长江三峡花岗岩地区土壤流失时间分布特性

长江三峡花岗岩地区坡面土壤流失以耕地砂砾化面蚀和有部分植物覆盖坡面的鳞片状面蚀为主，该地土壤流失研究结果表明，由以上两类面蚀导致的土壤流失量月分布与月降雨量的分布基本趋势一致，二者呈现较为明显的线性相关关系。地面坡度＞３０°的裸地土壤流失量达５０００ｔ／ｋｍ３·ａ以上，覆盖度≥０．７０的林地土壤流失量＜５００ｔ／ｋｍ２·ａ，该流域土壤流失量为１５４４．１４ｔ／ｋｍ２·ａ，产沙量为６９４．８６ｔ／ｋｍ２·ａ     

加强三峡地区土壤腐蚀环境调查与研究

三峡工程是关系到国计民生的一项特大型工程，必须保证其长期，安全地运行，这就要求对工程中的埋地金属构件进行有效的腐蚀防护，而构件使用寿命的预测及防护方法的筛选又赖于该地区土壤的腐蚀性强弱。本文以三峡坝址土壤的腐蚀性调查与研究为重点，探讨了三峡地区土壤的腐蚀性及其主要影响因子，作者认为，三峡地区土壤的腐蚀性较强，在工程建设中最好先进行土壤腐蚀环境的勘测，并在工程中采用必要的防护方法。     

南水北调中线水源地不同植被类型坡地土壤水分特征研究

为了解不同植被类型土壤水资源的变化规律，选择南水北调中线水源区宁陕县寨沟区域典型植被针阔混交林、针叶林、板栗林、灌木林、荒坡草地和坡耕地为研究对象，通过样地调查与实验分析的方法对其土壤水分物理特征及有机质含量进行测定研究。结果表明，各种有林地的土壤容重、孔隙度和有机质等理化特征均优于荒坡和坡耕地；针阔混交林土壤含水量最高，蓄水能力明显好于其它植被类型；在垂直剖面上，各种植被类型坡地土壤含水量和饱和蓄水量随土壤深度的增加基本呈递减趋势，但有林地下降幅度较大，表层含水量明显高于荒坡与坡耕地表层。由此可见，在涵养水源方面，针阔混交林最好，针叶林、板栗林与灌木林次之，荒坡与坡耕地较差。     

ENVIRONMENTAL AND ECONOMIC DAMAGE CAUSED BY SEDIMENT FROM AGRICULTURAL NONPOINT SOURCES1

Environmental and economic damages caused by agricultural nonpoint source inputs of sediment and associated pollutants are examined. Widespread water quality problems are identified in lakes, rivers, and estuaries in agricultural areas, and billions of dollars of on-site and offsite costs result from this eroded soil every year. Some water bodies have been irretrievably damaged, and expensive rehabilitation programs are needed to remedy in-place water pollution problems if Clean Water Act goals are to be achieved. Unless effective abatement and rehabilitation programs are established, billions of dollars of benefits to future generations will not be realized as more waters become irretrievably damaged, and billions more will continue to be spent by government to treat symptoms of these sediment-related problems.     

Biosorption of Direct Yellow 12 from aqueous solution using green alga Ulva lactuca

The potential of commonly available green alga Ulva lactuca was investigated as viable biomaterials for removal of synthetic azo dye (Direct Yellow 12, DY-12) from aqueous solution. The results obtained from the batch experiments revealed that the ability of the U. lactuca to remove DY-12 from its aqueous solution was dependent on the dye concentration, pH, and algal biomass but less dependent on the particle size of the U. lactuca. The equilibrium conditions and kinetics of adsorption were investigated, and the adsorption kinetic was consistent with the pseudo-second-order model (R²=1). The adsorption isotherm followed only the Freundlich model with a correlation coefficient R²=0.99. This study demonstrated that the U. lactuca could be used as an effective biosorbent for the removal of DY-12 from its aqueous solution.     

The Chemistry of Throughfall, Stemflow and Soil Water Beneath Oak Woodland and Moorland Vegetation in Upland Wales

The chemistry of bulk precipitation, throughfall, stemflow and soil waters beneath an oak wood (Quercus petraea) canopy and soil waters under moorland vegetation were measured at two sites on acid brown podzolic soils near Llyn Brianne in rural mid-Wales, UK. Between March 1986 and November 1988, precipitation was 4354 mm and annual interception losses from the oak canopy averaged 13% of incident precipitation. Throughfall and stemflow were more acid and concentrations of most solutes were increased 2- to 4-fold compared with bulk precipitation. Nitrate was the only solute retained within the tree canopy. Throughfall collected beneath patches of bracken on the forest floor was less acidic but contained substantially higher concentrations of major ions than bulk precipitation and oak throughfall. the moorland soil was more acidic, contained more exchangeable calcium but less exchangeable aluminium and potassium than the woodland soil. Soil waters beneath both vegetation types were acidic (mean pH range 4.5-4.9) and dominated by sodium and chloride. with the exception of calcium, soil water solute concentrations were greater beneath oak. These differences are ascribed to larger atmospheric inputs beneath the oak canopy compared with the shorter grasses, combined with the effect of differences in nutrient dynamics and water fluxes. Variations in soil water aluminium chemistry are explained in terms of ion exchange and podzolisa-tion processes. the water quality implications of increased upland afforestation of moorland by broadleaved trees are discussed.     

土地资源利用保护与农业生态建设

本文阐述了国内外土地后备资源现状及存在问题,解剖了土壤肥力演化机制和土壤资源保护的关系,介绍了我国生态农业建设的研究进展,指出了今后的主攻方向。     

多层次模糊综合评判在林业土壤评价中的应用

本文以四川部分林业土壤为例,应用多层次模糊综合评判法进行土壤资源的质量评价。采取聘请众多专家分级、打分的办法制定评价标准和确定评价因素权数。实施了专家系统与综合评判的联合运用技术,并探讨了提高土壤质量评级精度的“加细”评判问题。最后,通过比较多层次模糊综合评判法与传统法(评分法)的评价结果,指出前者具有更强的客观性和全面性。     

Residual risk for cytogenetic abnormalities after prenatal diagnosis by interphase fluorescence in situ hybridization (FISH)

Results from conventional cytogenetic studies on 21 609 amniotic fluid specimens were analyzed retrospectively to determine the residual risk for a cytogenetic abnormality if interphase FISH, capable of only detecting aneuploidy for chromosomes 13, 18, 21, X and Y, was performed and did not reveal an abnormality. Detection rates (the probability of detecting a cytogenetic abnormality when an abnormality is present) and residual risks (the likelihood of a cytogenetic abnormality, in view of normal interphase FISH results) were calculated for the four major clinical indications for prenatal diagnosis (advanced maternal age, abnormal maternal serum screen indicating increased risk for trisomy 18 or trisomy 21, abnormal maternal serum screen indicating increased risk for neural tube defects and ultrasound abnormality). Differences in detection rates were observed to depend on clinical indication and presence or absence of ultrasound abnormalities. The detection rate ranged from 18.2 to 82.6% depending on the clinical indication. The detection rates of abnormalities significant to the pregnancy being evaluated (i.e. abnormalities excluding familial balanced rearrangements and familial markers) were between 28.6 and 86.4%. The presence of ultrasound abnormalities increased the detection rate from 72.2 to 92.5% for advanced maternal age and from 78.6 to 91.3% for abnormal maternal serum screen, indicating increased risk for trisomy 18 or trisomy 21. With regard to residual risk, the risk for a clinically significant abnormality decreased from 0.9–10.1%, prior to the interphase FISH assay, to a residual risk of 0.6–1.5% following a normal interphase FISH result in the 4 groups studied. Providing patients with detection rates and residual risks, most relevant to their situation (clinical indication and presence or absence of ultrasound abnormality) during counseling, could help them better understand the advantages and limitations of interphase FISH in their prenatal diagnostic evaluation. Copyright © 2003 John Wiley & Sons, Ltd.