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671.
柴油机排放颗粒物净化技术研究进展 总被引:3,自引:0,他引:3
柴油机被认为是城市大气微粒的主要污染源。柴油机颗粒物组成复杂并且颗粒粒径甚小,大都属于亚微米级粒子和纳米级粒子。因而柴油机颗粒物对人类健康和大气环境的影响受到世人的广泛关注。本文主要对柴油机排放颗粒物的生成机理、化学组成及危害、物理性质、检测方法和净化技术等方面进行综述与探讨。 相似文献
672.
Relationships between distributions of longevous population and trace elements in the agricultural ecosystem of Rugao County,Jiangsu, China 总被引:1,自引:0,他引:1
Huang B Zhao Y Sun W Yang R Gong Z Zou Z Ding F Su J 《Environmental geochemistry and health》2009,31(3):379-390
Soil, plant, and water, as well as trace elements they contain, can influence human health through the food chain. A survey
was conducted on distributions of trace elements in soils, plants, and drinking water in Rugao County, Jiangsu Province, China,
an agricultural area with a high level of centenarians and nonagenarians. The ratio of people over 90 years old per 100,000
inhabitants (90-rate) based on village (about 4,000 residents in 4 km2) was correlated with trace elements in soil, drinking water, and rice by means of correlation analysis and/or principal component
analysis. Although the average 90-rate in the whole area was as high as 277, the rates were not uniform across the entire
region. The 90-rate in the area of loamy and strongly-developed Anthrosols and Cambosols was about 330, significantly higher
than the 255 in the areas of sandy and strongly-developed Cambosols and of clayey and weakly-developed Cambosols. The concentrations
of available Se, B, Ni, and Mo in soils of the area with the high 90-rate were markedly greater than those in the area with
the low 90-rate. This was demonstrated by highly positive correlations between the 90-rate and available Se (r = 0.33), B (r = 0.21), Ni (r = 0.17) and Mo (r = 0.17) at the p < 0.01 level and high loadings of available Se (0.851), B (0.535), Ni (0.594) and Mo (0.394) in the longevous factor. Similar
relationships between the available elements in soils and elements in water and rice were found. These results suggest that:
(1) the available forms of elements in soil were more crucial to elemental bio-availability in the ecosystem and human health
than total elements in soil; and (2) the element association above might have affected the 90-rate positively and could be
an important environmental geochemical factor influencing the longevity of humans. 相似文献
673.
采用固相微萃取(SPME)与气相色谱-质谱联用,分析了3种养殖模式鱼塘沉积物中氯酚类(CPs)化合物的污染特征.结果表明,一般四大家鱼养殖模式(A)沉积物中总CPs质量分数(干质量)为9.91 ng·g-1,猪.鱼综合养殖模式(B)与鸭-鱼综合养殖模式(C)沉积物总CPs质量分数分别为7.79 ng·g-1和4.84 ng·g-1.总CPs及15种CPs化合物在A、B模式和鸭-鱼综合养殖模式(C)沉积物中的分布特征相似,质量分数由高到低的顺序为A模式,B模式,C模式.沉积物中质量分数比较高的一氯酚、二氯酚、三氯酚和四氯酚分别是4-CP、2,4-DCP、2,4,6-TCP和2,3,4,6-TeCP.五氯酚(PCP)质量分数与4-CP、2,5+2,6+3,5-DCP、3,4-DCP、2,4,5-TCP、2,3,6-TCP、2,3,4-TCP、2,3,5,6-TeCP、2,3,4,6-TeCP、2,3,4,5-TeCP等氯酚化合物质量分数显著正相关,显示PCP与它们之间存在降解物与产物的关系.参照美国EPA相关标准,上述鱼塘沉积物中的PCP和Ky氯酚(2,3,4,6-TeCP、2,4,6-TCP和PCP)导致生态风险的可能性较低. 相似文献
674.
After sepiolite was modified with Fe3+ to increase its surface charge, the initial algal removal rate increased significantly, but its Q8h was not improved substantially at clay loadings below 0.1 g/L. Modification on netting and bridging properties of clays by either chitosan or polyacrylamide (PAM) dramatically increased flocculation (Q8h) of MA cells in freshwaters. Algal removal efficiencies of different solids, including Type III clays, local soils and sediments, were all improved to a similar level of >90% at a total loading of 0.011 g/L (contained 0.001 g/L chitosan) after they were modified with chitosan, making the idea of clearing up algal blooms using local soils/sediments possible. The mechanism of netting and bridging was confirmed to be the most important factor in improving the removal efficiency of cells, whereas clays also played important roles in the sedimentation of the floc. 相似文献
675.
Nature reserves have developed rapidly over the decades in China and play a significant role in the function of ecosystem services. The function of ecosystem services in nature reserves, however, has tended to decline in recent years due to natural hazards and human activities. Based on land use, the variation of ecosystem services value (ESV) during 2000–2010 in national nature reserves in Sichuan was evaluated. We analyzed the comprehensive effects of natural disasters and human activities on the decline of ESVs. Total ESV in the national nature reserves in Sichuan was approximately 2741.35 million US$ in 2000, 2616.81 million US$ in 2005, and 2499.06 million US$ in 2010, representing a decrease of 242.29 million US$, or 8.84%, in the decade. Forestland, grassland, wetland, and water bodies played vital roles in the function of ecosystem services, with an aggregated ESV of 99% of the total. The largest proportion of the total ESV was the protection of biodiversity at 48.6%. ESV of all land use types and single ecosystem services continued to decline during 2000–2010. A mechanism of adaptable risk prevention should be established, and unreasonable human activities should be avoided to protect ecosystems and to improve the functions of ecosystem services. 相似文献
676.
有机锡致海洋腹足类性畸变分子机制的研究进展 总被引:1,自引:0,他引:1
有机锡作为防污损生物附着添加剂曾被大量使用,在极低浓度下就能诱发腹足类发生性畸变现象,严重危害了海洋生态系统的平衡。虽然三丁基锡已被国际海事组织全球禁用,但目前报道的环境有机锡污染仍然非常严重,而且其致毒机制一直众说纷纭。首先,简述了腹足类性畸变及其在世界各个海域有机锡污染监测中的应用,重点综述了有机锡致海洋腹足类性畸变分子机制的3种假说:脊椎动物类型的类固醇激素假说、神经肽假说以及视黄酸X受体(retinoid X receptor,RXR)假说,另外,结合快速发展的分子生物学技术,探讨了研究腹足类性畸变分子机制的新思路和新方法。 相似文献
677.
Zhengyan Wu Shuguang Jiang Hao Shao Kai Wang Xiaorui Ju Wei Zou Weiqing Zhang Lanyun Wang 《Safety Science》2012,50(4):660-667
In view of the invalidity of suppression and isolation apparatus for gas explosion, a closed vacuum chamber structure for explosion suppression with a fragile plane was designed on the base of the suction of vacuum. Using methane as combustible gas, a series of experiments on gas explosion were carried out to check the feasibility of the vacuum chamber suppressing explosion by changing methane concentration and geometric structure of the vacuum chamber. When the vacuum chamber was not connected to the tunnel, detonation would happen in the tunnel at methane volume fraction from 9.3% to 11.5%, with flame propagation velocity exceeding 2000 m/s, maximum peak value overpressure reaching 0.7 MPa, and specific impulse of shock wave running up to 20 kPa s. When the vacuum chamber with 5/34 of the tunnel volume was connected to the flank of the tunnel, gas explosion of the same concentration would greatly weaken with flame propagation velocity declining to about 200 m/s, the quenching distance decreasing to 3/4 of the tunnel length, maximum peak value overpressure running down to 0.1-0.15 MPa and specific impulse of shock wave below 0.9 kPa s. The closer the position accessed to the ignition end, the greater explosion intensity weakened. There was no significant difference between larger section and smaller vacuum chambers in degree of maximum peak value overpressure and specific impulse declining, except that quenching fire effect of the former was superior to the latter. The distance of fire quenching could be improved by increasing the number of the vacuum chambers. 相似文献
678.
679.
Laboratory experiments were conducted to examine the impact of cadmium (Cd) on survival of Diplostomum sp. cercariae. Freshly emerged cercariae were exposed to Cd solutions at concentrations ranging between 0.2 and 200 microg/l. The mortality patterns and mean survival times (MSTs) of the exposed parasites were determined by the Kaplan-Meier estimator and were compared (Log-Rank test) to corresponding patterns and estimators of the unexposed controls. Cd concentrations >20 microg/l caused statistically significant changes in the mortality pattern of Diplostomum sp. cercariae and reduced MST by at least five hours compared to the control group, where MST was 52 h. The results show that longevity of the free-living Diplostomum sp. cercariae can be reduced by direct exposure to heavy metals. Cd contamination of aquatic habitats thus potentially can have an impact on parasite populations and communities. 相似文献
680.
邹竞蒙 《中国人口.资源与环境》1994,4(1):54-57
大气层是全球环境各组成部分中最活跃的一个部分。全球及区域气候变异以及各种时空尺度的气象灾害如暴雨、台风、干旱、洪涝等,对社会经济发展的影响是全方位、多层次的。人类活动可能导致的气候变化对社会经济发展有着广泛性、长远性和深刻性的影响。因此讨论可持续发展问题,须对提高社会防御气象灾害和适应、减缓气候变化的能力问题予以特别的注意。 相似文献