我国近地层臭氧污染对水稻和冬小麦产量的影响概述

地表监测数据表明,我国近地层O3污染日趋严重,已对水稻和冬小麦的生长造成严重威胁。为评估O3污染对我国农业生产的风险,综合已有剂量反应实验结果,对我国南北五个地区(北京、定兴、江都、嘉兴、东莞)水稻和冬小麦的O3敏感性进行了比较分析。研究发现:(1)随着实验地区和实验品种的变化,两种作物的O3敏感性存在明显差异,其中,水稻对O3的敏感程度由北到南逐渐增加;(2)两种作物的产量均随O3剂量的增加而降低,且冬小麦的减产程度高于水稻;(3)基于FACE实验得到的作物O3敏感性高于基于OTC实验的研究结果。利用上述研究得到的O3剂量反应方程和O3浓度预测数据,对未来我国水稻和冬小麦的产量损失进行了评估。预计到2020年,我国五个主要作物产地水稻和冬小麦的产量损失范围分别为3.2~28.8%和7.8~36.9%。上述结果表明,O3污染已对我国主要粮食作物的生长造成巨大威胁,且作物品种间存在明显的O3抗性差异,有必要采取有效措施缓解O3浓度的上升,同时,需要利用更科学的实验方法进行O3抗性品种的选育,这对降低O3的农业风险具有重要意义。     

玛瑙河多环境介质和铜锈环棱螺体内微塑料的赋存特征

微塑料污染对水生态系统及人类健康危害大,为探究微塑料在不同环境介质中的赋存特征,选择长江一级支流玛瑙河为研究区域,通过现场采样、显微镜观察和傅里叶红外光谱测定等,对玛瑙河表层水体、沉积物、河岸带土壤和底栖动物铜锈环棱螺中微塑料的丰度、粒径、形状、颜色和组成类型进行了分析.结果表明,玛瑙河表层水体的微塑料平均丰度为（5.9±0.26）n·L^-1;上层沉积物中微塑料丰度（以干重计）为（1.35±0.1）n·g^-1,下层沉积物中微塑料丰度（以干重计）为（0.93±0.12）n·g^-1;近河岸带土壤中微塑料丰度（以干重计）为（0.68±0.16）n·g^-1,远河岸带土壤中微塑料丰度（以干重计）为（0.69±0.14）n·g^-1;铜锈环棱螺体内微塑料丰度为（2.06±0.25）n·g^-1.分析发现,上层沉积物和下层沉积物中微塑料丰度呈正相关;铜锈环棱螺体内微塑料丰度分别与上、下层沉积物中微塑料丰度呈正相关;近、远河岸带土壤中微塑料丰度具有相关性.各环境介质和铜锈环棱螺体内微塑料粒径大多<0.1mm,主要形态为纤维状和碎片状,颜色以蓝色和黑色为主,成分主要是聚丙烯（PP）和聚乙烯（PE）.研究发现,河岸带土壤中微塑料主要来源于农用塑料薄膜的破碎和分解.通过多环境介质调查和铜锈环棱螺体内微塑料的分析,探明了大型底栖动物体内微塑料的累积效应,可为全面了解微塑料潜在生态风险提供依据.     

银川市典型湖泊沉积物细菌群落结构及其对重金属的响应关系

湖泊湿地是极其重要而又特殊的生态系统,在区域水资源调蓄、环境保护和生物多样性维持等方面具有重要意义.沉积物细菌是湖泊生态系统重要的组成部分,是湖泊生物地球化学循环的主要驱动力.为探明银川市典型湖泊沉积物细菌的群落结构及其影响因素,选取银川市3个典型湖泊（阅海湖、鸣翠湖和犀牛湖）为研究对象,于2021年1月、4月、7月和10月采集表层沉积物,应用16S rDNA高通量测序技术研究沉积物细菌群落组成,并探究其与重金属之间的响应关系.结果表明,银川市3个典型湖泊沉积物重金属生态危害系数远小于40,生态危害指数远小于150,危害程度均为生态轻微危害.3个湖泊的细菌群落多样性无显著差异,但各湖泊不同季节多样性有显著变化,群落组成也存在显著差异.阅海湖、鸣翠湖和犀牛湖的优势种菌门（相对丰度排名前3）均为：变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）和绿弯菌门（Chloroflexi）,优势下级阶元为γ-变形菌纲（Gammaproteobacteria）、α-变形菌纲（Alphaproteobacteria）和δ-变形菌纲（Deltaproteobacteria）.银川市典型湖泊门水平分类上出现的主要差异物种为变形菌门（Proteobacteria）、拟杆菌门（Bacteroidetes）、广古菌门（Euryarchaeota）、厚壁菌门（Firmicutes）、放线菌门（Actinobacteria）和酸杆菌门（Acidobacteria）.阅海湖沉积物细菌群落结构与Cu、Fe、Mn、Zn、As和Pb显著相关,鸣翠湖沉积物细菌群落结构与Fe、Pb和Cr显著相关,犀牛湖沉积物细菌群落结构与重金属相关关系不显著.沉积物重金属的种类和含量对银川市阅海湖和鸣翠湖沉积物细菌群落结构有显著影响,是引起湖泊沉积物细菌群落结构变化的重要环境因子.     

EVALUATION OF SOME APPROACHES TO ESTIMATING NON-POINT POLLUTANT LOADS FOR UNMONITORED AREAS1

ABSTRACT: Evaluation of the non-point source pollutant load entering a lake from multiple tributaries requires either that all tributaries be monitored or that some extrapolation method be used to estimate loads originating in areas not monitored. Unmonitored areas include not only watersheds of tributaries that are not monitored, but also portions of a monitored tributary's drainage basin downstream from the monitoring site and areas of direct drainage. Significant portions of large lake drainage basins are often not monitored, and loads for these areas are often estimated by extrapolation. Six simple extrapolation procedures were evaluated by using them to estimate loads for areas that had been monitored and comparing the estimated loads with the monitored loads. Three approaches were based on inter-basin ratios of area, C-factor, and discharge. The other approaches used regression relationships between concentration and flow to estimate concentrations for the unmonitored basin. The ratio approaches generally were more reliable than the regression approaches. However, extrapolation by any method tested was not very precise. Some methods also were biased when applied to watersheds of a size different than the monitored one. Extrapolation by any of these methods would compromise the precision of the lake-wide load estimate, if the unmonitored area were a significant part of the entire basin.     

COARSE WOODY DEBRIS AND CHANNEL MORPHOLOGY: A FLUME STUDY1

ABSTRACT: In recent years, logs and other structures have been added to streams for the purposes of altering channel morphology to improve fish habitat. This flume study was conducted to evaluate the effects of coarse woody debris on local channel morphology. Wooden dowels were used to simulate the effects of individual logs in a stream, and scour depth and surface area were determined at the end of each test run. The maximum scour depth was significantly correlated (90 percent confidence level) with both the vertical orientation of the dowels and the channel opening ratio; the scour surface area was significantly correlated (90 percent confidence level) with both the flow depth and the vertical orientation. Upstream-oriented dowels caused relatively large streambed scour and also deflected flows toward the streambank. Downstream-oriented dowels generally caused less bed scour and appeared to provide better bank protection because flow was generally deflected from the bank. In conjunction with data from field studies, these results provide information on the effects of orientation, hydraulic function, and relative stability of coarse woody debris in streams.     

Redox potential and uranium sorption onto sediments: kinetic and thermodynamic characteristics

ABSTRACT

The effects of the flooding and initial Eh of sediments on the sorption of uranium onto the sediments were analysed by flooding and static experiments. The changes in uranium species with Eh and kinetic and thermodynamic characteristics of the uranium sorption onto the sediments were investigated. The flooding experiment indicates that the initial Eh of the sediment gradually decreased with the increase in flooding time. Based on the redox potential in the flooding experiment, simulation results obtained using the geochemical simulation software PHREEQC show that the concentration of U (VI) decreased. In contrast, the concentrations of U (III), U (IV), and U (V) gradually increased. The pseudo-second-order kinetic model well fitted the experimental data, which shows that the sorption was mainly chemical sorption. The thermodynamic parameters suggest that the entropy and enthalpy under the used conditions were positive and that ΔG^θ was negative. A thermodynamic analysis shows that the sorption was endothermic and spontaneous. These results are useful for the understanding of the sorption mechanism and migration of uranium onto the sediment under different initial sediment redox potentials and provide a good theoretical foundation for radioactive pollution remediation.     

Pattern and Process in Northern Rocky Mountain Headwaters: Ecological Linkages in the Headwaters of the Crown of the Continent1

Abstract: The Crown of the Continent is one of the premiere ecosystems in North America containing Waterton‐Glacier International Peace Park, the Bob Marshall‐Great Bear‐Scapegoat Wilderness Complex in Montana, various Provincial Parks in British Columbia and Alberta, several national and state forest lands in the USA, and Crown Lands in Canada. The region is also the headwater source for three of the continent’s great rivers: Columbia, Missouri and Saskatchewan that flow to the Pacific, Atlantic and Arctic Oceans, respectively. Headwaters originate in high elevation alpine environs characterized by high snow accumulations in winter and rainstorms in summer. Most headwaters of the region contain high quality waters with few ions in solution and extremely low nutrient concentrations. Alpine streams have few species of aquatic organisms; however, they often possess rare species and have hydrogeomorphic features that make them vulnerable to climatic change. Subalpine and valley bottom streams of the Crown of the Continent Ecosystem (CCE) flow through well forested watersheds. Along the elevation gradient, the streams and rivers of the CCE flow through series of confining and nonconfining valleys resulting in distinct canyon and floodplain reaches. The alluvial floodplains are characterized by high species diversity and bioproduction maintained by the hydrologic linkages of habitats. The streams and rivers of the CCE have low nutrient concentrations, but may be significantly affected by wildfire, various resource extraction activities, such as logging or mining and exurban encroachment. Wildfire has been shown to increase nutrient loading in streams, both during a fire and then following the fire for as much as 5 years. Logging practices increase nutrient loading and the algal productivity of stream periphyton. Logging and associated roads are also known to increase sediment transport into Crown of the Continent streams directly affecting spawning success of native trout. The CCE is one of the fastest growing regions in the USA because of the many recreational amenities of the region. And, while the region has many remarkably pristine headwater streams and receiving rivers, there are many pending threats to water quality and quantity. One of the most urgent threats comes from the coal and gas fields in the northern part of the Crown of the Continent, where coal deposits are proposed for mountain‐top removal and open‐pit mining operations. This will have significant effects on the waters of the region, its native plants and animals and quality of life of the people.     

Adequacy of Visually Classified Particle Count Statistics From Regional Stream Habitat Surveys1

Abstract: Streamlined sampling procedures must be used to achieve a sufficient sample size with limited resources in studies undertaken to evaluate habitat status and potential management‐related habitat degradation at a regional scale. At the same time, these sampling procedures must achieve sufficient precision to answer science and policy‐relevant questions with an acceptable and statistically quantifiable level of uncertainty. In this paper, we examine precision and sources of error in streambed substrate characterization using data from the Environmental Monitoring and Assessment Program (EMAP) of the U.S. Environmental Protection Agency, which uses a modified “pebble count” method in which particle sizes are visually estimated rather than measured. While the coarse (2?) size classes used in EMAP have little effect on the precision of estimated geometric mean (D_gm) or median (D₅₀) particle diameter, variable classification bias among observers can contribute as much as 0.3?, or about 15‐20%, to the root‐mean‐square error (RMSE) of D_gm or D₅₀ estimates. D_gm and D₅₀ estimates based on EMAP data are nearly equal when fine sediments (<2 mm) are excluded, but otherwise can differ by up to a factor of 2 or more, with D_gm < D₅₀ for gravel‐bed streams. The RMSE of reach‐scale particle size estimates based on visually classified particle count data from EMAP surveys, including variability associated with reoccupying unmarked sample reaches during revisits, is up to five to seven times higher than that reported for traditional measured pebble counts by multiple observers at a plot scale. Nonetheless, a variance partitioning analysis shows that the ratio of among site to revisit variance for several EMAP substrate metrics exceeds 8 for many potential regions of interest, suggesting that the data have adequate precision to be useful in regional assessments of channel morphology, habitat quality, or ecological condition.     

Atmospheric Metal Pollutants-Archives, Methods, and History

Pollution of the atmosphere with cadmium (Cd), mercury (Hg), and lead (Pb) is a consequence of human activities. Natural archives are necessary to reconstruct the long-term history of metal deposition because accurate measurement of atmospheric deposition is a recent accomplishment. Reconstructions require: (1) accurate determination of concentrations of elements and isotopes, (2) accurate chronology of archives, and (3) archives that faithfully record atmosphere deposition. The most useful long-term archives are accumulations of ice and snow, peat, and lake sediment. Quantification of Cd deposition is uncommon because of its low concentration and substantial chemical mobility. Nonetheless, trends in peat and lake sediment are similar to those of Hg and Pb since ca. 1800 a.d. Both Hg and Pb are relatively chemically immobile and thus the peat and lake archives are believed to record historic trends of atmospheric deposition. Isotopic and concentration studies of Pb indicate a history of northern hemisphere atmospheric pollution extending back prior to 0 a.d. Although measurements of Hg concentration are now routine, isotopic measurements are in their infancy. Some Hg pollution sources have unique isotopic ratios, thereby contributing unique signals to the total Hg. Maximum accumulation rates of Hg and Pb occur up to 10 years later than for Cd (1970s versus 1960s in eastern North America, perhaps slightly later in Europe). By 2004, deposition of Cd, Hg, and Pb had declined from peak values in eastern North America more than 75, 75, and 90%, respectively.     

区域农业水分供应脆弱性分析及定量损失评估

采用积分湿度指数方法,建立了区域农业水分供应脆弱性分析模型,并以山东省为案例进行了应用研究,结果表明:无论春、夏、秋季还是年平均的积分湿度指数值,均呈从东南到西北递减的趋势,说明自然降水对农业需水的满足程度沿该方向递减。对山东省而言,农业用水的满足程度在季节上也存在较大的差异,夏季降水在农业满足程度方面最高、秋季次之、春季最差。由于气候因子的年变异较大,积分湿度指数的年变异亦大;根据作物产量的形成为一动态过程,作物整个生育期内的每一个生长阶段都对其最终产量有一定的贡献,利用积分回归模式对作物全生育期中每一旬降水因子与产量的定量关系进行模拟分析,得到了主要农作物全生育期内每旬降水对最终产量的贡献系数。根据每旬降水对产量的贡献系数和作物受旱指标,建立了作物旱灾损失评估模型。