Soil chemistry and acidification risk of acid sulfate soils on a temperate estuarine floodplain in southern Australia

Soil Research ◽  
2016 ◽  
Vol 54 (7) ◽  
pp. 787 ◽  
Author(s):  
C. C. Yau ◽  
V. N. L. Wong ◽  
D. M. Kennedy
Keyword(s):  
Soil Chemistry ◽  
Acid Sulfate Soils ◽  
Shell Material ◽  
Acid Sulfate ◽  
Estuarine Processes ◽  
Acid Neutralising Capacity ◽  
Eastern Australia ◽  
Actual Acidity ◽  
Sulfate Soils ◽  
Soil And Water

The distribution and geochemical characterisation of coastal acid sulfate soils (CASS) in Victoria in southern Australia is relatively poorly understood. This study investigated and characterised CASS and sulfidic material at four sites (wetland (WE), swamp scrub (SS), woodland (WO) and coastal tussock saltmarsh (CTS)) on the estuarine floodplain of the Anglesea River in southern Australia. Shell material and seawater buffered acidity generated and provided acid-neutralising capacity (up to 10.65% CaCO3-equivalent) at the sites located on the lower estuarine floodplain (WO and CTS). The SS site, located on the upper estuarine floodplain, can potentially acidify soil and water due to high positive net acidity (>200molH+t–1) and a limited acid-neutralising capacity. High titratable actual acidity in the SS and WO profiles (>270molH+t–1) were the result of high organic matter in peat-like layers that can potentially contribute organic acids in addition to acidity formed from oxidation of sulfidic sediments. The results of the present study suggest that the environments and chemistry of acid sulfate soils in southern Australia are distinct from those located in eastern Australia; this may be related to differences in estuarine processes that affect formation of acid sulfate soils, as well as the geomorphology and geology of the catchment.

The measurement of actual acidity in acid sulfate soils and the determination of sulfidic acidity in suspension after peroxide oxidation

Soil Research ◽  
2002 ◽  
Vol 40 (7) ◽  
pp. 1133 ◽  
Author(s):  
Angus E. McElnea ◽  
Col R. Ahern ◽  
Neal W. Menzies
Keyword(s):  
Regression Line ◽  
Correction Factors ◽  
Acid Sulfate Soils ◽  
Peroxide Oxidation ◽  
Acid Sulfate ◽  
Inorganic Sulfur ◽  
Actual Acidity ◽  
Sulfate Soils ◽  
The Relationship

Improvements to the routine methods for the determination of actual acidity in suspension for acid sulfate soils (ASS) are introduced. The titratable sulfidic acidity (TSA) results using an improved peroxide-based method were compared with the theoretical acidity predicted by the chromium reducible sulfur method for 9 acid sulfate soils. The regression between these 2 measures of sulfidic acidity was highly significant, the slope of the regression line not significantly different from unity (P = 0.05) and the intercept not significantly different from zero. This contrasts with results of other workers using earlier peroxide oxidation methods, where TSA substantially underestimated the theoretical acidity predicted by reduced inorganic sulfur analysis. Comparison was made between the 2 principal measurements from the improved peroxide method (TSA and SPOS), with SPOS converted to theoretical sulfidic acidity to allow comparison. The relationship between these 2 measurements was highly significant. The effects of titration in suspension, as well as raising titration end points to pH 6.5, were investigated, principally with respect to the titratable actual acidity (TAA) result. TAA results obtained by KCl extraction were compared with those obtained using BaCl2, MgCl2, and water extraction. TAA in 1 M KCl suspensions titrated to pH 6.5 agreed well with titratable actual acidity measured using the 25-h extraction approach of the Lin et al. (2000a) BaCl2 method. Both BaCl2 and KCl solutions were ineffective at fully recovering acidity from synthetic jarosite without repeated extraction and titration. The application of correction factors for the estimation of total actual acidity in ASS is not supported by the results of this investigation. Acid sulfate soils that contain substantial quantities of jarosite or other acid-producing but relatively insoluble sulfate minerals continue to prove problematic to chemically analyse; however, an approach for estimating this component is discussed.

Oxidation rate of pyrite in acid sulfate soils: in situ measurements and modelling

Soil Research ◽  
2004 ◽  
Vol 42 (6) ◽  
pp. 499 ◽  
Author(s):  
F. J. Cook ◽  
S. K. Dobos ◽  
G. D. Carlin ◽  
G. E. Millar
Keyword(s):  
Oxidation Rate ◽  
Volume Ratio ◽  
Soil Surface ◽  
Biological Processes ◽  
Acid Sulfate Soils ◽  
Acid Sulfate ◽  
The Difference ◽  
Actual Acidity ◽  
Sulfate Soils

The generation of acidity from oxidation of pyrite in acid sulfate soils requires the transport of oxygen into the soil profile. The sink for this oxygen will not only be the chemical reaction with pyrite but the biological processes associated with both microbial and plant respiration. The biological sinks in burning the oxygen (O2) will release CO2. The respiratory quotient which is the molar volume ratio of O2 : CO2 varies between 1.3 and 0.7 depending on the source of the organic matter being oxidised, but is generally 1.0. The oxidation of pyrite by oxygen will, by comparison with the biological processes, produce minor amounts of CO2 (if any) by reaction with intrinsic carbonate minerals. Gas samplers were installed into the soil at various depths and samples collected from these at approximately fortnightly intervals. The samples were analysed by gas chromatography and the CO2 and O2 profiles obtained. The flux of these gases was calculated and the difference between these attributed to the oxidation of pyrite. The flux difference varied over the period of sampling and on average gave an in situ oxidation rate of 11.5 tonnes H2SO4/ha.year. This is considerably more that the rate of export of acidity from this site and would explain the considerable actual acidity storage in these soils. A model is developed for steady state transport of oxygen into soils with an exponentially decreasing biological sink with depth and an exponentially increasing chemical (pyrite) sink with depth. The model is developed in non-dimensional variables, which allows the relative strengths and rates of increase or decrease in sink terms to be explored. This model does not explicitly treat the flow of oxygen in macropores. Other models that do explicitly calculate macropore flow are compared and found to give similar results. These results suggest that the use of biological or other sinks near the soil surface could be a useful method for reducing the oxidation rate of pyrite in acid sulfate soils.

Effects of Bauxsol™ on the immobilisation of soluble acid and environmentally significant metals in acid sulfate soils

Soil Research ◽  
2002 ◽  
Vol 40 (5) ◽  
pp. 805 ◽  
Author(s):  
Chuxia Lin ◽  
Malcolm W. Clark ◽  
David M. McConchie ◽  
Graham Lancaster ◽  
Nick Ward
Keyword(s):  
Heavy Metals ◽  
Simulation Experiment ◽  
Acid Sulfate Soils ◽  
Acid Sulfate Soil ◽  
Acid Sulfate ◽  
Metal Hydroxides ◽  
Acid Neutralising Capacity ◽  
Soluble Acid ◽  
Decreasing Ph ◽  
Sulfate Soils

The effects of Bauxsol, an abundant industrial by-product, on the immobilisation of soluble acid and a range of potentially environmentally toxic metals in artificial and natural acid sulfate soils were investigated. The acid neutralising capacity of Bauxsol increased with decreasing pH, which is probably provided not only by basic metal hydroxides, carbonates, and hydroxycarbonates but also by protonation of variably charged particles (e.g. gibbsite and hematite) present in Bauxsol. Simulation experiment results show that the removal of 9 tested environmentally significant heavy metals can be enhanced by addition of BauxsolTM; an exception was Co. The removal of the added soluble heavy metals by the BauxsolTM-soil mixtures shows a preferential order of Pb > Fe > Cr > Cu > Zn > Ni > Cd > Co > Mn. For the natural acid sulfate soil without added synthesised metal solution, the retention of the investigated environmentally significant metals is in the following decreasing order : Al > Zn > Fe > Co > Mn.

Climate-driven mobilisation of acid and metals from acid sulfate soils

2010 ◽  
Vol 61 (1) ◽  
pp. 129 ◽  
Author(s):  
Stuart L. Simpson ◽  
Rob W. Fitzpatrick ◽  
Paul Shand ◽  
Brad M. Angel ◽  
David A. Spadaro ◽  
...  
Keyword(s):  
Metal Release ◽  
Acid Sulfate Soils ◽  
Acid Sulfate ◽  
Metal Concentrations ◽  
Australian Water ◽  
Quality Guidelines ◽  
Eastern Australia ◽  
Water Ph ◽  
Co Precipitation ◽  
Sulfate Soils

The recent drought in south-eastern Australia has exposed to air, large areas of acid sulfate soils within the River Murray system. Oxidation of these soils has the potential to release acidity, nutrients and metals. The present study investigated the mobilisation of these substances following the rewetting of dried soils with River Murray water. Trace metal concentrations were at background levels in most soils. During 24-h mobilisation tests, the water pH was effectively buffered to the pH of the soil. The release of nutrients was low. Metal release was rapid and the dissolved concentrations of many metals exceeded the Australian water quality guidelines (WQGs) in most tests. The concentrations of dissolved Al, Cu and Zn were often greater than 100× the WQGs and strong relationships existed between dissolved metal release and soil pH. Attenuation of dissolved metal concentrations through co-precipitation and adsorption to Al and Fe precipitates was an important process during mixing of acidic, metal-rich waters with River Murray water. The study demonstrated that the rewetting of dried acid sulfate soils may release significant quantities of metals and a high level of land and water management is required to counter the effects of such climate change events.

Ultra-fine grinding is not essential for acid sulfate soil tests

Soil Research ◽  
2011 ◽  
Vol 49 (5) ◽  
pp. 439
Author(s):  
David J. Lyons ◽  
Angus E. McElnea ◽  
Niki P. Finch ◽  
Claire Tallis
Keyword(s):  
Chemical Properties ◽  
Test Results ◽  
Acid Sulfate ◽  
Fine Grinding ◽  
Acid Neutralising Capacity ◽  
Significant Difference ◽  
Australian Standard ◽  
Actual Acidity ◽  
Ultra Fine Grinding ◽  
Sulfate Soils

Australian Standard methods for acid sulfate soils (ASS) require the grinding of soil to <0.075 mm. A ring-mill or similar grinding apparatus is therefore needed. We investigated whether ring-mill grinding is required for accurate and reproducible test results and associated calculations (such as acid–base accounting), or if more conventional fine-grinding (i.e. <0.5 mm) is sufficient to obtain acceptable results. An initial experiment (unreplicated) was conducted on 52 soils comparing ring-mill and fine-grinding treatments, and this information was used to formulate final, more detailed experimental work on five soils from the same dataset. Soils from an ASS survey in coastal central Queensland were chosen to reflect the range of chemical properties found in ASS. Soils were analysed by the Chromium and SPOCAS suite of tests for the two grinding treatments. For those tests that follow a relatively vigorous extraction carried out with heating [such as chromium-reducible S, peroxide-oxidisable S and acid-neutralising capacity by back titration (ANCBT)], results were similar for the two grinding treatments. However, for those tests that follow a relatively mild extraction without heating (such as KCl-extractable S, HCl-extractable S and titratable actual acidity), significantly higher values (P < 0.05) were obtained for ring-mill ground soil. There was no significant difference in calculated net acidity between ring-mill grinding and fine-grinding for soils without excess ANC. For self-neutralising soils, fine-grinding gave significantly lower values of ANC than ring-mill grinding. It is uncertain whether ring-mill grinding gives a true reflection of the ANC available in the natural environment.

An improved analytical procedure for determination of total actual acidity (TAA) in acid sulfate soils

2000 ◽  
Vol 262 (1-2) ◽  
pp. 57-61 ◽  
Author(s):  
C. Lin ◽  
K. O’Brien ◽  
G. Lancaster ◽  
L.A. Sullivan ◽  
D. McConchie
Keyword(s):  
Analytical Procedure ◽  
Acid Sulfate Soils ◽  
Acid Sulfate ◽  
Actual Acidity ◽  
Sulfate Soils

Acidity fractions in acid sulfate soils and sediments: contributions of schwertmannite and jarosite

Soil Research ◽  
2013 ◽  
Vol 51 (3) ◽  
pp. 203 ◽  
Author(s):  
Chamindra L. Vithana ◽  
Leigh A. Sullivan ◽  
Richard T. Bush ◽  
Edward D. Burton
Keyword(s):  
Correction Factor ◽  
Soil Samples ◽  
Acid Sulfate Soils ◽  
Peroxide Oxidation ◽  
Acid Base ◽  
Acid Sulfate ◽  
Soils And Sediments ◽  
Actual Acidity ◽  
Sulfate Soils

In Australia, the assessment of acidity hazard in acid sulfate soils requires the estimation of operationally defined acidity fractions such as actual acidity, potential sulfidic acidity, and retained acidity. Acid–base accounting approaches in Australia use these acidity fractions to estimate the net acidity of acid sulfate soils materials. Retained acidity is the acidity stored in the secondary Fe/Al hydroxy sulfate minerals, such as jarosite, natrojarosite, schwertmannite, and basaluminite. Retained acidity is usually measured as either net acid-soluble sulfur (SNAS) or residual acid soluble sulfur (SRAS). In the present study, contributions of schwertmannite and jarosite to the retained acidity, actual acidity, and potential sulfidic acidity fractions were systematically evaluated using SNAS and SRAS techniques. The data show that schwertmannite contributed considerably to the actual acidity fraction and that it does not contribute solely to the retained acidity fraction as has been previously conceptualised. As a consequence, SNAS values greatly underestimated the schwertmannite content. For soil samples in which jarosite is the only mineral present, a better estimate of the added jarosite content can be obtained by using a correction factor of 2 to SNAS values to account for the observed 50–60% recovery. Further work on a broader range of jarosite samples is needed to determine whether this correction factor has broad applicability. The SRAS was unable to reliably quantify either the schwertmannite or the jarosite content and, therefore, is not suitable for quantification of the retained acidity fraction. Potential sulfidic acidity in acid sulfate soils is conceptually derived from reduced inorganic sulfur minerals and has been estimated by the peroxide oxidation approach, which is used to derive the SRAS values. However, both schwertmannite and jarosite contributed to the peroxide-oxidisable sulfur fraction, implying a major potential interference by those two minerals to the determination of potential sulfidic acidity in acid sulfate soils through the peroxide oxidation approach.

Discharge of weathering products from acid sulfate soils after a rainfall event, Tweed River, eastern Australia

2007 ◽  
Vol 22 (12) ◽  
pp. 2695-2705 ◽  
Author(s):  
B.C.T. Macdonald ◽  
I. White ◽  
M.E. Åström ◽  
A.F. Keene ◽  
M.D. Melville ◽  
...  
Keyword(s):  
Rainfall Event ◽  
Acid Sulfate Soils ◽  
Acid Sulfate ◽  
Eastern Australia ◽  
Sulfate Soils
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