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Resultados 1-10 de 18
MODIS derived fire characteristics and aerosol optical depth variations during the agricultural residue burning season, north India
2011
Vadrevu, Krishna Prasad | Ellicott, Evan | Badarinath, K.V.S. | Vermote, Eric
Agricultural residue burning is one of the major causes of greenhouse gas emissions and aerosols in the Indo-Ganges region. In this study, we characterize the fire intensity, seasonality, variability, fire radiative energy (FRE) and aerosol optical depth (AOD) variations during the agricultural residue burning season using MODIS data. Fire counts exhibited significant bi-modal activity, with peak occurrences during April–May and October–November corresponding to wheat and rice residue burning episodes. The FRE variations coincided with the amount of residues burnt. The mean AOD (2003–2008) was 0.60 with 0.87 (+1σ) and 0.32 (−1σ). The increased AOD during the winter coincided well with the fire counts during rice residue burning season. In contrast, the AOD-fire signal was weak during the summer wheat residue burning and attributed to dust and fossil fuel combustion. Our results highlight the need for ‘full accounting of GHG’s and aerosols’, for addressing the air quality in the study area.
Mostrar más [+] Menos [-]Seasonal variation and source estimation of organic compounds in urban aerosol of Augsburg, Germany
2011
Pietrogrande, Maria Chiara | Abbaszade, Gülcin | Schnelle-Kreis, Jürgen | Bacco, Dimitri | Mercuriali, Mattia | Zimmermann, Ralf
This study reports a general assessment of the organic composition of the PM₂.₅ samples collected in the city of Augsburg, Germany in a summer (August–September 2007) and a winter (February–March 2008) campaign of 36 and 30 days, respectively. The samples were directly submitted to in-situ derivatisation thermal desorption gas chromatography coupled with time of flight mass spectrometry (IDTD–GC–TOFMS) to simultaneously determine the concentrations of many classes of molecular markers, such as n-alkanes, iso- and anteiso-alkanes, polycyclic aromatic hydrocarbons (PAHs), oxidized PAHs, n-alkanoic acids, alcohols, saccharides and others. The PCA analysis of the data identified the contributions of three emission sources, i.e., combustion sources, including fossil fuel emissions and biomass burning, vegetative detritus, and oxidized PAHs. The PM chemical composition shows seasonal trend: winter is characterized by high contribution of petroleum/wood combustion while the vegetative component and atmospheric photochemical reactions are predominant in the hot season.
Mostrar más [+] Menos [-]Atmospheric deposition, retention, and stream export of dioxins and PCBs in a pristine boreal catchment
2011
Bergknut, Magnus | Laudon, Hjalmar | Jansson, Stina | Larsson, Anna | Gocht, Tilman | Wiberg, Karin
The mass-balance between diffuse atmospheric deposition of organic pollutants, amount of pollutants retained by the terrestrial environment, and levels of pollutants released to surface stream waters was studied in a pristine northern boreal catchment. This was done by comparing the input of atmospheric deposition of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and PCBs with the amounts exported to surface waters. Two types of deposition samplers were used, equipped with a glass fibre thimble and an Amberlite sampler respectively. The measured fluxes showed clear seasonality, with most of the input and export occurring during winter and spring flood, respectively. The mass balance calculations indicates that the boreal landscape is an effective sink for PCDD/Fs and PCBs, as 96.0–99.9 % of received bulk deposition was retained, suggesting that organic pollutants will continue to impact stream water in the region for an extended period of time.
Mostrar más [+] Menos [-]Photochemical processing of aldrin and dieldrin in frozen aqueous solutions under arctic field conditions
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.
Mostrar más [+] Menos [-]How seasonality affects the flow of estrogens and their conjugates in one of Japan’s most populous catchments
2011
Kumar, Vimal | Nakada, Norihide | Yamashita, Naoyuki | Johnson, Andrew C. | Tanaka, Hiroaki
A detailed study of the free and conjugated estrogen load discharged by the eight major sewage treatment plants into the Yodo River basin, Japan was carried out. Sampling campaigns were focused on the winter and autumn seasons from 2005 to 2008 and the free estrogens estrone(E1), 17β-estradiol(E2), estriol(E3), 17α-ethynylestradiol(EE2) as well as their conjugated (sulfate and glucuronide) forms. For both sewage effluent and river water E2 and E1 concentrations were greatest during the winter period (December–March). This coincides with the period of lowest rainfall and lowest temperatures in Japan. E1 was the dominant estrogenic component in effluent (means of 10–50 ng/L) followed by E2 (means of 0.5–3 ng/L). The estrogen sulfate conjugates were found intermittently in the 0.5–1.7 ng/L concentration range in the sewage effluents. The greatest estrogen exposure was found to be in the Katsura River tributary which exceeded 1 ng/L E2-equivalents during the winter period.
Mostrar más [+] Menos [-]Light-induced bird strikes on vessels in Southwest Greenland
2011
Merkel, Flemming Ravn | Johansen, Kasper Lambert
Light-induced bird strikes are known to occur when vessels navigate during darkness in icy waters using powerful searchlight. In Southwest Greenland, which is important internationally for wintering seabirds, we collected reports of incidents of bird strikes over 2–3 winters (2006–2009) from navy vessels, cargo vessels and trawlers (total n=19). Forty-one incidents were reported: mainly close to land (<4km, 78%), but one as far offshore as 205km. Up to 88 birds were reported killed in a single incident. All occurred between 5p.m. and 6a.m. and significantly more birds were involved when visibility was poor (snow) rather than moderate or good. Among five seabird species reported, the common eider (Somateria mollissima) accounted for 95% of the bird casualties. Based on spatial analyses of data on vessel traffic intensity and common eider density we are able to predict areas with high risk of bird strikes in Southwest Greenland.
Mostrar más [+] Menos [-]The effect of thermal pollution on benthic foraminiferal assemblages in the Mediterranean shoreface adjacent to Hadera power plant (Israel)
2011
Arieli, Ruthie Nina | Almogi-Labin, Ahuva | Abramovich, Sigal | Herut, Barak
The thermal pollution patch of Hadera power plant was used as a natural laboratory to evaluate the potential long-term effects of rise in Eastern Mediterranean SST on living benthic foraminifera. Their sensitivity to environmental changes makes foraminifera ideal for this study. Ten monthly sampling campaigns were performed in four stations located along a temperature gradient up to 10°C from the discharge site of heated seawater to a control station. The SST along this transect varied between 25/18°C in winter and 36/31°C in summer. A significant negative correlation was found between SST in all stations and benthic foraminiferal abundance, species richness and diversity. The total foraminiferal abundance and species richness was particularly low at the thermally polluted stations especially during summer when SST exceeded 30°C, but also throughout the entire year. This indicates that thermal pollution has a detrimental effect on benthic foraminifera, irrelevant to the natural seasonal changes in SST.
Mostrar más [+] Menos [-]Seabirds and chronic oil pollution: Self-cleaning properties of gulls, Laridae, as revealed from colour-ring sightings
2011
(C.J.) Camphuysen, Kees
Mystery oil spills off the Dutch coast affected colonial, adult Lesser Black-backed Gulls prior to and within the breeding season. From colour-ringed individuals, it was demonstrated that most oiled birds survived and were clean within a few weeks and often bred successfully. Further evidence of self-cleaning properties of Larus-gulls is provided from a long-term colour-ringing project (1984–2009). In total 46 birds were reported ‘oiled’, two died, but the majority cleaned itself and survived for up to 20years after being oiled. From colour-ring data and 30years of beached bird surveys (1980–2010) it is demonstrated that the effects of chronic oil pollution is larger in winter than in summer; a reflection of seasonal differences in exposure and environmental conditions. The self-cleaning properties of gulls are such that long-term survival is not necessarily jeopardised and even in a breeding season, not all is lost in case of a spill.
Mostrar más [+] Menos [-]Seasonal nitrogen and phosphorus dynamics during benthic clam and suspended mussel cultivation
2011
Nizzoli, Daniele | Welsh, David Thomas | Viaroli, Pierluigi
Effects of suspended mussel and infaunal clam cultivation on sediment characteristics, and benthic organic and inorganic nitrogen and phosphorus fluxes were compared in a shallow coastal lagoon. The two species had different impacts on sediment features, but both created “hotspots” of nutrient fluxes with annual N and P regeneration rates being 4.9 and 13.5 (mussel) and 4.5 and 14.9 (clams) fold greater than those of unfarmed control sediments. Mussel farming also caused considerable nutrient regeneration within the water column with the mussel ropes contributing ∼25% of total inorganic N and P production and at times dominating the sediments (e.g. 95% of SRP production in summer and 45% of DIN production in winter). Such nutrient regeneration rates seriously question the proposal that suspension-feeding bivalves act as a eutrophication buffer, especially during summer when nutrient regeneration rates are maximal, but other nutrient sources (freshwater run-off and unfarmed sediments) are at their lowest.
Mostrar más [+] Menos [-]Impact of hypoxia on the structure and function of benthic epifauna in Tolo Harbour, Hong Kong
2011
Fleddum, A. | Cheung, S.G. | Hodgson, P. | Shin, P.K.S.
In Tolo Harbour, Hong Kong, where hypoxia occurs periodically, a large amount of benthic epifauna was found to be absent in the summer but become abundant again in the winter. This observation may indicate that some species are sensitive in detecting low dissolved oxygen (DO) levels and are able to escape from the harbour to more oxygenated, open waters when conditions deteriorate and return when DO levels are improved. Analysis of biological traits of these animals showed that 58% of the categories showed significant differences between the community structure in summer and winter. The significant biological traits of the few species, which remained in the harbour under the summer’s hypoxic conditions suggested adaptation rather than opportunism to the low DO levels. Our data also showed that trawling can increase DO at the bottom and may benefit the less sensitive species that remained in the habitat during the summer.
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