Long-term ionic increases from a central Appalachian forested watershed
- Download PDF (176.0 KB)
- This publication is available only online.
Journal of Environmental Quality. 20(1): 250-255.
The electrical conductivity of stream water draining from an unmanaged and undisturbed control watershed has been increasing rather steadily, about 0.03 mS m-1 yr-1, since 1971. During this period, NO–3 and Ca2+ concentrations increased and were shown to mathematically account for the ionic contribution to conductivity; therefore, they are believed to be primarily responsible for the increase. However, the percentage of conductivity explained by the two ions was different over time. The percentage of conductivity attributable to NO–3 increased in a pattern very similar to concentration. In contrast, the percentage of conductivity attributable to Ca2+ decreased slightly over time. The Ca2+ is believed to be pairing with the NO–3 as the NO–3 ions leach through the soil. While nitrification in mature stands can be strongly inhibited, limited nitrification , especially in forest gaps, and high anthropogenic inputs of NO–3 probably were primary sources of the leached NO–3. Preferential adsorption of SO 2-4, rather than NO–3, on soil colloids is given as an explanation for the lack of retention of NO–3 in the soil system and subsequent leaching to the stream.
Edwards, Pamela J.; Helvey, J. David. 1991. Long-term ionic increases from a central Appalachian forested watershed. Journal of Environmental Quality. 20(1): 250-255.