Ambient distribution of particulate- and gas-phase <Emphasis Type="Italic">n</Emphasis>-alkanes and polycyclic aromatic hydrocarbons in the Tibetan Plateau

Attention has been paid for the levels, sources and health risks of atmospheric aliphatic and polycyclic aromatic hydrocarbons (n-alkanes and PAHs) in remote areas, however, few studies have focused on those in the Tibetan Plateau. In this study, 18 pairs of atmospheric samples were obtained during the period from August 2006 to July 2007 in Lhasa, the capital city of Tibet. Both gas-phase and particulate-phase n-alkanes and PAHs were measured. Concentrations of n-alkanes (gas + particulate phase, 99.1–480.9 ng/m³) and PAHs (gas + particulate phase, 11.4–72.5 ng/m³) in Lhasa are lower than those in many cities. The sources of n-alkanes related to biological and petroleum sources were 67 and 33%, respectively. According to the results of diagnostic ratios and principal component analysis, emission of traffic vehicles was one of the important PAH sources, and sources of benzo(a)pyrene was likely attributed to incense burning. Good simulations were obtained by traffic soot-based model for fluoranthene, pyrene and benzo(a)anthracene, while, wood soot-based model fitted the experimental results of benzo(a)pyrene better. This meant atmospheric fate of PAHs was mainly influenced by the adsorptive partitioning that occurred during traffic and incense burning procedures. In addition, the benzo[a]pyrene-equivalent carcinogenic power (BaPE) in the present study (0.1–1.6 ng/m³) is lower than those in other cities and also the air quality standard of China, suggesting that atmospheric PAHs caused low health risks.     

Temporal and spatial variation in soil respiration of poplar plantations at different developmental stages in Xinjiang, China

Soil respiration is essential for the understanding of carbon sequestration of forest plantations. Soil respiration of poplar plantations at three developmental stages was investigated in 2007 and 2008. The results showed that mean soil respiration rate was 5.74, 5.10 and 4.71 μmol CO₂ m⁻² s⁻¹ for stands of 2-, 7- and 12-year-old, respectively, during the growing season. Soil temperature decreased with increasing plantation age and canopy cover. As plantation matured, fine root biomass also declined. Multiple regression analysis suggested that soil temperature in the upper layer could explain 73-77% of the variation in soil respiration and fine root biomass in the upper layer could explain further 5-8%. The seasonal dynamics of soil respiration was mainly controlled by soil temperature rhythm and fine root growth since soil water availability remained adequate due to monthly irrigation. Spatial variability of soil respiration varied considerably among three age classes, with the coefficient of variation of 28.8%, 22.4% and 19.6% for stands of 2-, 7- and 12-year-old, respectively. The results highlight the importance of the development stage in soil carbon budget over a rotation, since both temporal and spatial variation in soil respiration displayed significant differences at different developmental stages.     

台风过程影响下的滨海湿地物理变量观测及湿地系统响应

如何研究台风等极端天气事件影响下的湿地系统响应过程,进而提出有效的生态完整性维护和管理方案,对关键区域的湿地管理及生态安全维护具有重要意义。本文于2021年9月“灿都”台风期间在南汇东滩南岸设置水动力观测点,采集表层沉积物、测量滩面高程并用无人机获得植被影像,运用ArcGIS空间分析,探讨了台风过程影响下的南汇东滩水动力、滩面沉积变化与植被分布面积响应。结果表明：台风中,观测点近底层平均流速为0.23 m/s,植被边缘平均有效波高和波能是台风前后的1.54倍和2.14倍,近底层1 m的滩面出现“高悬沙浓度层”（>10 g/L）且存在时长为8.13 h。台风后高程低于4 m的稀疏海三棱藨草和互花米草滩面侵蚀0～4.8 cm,高程高于4 m的茂盛互花米草和芦苇滩面淤积0～14.7 cm;研究区植被分布面积共减少1 827.67 m²,减少量占台风前植被总量的1.63%,其中侵蚀滩面植被分布面积减少31.9%,淤积滩面减少68.1%。对台风过程影响后的湿地管理,可以总结为：（1）湿地在台风过程后滩面基本表现为明显的侵蚀、淤积区域共存的特征;（2）对高程低于4 m的侵蚀滩面,建议确定植被适宜生长的高程,结合台风过程冲淤变化通过“微生物膜”和植被斑块移植的方法消浪、固滩和促淤,加速湿地在台风过程影响后的修复。     

Satellite remote sensing of sea-ice and its operational monitoring method along the coast of China

Sea-ice is an important operational item for real timely monitoring and forecasting marine environment of China. This paper introduces an operational method of satellite remote sensing to monitor sea- ice using quantitative data of NOAA, and its contents include computer processing of AVHRR sounding data of NOAA and its program design, imagery processing of sea-ice imagery from satellite and their thematic analysis. The sea-ice satellite colour imageries processed via this software system are able to interpret sea-ice pattern, characterizing it by thickness, maximum position of ice boundary, floe concentration and dynamic process of ice changing. At the same time, analyses of the ice condition of the Bohai Sea for the two-year period (1986-1988) as monitored by satellite have been summarized.     

试论矿井水灾害的预测及预防

矿井水灾害给矿山造成生命,财产的巨大损失,可据矿山积累的矿井水动态观测资料,采用数学方法预测降雨量或地表水流量超过正常值的未来年份,对可能发生的矿井水灾害进行预报,及早采取预防措施,并以恩口煤矿为例,预测1995年6月或1996年6月可能发生灾变。     

An intelligent agent based on virtual geographic environment system

On the basis of previous work, this paper designs an intelligent agent based on virtual geographic environment (VGE) system that is characterized by huge data, rapid computation, multi-user, multi-thread and intelligence and issues challenges to traditional GIS models and algorithms. The new advances in software and hardware technology lay a reliable basis for system design, development and application.     

THE NUMERICAL SIMULATION OF TWO-DIMENSIONAL DYNAMICAL CLIMATE MODEL WITH MOUNTAIN FORCING

In order to investigate the effects of trace gases on climate variation in the atmosphere,we have developed a primitive equation two-dimensional dynamical climate model with five levels.A series of simulation results and discussions are shown in this paper,indicating that the model is useful and can comectly reproduced the main feature of the general atmospheric circulation and its seasonal changes.In addition,we have discussed the role of the Qinghai-Xizang Plateau on the formation process of summer monsoon in South Asia and found that the thermal effect of the Qjnghai-Xizang Plateau may not be the main factor controlling the onset and the variation of the summer monsoon in South Asia.     

Late Cretaceous-Cenozoic exhumation of the Yanji area, northeast China: Constraints from fission-track thermochronology

The Yanji area, located at the border of China, Russia, and Korea, where the Phanerozoic granitoids have been widely exposed, was considered part of the orogenic collage between the North China Block in the south and the Jiamusi–Khanka Massifs in the northeast. In this study, the cooling and inferred uplift and denudation history since the late Mesozoic are intensively studied by carrying out apatite and zircon fission-track analyses, together with electron microprobe analyses (EMPA) of chemical compositions of apatite from the granitoid samples in the Yanji area. The results show that: (i) zircon and apatite fission-track ages range 91.7–99.6 Ma and 76.5–85.4 Ma, respectively; (ii) all apatite fission-track length distributions are unimodal and yield mean lengths of 12–13.2 µm, and the apatites are attributed to chlorine-bearing fluorapatite as revealed by EMPA results; and (iii) the thermal history modeling results based on apatite fission-track grain ages and length distributions indicate that the time–temperature paths display similar patterns and the cooling has been accelerated for each sample since ca 15 Ma. Thus, we conclude that sequential cooling, involving two rapid (95–80 Ma and ca 15–0 Ma) and one slow (80–15 Ma) cooling, has taken place through the exhumation of the Yanji area since the late Cretaceous. The maximum exhumation is more than 5 km under a steady-state geothermal gradient of 35°C/km. Combined with the tectonic setting, this exhumation is possibly related to the subduction of the Pacific Plate beneath the Eurasian Plate since the late Cretaceous.     

使用气象目标物验证珠海〖CDF*2〗澳门双偏振雷达的差分反射率标定

为了寻求适合珠海-澳门双偏振雷达的差分反射率标定方法,提升其探测的准确性和稳定性,对珠澳雷达的太阳法和垂直指向法的标定结果进行了分析对比。对比表明两个标定方法确定的系统偏差之间存在较大的差异。为了确定真实的系统偏差,基于业务运行的体积扫描数据,在初始差分相移订正的基础上,用差分相移、反射率、信噪比和相关系数作为筛选条件,筛选了适合作为标定参照物的小雨和干雪,对珠澳雷达的标定结果进行了验证并分析了标定误差的成因。结果表明以小雨和干雪作为目标物得到的差分反射率系统偏差和太阳扫描法得到的结果非常一致,且在超过两个月时间内表现较为稳定,可以用于对雷达系统的差分反射率偏差进行长期的在线监控。垂直指向法标定的结果存在明显偏差。与英国Thurnham C波段雷达以及南京大学C波段雷达的垂直入射标定数据的横向对比和分析表明,珠澳雷达的垂直指向法标定受到位于天线罩顶部的航空障碍灯和维护窗的影响,使得标定结果出现偏差。