The Henry's law constant of trichloroacetic acid [K′H (mol kg⁻¹ atm⁻¹) for the equilibrium CCl₃COOH₍g₎ ⇌ CCl₃COOH₍ₐq₎] has been determined from measured partial pressures over aqueous solutions at 298.15 K and 308.15 K. Its value is given by: ln(K′H) = (11.21 ± 0.5) – 8.66 × 10³ (l/Tᵣ – l/T) where T (K) is temperature and Tᵣ is equal to 298.15 K, for an aqueous phase dissociation constant (Kₐ) of 0.55 mol kg⁻¹ determined from literature osmotic coefficient and electromotive force data. Accuracy is estimated to be 4–30% in the product K′HKₐ. Trichloroacetic acid is highly soluble and will partition strongly into aqueous atmospheric aerosols, and completely into fog and cloud water. Its occurrence and transport in the environment are therefore to be associated primarily with liquid phases.

Acid deposition is considered to be a major environmental problem in China, but information about effects on soils and waters is scarce. To contribute to increased knowledge about the problem a small catchment (about 7 ha) in the outskirts of Guiyang, the provincial capital of Guizhou in south-western China, was instrumented for collection of precipitation, throughfall, soil water and stream water. In addition soil samples have been collected and analyzed for key properties. Median pH in the precipitation is 4.40 (quartiles: 4.19 and 4.77) and the median sulfate concentration 228 µeq/L (quartiles: 147 and 334 µeq/L). The dry deposition of both SO₂ and alkaline dust is considerable. The sum of wet deposition of sulfate and dry deposition of SO₂ has been estimated to about 8.5 gSm⁻²yr⁻¹. The total S-deposition may be somewhat higher due to dry deposition of sulfate and occult deposition. In soil water, SO₄ ²⁻ is the major anion, generally ranging from 300 to 2500 µeq/L in the different plots. Calcium is an important cation, but there is also a considerable contribution of aluminum from the soil. In some of the plots the concentrations of inorganic monomeric aluminum (Ali) are typically between 200 and 400 µm. Potential harmful levels of aluminum and/or high Ali/(Ca²⁺ + Mg²⁺) molar ratios occur in the catchment, but damages to vegetation have not yet been reported. In most cases exchangeable aluminum accounts for between 75 and 95% of the total effective cation exchange capacity (CECE) in the mineral soils. The aluminum chemistry cannot easily be explained by conventional models as the Gaines-Thomas ion-exchange equation or equilibrium with an Al(OH)₃ mineral phase. The stream water is generally less acidic and has considerably lower concentrations of aluminum than the soil water, even though quite acid events have been observed (pH < 4.4). The median pH values are 4.9 and 5.0 in the two first order streams and 6.3 in the dam at the lower boarder of the catchment.