The effects of acidic deposition on cation leaching from three deciduous forest canopies.

For 3 deciduous forests in E Tennessee currently receiving wet and dry acidic deposition, retention of atmospherically deposited cations (H+ and NH+4 exceeded retention of deposited anions (NO-3) on a charge-equivalent basis. Charge balance was maintained by ion exchange between the deposited cations and K+, Ca2+, and Mg2+ on the canopy surfaces. Some 40-60% of the leaching of K+, Ca2+, and Mg2+ from these canopies results from this exchange process, with the remainder attributable to co-leaching with plant-derived anions. Because the cation exchange can be largely attributed to retention of deposited H+, it is interpreted as a measure of the acidic deposition effect on foliar cation leaching. Dry deposition was an important input for most of the major cations and anions. Organic anions may be important counter ions to cation leaching, especially in the absence of acidic deposition. Acid-base reactions in the canopy can obscure the true H+-exchange reactions between the deposition and the canopy. -from Authors

Duke Scholars

Author Daniel D. Richter Earth and Climate Sciences