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Результаты 1451-1460 из 4,309
Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in surface sediments from the Nantong Coast, China Полный текст
2017
Liu, Na | Li, Xian | Zhang, Daolai | Liu, Qiang | Xiang, Lihui | Liu, Ke | Yan, Dongyun | Li, Yue
The distribution, sources, and ecological risk assessment of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from the Nantong coast in China were investigated. The results indicated that the total concentrations of the 16 PAHs in the surface sediments from the study area ranged from 1.4 to 87.1ngg−1 dw (mean value 19.9ngg−1 dw), which were generally low compared to the adjacent offshore area and other coastal zones around the world. The selected PAH ratios and the principal components analysis for each site showed that petroleum combustion and petrogenic pollution (mainly caused by petroleum spills) were the dominant PAHs sources in the surface sediments of the coast. The ecological risk assessment indicated that most of the individual PAHs had few negative effects in this area.
Показать больше [+] Меньше [-]Evaluation of sediment contamination by monoaromatic hydrocarbons in the coastal lagoons of Gulf of Saros, NE Aegean Sea Полный текст
2017
Ünlü, Selma | Alpar, Bedri
The concentrations and distribution of monoaromatic hydrocarbons (benzene, toluene, ethyl benzene and the sum of m-, p- and o-, xylenes) were determined in the sediments of coastal lagoons of the Gulf of Saros, using a static headspace GC–MS. The total concentrations of BTEX compounds ranged from 368.5 to below detection limit 0.6μgkg−1 dw, with a mean value of 61.5μgkg−1 dw. The light aromatic fraction of m-, p-xylene was the most abundant compound (57.1% in average), and followed by toluene (38.1%)>ethylbenzene (4.1%)>o-xylene (2.5%)>benzene (1.1%). The factor analysis indicated that the levels and distribution of BTEX compounds depend on the type of contaminant source (mobile/point), absorbance of compounds in sediment, and mobility of benzene compound and degradation processes. Point sources are mainly related to agricultural facilities and port activities while the dispersion of compounds are related with their solubility, volatility and effect of sea/saline waters on lagoons.
Показать больше [+] Меньше [-]Characterization of Enterococcus species isolated from marine recreational waters by MALDI-TOF MS and Rapid ID API® 20 Strep system Полный текст
2017
Christ, Ana Paula Guarnieri | Ramos, Solange Rodrigues | Cayô, Rodrigo | Gales, Ana Cristina | Hachich, Elayse Maria | Sato, Maria Inês Zanoli
MALDI-TOF Mass Spectrometry Biotyping has proven to be a reliable method for identifying bacteria at the species level based on the analysis of the ribosomal proteins mass fingerprint. We evaluate the usefulness of this method to identify Enterococcus species isolated from marine recreational water at Brazilian beaches. A total of 127 Enterococcus spp. isolates were identified to species level by bioMérieux's API® 20 Strep and MALDI-TOF systems. The biochemical test identified 117/127 isolates (92%), whereas MALDI identified 100% of the isolates, with an agreement of 63% between the methods. The 16S rRNA gene sequencing of isolates with discrepant results showed that MALDI-TOF and API® correctly identified 74% and 11% of these isolates, respectively. This discrepancy probably relies on the bias of the API® has to identify clinical isolates. MALDI-TOF proved to be a feasible approach for identifying Enterococcus from environmental matrices increasing the rapidness and accuracy of results.
Показать больше [+] Меньше [-]The revealed preferences of Baltic Sea governments: Goals, policy instruments, and implementation of nutrient abatement measures Полный текст
2017
Elofsson, Katarina | von Brömssen, Claudia
Nitrogen and phosphorus loads are considered a major reason for the eutrophication of the Baltic Sea. Until now, most of the abatement has been made at point sources while the implementation of policies for nonpoint sources has not led to equally large reductions in emissions. The purpose of this study is to investigate the determinants of how nutrient abatement measures are implemented by countries in the agricultural sector of the Baltic Sea region. We investigate how goal setting, policy instrument choice, and the level of implementation is determined by characteristics of the abatement measure as well as socio-economic characteristics of the country where it is implemented. Econometric analysis of a cross-sectional data set suggests that income, institutional capacity, and economies of scope in abatement and enforcement are important determinants of policies developed and their implementation.
Показать больше [+] Меньше [-]Performance and bacterial community structure of a 10-years old constructed mangrove wetland Полный текст
2017
Tian, Tingting | Tam, Nora F.Y. | Zan, Qijie | Cheung, S.G. | Shin, Paul K.S. | Wong, Y.S. | Zhang, Li | Chen, Zhanghe
Constructed mangrove wetland has been used for wastewater treatment but its long-term performance has not been reported. One-year monitoring of a 10-years old horizontal subsurface-flow constructed mangrove wetland consisting of three belts, two with mangrove plants and one without, revealed that the system maintained high and stable removal percentages of organic matter and nutrients, and planted belts performed better than unplanted control. Substrates in belts planted with Aegiceras corniculatum or Kandelia obovata had higher abundance of ammonifiers, nitrifiers and denitrifiers but lower total heterotrophic bacteria than unplanted substrate. Denaturing gradient gel electrophoresis showed that microbial diversity in planted substrate was significantly lower than that in unplanted one. The bacteria in substrates, irrespective to belts, were phylogenetically related to Proteobacteria (most dominant), Acidobacteria, Firmicutes, Nitrospirae, Gemmatimonadetes, Chloroflexi and Cyanobacteria. The steady performance of this 10-year old constructed mangrove wetland was affected by the abundance and diversity of bacterial community in substrate.
Показать больше [+] Меньше [-]Spatiotemporal variations in metal accumulation, RNA/DNA ratio and energy reserve in Perna viridis transplanted along a marine pollution gradient in Hong Kong Полный текст
2017
Yeung, Jamius W.Y. | Zhou, Guang-Jie | Leung, Kenneth M.Y.
We examined spatiotemporal variations of metal levels and three growth related biomarkers, i.e., RNA/DNA ratio (RD), total energy reserve (Et) and condition index (CI), in green-lipped mussels Perna viridis transplanted into five locations along a pollution gradient in the marine environment of Hong Kong over 120days of deployment. There were significant differences in metal levels and biomarker responses among the five sites and six time points. Mussels in two clean sites displayed better CI and significantly lower levels of Ag, Cu, Pb and Zn in their tissues than the other sites. Temporal patterns of RD in P. viridis were found to be site-specific. Across all sites, Et decreased in P. viridis over the deployment period, though the rate of decrease varied significantly among the sites. Therefore, temporal variation of biomarkers should be taken to consideration in mussel-watch programs because such information can help discriminate pollution-induced change from natural variation.
Показать больше [+] Меньше [-]A pilot study of different materials applied for active sampling of gaseous oxidized mercury in the atmospheric air Полный текст
2017
Urba, A. | Valiulis, D. | Šarlauskas, J. | Kvietkus, K. | Šakalys, J. | Selskis, A.
Samplers made with different materials were tested for the quantitative collection and recovery of mercury halides from the atmospheric air. The tested adsorbent materials included zirconia (ZrO2), titania (TiO2), melted SiO2 (quartz wool) and potassium chloride (KCl). Different processes affecting the sampler efficiency were investigated specifically: breakthrough during sampling because of the surface passivation and loss of already collected mercury halides due to spontaneous reduction or due to the reaction with ozone. Reduction of mercury because of reaction with the atmospheric ozone appeared to be the major cause of the sample loss and it was inherent in all tested materials at a comparable extent. We hypothesized the zirconia layer covered on a ceramic substrate (patented) to be less sensitive to the ozone-caused reduction, inert to gaseous elemental mercury and completely insensitive to atmospheric humidity. In addition, zirconia samplers were highly resistant to heating and they could be used for multiple adsorption/desorption cycles avoiding degradation in the atmospheric air. Key results of the zirconia sampler tests with mercury halides were: the collection efficiency of >98%; reduction with 50 ppb ozone in the first 4 min of exposition to the atmospheric air ─ 6% ±1%; spontaneous reduction at 50 °C in the first 4 min after spiking ─ <0.6%. Along with the above experimental results, some insights into the possible mechanism of interaction of ozone with mercury halides have been provided.
Показать больше [+] Меньше [-]Temporal and spatial variability of ground level atmospheric methane concentrations in the Ebro River Delta Полный текст
2017
Àgueda, A. (Alba) | Grossi, Claudia | Pastor, Elsa | Rioja, Eva | Sánchez-García, Laura | Batet, Òscar | Curcoll, Roger | Ealo, Marina | Nofuentes, Manel | Occhipinti, Paola | Rodó, Xavier | Morguí, Josep-Anton
Deltas provide many worthy ecosystem services. Yet, delta basins are quite vulnerable, especially in the face of climate change, which can affect the outcome of both agriculture and biodiversity. Moreover, rice paddy cultivation is well known to contribute with strong emissions of greenhouse gases (GHGs), such as methane (CH4). Thus, knowing the atmospheric variability of CH4 in relation to the different stages of the rice culture cycle could help to improve GHGs' mitigation strategies in deltas.The Ebro River Delta, in the northwestern Mediterranean basin, forms part of the largest Spanish river basin and is mainly covered by rice fields. In this study, for the first time, ground level (40 cm a.g.l.) atmospheric CH4 concentrations have been monitored in this area, through twenty-seven car mobile transects, over the course of one year. Seasonal, diurnal and spatial variability of CH4 concentrations were studied to identify its relationship with rice cultivation, meteorological conditions and land-use distribution.With regard to seasonal variability, autumn transects showed the highest mean values for atmospheric CH4 (2.466 ppm) when dead rice straw is mixed with the sediment, and weed growth is prevented. Spring and summer measurements gave the highest mean CH4 values at dawn (1.897–3.544 ppm), whereas autumn and winter produced the mean values after sunset (2.148–2.930 ppm). Spatial differences were accounted for by proximity to urban areas, presence of shallow water storage structures, and distance to seawater.
Показать больше [+] Меньше [-]Polybrominated diphenyl ethers (PBDEs) and alternative flame retardants (NFRs) in indoor and outdoor air and indoor dust from Istanbul-Turkey: Levels and an assessment of human exposure Полный текст
2017
Kurt-Karakus, Perihan Binnur | Alegria, Henry | Jantunen, Liisa | Birgul, Askin | Topcu, Aslinur | Jones, K. C. (Kevin C.) | Turgut, Cafer
Levels of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NFRs) were measured in ambient outdoor air, indoor air and indoor dust collected in homes and offices at urban, semi-urban and rural locations in Istanbul, Turkey. Indoor air levels of Σ12PBDEs in homes and offices ranged from 36 to 730 pg/m3 and 160 to 10 100 pg/m3, respectively, while levels of Σ12NFRs ranged from 180 to 7600 pg/m3 and 180 to 42 400 pg/m3, respectively. Outdoor air levels ranged from 110 to 620 pg/m3 for Σ12PBDEs and 750 to 2800 pg/m3 for Σ12NFRs. I/O ratios that are greater than 1 suggest that air concentrations detected in indoor environments are mainly from indoor sources. Indoor dust levels in homes and offices of Σ12PBDEs ranged from 400 to 12 500 ng/g and 330 to 32 200 ng/g respectively and levels of Σ12NFRs ranged from 320 to 31 400 ng/g and 910 to 97 900 ng/g, respectively. The I/O ratios >1 for PBDEs and NFRs may indicate that emissions of these chemicals detected in homes and offices are mainly from indoor sources. Due to childrens' frequent hand-to-mouth behaviour, lower body weight and increased dust ingestion rate compared to adults, exposure rates to target chemicals for children were greater than those of adults. Based on median concentrations of chemicals of interest in dust and air samples from Istanbul, we estimate that exposure rates of children to PBDEs and NFRs are up to 160 times higher compared to adults but none of the estimated exposure rates results for children or adults were than the recommended daily oral reference dose values of certain analytes.
Показать больше [+] Меньше [-]Nitrogen extraction potential of wild and cultured bivalves harvested from nearshore waters of Cape Cod, USA Полный текст
2017
Reitsma, Joshua | Murphy, Diane C. | Archer, Abigail F. | York, Richard H.
As nitrogen entering coastal waters continues to be an issue, much attention has been generated to identify potential options that may help alleviate this stressor to estuaries, including the propagation of bivalves to remove excess nitrogen. Oysters (Crassostrea virginica) and quahogs (Mercenaria mercenaria) from numerous Cape Cod, MA, (USA) sources were analyzed for nitrogen content stored in tissues that would represent a net removal of nitrogen from a water body if harvested. Results showed local oysters average 0.69% nitrogen by total dry weight (mean 0.28gN/animal) and quahogs average 0.67% nitrogen by total dry weight (mean 0.22gN/animal); however, these values did vary by season and to a lesser extent by location or grow-out method. The differences in nitrogen content were largely related to the mass of shell or soft tissue. Nitrogen isotope data indicate shellfish from certain water bodies in the region are incorporating significant amounts of nitrogen from anthropogenic sources.
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