Cadmium in the terrestrial environment: Impact of long‐range atmospheric transport∗

Cadmium is supplied to Southern Norway in considerable amounts by atmospheric transport from other areas of Europe. This has caused a very marked increase of Cd levels in the natural environment in this area. Evidence of the main source areas is inferred from air concentration studies coupled to trajectory analysis. The extent of contamination is indicated from deposition studies and investigations of Cd in peat cores and surface soils, including soil profile distributions. The Cd content of vascular plants is substantially higher in Southern Norway than in areas farther north and further transfer in terrestrial food chains is occurring and may eventually lead to increased human exposure.     

Growth performance and range shift of the subalpine fir (Abies fargesii) in the Qinling Mountains,China

Trees in the subalpine environment, a particularly vulnerable area being the first to reflect climate changes, are most likely to show strong effects of climate variability. The aim of this study was to identify growth responses of subalpine fir (Abies fargesii) to climate variability, and investigate range shifts along an altitudinal gradient in the subalpine region of the Qinling Mountains, China. Standard correlation functional analysis showed different growth responses of fir trees to climatic variables between north and south aspects. In the north aspect, radial growth was significantly positively correlated with temperatures in early spring (February–April) and summer (July) of the current year, while radial growth was significantly positively correlated with temperatures in November and December of the previous year and early spring (February–April) of the current year in the south aspect. Analysis of age structure distribution displayed a decrease in number of mature fir trees and an increase in number of saplings along the altitudinal gradient on both aspects. Fir saplings/seedlings only occur in the treeline environment, and this fir population was significantly younger than that at lower elevations. Thus, fir trees show different radial growth patterns in response to climatic variability between north and south aspects, and age-class distributions along the altitudinal gradient imply an upward shift in range in the subalpine region during the past century in the Qinling Mountains of China.     

白石砬子自然保护区几种主要植被类型土壤入渗特性研究

为了深入研究辽东山区森林土壤的水源涵养功能,以白石砬子自然保护区内的6种主要植被类型下土壤为研究对象,采用野外双环试验和室内理化性质分析相结合的方法,研究了不同植被类型下土壤入渗能力及其与理化性质的关系。结果表明,不同植被类型土壤的初渗率、稳渗率、平均入渗率、渗透总量均表现为下层低于上层,最大值是最小值的近3倍;不同植被类型间土壤入渗能力差异较大,其中A层初渗率排列顺序为原生红松阔叶混交林>红松人工林>鱼鳞云杉臭冷杉林>农地>蒙古栎林>杂木林,B层初渗率排列顺序为鱼鳞云杉臭冷杉林>农地>杂木林>红松人工林>原生红松阔叶混交林>蒙古栎林,A层稳渗率排列顺序为红松人工林>鱼鳞云杉臭冷杉林>原生红松阔叶混交林>杂木林>蒙古栎林>农地,B层稳渗率以杂木林最大,为3.8 mm?min-1,原生红松阔叶混交林最小,仅为1.1 mm?min-1,其他4种植被类型土壤稳渗率几乎无差异,A层平均入渗率排列顺序为红松人工林>原生红松阔叶混交林>鱼鳞云杉臭冷杉林>杂木林>蒙古栎林>农地,B层平均入渗率排列顺序为杂木林>鱼鳞云杉臭冷杉林>红松人工林>蒙古栎林>农地>原生红松阔叶混交林,A层的渗透总量以红松阔叶混交林和红松人工林最大,蒙古栎林和农地相对较低,B层的渗透总量以杂木林最大,红松阔叶混交林最小;主成分分析评价的土壤入渗能力排序为红松人工林>鱼鳞云杉臭冷杉林>原生红松阔叶混交林>杂木林>蒙古栎林>农地,初渗率、稳渗率、平均入渗率和渗透总量等4个指标综合起来能够很好的表达土壤入渗能力,其主成分方差的累积贡献率为90.662%;不同层次土壤入渗速率与入渗时间均存在良好的幂函数关系;土壤的稳渗率、平均入渗率、渗透总量与非毛管孔隙度呈显著正相关关系,初渗率与非毛管孔隙存在相关性,但不显著。与容重存在负相关关系,但不显著。     

基于CVM的旅游相关资源价值评估总体范围扩展方法研究

条件价值评估法(CVM)是旅游相关资源价值评估的重要方法,其评估结果的准确性主要由支付意愿(WTP)或补偿意愿(WTA)和总体范围扩展两者决定。目前,国内外关于CVM方法的相关研究主要是针对提高WTP(或WTA)的准确性,而关于总体范围扩展方法的相关研究较少。国外旅游相关资源价值评估总体范围主要扩展为使用者,或资源所在区域的家庭,或资源所在邻近区域的家庭;国内主要扩展为使用者,或资源所在区域的居民,或资源所在区域的就业者,或全国范围的相关居民或就业者;这些总体范围扩展方法均存在一些缺陷。论文以调查样本信息为依据,提出了一种基于旅游相关资源关注度系数(用出游小区相对旅游率表示)的非使用者总体范围扩展方法和基于游客量的使用者总体范围扩展方法,并以舟山普陀金三角景区非使用价值评估为例,以2008年为评价基准年份,进行了实证分析。结果表明:普陀金三角旅游资源非使用价值为345.83×10⁶元/a,其中非使用者贡献159.21×10⁶元/a,国内使用者贡献184.17×10⁶元/a,国外使用者贡献2.45×10⁶元/a。并与国内外各种总体范围扩展计算的结果进行对比,该结果较为合理。     

THE TWO‐DIMENSIONAL UPLAND EROSION MODEL CASC2D‐SED1

ABSTRACT: The two‐dimensional soil erosion model CASC2D‐SED simulates the dynamics of upland erosion during single rainstorms. The model is based on the raster‐based surface runoff calculations from CASC2D. Rainfall precipitation is distributed in time and space. Infiltration is calculated from the Green‐Ampt equations. Surface runoff is calculated from the diffusive wave approximation to the Saint‐Venant equations in two‐dimensions. Watershed data bases in raster Geographical Information System (GIS) provide information on the soil type, size fractions, soil erodibility, cropping management, and conservation practice factors for soil erosion calculations. Upland sediment transport is calculated for the size fractions (sand, silt, and clay), and the model displays the sediment flux, the amount of suspended sediment, and the net erosion and deposition using color graphics. The model has been tested on Goodwin Creek, Mississippi. The peak discharge and time to peak are within ± 20 percent and sediment transport rates within ?50 percent to 200 percent.     

ISOTOPE HYDROLOGY DYNAMICS OF RIVERINE WETLANDS IN THE KANKAKEE WATERSHED,INDIANA1

ABSTRACT: Wetland restoration activities may disturb shallow ground‐water flow dynamics. There may be unintentional sources of water flowing into a constructed wetland that could compromise the long‐term viability of a wetland function. Measurement of naturally‐occurring isotopes in the hydrosphere can provide an indication of provenance, flow paths or components, and residence times or ages of wetland ground‐water flow systems. Hydraulic head measurements may not provide sufficient detail of shallow flow disturbances and can be complemented by analyzing isotopes in waters flowing through the wetland. Two north‐central Indiana wetlands in the Kankakee watershed are being studied to determine the adequacy of wetland restoration activities. The native LaSalle wetland and the restored Hog Marsh wetland have contrasting ground‐water flow regimes. The conservative water isotopes ¹⁸O, ²H, and ³H, and selected solute isotopes ¹³C, ¹⁴C, ¹⁵N, ³⁴S, ⁸⁷Sr, and 206–208Pb, demonstrate the complexity of ground‐water flow in Hog Marsh compared to the established flow regime at the LaSalle wetland.     

SELECTION OF APPROPRIATE EVAPORATION ESTIMATION TECHNIQUE FOR CONTINUOUS MODELING1

ABSTRACT: The importance of evaporation in hydrologic modeling has been investigated by analysis of water budget at various scales and application of a water management model at plot scale. The data at all scales indicate that evaporation constitutes a major hydrological output. Accurate determination of watershed evapotranspiration depends upon appropriate accounting for the various components of evapotranspiration and their areal and temporal variability. An application of a water management model has revealed that the ranking of the sensitivity of input parameters depends upon the method of determination of evapotranspiration.     

REMOTE MONITORING OF SELECTED GROUND‐WATER DOMINATED LAKES IN THE NEBRASKA SAND HILLS1

ABSTRACT: The Landsat‐Muitispectral Scanner (MSS) data were used to measure lake area fluctuations (1972–1989) for 130 ground‐water dominated lakes in the Western Lakes Region of the Nebraska Sand Hills. In general, the pattern shown in lake area hydrographs was similar to that for in‐situ lake elevations. In‐situ lake‐elevation data verify that remote monitoring of surface‐area fluctuations, even at relatively coarse spatial resolution, is not only practical and useful, but also it elucidates the hydrologic characteristics of groundwater‐dominated lakes of the Sand Hills. The apparent differences in behavior between lakes in the northern and southern portions of the study area may be related to both their location in the regional ground water system and the substantial local hydrologic complexity.     

BIODEGRADATION OF DISINFECTION BYPRODUCTS AS A POTENTIAL REMOVAL PROCESS DURING AQUIFER STORAGE RECOVERY1

ABSTRACT: The biodegradation potential of two drinking water disinfection byproducts was investigated using aquifer materials obtained from approximately 100 and 200 meters below land surface in an aerobic aquifer system undergoing aquifer storage recovery of treated surface water. No significant biodegradation of a model trihalomethane compound, chloroform, was observed in aquifer microcosms under aerobic or anaerobic conditions. In contrast, between 16 and 27 percent mineralization of a radiolabeled model haloacetic acid compound, chloroacetic acid, was observed. These results indicate that although the potential for biodegradation of chloroacetic acid exists in deep aquifer systems, chloroform entrained within these aquifers or formed in situ will tend to persist. These results have important implications for water managers planning to meet anticipated lowered permissible levels of trihalomethanes in drinking water.     

Impact of 20 Years of Land-Cover Change on the Hydrology of Streams in the Southeastern United States1

Cruise, James F., Charles A. Laymon, and Osama Z. Al-Hamdan, 2010. Impact of 20 Years of Land-Cover Change on the Hydrology of Streams in the Southeastern United States. Journal of the American Water Resources Association (JAWRA) 46(6):1159–1170. DOI: 10.1111/j.1752-1688.2010.00483.x Abstract: Land-cover changes for portions of Alabama, Georgia, and Tennessee were estimated for the years 1980, 1990, and 2000 using classified Landsat images, and associated with hydrologic indices for 12 watersheds in the region. Rainfall-adjusted mean annual streamflow, an ET proxy (precipitation minus runoff), frequency of inundation above thresholds, and duration of inundation were used to characterize the hydrologic response of the test basins over the two-decade study period. Results indicate that several of the watersheds had undergone significant (>20%) reductions in agricultural land cover with a coincident increase in forested land. Attempts to correlate the hydrologic results with the land-cover changes were only partially successful. Watersheds with the largest land conversion from agriculture to forest (20% or more) did show significant trends in hydrologic indices indicating decreasing streamflow; however, other basins evidenced ambiguous results. The net conclusions of the study are that land-cover effects on hydrologic variables may be nuanced and can sometimes be only indirectly evident, and that a rigorous and detailed land-cover classification effort along with a battery of statistical tests with the same objective may be necessary to uncover these effects.