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Seasonal variations of monocarbonyl and dicarbonyl in urban and sub-urban sites of Xi’an,China 总被引:1,自引:0,他引:1
K. F. Ho Steven Sai Hang Ho W. T. Dai J. J. Cao Ru-Jin Huang Linwei Tian W. J. Deng 《Environmental monitoring and assessment》2014,186(5):2835-2849
Seventeen airborne carbonyls including monocarbonyls and dicarbonyls were determined in urban and sub-urban sites of Xi’an, China in three seasons in 2010. In winter, acetone was the most abundant carbonyl in the urban site due to usage of organic solvents in constructions and laboratories and its slower atmospheric removal mechanisms by photolysis and reaction with hydroxyl radical than those of formaldehyde and acetaldehyde. In the sub-urban site, acetaldehyde was the most abundant carbonyl, followed by formaldehyde and acetone. During summer, however, formaldehyde was the most dominant carbonyl in both sites. The photooxidations of a wide range of volatile organic compounds (VOCs) yielded much more formaldehyde than other carbonyls under high solar radiation and temperature. In the urban site, the average concentrations of dicarbonyls (i.e., glyoxal and methyglyoxal) in spring and summer were higher than that in winter. Transformation of aromatic VOCs emitted from fuel evaporation leads to the formation of 1,2-dicarbonyls. A reverse trend was observed in sub-urban sites, as explained by the relatively low abundances and accumulations of VOC precursors in the rural atmosphere during warm seasons. Moreover, cumulative cancer risk based on measured outdoor carbonyls (formaldehyde and acetaldehyde) in Xi’an Jiaotong University and Heihe was estimated (8.82?×?10?5 and 4.96?×?10?5, respectively). This study provides a clear map on the abundances of carbonyls and their source interpretation in the largest and the most economic city in Northwestern China. 相似文献
114.
Li Zhang Dawen Zhang Yihua Wei Linguan Luo Tingcan Dai 《Environmental monitoring and assessment》2014,186(4):2185-2194
The levels of trace elements (As, Cd, Cr, Cu, Fe, Ni, Pb, Se, and Zn) in eight species of cultured freshwater fishes from Jiangxi province were determined by inductively coupled plasma-mass spectroscopy. All the studied trace element levels in fish muscles from Jiangxi province did not exceed Chinese national standard and European Union standard, and they were often lower than previous studies. The calculated target hazard quotient values for all the studied trace elements in fish samples were much less than 1, suggesting that the studied trace elements in fish muscles from Jiangxi province had not pose obvious health hazards to consumers. As and Cd concentrations in northern snakehead were much higher than that in other fishes, demonstrating that this fish species could be valuable as a bioindicator of As and Cd in environmental surveys. In addition, the highest concentrations of Fe, Zn, and moderate contents of other essential trace elements in crucian carp indicated that crucian carp could be a good nutrient source of essential trace elements for human health. 相似文献
115.
Green vegetation cover fraction (VCF) is an important indicator of vegetation status in ecology and agronomy. Digital image analysis (DIA) has been widely accepted as a new VCF measurement technique. In this study, we present a novel fully automatic threshold segmentation algorithm for VCF measurements, which is named as upper inflection point plus mean gradient magnitude of edge pixels (UIP-MGMEP). The algorithm performs VCF estimation upon the vegetation index Excess Green (EXG). UIP-MGMEP optimizes the EXG threshold by searching the upper inflection point (UIP) of the M-Et curve (mean gradient magnitude of edge pixels (MGMEP) vs. EXG threshold), based on the assumption that EXG variance of the boundary pixels between vegetation and background is larger than the variance of the background. Five typical sample images are used to illustrate how ground complexity reduces the distinctness of the UIP. Three controlled experiments are illustrated to test the robustness of UIP-MGMEP to resolution, exposure, and ground complexity. The results show that UIP-MGMEP is a promising algorithm for automatic VCF estimation upon digital images. Compared to broad-leaved grass, narrow-leaved grass is more sensitive to resolution and exposure. To reduce ground complexity, smaller footprint size while more images to cover the same area may be better than one image with large footprint size. UIP-MGMEP is fully automatic, making it promising for batch processing of VCF measurements that is very difficult in any wide-range field survey in the past. UIP-MGMEP algorithm can only extract green vegetation and is not suitable for non-green (even grayish-green) vegetation, due to the limits of vegetation index EXG. In addition, UIP-MGMEP is not recommended for images with VCF less than 0.5% or greater than 99.5%. 相似文献
116.
Huang Shaojian Dai Chunhao Zhou Yaoyu Peng Hui Yi Kexin Qin Pufeng Luo Si Zhang Xiaoshan 《Environmental science and pollution research international》2018,25(17):16548-16566
Environmental Science and Pollution Research - Plant leaves play a key role in the accumulation of PAHs, as they are able to capture PAHs from the air. In this paper, the mechanism, including... 相似文献
117.
为了评价并进行城市水环境质量考核排名,介绍了江苏省组织开展涵盖地表水、饮用水、地下水、近岸海域和城市内河5种类型"全要素、代表性"水质监测断面(点位)体系建设工作的情况以及全要素断面设置的基本原则和做法。分苏南、苏北、苏中3个区域,对全省地表水监测代表性进行了量化计算,结果表明,调整后全省水质综合指数极差从41.07降至7.17,标准差从3.16降为0.49;采用德尔斐层次分析法分析,设计了水质代表性指数,含1项一级指标、5项二级指标、12项三级指标,计算表明,调整前全省水质代表性指数得分为69.1分,调整后为88.7分。将调整结果进行论证后再与各市环保主管部门交换意见,取得最终一致后正式实施。 相似文献
118.
全国大气背景地区黑碳浓度特征 总被引:1,自引:0,他引:1
分析了2015年14个背景站黑碳浓度水平及分布规律,结果表明:我国背景地区黑碳小时浓度均值呈现明显的对数正态分布特征,14个背景站880 nm波长时年均质量浓度为88.7~1 487.6 ng/m~3,小时最大峰值为685.0~13 731.0 ng/m~3,长岛和衡山相对较高;24 h日浓度变化基本呈现"单峰"状,但峰值出现时刻有所不同;工作日和周末的浓度变化趋势基本相似,但浓度高低与所在区域生产生活方式不同而有所差异。初步探讨了风速和风向与浓度污染水平的关系,相对风速而言,风向对黑碳的浓度影响较大,后向轨迹结果也印证了风向的影响。 相似文献
119.
利用2013-2017年京津冀区域13个城市PM2.5监测数据,综合探讨了该区域PM2.5浓度的时空变化特征。结果表明:京津冀区域PM2.5污染整体较重,但治理成效显著,2013-2017年区域PM2.5年均质量浓度分别为106、93、77、71、64 μg/m3,完成《大气污染防治行动计划》PM2.5浓度下降25%左右的目标;13个城市PM2.5浓度各百分位数总体呈现下降趋势,且随百分位数增大而下降速率加大,PM2.5年均质量浓度平均每年下降10.6 μg/m3,污染严重的太行山沿线城市邢台、石家庄、邯郸3个城市平均每年分别下降20.3、16.1、13.9 μg/m3;京津冀区域PM2.5重度污染天数比例分别为19.9%、16.6%、9.5%、9.0%、7.0%,呈下降趋势。2013-2017年京津冀区域PM2.5平均质量浓度与非重度污染天相比升高19 μg/m3,PM2.5重度污染天平均质量浓度较非重度污染天时高244.4%。 相似文献
120.
建立了硝酸加热消解后采用电感耦合等离子体发射光谱(ICP-OES)测定石化废水中重金属(As,Cd,Cr,Cu,Zn,Pb,Mn)的方法,优化了仪器工作参数,得到了线性回归方程,并对该方法进行了评价。优化后的仪器工作参数为射频功率1 150 W、雾化器流量0.70 L/min、辅助气流量0.50 L/min。各重金属元素回归方程的相关系数均在0.999 9以上,检出限为0.000 18~0.007 00 mg/L,相对标准偏差为0.1%~2.0%,加标回收率为96.3%~102.2%。该方法具有线性关系好、检出限低、精密度和准确度高、分析速度快等优点。 相似文献