INTRODUCTION A recent hydroponic study conducted in our laboratories demonstrated that significan... more INTRODUCTION A recent hydroponic study conducted in our laboratories demonstrated that significant isotope fractionation of Zn occurs during uptake from nutrient solutions by rice, lettuce and tomato plants (Weiss et al. 2005). We conducted a field study at the International Rice Research Institute (IRRI) to assess if isotopic fractionation can also be found under natural conditions. This work is part of a larger study looking into the controls of isotopic fractionation of Zn and Fe during plant nutrient uptake (Chapman et al. 2006). METHODS Rice seedlings were transplanted into two 10 × 25 m plots at IRRI's experimental farm, Los Baños, Laguna, Philippines, the first containing a Zn-deficient soil (Typic Hydraquent from Tiaong, Quezon, Philippines), and the second containing the same soil treated with 50 kg ha -1 Zn in the form of ZnSO 4 , ten days prior to transplantation. After 35 days, plants were harvested and soil directly surrounding the plant roots were collected. Plant ...
Journal of Geophysical Research D: Atmospheres, 2013
ABSTRACT [1] Numerical model simulations provide a useful platform for investigating the interact... more ABSTRACT [1] Numerical model simulations provide a useful platform for investigating the interactions between the atmospheric dust cycle and environmental change in Asia. However, model validation is still limited by the scarcity of ground observations of past terrestrial dust deposition fluxes. Here we apply a regional atmosphere-chemistry/aerosol climate model to simulate Asian dust emissions, transport, and deposition over East Asia during the years 1996–1998 and compare the present-day deposition fluxes and dominant dust sources obtained from the numerical simulations to those measured in a high-resolution Holocene palaeodust peat record on the eastern Qinghai-Tibetan Plateau. The model was found to produce reasonable dust emission fluxes from the Chinese dust sources, with average annual emissions of 179 Mt y−1, and successfully reproduced both the dominant dust sources and average deposition fluxes to the peat core, with modeled and observed fluxes of 6.1 g m−2 y−1. Sensitivity tests show that modeled dust fluxes are sensitive to the parameterization of erodible surfaces, and future development of the regional model to simulate dust emissions in Asia should include an improved scheme for the soil surface properties. The results presented here suggest that the regional model holds the potential to study past and present dust cycles in Asia but evidence the need for both further refinement of the model's dust parameterizations in this region and more high-resolution terrestrial validation data sets such as peat archives. This study demonstrates how present-day simulations, for which reanalysis data is available as boundary conditions, are useful tools to explore the relationship between the dust cycle and environmental change during the Holocene.
Lead concentrations and isotope ratios were measured in North Atlantic surface water samples coll... more Lead concentrations and isotope ratios were measured in North Atlantic surface water samples collected in 1981 (29°-79°N, 6°E-49°W) and in 1989 (23°-39°N, 29°-68°W). In the early 1980s, 206Pb/207Pb ratios in the North African Basin averaged 1.193 +/- 0.005 (1 sigma). Similar radiogenic ratios within the level of analytical precision (average 0.29%) were found in the Labrador and Iceland Basins (1.198 +/- 0.006) and in the Norwegian Sea (1.196 +/- 0.008). These radiogenic mixed layer signatures along with atmospheric global lead emission patterns suggest that most North Atlantic lead in the early 1980s was derived from North American leaded gasoline. Samples in the East Iberian Basin near Portugal and France showed lower 206Pb/207Pb ratios, between 1.167 and 1.182, indicating a significant influence of less radiogenic atmospheric lead transported from Europe and possibly the influence of the Rio Tinto acid mine drainage very close to shore in the Gulf of Cadiz. [Pb] across the entire...
Osmium is among the least abundant elements in the Earth&... more Osmium is among the least abundant elements in the Earth's continental crust. Recent anthropogenic Os contamination of the environment from mining and smelting activities, automotive catalytic converter use, and hospital discharges has been documented. Here we present evidence for anthropogenic overprinting of the natural Os cycle using a ca. 7000-year record of atmospheric Os deposition and isotopic composition from an ombrotrophic peat bog in NW Spain. Preanthropogenic Os accumulation in this area is 0.10 +/- 0.04 ng m(-2) y(-1). The oldest strata showing human influence correspond to early metal mining and processing on the Iberian Peninsula (ca. 4700-2500 cal. BP). Elevated Os accumulation rates are found thereafter with a local maximum of 1.1 ng m(-2) y(-1) during the Roman occupation of the Iberian Peninsula (ca. 1930 cal. BP) and a further increase starting in 1750 AD with Os accumulation reaching 30 ng m(-2) y(-1) in the most recent samples. Osmium isotopic composition ((187)Os/(188)Os) indicates that recent elevated Os accumulation results from increased input of unradiogenic Os from industrial and automotive sources as well as from enhanced deposition of radiogenic Os through increased fossil fuel combustion and soil erosion. We posit that the rapid increase in catalyst-equipped vehicles, increased fossil fuel combustion, and changes in land-use make the changes observed in NW Spain globally relevant.
INTRODUCTION A recent hydroponic study conducted in our laboratories demonstrated that significan... more INTRODUCTION A recent hydroponic study conducted in our laboratories demonstrated that significant isotope fractionation of Zn occurs during uptake from nutrient solutions by rice, lettuce and tomato plants (Weiss et al. 2005). We conducted a field study at the International Rice Research Institute (IRRI) to assess if isotopic fractionation can also be found under natural conditions. This work is part of a larger study looking into the controls of isotopic fractionation of Zn and Fe during plant nutrient uptake (Chapman et al. 2006). METHODS Rice seedlings were transplanted into two 10 × 25 m plots at IRRI's experimental farm, Los Baños, Laguna, Philippines, the first containing a Zn-deficient soil (Typic Hydraquent from Tiaong, Quezon, Philippines), and the second containing the same soil treated with 50 kg ha -1 Zn in the form of ZnSO 4 , ten days prior to transplantation. After 35 days, plants were harvested and soil directly surrounding the plant roots were collected. Plant ...
Journal of Geophysical Research D: Atmospheres, 2013
ABSTRACT [1] Numerical model simulations provide a useful platform for investigating the interact... more ABSTRACT [1] Numerical model simulations provide a useful platform for investigating the interactions between the atmospheric dust cycle and environmental change in Asia. However, model validation is still limited by the scarcity of ground observations of past terrestrial dust deposition fluxes. Here we apply a regional atmosphere-chemistry/aerosol climate model to simulate Asian dust emissions, transport, and deposition over East Asia during the years 1996–1998 and compare the present-day deposition fluxes and dominant dust sources obtained from the numerical simulations to those measured in a high-resolution Holocene palaeodust peat record on the eastern Qinghai-Tibetan Plateau. The model was found to produce reasonable dust emission fluxes from the Chinese dust sources, with average annual emissions of 179 Mt y−1, and successfully reproduced both the dominant dust sources and average deposition fluxes to the peat core, with modeled and observed fluxes of 6.1 g m−2 y−1. Sensitivity tests show that modeled dust fluxes are sensitive to the parameterization of erodible surfaces, and future development of the regional model to simulate dust emissions in Asia should include an improved scheme for the soil surface properties. The results presented here suggest that the regional model holds the potential to study past and present dust cycles in Asia but evidence the need for both further refinement of the model's dust parameterizations in this region and more high-resolution terrestrial validation data sets such as peat archives. This study demonstrates how present-day simulations, for which reanalysis data is available as boundary conditions, are useful tools to explore the relationship between the dust cycle and environmental change during the Holocene.
Lead concentrations and isotope ratios were measured in North Atlantic surface water samples coll... more Lead concentrations and isotope ratios were measured in North Atlantic surface water samples collected in 1981 (29°-79°N, 6°E-49°W) and in 1989 (23°-39°N, 29°-68°W). In the early 1980s, 206Pb/207Pb ratios in the North African Basin averaged 1.193 +/- 0.005 (1 sigma). Similar radiogenic ratios within the level of analytical precision (average 0.29%) were found in the Labrador and Iceland Basins (1.198 +/- 0.006) and in the Norwegian Sea (1.196 +/- 0.008). These radiogenic mixed layer signatures along with atmospheric global lead emission patterns suggest that most North Atlantic lead in the early 1980s was derived from North American leaded gasoline. Samples in the East Iberian Basin near Portugal and France showed lower 206Pb/207Pb ratios, between 1.167 and 1.182, indicating a significant influence of less radiogenic atmospheric lead transported from Europe and possibly the influence of the Rio Tinto acid mine drainage very close to shore in the Gulf of Cadiz. [Pb] across the entire...
Osmium is among the least abundant elements in the Earth&... more Osmium is among the least abundant elements in the Earth's continental crust. Recent anthropogenic Os contamination of the environment from mining and smelting activities, automotive catalytic converter use, and hospital discharges has been documented. Here we present evidence for anthropogenic overprinting of the natural Os cycle using a ca. 7000-year record of atmospheric Os deposition and isotopic composition from an ombrotrophic peat bog in NW Spain. Preanthropogenic Os accumulation in this area is 0.10 +/- 0.04 ng m(-2) y(-1). The oldest strata showing human influence correspond to early metal mining and processing on the Iberian Peninsula (ca. 4700-2500 cal. BP). Elevated Os accumulation rates are found thereafter with a local maximum of 1.1 ng m(-2) y(-1) during the Roman occupation of the Iberian Peninsula (ca. 1930 cal. BP) and a further increase starting in 1750 AD with Os accumulation reaching 30 ng m(-2) y(-1) in the most recent samples. Osmium isotopic composition ((187)Os/(188)Os) indicates that recent elevated Os accumulation results from increased input of unradiogenic Os from industrial and automotive sources as well as from enhanced deposition of radiogenic Os through increased fossil fuel combustion and soil erosion. We posit that the rapid increase in catalyst-equipped vehicles, increased fossil fuel combustion, and changes in land-use make the changes observed in NW Spain globally relevant.
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