East Trinity Acid Sulfate Soil Remediation

(not documented)

QPWS
SCU
CRC CARE
Djunbunji

Science

On-ground work

(none)

Queensland Government ongoing funding; Natural Heritage Trust (Coastal acid sulfate soil program 2001-2003); and CRC CARE (2008-2015)

(not documented)

(not documented)

30 May 2000

Ongoing

Lime-Assisted Tidal Exchange has transformed the once acidified, terrestrial East Trinity landscape into a healthy and diverse, managed estuarine system. Strategic research has explained how, where, and most importantly, why, these environmentally relevant changes have occurred across the East Trinity site. The remediation of the site has progressed to the point that eco-tourism activities are undertaken by the Traditional Owners; the Mandingalbay Yidinji people.
In May 2000 the Queensland State Government purchased the 774ha East Trinity property to address the severe acid sulfate soil issues and protect the green backdrop to Cairns. The State Government scientists charged with the acid sulfate soil remediation devised a novel and untested Lime-Assisted Tidal Exchange (LATE) treatment strategy, which progressively and cautiously replaced the existing acidified freshwater environment with a managed tidal wetland system—ironically, by modifying and managing the tidal gate infrastructure that contributed to the problem when the site was developed for sugar cane production in the 1970s. Strategic application of hydrated lime (Ca(OH)2) to buffer incoming tidal water and, when necessary outgoing tidal water, was an essential control mechanism to prevent off-site acid and metal discharge during the active phase of LATE.
Changes in soil, water, vegetation and biota will continue to be monitored as the site progresses under the passive LATE management strategy, where controlled tidal exchange alone manages the acid sulfate soils.

The project will:

• reduce the environmental risk posed by the acid sulfate soils;
• neutralise the existing soil and water acidity in LATE treated areas;
• prevent further oxidation of pyrite and acid production in LATE treated areas;
• improve water quality in the creeks and drains of the East Trinity property and discharging into Trinity Inlet; and
• replace an acidified terrestrial landscape with a healthy estuarine ecosystem

Lime-Assisted Tidal Exchange (LATE) has transformed the East Trinity landscape while the biogeochemical understanding of LATE has transformed the legacy broad acre acid sulfate soil remediation paradigm.
The remediation at East Trinity involves the controlled re-introduction of daily tidal exchange, with the strategic addition of hydrated lime to enhance the natural acid buffering capacity of sea water. LATE keeps the soil wet and neutralises some of the acidity, which stimulates the proliferation of naturally occurring sulfate and iron reducing bacteria. Studies have shown that the bulk of the remediation at East Trinity was due to the microbial and chemical reduction of iron and sulfate. Insitu bicarbonate production, a byproduct of this process, further neutralises soil acidity and promotes the beneficial microbial weathering of acid minerals. The process becomes self-propelling toward a stable, neutral and healthy soil-wetland system with good water quality.

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