Surface and sub-surface salinity in and around acid sulfate soil scalds in the coastal floodplains of New South Wales, Australia

Abstract

Two-metre-deep soil profiles at 10 acid sulfate soil (ASS) scalds along the coast of New South Wales (NSW), Australia, were examined for salinity indicators. At 5 of the sites, permanently vegetated areas adjacent to the ASS-scalded land were also tested. Throughout the profiles, most sites had high soluble chloride (Cl−) concentrations (≤17 mg/g soil) and high soluble sulfate (SO42−) concentrations (≤17 mg/g soil). Very low Cl− : SO42− ratios (≤3) indicated active pyrite oxidation. Soil salinity (measured as electrical conductivity, EC) was extremely high in the top 2 m of most of the ASS scalds when related to the growth requirements of the typical introduced pasture species that were planted in these areas following drainage. This allows salinity, in addition to the extremely low pH of the surface soils, to contribute to land denudation, which can instigate or perpetuate pyrite oxidation and ASS-related land scalding. Although the sites had shallow watertables and soil-moisture content was high, the surface soil (top 0.10 m) of the scalds had consistently higher soluble Cl− and SO42− concentrations and EC than adjacent vegetated areas. All coastal ASS areas investigated, typically freshwater backswamps used for cattle grazing, were underlain by estuarine-derived sediments containing saline ground water. The results demonstrate that revegetation of ASS scalds must include investigation and management of salinity, in addition to acidity, within the soil profile and at the soil surface.

Problems, Management, and Prospects of Acid Sulphate Soils in the Ganges Delta

“…Another notable feature in these soils is that the highest salinity usually coincides with the lowest pH, which is unusual in normal saline soils [91,92]. The sulphate salts of Fe and Al referred to as acid salts [93] cause both low pH (acidity) as well as osmotic stress similar to neutral salts, as well as toxicity effects on seed germination and plant growth due to excess Al and Fe [92]. Therefore, if the salinity of coastal soils is only thought to originate from seawater, and reclamation practices are oriented towards blocking out seawater from these soils, a cycle of sulphide oxidation may be set off with disastrous acidity as well as salinity consequences for the soils and associated ecosystems [91].…”

“…In these soils, salts produced upon the oxidation of the sulphides may be more important than the direct addition from seawater [91]. This high salinity due to high soluble chloride (Cl − ) concentrations (≤17 mg g −1 soil) and high soluble sulphate (SO 4 2− ) concentrations (≤17 mg g −1 soil), in addition to the extremely low pH of the surface soils contributes to land denudation, instigation or perpetuation of pyrite oxidation, and ASS-related land scalding [92]. Another notable feature in these soils is that the highest salinity usually coincides with the lowest pH, which is unusual in normal saline soils [91,92].…”

“…This high salinity due to high soluble chloride (Cl − ) concentrations (≤17 mg g −1 soil) and high soluble sulphate (SO 4 2− ) concentrations (≤17 mg g −1 soil), in addition to the extremely low pH of the surface soils contributes to land denudation, instigation or perpetuation of pyrite oxidation, and ASS-related land scalding [92]. Another notable feature in these soils is that the highest salinity usually coincides with the lowest pH, which is unusual in normal saline soils [91,92]. The sulphate salts of Fe and Al referred to as acid salts [93] cause both low pH (acidity) as well as osmotic stress similar to neutral salts, as well as toxicity effects on seed germination and plant growth due to excess Al and Fe [92].…”

“…Soil Syst. 2022, 6, x FOR PEER REVIEW 11 of 28 pH of the surface soils contributes to land denudation, instigation or perpetuation of pyrite oxidation, and ASS-related land scalding [92]. Another notable feature in these soils is that the highest salinity usually coincides with the lowest pH, which is unusual in normal saline soils [91,92].…”

Caracterización y dispersión del material aerotransportado en el entorno de la antigua zona de minería metálica de Cartagena-La Unión: impactos y riesgos

“…La acumulación de sales en los horizontes superficiales es común en los suelos y residuos afectados por el drenaje ácido de mina (Cánovas et al, 2008, Hammarstrom et al, 2005, Bayless & Olyphant 1993; sin embargo, no es exclusiva de los entornos mineros, ya que idénticos procesos suceden en ciertos suelos naturales como los suelos ácidos sulfatados (Acid Sulfate Soils) (Rosicky et al, 2006) y los suelos aluviales salinos de zonas semiáridas (Ducloux et al, 1994).…”