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251.
Knowledge of particle number size distribution(PND) and new particle formation(NPF)events in Southern China is essential for mitigation strategies related to submicron particles and their effects on regional air quality,haze,and human health.In this study,seven field measurement campaigns were conducted from December 2013 to May 2015 using a scanning mobility particle sizer(SMPS) at four sites in Southern China,including three urban sites and one background site.Particles were measured in the size range of15-515 nm,and the median particle number concentrations(PNCs) were found to vary in the range of 0.3× 10~4-2.2 × 10~4 cn~(-3) at the urban sites and were approximately 0.2 × 10~4 cm~(-3) at the background site.The peak diameters at the different sites varied largely from 22 to 102 nm.The PNCs in the Aitken mode(25-100 nm) at the urban sites were up to 10 times higher than they were at the background site,indicating large primary emissions from traffic at the urban sites.The diurnal variations of PNCs were significantly influenced by both rush hour traffic at the urban sites and NPF events.The frequencies of NPF events at the different sites were0%-30%,with the highest frequency occurring at an urban site during autumn.With higher SO_2 concentrations and higher ambient temperatures being necessary,NPF at the urban site was found to be more influenced by atmospheric oxidizing capability,while NPF at the background site was limited by the condensation sink.This study provides a unique dataset of particle number and size information in various environments in Southern China,which can help understand the sources,formation,and the climate forcing of aerosols in this quickly developing region,as well as help constrain and validate NPF modeling.  相似文献   
252.

基于川南城市群空气质量指数(AQI)数据和NECP/NCAR再分析资料,结合年内分配不均匀系数(CV),分析了该地区2020年空气质量变化特征及其与大气环流间的联系。结果表明:1)川南城市群AQI整体呈年内下降趋势,夏、秋季空气质量好于春、冬季;CV轻微上升,表明年内空气质量分配不均匀状态增大,其中冬季空气质量分配差异最大,夏季差异最小,川南西部地区差异大于东部地区。2)受首要污染物PM2.5影响,AQI空间上呈中部高四周低的分布形式,加之PM10的影响,AQI空间分布有明显的季节差异性。春、冬季AQI空间分布特征较为相似,形成中部高值区和北部低值区;夏季分布西高东低,秋季为东南高西北低。3)川南城市群春、冬季处于高空槽后,冷空气的堆积不利于对流发生,污染物排出不畅,使得AQI较高;夏、秋季则由于副热带高压和中高纬低槽的存在易产生对流而发生降水,加之风场辐合形势较明显,污染物不易积聚,因此AQI较低。

  相似文献   
253.
Wrathall JE 《Disasters》1985,9(2):104-114
The annual hazard of fire in the forest, maquis and garrigue of southern France is related both to the fragile nature of the Mediterranean ecosystem and to man's activities. The Mediterranean vegetation is adapted to withstand the aridity of the summer months, but the combination of high temperatures, low precipitation, critical soil-moisture levels and occasional bouts of strong winds (mistral) desiccate the vegetation cover and create conditions in which outbreaks of forest fires are inevitable. Although the annual incidence and impact of forest fires are related to the occurrence of extreme weather conditions they are also exacerbated by depopulation of the remoter rural areas, the spread of urbanization and the growth of tourist facilities in the more accessible coastal zones, and above dl by man's carelessness. This article reviews the factors affecting the nature and severity of forest fires and discusses the attempts being made to prevent and control forest fires in the Mediterranean zone of southern France  相似文献   
254.
分析了南方季节性干旱的特征、成因和抗旱体系。其特征是干旱出现的频率与强度加大,表土干旱和干热同步。成因是降水量、蒸发量年分布在时间序列上不同步;红壤调控供水力弱、有效水少和生物耗水多、供需矛盾突出。关键对策是建立开源节流为主体、降耗增效为两翼的抗旱技术体系。  相似文献   
255.
Reproductive effort is a key parameter of life history because it measures the resources allocated to reproduction at the expense of growth and maintenance. Male reproductive effort always had a minor role with respect to female effort both in the development of theories and in field research. Elephant seals are an ideal subject for reproductive effort studies because they fast during the breeding season, splitting the phase of energy acquisition from the phase of energy use for breeding. In this paper, we present results on male reproductive effort (weight loss estimated by photogrammetry) in southern elephant seals (Mirounga leonina), the most dimorphic and polygynous of all mammal species. We show that total reproductive effort increases with age, with no sign of late decrease or senescence. Male reproductive effort in this species depends mostly on behavioral factors, i.e., the success in competition with other males, and the intensity of interaction with females. A large effort results in large gains in both mating success and fertilizations. The large reproductive success that a few males are able to achieve come at a big cost in terms of energy expenditure, but this cost does not seem to affect the likelihood of survival to the following breeding season.  相似文献   
256.
东苕溪蓝藻时空分布及其与环境因子关系研究   总被引:2,自引:0,他引:2  
研究了东苕溪(太湖主要入湖河流)秋季和春季浮游植物的空间分布格局,监测了东苕溪18个采样点的浮游植物叶绿素a含量、细胞密度及种类组成等指标,分析了影响蓝藻时空分布差异的环境因子.结果表明:调查期间,共观察到浮游植物8门60属132种,其中,蓝藻门9属14种,蓝藻细胞密度占浮游植物细胞密度的平均比例为60.3%,蓝藻细胞密度自东苕溪下游至上游呈减小趋势,最高值出现在东苕溪下游距南太湖湖口3km以内.在秋季,东苕溪下游以铜绿微囊藻(Microcystis aeruginosa)为优势种,春季为水华鱼腥藻(Anabaena flos-aquae);丝状蓝藻(小席藻)是上游的优势代表种.东苕溪下游蓝藻的绝对优势与特殊的水动力条件、高浓度的营养盐有关.相关性分析表明,蓝藻细胞密度与水深(p<0.01)、总氮(p<0.01)和溶解性总碳(p<0.05)呈显著正相关.  相似文献   
257.
Prenatal diagnosis was attempted in a pregnant Japanese woman whose son had died of infantile hypophosphatasia, using chorionic villi sampled at 10 weeks of gestation. Southern blot analysis of restriction fragment length polymorphism was used as a guide, with cDNA for the human liver-type alkaline phosphatase as a probe, and BclI as a restriction enzyme. The fetus was found to be a heterozygote; the pregnancy was allowed to continue; and the baby born was phenotypically normal.  相似文献   
258.
自然灾害综合性评价与分区是防、减、治灾的基础。本文提出的自然灾害综合评价模型,考虑了各种自然灾害的共同作用和受灾区域的社会经济水平,用自然灾害综合指数来表示区域自然灾害的危险程度,并据此作综合分区。  相似文献   
259.
皖南地区具有独特的地理位置,自然景观和人文景观相互交融,其旅游资源的特色是景区分布集中(稀有性)、景观类型多样(珍贵性)、文化古迹丰富(徽文化发源地),旅游资源还具有自然风光、人文景观、生态环境的优势,具有综合开发利用各类旅游资源的可行性与必要性。通过系统调查和分析该地区旅游资源的配置基础,提出了对该地区的旅游资源进行综合开发的建议。  相似文献   
260.
/ For regional analyses of species imperilment patterns, data on species distributions are available from the U.S. Fish and Wildlife Service and from the state heritage programs. We compared these two different databases as sources of best available information for regional analyses of patterns of aquatic species imperilment for 132 counties in the southern Appalachians and examined patterns produced from the databases. The heritage program database contained information about a greater number of imperiled species because species need not be federally listed as threatened or endangered to be included in this database. In the southern Appalachians, about half of imperiled molluscs and about one-fourth of imperiled fish were listed as threatened or endangered; much smaller proportions of other taxonomic groups were federally listed. Most threatened and endangered species appeared on both lists, but for about 40% of the species inconsistencies exist, notably a lack of recent records in the heritage program dataset. Numbers of species in each county were significantly different between the two datasets for Georgia, Tennessee, and Virginia, where the largest number of threatened and endangered species reside. Nevertheless, some counties always appeared as centers of imperilment, and the general spatial patterns of imperilment were similar.  相似文献   
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