History and Development of the NRCS Lag Time Equation1

Abstract: Many of the hydrologic methods that are used in engineering practice today resulted from the Spring Flood of 1936, which blanketed the Northeastern portion of the United States. Because of the flood damage that was caused by this rainfall‐snowmelt event, many federal agencies including the U.S. Army Corp of Engineers and the Soil Conservation Service (SCS) implemented the hydrologic theories that were available in the literature at this time and developed hydrologic procedures for design flow estimation. Sherman had recently published his unit hydrograph theory in 1932, and later in 1938 Snyder, who had been charged by the Water Resource Council to develop a synthetic unit hydrograph, published his famous paper. The SCS unit hydrograph theory was developed by Victor Mockus in the late 1950s. Most if not all of the theories at that time reported the rainfall‐runoff process for floods as a surface phenomenon, and as such those theories all required some type of a timing parameter to estimate watershed response time. This article documents the development of the SCS lag equation.     

Mann-Kendall检验及其在河流悬沙浓度时间序列分析中的运用

探讨了Mann-Kendall非参数秩次相关检验在时间序列分析方面的应用,并以云南省文山州盘龙河为例,把它运用到河流悬沙浓度时间序列的趋势分析和突变分析研究中。结果表明：①M-K检验同样适用于河流悬沙浓度的趋势与突变分析;②盘龙河自20世纪60年代初至90年代末河流悬沙浓度一直表现为波动上升趋势,1999年后有下降的迹象;③盘龙河的河流悬沙浓度自20世纪60年代以来存在着两个明显的突变点,其一在1973年,其二在1999年。     

大同市地表水“十五”与“九五”期间污染状况比较及原因分析

“十五”期间大同市地表水氨氮、总汞、六价铬、砷等项目比“九五”期间有所恶化，而生化需氧量、化学需氧量、镉等项目有所好转，其它项目变化不大。主要原因是随着经济的发展，排污企业日益增多，因此需要各排污单位增强环保意识，严格管理污水处理设施，杜绝偷排和超标排放现象，加快城市污水处理厂建设步伐。     

Variation in Sensitivity of Aquatic Species to Toxicants: Practical Consequences for Effect Assessment of Chemical Substances

5 –10⁶ times higher compared with less sensitive species. The use of assessment factors in effect assessment procedures may lead to an underestimation of effects on the more sensitive species. For many priority pollutants there is little information on their ecotoxicity. Predictive techniques are needed to compensate for this lack of data. Knowledge of the relation between modes of action of compounds and interspecies variation in sensitivity should be integrated in risk assessment procedures in order to make more efficient use of the limited financial resources available.     

无除湿预处理采样法测定烟气中低浓度SO2

针对海水脱硫后的烟气具有SO2浓度低、湿度大、温度低的特点，提出了在烟道内无需除湿预处理的直接采样测定SO2的方法，解决了国标法进行除湿采样或使用较先进仪器直接脱水测定带来的测定结果偏低问题。实际应用表明，谊法比在烟道外使用的除湿法更加准确、经济。     

油田采出水过滤进水中不同粒径悬浮物的质量分布

采用已知孔径的微孔过滤器,对油田采出水的过滤进水进行了筛分,分析了悬浮物的质量浓度,并同步测定了颗粒体积浓度和几何特征值。除了D[v,0.5]具有指标性意义外,粒度分析结果并不能完全代表过滤等工艺的分离精度。悬浮物几何特征值、体积浓度和质量含量降低率不是同步的,其中质量浓度降低幅度最小。当粒径小于4μm的悬浮物质含量超过3mg/L时,难以被目前普遍采用的过滤工艺去除。应选择与膜过滤类似的更精密的工艺技术,才能最终达到采出水回用标准。     

某金铜矿山含铜酸性废水处理研究

采用石灰调pH—铁屑置换—石灰沉淀处理工艺对废水进行试验，结果表明，采用该工艺处理含铜酸性矿山废水，不仅能使处理后的水满足排放标准，同时还能回收废水中的铜。     

时变条件下的有害物品运输的人口风险分析

随着工业的发展 ,有害物品运输量在逐年增加 ,有害物品对于人类威胁也在加大 ,有害物品运输的风险问题受到了广泛的关注。由于有害物品运输中 ,路径周围的人口密度随着时间的变化而变化 ,进而影响在运输过程中的人口风险。笔者在有时变情况下 ,对有害物品运输人口风险进行了分析 ;建立了估计人口风险的模型 ;获得了有害物品运输中的最小人口风险以及最佳出发时间 ;进一步完善了有害物品的运输的风险分析 ;为如何减少有害物品运输的人口风险提供了依据。     

Quantifying dry NH3 deposition to an ombrotrophic bog from an automated NH3 field release system

Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH₃ inputs to moorland vegetation growing on a bog at a field scale, a field release NH₃ fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH₃ from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s^–1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH₃ concentration with distance from the source. In a complementary study, using a NH₃ flux chamber system, the relationships between NH₃ concentrations and cuticular resistances were quantified for a range of NH₃ concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH₃ concentration from 11 s m^–1 at 3.0 g m^–3 to 30 s m^–1 at 30 g m^–3. The NH₃ concentration data and the concentration-dependent canopy resistance are used to calculate NH₃ deposition taking into account leaf surface wetness. The implications of using an NH₃ concentration-dependent cuticular resistance and the importance for refining critical loads are discussed.     

长江下游氮、磷含量变化及其输送量的估计

根据在１９９７和１９９８年内对长江干流大通站河水的３次采样分析,结合该站１９６２～１９９０年的水质资料,对长江下游Ｎ、Ｐ含量变化及其输送量进行研究．总氮、总磷的平均含量分别为１．６～２．２ｍ ｇ·Ｌ^-1和０．１１～０．１５ｍ ｇ·Ｌ^-1,Ｎ 以ＮＯ^-_３ －Ｎ 为主,约占７６％ ,其余主要为溶解有机氮和颗粒氮;Ｐ以颗粒态为主,占９５％ 以上．从５、６月到８月,ＮＯ^-_３－Ｎ含量是逐渐降低的,ＤＯＮ含量有较大幅度的上升,ＰＮ、ＰＰ及ＴＰ含量也有所增高．与历史资料相比,长江大通站溶解无机氮（ＤＩＮ）和ＰＯ^3-₄－Ｐ含量还在不断上升,Ｎ、Ｐ含量的上升与流域化肥施用量变化趋势一致．１９９８年夏季洪水期间,约有７９．９５万ｔＮ和８．３６万ｔＰ从大通站向下游输送,其中ＤＩＮ与生物有效磷（ＢＡＰ）比值远高于浮游植物生长的Ｐ限制值.