Depositional behaviors of plutonium and thorium isotopes at Tsukuba and Mt. Haruna in Japan indicate the sources of atmospheric dust

Monthly plutonium and thorium depositions at Tsukuba (28 m asl) and Mt. Haruna (1370 m asl) were measured during 2006 and 2007 (Jan 2006-Dec 2007 at Tsukuba, Nov 2006-Dec 2007 at Mt. Haruna). The monthly ^239,240Pu depositions ranged from 0.044 to 2.67 mBq m⁻² at Tsukuba and from 0.05 to 0.9 mBq m⁻² at Mt. Haruna during the measurement periods. Monthly ^239,240Pu deposition did not differ markedly between the two sites except in April 2007. Seasonal pattern of monthly ^239,240Pu depositions at both sites showed high in spring and low in summer, and typical of seasonal variations in northeastern Asia. Thorium deposition at Tsukuba was higher than that at Mt. Haruna except in May and June 2007. ²³⁰Th/²³²Th activity ratios were used to partition deposition samples into locally and remotely derived fractions. The results revealed that a major proportion of total ^239,240Pu and Th deposits are derived from remote sources, especially in spring.     

Characteristics of lead geochemistry and the mobility of Pb isotopes in the system of pedogenic rock–pedosphere–irrigated riverwater–cereal–atmosphere from the Yangtze River delta region,China

Knowledge of the characteristics of Pb and its isotopic transfer in different compartments is scant, especially for the mobility of Pb isotopes in the geochemical cycle. The present study characterizes differential Pb transport mechanism and the mobility of Pb isotopes in the pedogenic parent rock–pedosphere–irrigated riverwater–cereal–atmosphere system in the Yangtze River delta region, by determining Pb concentration and Pb isotopic ratios of pedogenic parent rocks, fluvial suspended particle matter, tillage soils, soil profiles, irrigated riverwater, fertilizer, Pb ore, cereal roots and grains. The results show that Pb isotopes in the geochemical cycle generally follow the equation of ²⁰⁸Pb/²⁰⁶Pb = −1.157 × ²⁰⁶Pb/²⁰⁷Pb + 3.46 (r² = 0.941). However, Pb isotopes have different mobility in different environmental matrixes. Whereas in the pedosphere, the heavier Pb (²⁰⁸Pb) usually shows stronger mobility relative to the lighter Pb, and is more likely to transfer into soil exchangeable Pb fraction and carbonates phase. The lighter Pb shows stronger transfer ability from soil to cereal grain via root compared to the heavier Pb. However, the cereal grains have lower ²⁰⁶Pb/²⁰⁷Pb and higher ²⁰⁸Pb/²⁰⁶Pb ratios than root and tillage soil, similar to the airborne Pb and anthropogenic Pb, implying that a considerable amount of Pb in cereal grains comes from the atmosphere. The estimate model shows that 16.7–52.6% (average: 33.5%) of Pb in rice grain is the airborne Pb.     

Mg/Fe水滑石吸附水中磷的动力学及热力学研究

以MgCl2和FeCl3为原料通过共沉淀法制备了Mg/Fe水滑石,并对其进行焙烧得到了焙烧态Mg/Fe水滑石。采用X射线衍射(XRD)和傅里叶红外光谱(FTIR)对所得产物进行了结构表征。利用焙烧前后的水滑石作吸附剂吸附处理含磷废水,比较了两者对磷的吸附能力,并在不同温度和pH条件下进行了吸附动力学实验。结果表明,焙烧前后的水滑石对磷都具有很好的吸附能力,但300℃焙烧后水滑石的吸附能力提高了约5%。动力学实验表明,水滑石对磷的吸附可很好地用准二级动力学方程进行描述,其线性相关系数达0.999以上。在15~35℃下进行了等温吸附实验,结果发现水滑石对磷的吸附更符合Langmuir方程。经热力学研究发现,标准吸附焓变(ΔH0)0J/mol、标准吸附自由能(ΔG0)0J/mol和标准吸附熵变(ΔS0)0J/(mol·K),说明水滑石对磷的吸附反应是自发的吸热反应,且是一个熵增加的过程。     

Use of Stable Isotopes to Identify Sources of Mercury in Sediments: A Review and Uncertainty Analysis

Mass-dependent and mass-independent mercury isotope fractionation potentially generates unique source signatures that can be used to apportion contributions to sediment contamination. This article reviews findings from previous investigations that have used mercury isotopes to identify sources. It also discusses a mass balance mercury isotope fractionation model that simulates changes in isotopic source signatures in aquatic systems caused by natural biogeochemical cycling. According to the model, the extent of source signature alteration depends on chemical speciation, with more labile forms exhibiting greater isotopic fractionation. Apportionment is tractable when differences between δ²⁰²Hg of sources are larger than potential changes in isotopic signatures following the release of mercury into the environment.     

Iron isotopic fractionation in industrial emissions and urban aerosols

A study on tropospheric aerosols involving Fe particles with an industrial origin is tackled here. Aerosols were collected at the largest exhausts of a major European steel metallurgy plant and around its near urban environment. A combination of bulk and individual particle analysis performed by SEM–EDX provides the chemical composition of Fe-bearing aerosols emitted within the factory process (hematite, magnetite and agglomerates of these oxides with sylvite (KCl), calcite (CaCO₃) and graphite carbon). Fe isotopic compositions of those emissions fall within the range (0.08‰ < δ⁵⁶Fe < +0.80‰) of enriched ores processed by the manufacturer (−0.16‰ < δ⁵⁶Fe < +1.19‰). No significant evolution of Fe fractionation during steelworks processes is observed. At the industrial source, Fe is mainly present as oxide particles, to some extent in 3–4 μm aggregates. In the close urban area, 5 km away from the steel plant, individual particle analysis of collected aerosols presents, in addition to the industrial particle type, aluminosilicates and related natural particles (gypsum, quartz, calcite and reacted sea salt). The Fe isotopic composition (δ⁵⁶Fe = 0.14 ± 0.11‰) measured in the close urban environment of the steel metallurgy plant appears coherent with an external mixing of industrial and continental Fe-containing tropospheric aerosols, as evidenced by individual particle chemical analysis. Our isotopic data provide a first estimation of an anthropogenic source term as part of the study of photochemically promoted dissolution processes and related Fe fractionations in tropospheric aerosols.     

红壤地区镁肥对作物的效应

土壤交换性镁量愈低,镁肥对作物的增产效果愈显著。作物地上部含镁量和吸镁量也决定于交换性镁量大小;交换性镁水平与含镁量和吸镁量呈显著正相关。因此,土壤交换性镁能较好地反映土壤镁素对作物的有效性。此外,作物对镁肥的反应还受土壤交换性钾和钾肥施用的影响。当土壤交换性镁低于５０ ｍｇ／ｋｇ~（－１）,交换性 Ｋ／Ｍｇ比大于 １．３时,施用镁肥效果明显。     

Relationships between stable isotopes and metal contaminants in feathers are spurious and biologically uninformative

Stable isotopes of carbon (δ¹³C) and nitrogen (δ¹⁵N) are used frequently in ecotoxicological investigations of birds to relate contaminant levels to trophic position (δ¹⁵N) or foraging location (δ¹³C) and many researchers using avian feathers in such investigations use δ¹³C or δ¹⁵N as a predictor of contaminant concentrations. Contaminants, especially mercury, however, are integrated into feathers over different time periods than are stable isotopes, resulting in spurious relationships that have no biological meaning. I show the fundamental principles behind the conclusion that relating δ¹³C or δ¹⁵N to contaminant concentrations in feathers is not appropriate in light of the number of recent studies that have employed this approach, and make recommendations for those wishing to investigate the relationship between contaminants and stable isotope ratios.     

Atmospheric pollutants in alpine peat bogs record a detailed chronology of industrial and agricultural development on the Australian continent

Two peat bogs from remote alpine sites in Australia were found to contain detailed and coherent histories of atmospheric metal pollution for Pb, Zn, Cu, Mo, Ag, As, Cd, Sb, Zn, In, Cr, Ni, Tl and V. Dramatic increases in metal deposition in the post-1850 AD portion of the cores coincide with the onset of mining in Australia. Using both Pb isotopes and metals, pollutants were ascribed to the main atmospheric pollution emitting sources in Australia, namely mining and smelting, coal combustion and agriculture. Results imply mining and metal production are the major source of atmospheric metal pollution, although coal combustion may account for up to 30% of metal pollutants. A novel finding of this study is the increase in the otherwise near-constant Y/Ho ratio after 1900 AD. We link this change to widespread and increased application of marine phosphate fertiliser in Australia's main agricultural area (the Murray Darling Basin).     

Lead (Pb) isotopic fingerprinting and its applications in lead pollution studies in China: A review

As the most widely scattered toxic metal in the world, the sources of lead (Pb) observed in contamination investigation are often difficult to identify. This review presents an overview of the principles, analysis, and applications of Pb isotopic fingerprinting in tracing the origins and transport pathways of Pb in the environment. It also summarizes the history and current status of lead pollution in China, and illustrates the power of Pb isotopic fingerprinting with examples of its recent applications in investigating the effectiveness of leaded gasoline phase-out on atmospheric lead pollution, and the sources of Pb found in various environmental media (plants, sediments, and aquatic organisms) in China. The limitations of Pb isotopic fingerprinting technique are discussed and a perspective on its development is also presented. Further methodological developments and more widespread instrument availability are expected to make isotopic fingerprinting one of the key tools in lead pollution investigation.     

Diet shifts during egg laying: Implications for measuring contaminants in bird eggs

We combined stable isotope tracers of blood plasma, blood cells and egg contents with faecal analysis during pre-breeding and egg laying phases in two dipper species Cinclus cinclus and Cinclus mexicanus to determine the occurrence of dietary shifts during egg production and to assess consequences for egg contaminant loads. In both species, changes in δ¹³C (C. cinclus) or δ¹⁵N (C. mexicanus) in female plasma relative to red blood cells indicated a dietary shift during laying that was not observed in males. Eurasian dippers increased prey consumption as breeding approached, shifting from primarily trichopteran insect larvae to ephemeropterans and plecopterans. In American dippers, egg-laying females switched to feeding at a higher trophic level by consuming more fish. Eggs derived from higher trophic level diets contained more mercury (American dipper), polychlorinated biphenyls and some organochlorines, especially DDT metabolites. The results demonstrate how dietary changes during egg laying accompany the demands for egg production with consequences for contaminant deposition in avian eggs.