 5.1, 0.48 and 7.1% when exposed to a flow rate pulse (7.5–50 cm s⁻¹), concentration pulse (5–100 μg P L⁻¹), or both simultaneously. For the P-sampler, good agreement was observed between the grab and passive measurements of FRP concentration when exposed to a pulse in flow (6% overestimation) or concentration (2% underestimation).
Показать больше [+] Меньше [-]Changes in photosynthesis, mesophyll conductance to CO₂, and isoprenoid emissions in Populus nigra plants exposed to excess nickel Полный текст
2011
Velikova, Violeta | Tsonev, Tsonko | Loreto, Francesco | Centritto, Mauro
Poplar (Populus nigra) plants were grown hydroponically with 30 and 200 μM Ni (Ni₃₀ and Ni₂₀₀). Photosynthesis limitations and isoprenoid emissions were investigated in two leaf types (mature and developing). Ni stress significantly decreased photosynthesis, and this effect depended on the leaf Ni content, which was lower in mature than in developing leaves. The main limitations to photosynthesis were attributed to mesophyll conductance and metabolism impairment. In Ni-stressed developing leaves, isoprene emission was significantly stimulated. We attribute such stimulation to the lower chloroplastic [CO₂] than in control leaves. However chloroplastic [CO₂] did not control isoprene emission in mature leaves. Ni stress induced the emission of cis-β-ocimene in mature leaves, and of linalool in both leaf types. Induced biosynthesis and emission of isoprenoids reveal the onset of antioxidant processes that may also contribute to reduce Ni stress, especially in mature poplar leaves.
Показать больше [+] Меньше [-]Triclosan affects the microbial community in simulated sewage-drain-field soil and slows down xenobiotic degradation Полный текст
2011
Svenningsen, Hanne | Henriksen, Trine | Priemé, Anders | Johnsen, Anders R.
Effects of the common antibacterial agent triclosan on microbial communities and degradation of domestic xenobiotics were studied in simulated sewage-drain-field soil. Cultivable microbial populations decreased 22-fold in the presence of 4 mg kg⁻¹ of triclosan, and triclosan-resistant Pseudomonas strains were strongly enriched. Exposure to triclosan also changed the general metabolic profile (Ecoplate substrate profiling) and the general profile (T-RFLP) of the microbial community. Triclosan degradation was slow at all concentrations tested (0.33–81 mg kg⁻¹) during 50-days of incubation. Mineralization experiments (¹⁴C-tracers) and chemical analyses (LC–MS/MS) showed that the persistence of a linear alkylbenzene sulfonate (LAS) and a common analgesic (ibuprofen) increased with increasing triclosan concentrations (0.16–100 mg kg⁻¹). The largest effect was seen for LAS mineralization which was severely reduced by 0.16 mg kg⁻¹ of triclosan. Our findings indicate that environmentally realistic concentrations of triclosan may affect the efficiency of biodegradation in percolation systems.
Показать больше [+] Меньше [-]Implementation of airborne trace element monitoring with devitalised transplants of Hypnum cupressiforme Hedw.: Assessment of temporal trends and element contribution by vehicular traffic in Naples city Полный текст
2011
Adamo, P. | Giordano, S. | Sforza, A. | Bargagli, R.
A biomonitoring of airborne trace elements was performed in 2006 in Naples urban area through the exposure of devitalised Hypnum cupressiforme for 10 weeks at 4m height. In one street, the moss was exposed at different heights to assess vertical gradients of element concentrations. Results were compared with those of a 1999 biosurvey. Correlations among Al, Fe and Ti suggested a soil particles contribution to element uptake. Cu, Mo and Fe were related with traffic flows. Long-range transport contributed to Cd, Cu and Mo accumulation in moss at higher heights. As in 1999, the airborne element load was higher in coastal sites, more affected by marine aerosols and traffic. In all sites, contents of Cd, Fe, Pb, Ni and V in moss were remarkably lower than in 1999, indicating a positive effect of actions set up in recent years to reduce the traffic and to improve the city air quality.
Показать больше [+] Меньше [-]Date palm (Phoenix dactylifera L.) leaves as biomonitors of atmospheric metal pollution in arid and semi-arid environments Полный текст
2011
Al-Khashman, Omar Ali | Al-Muhtaseb, Ala’a H. | Ibrahim, Khalid A.
The leaves of date palms were evaluated as a possible biomonitor of heavy metal contamination in Ma’an city, Jordan. Concentrations of (Fe), (Pb), (Zn), (Cu), (Ni), and (Cr) were determined in washed and unwashed leaves and soil samples collected from different sites with different degrees of metal contamination (urban, suburban, industrial, highway and rural sites); separate leaves were taken from outside the city to be used as a control sample. Samples collected from industrial sites were found to have high concentrations of all metals except those of Cu, Ni and Pb, which were found at high levels in the highway site samples which is associated with the road traffic. The difference between unwashed and washed samples showed that metal pollutants exist as contaminants, particularly Pb, Zn and Ni, which varied in concentration, depending on the source of the metal.
Показать больше [+] Меньше [-]Photochemical processing of aldrin and dieldrin in frozen aqueous solutions under arctic field conditions Полный текст
2011
Rowland, Glenn A. | Bausch, Alexandra R. | Grannas, Amanda M.
Organochlorine (OC) contaminants are transported to the Polar Regions, where they have the potential to bioaccumulate, presenting a threat to the health of wildlife and indigenous communities. They deposit onto snowpack during winter, and accumulate until spring, when they experience prolonged solar irradiation until snowmelt occurs. Photochemical degradation rates for aldrin and dieldrin, in frozen aqueous solution made from MilliQ water, 500 μM hydrogen peroxide solution or locally-collected melted snow were measured in a field campaign near Barrow, AK, during spring–summer 2008. Significant photoprocessing of both pesticides occurs; the reactions depend on temperature, depth within the snowpack and whether the predominant phase is ice or liquid water. The effect of species present in natural snowpack is comparable to 500 μM hydrogen peroxide, pointing to the potential significance of snowpack-mediated reactions. Aldrin samples frozen at near 0 °C were more reactive than comparable liquid samples, implying that the microenvironments experienced on frozen ice surfaces are an important consideration.
Показать больше [+] Меньше [-]Road deicing salt irreversibly disrupts osmoregulation of salamander egg clutches Полный текст
2011
Karraker, Nancy E. | Gibbs, James P.
It has been postulated that road deicing salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of deicing salts in wetlands with extremely high chloride concentrations.
Показать больше [+] Меньше [-]National survey of the levels of persistent organochlorine pesticides in the breast milk of mothers in China Полный текст
2011
Zhou, Pingping | Wu, Yongning | Yin, Shian | Li, Jingguang | Zhao, Yunfeng | Zhang, Lei | Chen, Huijing | Liu, Yinping | Yang, Xin | Li, Xiaowei
The occurrence of persistent organochlorine pesticides (OCPs) in breast milk samples collected from mothers from twelve provinces in mainland China was investigated. Dichlorodiphenyltrichloroethanes (DDTs) were the most prevalent agent, followed by HCHs and HCB, whereas levels of chlordane compounds, drins and mirex were lower. The relatively lower DDE/DDT ratio in the Fujian rural area suggested more recent exposure to DDT than in other areas. The mean level of DDTs in breast milk from the southern China was higher than those from northern China (p < 0.05). A positive correlation was observed between concentration of DDTs in human milk and consumption of animal-origin food, suggesting that this parameter could play an important part in influencing OCPs burdens in lactating women. The mean estimated daily intakes of different OCPs for breastfed infants were lower than the tolerable daily intake.
Показать больше [+] Меньше [-]Accumulation of ¹⁴C-trinitrotoluene and related nonextractable (bound) residues in Eisenia fetida Полный текст
2011
Belden, Jason B. | Lotufo, Guillerme R. | Chambliss, C Kevin | Fisher, Jonathan C. | Johnson, Dave R. | Boyd, Robert E. | Sims, Jerre G.
To determine if trinitrotoluene (TNT) forms nonextractable residues in earthworms and to measure the relative degree of accumulation as compared to TNT and its deaminated metabolites, Eisenia fetida was exposed to ¹⁴C-TNT using dermal contact to filter paper or exposure to soil. Nonextractable residues made up 32–68% of total body burden depending on exposure media and depuration time. Parent TNT accounted for less than 3% of radioactivity, while ADNTs accounted for 7–38%. Elimination half-lives were 61–120h for TNT, ADNTs, and DANTs, which was significantly lower than the half-lives found for nonextractable residues, 201–240h. However, over 80% of the nonextractable residue was solubilized using weak acid (pH 2). Based on our findings that TNT accumulation occurs primarily as nonextractable residues, which have a longer half-life, and that nonextractable residues can be solubilized, we propose that nonextractable residues could be used as a selective biomarker for assessing TNT contamination.
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