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排序方式: 共有256条查询结果,搜索用时 281 毫秒
31.
六价铬还原细菌Bacillus cereus S5.4还原机理及酶学性质研究 总被引:2,自引:1,他引:1
从宝钢电镀污泥中分离得到1株六价铬还原细菌Bacillus cereus S5.4,在液体LB培养基中培养72 h完全还原2 mmol/L Cr6+.测定该菌株六价铬还原后细胞内外六价铬和总铬浓度,检测细胞各组分六价铬还原能力,并结合扫描电镜分析六价铬还原前后细胞形态的变化.结果表明,细菌的细胞壁膜能阻止六价铬进入细胞,是六价铬发生还原的主要场所,其通透性的改变将影响六价铬还原酶的作用;该菌株六价铬还原酶为非分泌型,在细菌细胞内侧发生作用.测定六价铬还原酶活性和稳定性:其最适温度范围25~37℃,最适pH 7,Cu2+有增强六价铬还原酶活性的作用;在37℃,该菌株六价铬还原酶Km为125.61 μmol/L,Vmax为7.68 nmol/(min·mg). 相似文献
32.
Long-term study of air pollution plays a decisive role in formulating and refining pollution control strategies. In this study, two 12-month measurements of PM2.5 mass and speciation were conducted in 00/01 and 04/05 to determine long-term trend and spatial variations of PM2.5 mass and chemical composition in Hong Kong. This study covered three sites with different land-use characteristics, namely roadside, urban, and rural environments. The highest annual average PM2.5 concentration was observed at the roadside site (58.0±2.0 μg m−3 (average±2σ) in 00/01 and 53.0±2.7 μg m−3 in 04/05), followed by the urban site (33.9±2.5 μg m−3 in 00/01 and 39.0±2.0 μg m−3 in 04/05), and the rural site (23.7±1.9 μg m−3 in 00/01 and 28.4±2.4 μg m−3 in 04/05). The lowest PM2.5 level measured at the rural site was still higher than the United States’ annual average National Ambient Air Quality Standard of 15 μg m−3. As expected, seasonal variations of PM2.5 mass concentration at the three sites were similar: higher in autumn/winter and lower in summer. Comparing PM2.5 data in 04/05 with those collected in 00/01, a reduction in PM2.5 mass concentration at the roadside (8.7%) but an increase at the urban (15%) and rural (20%) sites were observed. The reduction of PM2.5 at the roadside was attributed to the decrease of carbonaceous aerosols (organic carbon and elemental carbon) (>30%), indicating the effective control of motor vehicle emissions over the period. On the other hand, the sulfate concentration at the three sites was consistent regardless of different land-use characteristics in both studies. The lack of spatial variation of sulfate concentrations in PM2.5 implied its origin of regional contribution. Moreover, over 36% growth in sulfate concentration was found from 00/01 to 04/05, suggesting a significant increase in regional sulfate pollution over the years. More quantitative techniques such as receptor models and chemical transport models are required to assess the temporal variations of source contributions to ambient PM2.5 mass and chemical speciation in Hong Kong. 相似文献
33.
Sung-Geun Woo Holly L. Sewell Craig S. Criddle 《Frontiers of Environmental Science & Engineering》2022,16(10):127
34.
由于人口的快速增长,人类活动导致近地层O3浓度不断提高,O3浓度升高将对植物、动物和人体健康产生极大的危害.采用开顶式气室(OTC)原位实验方法,研究O3浓度升高对不同生长期冬小麦叶片抗氧化系统的影响,进而分析O3对植物的伤害机制.结果表明,O3浓度升高可导致冬小麦拔节期和抽穗期叶片超氧化物歧化酶(SOD)、过氧化物酶... 相似文献
35.
Robyn E. Tuerena Claire Mahaffey Sian F. Henley Camille de la Vega Louisa Norman Tim Brand Tina Sanders Margot Debyser Kirstin Dhnke Judith Braun Christian Mrz 《Ambio》2022,51(2):355
Climate change is altering nutrient cycling within the Arctic Ocean, having knock-on effects to Arctic ecosystems. Primary production in the Arctic is principally nitrogen-limited, particularly in the western Pacific-dominated regions where denitrification exacerbates nitrogen loss. The nutrient status of the eastern Eurasian Arctic remains under debate. In the Barents Sea, primary production has increased by 88% since 1998. To support this rapid increase in productivity, either the standing stock of nutrients has been depleted, or the external nutrient supply has increased. Atlantic water inflow, enhanced mixing, benthic nitrogen cycling, and land–ocean interaction have the potential to alter the nutrient supply through addition, dilution or removal. Here we use new datasets from the Changing Arctic Ocean program alongside historical datasets to assess how nitrate and phosphate concentrations may be changing in response to these processes. We highlight how nutrient dynamics may continue to change, why this is important for regional and international policy-making and suggest relevant research priorities for the future.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13280-021-01673-0. 相似文献
36.
Henrieta Dulaiova Richard Camilli Matthew A. Charette 《Journal of environmental radioactivity》2010,101(7):553-8921
We constructed a survey system of radon/methane/nitrate/salinity to find sites of submarine groundwater discharge (SGD) and groundwater nitrate input. We deployed the system in Waquoit Bay and Boston Harbor, MA where we derived SGD rates using a mass balance of radon with methane serving as a fine resolution qualitative indicator of groundwater. In Waquoit Bay we identified several locations of enhanced groundwater discharge, out of which two (Childs and Quashnet Rivers) were studied in more detail. The Childs River was characterized by high nitrate input via groundwater discharge, while the Quashnet River SGD was notable but not a significant source of nitrate. Our radon survey of Boston Harbor revealed several sites with significant SGD, out of these Inner Harbor and parts of Dorchester Bay and Quincy Bay had groundwater fluxes accompanied by significant water column nitrogen concentrations. The survey system has proven effective in revealing areas of SGD and non-point source pollution. 相似文献
37.
Short-term increases in soil solution nitrate (NO3−) concentration are often observed after forest harvest, even in N-limited systems. We model NO3− leaching below the rooting zone as a function of site productivity. Using national forest inventories and published estimates of N attenuation in rivers and the riparian zone, we estimate effects of stem-only harvesting on NO3− leaching to groundwater, surface waters and the marine environment. Stem-only harvesting is a minor contributor to NO3− pollution of Swedish waters. Effects in surface waters are rapidly diluted downstream, but can be locally important for shallow well-waters as well as for the total amount of N reaching the sea. Harvesting adds approximately 8 Gg NO3-N to soil waters in Sweden, with local concentrations up to 7 mg NO3-N l−1. Of that, ∼3.3 Gg reaches the marine environment. This is ∼3% of the overall Swedish N load to the Baltic. 相似文献
38.
The protective effect of hydroxytyrosol (HT), a strong antioxidant compound from extra virgin olive oil, against TCDD induced toxicity was investigated in human peripheral blood mononuclear cells (PBMC). PBMC (1 × 106 cells mL−1) were divided into four groups and were incubated in a CO2 incubator (5% CO2) for 12 h with vehicle, TCDD (10 nM), TCDD + HT (10 nM + 100 μM) and HT alone (100 μM) respectively. To clarify the role of HT against TCDD induced cytotoxicity, oxidative stress and the levels of antioxidant enzymes were assessed. Incubation of PBMC with TCDD significantly decreased cell viability, catalase (CAT) and glutathione peroxidase (GPx) and increased the levels of superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers such as lipid peroxidation products (LPO), protein carbonyl content (PCC) and reactive oxygen species (ROS). Whereas, HT had an effective antioxidant property as observed by the increased cell viability, normalization of antioxidant enzymes and decreased levels of LPO, PCC and ROS in PBMC co-treated with HT and TCDD. Apoptosis detection and comet assay results shows that HT, by acting as an antioxidant, prevents the damage to DNA induced by TCDD. In addition light microscopic and histopathological observations revealed that the cells are apoptotic and degenerated during TCDD treatment, whereas cells showed intact morphology during co-treatment with HT. On the whole, the results reveal that HT exerts a promising antioxidant potential in protecting the PBMC against TCDD induced oxidative stress, which might be due to the presence of catechol moiety in its structure. 相似文献
39.
Quantification of nitrate leaching from German forest ecosystems by use of a process oriented biogeochemical model 总被引:1,自引:0,他引:1
Kiese R Heinzeller C Werner C Wochele S Grote R Butterbach-Bahl K 《Environmental pollution (Barking, Essex : 1987)》2011,159(11):3204-3214
Simulations with the process oriented Forest-DNDC model showed reasonable to good agreement with observations of soil water contents of different soil layers, annual amounts of seepage water and approximated rates of nitrate leaching at 79 sites across Germany. Following site evaluation, Forest-DNDC was coupled to a GIS to assess nitrate leaching from German forest ecosystems for the year 2000. At national scale leaching rates varied in a range of 0–>80 kg NO3–N ha−1 yr−1 (mean 5.5 kg NO3–N ha−1 yr−1). A comparison of regional simulations with the results of a nitrate inventory study for Bavaria showed that measured and simulated percentages for different nitrate leaching classes (0–5 kg N ha−1 yr−1:66% vs. 74%, 5–15 kg N ha−1 yr−1:20% vs. 20%, >15 kg N ha−1 yr−1:14% vs. 6%) were in good agreement. Mean nitrate concentrations in seepage water ranged between 0 and 23 mg NO3–N l−1. 相似文献
40.
Kros J Frumau KF Hensen A de Vries W 《Environmental pollution (Barking, Essex : 1987)》2011,159(11):3171-3182
The integrated modelling system INITIATOR was applied to a landscape in the northern part of the Netherlands to assess current nitrogen fluxes to air and water and the impact of various agricultural measures on these fluxes, using spatially explicit input data on animal numbers, land use, agricultural management, meteorology and soil. Average model results on NH3 deposition and N concentrations in surface water appear to be comparable to observations, but the deviation can be large at local scale, despite the use of high resolution data. Evaluated measures include: air scrubbers reducing NH3 emissions from poultry and pig housing systems, low protein feeding, reduced fertilizer amounts and low-emission stables for cattle. Low protein feeding and restrictive fertilizer application had the largest effect on both N inputs and N losses, resulting in N deposition reductions on Natura 2000 sites of 10% and 12%, respectively. 相似文献