Recent Decrease in the Lead Concentration of Antarctic Snow

Abstract

Differential Pulse Anodic Stripping Voltammetry (DPASV) was applied to determine the lead concentration in recent snow at two sites in the Victoria Land region, East Antarctica. Snow samples were collected during the 6th Italian Scientific Expedition to Antarctica (austral Summer 1990–91) along the wall of 2.5 m-deep hand-dug pits and by coring to a depth of about 11 m. The measurements revealed that lead content in Antarctic snow increased continuously from 1965 (about 3 pg/g) to the early 1980s (maximum about 8 pg/g), after which a marked, rapid decrease took place during the second half of 1980s, down to 2–4 pg/g in 1991. Estimates of the lead contributions from rocks and soils, volcanoes and the marine environment, together with analysis of statistical data on non-ferrous metal production and gasoline consumption, and the corresponding lead emissions into the atmosphere of the Southern Hemisphere, show that a net anthropogenic component is present and support the hypothesis that the trend observed in Antarctic snow may be related to lead consumption in gasoline, which firstly was on the rise, then declined owing to the increased use of unleaded gasoline.     

Effects of land use patterns on soil aggregate stability in Sichuan Basin, China

Soil aggregate stability as a key indicator of soil structure, is a product of interactions between soil environment, management practices, and land use patterns. The objective of this study was to analyze the impact of various land use patterns on soil aggregate stability in Sichuan Basin of southwestern China. The dry- and water-stable aggregate size distributions were determined by manual dry sieving procedure and Yoder's wet sieving procedure, respectively, while microaggregates and its mechanical and chemical stabilities by Kachisky's method, oscillator method, and citrate-dithionate (C-D) reagent method, separately. The results indicated that fractal dimension and surface fractal dimension were useful indicators to reflect soil aggregate distribution. Land use patterns have an obvious influence on soil aggregate stability. In the study area, water stability, mechanical stability, and chemical stability followed the sequence, Barren landforestlandorchardcropland, and the original stability and collapse velocity were sensitive to soil properties and soil structure. The difference of aggregate stability under different land use patterns is mainly due to the intensity of human disturbance and cultivation. Improper land use patterns will lead to breakdown of unstable aggregates, producing finer and more-easily transportable particles and microaggregates. In the future, inappropriate cultivation and land use patterns should be changed to protect soil structure, to improve soil aggregate stability and soil fertility in Sichuan Basin.     

光度法对不同土地利用类型河流在不同水期氮磷分布特性及定量源解析研究

氮和磷是水环境生物生长和繁殖必须的营养成分,影响水体初级生产力的水平,且水体富营养化水平与氮磷形态密切相关,随着水体环境的改变,沉积物会向水体释放氮磷,造成二次污染。同时,对外源氮磷污染来源的贡献进行定量识别,可有效管理和控制水体氮磷污染负荷。毗河和石亭江是沱江的重要支流,影响着长江母亲河的水质。采用钼锑抗分光光度法和连续提取法研究在枯水期和丰水期毗河和石亭江水体和表层沉积物中总氮(TN)、总磷(TP)及各形态氮磷的分布特性,对比不同土地利用类型河流氮磷行为特性及释放风险,并采用Multiple Linear Regression of the Absolute Principal Component Scores(APCS-MLR)受体模型进行氮磷污染源的识别和量化。研究结果表明：(1)研究区水体和表层沉积物中氮磷均处于不同程度的污染水平,水体枯水期TP的主要贡献者是颗粒态无机磷(PIP)和颗粒态有机磷(POP),而丰水期却是颗粒态无机磷(PIP)和溶解态无机磷(DIP),两水期水体中TN的主要贡献者是硝态氮(NO^-₃-N)和有机氮(ON)...     

盐碱地利用障碍因子高光谱遥感反演研究

选取陕北拌沙改良盐碱地为研究对象,对盐碱地利用障碍因子进行高光谱遥感反演研究。通过实测研究区域的作物长势,采集土壤样品和土壤高光谱数据,并实验测定土壤理化性质分析盐碱地利用的障碍因子,研究盐碱地利用障碍因子的高光谱特征,建立其遥感定量反演模型,并进行精度检验。研究结果表明：土壤盐分含量是制约改良盐碱地利用的主要障碍因子,毛管孔隙度与土壤盐分含量具有良好相关性,也可以作为障碍因子之一;利用土壤的高光谱数据对土壤全盐含量及毛管孔隙度进行遥感定量反演具有良好的精度(回归分析决定系数R2分别为0.938和0.973);检验样点精度检验结果表明,盐分含量及毛管孔隙度的实测值与预测值均具有良好的相关性(k均接近于1,R2分别为0.840 4和0.796 5),反演精度较高。通过高光谱数据对盐碱地改良利用的障碍因子进行遥感定量反演,对于指导盐碱地的整治改良和利用具有重要的推动作用。     

Development of novel backwash cleaning technique for reverse osmosis in reclamation of secondary effluent

The objective of the study was to further develop a novel cleaning technique for reverse osmosis in reclamation of municipal secondary effluent. This technique is a new backwash method via direct osmosis (DO) by intermittent injection of the high salinity (HS) solution without stopping of high pressure pump and it is environment and membrane friendly technique. In the study, DO-HS trials were carried out with a UF-RO pilot system which was operated on site with the secondary treated effluent as the raw feed. Different operating conditions for DO-HS treatment in the actual process were investigated. It was found that the operation for implementation of the DO-HS cleaning technique developed was easy. For the first time, the actual profiles of HS concentration, DO backwash flow rate, brine flow rate and permeate pressure during DO-HS treatment have been demonstrated. It was observed that turbidity of the brine stream during DO-HS treatment at 3 NTU was 5 times higher than that before DO-HS treatment. The results from this study have confirmed the previous hypothesis with DO-HS treatment that there would be a strong driving force for DO backwash to lift and sweep the foulants from the membrane surface which would be carried over to the brine. The optimal plant operating conditions in terms of RO feed flow rate, HS concentration and HS injection time are ready for the DO-HS method to be adopted and validated in a long-term continuous plant operation.     

Maneuver analysis methodology to predict vehicle impacts on training lands

Tactical mobility analysis techniques were merged with land management strategies to assess potential impacts of vehicle operations on training areas for rangeland planning and management. A vehicle mobility analysis was performed for a suite of vehicle types using the NATO Reference Mobility Model (NRMM II). Input parameters include terrain information (soil type, slope, vegetation, surface roughness, soil strength), terrain surface condition based on climate (terrain strength, freeze–thaw, moisture content, snow cover), and vehicle specifications (tire, power train, weight on each axle, ground clearance, dimensions, ride). The vehicle performance was spatially mapped over the terrain for different seasons of the year and used to calculate the maneuverable acreage, which was compared to acreage needed for training requirements. This can be related to land capability based on expected training impact (Maneuver Impact Miles, MIM) and Land Condition Curves which link training density to land condition. This methodology can be used to determine the suitability of training lands and the degree of land management or rehabilitation expected. The methodology was applied to the transformation of the Alaska training lands to support a new brigade unit called the Stryker Brigade Combat Team (SBCT3), but is equally useful for other training areas and military units. For summer use, Alaska training lands are capable of supporting four times the projected training requirements. For winter, when the ground is frozen, more than 10 times the area needed was available.     

长江河口滨海地区冲填土对地面沉降效应——以上海市临港新城为例

长江河口滨海地区广泛分布有大量的冲填土,由于其形成时间短,具有欠固结特性,因此对地面沉降影响较大。本文首先阐述上海市临港新城区冲填土分布特征,并按其填料不同将其分类后计算出不同种类冲填土大面积堆载所引起下部土层的地面沉降量和冲填土本身固结产生的沉降量,并与总的地面沉降量相比较,得出结论,并对进一步开展工作提出建议。     

Assessing and predicting changes in vegetation cover associated with military land use activities using field monitoring data at Fort Hood, Texas

We assessed short-term impacts of changes in military training load on vegetative cover at Fort Hood, TX. From 1989 to 1995, permanent field transects were monitored for vegetative cover and land use disturbance using standard army monitoring methods [Land Condition Trend Analysis (LCTA)]. Land use intensity (training load) was quantified and used to develop a model to predict future vegetation cover values. We found that standard Army monitoring methods detected changes in installation resources associated with changes in training load. Increased training loads were associated with increased measures of disturbance, decreased ground cover, and decreased aerial vegetative cover. We found that the spatial pattern of disturbance and vegetation cover remained relatively constant over the study period despite large variations in overall training load. Our model used the consistency in spatial cover patterns over time and the strong relationship between training load and vegetation cover to predict the impact of future training loads on vegetation.     

Duality in land rental problems

Land rental problems describe situations where one tenant demands land from several lessors. The way lessors rent their land can be seen as equivalent to a bankruptcy problem. We extend the idea of self-duality in bankruptcy problems to land rental problems. We provide a complete characterization of the family of rules that satisfy self-duality. Moreover, self-duality is enough to assure the proportional land share among lessors. Adding other reasonable properties, we pick up a single rule.     

“家庭”还是“市场”:关于提高农民收入问题的再思考——基于广西壮族自治区南宁市武鸣县小梁村的农户调查

通过梳理我国在增加农民收入上所采取的有关政策、效果评价,总结了学者们对农民收入问题认识的变迁过程,提出农民的收入是其劳动力与其他生产要素相结合的结果,即农民收入是否能够有效地提高,关键在于农民是否可以并且是否愿意灵活地分配其劳动力与其他生产要素相结合。通过运用农户模型(AHM),并基于对广西农户的调研数据进行的线性规划分析,本文得到以下三点结论:首先,专于经济作物种植的农户在收入上仍有较大的增长空间,农业收入依然是他们收入来源和收入增长的主要力量。其次,在实现最优生产决策的前提下,农民仍有大量的劳动时间未被充分利用,这为农民灵活地支配劳动提供了可能。再次,农民是否选择利用剩余的劳动时间离开土地并从事非农产业活动还要根据其种植农作物的品种决定。最后,根据结论提出了相关的对策和建议。