REELFOOT LAKE SEDIMENTATION RATES AND SOURCES1

ABSTRACT: The three basins of Reelfoot Lake, which is located in northwestern Tennessee, were investigated using the Cs-137 tracer technique to determine rates of sediment deposition and to estimate the time before the basins will fill with sediment. Blue Basin, the largest of the three basins with 2922 ha, had an average annual sedimentation rate of 0.9 cm/yr from 1984 to 1984. The basin will become too shallow for most boating and recreational activities in about 200 years. Buck Basin, the central basin with 774 ha, had an average annual sedimentation rate of 1.1 cm/yr and will become too shallow for most recreational uses in about 100 years. Upper Blue Basin, the most upstream and smallest basin with 439 ha, had an average annual sedimentation rate of 1.7 cm/yr and will become too shallow for most recreational uses in about 60 years. Two important sources of sediment to Reelfoot Lake are erosion from a large number of soybean fields and channelization of many of the streams that flow into the lake. Changes in land management that would reduce erosion could increase the time the lake would remain usable for recreational activities.     

Soil erosion in developing countries: A politicoeconomic explanation

Soil erosion is accelerating in developing countries of Asia, Africa, and Latin America. It has threatened the livelihood of millions of peasants, for agriculture is their economic mainstay. A probe into the forces causing erosion reveals that the elite’s resolve to accumulate ever more wealth and to maintain, consolidate, or expand their sociopolitical power and the necessity of the poor to fulfill their requirements of food, fuelwood, and fodder are the two major factors accelerating soil erosion. Unless the vast masses of poor people are integrated into the national mainstream through the implementation of equitable and redistributive development policies, it is impossible to control the accelerating rate of soil erosion and thus to achieve the objective of sustainable development. In this article, the phenomenon “soil erosion” is studied with the sol e focus on causation through anthropogenic factors.     

黄土丘陵沟壑区土壤侵蚀专家系统试验研究

本文介绍了黄土丘陵的沟壑区土壤侵蚀专家系统的建造原理与方法.系统采用压缩编码方式存贮各种地学图形与遥感图象数据,具有效据与图象的存贮更新、查询检索、分析处理、图象显示和自动制图功能.该系统可对黄土地区的土壤侵蚀进行准确、快速的预测、预报,并对土壤侵蚀的综合治理,水土保持规划提出几种可行性建议供用户选择。用该系统对山西省离石县王家沟流域羊道沟的土壤侵蚀进行了试验研究,并对试验结果进行了系统评价。     

毁林与汉代居延垦区的衰落

本文根据历史史料，阐明了汉代居延垦区由兴旺发达到衰落的历史原因。进一步说明了乱破滥伐森林带来的恶果。开发大自然必须遵循自然规律，切不可盲目蛮干，毫无克制。     

ECONOMIC EFFECTS OF SOIL CONDITIONS ON FARM STRATEGIES TO REDUCE AGRICULTURAL POLLUTION1

ABSTRACT: Utilizing predictions of pollutant movement generated by the CREAMS model, the economics of reducing field losses of sediment and nitrate percolation were compared between two soil types on each of two slopes common to the Upper Eastern Shore of Maryland. The soils considered were Matapeake silt loam and Sassafras sandy loam textures on field slopes of 3.5 percent and 7.5 percent. A representative cash grain farm was used as a basis of comparison. Under assumptions of profit maximization, economic optimal cropping systems varied by slope. Results further indicated that relative cost-effectiveness of sediment or nitrate percolation control varied by soil type for both slopes considered. Unit costs of sediment control were less on silt loam soils, while unit costs of nitrate percolation control were less on sandy loam soils.     

中国海岸侵蚀特点及侵蚀加剧原因分析

中国海岸侵蚀具有普遍性、多样性和加剧发展等三个特点，侵蚀岸线长度占全国大陆岸线的１／３以上，尤以渤海和黄海沿岸较重。但因沿海泥沙来源丰富、堆积条件较好，使总体侵蚀强度通常稍轻于国外许多海岸。中国海岸的侵蚀因素有海平面上升、风暴潮加剧、入海泥沙减少和多种不合理的人为开发活动等９种，其中７种与全球变化有直接或间接关系。它们主要通过增强海洋动力作用、减少沿岸泥沙和降低海岸稳定性三个原因，加剧海岸侵蚀。     

山东省海岸侵蚀灾害研究

本文根据大量外业调查资料,阐述了山东海岸侵蚀灾害状况.并探讨了山东海岸侵蚀原因,认为自然条件的变化和人类活动的影响是引起海岸侵蚀的原因,作者强调指出,人类活动在海岸侵蚀和灾害中起更重要的作用。     

Sediment–Water Interactions in an Eroded and Heavy Metal Contaminated Peatland Catchment,Southern Pennines,UK

Atmospherically deposited lead in the upper layer of the heavily eroded peatlands of the Peak District, southern Pennines, UK, reaches concentrations in excess of 1,000 mg kg⁻¹. Erosion of the upper peat layer in this region is releasing lead, associated with eroded peat particles, into the fluvial system. Understanding the process mechanisms that control dissolved lead concentrations in contaminated peatland streams is vital for understanding lead cycling and transport in peatland streams. Many headwater streams of the southern Pennines recharge drinking water reservoirs. Measurements in the Upper North Grain (UNG) study catchment show that mean sediment-associated and dissolved lead concentrations are 102 ± 39.4 mg kg⁻¹ and 5.73 ± 2.16 μg l⁻¹, respectively. Experimental evidence demonstrates that lead can desorb from suspended sediments, composed of contaminated peat, into stream waters. In-stream processing could therefore account for the elevated dissolved lead concentrations in the fluvial system of UNG.     

公众可持续发展基本意识评价与分析--以地方21世纪议程南阳试点为例

具备可持续发展基本意识是公众参与可持续发展的前提和基础。采用问卷调查方法和GLM模型。以地方21世纪议程南阳试点为例，基于7765份调查问卷，论述了公众可持续发展基本意识的特点和人群差异。研究发现，公众可持续发展基本意识在年龄、职业、县（市、区）、城乡、收入等方面差异显著，但是在性别、地形方面差异不显著。在不增加消费成本的情况下，公众可持续发展基本意识与公众可持续发展行为取向显著正相关，但是在增加消费成本的情况下，则行为取向滞后。公众可持续发展基本意识评估值整体上较高。但仍有少部分人缺乏最基本的可持续发展知识和观念。