Precipitation as the Primary Driver of Variability in River Nitrogen Loads in the Midwest United States

Nitrogen (N) losses from agricultural lands in the Midwest United States are contributing to the expansion of the hypoxic zone in the Gulf of Mexico. This study evaluated the importance of inter‐annual variability in precipitation, land cover, and N fertilizer use on NO₃ + NO₂‐N loads in seven United States Midwestern Rivers using the backward stepwise regression analysis. At the annual scale, fluctuations in the current and previous years’ precipitations explained much of the variation in streamflow, baseflow, and N‐load. Previous years precipitation effects were associated with fillable soil porosity. In some years, higher residual soil N from previous dry years also contributed to an increase in N‐load. Area under soybean production (SOY), a surrogate for replacement of prairies and small grains was generally not a significant explanatory variable. Fertilizer use from 1987 to 2012 was also not a significant explanatory variable in the annual analysis. Precipitation in both the current and previous months and previous year were important in explaining variation in monthly streamflow, baseflow, and N‐load. SOY was significant in one or two months from June to August, but had a higher p‐value than precipitation. We conclude recent increases in river N‐loads are primarily due to wet climate and minimally due to the changes in land cover or N fertilizer use. Under current cropping systems and agronomic N application rates, tile water remediation will be necessary to reduce river N‐loads.     

Salt Flushing,Salt Storage,and Controls on Selenium and Uranium: A 31‐Year Mass‐Balance Analysis of an Irrigated,Semiarid Valley

Salinity, selenium, and uranium pose water‐quality challenges for the Arkansas River in southeastern Colorado and other rivers that support irrigation in semiarid regions. This study used 31 years of continuous discharge and specific conductance (SC) monitoring data to assess interannual patterns in water quality using mass balance on a 120‐km reach of river. Discrete sampling data were used to link the SC records to salinity, selenium, and uranium. Several important patterns emerged. Consumptive use reduced discharge by a median value of 33% and drove corresponding increases in salinity and uranium concentrations. Increased water availability for irrigation from rainfall and upstream snowpack in 1995–1999 flushed additional salinity and uranium into the river in 1996–2000; average annual total dissolved solids (salinity) concentrations increased 25%, and loads increased 131%. Smaller flushing events have occurred, sometimes lagging an increase in water availability by about one year. The pattern indicates flushing of salts temporarily stored, evaporatively concentrated, or of geologic origin. Mobilization of selenium from the reach was minor compared to salinity and uranium, and net selenium removal from the river was suggested in some years. Several processes related to irrigation could be removing selenium. The results provide context for efforts to improve water quality in the Arkansas River and rivers in other semiarid regions.     

丰水期乌江上游干流水库—河流体系硫同位素组成

2007年7月对乌江上游河流、乌江干流上的3座不同库龄的梯级水库(洪家渡水库、东风水库、乌江渡水库)表层及垂直剖面水体的可溶性硫酸盐的硫同位素组成进行了研究.在垂直剖面上,洪家渡水库硫同位素值(δ34S)介于+0.3‰～+3.1‰,下泄水为-0.7‰;东风水库δ34S值介于-7.5‰～-5.5‰,下泄水为-6.8‰;乌江渡水库δ34S值介于-4.3‰～-0.6‰,下泄水为-2.9‰.上述结论表明,硫同位素组成变化反映了水库硫的不同来源及生物地球化学过程.不同水库表层和垂直剖面水体的硫同位素平均值有差别,水库表层的硫同位素比值主要受输入水体的控制,垂直剖面由表层向下硫同位素比值偏负,主要是由于生物作用以及有机硫的氧化造成的.     

水体污染物为导向的流域环境审计模式

日益严峻的环境问题表明,环境行政部门的单一管理模式已难以适应环境监管的需要,独立的第三方监督已成为必要.环境审计实务中多采用以项目为导向,以资金审计为重点的审计模式,难以适应逐步向绩效审计发展的环境审计的需要.本文分析了水体污染区域性、复杂性和累积性等特点,将其与审计理论相结合,构建了以流域主要污染物或特征污染物为导向的审计模式,探讨了以水体污染物迁移特点为基础的流域环境审计范围和重点区域的划分方法,建立了专家评价法、文献调查法、实地监测法等导向污染物调查方法,根据水体污染累积性的特点,从环境治理项目、生态恢复效果等层次确立了审计对象,按政策制度、项目管理、专业技术等层面确定了审计内容,给出了周期性审计、周期内跟踪审计等适合水体环境审计要求的审计方式,并结合太湖流域进行了较为系统的分析,为水环境审计的深入开展提供一定的指导.     

Ion activity and distribution of heavy metals in acid mine drainage polluted subtropical soils

The oxidative dissolution of mine wastes gives rise to acidic, metal-enriched mine drainage (AMD) and has typically posed an additional risk to the environment. The poly-metallic mine Dabaoshan in South China is an excellent test site to understand the processes affecting the surrounding polluted agricultural fields. Our objectives were firstly to investigate metal ion activity in soil solution, distribution in solid constituents, and spatial distribution in samples, secondly to determine dominant environment factors controlling metal activity in the long-term AMD-polluted subtropical soils. Soil Column Donnan Membrane Technology (SC-DMT) combined with sequential extraction shows that unusually large proportion of the metal ions are present as free ion in the soil solutions. The narrow range of low pH values prevents any pH effects during the binding onto oxides or organic matter. The differences in speciation of the soil solutions may explain the different soil degradation observed between paddy and non-paddy soils.     

Situational Waste in Landscape Watering: Residential and Business Water Use in an Urban Utah Community1

Abstract: Landscape water conservation is an important issue for municipalities throughout the Western United States, and especially in Utah as rapid growth strains existing water supplies. We conducted interdisciplinary research in Layton, Utah, that aimed at understanding patterns of landscape water use among households and businesses. The research project involved three basic tasks. First, a landscape “water budget” was developed by producing a calibrated and classified mosaic of landscape type and area from airborne multispectral digital imagery, integrating this information with Layton City parcel boundary data to determine landscape vegetated areas per lot, and estimating irrigation needs derived from reference evapotranspiration (ETo) obtained using weather data for the Salt Lake City metropolitan region. Second, utilizing Layton water billing data, water use for each household and business was identified and categorized as “conserving,”“acceptable” or “wasteful” by determining how much the water applied varied from actual landscape plant need. Third, surveys were administered to a random stratified sample of households and businesses in the study area to investigate various factors that were hypothesized to be predictive of wasteful watering practices. This paper primarily focuses on analysis of the household and business survey data, which explores factors affecting urban landscape water use from a human behavioral perspective. We found that the most significant factors predicting actual water use were the type of irrigation system and whether the location was a household or business. Attitudinal and motivational characteristics were not consistently associated with water use. We found that wasteful watering is the result of many factors embedded in the complex context of urban landscapes. This implies that water conservation programs should identify potential wasteful users through analyses of water billing data and direct water conservation measures at these users by focusing on site‐specific evaluations and recommendations. Water audits or water checks are one such tool that some communities have employed to help people understand and assess the quantity of water needed by and applied to their landscapes. This approach provides an opportunity to evaluate situational constraints at particular locations and design appropriate strategies for reducing water waste.     

N2O emissions from municipal solid waste landfills with selected infertile cover soils and leachate subsurface irrigation

This study presents the field investigations into the effects of cover soils and leachate subsurface irrigation on N₂O emissions from municipal solid waste landfills. Landfill Site A and Site B, covered with carefully chosen infertile soils, were selected to monitor their diurnal and seasonal variations of N₂O emissions. The annual average N₂O flux was 469 ± 796 μg N₂O-N m⁻² h⁻¹ in Site B with leachate subsurface irrigation, three times that of Site A without leachate irrigation. When an additional soil containing lower contents of carbon and nitrogen was introduced to cover part of Site B, its N₂O fluxes decreased by 1-2 orders of magnitude compared with the left area of Site B. This suggested that carefully selected cover soils could substantially reduce N₂O emissions even under leachate subsurface irrigation. Statistical analysis proved that the availabilities of soil moisture and mineralized nitrogen were the key parameters controlling landfill N₂O emissions.     

填埋场渗滤液灌溉对粘壤土N2O释放的影响

以生活垃圾填埋场渗滤液和粘壤土为实验材料,研究了不同的渗滤液灌溉量、灌溉后土壤中矿物氮含量和反硝化酶活性对粘壤土N2O释放的影响.结果表明:渗滤液灌溉可促进土壤中N2O的释放,投加渗滤液的土壤样品N2O的释放通量是投加(NH4)2SO4溶液的2-3倍.粘壤土含水率为25%并且保持氧含量的条件下,渗滤液灌溉土壤后,土壤中N2O主要在硝化过程中产生.相关性统计分析表明:N2O释放通量与NO-2和渗滤液灌溉量呈显著正相关(分别为r=0.928,p＜0.001;r=0.425,P<0.05),而与土壤中NO-3和反硝化酶活性无显著相关性.     

Monitoring Inter-Annual Variability Reveals Sources of Mercury Contamination in Clear Lake, California

Mercury (Hg) in the aquatic ecosystem of Clear Lake has been documented since the 1970s when fishes were found to have elevated levels of toxic methyl mercury (meHg). Mining practices at the Sulphur Bank Mercury Mine (active intermittently from 1872–1957) along the shoreline of Clear Lake included the bulldozing of waste rock and overburden ore into the shallow nearshore regions of the lake and the creation of steeply sloped piles of waste rock at the water's edge. This process, plus erosion of the waste rock piles, resulted in the accumulation of an estimated 100 metric tons of Hg in Clear Lake. A monitoring program to assess Hg in Clear Lake was established in 1992, and conducted continuously from 1994. Drought conditions in California had persisted for ca. 6 yrs prior to 1992, when the U.S. Environmental Protection Agency (USEPA) remediated the steeply sloped eroding waste rock piles, which appeared to reduce sediment Hg concentrations significantly. In April 1995, a white flocculent material was observed in Clear Lake adjacent to the mine and has been observed every year since, leading to the discovery of ongoing acid mine drainage (AMD), low pH fluids high in Hg and extremely high in sulfate. AMD is now believed to be the most likely cause of elevated meHg in Clear Lake. The discovery of this source of meHg production in Clear Lake, which will significantly influence remedial options, was only made possible by implementation of a diligent monitoring program.     

新疆石化企业废水贮用现状及存在的问题

为掌握新疆石化企业的废水贮用现状,对新疆几个石化企业废水蓄水库运营状况及排水灌溉利用方式进行了调查分析。提出了石化企业废水冬贮及灌溉利用系统的未来管理重点和改进方向。并提出,解决新疆未来石化类工业园区排水出路问题时应注重技术进步,倡导循环经济和生态工业园区模式,因地制宜确定排水方案,应积极推进排水受纳区环境保护与资源化利用相结合的石化企业排水模式。