Bioavailability of Arsenic to Edible Plants Grown in Poultry Litter Applied Soils

Jennifer Parker, Research Associate, Frontier Geosciences, 414 Pontius Ave. N, Seattle, WA 98109, Tel: 206-622-6960, Fax: 206-622-6870, Email: jennp@FrontierGeosciences.com
Nicolas Bloom, Senior Research Scientist, Frontier Geosciences, 414 Pontius Ave. N, Seattle, WA 98109, Tel: 206-622-6960
Hakan Gürleyük, Ph.D., Research Scientist, Frontier Geosciences, 414 Pontius Ave. N, Seattle, WA 98109, Tel: 206-622-6960

The poultry industry is one of the largest and fastest growing livestock production systems in the world.  Poultry is often treated with organo-arsenical feed additives used to control coccidial intestinal parasites, improve feed efficiency, and promote rapid weight gain. Since these arsenic compounds are not readily absorbed by poultry, poultry litter may contain as much as 30-50 mg As kg^-1. Approximately, 90% of the 13 million metric tons of poultry litter annually produced in the U.S. is applied as a fertilizer on cropland and pasture. There are already reports of high inorganic arsenic concentrations in rivers close to these chicken farms and chicken litter applied fields during/after storm events. Another important but unstudied aspect of this application is the possible accumulation of arsenic in agricultural plants. This study focuses on the bioavailability of As to various edible plants grown in soils amended with poultry litter. Arsenic speciation changes in the soil and plants over time was also monitored. For comparison, soils were also amended with inorganic As species and differences in plant bioavailability was assessed. In addition, we evaluated the ability of different leach solutions to target the desired As species, as well as a variety of chemical soil extractions to determine their usefulness in predicting plant bioavailable As in soils. Arsenic speciation was conducted using both ion chromatography - inductively coupled mass spectrometry (IC-ICP-MS) and hydride generation - cryogenic trapping - atomic absorption spectroscopy (HG-CT-AAS).

Determination of Inorganic Arsenic in Soils, Surface Waters and Plants in Old Mining Sites of Maldon, Australia

Khawar Sultan and Kim Dowling, School of Science and Engineering, University of Ballarat, Mt. Helen, Vic 3353, Australia

Arsenic concentrations in surface water, plant and soil (< 2 mm fraction) samples were collected from six different sites located in area that had been affected due to mining, smelter activities and natural enrichment due to geological mineralization. Concentrations in excess of 1000 mg/kg of arsenic has been recorded in topsoils (0-10 cm) and more than 51% of soil samples reported concentrations >500 mg/kg. Concentrations of As in freshwater at sites exceeded permissible limits even though atmospheric contribution is less significant during the past decades. Total arsenic concentration in all soil samples were higher than those found at non-contaminated sites particularly at State Battery location which recorded extreme level of 3265 mg/kg of As. The total arsenic concentrations of various plants were in the range  ~ 0.18-6.9 mg/kg of As (dry mass) and was observed bioavailable; with difference depending on site location and possibly plant species.

The Maldon mining district has been mined for years for gold and has resulted in waste rock and tailings, rich in sulphides, over an area including the city itself. Oxidation of these sulphides result in mobility of As and other heavy metals into runoff and drains into local drainage tributaries and water bodies, which ultimately may contaminate groundwater. Wide range of pH (3.8 ~ 8.3) and Eh (-286 ~ +396 mV) has been measured in surface waters. Total dissolved inorganic As in surface waters was measured as high as 11.5 mg/l in acidified mine drainage and possible adsorption on to Fe oxides is taking place preventing extreme mobility. Plants growing on these sites were shown to accumulate arsenic to levels as high as 6.9 mg/kg of As. Elevated As concentrations in soils, waters and plants may also have originated from natural source partly but strong indications by high concentration in particular sites due to mining activity was observed clearly.

The current work focused on identification of localized contamination of As and its possible mobility and bioavailability. This study can be useful to examine the measures to prevent the mobilization of the contaminant source material in future.

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