华南暴雨试验过程的环境场和云团特征的初步分析

用诊断方法对 1 998年华南暴雨试验 5月 2 3～ 2 4日强化观测期暴雨的大尺度环境条件和云团的中尺度特征进行了初步分析。指出了中尺度云团具有次第发展的现象 ,并提出了一种可能的机制     

Energy and Water Balance at Soil-Air Interface in a Sahelian Region

l. IntroductionModel simulation of soll physical properties is very 1mportant for climate studies becauseof the role they play in different interaction processes with the atmosphere. One of the mostwidespread studies is the implementation of soil models 1n General Circulation Models(GCMs); previous studies showed, in fact, that climate simulat1ons are sensitive to theparameterization of the energy and mass fluxes at the land surface (V1terbo, l995; Beljiaars etal., l996; Dolman et al., l997…     

内蒙古暴风雪灾害及其形成过程

分析了近50年来内蒙古所发生的暴风雪天气的环流演变特点，指出在暴风雪过程中，大风、暴雪强降温联合施虍，加剧了人畜的热损耗率，从百形成严重的冻害。高空存在强急流、强锋区、强辐散是促成蒙古气旋猛烈发展形成大风的主要原因，而低层华北沿海高脊的发展又为南方水汽北输提供了条件，它们共同促成了内蒙古暴风雪的形成。     

2000-09-24郑州暴雨过程物理量演变特征

利用郑州实时探空资料 ,分析了 2 0 0 0年 9月 2 4日本区暴雨发生前郑州站物理量演变特征 ,为秋季暴雨预报提供了思路和线索     

Chemical composition of dew in Amman, Jordan

Twenty-six dew samples were collected on a glass surface from an urbanized area in Amman city during the period October 1999 to June 2000. They were analyzed for the major ions (Cl, SO₄, NO₃, Ca, Mg, Na, K and NH₄) in addition to three heavy metals (Pb, Cd and Co). Rain samples were collected for the same period and compared to the chemical constituents of dew.It was found that both rain and dew samples were of almost neutral acidity due to the buffering effect of CaCO₃. Dew composition was mainly from CaSO₄ solution due to conversion of CaCO₃ to CaSO₄ when left exposed to a sulfate-rich atmosphere. The total dissolved solids were higher in dew than rain samples of the same period. This was attributed to higher evaporation effect on dew than rain.The heavy metal content in dew is highest during the cold winter season (December–March) due to excess fossil fuel combustion for heating purposes in this period. The heavy metal content in dew was lower than that for rain during the same period because of the shorter period of dew formation than rainwater.     

Remediation technologies for metal-contaminated soils and groundwater: an evaluation

Metals including lead, chromium, arsenic, zinc, cadmium, copper and mercury can cause significant damage to the environment and human health as a result of their mobilities and solubilities. The selection of the most appropriate soil and sediment remediation method depends on the site characteristics, concentration, types of pollutants to be removed, and the end use of the contaminated medium. The approaches include isolation, immobilization, toxicity reduction, physical separation and extraction. Many of these technologies have been used full-scale. This paper will review both the full-scale and developing technologies that are available. Contaminants can be isolated and contained to minimize further movement, to reduce the permeability of the waste to less than 1×10⁻⁷ m/s (according to U.S. guidelines) and to increase the strength or bearing capacity of the waste. Physical barriers made of steel, cement, bentonite and grout walls can be used for isolation and minimization of metal mobility. Another method is solidification /stabilization, which contains the contaminants in an area by mixing or injecting agents. Solidification encapsulates contaminants in a solid matrix while stabilization involves formation of chemical bonds to reduce contaminant mobility. Another approach is size selection processes for removal of the larger, cleaner particles from the smaller more polluted ones. To accomplish this, several processes are used. They include: hydrocyclones, fluidized bed separation and flotation. Addition of special chemicals and aeration in the latter case causes these contaminated particles to float. Electrokinetic processes involve passing a low intensity electric current between a cathode and an anode imbedded in the contaminated soil. Ions and small charged particles, in addition to water, are transported between the electrodes. This technology have been demonstrated in the U.S. full-scale, in a limited manner but in Europe, it is used for copper, zinc, lead, arsenic, cadmium, chromium and nickel. The duration of time that the electrode remains in the soil, and spacing is site-specific. Techniques for the extraction of metals by biological means have been not extensively applied up to this point. The main methods include bioleaching and phytoremediation. Bioleaching involves Thiobacillus sp. bacteria which can reduce sulphur compounds under aerobic and acidic conditions (pH 4) at temperatures between 15 and 55°C. Plants such as Thlaspi, Urtica, Chenopodium, Polygonum sachalase and Alyssim have the capability to accumulate cadmium, copper, lead, nickel and zinc and can therefore be considered as an indirect method of treating contaminated soils. This method is limited to shallow depths of contamination. Soil washing and in situ flushing involve the addition of water with or without additives including organic and inorganic acids, sodium hydroxide which can dissolve organic soil matter, water soluble solvents such as methanol, nontoxic cations, complexing agents such as ethylenediaminetetraacetic acid (EDTA), acids in combination with complexation agents or oxidizing/reducing agents. Our research has indicated that biosurfactants, biologically produced surfactants, may also be promising agents for enhancing removal of metals from contaminated soils and sediments.

In summary, the main techniques that have been used for metal removal are solidification/stabilization, electrokinetics, and in situ extraction. Site characteristics are of paramount importance in choosing the most appropriate remediation method. Phytoremediation and bioleaching can also be used but are not as well developed.     

Heavy metals on tidal flats in the Yangtze Estuary, China

 Five short cores were used to examine heavy metals on tidal flats in the Yangtze Estuary, China. Statistically insignificant trends in lead-210 and most metals with core depth are primarily due to high sedimentation rates. Metal contents are correlated with percent aluminum, which reflects the clay contents in the sediment, and they are also affected by proximity to sewage outlets and local industry. National standards for copper are exceeded in four cores, zinc in one core, and arsenic in all cores. Heavy metal contents are generally lower on the Yangtze tidal flats compared to most other estuaries because high sediment loads dilute metal inputs. Received: 1 June 1999 · Accepted: 15 August 2000     

地面辐合线与强对流天气落区

通过对1993～2002年焦作辖区20余次强对流天气过程的统计分析发现，在天气尺度条件下，地面气压场上中尺度辐合线对强对流天气的维持时间和落区有很好的指示性。     

1998年夏季西南低涡活动与长江上游暴雨

应用天气学和统计学方法，分析了1998年盛夏西南低涡活动的主要特征。指出该年夏季西南低涡活动偏强，该年长江上游暴雨偏多与此有关。     

1998年6月28日～7月2日淮河流域暴雨分析

文中对比分析了 1998年 6月 2 8～ 2 9日和 7月 1～ 2日淮河水循环试验期间两次特大暴雨过程的天气形势、红外卫星云图上降水云系的特征及其水汽来源。结果表明 :(1) 6月底的暴雨是一次东移的西南低涡引发的暖性切变线降水 ,β中尺度对流系统起主要作用。 7月初的暴雨过程是一次移动缓慢的锋面降水 ,锋面上有中尺度的云团活动 ,这是一次大中尺度系统相互作用的结果。 (2 )两场特大暴雨的水汽源地都为中国南海北部地区 ,而强度达到18～ 2 2m/s的西南低空急流是水汽的输送带。