农田生态系统大气硫沉降通量的观测研究

1998年 11月～ 1999年 10月间在中国科学院红壤站 (江西鹰潭 )农田小气候站进行了大气二氧化硫 (SO2 )、硫酸盐粒子 (SO2 -4)浓度采样和雨水样本收集 ,利用阻力模式和全年逐时气象资料计算 SO2 和 SO2 -4的干沉降速度 ,估算干沉降通量 ,利用降水资料和雨水中硫酸根离子浓度估计大气硫的湿沉降 ,从而定量研究大气硫沉降输入农田生态系统的通量 ,结果表明 :农田下垫面上 SO2 和 SO2 -4干沉降速度的年平均值分别是 0 .373± 0 .170 cm· s-1(月均值 0 .16 1～ 0 .5 45 cm·s-1)、0 .198± 0 .12 3cm· s-1(月均值 0 .15 2～ 0 .2 6 9cm· s-1)。农田下垫面硫年总沉降量为 10 .3g· m-2 ,其中干沉降占总沉降的 83.3%。硫的干沉降又以 SO2 的干沉降为主 ,占年干沉降总量的 92 .2 %。大气硫沉降输入占农田生态系统输入总量的 90 %以上 ,是农田生态系统获取硫素的一个重要途径     

A Laboratory and Theoretical Study on the Uptake of SO2 Gas by Large and Small Water Drops Containing Heavy Metal Ions

Laboratory experiments have been carried out to investigate the uptake of sulfur dioxide by water drops containing heavy metal ions where the metal ions serve as catalysts to oxidise the taken up S(IV) into S(VI). During the gas uptake the drops were freely suspended at their terminal velocity in the airstream of the Mainz vertical wind tunnel. Two series of experiments were carried out, one with large millimeter size water drops containing manganese or iron ions, and the other with small water drops containing manganese ions and having radii in hundreds of micron size range. The experimental results were compared against model computations using the Kronig–Brink model and the fully mixed model, modified for the case that heavy metal ions present in the liquid phase act as catalysts for the oxidising process. The results of the model calculations show that there are only small differences between the predicted gas uptake according to the two models. In addition it was found that the experimental obtained results from the uptake of SO₂ by water drops containing heavy metal ions for both, large and small water drops did agree with the model results.     

Quantitative Evaluation of Water Deposited By Dew on Monuments

Samples of White and Green Carrara marble, and three types oflimestone and brick exposed in the field vertically and horizontally were used to evaluate condensationon monuments during clear sky nights. Experiments in a simulation chamber under controlledconditions led to a general equation for the actual amount of water deposited on a surface by dew.This is determined by: How much and for how long the surface temperature falls below the dew point,the moisture content in the air and the ventilation. On clear nights, the condensation on buildingstructures facing the sky may reach some 0.2 kg m^-2 (or 0.2 mm), whereas condensation on verticalsurfaces is very small. Computation of the seasonal trend of night-time condensationshowed that the maximum amount of water condensed per night occurs in the autumn, with the moreabundant concentration of moisture in the air. The total amount of water condensed per month isfound to be a maximum in the summer-autumn period. Morning condensationfor the thermal inertia of monuments is also relevant, and has been calculated to reach the same order of magnitude as thenocturnal dew. A detailed analysis of the temperature and mixing ratio profiles near a condensingsurface has shown two different situations. In still air, the two profiles follow an exponentiallaw and the thermal and the concentration layers lie within a few tens of millimetres. Inthe presence of turbulence, the thickness of these two layers is dramatically reduced. In still air, infront of a vertical, chilly surface, the deposition rate of air pollutants by thermophoresis and/orStefan flow is increased by 3 or 4 times in comparison with a horizontal surface. In the presence ofturbulence, the thickness of the thermal and concentration layers was dramatically reduced, makingthese two kinds of deposition much faster.     

辽东裂谷块状硫化物矿床中电气石岩的H、O和Si同位素地球化学

辽东裂谷内分布着一系列块状硫化物矿床，含矿建造及矿层内普遍发育有纹层状电气石岩。电气石岩的H、O和Si同位素地球化学研究表明，其中δD为-50‰—62‰，δ18O值为13.3‰—16.7‰，δSi为0.1‰—0.4‰。H、O同位素组成与典型块状硫化物矿床中的电气石岩完全一致。研究认为矿床中的电气石岩为海底热水沉积成因作用的产物。此类电气石央坏蛋硫化物矿床关系密切，具有明显的成因找矿指示意义。     

黄河下游泥沙淤积的经验统计关系

以黄河下游历年实测水文泥沙资料为基础,运用多元回归分析方法,建立了下游河道淤积量与淤积强度的经验统计关系。揭示了不同粒径组泥沙的来量和它们在全沙中所占的比率对下游河道淤积特征的影响。同时,研究了高含沙洪水及清水基流对下游河道淤积的影响。     

CuInSe2太阳电池薄膜的制备技术及研究进展

着重介绍了CuInSe2的结构和光、电学特性；讨论了多各上薄膜沉积技术；评价了主要的合成装置及其作途；综述了制备CuInSe2太阳电池器件的工艺和材料，提出了一种能成功地生产大面积太阳电池薄膜的经济有铲的沉积技术。     

鄂尔多斯西南缘前陆盆地沉降和沉积过程模拟

本文将东祁东逆冲带与鄂尔多斯西南缘晚三叠世前陆盆地相结合，研究了逆冲带内部变形特征，前陆盆地中层序地层格架特征及其反映的盆缘构造性质和幕式逆作作用。     

Heavy metal retention in secondary precipitates from a mine rock dump and underlying soil, Dalarna, Sweden

This study investigates the retention of heavy metals in secondary precipitates from a sulfidic mine rock dump and underlying podzolic soils by means of mineralogical and chemical extraction methods. The rock dump, which is at least 50 years old, consists of a 5–10-cm-thick leached zone and an underlying 110–115-cm-thick accumulation zone. Optical microscopy and electron microprobe analyses confirm that pyrrhotite weathering has proceeded much further in the leached horizon relative to the accumulation horizon. The weathering of sulfides in the leached zone has resulted in the migration of most heavy metals to the accumulation zone or underlying soils, where they are retained in more stable phases such as secondary ferric minerals, including goethite and jarosite. Some metals are temporarily retained in hydrated ferrous sulfates (e.g., melanterite, rozenite). Received: 28 October 1996 · Accepted: 24 February 1997     

Geotechnical Hazards Associated with Desert Environment

The aridity of the Arabian Peninsula's deserts ranges between arid to hyperarid with hot dry climate, scarce precipitation and sparse vegetation. These harsh environmental conditions enhance some geomorphologic processes more than others, cause specific geotechnical problems, and increase desertification.From west to east, the general physiography of Saudi Arabia shows the Red Sea coastal plains and the escarpment foothills called Tihama followed by the Arabian Shield mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. Sand moves by wind either as drifting sand or migrating dunes in four major sand seas, over the Arabian Shelf, and in the inter-mountain valleys, in the Arabian Shield causing problems of erosion and deposition. Human activities in the deserts may cause more instability to the sand bodies, enlarging the magnitude of the problem. Fine silty soil particles also move by wind, depositing loess mainly in selected areas downwind in the Tihama. These loess deposits subside and may form earth fissures by the process of hydrocompaction upon wetting. The addition of water can be either natural through storms or man-made through human agricultural or civil activities. Extensive sabkhas exist along the coastal plains of both the Red Sea and Arabian Gulf. The sabkha soil may also heave by salt re-crystallization or collapse by wetting. The shallow groundwater brines present in sabkhas also attack and corrode civil structures. Urbanization and excessive groundwater pumping may also deplete the fresh groundwater resources and may cause subsidence, ground fissuring and surface faulting as observed in some locations in the Arabian Shield. Although the average annual precipitation is very low, rain usually falls in the form of torrential storms, collected by dry valley basins and causing floods to unprotected downstream areas on the coastal plains of the Red Sea.The desert environment, being a fragile echo system, needs to be treated with care. Intercommunications between different national and international agencies and education of the layman should help to keep the system balanced and reduce the resulting environmental hazards. In addition, any suggested remedial measures should be planned with nature and engineered with natural materials.     

An Algorithm for the Determination of All Significant Pathways in Chemical Reaction Systems

When the output of a complex chemical model is analysed, a typical topic isthe determination of pathways, i.e., reaction sequences, that produce ordestroy a chemical species of interest.A representative example is the investigation of catalytic ozone destruction cycles in the stratosphere.An algorithm for the automatic determination of pathways in any given reactionsystem is presented. Under the assumption that reaction rates are known, it finds all significant pathways, i.e., all pathways with a rate above a prescribed threshold.The algorithm forms pathways step by step, starting from single reactions.The chemical species in the system are consecutively considered as `branching points'.For every branching-point species, each pathway producing it is connected witheach pathway consuming it.Rates proportional to `branching probabilities' are calculated.Pathways with a rate that is smaller than a prescribed threshold arediscarded.If a newly formed pathway contains sub-pathways, e.g., null cycles, it is split into these simpler pathways.In order to demonstrate the performance of the algorithm, it has been applied to the determination of catalytic ozone destruction cycles and methaneoxidation pathways in the stratosphere.