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341.
对2015—2016年盐城市城区4个空气质量自动监测国控站点的O_3监测数据进行分析,探讨盐城市O_3污染水平、时空分布特征及其与前体物、气象因子之间的关系。结果表明,各站点O_3污染水平较为接近,2016年各站点O_3-8h第90百分位数超标天数较2015年分别下降了43.5%,50.0%,8.7%和43.6%;全年O_3逐月值大致呈双峰分布,高ρ(O_3)主要集中在4—10月;O_3日变化曲线呈明显的单峰分布,一般在05:00—07:00最低,13:00—15:00达到峰值;不同季节的O_3日变化情况有所差异,午后O_3峰值与O_3日变化幅度均在春季最大,冬季最低;NO、NO_2和CO的日变化曲线均呈现出早晚双峰分布,受早高峰影响,一般在07:00左右达到一日中的最大值;O_3与NO_x等前体物均显著负相关,高ρ(O_3)往往出现在高ρ(CO)/ρ(NO_2)时;总体上各站点的ρ(O_3)随风速的增大而增大。 相似文献
342.
Kurt E. Richardson Nelson A. Cox Douglas E. Cosby Mark E. Berrang 《Journal of environmental science and health. Part. B》2018,53(2):141-144
In a recent study, the pH of commonly used Salmonella pre-enrichment media became acidic (pH 4.0 to 5.0) when feed or feed ingredients were incubated for 24 h. Acidic conditions have been reported to injure or kill Salmonella. In this study, cultures of four known feed isolates (S. montevideo, S. senftenberg, S. tennessee, and S. schwarzengrund) and four important processing plant isolates (S. typhimurium, S. enteritidis, S. infantis, and S. heidelberg) were grown on meat and bone meal and later subjected to desiccation and heat exposure to stress the microorganism. The impact of stress on the isolates ability to survive in acidic conditions ranging from pH 4.0 to 7.0 was compared to the non-stressed isolate. Cell injury was determined on xylose lysine tergitol 4 (XLT4) and cell death determined on nutrient agar (NA). When measured by cell death in non-stressed Salmonella, S. typhimurium was the most acid tolerant and S. heidelberg was the most acid sensitive whereas in stressed Salmonella, S. senftenberg was the most acid tolerant and S. tennessee was the most acid sensitive. The pH required to cause cell injury varied among isolates. With some isolates, the pH required for 50% cell death and 50% cell injury was similar. In other isolates, cell injury occurred at a more neutral pH. These findings suggest that the pH of pre-enrichment media may influence the recovery and bias the serotype of Salmonella recovered from feed during pre-enrichment. 相似文献
343.
K. K. Nkongolo R. Narendrula-Kotha K. Kalubi S. Rainville P. Michael 《Chemistry and Ecology》2017,33(9):795-806
Nickel (Ni) and copper (Cu) are the most prevalent metals found in the Greater Sudbury Region ecosystems. The main objectives of this study are to (1) assess silver maple (Acer saccharinum) tolerance to different doses of Ni and (2) determine the translocation pattern of metals in A. sacharinum. This study revealed that A. sacharinum is highly tolerant to high doses of NI (1600 and 9200?mg/kg). Growth chamber screening trials revealed that Ni is stored in roots and does not translocate to other plant parts. Analysis of samples from A. sacharinum growing for >30 years in soil contaminated with metals also showed that the levels of iron (Fe), manganese (Mn), Ni, and zinc (Zn) were significantly higher in roots compared with soils and aerial parts. On the other hand, the amount of Cu was higher in soil compared with roots and other plant parts. In fact, the bioaccumulation factors (BFs) were 0.29, 2.00, 3.6, 1.9, and 4.0 for Cu, Fe, Mn, Ni, and Zn, respectively. The translocation from roots to aerial parts showed an insignificant level of movement of Cu, Fe, and Ni. Hence, A. saccharinum is classified as excluder for Fe, Mn, Ni, and Zn, and avoider for Cu. 相似文献
344.
β射线法空气PM_(10)监测结果的准确性探讨 总被引:1,自引:0,他引:1
目前国内有很多地市使用β射线法仪器监测空气PM10,本文结合实际,在国内PM10连续自动监测质量控制体系相对薄弱且国家尚未开展标准膜片检定与溯源的情况下,对在用β射线法仪器PM10监测结果的准确性进行了一些实验探讨,期望能提供给同行参考。 相似文献
345.
Ozone dynamics in our study area (Castellon, Spain) is both strongly bound to the mesoscale circulations that develop under
the effect of high insolation (especially in summer) and conditioned by the morphological characteristics of the Western Mediterranean
Basin. In this work we present a preliminary analysis of ozone time series on five locations in Castellon for the period 1997–2003.
We study their temporal and spatial variations at different scales: daily, weekly, seasonally and interannually. Because both
the O3 concentration and its temporal variation depend on the topographic location of the observing station, they can show large
differences within tens of kilometer. We also contrast the variation in the ozone concentration with the variations found
for meteorological variables such as radiation, temperature, relative humidity and recirculation of the air mass. The link
between elevated ozone concentrations and high values of the recirculation factor (r=0.7–0.9) shown the importance of recirculating flows on the local air pollution episodes. 相似文献
346.
The atmospheric chemical composition is affected by the interaction mechanisms among gases and particulate matter through
a wide range of chemical reactions that can occur with the aid of particulate matter (e.g. particles act as reacting or absorbing
surfaces) or be influenced by the presence of particulate matter in the atmosphere (photochemical reactions). Physical and
chemical processes are also bonded in an interactive way that often leads to the influence of the radiation budget, cloud
physics and the warming or cooling of the lower atmospheric levels. The Euro-Mediterranean region is a key-sensitive area
due to the unique climatic and air quality characteristics associated with the regional climatic patterns, geomorphology (land
and water contrast) and coexistence of pollutants from different origin. Focusing on this region, the gas-aerosol interactions
are studied using state-of-the-art atmospheric and chemical transport modeling tools following the necessary development in
the chemical transport model CAMx. Sensitivity and large-scale simulations have shown significant responses of the modeling
system to the inclusion of natural species emissions, the direct shading effect of dust particles on photochemical processes
and the formation of new types of aerosols through heterogeneous uptake of gases on dust particles. Including such interactions
in the chemical transport model often led to the improvement of the model performance compared with available measurements
in the region. 相似文献
347.
David L. Fabacher Edward E. Little Gary K. Ostrander 《Environmental science and pollution research international》1999,6(2):69-71
We exposed albino and pigmented medakaOryzias latipes to simulated solar ultraviolet-B (UVB) radiation to determine if albino medaka were less tolerant of UVB radiation than medaka
pigmented with melanin. There was no difference in the number of albino and pigmented medaka that died during the exposure
period. Spectrophotometric analyses of the outer dorsal skin layers from albino and pigmented medaka indicated that, prior
to exposure, both groups of fish had similar amounts of an apparent colorless non-melanin photoprotective substance that appears
to protect other fish species from UVB radiation. Our results indicate that albino medaka were as tolerant of UVB radiation
as pigmented medaka because they had similar amounts of this photoprotective substance in the outer layers of the skin. 相似文献
348.
Manning WJ Paoletti E Sandermann H Ernst D 《Environmental pollution (Barking, Essex : 1987)》2011,159(12):3283-3293
Ethylenediurea (EDU) has been widely used to prevent ozone (O3) injury and crop losses in crop plants and growth reductions in forest trees. Successful use requires establishing a dose/response curve for EDU and the proposed plant in the absence of O3 and in the presence of O3 before initiating multiple applications to prevent O3 injury. EDU can be used to verify foliar O3 symptoms in the field, and to screen plants for sensitivity to O3 under ambient conditions. Despite considerable research, the mode of action of EDU remains elusive. Additional research on the mode of action of EDU in suppressing O3 injury in plants may also be helpful in understanding the mode of action of O3 in causing injury in plants. 相似文献
349.
Pleijel H 《Environmental pollution (Barking, Essex : 1987)》2011,159(4):897-902
This study considered effects of reduced [O3] on wheat yield. Open-top chamber charcoal filtered air treatments were compared with non-filtered treatments for field-grown wheat. 30 experiments meeting requirements were found, representing nine countries in North America, Europe and Asia. 26 experiments reported improved yield and 4 experiments reduced yield by filtration, a significant positive effect. Average yield improvement was 9%. Average daytime [O3] was reduced by filtration from 35 to 13 nmol mol−1. Filtration efficiency was 63% for O3 and 56% for SO2. For NOx it was observed that NO2 was reduced and NO increased by filtration. Thus, filters convert NO2 to NO. Most experiments reported low or very low [SO2] and [NOx]. Thus, O3 can be concluded to be the main phytotoxic component in the experiments. Elevated [NO2] was observed in one experiment. The conclusion is that current [O3] over large parts of the world adversely affect wheat yield. 相似文献
350.