生态小区特征和指标体系探讨

保护和建设生态小区，推行生态细胞工程是自然生态工作的有力补充。对于目前出现的许多生态小区，中国尚无一套正式通用的生态小区考评指标体系。本文从生态学的角度出发，探讨了生态小区的概念、内涵与其特征，并以此为基础，提出了生态小区的考评指标体系，希望以此引导四川省生态小区的创建活动。     

INCREASED BASEFLOW IN IOWA OVER THE SECOND HALF OF THE 20TH CENTURY1

ABSTRACT: Historical trends in annual discharge characteristics were evaluated for 11 gauging stations located throughout Iowa. Discharge records from nine eight‐digit hydrologic unit code (HUC‐8) watersheds were examined for the period 1940 to 2000, whereas data for two larger river systems (Cedar and Des Moines Rivers) were examined for a longer period of record (1903 to 2000). In nearly all watersheds evaluated, annual base flow, annual minimum flow, and the annual base flow percentage significantly increased over time. Some rivers also exhibited increasing trends in total annual discharge, whereas only the Maquoketa River had significantly decreased annual maximum flows. Regression of stream discharge versus precipitation indicated that more precipitation is being routed into streams as base flow than as storm flow in the second half of the 20th Century. Reasons for the observed stream flow trends are hypothesized to include improved conservation practices, greater artificial drainage, increasing row crop production, and channel incision. Each of these reasons is consistent with the observed trends, and all are likely responsible to some degree in most watersheds.     

The Role of Soil Organic Carbon in Maintaining Surface Elevation in Rapidly Subsiding U.S. Gulf of Mexico Coastal Marshes

Subsidence is a primary factor governing marsh deterioration in Mississippi River deltaic plain coastal marshes. Marsh surface-water level relationships are maintained primarily through soil organic matter accumulation and inorganic sediment input. In this study we examined the role of soil organic matter accumulation in maintaining marsh elevation in a brackish Spartina patens marsh. Measured rates of soil organic accumulation were compared to plant biomass production and soil respiration (carbon dioxide and methane emission) at the study sites. The study demonstrated the importance of plant biomass production to soil organic carbon accumulation in maintaining viable Spartina patens marshes in sediment-deficient coastal environments. The role of Mississippi River freshwater reintroduction in maintaining conditions for organic accretion is discussed.     

GROUND WATER NITRATE REDUCTION IN GIANT CANE AND FOREST RIPARIAN BUFFER ZONES1

ABSTRACT: Ground water contamination by excess nitrate leaching in row‐crop fields is an important issue in intensive agricultural areas of the United States and abroad. Giant cane and forest riparian buffer zones were monitored to determine each cover type's ability to reduce ground water nitrate concentrations. Ground water was sampled at varying distances from the field edge to determine an effective width for maximum nitrate attenuation. Ground water samples were analyzed for nitrate concentrations as well as chloride concentrations, which were used as a conservative ion to assess dilution or concentration effects within the riparian zone. Significant nitrate reductions occurred in both the cane and the forest riparian buffer zones within the first 3.3 m, a relatively narrow width. In this first 3.3 m, the cane and forest buffer reduced ground water nitrate levels by 90 percent and 61 percent, respectively. Approximately 40 percent of the observed 99 percent nitrate reduction over the 10 m cane buffer could be attributed to dilution by upwelling ground water. Neither ground water dilution nor concentration was observed in the forest buffer. The ground water nitrate attenuation capabilities of the cane and forest riparian zones were not statistically different. During the spring, both plant assimilation and denitrification were probably important nitrate loss mechanisms, while in the summer nitrate was more likely lost via denitrification since the water table dropped below the rooting zone.     

对Janbu普遍条分法计算方法的改进

Janbu普遍条分法(或称严格Janbu法)是第一个基于任意形状滑面且考虑滑体所有平衡条件的边坡稳定性计算方法。该方法存在的严重不收敛问题一直困扰着边坡理论和工程界近半个世纪。本文基于Janbu普遍条分法的基本原理和假设,重新推导出数学上更为简洁的安全系数积分表达式,指出传统计算格式不易收敛性是推力二阶导数的不合理数值误差所致,应用数值平滑技术可减少这个误差,使计算过程稳定收敛。研究表明,改进后的Janbu普遍条分法不失为理论相对严格、工程较为实用的边坡稳定性计算方法。     

四川省珙县地质灾害特征及其防治措施分析

本文从珙县地质灾害的分布特征、影响因素、防治措施等方面作了较为深入的分析和探讨，以期对地质灾害区划和防治有所借鉴和参考。     

岷江上游半干旱河谷土壤成土特征研究：以大沟流域为例

岷江上游半干旱河谷位于新构造运动活动带，其土壤形成和发育过程有着鲜明的区域特征。本文结合该区域的自然地理特点，综合分析各成土因素和土壤性状，对该区域土壤的成土特征进行了深入的分析和研究。     

PESTICIDES AND PESTICIDE DEGRADATION PRODUCTS IN STORMWATER RUNOFF: SACRAMENTO RWER BASIN,CALIFORNIA1

ABSTRACT: Pesticides in stormwater runoff, within the Sacramento River Basin, California, were assessed during a storm that occurred in January 1994. Two organophosphate insecticides (diazinon and methidathion), two carbamate pesticides (molinate and carbofuran), and one triazine herbicide (simazine) were detected. Organophosphate pesticide concentrations increased with the rising stage of the hydrographs; peak concentrations were measured near peak discharge. Diazinon oxon, a toxic degradation product of diazinon, made up approximately 1 to 3 percent of the diazinon load. The Feather River was the principal source of organophosphate pesticides to the Sacramento River during this storm. The concentrations of molinate and carbofuran, pesticides applied to rice fields during May and June, were relatively constant during and after the storm. Their presence in surface water was attributed to the flooding and subsequent drainage, as a management practice to degrade rice stubble prior to the next planting. A photo-degradation product of molinate, 4-keto molinate, was in all samples where molinate was detected and made up approximately 50 percent of the total molinate load. Simazine, a herbicide used in orchards and to control weeds along the roadways, was detected in the storm runoff, but it was not possible to differentiate the two sources of that pesticide to the Sacramento River.     

特大型煤和瓦斯突出的地质条件及其成因

特大型煤和瓦斯突出危害极大，具有独特的发生条件，应专门研究。在全国９９ 次特大型煤和瓦斯突出详细研究的基础上，总结了特大型突出的一般特征及发生的地质和采矿条件，并给出了南桐矿区的几个临界值。对特大型突出地质条件的成因进行了较深入的探讨，提出了防止特大型突出的几点建议     

臭氧-生物活性炭深度处理黄浦江水源水中试研究

以黄浦江水源水厂的滤后水为试验对象，进行饮用水O3-BAC深度处理工艺影响因素的中试研完。针对进水水质的试验结果表明，最优臭氧投加量为3mg／L左右，空床停留时间为15min左右。试验结果可为工程设计提供有益的参考。