Investigation of the Adsorption and Desorption Capacities of Bojac Sandy Loam Soil from the Eastern Shore of Virginia

摘要

Due to the deteriorated water quality seen in the local estuaries of the Eastern Shore in Virginia a study was performed by Virginia Tech to study the causes of this problem. Copper-based protectants are used by tomato farmers on the Eastern Shore of Virginia to primarily fight fungi and bacteria. When runoff occurs, the copper is washed from the plants and fields to the surrounding waterways, effecting the aquatic life in these systems. However, some copper does sorb to the soil in and surrounding the fields and the sediment leaving the field. The fate and transport of this copper onto and off of the soil was investigated through a series of sorption and desorption experiments. The adsorption isotherms showed that as the amount of soil increases, the amount of copper adsorbed also increases. However, over time there was not a clear increase in copper Sorption, which indicates that the adsorption is a quick process and that an increase in time does not dramatically change the amount of copper the soil will sorb. For example, the amount of copper sorption at the first time interval of 2 hours is essentially the same as the amount sorbed at each following time interval of 24 hours, 48 hours, and 7 days. At the equilibrium concentration of 200 ppb, a value of 54 mg Cu/kg soil is seen for Bojac Sandy Loam soil, When copper laden soil was used in both 20 ppt saline and pure water desorption isotherms, copper did desorb from the soil into solution. Again this was an immediate process, the 30 minute readings were similar to both the 2 hour and 24 hour readings, thus the increased time did not significantly affect the amount of copper being released. Even though the trend was similar between the two experiments in that time did not have a large role in the amount of desorption, the zero salinity test had slightly higher amounts of copper desorption.