极地冰芯中记录的火山作用及其对气候的影响

大多数火山喷发以强酸 (主要是硫酸 )的形式在极地冰芯中留下痕迹 ,通过冰芯连续电导率 (ECM)或各个雪冰样品SO42 - 浓度测定能够恢复历史上的火山作用。极地冰芯中已知年代的火山喷发还可用于冰芯定年。极地冰芯记录的火山信号大小依赖于火山喷发的规模和类型 ,火山喷发的地理位置和酸性气体组成 ,大气气溶胶传输 ,以及沉降地点的年积累率和沉积后生过程等。单个火山喷发通常会导致数月至数年的半球乃至全球范围的气候相对变冷 (这种现象在极区变得更明显 ) ,但过去大规模的爆炸性火山喷发对气候的影响及其与气候变化之间的联系仍有待于进一步研究     

Late Pleistocene–Holocene hydrologic changes in the interfluve areas of the central Ganga Plain, India

Abandoned channel belts, ponds and point bar deposits of palaeochannels in the interfluve regions of the central Ganga Plain suggest changes in the morphohydrologic conditions during the Latest Pleistocene–Holocene. Stratigraphy of these ponds comprises channel sand at the base overlain by shell-bearing clayey silt. The contact of the two facies marks the phase when channels converted into standing water bodies. Point bar deposits of some palaeochannels are overlain by oxidised aeolian sand, indicating that the channel abandonment possibly occurred due to the desiccation and aridity in the region.Optically stimulated luminescence (OSL) chronometry of the pond sediments suggests that the deposition of the basal channel sand started before 13 ka and continued up to 8 ka. The ponds formed around 8–6 ka when the channel activity ceased. Evidence from the point bar deposits also indicates that the fluvial activity in the region ended sometime during 7–5 ka. This was followed by aeolian aggradation. The present study thus suggests that the hydrologic conditions in the Gangetic plains, i.e. initiation of channels and their abandonment, formation of microgeomorphologic features such as ponds and their eventual siltation, were controlled largely by climatic changes (i.e. monsoon changes) supported by tectonic activity. For the past 2 ka, increasing human and related agricultural activity has substantially accentuated the natural siltation rate of ponds.     

Climatological characteristics of the tropics in China: climate classification schemes between German scientists and Huang Bingwei

Reviewing some important German scientists who have developed climatic regionalization schemes either on a global or Chinese scale, their various definitions of the tropical climate characteristics in China are discussed and compared with Huang Bingwei's climate classification scheme and the identification of the tropical climate therein. It can be seen that, due to different methodological approaches of the climatic regionalization schemes, the definitions of the tropics vary and hence also their spatial distribution in China. However, it is found that the tropical climate type occupies only a peripheral part of southern China, though it firmly represents a distinctive type of climate that is supsequently associated with a great economic importance for China. As such, the tropical climate type was mostly identified with its agro-climatological significance, that is by giving favourable growing conditions all-year round for perennial crops with a great heat demand. Tropical climate is, hence, conventionally regarded to be governed by all-year round summer conditions "where winter never comes".     

Impact of climate change and variability on water resources in Heihe River Basin

Studies indicate that the climate has experienced a dramatic change in the Heihe River Basin with scope of temperature rise reaching 0.5-1.1oC in the 1990s compared to the mean value of the period 1960-1990, precipitation increased 18.5 mm in the 1990s compared to the 1950s, and 6.5 mm in the 1990s compared to the mean value of the period 1960-1990, water resources decreased 2.6×108 m3 in the 1990s compared to the 1950s, and 0.4×108 m3 in the 1990s compared to the mean value of the period 1960-1990. These changes have exerted a greater effect on the local environment and socio-economy, and also made the condition worsening in water resources utilizations in the Heihe Rver Basin.     

Influence of Arctic Oscillation on winter climate over China

In this study the relationship between the Arctic Oscillation (AO) and climate in China in boreal winter are investigated. Correlation analysis for the last 41 years shows that the winter temperature and precipitation in China change in phase with AO. High positive correlation (>0.4) between temperature and AO appears in the northern China. High correlation coefficients between precipitation and AO cover the southern China (close to the South China Sea) and the central China (between 30o-40oN and east of ~100oE), with the values varying between +0.3 and +0.4. It is found that during the past several decades the precipitation was strongly affected by AO, but for the temperature the Siberian High plays a more important role. At the interdecadal time scale the AO has significant influence on both temperature and precipitation. Multivariate regression analysis demonstrates that AO and the Siberian High related variance in temperature and precipitation is 35% and 11% respectively. For precipitation, however the portion is rather low, implying that some other factors may be responsible for the changes in precipitation, in addition to AO and the Siberian High.     

Extreme climate events over northern China during the last 50 years

Climate extremes for agriculture-pasture transitional zone, northern China, are analyzed on the basis of daily mean temperature and precipitation observations for 31 stations in the period 1956-2001. Analysis season for precipitation is May-September, i.e., the rainy season. For temperature is the hottest three months, i.e., June through August. Heavy rain events, defined as those with daily precipitation equal to or larger than 50 mm, show no significant secular trend. A jump-like change, however, is found occurring in about 1980. For the period 1980-1993, the frequency of heavy rain events is significantly lower than the previous periods. Simultaneously, the occurring time of heavy rains expanded, commencing about one month early and ending one month later. Long dry spells are defined as those with longer than 10 days without rainfall. The frequency of long dry spells displays a significant (at the 99% confidence level) trend at the value of +8.3%/10a. That may be one of the major causes of the frequent droughts emerging over northern China during the last decades. Extremely hot and low temperature events are defined as the uppermost 10% daily temperatures and the lowest 10% daily temperatures, respectively. There is a weak and non-significant upward trend in frequency of extremely high temperatures from the 1950s to the mid-1990s. But the number of hot events increases as much as twice since 1997. That coincides well with the sudden rise in mean summer temperature for the same period. Contrary to that, the frequency of low temperature events have been decreasing steadily since the 1950s, with a significant linear trend of -15%/10a.     

层控夕卡岩型矿床成矿系统的元素活动性及质量迁移--以铜陵冬瓜山铜矿床为例

应用改善了的质量平衡方程研究冬瓜山层控夕卡岩型铜矿床成矿系统的元素活动性及质量迁移，结果表明：系统中Zr,Hf,Y和Nb为不活动元素，其余均为活动元素。主量元素中仅CaO为迁出组分，其质量迁移量为84％，其余均为带入组分，带入量最大的SiO2的质量迁移量高达2384％；稀土元素均为带入组分，其中，中稀土较轻稀土和重稀土的活动性更强；其它微量元素中，带入序列由强到弱为：Cr→Ta→Sn→Th，迁出序列由强至弱依次为：U→Sb→Ni—Sr→Ba→Bb→Co→W；成矿元素Cu和Ag为带入组分，其中Cu的带入量最大，质量迁移量高达1200％。本文还得出两点具普适性认识：①稀土元素较其它微量元素对体系条件的变化更为敏感，且往往表现出明显的规律性变化，能更好地示踪地质地球化学过程。②不同元素在不同体系中的行为特征差异极大，仅凭经验判定某一元素为不活动元素往往不可靠。因此，在开展质量平衡研究时，首先采用适当方法确认体系的不活动元素是一项不可或缺的前提工作。     

镜泊湖地区水体的同位素、元素地球化学特征及地下热水储存状态分析

依据镜泊湖地区水体的同位素、水化学及微量元素中子活化分析资料，详细阐述了各采样点水体的来源、补给相对高程和它们之间可能的水力联系，以及有关的地热信息；分析了区内地热资源的有利地质背景条件研究区地处深大断裂及岩浆喷发带，火山喷发一直延续至第四纪全新世，有充分的热源供给；区内上部为较厚的玄武岩覆盖，有利于储存地热；下部白垩系上统为主要含水层，发现有广泛分布的典型木／岩热蚀变产物——斜发沸石，进而证明存在地下热水的可能性。