A LABORATORY SIMULATION OF CHLORITE WEATHERING IN AND INCEPTISOL UNDER POST-FIRE CONDITIONS

Chlorite [(Mg, Fe ²⁺)₅Al(Si₃0₁₀)(OH)₈] is the dominant clay mineral of the inceptisols of Warren County, New Jersey. Chlorite may undergo alterations following the application of fire. A 2009 field-based study analyzed these alterations following a prescribed fire at Double N Farm. The results of the study indicated weathering of chlorite in the sub-surface (30+cm) due to chemical modification of rainwater as a result of cation leaching from ash. The purpose of this study was to investigate the weathering of chlorite following prescribed fire-simulated conditions. The goal was to attempt to recreate the chlorite weathering observed in the 2009 study in order to ascertain if ash input is a possible weathering mechanism.

Two laboratory simulations were conducted by placing soil into PVC pipes, recreating the soil profile of Double N Farm. The pipes were capped at the bottom and a small hole was drilled at the bottom center to simulate the restrictive layer observed at the field site. The experimental pipes were treated with five centimeters of ash. Rainwater was applied to the columns in accordance to the volume of rainfall that affected the field study location following the prescribed burn. It was assumed that moisture content was a key component to the previously observed weathering. Therefore, the second of the two simulations was treated with additional rainwater through a smaller diameter PVC pipe, inside the top of the existing PVC column. This would allow rainwater to penetrate further down into the soil profile, while bypassing the ash layer, allowing for more natural moisture conditions. It was anticipated that increased evaporation would be a factor in the controlled laboratory environment. Clay was extracted from the laboratory columns at each time interval and analyzed by X-ray diffraction. Positions and relative intensities of the chlorite peaks were analyzed to examine alterations resulting from the ash treatment. The results indicated that ash treated samples did not show significant differences in chlorite peak positions or relative intensities from that of the control group. The results of the 2009 study were not recreated. It is believed that ash layer thickness and associated base ion concentration may be the contributing factor to the observed weathering of the past study.