北京市区及郊区大气中的汞沉降的估算

以Throughfall法估算出北京市1996年大气汞干沉降率为528．88μg.m^2.a^-1，以沉降速率估算出1998年北京市汞的年沉降量为687．5μg.m^-2.a^-1。     

The lead content and isotopic composition of british coals and their implications for past and present releases of lead to the UK environment

More than 60 coal samples, predominantly from the principal coalfields of England and Wales (25) and Scotland (30), were analysed for lead by AAS and for stable lead isotopes by ICPMS. While the average lead content of Scottish coal, 23.9mg kg^–1, was more than double that of coal from England and Wales, 11.0mg kg^–1, the corresponding mean ²⁰⁶Pb/²⁰⁷Pb ratios (± 1 s.d.) were nearly identical, at 1.181±0.011 and 1.184±0.006, respectively. In the light of the lead isotopic signatures of British coals and of both indigenous (²⁰⁶Pb/²⁰⁷Pb 1.17) and imported Australian (²⁰⁶Pb/²⁰⁷Pb 1.04) lead ores, an approach based on estimated lead emissions from these sources and the deconvolution of the historical lead and ²⁰⁶Pb/²⁰⁷Pb records preserved in lake sediments, peat bogs and archival herbage material indicates that coal combustion became an increasingly significant contributor to atmospheric lead deposition in the UK during the period 1830–1930, especially after the onset of Englands decline as a major location of lead mining and smelting in the late19th Century. Since 1930 and the introduction of leaded petrol, the atmospheric ²⁰⁶Pb/²⁰⁷Pb ratio in the UK has been strongly influenced by carexhaust emissions of comparatively ²⁰⁶Pbdepleted lead of predominantly Australian origin, counterbalanced to some extent by coalcombustion emissions of lead, although these have fallen dramatically since the mid1950s. Nevertheless, with the introduction and substantial uptake of unleaded petrol in the UK during the last decade, even the declining releases from coal, along with contributions from other sources, are continuing to affect the atmospheric lead content and ²⁰⁶Pb/²⁰⁷Pb ratio.     

Changes in nutrient content and stable isotope ratios of C and N during decomposition of seagrasses and mangrove leaves along a nutrient availability gradient in Florida Bay, USA

The decomposition of the mangrove Rhizophora mangle and the seagrass Thalassia testudinum was examined using litterbags along a natural gradient in nutrient availability. Seagrass leaves had a higher fraction of their biomass in the labile pool (57%), compared to mangrove leaves (36%) and seagrass rhizomes (29%); the overall decomposition rates of the starting material reflected the fractionation into labile and refractory components. There was no relationship between the N or P content of the starting material and the decomposition rate.

Nutrient availability had no influence on decomposition rate, and mass was lost at the same rate from litterbags that were buried in the sediment and litterbags that were left on the sediment surface. The dynamics of N and P content during decomposition varied as a function of starting material and burial state. N content of decomposing mangrove leaves increased, but seagrass rhizomes decreased in N content during decomposition while there was no change in seagrass leaf N content. These same general patterns held for P content, but buried seagrass leaves increased in P content while surficial leaves decreased. δ¹³C and δ¹⁵N changed by as much as 2‰ during decomposition.     

Use of Central Stonerollers (Cyprinidae: Campostoma anomalum) from Tennessee as a Bioindicator of Metal Contamination

We compared the levels of arsenic, cadmium, chromium, lead, manganese, mercury and selenium in a small species of fish (Central stonerollers, Campostoma anomalum) collected from East Fork Poplar Creek (EFPC) and a reference site in eastern Tennessee. Stonerollers are minnows in the Cyprinidae family that serve as prey for many carnivores in aquatic systems. Fish were collected from East Fork Poplar Creek within the U.S. Department of Energy's Y-12 National Security Complex, part of the Oak Ridge Reservation, and from a reference stretch of the Little River in East Tennessee. Whole fish were homogenized for analysis. Concentrations of all metals (except arsenic) were significantly higher in stonerollers from EFPC compared to the reference site. Mercury levels in minnows from EFPC averaged 0.4 ppm (μg/g), four times higher than the average for fish in the U.S. in general. This was higher than levels in fish from the nearby Clinch River and higher than fillets of white bass (Morone chrysops) from the same creek. Most metal levels were inversely related to size and weight of the stonerollers, perhaps due to growth dilution.     

PRESERVATION OF SAMPLES FOR DISSOLVED MERCURY1

ABSTRACT: Water samples for dissolved mercury require special treatment because of the high chemical mobility and volatility of this element. Widespread use of mercury and its compounds has provided many avenues for contamination of water. Two laboratory tests were done to determine the relative permeabilities of glass and plastic sample bottles to mercury vapor. Plastic containers were confirmed to be quite permeable to airborne mercury, glass containers were virtually impermeable. Methods of preservation include the use of various combinations of acids, oxidants, and complexing agents. The combination of nitric acid and potassium dichromate successfully preserved mercury in a large variety of concentrations and dissolved forms. Because this acid-oxidant preservative acts as a sink for airborne mercury and plastic containers are permeable to mercury vapor, glass bottles are preferred for sample collection. To maintain a healthy work environment and minimize the potential for contamination of water samples, mercury and its compounds are isolated from the atmosphere while in storage. Concurrently, a program to monitor environmental levels of mercury vapor in areas of potential contamination is needed to define the extent of mercury contamination and to assess the effectiveness of mercury clean-up procedures.     

痕量汞的分析现状

本文系统地综述了自1975年以来分光光度法、催化法、电极溶出伏安法、冷原子吸收和荧光法以及其它方法分析痕量汞的发展状况,并对稀浓度汞标液的保存方法作了介绍。     

Anthropogenic mercury emissions in China

An inventory of mercury emissions from anthropogenic activities in China is compiled for the year 1999 from official statistical data. We estimate that China's emissions were 536 (±236) t of total mercury. This value includes open biomass burning, but does not include natural sources or re-emission of previously deposited mercury. Approximately 45% of the Hg comes from non-ferrous metals smelting, 38% from coal combustion, and 17% from miscellaneous activities, of which battery and fluorescent lamp production and cement production are the largest. Emissions are heaviest in Liaoning and Guangdong Provinces, where extensive smelting occurs, and in Guizhou Province, where there is much small-scale combustion of high-Hg coal without emission control devices. Emissions are gridded at 30×30 min spatial resolution. We estimate that 56% of the Hg in China is released as Hg⁰, 32% as Hg²⁺, and 12% as Hg^p. Particulate mercury emissions are high in China due to heavy burning of coal in residential and small industrial settings without PM controls. Emissions of Hg²⁺ from coal-fired power plants are high due to the absence of flue-gas desulfurization units, which tend to dissolve the soluble divalent mercury. Metals smelting operations favor the production of elemental mercury. Much of the Hg is released from small-scale activities in rather remote areas, and therefore the activity levels are quite uncertain. Also, emissions test data for Chinese sources are lacking, causing uncertainties in Hg emission factors and removal efficiencies. Overall, we calculate an uncertainty level of ±44% (95% confidence interval) in the estimate of total emissions. We recommend field testing of coal combustors and smelters in China to improve the accuracy of these estimates.     

A Simple Field Method to Determine Mercury Volatilization from Soils (3 pp)

Background Estimations of gaseous mercury volatilization from soils are often complex, stationary and expensive. Our objective was to develop a mobile and more simple, easy to handle and more cost-effective field method allowing rapid estimates of potential Hg emissions from soils. Methods. The study site is located in Germany, about 100 kilometers south-westerly of Berlin and influenced by the river Elbe and its tributary Saale river. The site is representative for a lot of other floodplain locations at the river Elbe and highly polluted with Hg and other heavy metals. For our study we developed a system consisting of a glass chamber gas, two gold traps, a battery operated pump and a gas meter. Adsorbed total gaseous mercury (TGM) in the gold traps was determined by use of atomic absorption spectrometry (AAS). Results and Discussion. In contrast to the common used flux chambers we designed a chamber without inlet and named it gas suck up chamber (GSC). TGM fluxes determined with the GSC showed a very close linear correlation (r = 0.993) between the TGM content in the gold traps and the corresponding pumped gas volume. The TGM adsorbed, increased proportional with increasing gas volume indicating homogenous concentrations of gaseous mercury in the soil air sucked. In contrast to the commonly used dynamic flux chamber with the aim of precisely measuring actual fluxes of Hg from a defined soil area, we focused on developing of a measurement system which will allow rapid estimates of potential Hg emissions of a site. Earlier research at the study site indicated a high potential for releasing volatile Hg from the soil to the atmosphere. Indeed, due to the high Hg content of the soil significant amounts of TGM could be detected and no shortage was reached. Conclusion. Our initial measurements are still too few in number neither to generalize the achieved results nor discuss controlling factors and processes. However, we are pleased to communicate that the developed GSC is well suited to become an effective sampling set up to rapidly estimate the magnitude of Hg volatilization from soils. Outlook. Further measurements at other polluted locations are necessary to verify the GSC method. In addition the use of a mercury analyzer instead of gold traps is planned for faster risk assessments.     

燃煤烟气中汞形态分析的实验研究

在一维煤粉燃烧炉台架上采用EPA推荐的Ontario Hydro方法 ,测量了燃烧不同煤种排放的烟气中汞的形态分布情况 .结果表明 ,烟气中汞以颗粒态和气态汞的形式存在 .气态汞总量在 9— 2 3 μg·Nm- 3范围内 ,主要以单质汞的形式存在 ,占气态汞总量的 5 2 %—83 % ,而二价汞占 1 7%— 48% .飞灰中汞的浓度大大超过了底灰中汞的浓度 ,表明汞在飞灰中富集 ,在底灰中分散的行为