EVALUATING RELIABILITY OF STORAGE SCHEMES WITH DENDROHYDROLOGY AND THE HURST PHENOMENON1

ABSTRACT: The mean annual flow at a damsite during a water project yield study of several decades may differ considerably from the mean flow of several hundred years. The frequency of the most severe droughts of record may be much different than apparent from the historical record as well. Dendrohydrology and the Hurst Phenomenon provide means to evaluate the validity of the study period for project reliability analysis. The most severe hydrologic drought (1928–1934) affecting the watersheds of the Sacramento River and tributaries in Northern California during the 75-year period 1906–1980 was also the worst drought in 421 years (1560–1980). In contrast, the most severe drought (1945–1951) in the Santa Ynez River watershed in Santa Barbara County, California, during the 62-year period 1918–1979 was the ninth worst drought in 443 years (1537–1979). Thus, in one case the drought risk indicated by the dendrohydrologic time series would actually be less; in the other, actual risk would be greater than perceived from the historical record. In the absence of a dendrohydrologic prehistoric time series, Hurst Phenomena would have provided clues to this outcome. Hurstian plotting of the accumulated deviation from the mean for long time series facilitates observation of the wet-dry regime of the examples and identification of characteristics that should be accounted for in water development planning.     

NUTRIENT CONTRIBUTION OF NONPOINT SOURCE RUNOFF IN THE LAS VEGAS VALLEY1

ABSTRACT: A Geographic Information System (GIS) based non‐point source runoff model is developed for the Las Vegas Valley, Nevada, to estimate the nutrient loads during the years 2000 and 2001. The estimated nonpoint source loads are compared with current wastewater treatment facilities loads to determine the non‐point source contribution of total phosphorus (TP), total nitrogen (TN), and total suspended solids (TSS) on a monthly and annual time scale. An innovative calibration procedure is used to estimate the pollutant concentrations for different land uses based on available water quality data at the outlet. Results indicate that the pollutant concentrations are higher for the Las Vegas Valley than previous published values for semi‐arid and arid regions. The total TP and TN loads from nonpoint sources are approximately 15 percent and 4 percent, respectively, of the total load to the receiving water body, Lake Mead. The TP loads during wet periods approach the permitted loads from the wastewater treatment plants that discharge into Las Vegas Wash. In addition, the GIS model is used to track pollutant loads in the stream channels for one of the subwatersheds. This is useful for planning the location of Best Management Practices to control nonpoint pollutant loads.     

HYDROLOGIC LANDSCAPES ON THE DELMARVA PENINSULA PART 2: ESTIMATES OF BASE-FLOW NITROGEN LOAD TO CHESAPEAKE BAY1

ABSTRACT: Base-flow samples were collected from 47 sampling sites for four seasons from 1990–91 on the Delmarva Peninsula in Delaware and Maryland to relate stream chemistry to a “hydrologic landscape” and season. Two hydrologic landscapes were determined: (1) a well-drained landscape, characterized by a combination of a low percentage of forest cover, a low percentage of poorly drained soil, and elevated channel slope; and (2) poorly drained landscape, characterized by a combination of an elevated percentage of forest cover, an elevated percentage of poorly drained soil, and low channel slope. Concentrations of nitrogen were significantly related to the hydrologic landscape. Nitrogen concentrations tended to be higher in well-drained landscapes than in poorly drained ones. The highest instantaneous nitrogen yields occurred in well-drained landscapes during the winter. These yields were extrapolated over the part of the study area draining to Chesapeake Bay in order to provide a rough estimate of nitrogen load from base flow to the Bay and its estuarine tributaries. This estimate was compared to an estimate made by extrapolating from an existing long-term monitoring station. The load estimate from the stream survey data was 5 ± 10⁶ kg of N per year, which was about four times the estimate, made from the existing long-term monitoring station. The stream-survey estimate of base flow represents about 40 percent of the total nitrogen load that enters the Bay and estuarine tributaries from all sources in the study area.     

SIMPLE MEASUREMENTS OF SOIL SURFACE MICRORELIEF CHARACTERISTICS1

ABSTRACT: Soil surface roughness and the topographic orientation of microrelief influence runoff and water storage. Distances measured following the surface of the microrelief and horizontally across the area with the microrelief can be used with the number of microridges or microhills to estimate the average cross-sectional areas of the depression, the microslope angles, and crest heights. Microridge sideslope angles which effect the rate of runoff were estimated reasonably well in field plots by the method.     

海洋污损硅藻附着强度的定量测定

以海洋底栖硅藻新月菱形藻MMDL533作为模型污损物种,利用显微镜-图像分析软件、平行平板流动装置测定了其在羟基化玻璃表面及改性玻璃上的附着性质。研究表明,环境温度为20℃时,新月菱形藻MMDL533在羟基化玻璃表面的附着量最大,在1 h的接触时间后达到87±9/mm2;同时,其附着量随着接触时间延长而变大,并在3 h后达到一个较为稳定的值(110±15/mm2左右);当用水流冲刷后细胞的移除率来表征细胞在特定表面的附着强度时,新月菱形藻MMDL533的附着强度随着表面接触角逐渐增大,并在80°左右达到最大值,然后呈下降趋势。     

热镀锌板表面硅烷处理耐蚀性能的研究

将镀锌钢板经表面处理后涂覆硅烷,研究成膜后的耐蚀性能。在3.5%NaCl溶液中的电化学极化曲线测试和交流阻抗表明,涂覆硅烷膜后,硅烷膜的存在能够明显地抑制腐蚀过程中的阴极和阳极反应,使电荷转移阻力大增,显著降低了锌的腐蚀速率,耐蚀效果较好。初步讨论了硅烷膜的成膜及耐蚀机理。     

Concentration level and geographical distribution of nitrobenzene in Chinese surface waters

Nitrobenzene was reported to occur at relatively high concentrations in some Chinese surface water and to cause an environmental pollution event in 2005.To map the distribution of nitrobenzene in the Chinese surface water throughout China,surface water samples were collected from over 600 sites in the 7 major watersheds and three drainage areas.The samples were analyzed for concentration of nitrobenzene.Overall,nitrobenzene was more frequently detected at higher concentrations in the rivers of North Chin...     

纤维素酶液体发酵工艺条件的响应面分析优化

借助于MINITAB软件,采用Plackett-Burman试验设计法及响应面法分析,对纤维素酶高产菌康氏木霉Trichoderma koningii P12进行了发酵工艺条件的优化研究。首先利用Plackett Burman试验设计筛选出影响产酶的三个主要因素,即装液量、稻草粉浓度和麦麸浓度。在此基础上用最陡爬坡路径逼近最大响应区域,再利用Box-Behnken试验设计及响应面分析法进行回归分析。结果表明,装液量和稻草粉浓度与纤维素酶活存在显著的相关性,通过求解回归方程得到优化发酵条件:当装液量56.5mL、稻草粉浓度37.4g/L和麦麸浓度11.3g/L时,纤维素酶产量达到63.32U/mL。经三批培养验证,预测值与验证试验平均值接近,在此优化条件下纤维素酶活提高了96.7%。     

湘潭市地表雨水径流污染的特性研究

目前,由于地表雨水径流污染日益严重,造成的损失也越来越大,人们的目光逐渐从传统的点源污染转向面源污染(即非点源污染)。为防止地表雨水径流污染对地表水体的污染,探讨城市地表径流的污染特性,本文对晴天时湘潭市雨湖区道路路面沉积物的粒径分布及污染潜力进行了测试,对雨天时湖南科技大学校园内家属区一道路的雨水径流也进行了测试,旨在为相关部门治理地表污染提供一定的参考与依据。     

氢化物发生原子荧光法测定地表水和饮用水中的痕量砷、汞、硒

文章研究了用SK-2002 AFS analyser氢化物发生原子荧光法测定地表水和饮用水中的砷、汞、硒的测定。在5％的酸度条件下加入5％硫脲＋5％抗坏血酸,20g／L的硼氢化钾为还原剂,调整仪器的空气和辅气流量及分析条件为文中条件,取水样中分别添加砷,汞,硒,使它们的浓度分别为2μg/L,0．4μg／L,4μg／L,连续测定12次,以砷,汞,硒的相对标准偏差分别为0．4％,1．1％,1．2％。取水样加入As,Hg,Se标准分别为2．0ng,0．6ng,4．0ng,测定的添加标准回收率分别为99．5％,97．5％,95．8％。研究结果表明,该方法操作简便,快速,灵敏,干扰少,检出限低等特点,适合于测定地表水和饮用水中砷,汞,硒的测定。