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21.
The Environmental Impact Statement (EIS) attempts to portray the current character of a given ecosystem. This provides a Baseline against which future possible changes can be assessed. Ecosystems, however, are dynamic and in a constant state of change. Consequently, data representing a single year reflect conditions only for that year and can be misleading if compared against any other year. In addition to this temporal variation, considerable spacial variation exists in species composition and cover. Ample sampling is required to compensate for this heterogeneity. Variation, or background noise, can be minimized by the use of similarity indexes and sampling over a period of at least two years. 相似文献
22.
报导了乌鲁木齐市两年内大气TSP中苯并(a)芘及碳质成分含量的分析结果、污染程度及变化规律,为乌鲁木齐城市环境综合整治定量考核,加强环境管理,进一步防治大气污染提供了科学依据. 相似文献
23.
A fuzzy logic approach has been developed to assess the groundwater pollution levels below agricultural fields. The data collected
for Kumluca Plain of Turkey have been utilized to develop the approach. The plain is known with its intensive agricultural
activities, which imply excessive application of fertilizers. The characteristics of the soils and underlying groundwater
for this plain were monitored during the years 1999 and 2000. Additionally, an extensive field survey related to the types
and yields of crops, fertilizer application and irrigation water was carried out. Both the soil and groundwater have exhibited
high levels of nitrogen, phosphorus and salinity with considerable spatial and temporal variations. The pollution level of
groundwater at several established stations within the plain were assessed using Fuzzy Logic. Water Pollution Index (WPI)
values are calculated by Fuzzy Logic utilizing the most significant groundwater pollutants in the area namely nitrite, nitrate
and orthophosphate together with the groundwater vulnerability to pollution. The results of the calculated WPI and the monitoring
study have yielded good agreement. WPI indicated high to moderate water pollution levels at Kumluca plain depending on factors
such as agricultural age, depth to groundwater, soil characteristics and vulnerability of groundwater to pollution. Fuzzy
Logic approach has shown to be a practical, simple and useful tool to assess groundwater pollution levels. 相似文献
24.
Number concentration and size distributions of submicron particles in Jinan urban area: Characteristics in summer and winter 总被引:1,自引:0,他引:1
GAO Jian WANG Jin CHENG Shu-hui XUE Li-kun YAN Huai-zhong HOU Lu-jian JIANG Yu-quan WANG Wen-xing 《环境科学学报(英文版)》2007,19(12):1466-1473
The aerosol number concentration and size distribution were measured with the newly developed Wide-range Particle Spectrometer in summer and winter of 2006 at the urban site of Jinan City.Here reported the characteristics of fine particles of the different observation seasons.Relative high number concentrations for the particles in the diameter range of 10-500 nm were observed in both seasons.It was found that the dominant number distributed in particle diameter smaller than 100 nm and the percentage over the number concentration of all air particles is much higher than what has been measured in other urban sites over the world.The number mean diameter in summer was much smaller than in winter,strongly suggesting the different origin of ultrafine particles in different seasons.That is, particles in ultrafine mode mainly came from nucleation and new particle formation in summer while from traffic emission in winter. The diurnal variation also supported this point.Number concentration in the diameter range of 10-200 nm got their peak values at noontime,well correlated with the mixing ratio of SO_2 and the intensity of solar radiation in summer.While in winter,those in the same diameter range showed the main peaks during the traffic hours happened in the morning and evening. 相似文献
25.
Ian Colbeck Zaheer Ahmad Nasir Shahida Hasnain Sikander Sultan 《Water, Air, & Soil Pollution: Focus》2008,8(1):61-69
In the developing world, the vast majority of people rely on solid biomass fuels for cooking and heating which results in
poor indoor air quality. The present study determined indoor air quality in some rural and urban areas of Pakistan. Measurements
were made of particulate mass (PM10, PM2.5 and PM1), number concentration and bioaerosols in different micro environments.
PM10 concentrations of up to 8,555 μg/m3 were observed inside the kitchens where biofuels were used as energy source. Cleaning and smoking was identified as a major
source of indoor particulate pollution and concentrations of more than more than 2,000 μg/m3 were recorded in the living room during these activities. Indoor number concentrations in Lahore were typically greater than
those observed outdoors in European cites. At a rural site the highest Colony Forming Units (CFUs) were in the 0.5 μm–2 μm
size fraction, while at the urban location CFUs were dominant for 2 μm–16 μm. It was observed that CFUs(Colony Forming Units)
counts were higher inside living rooms than kitchens. It is important to note that women and children were exposed to extremely
high levels of particulates during cooking. Overall, indoor air quality in Pakistan was poor and there is a dire need to take
a serious step to combat with it. 相似文献
26.
土壤重金属来源及空间分布是土壤学及环境学研究的热点问题。地统计学是土壤元素空间变异研究的有效方法以昆山市土壤重金属分布为例,先利用多元回归分析方法,提取与重金属含量显著相关的因子,再利用协同克里格方法研究了土壤理化性质和土壤重金属含量的相互关系,最后比较协同克里格与普通克里空间预测的精度。研究表明Hg、As、Cu、Pb的精度分别提高了2.75%、2.13%、0.17%和0.43%,cr、Zn和Cd 3种元素空间预测精度没有显著提高。 相似文献
27.
2012年6月13~14日对温州三垟湿地水质进行连续24h的采样监测,并运用对数型幂函数普适指数公式评价了监测站点1天内连续的水质变化情况。研究目的是揭示城市湿地水体中水质参数是否存在昼夜变化、昼夜变化的幅度大小和变化原因。结果表明:温度、pH、溶解氧、化学需氧量和叶绿素a表现出明显的昼夜变化,由于影响营养盐的因素复杂,营养盐指标没有表现出明显的昼夜变化。运用对数型幂函数普适指数公式评价监测站点的水质情况,评价结果显示在连续24h的实验中,水体的富营养化程度都处于"极富"营养状态而且呈现出白天营养状态综合指数下降,夜间升高的趋势。 相似文献
28.
29.
Dongliang Sun Juncheng Jiang Mingguang ZhangZhirong Wang Guangtuan HuangJianjiang Qiao 《Journal of Loss Prevention in the Process Industries》2012,25(1):114-126
More specific and accurate probabilistic models of the numbers of fragments generated respectively by Boiling Liquid Expanding Vapor Explosions (BLEVEs), Mechanical Explosions (MEs), Confined Explosions (CEs), and Runaway Reactions (RRs) of a horizontal cylindrical vessel were developed using the maximum entropy principle based on historical accident data. The theoretical results from the four probability density functions were compared to the observed data, and the numbers of fragments followed discrete exponential distributions in the interval [1, 9]. Beside the summary of the probabilistic distributions of the other random variables in the process of fragment projection, the effects on the fragment trajectory and target terms were investigated using a parametric approach. The results showed that using the complete model, wind shear, turbulence, and absence of fragment rotation caused the fragments to impact within shorter distances; fragment rotation and lack of wind decreased the probability of impact within a given distance, but the rupture probability of the target was not affected by fragment rotation or wind. The probabilistic confidence intervals of fragment range, impact, and target penetration became narrower with the number of simulation runs, but the accuracy of the results increased. The probability of fragment impact increased with the volume of the target vessel and the degree of filling of the explosion vessel, but did not depend on the kind of explosion. The probability of target rupture increased slowly with the degree of filling of the explosion vessel, but was little influenced by the volume of the target vessel or the kind of explosion. 相似文献
30.