排序方式: 共有51条查询结果,搜索用时 265 毫秒
31.
32.
33.
基于分形维数权重的南水北调东线源头水质评价研究 总被引:1,自引:0,他引:1
水质评价问题的实质是对水质现状和各评价因素间的函数关系的逼近,是一种复杂的非线性问题.针对水质评价指标之间的非线性关系,提出了基于分形维数权重的水质评价方法.为有效地评估南水北调东线源头的水质现状,首先选取影响水质评价的7个主要因素,根据标准等级水体分类标准,采用在等级标准中随机内插的方法,得到50个标准等级样本,并根据样本综合评估值与经验等级之间的关系建立分形插值评价模型;最后,以长江江都市芒稻河断面2001—2008年的年平均水质监测数据为例对模型进行验证.结果表明,该方法可以通过分段函数得到每个样本的具体得分值,因而具有较高的分类精度,为水质评价提供了一种较好的新方法. 相似文献
34.
35.
我国是个多山的国家,山地、丘陵和高原占全国总面积的1/3,一般都存在着不同程度的地质灾害。2002年全国共发生滑坡、崩塌、泥石流、地面沉陷等突发性的地质灾害4.8万余起(重大地质灾害333起),其中滑坡数量最多约占84.3%,其次是崩塌和泥石流,分别占6.6%和6.0%。造成962人死亡,1797人受伤,直接经济损失近51亿元。 相似文献
36.
为探明高海拔矿山井下作业环境对安全人因指标影响规律及致因过程,基于安全工程学原理与正交分析理论,借助高海拔环境模拟试验系统,开展单因素及正交复合因素试验,分析安全人因指标与矿山环境参数定量关系,并利用统计分析软件SPSS进行多元回归分析,构建高海拔矿山恶劣环境条件下各安全人因指标动态预测模型,通过与实测数据比对,验证模型可靠性。结果表明:人因指标动态预测模型可以有效预测高海拔矿山井下作业人员安全人因指标变化规律;氧分压、温度、湿度3项环境因素对安全人因指标存在交互影响作用。研究结果可为高海拔矿山安全生产提供理论依据。 相似文献
37.
青霉菌P-93对偶氮染料的降解特性研究 总被引:4,自引:2,他引:4
采用富集培养的方法,从土壤中分离得到一株对偶氮染料酸性大红(GR)和酸性黑(ATT)有较强脱色能力的青霉菌P-93(Penicilliumsp.P-93)。该菌以GR和ATT作为唯一C源和唯一N源均能生长。P-93在pH4.0─8.0的范围内对ATT的脱色率都在80%以上,在28-37℃的温度范围内对GR和ATT的脱色率也都超过80%。对降解产物的紫外─可见光光谱分析表明,对GR和ATT在可见光区的吸收峰(487.1nm,486.2nm和596.5nm)明显消失,而在紫外区的光吸收有所加强。P-93中降解GR和ATT的酶主要存在于细胞内,其生物合成不受染料的诱导。 相似文献
38.
利用高时空分辨率的ERA-Interim资料,结合环保局空气质量监测数据,分析了1000 m以下低层大气扩散能力和大气层结条件对浙江省大气环境质量的可能影响.结果表明:浙江省700 m以下的大气扩散能力对全省大部地区的空气质量有明显影响,部分地区700~1000 m的大气扩散能力对空气质量也有一定的影响.但位于沿海的舟山,仅300 m以下的大气扩散能力对空气质量有显著的影响.将低层大气扩散能力分别与逆温层高度、空气质量做相关性分析,结果显示通过显著性检验的影响区域和影响高度有很好的一致性,说明三者之间存在密切的联系.逆温层高度越低,低层大气扩散能力越弱,空气质量越差,严重污染天气出现时常常伴随着强度较强或贴近地面的逆温发生.浙江省大气层结大部分时间处于中性状态,当大气层结转为较稳定时,污染物不易扩散稀释,空气污染较易发生. 相似文献
39.
Guoying Wang Shiming Ji Ruihong Li Shangrong M Xuefu Chen Zhijun Wu Gaofeng Shi Xiuli Niu 《环境科学学报(英文版)》2020,32(9):58-64
Hydroxyl free radicals (OH radicals) play the main role in atmospheric chemistry and their involving reactions are the dominant rate determining step in the formation of secondary fine particulate matter and in the removal of air pollutants from the atmosphere. In this paper, we studied the seasonal variation characteristics of OH radicals during the daytime in Lanzhou and explored the potential formation mechanism of high concentration OH radicals. We found that the OH radicals in four seasons was 2.7 × 106, 2.6 × 106, 3.1 × 106, and 2.2 × 106 cm?3, respectively. Since the rainfall was concentrated in summer, the wet deposition had a significant effect on removing OH radicals. Among the four pollutants (including ozone (O3), volatile organic compounds (VOCs), nitrogen dioxide (NO2) and fine particulate matter (PM2.5)), the variation of OH radicals were closely related to ozone concentration especially in spring and summer. In autumn, the correlation between PM2.5 and OH radicals were the closest among the observing pollutants and its formation mechanism was different conventional regeneration pathway. In Event 1, high concentration of ozone was the main source of OH radicals; under the high humidity condition, except for ozone, the multiple factors including VOCs, NO2 and PM2.5 interplayed and leaded to the Event 2. 相似文献
40.
Levels of synthetic musk fragrances in human milk from three cities in the
Yangtze River Delta in Eastern China 总被引:2,自引:0,他引:2
Xiaolan Zhang Gaofeng Liang Xiangying Zeng Jing Zhou Guoying Sheng Jiamo Fu 《环境科学学报(英文版)》2011,23(6):983-990
Synthetic musks are used as additives in many household products. After absorption into the human body, they accumulate and
their concentrations in human milk reflect both the mother and her infant’s exposure level. Concentrations of four synthetic musks,
musk xylene (1-tert-butyl-2,6-dimethyl-2,4,6-trinitrobenzene, MX), musk ketone (4-tert-butyl-2,6-dimethyl-3,5-dinitroacetophenone,
MK), 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta[
]-2-benzopyran (HHCB) and 7-acetyl-1,1,3,4,4,6-hexamethyl-1,2,3,4-
tetrahydronaphthalene (AHTN), were determined in human milk samples collected from Shanghai, Wuxi, and Shaoxing in Eastern
China. The four synthetic musks were found in most samples analyzed, with HHCB the dominant component followed by MX. The
median (mean) values for HHCB, AHTN, MX and MK concentrations were 63 (82), 5 (12), 17 (24) and 4 (9) ng/g lipid weight,
respectively. These data suggested the total synthetic musk contamination was low, and the distribution percentage was HHCB > MX
> AHTN MK. The relative high ratio of nitro to polycylic musk indicated that nitro musks were still widely used. The musk
concentrations in these cities were not significantly different from each other (p > 0.05). Principal components score plots were
obtained, which showed similar exposure sources. The amount of total synthetic musks in human milk were not associated with
mother’s age, although HHCB was significantly correlated with AHTN (p < 0.05). Daily ingestion of HHCB, AHTN, MX and MK for
infants from human milk were estimated as (2526 2926), (370 524), (7391 832), and (277 462) ng/day, respectively. Those
doses were 1–2 orders of magnitude below the provisional tolerable daily intakes. 相似文献