Уточнить поиск
Результаты 591-600 из 3,243
Estimation of the isoprene emission from the Inner Mongolia grassland
2015
Bai, Jianhui
Measurements of isoprene emissions, solar spectral radiation, temperature and relative humidity were carried out at a grassland site in the Inner Mongolia, China during the growing seasons in 2002 and 2003. Isoprene emissions are dependent on PAR (Photosynthetically Active Radiation) and temperature nonlinearly. PAR controls the main processes related to isoprene emission, thus, PAR energy balance is used to establish quantitative relationship between isoprene emission and its affecting factors. An empirical Equation of isoprene emission was built on the basis of PAR energy balance. The calculated values were in good agreement with those measured for 2002 and 2003 summer seasons, the relative biases of 70% estimated emissions were within 50% compared to measured fluxes. The chamber changes the inside environment and emission fluxes, the emission differences were estimated by using the empirical Equation. The results show that isoprene emission flux around the noon decreases by 37% when the chamber is used, i.e., the biggest effect was resulted from PAR difference caused by the chamber. Isoprene emission measured by chamber should be corrected. The empirical model of isoprene emission showed that isoprene emission fluxes were close to zero, when PAR was low in early morning and in late evening. Total isoprene emissions emitted from the grassland in the Inner Mongolia were 1.10 and 1.00gC m−2 during the growing seasons of 2002 and 2003, respectively, which contributed to about 3.1–4.3% and 2.8−3.9% to grass respiration. The averaged isoprene emission normalized to a standard light (1 500μmolm−2 s−1) and temperature (30 °C) condition was 482.8μg m−2 h−1.
Показать больше [+] Меньше [-]Biomass burning emissions contaminate winter snowfalls in urban Beijing: A case study in 2012
2015
You, Chao | Gao, Shaopeng | Xu, Chao
Three monosaccharide anhydrides levoglucosan, mannosan and galactosan were detected in winter snowfall samples of 2012 in urban Beijing. Concentrations of three isomers vary from 0.15 to 54.43ngmL−1, with an average value of 10.49ngmL−1. Levoglucosan is the most abundant component. Winter snowfalls are contaminated by biomass burning emissions seriously in urban Beijing. The main sources are softwood and crop residue burnings around Beijing from late autumn to early winter, while long-range transport of biomass burning emissions contribute more during the late winter. Concentrations of monosaccharide anhydrides in snowfall samples may be affected by both topography and the meteorological conditions around urban Beijing.
Показать больше [+] Меньше [-]Application of Stabilized Nanoparticles for In Situ Remediation of Metal-Contaminated Soil and Groundwater: a Critical Review
2015
Liu, Wen | Tian, Shuting | Zhao, Xiao | Xie, Wenbo | Gong, Yanyan | Zhao, Dongye
Remediation of soil and groundwater contaminated with toxic metals has been a major environmental challenge for decades. Yet, cost-effective and sustainable in situ remediation technologies remain lacking. Over the last 15 years or so, an innovative in situ remediation strategy has shown promising by means of stabilized nanoparticles. Stabilized nanoparticles are prepared using novel stabilizers that facilitate the deliverability and transport of nanoparticles in the subsurface. This study reviews synthesis and characterization of some model stabilized nanoparticles and their application for remediation of metal-contaminated soil and water. Fate and transport of these stabilized nanoparticles in groundwater and soil are also examined. Lastly, this review identifies the key knowledge gaps such as lack of field data pertaining to the long-term effectiveness of the immobilized metals and impacts of the delivered nanoparticles on the biogeochemical conditions in the subsurface. The information may facilitate further development of this promising remediation technology.
Показать больше [+] Меньше [-]Arsenic Contamination in Soil and Sediment in India: Sources, Effects, and Remediation
2015
Shrivastava, Anamika | Ghosh, Devanita | Dash, Ayusman | Bose, Suatapa
Arsenic contamination is turning out to be a major problem these days with its area coverage and the number of people affected directly or indirectly. Now, the level of the contaminant has spread over the soil and sediments from groundwater and other natural sources. Arsenic poisoning in groundwater events is familiar to the world, but the consequences of soil contamination are still unrevealed to the community, specially the people of contaminated counties. Arsenic is a serious instantaneous concern for the people and other life forms regarding the poisoning through crops and vegetables. Many remediation technologies that mainly include physical, chemical, and a few biological methods have been evolved with time to check its effects. The physical and chemical methods for this purpose are often inefficient and/or very expensive, mainly limited to application in aqueous systems, and produce toxic sludge, which again becomes a matter of concern. But bioremediation relies on the fact that biological organisms have the ability to degrade, detoxify, and even accumulate harmful chemicals and offers attractive perspectives for biomonitoring (via biosensors), treatment of wastewater, and the recycling of polluted soils.
Показать больше [+] Меньше [-]Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics
2015
Napper, Imogen E. | Bakir, Adil | Rowland, Steven J. | Thompson, Richard C.
Cosmetic products, such as facial scrubs, have been identified as potentially important primary sources of microplastics to the marine environment. This study characterises, quantifies and then investigates the sorptive properties of plastic microbeads that are used as exfoliants in cosmetics. Polyethylene microbeads were extracted from several products, and shown to have a wide size range (mean diameters between 164 and 327μm). We estimated that between 4594 and 94,500 microbeads could be released in a single use. To examine the potential for microbeads to accumulate and transport chemicals they were exposed to a binary mixture of 3H-phenanthrene and 14C-DDT in seawater. The potential for transport of sorbed chemicals by microbeads was broadly similar to that of polythene (PE) particles used in previous sorption studies. In conclusion, cosmetic exfoliants are a potentially important, yet preventable source of microplastic contamination in the marine environment.
Показать больше [+] Меньше [-]Inputs of anthropogenic nitrogen influence isotopic composition and trophic structure in SE Australian estuaries
2015
Mazumder, Debashish | Saintilan, Neil | Alderson, Brendan | Hollins, Suzanne
Urban development in coastal settings has increased the input of nitrogen into estuaries globally, in many cases changing the composition of estuarine ecosystems. By focussing on three adjacent estuaries with a gradient of anthropogenic N loadings, we used stable isotopes of N and C to test for changes due to increased anthropogenic N input on the structure of some key trophic linkages in estuaries. We found a consistent enrichment in δ15N corresponding to increased anthropogenic N at the three ecosystem levels studied: fine benthic organic matter, grazing invertebrate, and planktivorous fish. The degree of enrichment in δ15N between fine benthic organic matter and the grapsid crab Parasesarma erythrodactyla was identical across the three sites. The glassfish Ambassis jacksoniensis showed lower levels of enrichment compared to basal food sources at the higher N-loaded sites, suggesting a possible effect of anthropogenic N in decreasing food-chain length in these estuaries.
Показать больше [+] Меньше [-]Endangered New Caledonian endemic mushroom coral Cantharellus noumeae in turbid, metal-rich, natural and artificial environments
2015
Gilbert, Antoine | Heintz, Tom | Hoeksema, Bert W. | Benzoni, Francesca | Fernandez, Jean-Michel | Fauvelot, Cécile | Andréfouët, Serge
Since its description in 1984, little attention has been paid to the New Caledonian endemic mushroom coral Cantharellus noumeae (Fungiidae), an IUCN Red-listed, endangered coral species. Our study presents the first ever quantitative assessment conducted on C. noumeae populations for two contrasting sites in the same turbid bay. Sites differed by their substrates of artificial or natural origins. Metal concentrations of superficial sediment were measured. C. noumeae was found in high densities in metal-rich and turbid environments at both locations, reaching up to 288 individuals per 50m2. It was 3.5 times more abundant on natural rock than on artificial substrates. Recruitment was also higher proportionally on rock (47% vs 7–14%). The composition of the associated coral communities included 30–37 species occurring in low densities. Our findings clarify the environmental niche of this species and its colonization potential, in order to eventually better characterize its conservation status.
Показать больше [+] Меньше [-]Recommendations on standardizing lists of marine alien species: Lessons from the Mediterranean Sea
2015
Marchini, Agnese | Galil, Bella S. | Occhipinti, Anna
Analyses of marine alien species based on national/regional datasets are of paramount importance for the success of regulation on the prevention and management of invasive alien species. Yet in the extant data systems the criteria for the inclusion of records are seldom explicit, and frequently inconsistent in their definitions, spatial and temporal frames and comprehensiveness. Agreed-upon uniform guiding principles, based on solid and transparent scientific criteria, are therefore required in order to provide policy makers with validated and comparable data. Following a meta-analysis on the records of marine alien species in the Mediterranean Sea, we recommend a judicious approach to compiling the data. Here, three categories of uncertainty were identified: species' taxonomic identification, species' actual occurrence in the area, and its status as an alien. In proposing guiding principles to standardize such datasets, we aim to encourage discourse on logical, standardized and transparent criteria to substantiate records of alien species.
Показать больше [+] Меньше [-]Black coral as a new environmental recorder: The lead profiles in coral skeletons over the past century
2015
Lu, Shan | Cai, Weiying | Zhang, Xiaodi | Li, Xiubao | Huang, Hui | Zhang, Fenfen | Zhang, Jing
Lead (Pb) is a typical heavy metal pollutant in the environment, and most Pb contamination comes from human activities. In the present work, the Pb contents of two black coral specimens (Cirrhipathes spp.) collected from the northern South China Sea were measured by synchrotron radiation micro X-ray fluorescence (SR μ-XRF) analysis with 2.5μm resolution. The results showed that sample SY-1 from the Sanya Bay (near the continent) exhibited higher Pb levels and greater fluctuations than sample XS-1 from the Xisha Islands (off the continent), reflecting the influence of terrestrial input and atmospheric deposition in coastal surface seawater. The present work also demonstrated that the Pb profile in black coral nearshore was highly influenced by human activities, mainly by war and economic development. Thus, black coral may serve as a new potential environmental Pb recorder with SR μ-XRF analytical technology.
Показать больше [+] Меньше [-]Changes to the biomass and species composition of Ulva sp. on Porphyra aquaculture rafts, along the coastal radial sandbank of the Southern Yellow Sea
2015
Huo, Yuanzi | Han, Hongbin | Shi, Honghua | Wu, Hailong | Zhang, Jianheng | Yu, Kefeng | Xu, Ren | Liu, Caicai | Zhang, Zhenglong | Liu, Kefu | He, Peimin | Ding, Dewen
Compositions, changes and biomass of attached Ulva species on Porphyra rafts along the radial sandbank in the Yellow Sea were investigated, and potential contributions to green tides was analyzed. Ulva prolifera, Ulva flexuosa and Ulva linza were all appeared throughout the investigated period. U. prolifera and U. flexuosa dominated attached Ulva population on Porphyra rafts. Attached Ulva species biomass showed obviously spatial and temporal variations. Temperature, Ulva microscopic propagules and human activities were main factors to influence attached Ulva species biomass. The total attached Ulva species biomass was more than 20,000 fresh weight tons in April, and the green tide causative species U. prolifera accounted 51.03% in April 2013 before green tides occurred. The high biomass of attached Ulva species would contribute most to green tides in the Yellow Sea. But how attached Ulva species on Porphyra rafts contributing to green tides in the Yellow Sea should be further studied.
Показать больше [+] Меньше [-]