EFFECT OF SWINE MANURE ON LIMESTONE DISSOLUTION

Localized wastewater sources on karst terrain that discharge directly into the subsurface can enhance the dissolu­tion of limestone. Previous work suggests that landfill leachate leads to the formation of localized permeable fis­sures in karst. Based on this previous work, we hypothesized that manure application may also have an enhanced effect on dissolution of limestone. To address this hypothesis, we conducted a batch laboratory experiment where we observed the effect of swine manure on limestone dissolution. Six treatments were constructed using combinations of diluted swine manure, limestone, soils and deionized water. Limestone of the Boone Formation and overlying soils were collected from Newton County, Arkansas, a karst region characterized by extensive agriculture, including a swine Confined Animal Feeding Operation. Liquid manure was collected from the Virginia Tech swine farm. During the six week experiment, we measured pH, Ca and Mg of the experimental solution. Results show an increase in the pH and in the Ca and Mg concentrations in the treatment containing limestone and manure in comparison to the control (no manure), suggesting that the manure accelerated the dissolution of the limestone. Data will be used to calculate rates to allow for quantitative comparison of the effect of manure on limestone dissolution.