خيارات البحث
النتائج 1251 - 1260 من 4,043
From blue to black: Anthropogenic forcing of carbon and nitrogen influx to mangrove-lined estuaries in the South China Sea النص الكامل
2016
Lee, S.Y.
Southeast Asia is the global centre of mangrove development but human activities have dramatically reduced mangrove area in the region. An analysis is made of the shift in carbon and nitrogen influxes into the South China Sea (SCS) resulting from three anthropogenic nutrient sources: domestic sewage discharge, fertilizer use in rice agriculture and environmental loss from mariculture, between 1997 and 2010. Anthropogenic C and N influxes were, respectively, 1.81× and 1.43× those in 1997, with coastal aquaculture contributing most to the increase. In contrast, fringing mangroves provided ~44% of the C but only ~3% of the N from anthropogenic sources in 2010. In 1997, influx from mangroves was 113% and 6% of anthropogenic influx for C and N, respectively. This dominance by relatively labile anthropogenic nutrients over mangrove sources would change nearshore trophodynamics, with negative implications for the resilience of mangroves and nutrient-intolerant systems such as corals.
اظهر المزيد [+] اقل [-]Spatial distribution and enrichment assessment of heavy metals in surface sediments from Baixada Santista, Southeastern Brazil النص الكامل
2016
Kim, Bianca Sung Mi | Salaroli, Alexandre Barbosa | Ferreira, Paulo Alves de Lima | Sartoretto, Juliê Rosemberg | Mahiques, Michel Michaelovich de | Figueira, Rubens Cesar Lopes
The Baixada Santista, besides being an important estuarine system, is responsible for most of the international trade and economic development in the region because of the Santos Port and the Cubatão Industrial Complex. The aim of this study is to assess heavy metal contamination of the Santos São Vicente Estuary using enrichment factors (EFs) and sediment quality guidelines (SQGs). Thus, superficial sediment samples were subjected to acid digestion and analyzed (Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sc, V, and Zn) by inductively coupled plasma optical emission spectrometry (ICP-OES). The results indicated an absence of contamination, with the EFs indicating moderate enrichment. As and Pb presented higher enrichment probably due to the natural processes of weathering and sedimentation, and the influence of human activity. This conjoint analysis showed that potentially polluting activities are of concern as the highest values converge near the Cubatão Industrial Complex, which correspond to intense urbanization and industrial activity.
اظهر المزيد [+] اقل [-]Parallel measurements of organic and elemental carbon dry (PM1, PM2.5) and wet (rain, snow, mixed) deposition into the Baltic Sea النص الكامل
2016
Witkowska, Agnieszka | Lewandowska, Anita | Falkowska, Lucyna M.
Parallel studies on organic and elemental carbon in PM1 and PM2.5 aerosols and in wet deposition in various forms of its occurrence were conducted in the urbanised coastal zone of the Baltic Sea. The carbon load introduced into the sea water was mainly affected by the form of precipitation. Dry deposition load of carbon was on average a few orders of magnitude smaller than wet deposition. The suspended organic carbon was more effectively removed from the air with rain than snow, while an inverse relationship was found for elemental carbon. However the highest flux of water insoluble organic carbon was recorded in precipitation of a mixed nature. The atmospheric cleaning of highly dissolved organic carbon was observed to be the most effective on the first day of precipitation, while the hydrophobic elemental carbon was removed more efficiently when the precipitation lasted longer than a day.
اظهر المزيد [+] اقل [-]Oil droplets transport due to irregular waves: Development of large-scale spreading coefficients النص الكامل
2016
Geng, Xiaolong | Boufadel, Michel C. | Ozgokmen, Tamay | King, Thomas | Lee, Kenneth | Lu, Youyu | Zhao, Lin
The movement of oil droplets due to waves and buoyancy was investigated by assuming an irregular sea state following a JONSWAP spectrum and four buoyancy values. A technique known as Wheeler stretching was used to model the movement of particles under the moving water surface. In each simulation, 500 particles were released and were tracked for a real time of 4.0h. A Monte Carlo approach was used to obtain ensemble properties. It was found that small eddy diffusivities that decrease rapidly with depth generated the largest horizontal spreading of the plume. It was also found that large eddy diffusivities that decrease slowly with depth generated the smallest horizontal spreading coefficient of the plume. The increase in buoyancy resulted in a decrease in the horizontal spreading coefficient, which suggests that two-dimensional (horizontal) models that predict the transport of surface oil could be overestimating the spreading of oil.
اظهر المزيد [+] اقل [-]Assessing exemptions under the ballast water management convention: preclude the Trojan horse النص الكامل
2016
Olenin, Sergej | Ojaveer, Henn | Minchin, Dan | Boelens, Rick
The International Maritime Organization (IMO) Ballast Water Management Convention (BWMC) is a powerful instrument aimed at reducing spread of harmful aquatic organisms and pathogens (HAOPs). As BWMC is expected to enter into force soon, shipping companies will start seeking exemptions for ballast water management in accordance with BWMC Regulation A-4. However, without scientifically robust risk assessment (RA) and consistent rules, the exemptions may introduce a new form of risk within a convention generally designed to reduce risks. This paper describes an adaptive system for granting exemptions, consisting of six major components: target species selection procedure, port-to-port RA, monitoring, information support, administrative decision and review process. The system is based on key principles defined in the IMO guidelines for RA and is designed to continuously accumulate evolving experience on granting exemptions. The ultimate goal is to contribute to the control of the spread of HAOPs, without placing an unnecessary burden on the shipping industry.
اظهر المزيد [+] اقل [-]Accumulation and temporal changes of PCDD/Fs and dioxin-like PCBs in finless porpoises (Neophocaena asiaeorientalis) from Korean coastal waters: Tracking the effectiveness of regulation النص الكامل
2016
Jeong, Yunsun | Kim, Sang-jo | Shin, Kyung-Hoon | Hwang, Seung Yong | An, Yong-Rock | Moon, Hyo-Bang
Temporal trend studies are useful to evaluate the effectiveness of regulations on local pollutants. The emission of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (PCBs) has been regulated by the Korean government in accordance with the Stockholm Convention. The accumulation and temporal trends of PCDD/Fs and dioxin-like PCBs were investigated in finless porpoises (Neophocaena asiaeorientalis) collected in Korean waters. Median concentrations of PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs were 1.0, 1.1, 0.1, and 1.8pgTEQ/g lipid weight, respectively, which were lower than threshold values for marine mammals. Age- and sex-dependent accumulation patterns were found for PCDFs and DL-PCBs. Temporal trends in finless porpoises collected between 2003 and 2010 showed significant reduction rates of 57%, 54%, 69%, and 60% for PCDDs, PCDFs, non-ortho PCBs, and mono-ortho PCBs, respectively. Our results suggest that the regulations on dioxin-like contaminants have been effective for marine mammals in Korea.
اظهر المزيد [+] اقل [-]Phylogeny of Symbiodinium populations in zoantharians of the northern Persian Gulf النص الكامل
2016
Noori Koupaei, Atoosa | Dehghani, Hamed | Mostafavi, Pargol Ghavam | Mashini, Amirhossein Gheitanchi
Zoantharians of the Persian Gulf (PG) experience periods of anomalous high temperature, irradiance and desiccation. Their survival largely relies on the symbiotic relationship with single celled dinoflagellates of the genus Symbiodinium. However, the phylogeny of symbionts of zoantharians has not been investigated in the region. In this study, the second internal transcribed spacer region of ribosomal DNA (ITS2) was used to recognize in hospite populations of Symbiodinium in Palythoa aff. mutuki, Palythoa tuberculosa and Zoanthus sansibaricus colonies from Hengam, Kish, Larak, and Qeshm Islands, in the PG. The results showed subclade D1–4 and a variant of A1, were the most prevalent subclades of Symbiodinium. Predominance of stress tolerant subclade D1–4 and putatively radiation tolerant variant of A1 of Symbiodinium in zoantharian species might suggest an adaptation strategy to the extreme physical environment of the PG.
اظهر المزيد [+] اقل [-]The occurrence of PAHs and faecal sterols in Dublin Bay and their influence on sedimentary microbial communities النص الكامل
2016
Murphy, Brian T. | O'Reilly, Shane S. | Monteys, Xavier | Reid, Barry F. | Szpak, Michal T. | McCaul, Margaret V. | Jordan, Sean F. | Allen, Christopher C.R. | Kelleher, Brian P.
The source, concentration, and potential impact of sewage discharge and incomplete organic matter (OM) combustion on sedimentary microbial populations were assessed in Dublin Bay, Ireland. Polycyclic aromatic hydrocarbons (PAHs) and faecal steroids were investigated in 30 surface sediment stations in the bay. Phospholipid fatty acid (PLFA) content at each station was used to identify and quantify the broad microbial groups present and the impact of particle size, total organic carbon (%TOC), total hydrogen (%H) and total nitrogen (%N) was also considered. Faecal sterols were found to be highest in areas with historical point sources of sewage discharge. PAH distribution was more strongly associated with areas of deposition containing high %silt and %clay content, suggesting that PAHs are from diffuse sources such as rainwater run-off and atmospheric deposition. The PAHs ranged from 12 to 3072ng/g, with 10 stations exceeding the suggested effect range low (ERL) for PAHs in marine sediments. PAH isomer pair ratios and sterol ratios were used to determine the source and extent of pollution. PLFAs were not impacted by sediment type or water depth but were strongly correlated to, and influenced by PAH and sewage levels. Certain biomarkers such as 10Me16:0, i17:0 and a17:0 were closely associated with PAH polluted sediments, while 16:1ω9, 16:1ω7c, Cy17:0, 18:1ω6, i16:0 and 15:0 all have strong positive correlations with faecal sterols. Overall, the results show that sedimentary microbial communities are impacted by anthropogenic pollution.
اظهر المزيد [+] اقل [-]Release of synthetic microplastic plastic fibres from domestic washing machines: Effects of fabric type and washing conditions النص الكامل
2016
Washing clothes made from synthetic materials has been identified as a potentially important source of microscopic fibres to the environment. This study examined the release of fibres from polyester, polyester-cotton blend and acrylic fabrics. These fabrics were laundered under various conditions of temperature, detergent and conditioner. Fibres from waste effluent were examined and the mass, abundance and fibre size compared between treatments. Average fibre size ranged between 11.9 and 17.7μm in diameter, and 5.0 and 7.8mm in length. Polyester-cotton fabric consistently shed significantly fewer fibres than either polyester or acrylic. However, fibre release varied according to wash treatment with various complex interactions. We estimate over 700,000 fibres could be released from an average 6kg wash load of acrylic fabric. As fibres have been reported in effluent from sewage treatment plants, our data indicates fibres released by washing of clothing could be an important source of microplastics to aquatic habitats.
اظهر المزيد [+] اقل [-]A dynamical systems perspective for a real-time response to a marine oil spill النص الكامل
2016
This paper discusses the combined use of tools from dynamical systems theory and remote sensing techniques and shows how they are effective instruments which may greatly contribute to the decision making protocols of the emergency services for the real-time management of oil spills. This work presents the successful interplay of these techniques for a recent situation, the sinking of the Oleg Naydenov fishing ship that took place in Spain, close to the Canary Islands, in April 2015.
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