2011年春季日本福岛核泄漏污染输送:贵阳131I和137Cs观测示踪分析

2011年3月11日,日本本州9.0级地震引发了福岛核电站核泄漏,以及由此引起的131I和137Cs在全球大气环流传输已引起了重视.理论上也对这种输送路径进行了研究.本文报道2011年3月17日—4月28日在贵阳观风山对气溶胶中天然核素(210Pb、7Be)和人为核素(131I、137Cs)近地面空气浓度逐周采样的系统对比观测,并结合该时段贵阳离地面500m高度逐周315h的气团后向轨迹分析.结果表明:福岛核泄漏污染物通过两条显著的途径输送到贵阳地区.第一条是首波核污染通过全球大气环流传输,由西向东,几乎环绕地球一周,历经约10d至两周,最终在3月24日—31日从我国的西北地区入侵抵至贵阳;第二条途径则是福岛地区上空的核污染气团受东北天气系统的挤压南移并在低纬度地区再次先后受到东北和东南气流的影响,于4月7日—14日抵达贵阳.核污染的第一条输送路径是全球尺度,第二条是东亚区域尺度.     

生物对137Cs的吸收和富集

螺蛳等供试生物能很快地吸收水体中的＾１３７Ｃｓ,并随着时间的延长而不断增加,吸收过程可用直线方程来表达,螺蛳、喜旱莲子草和金鱼藻可以用来净化被＾１３７Ｃｓ的吸收较少,其中稗草和喜旱莲子草较高;由于Ｋ＾＋与Ｃｓ＾＋之间的拮抗作用,帮可用施钾肥方法减少作物以土壤中＾１３７Ｃｓ的吸收。     

A COMPARISON OF THREE METHODS FOR MEASURING RECENT RATES OF SEDIMENT ACCUMULATION1

ABSTRACT: The determination of sediment accumulation rates is important in understanding how these materials are affecting lakes and reservoirs ecosystems. In this study three methods were used to estimate sediment accumulation rates in the impounded backwater lakes behind Lock and Dam Nos. 8 and 9 on the upper Mississippi River. The three methods were: 1) a “spud” survey, 2) a survey of bottom contours, and 3) the use of fallout cesium-137. The field use of these three methods of determining sediment accumulation and the potential errors and merits involved in each method are discussed. The results from the field study in backwater areas along the upper Mississippi River showed the survey of bottom contour method gave the lowest rate of sediment deposition and the ¹³⁷Cs method gave the highest rates. Sediment accumulation rates from 0 to 7.8 cm per year were measured in the study area. All three methods are useful and have unique characteristics for determining rates and patterns of sediment accumulation. Thus the choice of a method to be used in a sediment survey is dependent on the type of information needed and the time available.     

Partitioning of Cs-137 Between Sediment and Water From the Black Sea

Abstract

As part of a joint USA/USSR Environmental Agreement to determine the distribution and concentration of Chernobyl radioactivity in the northwest Black Sea area, the sediment from eight stations was collected and analyzed to assess the ability of this material to adsorb radiocaesium. Batch tests were conducted in which Cs-137 tracer was added to mixtures of sediment and bottom water, with contact solutions ranging from 85 Bq ml^?1 to 1,760 Bq ml^?1. This work was done in an argon atmosphere at 9.5°C, which is the average temperature of the sediment. Isotherms were linear for all cores and distribution ratios (R_D) calculated from the slopes of the isotherms ranged from 660 to 1,660 ml g^?1. These isotherms fit a simplified Freundlich isotherm. Correlations of R_D to a number of sediment parameters describing texture and mineralogy were determined. A close relationship was observed between R_D for caesium and the percentage of illite contained in the samples.     

Investigations of Contaminated Fluvial Sediment Deposits: Merging of Statistical and Geomorphic Approaches

Concentrations of contaminants in sediment deposits can have large spatial variability resulting from geomorphic processes acting over long time periods. Thus, systematic (e.g., regularly spaced sample locations) or random sampling approaches might be inefficient and/or lead to highly biased results. We demonstrate the bias associated with systematic sampling and compare these results to those achieved by methods that merge a geomorphic approach to evaluating the physical system and stratified random sampling concepts. By combining these approaches, we achieve a more efficient and less biased characterization of sediment contamination in fluvial systems. These methods are applied using a phased sampling approach to characterize radiological contamination in sediment deposits in two semiarid canyons that have received historical releases from the Los Alamos National Laboratory. Uncertainty in contaminant inventory was used as a metric to evaluate the adequacy of sampling during these phased investigations. Simple, one-dimensional Monte Carlo simulations were used to estimate uncertainty in contaminant inventory. We also show how one can use stratified random sampling theory to help estimate uncertainty in mean contaminant concentrations.     

REELFOOT LAKE SEDIMENTATION RATES AND SOURCES1

ABSTRACT: The three basins of Reelfoot Lake, which is located in northwestern Tennessee, were investigated using the Cs-137 tracer technique to determine rates of sediment deposition and to estimate the time before the basins will fill with sediment. Blue Basin, the largest of the three basins with 2922 ha, had an average annual sedimentation rate of 0.9 cm/yr from 1984 to 1984. The basin will become too shallow for most boating and recreational activities in about 200 years. Buck Basin, the central basin with 774 ha, had an average annual sedimentation rate of 1.1 cm/yr and will become too shallow for most recreational uses in about 100 years. Upper Blue Basin, the most upstream and smallest basin with 439 ha, had an average annual sedimentation rate of 1.7 cm/yr and will become too shallow for most recreational uses in about 60 years. Two important sources of sediment to Reelfoot Lake are erosion from a large number of soybean fields and channelization of many of the streams that flow into the lake. Changes in land management that would reduce erosion could increase the time the lake would remain usable for recreational activities.     

Preliminary Caesium Data From A Cooperative Us/Ussr Monitoring Survey for Chernobyl Radioactivity in the Black Sea

In June 1990, scientists from the US Environmental Protection Agency's (EPA) Office of Radiation Programs (ORP), and the Woods Hole Oceanographic Institution (WHOI), travelled to Sevastopol in the Soviet Union to work with radioecologists and marine scientists from the USSR Institute of Biology of the Southern Seas (IBSS). the purpose of this cooperative programme was to conduct a monitoring survey for radioactivity in the northwestern Black Sea. Samples of sediment, surface and in-situ water, and biota were collected from fourteen stations for post-survey radionuclide analyses to determine levels of radioactivity in the Black Sea environment resulting from the Chernobyl nuclear power plant explosion and subsequent transport of radioactivity via the Dnepr and Danube rivers. This paper presents the preliminary data for caesium-137 and caesium-134 in sediment samples analyzed by the EPA/ORP. Caesium-137 was measured at four shallow (20-114 m) stations on the shelf near the mouth of the Dnepr and Danube Rivers, but was not detected in sediments from comparable depths at stations further off shore or in slope sediments at depths of 510-1288 meters. Caesium-134 was detected only in sediments from the shallow-water station nearest to the Danube River.     

Cs-137 contamination in forest ecosystems in southwest Rila Mountain, Bulgaria

We studied Cs-137 contamination and radionuclide transfer in mountain forest ecosystems from Bulgaria. Here we show the first analyses of Cs-137 soil-to-plant transfer and we assess that it depends on the soil organic matter content and the specifics of the tree species. The forest litter is strong polluted with Cs-137 and is a barrier for its migration. In the upper 0-5 cm of the soil the Cs content ranges from 52 to 81 Bq kg^–1 then decreases in deeper layers. The 1-year-old needles of spruce, fir, and Scots pine accumulate more cesium than the fine roots. The values of the needles transfer factor range between 0.3 and 0.58. The fine roots transfer factor varies between 0.1 and 0.32.     

Nutrient fluxes in a eutrophic coastal Louisiana freshwater lake

Nitrogen and phosphorus cycling in a eutrophic Louisiana freshwater lake system (Lac des Allemands) was studied. Nutrients from runoff entering the lake, as well as sediment-interstitial and lake water nitrogen and phosphorus fractions, were measured seasonally. Sedimentation rates in the lake were determined using¹³⁷Cs dating.Phosphorus levels in the lake were found to be largely dependent on concentrations in the incoming bayou water from upland drainage. Lake water concentrations appear to respond to fluctuations in incoming waters. Laboratory equilibrium studies showed bottom sediments in the lake are a major sink for the incoming dissolved orthophosphate phosphorus. Total nitrogen concentrations in the lake water generally exceeded incoming runoff concentrations, suggesting fixation by the large blue-green algae population in the lake as being the major source of nitrogen to the system.Sedimentation ranged from 0.44 cm/year to 0.81 cm/year, depending on the proximity to the inlet bayous. Even though the lake is eutrophic the sediment served as a buffer by removing large amounts of carbon, nitrogen, and phosphorus through sedimentation processes. Carbon, nitrogen, and phosphorus were accumulating in the sediment at rates of 60, 7.1, and 1.1 g/m²/year, respectively.The water quality of the lake is likely to continue to decline unless measures are taken to reduce municipal, industrial, and agricultural inputs of phosphorus into the lake.     

Analysis of Factors Determining Accumulation of 137Cs by Woody Plants

The accumulation of ¹³⁷Cs by coniferous (Pinus sylvestris) and deciduous (Betula pendula) trees was studied in the area contaminated with radioactive products after the Chernobyl accident. The availability of ¹³⁷Cs to woody plants is determined by its vertical distribution in the soil profile, the proportion of its exchangeable form, and the distribution of tree roots in the soil. The index of biological availability of ¹³⁷C in the soil is proposed, and its linear dependence on the coefficients of ¹³⁷Cs transfer to wood is demonstrated.