EFFECTS OF URBANIZATION ON BASE FLOW OF SELECTED SOUTH-SHORE STREAMS,LONG ISLAND,NEW YORK1

ABSTRACT: Hydrograph analysis of six streams on the south shore of Long Island indicates that eastward urbanization during the last three decades has significantly reduced base flow to streams. Before urbanization, roughly 95 percent of total annual stream flow on Long Island was base flow. In urbanized southwestern Nassau County, storm water sewerage, increased impervious surface area, and sanitary sewerage have reduced base flow to 20 percent of total stream flow. In an adjacent urbanized but unsewered area in southeastern Nassau County, base flow has decreased to 84 percent of total annual stream flow. In contrast, base flow in two streams in rural areas has remained virtually constant, averaging roughly 95 percent of total annual flow throughout the 1955-70 study period. Double-mass curve analysis of base flow as a percentage of total annual stream flow indicates that (1) changes in stream flow characteristics began in the early 1960's in the sewered area and in the late 1960's in the later urbanized, unsewered area, and (2) a new equilibrium has been established between the streams in the sewered area and the new hydrologic characteristics of their urbanized drainage basins.     

INTERDISCIPLINARY MODELING IN THE ANALYSIS OF THE SALINITY PROBLEMS OF THE SAFFORD VALLEY1

ABSTRACT: A groundwater quality change of +0.13 millimhos electrical conductivity was documented between 1940 and 1 972 in the Safford Valley. The change is attributable to four principal mechanisms: pumping-encouraged saline artesian aquifer leakage, natural recharge of the water table aquifer by saline waters, leaching of agricultural waters into the aquifer and the lateral flow of groundwater through saline lacustrine beds. A hydrologic study of the area has shown the first of these mechanisms to be predominant. Salinity modeling has shown three regions of salinity change, and salinity increase projections for each are determined. An economic analysis and an economic model are then combined with the physical model, yielding information as to when certain economic conditions are reached with respect to the salinity increase. This combined model shows that, based on projected salinity trends, cotton, the principal agricultural crop of the valley, will remain economical to cultivate for a significant time beyond the model's limit of prediction. Alfalfa, on the other hand, should go out of production in large areas of the valley by 1990, and not be under economical cultivation by 2040. A sociologic model, based on the cluster analysis of questionnaire data, shows an awareness of the salinity problems of the area but little concern over them. Interdisciplinary model based salinity control regulations are made.     

EXPERIMENTAL DREDGING TO CONVERT LAKE BOTTOM FROM ABIOTIC MUCK TO PRODUCTIVE SAND1

ABSTRACT: Conversion of muck to sand bottom was tested to increase benthic production in two eutrophic Florida lakes, and preliminary results indicate that benthos will be increased in areas converted to sand. Muck removal with a specially designed dredge, or “Mudcat,” was tested in Trout Lake. The Mudcat removed 41,650 cu. yds. of muck and exposed 17 acres of sand bottom, but 10 of those acres developed thin layers of muck, which proved too soft to be picked up by the Mudcat. Consequently, only 7 acres were satisfactorily converted. Bottom redistribution with a suction-type dredge was tested in Lake Carlton, and 14 acres were converted from muck to sand. Sand covered with muck was pumped from midlake areas to more peripheral areas of the lake where water depths were 11 to 13 feet and muck layer about 1.5 feet deep. The bottom was built up to an elevation above the previous muck elevation. Several methods for depositing the sand were tested. Level areas of sand fill developed accumulations of muck from fallout following dredging activity. Piles or dunes provided the best cost-return ratio. The bottom in filled areas changed very little during a 1½ year period following filling.     

乌鲁木齐市大气环境质量现状及其变化趋势分析

本文对乌鲁木齐市大气环境质量及其发展趋势作了简要的分析,说明目前市大气属煤烟-沙尘型污染区,氮氧化物和二氧化硫随着国民经济能耗的增加有发展的趋势,其它污染物仍稳定在目前水平,或稍有下降.     

TOPSIS法在大气环境质量评价中的应用

应用多目标决策中的TOPSIS法(即逼近于理想解的排序方法)对湖南长沙等十城市的大气环境质量进行评价,并与欧几里德贴近度法和上海指数法相比较,认为该评价方法对比较多个城市(或多个监测点,下同)的大气环境质量的优劣,比欧几里德贴近度法和上海指数法均优越.     

Risk assessment and binding mechanisms of potentially toxic metals in sediments from different water levels in a coastal wetland

The excessive accumulation of potentially toxic metals (Pb and Cd) in coastal wetlands is among the main factors threatening wetland ecosystems. However, the effects of water table depth (WTD) on the risk and binding mechanisms of potentially toxic metals in sediments remain unclear. Here, sediments from different WTD obtained from a typical coastal wetland were evaluated using a newly developed strategy based on chemical extraction methods coupled with high-resolution spectroscopy. Our findings indicated that the WTD of the coastal wetland fluctuates frequently and the average enrichment factor for Pb was categorized as minor, whereas Cd enrichment was categorized as moderate. High-resolution spectroscopy techniques also demonstrated that organic functional groups and partly inorganic compounds (e.g., Fe-O/Si-O) played a vital role in the binding of Pb and Cd to surface sediments. Additionally, mineral components rather than organic groups were mainly bound to these metals in the bottom sediments. Collectively, our findings provide key insights into the potential health effects and binding characteristics of potentially toxic metals in sediments, as well as their dynamic behavior under varying sediment depths at a microscale.     

Rehabilitation of a lowland river: Reconciling flood defence with habitat diversity and geomorphological sustainability

Geomorphologically appropriate rehabilitation measures were proposed to enhance the in-stream environment of the lowland River Idle, north Nottinghamshire, UK. However, the River Idle has multi-functional management requirements including those of flood defence so environmental enhancement must be pursued without significantly increasing the flood risk. Hydraulic testing of rehabilitation proposals is complicated because of the stringent assumptions about flow and morphology in ‘traditional’ hydraulic models. While new generation two- and three-dimension hydraulic models may overcome some of these problems, they are extremely data intensive, require advanced modelling capabilities and are, therefore, very expensive to apply. Also, they do not yet predict morphology-flow interactions adequately. As an alternative, several simple hydraulic models were applied to test the rehabilitation proposals, based on a fitness-for-purpose criterion.BENDFLOW was applied to fine tune the optimal siting of measures and to estimate the additional near-bank scour generated by proposed bend re-profiling. HMODEL2 and the FCFA method were used to test the impact on local channel conveyance capacities and HECRAS was applied to simulate the impact of the proposals on regional flood defence. Indicative results from the testing suggested a maximum increase in near-bank scour of 0·15 m in re-profiled bends, a loss of approximately 10% in flood conveyance locally due to deflector installation or reed and tree planting, and a 0·12 m increase in flood stage within the reach for a 15 year flood. The modelling results were acceptable to the management authority as an indication of an acceptable compromise between flood defence and conservation interests, and construction of the measures followed in 1996. It is clearly that it will require the results of post-project monitoring to indicate whether compromises made to the rehabilitation initiatives in order to satisfy flood defence requirements have unduly reduced their environmental enhancement potential but, for assessing the proposed methods, the models are recommended for use other lowland river environments.     

Hazardous waste indicators for national decision makers

Indicators and indices are important tools that assist decision makers to formulate and implement plans for management at local, national and international levels. Four indicators for hazardous waste management are described that have recently been adopted within the United Nations framework of Indicators of Sustainable Development. Although these four indicators will be useful tools, the need for a broader range of policy-relevant qualitative and quantitative indicators, proxy indicators and indices is outlined. The argument is advanced that in order for all nations to better manage the range of hazardous waste issues, including waste generation, export/import and disposal, a set of innovative indicators and indices is required. Useful indicators and indices are described that could be used to link and quantify likely environmental, ecosystem and health impacts and risks especially from hazardous waste disposal. Indicators are also suggested that could be used to illustrate the shift in industrial strategy away from end-of-pipe processes towards waste recycling, cleaner production and integrated life-cycle analysis. It was concluded that until the lack of reliable and harmonized data on hazardous waste is addressed, indicator development and use by national and international decision makers cannot readily be implemented.     

胶带输送机防尘治理综合改进措施

叙述了胶带输送机现有防尘罩的不足及改进措施。