细化搜索
结果 1191-1200 的 4,044
Spatial distribution and seasonal variation of the trace hazardous element contamination in Jakarta Bay, Indonesia 全文
2016
Siregar, Tuti Hartati | Priyanto, Nandang | Putri, Ajeng Kurniasari | Rachmawati, Novalia | Triwibowo, Radestya | Dsikowitzky, Larissa | Schwarzbauer, Jan
The Jakarta Bay Ecosystem is located in the vicinity of the megacity Jakarta, the capital city of Indonesia. Surrounding rivers and canals, carrying solid and fluid waste from households and several industrial areas, flow into the bay. Therefore, the levels of selected trace hazardous elements in water, surface sediments and animal tissues were determined. Samples were collected from two different seasons. The spatial distribution pattern of trace elements in sediment and water as well as the seasonal variation of the contamination were assessed. Quality assessment of sediment using the effects range median (ERM) showed that the concentrations of Hg, Cu and Cr at some stations exceeded the recommended values. Moreover, the concentrations of several trace hazardous elements in the sediments exceeded previously reported toxicity thresholds for benthic species.
显示更多 [+] 显示较少 [-]Tracking pollutant characteristics during haze events at background site Zhongmu, Henan Province, China 全文
2016
Yu, Fei | Yan, Qishe | Jiang, Nan | Su, Fangcheng | Zhang, Leishi | Yin, Shasha | Li, Yang | Zhang, Ruiqin | Chen, Liangfu
Recently, China has faced a large scale air pollution problem not only in urban but also in rural areas. To better understand the occurrence of haze events and properties of particulate matter (PM) in rural area, continuous monitoring of PM and its related characteristics is necessary. Consequently, in this study, a comprehensive observation was performed at a rural site of Zhongmu, Henan Province. The meteorological parameters, physical and chemical properties including number and mass concentration, size resolved and water soluble ions were measured. During the observation period, the highest hourly mass concentration of PM2.5 obtained from Electrical Low Pressure Impactor plus (ELPI+) was 560 μg/m3 on January 5, 2015. The Hybrid Single-Particle Lagrangian Integrated Trajectory model shows that the most polluted day (January 5) was under the influence of static stability meteorological conditions and greatly influenced by the surrounding regional (within 200 km). During new particle formation stage, higher number concentration in nucleation mode (<30 nm) was found. Through the measurement of water-soluble inorganic ions, it was found that Ca2+ was the highest water-soluble inorganic ions in the coarse fraction (PM2.1–10) while SO42−, NO3− and NH4+ were the three major species in the fine fraction (PM2.1). Furthermore, the ratio of [NH4+]/(2[SO42−] + [NO3−]) was higher in fine particulate and [NH4+]/[SO42−] was more than 2 in fine particulate, indicating the presence of both (NH4)2SO4 and NH4NO3 in fine particulate during haze days. The regional transport and to some extent local dust were responsible for haze formation in the observed site.
显示更多 [+] 显示较少 [-]Internal bioerosion in dead and live hard corals in intertidal zone of Hormuz Island (Persian Gulf) 全文
2016
Jafari, Mohammad Ali | Seyfabadi, Jafar | Shokri, Mohammad Reza
Internal macrobioeroders and their erosion rate in three live and dead coral genera (Favia, Platygyra and Porites) from the intertidal zone of the Hormuz Island were studied by collecting five live and five dead colonies from each genus, from which 4mm cross-sections were cut and photographed. Photos were analyzed using the Coral Point Count with Excel extensions. Totally, 9 taxa were identified: four bivalve species, one sponge, three polychaetes, and one barnacle. Bioerosion rate did not significantly differ among the three live corals, but among the dead ones only Porites was significantly more eroded than Favia. Sponge had the highest role in the erosion of the dead Platygyra, while barnacles were the most effective eroding organism in the live Platygyra. Polychaetes, followed by bivalves, were the most destructive bioeroders on the dead and live Porites. Further, none of the bioeroding organisms had selectively chosen either the dead or live Favia.
显示更多 [+] 显示较少 [-]Time series analysis of aerosol optical depth over New Delhi using Box–Jenkins ARIMA modeling approach 全文
2016
Taneja, Kanika | Aḥmad, Shamshād | Kafīl, Aḥmad | Attri, S.D.
The present study focuses on the application of stochastic modeling technique in analyzing the future trends of aerosol optical properties. For this, the Box–Jenkins ARIMA (Autoregressive Integrated Moving Average) model has been used for simulating the monthly average Aerosol Optical Depth (AOD550 nm) retrieved from Terra MODIS (Moderate Resolution Imaging Spectroradiometer) over New Delhi, the urban capital of India. The satellite dataset has been collected for a period of ten years from 2004 to 2014. The analysis of autocorrelation function indicates existence of seasonality in the AOD time series. Several seasonal ARIMA models have been generated and their validation has been verified by assessing various estimation parameters, using the Statistical Package for the Social Sciences (SPSS, version 20). After rigorous evaluation of the selected models, the ARIMA (1,0,0)x(0,1,2)12 is identified as the best fit model w.r.t. measures of goodness-of-fit like Stationary R-square (0.530), R-square (0.674), Root Mean Squared Error (0.128); Mean Absolute Error (0.095); Mean Absolute Percentage Error (16.942); and normalized Bayesian Information Criteria (−3.941). The selected models have been further used to forecast AOD values for the year 2014 at 95% level of confidence. However, the ARIMA (1,0,0)x(2,1,1)12 model is found to have minimum forecasting error, calculated as Mean Percentage Error (0.220). As the difference in BIC of both the models is minimal (0.046), so both the models have been considered as best fit models and utilized for prediction of AOD. Satisfactory results have been obtained using the selected ARIMA models, suggesting that a simplistic modeling technique for determining the future values of AOD is feasible.
显示更多 [+] 显示较少 [-]Oil spill dispersants induce formation of marine snow by phytoplankton-associated bacteria 全文
2016
van Eenennaam, Justine S. | Wei, Yuzhu | Grolle, Katja C.F. | Foekema, Edwin M. | Murk, AlberTinka J.
Unusually large amounts of marine snow, including Extracellular Polymeric Substances (EPS), were formed during the 2010 Deepwater Horizon oil spill. The marine snow settled with oil and clay minerals as an oily sludge layer on the deep sea floor. This study tested the hypothesis that the unprecedented amount of chemical dispersants applied during high phytoplankton densities in the Gulf of Mexico induced high EPS formation. Two marine phytoplankton species (Dunaliella tertiolecta and Phaeodactylum tricornutum) produced EPS within days when exposed to the dispersant Corexit 9500. Phytoplankton-associated bacteria were shown to be responsible for the formation. The EPS consisted of proteins and to lesser extent polysaccharides. This study reveals an unexpected consequence of the presence of phytoplankton. This emphasizes the need to test the action of dispersants under realistic field conditions, which may seriously alter the fate of oil in the environment via increased marine snow formation.
显示更多 [+] 显示较少 [-]Ecological quality assessment in the Eastern Mediterranean combining live and dead molluscan assemblages 全文
2016
Leshno, Yael | Benjamini, Chaim | Edelman-Furstenberg, Yael
The EU directive to quantify ecological quality by deviation from pre-impacted conditions often fails to be implemented because past information is usually incomplete or missing. Molluscan death assemblages, representing long-term accumulation of shells on the sea floor, average out short-term variability and can serve as a baseline for quality assessment. AMBI, Bentix and Shannon–Wiener indices were calculated for live and dead assemblages from polluted and control stations on the highly oligotrophic Levantine shallow shelf of Israel. Bentix successfully tracked deterioration over time, from moderate EcoQS in the dead to poor in the live assemblage. Additional modification of the ecological classification of species by scoring the naturally abundant Corbula gibba as pollution-sensitive improved the utility of the Bentix index in monitoring in this part of the Mediterranean. This adjustment of Bentix, and use of death assemblages for an ecological baseline, should therefore be incorporated in monitoring for compliance with EU directives.
显示更多 [+] 显示较少 [-]Role of environmental particulate matters on corrosion of copper 全文
2016
Saha, D. | Pandya, A. | Singh, J.K. | Paswan, S. | Singh, D.D.N.
Effect of environmental particulate materials on kinetics and mechanism of corrosion of industrial grade copper exposed in different parts of India is investigated. It is observed that the level of particulate materials in the atmosphere has more dominant role than the acidic gases on initiation of corrosion, formation of protective patina on the surface of the exposed samples leading to mitigation of corrosion. The identification of corrosion products formed on the surface of exposed samples by Raman spectroscopy provides very vital information to explain the observed corrosion rate of the metal computed in different environments. Electrochemical anodic polarization of the exposed samples supports the mechanism proposed for accelerating and protective effect on corrosion of the metals exposed in different environments.
显示更多 [+] 显示较少 [-]Assessment of factors enabling halite formation in a marsh in a humid temperate climate (Ajó Marsh, Argentina) 全文
2016
Carol, Eleonora S. | Álvarez, María del Pilar | Borzi, Guido E.
The formation of evaporites associated with the final stages of the precipitation sequence, such as the case of halite, is frequent in marshes in arid areas, but it is not to be expected in those humid climates. This work, by means of the study of the hydrological, climatic and land use conditions, identifies the factors that allow the formation of saline precipitations in a marsh located in a humid climate area. The results obtained show that the exclusion of the marsh as a result of the embankment is the main reason for the presence of halite. It is to be expected that in the future the growth of the embanked marsh areas, together with the climatic and tidal condition tendencies recorded, will favour a higher rate of formation of evaporite salts. The identification of these factors makes it possible to set basic sustainable management guidelines to avoid soil salinisation.
显示更多 [+] 显示较少 [-]Seasonal changes in nutrient limitation and nitrate sources in the green macroalga Ulva lactuca at sites with and without green tides in a northeastern Pacific embayment 全文
2016
Van Alstyne, Kathryn L.
In Penn Cove, ulvoid green algal mats occur annually. To examine seasonal variation in their causes, nitrogen and carbon were measured in Ulva lactuca in May, July, and September and stable nitrogen and oxygen isotope ratios were quantified in U. lactuca, Penn Cove seawater, upwelled water from Saratoga Passage, water near the Skagit River outflow, and effluents from wastewater treatment facilities. Ulvoid growth was nitrogen limited and the sources of nitrogen used by the algae changed during the growing season. Algal nitrogen concentrations were 0.85–4.55% and were highest in September and at sites where algae were abundant. Upwelled waters were the primary nitrogen source for the algae, but anthropogenic sources also contributed to algal growth towards the end of the growing season. This study suggests that small nitrogen inputs can result in crossing a “tipping point”, causing the release of nutrient limitation and localized increases in algal growth.
显示更多 [+] 显示较少 [-]Synoptic weather evolution and climate drivers associated with winter air pollution in New Zealand 全文
2016
Fiddes, S.L. | Pezza, A.B. | Mitchell, T.A. | Kozyniak, K. | Mills, D.
Particulate matter pollution of less than 10 μm in diameter (PM10) is a problem for some regional and urban centres across New Zealand during the winter period when solid fuel (wood and coal) fires are used for home heating. Elevated levels of PM10 concentrations occur during stable atmospheric conditions, when cool air temperatures and low wind speeds allow for a surface inversion to occur and trap PM10. This study examined the relationships between PM10 and local and large-scale synoptic conditions at daily and seasonal scales. Minimum temperature and wind speed were both negatively correlated with PM10 during the winter season, whilst the combination of the two can explain 30–54% of variability in average PM10. Synoptic-scale daily composites of high PM10 days showed the evolution of an anticyclone in the Tasman Sea, with an injection of cool air over New Zealand and persistent south-westerly winds leading to cold and stable conditions on the day of exceedance. Both of these results indicate that there is some potential for predicting days in which atmospheric conditions could favour elevated PM10 concentrations. Furthermore, at the seasonal scale, weaker westerly winds were found to be associated with winters with higher exceedance days, although the relationship is not straightforward. These characteristics can be associated with other, predictable large-scale climate drivers such as the El Niño-Southern Oscillation, and may aid in identifying years in which a higher risk of PM10 pollution events exists.
显示更多 [+] 显示较少 [-]