季节趋势模型在气体泄漏扩散模拟预测中的应用

基于江苏工业学院油气储运安全综合实验模型平台,利用示踪技术,模拟了有害气体瞬时泄漏扩散的整个过程。结合趋势季节模型,以六号探头为研究对象,利用指数平滑法,进行时间序列预测,得到下一个时间段的有害气体扩散数据。研究表明泄漏物质浓度有下降的趋势,模型输出结果较好,拟合度高,一定程度上反映了泄漏后有害气体未来的扩散趋势。该研究结果对泄漏事故扩散趋势做出准确的预测,对建立有针对性的应急救援预案,实施有效的现场控制,具有一定的科学参考价值。     

APPLICATION OF THE RHESSys MODEL TO A CALIFORNIA SEMIARID SHRUBLAND WATERSHED1

ABSTRACT: Distributed hydrologic models which link seasonal streamflow and soil moisture patterns with spatial patterns of vegetation are important tools for understanding the sensitivity of Mediterranean type ecosystems to future climate and land use change. RHESSys (Regional Hydro‐Ecologic Simulation System) is a coupled spatially distributed hydroecological model that is designed to be able to represent these feedbacks between hydrologic and vegetation carbon and nutrient cycling processes. However, RHESSys has not previously been applied to semiarid shrubland watersheds. In this study, the hydrologic submodel of RHESSys is evaluated by comparing model predictions of monthly and annual streamflow to stream gage data and by comparing RHESSys behavior to that of another hydrologic model of similar complexity, MIKESHE, for a 34 km² watershed near Santa Barbara, California. In model intercomparison, the differences in predictions of temporal patterns in streamflow, sensitivity of model predictions to calibration parameters and landscape representation, and differences in model estimates of soil moisture patterns are explored. Results from this study show that both models adequately predict seasonal patterns of streamflow response relative to observed data, but differ significantly in terms of estimates of soil moisture patterns and sensitivity of those patterns to the scale of landscape tessellation used to derive spatially distributed elements. This sensitivity has implications for implementing RHESSys as a tool to investigate interactions between hydrology and ecosystem processes.     

中国荒漠化气候类型划分方法的初步探讨

在同一气候资料的基础上 ,分别应用Thornthwaite公式和Penman公式计算了潜在蒸散 ,并据此计算湿润指数 ,划分了我国的荒漠化气候类型区 ,并确定了荒漠化潜在发生范围 ,同时对上述两种方法在我国荒漠化气候类型区划中的适用性进行了比较分析。结果表明 ,对我国而言 ,Penman公式法比Thornthwaite公式法更具有合理性。根据Penman公式法的区划结果 ,我国荒漠化潜在发生范围约为4 2 4万km2 ,占国土面积的 4 4 .1% ,分布于全国 19个省 (自治区、直辖市 )。     

VIRGINIA USA WATER QUALITY, 1978 TO 1995: REGIONAL INTERPRETATION1

ABSTRACT: Nine surface water‐quality variables were analyzed for trend at 180 Virginia locations over the 1978 to 1995 period. Median values and seasonal Kendall's tau, a trend indicator statistic, were generated for dissolved oxygen saturation (DO), biochemical oxygen demand (BOD), pH (PH), total residue (TR), nonfilterable residue (NFR), nitrate‐nitrite nitrogen (NN), total Kjeldahl nitrogen (TKN), total phosphorus (TP), and fecal coliform (FC) at each location. Each location was assigned to one of four physiographic regions, and mean state and regional medians and taus were calculated. Widespread BOD and NFR improvements were detected and FC improvements occurred in the state's western regions. TR and TKN exhibited predominantly increasing trends at locations throughout the state. BOD, TKN, NFR, and TR medians were higher at coastal locations than in other regions. NN, TKN, and TR exhibited predominantly increasing trends in regions with high median concentrations, while declining trends predominated in regions with relatively high BOD, FC, and NFR medians. Appalachian locations exhibited the greatest regional water‐quality improvements for BOD, FC, NFR, and TKN. Factors responsible for regional differences appear to include geology, land use, and landscape features; these factors vary regionally.     

Hydrologic Effects of NDVI Time Series in a Context of Climatic Variability in an Upstream Catchment of the Minjiang River1

Abstract: Increasing regional vegetation activity has been frequently found especially in middle and high latitude and alpine areas, but the effects of which on regional hydrology is still highly uncertain. The Upstream Catchment of Minjiang River is a large mountainous catchment covering 22,919 km² with a diverse vegetation distribution pattern, including alpine group (A), subalpine group (SA), and temperate and subtropical group (T/ST). The Seasonal Mann‐Kendall test, a nonparametric trend test method, detected consistent upward trends in all groups in monthly accumulated growing degree days (AGDD_M) time series from 1982 to 2003, but no significant trend in mean monthly precipitation (MMP) time series in any group. The alpine group had a significant (p = 0.024) upward trend in monthly Normalized Difference of Vegetation Index (NDVI) time series from 1982 to 2003, in contrast, the SA and T/ST groups had decreasing (although not significant) trends. AGDD_M plays more important role than MMP in affecting NDVI change in alpine areas, indicating temperature was the main climatic driver. In contrast, water was the main driver for the T/ST group, as indicated by the significant correlation between NDVI and MMP and a weak correlation with AGDD_M. Correlation coefficients of NDVI and river flow varied with seasons, mostly negative, especially during the growing season (April to October). A significant (p = 0.025) correlation was found only in August, indicating that an increase in peak‐NDVI decreased high flow significantly. TI‐NDVI_c, which was developed in an attempt to track the vegetation change at the catchment scale, accounted for more than 40% of the evapotranspiration increase (r² = 0.43).     

基于精细观测资料的深圳不同季节霾及其污染特征分析

利用2010~2013年逐时霾、能见度和空气质量监测数据,分析了深圳霾天气的变化特征、霾与空气质量和气象条件的关系.结果表明:深圳市霾日数总体呈现增多增强趋势,2009年开始明显下降;霾日数呈“V”型月变化:即秋冬季多、春夏季少,秋冬季多发持续时间长、影响严重的霾过程,春夏季多发持续时间短的霾过程; 霾常伴有污染发生(35%),污染以轻度污染为主;霾时首要污染物PM2.5最多、其次O3,这说明PM2.5是造成深圳霾的主因,且深圳光化学污染严重. 霾时PM2.5、PM10 和O3季节变化明显,冬春季首要污染物以PM2.5为主(75%以上),夏秋季O3和PM2.5为主;分析还发现,风、相对湿度与霾密切相关,风速越弱,湿度越大, 越利于霾出现和发展.约80%的中重度霾出现在风速<2m/s,相对湿度70%~90%的情况下.     

南京地区大气气溶胶及水溶性无机离子特征分析

于2010~2011年在南京市城郊两个采样点收集了气溶胶样品,并利用离子色谱(IC)法分析了其中的水溶性无机离子成分.结果表明,采样期间除了夏季,其他3个季节南京城郊气溶胶污染都较严重.南京城郊气溶胶谱分布特征基本在0.65~2.1μm和5.8~9μm粒径段出现峰值.PM2.5与能见度的相关性很大.城郊离子总质量浓度均是春冬季高于夏秋季,四季阴离子质量浓度明显高于阳离子,且这一特征在细粒子上表现明显.水溶性离子在气溶胶中所占比例是夏秋冬季城区高于郊区.南京城郊NO3-/SO42-年均值表明采样期间燃煤仍然是主要污染源,且该比值夏季最低,冬季最高.NH4+、K+、NO3-和SO42-主要富集在细粒子上;Na+、Cl-和NO2-在粗粒子和细粒子上都有富集;Ca2+、Mg2+和F-主要在粗粒子上富集.因子分析(FA)的方法表明南京城区气溶胶主要有3个来源.     

青海高原季节性降雪中的黑碳气溶胶

对青海高原2012年季节性降雪进行采集.6个采样点集中在青海高原东南部地区,共包括36袋雪样.从分析结果可知,青海高原东南部地区季节性降雪中含有较多的沙尘,滤膜颜色多为土黄色.6个采样点雪中的黑碳浓度为(184±123)ng/g,表层雪的黑碳浓度范围是59~238ng/g,平均值为152ng/g.通过后向轨迹聚类分析知道气流主要来自南亚和青藏高原地区,有少部分是来自塔克拉玛干沙漠和戈壁地区.     

A 14-year measurement of toxic elements in atmospheric particulates in Hong Kong from 1995 to 2008

Toxic elements in the atmosphere can enter and accumulate in the human body, seriously impacting human health. In this study, we analyzed a 14-year （1995-2008） measurement of three toxic elements （As, Cd and Cr） in PMlo in Hong Kong, China. The pollution of these toxic elements in Hong Kong was not serious. The trend analysis showed that As and Cr in PM10 increased at a statistically significant level （p〈0.05） during the 14-year period, while the Cd in PM10 did not change significantly. Typical seasonal variations were observed for all three toxic elements, largely in relation to the Asian monsoon. Hourly 10-day backward trajectories were computed and cate- gorised into four groups. The continental air masses showed much higher concentrations of the three toxic elements than the marine air masses. The abundances of As and Cd in the PM10 were much higher in the continental air masses than those in the marine air masses, while the abundances of Cr showed an opposite pattern. The trends of the three toxic elements in East China＇s air mass were consistent with those in the overall data set ofHong Kong. Examination of the toxic element data recorded at urban sites and a roadside site also indicated a large contribution of external air masses to particulate As and Cd in Hong Kong. These results suggest that the long-range transport from the mainland of China is the dominant contributor to particulate As and Cd, while both local and long-distance sources determine the particulate Cr in Hong Kong.     

垃圾焚烧厂周边大气二噁英含量及变化特征——以北京某城市生活垃圾焚烧发电厂为例

2013年4月至2014年1月对北京市某生活垃圾焚烧厂周边4km范围内5个采样点环境空气中二噁英含量、组成特征及季节变化特征进行了分析.结果表明该垃圾焚烧厂周边环境空气中PCDD/Fs质量浓度的变化范围为8.3~115pg/m³,毒性当量(TEQ)变化范围为0.11~1.9pg I-TEQ/m³,其中秋季1个采样点和冬季全部采样点超出日本环境空气质量标准限值(0.6pg I-TEQ/m³).1,2,3,4,6,7,8-HpCDF和OCDF均是四季空气中PCDD/Fs质量浓度的主要贡献单体,而2,3,4,7,8-PeCDF是总TEQ贡献最大的单体.空间分布特征表现为近源点位(~400m)浓度水平较高而其他点位(>1000m)浓度水平与距污染源距离远近没有显著相关性;季节变化特征表现为冬季值显著高于其他季节,分析可能与冬季采暖及大气扩散条件差导致的大气整体污染较重有关.样品中二噁英同族体及异构体分布指纹谱图与焚烧设施排放烟气存在差别,主成分分析(PCA)源解析结论与指纹谱图特征分析结论一致,体现为多种污染源共同作用的影响.二噁英呼吸暴露剂量估算结果表明该区域人群呼吸暴露风险总体处于较为安全的水平(0.034~0.161pg I-TEQ/(kg·d)),但仍需关注大气重污染天气发生时的呼吸暴露风险.