Exchange and solution phase chemistry of acid, highly weathered soils .I. Investigation of mechanisms controlling Al release into solution

Soil Research ◽  
1994 ◽  
Vol 32 (2) ◽  
pp. 269 ◽  
Author(s):  
NW Menzies ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Soil Solution ◽  
Solid Phase ◽  
Solution Phase ◽  
Strongly Correlated ◽  
Solution Ph ◽  
Surface Soils ◽  
Weathered Soils ◽  
Highly Weathered Soils ◽  
Phase Chemistry ◽  
Soil Solid Phase

Soil solid phase and soil solution characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on a subset of 39 surface horizons following the addition of CaSO4.2H2O. The activity of Al3+ Was found to be strongly correlated with the soil solution pH, with Al3+ activity increasing as pH decreased. For surface soils in the unamended state, and for the majority of subsoils, the Al3+ activity calculated was comparable to the theoretical activity supported by the dissolution of gibbsite (Al2O3.3H2O). The Al3+ activity in CaSO4.2H2O-amended samples tended to fall below that maintained by gibbsite dissolution and was more closely correlated with the Al3+ activity supported by the dissolution of jurbanite (AlSO4 (OH).5H2O).

Exchange and solution phase chemistry of acid, highly weathered soils .I. Characteristics of soils and the effects of lime and gypsum amendments

Soil Research ◽  
1994 ◽  
Vol 32 (2) ◽  
pp. 251 ◽  
Author(s):  
NW Menzies ◽  
LC Bell ◽  
DG Edwards
Keyword(s):  
Soil Solution ◽  
Exchange Capacity ◽  
Solution Phase ◽  
Exchangeable Cation ◽  
Solution Ph ◽  
Ph Change ◽  
Median Concentration ◽  
Surface Samples ◽  
Weathered Soils ◽  
Highly Weathered Soils

Exchange and solution phase characteristics were evaluated on surface and subsoil horizons of 60 acid, highly weathered soils in the unamended state, and on 39 of the surface horizons following addition of CaCO3 or CaSO4.2H2O. Soil solutions from unamended surface samples were dominated by Na (median concentration 0.65 mM), while the other major cations were present at lower levels (median concentrations: Ca, 0.09; Mg, 0.14; K, 0.28 mM). This pattern was more pronounced in the subsoil samples where the median concentrations of the nutrient cations were < 0.05 mM, whereas the median concentration of Na was 0.28 mM. The cation exchange capacity of surface samples was dominated by Ca, Mg and Al, while Al was the major exchangeable cation in the subsoil. Addition Of CaSO4.2H2O decreased soil solution pH and increased electrical conductivity and the concentration of Ca, Mg, Na, K and Al in the soil solution. The soil solution pH change resulting from CaSO4.2H2O addition could not be predicted on the basis of the characteristics of the soil in the unamended state.

Effects of calcium and aluminum in the soil solution of acid, surface soils on root elongation of mungbean

Soil Research ◽  
1994 ◽  
Vol 32 (4) ◽  
pp. 721 ◽  
Author(s):  
NW Menzies ◽  
DG Edwards ◽  
LC Bell
Keyword(s):  
Root Growth ◽  
Soil Solution ◽  
Root Length ◽  
Solid Phase ◽  
Ion Pairs ◽  
Exchange Capacity ◽  
Strongly Correlated ◽  
Surface Soils ◽  
Relative Root Length ◽  
Relative Root

Short term root growth bioassays using mungbean (Vigna radiata (L.) Wilczek) were conducted on 39 surface soils in the unamended state and following the addition of CaCO3 or CaSO4.2H2O. Root length after 48 h growth was related to solid phase and soil solution Ca and Al attributes. Suitable diagnostic indices for the prediction of Ca limitations to root growth were either Ca saturation of the cation exchange capacity or Ca activity ratio (CAR) defined as the ratio of the activity of ca2+ in the soil solution to the summed activities of Ca2+, Mg2+, Na+, K+ and Al3+. Values corresponding to 90% relative root length were 34% for Ca saturation and 0.10 for CAR. The activities of Al3+ and AlOH2+ were the Al attributes most strongly correlated with root growth; an Al3+ activity of 1.9 �m~ and an AlOH2+ activity of 0.46 �m corresponded to 90% relative root length. The results suggest that organically complexed Al and the ion pairs Al(OH)+2, Al(OH)04 and AlSO+4 are not plant-toxic. The most effective diagnostic criterion for A1 toxicity in this study was the calcium-aluminium balance (CAB), defined as 2 log(Ca2+) - 6 log(Al3+). The CAB value corresponding to 90% relative root length was 31. The correlation between root growth and CAB was further improved by inclusion of a pH term; this may indicate toxic effects of H+ per se.

Dissolution behaviour of soil kaolinites in acidic solutions

Clay Minerals ◽  
2013 ◽  
Vol 48 (3) ◽  
pp. 447-461 ◽  
Author(s):  
K. Khawmee ◽  
A. Suddhiprakarn ◽  
I. Kheoruenromne ◽  
I. Bibi ◽  
B. Singh
Keyword(s):  
Steady State ◽  
Dissolution Rate ◽  
Initial Period ◽  
Reference Sample ◽  
Stoichiometric Ratio ◽  
Solution Ph ◽  
Weathered Soils ◽  
Dissolution Behaviour ◽  
Georgia Kaolinite ◽  
Highly Weathered Soils

AbstractHighly weathered soils of the tropics and subtropics commonly have kaolinitedominated clay fractions. Under acidic conditions prevailing in these soils kaolinite dissolution occurs, contributing to the high levels of soluble Al in these soils. This study evaluates the dissolution behaviour of kaolinites from subsurface horizons of highly weathered soils from Thailand, along with a soil kaolinite from Western Australia (WA kaolinite) and Georgia kaolinite (KGa-2). Kaolinite-dominated clay fractions were isolated from soils by sedimentation and chemically treated to remove iron oxides. The dissolution rate of kaolinites was measured in 0.01 M NaCl as a function of pH (1–4; HCl) at 25±1°C using non-stirred flow-through reactors. Kaolinite dissolution rates were calculated from the release of Al and Si at the steady state. In most of the experiments and at all pH values, the release of both Si and Al underwent a distinct transition from an initial period of rapid release to significantly slower release at the steady state. Aluminium and Si concentrations at the steady state were higher for soil kaolinites than the reference sample (KGa-2). At the steady state the dissolution of all kaolinites was stoichiometric except for the soil kaolinites from Thailand at pH 4, where the Al/Si ratio was well below the stoichiometric ratio. Log dissolution rate (RSi) of soil kaolinites ranged from –13.75 to –12.51, with the dissolution rate increasing significantly with decreasing solution pH. However, the dissolution rate was similar or pH independent between pH 2 and 3, which is the pH range of the point of zero net charge (PZNC) for both soil and reference kaolinites. The dissolution rate of soil kaolinite was significantly higher than the KGa-2 sample at pH < 3. The results obtained on kaolinite samples from highly weathered soils show that in highly acidic systems kaolinite is a source of soluble Al. Soil kaolinites with poorly ordered small crystals dissolve faster than better crystalline reference kaolinite (KGa-2) with larger crystals.

Solid Phase Speciation and Solubility of Vanadium in Highly Weathered Soils

2017 ◽  
Vol 51 (15) ◽  
pp. 8254-8262 ◽  
Author(s):  
Worachart Wisawapipat ◽  
Ruben Kretzschmar
Keyword(s):  
Solid Phase ◽  
Weathered Soils ◽  
Highly Weathered Soils

Control of lead solubility in soil contaminated with lead shot: effect of soil moisture and temperature

Soil Research ◽  
2009 ◽  
Vol 47 (3) ◽  
pp. 296 ◽  
Author(s):  
R. G. McLaren ◽  
C. P. Rooney ◽  
L. M. Condron
Keyword(s):  
Soil Moisture ◽  
Soil Solution ◽  
Solid Phase ◽  
Temperature Limit ◽  
Soil Environment ◽  
Solution System ◽  
Organic C ◽  
Temperature Regimes ◽  
Almost All ◽  
Soil Solid Phase

An incubation experiment was carried out to assess the rate of oxidation of lead (Pb) shot and subsequent transfer of Pb to the soil under different soil moisture and temperature regimes. Lead was readily released from Pb shot into the soil environment due to rapid corrosion of the Pb shot; however, the rate of Pb shot dissolution was slower at 70% than at 100% field moisture capacity. The corrosion and development of crust material on Pb shot, and corresponding increases in soil solution Pb and Pb associated with the soil solid phase, were also slower at 10°C than 25 or 30°C. Soil moisture and temperature also influenced the speciation of soil solution Pb as modelled using WHAM 6, mainly through the effects of moisture and temperature on soil pH, total soluble Pb, and dissolved organic C. The rate of approach to equilibrium of the Pb shot–soil–soil solution system will be much slower where soil moisture and temperature limit Pb shot corrosion. Calculated free ion Pb2+ concentrations suggest that after 6 months, almost all samples contaminated with Pb shot exceeded soil critical limits for Pb toxicity.

Soil Solid-Phase Controls Lead Activity in Soil Solution

2002 ◽  
Vol 31 (1) ◽  
pp. 162 ◽  
Author(s):  
S. H. Badawy ◽  
M. I. D. Helal ◽  
A. M. Chaudri ◽  
K. Lawlor ◽  
S. P. McGrath
Keyword(s):  
Soil Solution ◽  
Solid Phase ◽  
Lead Activity ◽  
Soil Solid Phase

Soil Solid-Phase Controls Lead Activity in Soil Solution

2002 ◽  
Vol 31 (1) ◽  
pp. 162-167 ◽  
Author(s):  
S. H. Badawy ◽  
M. I. D. Helal ◽  
A. M. Chaudri ◽  
K. Lawlor ◽  
S. P. McGrath
Keyword(s):  
Soil Solution ◽  
Solid Phase ◽  
Lead Activity ◽  
Soil Solid Phase
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