东洞庭湖湖滨带土壤重金属健康风险评价

以东洞庭湖湖滨带为研究区域,系统调查分析其土壤中的重金属污染状况,并进行致癌风险评价和非致癌风险评价。东洞庭湖湖滨带土壤中的重金属As、Hg、Cd、Cu、Zn、Ni、Cr的平均含量分别为19.31、0.0113、0.989、50.29、125.7、43.9和93.36 mg/kg,已全部超过了洞庭湖背景值,其中As、Hg和Cd的最大含量分别已超过洞庭湖背景值的5倍、5倍和20倍之多,说明东洞庭湖湖滨带土壤已经受到一定程度的重金属污染。致癌风险评价结果表明,As为当地主要的致癌物,Cd属于安全的范围,叠加后的致癌总风险指数平均值成人的为1.6810-5,儿童的为1.0410-6,在鹿角港口区、岳阳市区和城陵矶港口区相对较高,是平均值的1.3至2.6倍。非致癌风险评价结果显示,Hg、Pb、Cu、Zn、Cr、Ni的非致癌风险指数均远小于1,不会对当地居民健康构成威胁。叠加后的非致癌总风险指数平均值成人的为1.7910-1,儿童的为1.0910-2,在漉湖芦苇场、团州农场、君山旅游区较高。     

基于DEM的西辽河流域河网水系提取研究

河网水系是对流域进行水文分析的重要数据,其生成的准确性会直接影响水文模型模拟的精度。以西辽河流域为研究区,在ARCGIS软件操作平台上对研究区的数字高程模型数据进行河网水系提取,设定不同的流域汇流累积阈值,分别计算出各模拟河网的分形维数及河网密度,取二者拟合趋势变化相同处阈值对应的河网与实际河网进行比较,发现此处的模拟河网与实际河网具有较高的拟合度,从而避免阈值确定的随机性、主观性等问题,有效地提高流域河网水系提取的精度。     

基于门限自回归的我国羊肉价格波动分析

羊肉价格的适度上涨会刺激我国羊肉产业的发展,但上涨过快,则会损害我国羊肉市场的稳定,对于政策制定者来说,确定羊肉价格大幅上涨的先期指标,以在恰当时机进行合理和适度地调控是非常必要的,可通过建立两体制TAR模型为政府实施调控的时机提供参考值.选取的羊肉月度价格时间序列样本区间为1994年6月至2014年2月,TAR模型估计结果表明,我国羊肉价格同比指数序列门限值为4.678,对应的价格同比指数为107.57％;如果羊肉价格同比指数高于107.57％,羊肉价格波动幅度将会增大,此时会对羊肉市场产生较大冲击,政府需要及时采取调控措施;如果羊肉价格同比指数低于107.57％,那么价格指数的波动相对较为稳定,此时政府不必采取调控措施.另外,政府在制定调控政策时还要充分考虑政策实施效果的时滞性,避免推动羊肉价格产生较大波动.     

Using the concept of ecological groundwater level to evaluate shallow groundwater resources in hyperarid desert regions

This paper,based on the analysis and calculation of the groundwater resources in an arid region from 1980 to 2001,put forward the concept of ecological groundwater level threshold for either salinity c...     

红三叶白粉病危害损失通径分析及经济阈值的数学模型

本文在红三叶白粉(Erysiphe Polygoni DC.)病情田间调查的基础上,分析了发病率、严重度、病情指数与产量损失之间线性关系,并由此建立了红三叶白粉病防治的经济阈值模型。这一模型可为当地红三叶白粉病的防治提供参考。     

模板法自动提取遥感图像耕地变化信息的研究

该文在多时相遥感图像中采用主成份差异法提取耕地变化信息，研究的关键在于差值前如何进行图像匹配、如何自动提取变化信息以及差值后如何确定变化阈值。在逐像元判断是否变化时，根据计算机视觉的数据处理思想提出一种采用(2n+1)×(2n+1)判断模板进行判断的方法，这种方法可以大幅度地改善单像元判断的效果。经试验，提取耕地变化信息的准确程度达85％以上，可以替代人工判读的工作。     

Integrating effects of hunting policy, catastrophic events, and inbreeding depression, in PVA simulation: the Scandinavian wolf population as an example

Focusing on the wolf Canis lupus in Scandinavia as an example, criteria are proposed and an analysis performed to assess the effect on extinction risk of various control policies, while accounting simultaneously for effects of inbreeding depression and potential catastrophic events. Each control policy is characterized by a hunting pressure (the increase caused by hunting of annual mortality rates) combined with a hunting threshold (the population size below which hunting is not permitted). Catastrophes are taken into account by including the persistence of a severe catastrophe in the criterion for population viability. Based on these criteria, the results suggest that only a very limited amount of hunting should be permitted at low population sizes. The results also illustrate the importance of including a long-term perspective in modelling threatened populations.     

Surface ozone concentrations and exposures during growing season at the Lithuanian rural site

The surface ozone (O₃) data show an increase by 2.6 % per year during the period 1982–1994 at the rural site of Lithuania. WHO (World Health Organization), UN-ECE (United Nations Economic Commission for Europe), CES (Commission of the European Communities) guideline values for the protection of vegetation from adverse effects are exceeded during the growing season at the Preila coastal station. Ozone exposures for different concentration threshold are estimated during daylight hours in April-September. These values above 60 g/m³ varied between 10 000 and 43 000 (g/m³) ·h, above 80 g/m³ — between 1700 and 15 000 (g/m³) ·h, above 100 g/m³ — between 130 and 3700 (g/m³) ·h during separate years. Maximum hourly ozone values were observed from 116 to 228 g/m³ during this period.     

深圳市不同城市密度区中环芳烃的发生、来源及生态风险评估

Urbanization may cause increased exposure levels to polycyclic aromatic hydrocarbons(PAHs) and associated health risks for over half of the world's population living in cities,but little evidence has shown a direct spatial relationship between urbanization and soil PAH pollution.Based on the monitored PAH concentrations in 188 topsoil(0-5 cm) samples in Shenzhen,the most rapidly developing city in China,in recent decades,we applied geographical demarcation to determine the occurrences,source apportionments,and spatial ecological risks of soil PAHs across five zones of varying urban densities.Mean concentrations of the 16 US Environmental Protection Agency(EPA) priority PAHs(Σ_(16)PAHs) and the 7 carcinogenic PAHs(Σ_7CarPAHs) both followed the order:Zone D(60%-80%constructive land density(CLD)) Zone E(80%-100%CLD) Zone C(40%-60%CLD) Zone B(20%-40%CLD) Zone A(0%-20%CLD),suggesting that the highest PAH levels occurred in the suburban-urban center transitional zone(Zone D) rather than the urban center zone(Zone E) in Shenzhen.There were significant correlations of Σ_(16)PAHs to TOC and sampling altitude across all samples but not within highly-urbanized regions(Zones D and E),implying a considerable disturbance of urbanization to the soil PAH pool.Source apportionments suggested that soil PAHs of all zones were mainly derived from fossil fuel combustion,with Zone E showing the highest contribution from oil sources among different zones.Spatial ecological risk analysis showed that the contaminated area(467 km~2;23.9%of total area;toxic equivalency quotients 33 ng g~(-1)) had a higher contribution from the highly-urbanized regions(Zones D and E) than the uncontaminated area(42.3%vs.18.1%).Overall,our study highlighted a strong spatial relationship between urbanization and soil PAH pollution.