In Kentucky, hundreds of horse farms dot the land. Thousands of miles of wooden fence posts outline these farms, which have become an icon of the Kentucky landscape. What goes unnoticed is the potential impact these fence posts are having on the environment.
Arsenic (As) is a poisonous metalloid, an element with metal and non-metal properties, that can have a significant impact on ecosystem function and pose potential health risks to humans. Installation and disposal of chromated copper arsenate (CCA) treated lumber introduces arsenic into the environment, due to the metalloid’s use as an insecticidal agent. The use of CCA treated wood for residential applications, such as decking and child play structures, has stopped. However, CCA treated lumber is still used for agricultural applications, including farm fencing.
In a study published in the current issue of the Journal of Environmental Quality, University of Kentucky assistant professor David McNear and his graduate student Donald Schwer III used CCA treated fence posts to investigate which soil properties had the greatest influence on As distribution. The pair gathered their data along a fence line that had been in place for 20 years, which ran across different soil series, parent material, drainage classes and slope.
Pits were dug to a depth of 1.5m alongside several fence posts at different landscape positions. Approximately 60 soil samples were taken around each post inside the pits. Total metal distribution in the soils was found using ICP-MS, a sensitive analytical technique used to determine metal concentrations and generate maps that show the extent of metal leaching.
The study revealed that more As was mobilized from the posts moving down the topographic slope. Minerals containing Al played a key role in As sorption at low soil pH levels, while Fe-bearing minerals did the same at high pH levels. The amount of As loading in the soil was found to be a substantial 8 to 12 kg/km-1.
“We were admittedly surprised when we did the calculations and discovered how much As per kilometer of fence row is released into the soil,” explained McNear, co-author of this study. “These results led us to recommend considering CCA alternatives for agricultural applications. Any chance to reduce the amount of As unintentionally released into the environment would be a good opportunity to protect human and environmental health”.
Research is ongoing in Dr. McNear’s Rhizosphere Science Lab to determine the leaching of other harmful metals around these fence posts. Researchers are also studying the variety of vegetation growing near the fence posts to determine how the plant species are able to tolerate such high metal concentrations.
See the full study here.