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51.
小窑湾海水养殖环境现状的研究   总被引:6,自引:0,他引:6  
2000年3-11月对小窑湾水域质量进行了9航次10个指标的海上调查,结果表明该水域质量符合国家一类标准。叶绿素a值夏季高于冬季,IN值冬季高于夏季,COD值4、5、6月均值高出其他月份均值43个百分点,IP值上半年高于下半年。海区营养属贫脊型。同时揭示了高密度双壳贝类浮筏养殖对海区水质的负影响较小,该海域养殖贝类的死亡主要是因饥 饿引发的贝体较弱,抗病力较差。  相似文献   
52.
地质灾害生命损失灾情分析与对策   总被引:3,自引:0,他引:3  
地质灾害每年造成最大可能死亡1500-2000人,除内蒙古,天津市,江苏省,上海市,香港,澳门以外,其余28个省(市,区)每年因地灾害均有不同程度的人员伤亡,据统计,全国实际发生地质灾害死亡人数:1995年死亡1230人,1996年死亡51人,1997年死亡108人,1998年死亡532人,2000年死亡142人(伤26975人)。各级政府必须加强地质灾害防治,保障人民群众生命财产的安全。(1)地质灾害防治,政府负总责,建立和完善领导责任制。(2)制定地质灾害防治规划,实施规划管理,分期分批治理。(3)将地质灾害防治资金列入预算,并建立多元化投资机制。(4)工程建设必须进行地质灾害危险性评估,发生地质灾害造成重大损失的,追究地方政府主要领导和有关部门负责人的责任。  相似文献   
53.
Nest defence behaviours, such as attacking predators and defending against predator attacks, expose birds to risk of injury and death. However, direct costs of such behaviours are poorly documented. To evaluate potential costs of nest defence behaviours in lesser snow geese (Chen caerulescens), we (1) estimated the proportion of interactions between arctic foxes (Alopex lagopus) and geese that resulted in physical contact and (2) examined how nest defence behaviours varied between male and female geese. We separated interactions into attacks initiated by foxes (attacks by foxes) and attacks initiated by geese (attacks by geese). Risks associated with attacks by geese were considerably lower than the risks associated with attacks by foxes; only 1 of 1,179 attacks by geese resulted in physical contact between foxes and geese, whereas 26 of 89 attacks by foxes involved such contact (two female geese were killed during these attacks). Attacks by geese were made almost exclusively by male geese (>97%), whereas female geese were involved in 75% of all attacks by foxes that resulted in physical contact with geese. There was, thus, a considerable difference in risks associated with male and female nest defence behaviours. We suggest that parental roles during nesting (i.e., females incubate and males guard) expose female geese to greater risk of injury and death. Male geese may, however, reduce the risk of injury or death to their mates with pre-emptive attacks on foraging foxes.  相似文献   
54.
分别设定保定市2020年、2025年及2030年PM2.5浓度的不同目标情景,并考虑人口发展趋势,采用IER模型对各区县低、中、高目标情景下归因于PM2.5污染的过早死亡人数进行评估.结果表明,以2017年大气PM2.5浓度为基线,按照高中低3种预测情景,在2020年、2025年和2030年分别能避免的过早死亡人数高达1582~3840人、5244~7902人和12602~23558人,主要分布在市中心(莲池区、竞秀区和清苑区)及其东南区域.随着老龄化问题越来越严重,环境质量改善获得的健康收益愈加突出,心血管系统疾病(中风和缺血性心脏病)的归因死亡人数多于呼吸系统疾病(肺癌、慢阻肺疾病以及急性下呼吸道感染).当PM2.5浓度高于20μg/m3时,中风的归因死亡人数最高;当PM2.5浓度小于10μg/m3时,缺血性心脏病的归因死亡人数最高.建议保定市在制定PM2.5污染防控政策时重点关注人群密集的市区及东南方向地区,并考虑大气污染不同阶段导致的过早死亡疾病类型进行针对性的宣教和防控.  相似文献   
55.
Abstract:  We used historical patterns of deposition of mollusc shells to infer changes to inshore benthic assemblages in the southeastern Tasmanian region over the past 120 years. We identified and counted shells in slices embedded within 1m long 210Pb-dated sediment cores were collected at 13 sites in water depths of 8–16 m. Declines in mollusc species richness and shell production occurred during the past century at all sites studied, with a mean decline per 5-cm sediment slice from 21 species in 1890 to 7 species in 1990 and in shell abundance from 150 to 30 individuals over the same period. The time course of decline notably corresponded with the history of the scallop dredge fishery, presumably either because scallop dredging caused general declines in populations of mollusc species or because other factors caused a catastrophic regional decline in molluscs that included scallops. As a consequence, the fishery was forced to close. Of major concern is that losses had not previously been recognized but extended throughout the 100-km coastal span of the study. Given that fishing and other anthropogenic impacts, as well as a lack of observational data, are virtually ubiquitous for the coastal zone, major recent losses in mollusc biodiversity may be globally widespread but have gone unnoticed.  相似文献   
56.
57.
采用广义相加模型评估臭氧和细颗粒物(PM2.5)暴露对2008~2017年上海浦东居民慢性阻塞性肺疾病(COPD)死亡的超额危险度(ER)和寿命损失年(YLL)的影响.结果表明:臭氧污染集中在4~6月,PM2.5污染集中在12月、1~2月,10a间臭氧浓度逐年增加,PM2.5有小幅下降;在最大滞后效应下,臭氧每增加10μg/m3,ER和YLL分别为1.34%(95% CI:0.57%~2.12%)和54.98(95% CI:16.36~106.41)人·a;PM2.5每增加10μg/m3,两者分别为2.66%(95% CI:1.54%~3.79%)和130.92(95% CI:42.47~274.28)人·a;臭氧对男性和<85岁人群影响显著,PM2.5对女性和385岁人群影响显著;暖季时臭氧暴露相关的COPD死亡风险更高,冷季时PM2.5暴露相关的COPD死亡风险更高.臭氧和PM2.5致COPD死亡的影响可能因气温水平而异.  相似文献   
58.
李杰  丁奕  项荣  宋立荣 《生态环境》2010,19(11):2743-2748
浮游植物是水生生态系统的基础,在生物地化循环中起着非常重要的作用,浮游植物的死亡势必引起水生生态系统的改变。近年来的研究表明,浮游植物的死亡是浮游植物水华衰退的一个重要原因。浮游植物中是否存在与后生动物类似的程序性细胞死亡(Programmed cell death,PCD)途径,也因此成了一个热点问题。文章对近年来浮游植物死亡表型、PCD生化证据、诱发条件、分子基础方面研究进行了总结。大量证据表明,浮游植物中存在类似细胞凋亡、类凋亡、自噬等途径的PCD,但Caspase基因除具有死亡执行者功能外,还可能具有看家功能。活性氧(ROS)和一氧化氮(NO)在浮游植物PCD过程中可能起到死亡信号分子的作用。部分浮游植物的PCD可以改善种群生存,但其生态学意义总体而言仍存在许多争论。  相似文献   
59.
运用模拟试验的方法查清了一起CO中毒死亡事故的原因,查明了事故的直接责任者,确定了石灰窑停窑操作的关键步骤,为今后避免类似事故提供参考.  相似文献   
60.
The optimization of a water distribution network (WDN) is a highly nonlinear, multi-modal, and constrained combinatorial problem. Particle swarm optimization (PSO) has been shown to be a fast converging algorithm for WDN optimization. An improved estimation of distribution algorithm (EDA) using historic best positions to construct a sample space is hybridized with PSO both in sequential and in parallel to improve population diversity control and avoid premature convergence. Two water distribution network benchmark examples from the literature are adopted to evaluate the performance of the proposed hybrid algorithms. The experimental results indicate that the proposed algorithms achieved the literature record minimum (6.081 M$) for the small size Hanoi network. For the large size Balerma network, the parallel hybrid achieved a slightly lower minimum (1.921M€) than the current literature reported best minimum (1.923M€). The average number of evaluations needed to achieve the minimum is one order smaller than most existing algorithms. With a fixed, small number of evaluations, the sequential hybrid outperforms the parallel hybrid showing its capability for fast convergence. The fitness and diversity of the populations were tracked for the proposed algorithms. The track record suggests that constructing an EDA sample space with historic best positions can improve diversity control significantly. Parallel hybridization also helps to improve diversity control yet its effect is relatively less significant.  相似文献   
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