The sensitivity of ecosystems to acid inputs in the Hunter Valley, Australia

This study assesses the importance of H+ generation in the Hunter Valley from land use and coal-fired power stations. The Hunter Valley is a temperate coastal land system approximately 150 km north of Sydney. Land uses include forestry and national parks, grazing and farming, coal mining, coal-fired electricity generation and manufacturing. The H+ generated from land use in estimated from land suitability classes. Wet deposition is estimated from 10 years' rainwater chemistry data and dry deposition is estimated from modelled SO2 concentrations and a deposition velocity constant. The pH and pH buffer capacity of 51 soils were measured. H+ loads from land use ranged from 0.05 to 12 kmol H+/ha/year for forests and prime agricultural land, respectively. Estimated H+ deposition ranged from 0.27 to 0.65 kmol H+/ha/year, depending on the distance and direction from the power stations. The H+ load that will lead to critically low pH values in 50 years is 0.27, 0.60, 1.77 and 2.14 kmol H+/ha/year for four broad soil classes. The two most sensitive classes, with target loads of 0.27 and 0.60 kmol H+/ha/year, occupy 26% and 56% of the study are a respectively. Although the total contribution of H+ from land use is larger than from deposition (970 vs. 220 Mmol h+/year), H+ deposition may be important on low fertility non-agricultural soils with low pH buffer capacity. More detailed study of the areas with sensitive soils is warranted. 12 refs., 4 tabs