EFFECTS OF SLUDGE AND CHEMICAL FERTILIZER APPLICATION ON RUNOFF WATER QUALITY1

ABSTRACT: Simulated rainfall was used on experimental field plots to compare the effect of chemical fertilizer and sludge application on sediment, nitrogen, and phosphorus in runoff from no-till and conventional tillage systems. Chemical fertilizer application under the no-till system resulted in the least amount of total N and P in surface runoff. However, sludge application under the no-till system resulted in the least amount of NO₃-N and sediment in surface runoff. The worst water quality scenarios were observed when either sludge or chemical fertilizer were surface-applied under a conventional tillage system. Nitrogen losses from the conventional tillage system were minimized when sludge was incorporated into the soil. However, phosphorus and sediment yield from such a system were significantly higher when compared to phosphorus and sediment yield from the no-till system. The results from this study indicate that the use of sludge on agricultural land under a no-till system can be a viable alternative to chemical fertilizer for nitrogen and phosphorus control in runoff. A more cautious approach is recommended when the sludge is incorporated into the soil in a conventional tillage system because of potential for high sediment and phosphorus yield in surface runoff.     

ESTIMATING MARYLAND CRITICAL AREA ACVS IMPACT ON FUTURE NONPOINT POLLUTION ALONG THE RHODE RWER ESTUARY1

ABSTRACT: This paper presents the results of an investigation of the effects of the Maryland Critical Area Act on generation of non-point source loads of phosphorus, nitrogen, and sediment to the Rhode River estuary. The Simple Method model, the Marcus and Kearney regression model, and the CREAMS model were used to estimate annual loads under: (1) present conditions, (2) maximum land use development allowable under the Act, and (3) two sets of future land use conditions that might occur if the Act were not in place. Results indicate that the Critical Area Act can reduce the present generation of nonpoint nutrient and sediment loadings 20–30 percent from the regulated area. These reductions can occur while preserving agricultural lands and allowing limited residential and urban development. The decrease in nutrient loadings is primarily dependent upon implementation and enforcement of agricultural best management practices (BMPs). The BMPs could reduce present agricultural nutrient loadings by 90 percent to a level comparable to loadings from residential areas. The estimated effectiveness of the Critical Area Act is even greater when compared to potential future nutrient loadings if development in the area remains unregulated. Unrestricted residential and urban development could increase nutrient loadings by 200 percent to 1000 percent as compared to controlled development under Critical Area Act guidelines. The Critical Area Act primarily prevents these future increases by severely limiting woodland cutting, with lesser results obtained by requiring urban BMPs.     

土地使用权出让与土地利用总体规划

本文在论述土地使用权出让和土地利用总体规划内涵的基础上,研究了两者作用和反作用的关系,提出了两者最终目标一致性的观点,并探讨了实践上相关的问题。     

SEASONAL OCCURRENCE OF ANNUAL FLOODS ON SMALL PENNSYLVANIA WATERSHEDS1

A study is presented of the months in which the instantaneous annual maximum discharges from 66 watersheds occurred. The 2,052 flood values were measured on areas ranging from 2.4 through 214 square miles. The longest record was 60 years; the three shortest were 20. Pictorial results show both the number of floods for each month and individual discharges relative to the mean flood. A parameter which is weighted in this manner accounts for both the incidence and the magnitude of floods. Peculiarities of flood-timing charts, based on this parameter, are discussed with respect to watershed size, soils, geology, and land use. After anomolous watersheds had been assigned to special categories, flood-timing charts from most records exhibit a regional dichotomy dividing eastern from western Pennsylvania.     

基于遥感与GIS的土地利用动态变化研究

土地是人类社会经济活动的载体；土地利用是指人类对作为生产生活资料的土地的利用方式和强度；而土地利用动态变化则反映了土地利用方式的发展变化趋势。土地利用动态变化在数量，方式，强度，结构和趋势等方面存在很大的差异。全面，客观地反映土地利用动态变化有利于正确认识当前土地利用中合理和不合理的利用方式，为制定长期，可持续发展的土地管理和土地规划提供依据。遥感技术提供巨大而丰富的信息源，GIS技术具有强大的数据处理，空间分析等功能，二者的结合有着传统方式无法比拟的优越性，具有周期短，效率高，费用低等特点，在土地利用变化监测中发挥着巨大的作用。制定详细的技术手段，对重庆市15年间的土地利用及其动态变化在时间序列和空间序列上加以分析，阐明这种变化的外在表象，即耕地，林地的减少和城镇用地的增加；同时分析这种变化的内在驱动力主要为自然环境（坡度，高程，土壤等）和人文要素（经济条件与人口压力等）。为国土资源的有效可持续利用提供决策依据。     

A MODELING APPROACH FOR OPTIMUM SEDIMENT DETENTION POND DESIGN1

ABSTRACT: A design procedure to determine optimum size for a sediment detention pond is presented. The procedure is based on simulating the sediment removal efficiency of the pond in conjunction with temporal variations in rainfall and potential land use and/or management options. The simulation procedure is based on a combined probabilistic-deterministic modeling approach. The probabilistic model generates daily rainfall with hourly increments for a selected site. The deterministic model simulates sediment yield and concentration for drainage area (pond inflow) and sediment trapping efficiency of the pond. The sediment yield and concentration in pond effluent is estimated from the difference between sediment inflow to the pond and sediment trapped by the pond. As an example, the procedure is applied to determine optimum design for a sediment detention pond in a surface mined area using several pond design options and alternative mining operation/land reclamation strategies.     

红壤丘陵区土地利用变化对土壤质量影响

以鄂南红壤丘陵典型区的三个村为代表 ,应用地理信息系统对 1981和 1998年两个时期的土地利用变化和土壤质量进行对比研究 ,分析了土地利用变化对土壤质量的影响。结果表明 :研究区土地利用结构总体上具有农业型特点 ,17a间水田减少了 2 1% ;其余的利用方式则有不同幅度的增加 ,居民地、水域、林地、园地和旱地增加了 4 2 .2 %、99.6 %、8%、5 6 .8%和 8%。土壤质量有从优劣两端向中等靠拢的趋势 ,17a后 、 、 和 等地面积分别减少 18.6 %、12 .2 %、2 9.6 %和 2 5 % ; 等地增幅达 5 1.9%。土地利用方式及管理措施是影响土壤质量演变方向和强度的关键因子 ,园地和林地的土壤质量大多得到明显改善 ,水田的Δ SQI多数呈下降的趋势 ,旱地的土壤质量变化比较复杂 ,与土地利用结构相关。依此 ,本文探讨了定向培育土壤质量的途径     

日本城市化中的耕地变动与经验

日本是一个国土面积狭小、耕地资源稀缺的国家。然而，在人均土地资源极为有限的条件下，日本在较短时间内达到了高度城市化，同时付出了较小的用地代价。在其整个城市化进程中，日本还出现了三个耕地面积增长时期。尽管各时期增长原因不尽相同，但却反映出耕地面积变动与城市化发展的密切关系。事实表明，日本选择了一条节约有限土地资源的城市化发展道路，这些经验对我国城市化发展中的耕地利用与保护有积极的借鉴意义。     

城市土地资产经营新思路探讨

自1996年上海市成立第一家土地收购储备机构——土地发展中心后，全国各大城市已纷纷效仿它的成功经验。截止2001年8月不完全统计，全国已有大小不同的土地收购储备机构669家。实践证明，土地收购储备机制在盘活城市存量土地，促进土地集约利用，保障城市土地资产的保值增值等方面成绩卓著。然而，实践过程中，土地收购储备机制的运作也暴露出不少问题。本文通过对这些问题的分析，提出了引进公司制度完善土地收购储备机制，合理运营城市土地资产的新思路。     

关于中国土地资源人口承载力问题的思考

土地资源的人口承载力问题也就是生存空间问题,它关系到人类未来的生存与发展问题,历来受学术界的注目。20世纪70年代联合国粮农组织(FAO)曾主持了一项大型的发展中地区土地资源人口承载力问题的研究,80年代后期,中国科学院—国家计委自然资源综合考察委员会也主持了一项大型的中国土地资源生产能力及人口承载量研究。相应地还有一系列有关中国未来的生存与发展和人口承载力问题的探讨。本文从中国人地关系变化的角度介入这一讨论,分析中国远期的土地资源是否超载的问题。