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The concentrations of H⁺, NO⁻₃, SO²⁻₄, soluble Al, and undissociated acidity were measured in throughfall, soil solution, and streamflow during five rainfall events on two steeply sloping forested sites in the Great Smoky Mountains. The sources and sinks of these chemical species on a spruce-birch (Picea rubens Sarg.-Betula lenta L.) site were compared to those on a hardwood site. The chemistry of water collected in zero-tension lateral flow collectors during storm events was contrasted with water collected at corresponding depths in tension lysimeters. Tension lysimeter samples from the spruce site had much higher concentrations than those from the hardwood site of H⁺ (3–7 ×), SO²⁻₄ (1.5–2 ×), Al (2–5 ×), and undissociated acidity (1.5–2 ×). Baseflow from a first-order stream draining the spruce site was significantly higher in Al and H⁺ than hardwood site baseflow. On both sites the largest sources of H⁺ and undissociated acidity were throughfall (incident precipitation + canopy sources) and the O horizon; on the spruce site the O horizon was the predominant source of each. Aluminum and SO²⁻₄ also increased dramatically with passage through the O horizons, especially on the spruce site. Only the spruce site generated appreciable lateral flow. Nitrate, undissociated acidity, and Al concentrations in spruce site lateral flow were not significantly (p |
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