What are Acid Sulfate Soils? The Causes of Soil Acidity and How to Manage Them
Acid sulfate soils (ASS) are naturally occurring soils and sediments rich in iron sulfides, notably pyrite. Typically, they form in the waterlogged, anaerobic conditions found in coastal regions, estuaries and wetlands.
In their undisturbed state, ASS are relatively harmless. However, when exposed to air through activities like excavation or drainage, the iron sulfides oxidise to produce sulfuric acid.
This acidification can lead to significant environmental and structural issues, including soil degradation, water contamination and infrastructure damage.
Engaging an experienced professional is the surest way of managing these issues before they arise. As a proudly Western Australian environmental consultancy, West Soil & Water provides a range of acid sulfate soil services in Perth.
If you would like to enquire about these services, you can contact WSW at sam@westsoilandwater.com.au or on 0424 021 264.
What is Acid Sulfate Soil and What Causes It?
The primary cause of increased acidity in ASS is oxidation of iron sulfides. This process generates sulfuric acid, which lowers the soil pH and can mobilise toxic metals such as aluminium and iron, further exacerbating environmental harm.
Activities that commonly disturb ASS include:
Construction and Development: Works on infrastructure projects like roads, tunnels and residential developments can expose ASS to air, triggering acidification.
Agricultural Practices: Drainage of wetlands for farming can lower the water table, leading to the oxidation of previously submerged sulfide minerals.
Groundwater Extraction: Excessive pumping can reduce groundwater levels, exposing ASS to atmospheric oxygen.
How can Acid Sulfate Soils be Managed?
Effective management of ASS is crucial to prevent environmental degradation and infrastructure damage. WSW provides two key services to assist in managing ASS:
Baseline Investigations: WSW carries out investigations to determine the presence, extent and severity of ASS on your site. This information is used as a foundation for future planning and monitoring.
Acid Sulfate Soil Management Plans (ASSMPs): We develop and implement ASSMPs to ensure potential risks are identified and managed proactively. These plans outline strategies for soil handling, treatment and monitoring throughout the lifecycle of a project.
Treatment and Monitoring: We tailor treatment solutions to the needs of your site and conduct ongoing monitoring to ensure their efficacy.
Other management strategies include:
Preventing Disturbance: Where possible, avoid activities that expose ASS to air. This may involve redesigning projects to minimise excavation or altering drainage plans.
Soil Treatment: If disturbance is unavoidable, you can neutralise soil acidity by applying alkaline materials (such as agricultural lime). This treatment should be carefully calculated to ensure sufficient neutralisation.
Water Management: Implementing controlled drainage and maintaining appropriate water tables can help prevent the oxidation of sulfides. In some cases, re-flooding areas with water can restore anaerobic conditions, halting further acid production.
West Soil & Water: Comprehensive Acid Sulfate Soil Management Services in Perth
Understanding and managing acid sulfate soils is essential for sustainable development and environmental protection. Proactive management minimises potential damage and contributes to the long-term viability of your projects and the surrounding ecosystems.
The West Soil & Water team specialises in these exact management strategies, providing comprehensive solutions to clients across Western Australia.
If you would like to speak with a member of our team about baseline investigations, management plans or treatment solutions, contact WSW at sam@westsoilandwater.com.au or on 0424 021 26.