细化搜索
结果 651-660 的 2,503
Glyphosate persistence in seawater
2014
Mercurio, Philip | Flores, Florita | Mueller, Jochen F. | Carter, S. (Steve) | Negri, Andrew P.
Glyphosate is one of the most widely applied herbicides globally but its persistence in seawater has not been reported. Here we quantify the biodegradation of glyphosate using standard “simulation” flask tests with native bacterial populations and coastal seawater from the Great Barrier Reef. The half-life for glyphosate at 25°C in low-light was 47days, extending to 267days in the dark at 25°C and 315days in the dark at 31°C, which is the longest persistence reported for this herbicide. AMPA, the microbial transformation product of glyphosate, was detected under all conditions, confirming that degradation was mediated by the native microbial community. This study demonstrates glyphosate is moderately persistent in the marine water under low light conditions and is highly persistent in the dark. Little degradation would be expected during flood plumes in the tropics, which could potentially deliver dissolved and sediment-bound glyphosate far from shore.
显示更多 [+] 显示较少 [-]Contemporary radioecological state of the North-western Black Sea and the problems of environment conservation
2014
Tereshchenko, N.N. | Mirzoyeva, N.Yu | Gulin, S.B. | Milchakova, N.A.
Review is devoted to the analysis of a radioecological situation in the North-western Black Sea and concerns the levels of contamination of the components of an ecosystem by the main artificial radioactive isotopes (90Sr, 137Cs, 239,240Pu). The long-term accumulation trends of these radionuclides were analyzed in components of the Black Sea ecosystem after the Chernobyl nuclear power plant accident. Zones that have an increased ability to accumulate these radioisotopes were revealed. The assessment of irradiation dose rates formed by 90Sr, 137Cs and 239,240Pu in Black Sea hydrobionts was obtained. The strategy for biodiversity conservation and sustainable management of natural resources should include monitoring of the radioecological state of the marine ecosystems, and the formation of a complex of biogeochemical criteria for assessment of an ecological situation in the sea. This approach is important for marine protected areas, since it allows the formation of a basis for scientific and practical function.
显示更多 [+] 显示较少 [-]Acclimation and toxicity of high ammonium concentrations to unicellular algae
2014
Collos, Yves | Harrison, Paul J.
A literature review on the effects of high ammonium concentrations on the growth of 6 classes of microalgae suggests the following rankings. Mean optimal ammonium concentrations were 7600, 2500, 1400, 340, 260, 100μM for Chlorophyceae, Cyanophyceae, Prymnesiophyceae, Diatomophyceae, Raphidophyceae, and Dinophyceae respectively and their tolerance to high toxic ammonium levels was 39,000, 13,000, 2300, 3600, 2500, 1200μM respectively. Field ammonium concentrations <100μM would not likely reduce the growth rate of most microalgae. Chlorophytes were significantly more tolerant to high ammonium than diatoms, prymnesiophytes, dinoflagellates, and raphidophytes. Cyanophytes were significantly more tolerant than dinoflagellates which were the least tolerant. A smaller but more complete data set was used to estimate ammonium EC50 values, and the ranking was: Chlorophyceae>Cyanophyceae, Dinophyceae, Diatomophyceae, and Raphidophyceae. Ammonia toxicity is mainly attributed to NH3 at pHs >9 and at pHs <8, toxicity is likely associated with the ammonium ion rather than ammonia.
显示更多 [+] 显示较少 [-]The proteome of Atlantic herring (Clupea harengus L.) larvae is resistant to elevated pCO2
2014
Maneja, Rommel H. | Dineshram, R. | Thiyagarajan, Vengatesen | Skiftesvik, Anne Berit | Frommel, Andrea Y. | Clemmesen, Catriona | Geffen, Audrey J. | Browman, Howard I.
Elevated anthropogenic pCO2 can delay growth and impair otolith structure and function in the larvae of some fishes. These effects may concurrently alter the larva’s proteome expression pattern. To test this hypothesis, Atlantic herring larvae were exposed to ambient (370μatm) and elevated (1800μatm) pCO2 for one-month. The proteome structure of the larvae was examined using a 2-DE and mass spectrometry. The length of herring larvae was marginally less in the elevated pCO2 treatment compared to the control. The proteome structure was also different between the control and treatment, but only slightly: the expression of a small number of proteins was altered by a factor of less than 2-fold at elevated pCO2. This comparative proteome analysis suggests that the proteome of herring larvae is resilient to elevated pCO2. These observations suggest that herring larvae can cope with levels of CO2 projected for near future without significant proteome-wide changes.
显示更多 [+] 显示较少 [-]Mercury concentrations in breast feathers of three upper trophic level marine predators from the western Aleutian Islands, Alaska
2014
Kaler, Robb S.A. | Kenney, Leah A. | Bond, Alexander L. | Eagles-Smith, Collin A.
Mercury (Hg) is a toxic element distributed globally through atmospheric transport. Agattu Island, located in the western Aleutian Islands, Alaska, has no history of point-sources of Hg contamination. We provide baseline levels of total mercury (THg) concentrations in breast feathers of three birds that breed on the island. Geometric mean THg concentrations in feathers of fork-tailed storm-petrels (Oceanodroma furcata; 6703±1635, ng/g fresh weight [fw]) were higher than all other species, including snowy owl (Bubo scandiacus; 2105±1631, ng/g fw), a raptor with a diet composed largely of storm-petrels at Agattu Island. There were no significant differences in mean THg concentrations of breast feathers among adult Kittlitz’s murrelet (Brachyramphus brevirostris; 1658±1276, ng/gfw) and chicks (1475±671, ng/gfw) and snowy owls. The observed THg concentrations in fork-tailed storm-petrel feathers emphasizes the need for further study of Hg pollution in the western Aleutian Islands.
显示更多 [+] 显示较少 [-]Effects of the sandbar breaching on hydrobiological parameters and zooplankton communities in the Senegal River Estuary (West Africa)
2014
Champalbert, Gisèle | Pagano, Marc | Arfi, Robert | Chevalier, Cristèle
This study describes the changes in hydrology, zooplankton communities and abundance in the Senegal River Estuary (SRE) before and after the breaching of the sandbar in October 2003. Samples were taken in 2003 at 3 stations located upstream (DI), in mid estuary (HY) and downstream (RM), and in 2005 at the same stations (RM becoming Old River Mouth: ORM), plus the new river mouth (NRM) resulting from the morphological evolution of the SRE.The study showed marked seasonal variations that affected the structure and distribution of zooplankton as well as major changes caused by the sandbar opening:–increased marine influence throughout the whole SRE,–changes in the horizontal gradients,–arrival of euryhaline species and increase in meroplankton, in particular decapod larvae,–transformation of the ORM area into a slackwater area with limited exchanges and the highest zooplankton numbers during high waters.
显示更多 [+] 显示较少 [-]Assessment of heavy metal impact on sediment quality of the Xiaoqinghe estuary in the coastal Laizhou Bay, Bohai Sea: Inconsistency between two commonly used criteria
2014
Zhuang, Wen | Gao, Xuelu
Surface sediments in the Xiaoqinghe estuary, southwestern coastal Laizhou Bay, were examined to assess the bio-toxic risk of heavy metals (Cd, Cu, Ni, Pb and Zn) with the effects range-low and effects range-median guidelines (ERL–ERMs) and the concentration ratio of simultaneously extractable metals to acid volatile sulfides ([SEM]/[AVS]). Based on the ERL–ERM guidelines, bio-toxic effect caused by Cu, Ni, Pb and Zn could be expected in the riverine surface sediments of the Xiaoqinghe estuary; and the surface sediments in the marine area were in good quality and only Ni might cause bio-toxic effect occasionally. The AVS–SEM guidelines revealed that no bio-toxic effect could be caused by any of the studied metals in both the riverine and marine sediments, since there were excess sulfides in surface sediments which could form water-insoluble substances with free metal ions and reduce the bioavailability of heavy metals.
显示更多 [+] 显示较少 [-]Distribution and recovery trajectory of Macondo (Mississippi Canyon 252) oil in Louisiana coastal wetlands
2014
Turner, R Eugene | Overton, Edward B. | Meyer, Buffy M. | Miles, M. Scott | McClenachan, Giovanna | Hooper-Bui, Linda | Engel, Annette Summers | Swenson, Erick M. | Lee, James M. | Milan, Charles S. | Gao, Heng
We measured the concentration of petroleum hydrocarbons in 405 wetland sediment samples immediately before the April 2010 Deepwater Horizon disaster led to their broad-scale oiling, and on nine trips afterwards. The average concentrations of alkanes and PAHs were 604 and 186 times the pre-spill baseline values, respectively. Oil was distributed with some attenuation up to 100m inland from the shoreline for alkanes, but increased for aromatics, and was not well-circumscribed by the rapid shoreline assessments (a.k.a. SCAT) of relative oiling. The concentrations of target alkanes and PAHs in June 2013 were about 1% and 5%, respectively, of the February 2011 concentrations, but remained at 3.7 and 33 times higher, respectively, than in May 2010. A recovery to baseline conditions suggests that the concentration of alkanes may be near baseline values by the end of 2015, but that it may take decades for the PAH concentrations to be that low.
显示更多 [+] 显示较少 [-]Input and dispersion of nutrients from the Jeddah Metropolitan Area, Red Sea
2014
Peña-García, David | Ladwig, Norbert | Turki, Adnan J. | Mudarris, Mohammed S.
Large amounts of waste water are discharged from the Jeddah Metropolitan Area into the Red Sea. Daily loads of total nitrogen (TN) and phosphorus (TP) amount to 6564kg and 2241kg, respectively, comprising 83% of dissolved inorganic nitrogen and 33% of dissolved phosphate. Steep gradients prevail nearshore, ranging from 2000μMTN and 250μMTP in the hypertrophic city lagoons to 6μMTN and 0.4μMTP in the adjacent oligotrophic water. Sewage inputs from Al Khumra, Jeddah’s main outfall, cause a widespread but moderate increase in surface nutrient concentrations due to the submerged diffuser. The nutrient pool in the oligotrophic water is dominated by dissolved organic and particulate forms, with nitrate frequently below the detection limit, indicating rapid transformation of inorganic nutrients. N:P ratios, as well as half-saturation constants for phytoplankton growth, suggest that nitrogen is the limiting factor restricting primary production in the area.
显示更多 [+] 显示较少 [-]Observations of air quality on the outskirts of an urban agglomeration during the implementation of pollution reduction measures
2014
Sun, Yang | Zhang, Junke | Pan, Yuepeng | Wang, Yuesi | Liao, Tingting | Song, Tao
Based on observations at Heshan, a boundary area in the city agglomeration of the Pearl River Delta region in China, atmospheric pollutants such as PM2.5, O3, CO, SO2, NOZ, NO2 and NO were monitored between the 12th and 29th November, 2010. Meteorological parameters, including temperature, humidity, dew point, air pressure, ultraviolet light, wind direction, and wind speed were also measured. By combining the meteorological parameters with the atmospheric pollutant data, we performed Positive Matrix Factorization (PMF) and ozone production efficiency (OPE) analysis to objectively understand the interrelations among the pollutants, as well as between the pollutants and the meteorological factors. During the observation period, there were various meteorological changes such as rainfall, cold air transit, and sunshine that created conditions for the formation or dispersal of pollutants. The study period coincided with the 16th Asian Games, during which time the government adopted strict measures to reduce the discharge of pollutants around the Pearl River Delta area. However, we still observed serious pollution of PM2.5 and O3, of which the highest value of PM2.5 was 210 μg m−3 and the highest value of O3 reached 117 ppb. At the same time, the high concentrations of CO, NO, NO2, NOZ, and SO2 could not be cleared away with rainfall in such a short period of time. On the basis of PMF analysis, we found that three factors influence the air quality of this region: local biomass burning, secondary pollutants of regional transport, and high industrial pollutant emissions. According to OPE analysis, the O3 pollution was mostly found to be VOC–sensitive but occasionally NOX–sensitive for OPE values greater than 10.
显示更多 [+] 显示较少 [-]