Balwant Singh | The University of Sydney (original) (raw)

Papers by Balwant Singh

Frontiers in Environmental Science, 2015

Organo-mineral interactions are important for the cycling and preservation of organic carbon (OC)... more Organo-mineral interactions are important for the cycling and preservation of organic carbon (OC) in soils. To understand the role of soil mineral surfaces in organo-mineral interactions, we used a sequential density fractionation procedure to isolate <1.6, 1.6-1.8, 1.8-2.0, 2.0-2.2, 2.2-2.6, and >2.6 g cm −3 density fractions from topsoils (0-10 cm) of contrasting mineralogies. These soils were under natural vegetation of four major Australian soil types-Chromosol, Ferrosol, Sodosol, and Vertosol. The soils and their organic matter (OM) contents were found to be partitioned in four distinct pools: (i) particulate organic matter 3 <1.6 g cm − ; (ii) phyllosilicate dominant 1.8-2.2 g cm −3 ; (iii) quartz and feldspar dominant 2.6 g cm −3 ; and (iv) Fe oxides dominant 2.0 g cm −3 > > (in the Ferrosol). X-ray photoelectron spectroscopy was used to investigate organic C and N bonding environments associated within each density fraction. Mineral pools were shown to be enriched in distinct organic functional groups: phyllosilicate dominant fractions were enriched with oxidized OC species (C-O, C=O, O=C-O) and protonated amide forms; quartz and feldspar dominated fractions were enriched in aliphatic C and protonated amide forms; Fe oxides dominant fractions had the greatest proportions of oxidized OC species and were low in protonated amide forms. The enrichment of different C species was related to the interaction of functional groups with the mineral surfaces. These results demonstrate the potential of mineral surfaces in influencing the chemical composition of OM bound in surfaces reactions and subsequently the stability of OM in organo-mineral interactions.

Introduction Significant quantities of sulfidic sediments have been reported to have recently acc... more Introduction Significant quantities of sulfidic sediments have been reported to have recently accumulated in inland wetlands of Murray Darling Basin due to a combination of long periods of inundation and the entrance of sulfate-rich water (Fitzpatrick and Shand, 2008). Sulfidic sediments have a capacity to produce copious amount of acidity on exposure to aerobic conditions (Fitzpatrick and Shand, 2008). These processes will cause soil acidification if the buffering capacity of soil is less than the amount of acidity produced. The dissolution of phyllosilicate minerals may occur if soil pH decreased below 4 in acid sulfate soils (ASS). The quantification of the mineral dissolution rates in ASS is imperative to understand the mechanism and parameters controlling the acid neutralization processes and their impact on the soil environment. The aim of this study was to investigate the dissolution behaviour of the clay material from an inland ASS in solutions with the composition similar t...

Liming and mulching are common agricultural management practices. However, there is limited knowl... more Liming and mulching are common agricultural management practices. However, there is limited knowledge on the temperature sensitivity of carbon (C) release in acidic soils amended with lime and mulch. We conducted laboratory incubation experiments for 96 days at 20°± 1 and 40 °C ± 1 using an acidic Chromic Luvisol. The experiments consisted of five treatments viz: soil only (S), soil + lime (S + L), soil + mulch (S + M), soil + mulch + lime (S + M + L) and soil + mulch + 2L (S + M + 2L). Mulch was applied at the rate of 0.5% w/w (M) in the form of sugarcane trash and lime was added at two rates, i.e. 0.46 (L) and 0.92 (2L) % w/w using analytical grade calcium carbonate. The proportions of C released from lime (δ13C of –8.67‰), mulch (–13.02‰) and soil (–25.2‰) were quantified using their distinct δ13C values and a simple linear mixing model. During the 96-day incubation period, in the absence of mulch addition between 64% and 100% of the applied lime C was released as CO2 at both inc...

Hypotheses: 1) rhizosphere effects would enhance lime dissolution and subsequent CO 2 effluxes; a... more Hypotheses: 1) rhizosphere effects would enhance lime dissolution and subsequent CO 2 effluxes; and 2) liming would increase the mobility of dissolved inorganic C (DIC) and dissolved organic C (DOC) in the presence of growing wheat plants. Methodology: Soil sampling & characterization • Subsurface (10–20 cm) sample of a highly acidic (pH 1:5H2O = 5.2) red Kandosol was collected from a long-term acidification field experiment at the Agricultural Institute in Wagga Wagga, NSW. • The soil contained 1.4 % organic C, 72 % sand, 8% silt and 20 % clay. Plant growth • 2.8 kg soil was packed into each PVC column. The following basal nutrients (mg/column), dissolved in water to maintain 60% WHC, were applied to all soil columns: KH 2 PO 4 (1000), (NH 4) 2 SO 4 (215), ZnSO 4 .7H 2 O (18), MnSO 4 ·H 2 O (6), CuCI 2 .2H 2 O (8), H 3 BO 3 (2) and Na 2 MoO 4 ·2H 2 O (1). Initially, nitrogen was applied in the NH 4 form [(NH 4) 2 SO 4 ], while the later additions were in the NO 3 form [Ca(NO 3) 2 a...

While gypsum, and to a lesser extent lime, are reported as ameliorants for soil sodicity, there i... more While gypsum, and to a lesser extent lime, are reported as ameliorants for soil sodicity, there is relatively little information concerning the use of these ameliorants in combination. This study investigates the use of lime and gypsum combinations on selected soil properties relating to sodicity on two different soils used for dryland cropping in the Macquarie Valley of New South Wales (NSW). Lime and gypsum treatments were applied to two soils (lime [L] and/or gypsum [G], applied at t/ha rates: L0G0 [control], L2.5G0, L0G2.5, L2.5G2.5, L2.5G5, L5G2.5, and L5G5) that were sampled after 2.5 years and analysed for soil pH, EC and aggregate stability. Changes in pH and EC, as well as correlations, suggest that lime has dissolved more readily in the presence of gypsum. While aggregate stability was not significantly enhanced, significant relationships between soil EC and aggregate stability were found.

Biochar has gained significant importance due to its ability to increase long-term soil carbon po... more Biochar has gained significant importance due to its ability to increase long-term soil carbon pool and crop productivity. A pot experiment was conducted to investigate the influence of biochar on the availability of arsenic (As) and cadmium (Cd) to maize. An activated wood biochar was applied at three rates (0, 5 and 15 g/kg) in factorial combinations with three rates (0, 10 and 50 mg/kg) each of As and Cd separately to a sandy soil. After 10 weeks of growth, crop was harvested and dry matter yield and concentration of As and Cd were determined. The soil was analysed for extractable trace elements after the plant harvest. The results showed that the addition of wood biochar to soil did not have any significant influence on the dry matter yield of maize shoot, even at the highest application rate. However, application of As and Cd significantly reduced the dry matter yield by 93 and 27%, respectively. Biochar application decreased the concentration of both As and Cd in maize shoots. However, the concentrations of extractable As increased with biochar treatment and the effect of biochar on DTPA extractable Cd in soil was inconsistent. The results show that biochar application can significantly reduce the bioavailability of As and Cd to plants and suggest that biochar application may have potential for remediating contaminated soils.

Soil Research, 2015

Land-use and management practices on limed acidic and carbonate-bearing soils can fundamentally a... more Land-use and management practices on limed acidic and carbonate-bearing soils can fundamentally alter carbon (C) dynamics, creating an important feedback to atmospheric carbon dioxide (CO2) concentrations. Transformation of carbonates in such soils and its implication for C sequestration with climate change are largely unknown and there is much speculation about inorganic C sequestration via bicarbonates. Soil carbonate equilibrium is complicated, and all reactants and reaction products need to be accounted for fully to assess whether specific processes lead to a net removal of atmospheric CO2. Data are scarce on the estimates of CaCO3 stocks and the effect of land-use management practices on these stocks, and there is a lack of understanding on the fate of CO2 released from carbonates. We estimated carbonate stocks from four major soil types in Australia (Calcarosols, Vertosols, Kandosols and Chromosols). In >200-mm rainfall zone, which is important for Australian agriculture, t...

$Research paper thumbnail of Detection of amorphous alumino-silicate by X-ray diffraction and chemical analysis to detect firing in archaeological sediments$

Archaeology in Oceania, 1991

Fire modifies sediments and soil by converting some crystalline clay minerals to amorphous alumin... more Fire modifies sediments and soil by converting some crystalline clay minerals to amorphous alumino-silicate minerals that can be determined using a combination of X-ray diffraction and chemical analysis procedures. Recognition of these materials provides a test for occupation that is independent of, and complementary to, criteria based on the occurrence of cultural or magnetic properties of sediments. This novel procedure has been evaluated for artificial mineral mixtures heated in simulated hearth fires and for Pleistocene and Holocene sediments from caves in the Kimberley Region of Western Australia. An index based on amorphous AI in the samples has been developed to separate heated and unheated samples.

International Journal of Phytoremediation, 2012

In this paper we propose a sender side modification to TCP to accommodate small network buffers. ... more In this paper we propose a sender side modification to TCP to accommodate small network buffers. We exploit the fact that the manner in which network buffers are provisioned is intimately related to the manner in which TCP operates. However, rather than designing buffers to accommodate the TCP AIMD algorithm, as is the traditional approach in network design, we suggest simple modifications to the AIMD algorithm to accommodate buffers of any size in the network. We demonstrate that networks with small buffers can be designed that transport TCP traffic in an efficient manner while retaining fairness and friendliness with standard TCP traffic.

Soil Biology and Biochemistry, 2013

ABSTRACT a b s t r a c t Lime is commonly used to overcome soil acidification in agricultural pro... more ABSTRACT a b s t r a c t Lime is commonly used to overcome soil acidification in agricultural production systems; however, its impact on inorganic and organic soil carbon dynamics remains largely unknown. In a column experi-ment, we monitored rhizosphere effects on lime dissolution, CO 2 effluxes, and the concentrations of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) in leachate from an acidic Kandosol. The experiment consisted of four treatments viz: soil only (control), soil þ lime, soil þ wheat, and soil þ lime þ wheat. We measured CO 2 -C effluxes at 7, 43 and 98 days after planting (DAP) and leachate was collected at 56 and 101 DAP. The soil CO 2 -C efflux rate increased significantly with lime addition at 7 and 43 DAP compared to control. At 43 DAP, the largest increase in CO 2 -C effluxes was observed in the lime þ wheat treatment. However, at 98 DAP similar CO 2 -C effluxes were observed from wheat and lime þ wheat treatments, suggesting that most of the lime was dissolved in the lime þ wheat treatment. Both DOC and DIC concentrations in the leachate increased significantly with lime and wheat only treatments (cf. control). In contrast to DOC, there was an increase in the DIC concentration in the soil leachate from lime þ wheat treatment columns at 101 DAP (significant wheat Â lime interaction), thus, accentuating the pronounced role of wheat roots. We conclude that plant mediated dissolution of lime increased the concentration of DIC in the soil leachate, while both liming and presence of plants enhanced DOC leaching.

smectech.com.au

The prevalence of sulfidic sediments in inland wetlands has been recognized in the last few years... more The prevalence of sulfidic sediments in inland wetlands has been recognized in the last few years in many parts of the world including Australia (Lamontagne et al., 2006). Under conditions of very high salinity, the oxidation of iron sulfide minerals in these sediments ...

Communications in Soil Science and Plant Analysis, 2002

... Titre du document / Document title. Potassium and magnesium in clay minerals of some Brazilia... more ... Titre du document / Document title. Potassium and magnesium in clay minerals of some Brazilian soils as indicated by a sequential extraction procedure. Auteur(s) / Author(s). MELO VF (1) ; SCHAEFER CEGR (2) ; NOVAIS RF (2) ; SINGLY B. (3) ; FONTES MPF (2) ; ...

Soil Systems, 2019

Although association between mineral and biochar carbon have been speculated in some studies, sti... more Although association between mineral and biochar carbon have been speculated in some studies, still there is no direct evidence for the influence of individual clay minerals on the mineralization of biochar carbon in soils. To address this, we conducted an incubation study using monomineralic soils constituted by separately mixing pure minerals, i.e., smectite, kaolinite, and goethite, with a sandy soil. Switch grass biochar (400 °C) was added to the artificial soils and samples were incubated for 90 days at 20 °C in the laboratory. The CO2-C mineralized from the control, and biochar amended soil was captured in NaOH traps and the proportion of C mineralized from biochar was determined using δ13C isotopic analysis. The clay minerals significantly decreased the cumulative total carbon mineralized during the incubation period, whereas biochar had no effect on this. The least amount of total C was mineralized in the presence of goethite and biochar amended soil, where only 0.6% of the ...

Clays and Clay Minerals, Jun 1, 1992

Geoderma, 2014

ABSTRACT Mulch Inorganic and organic carbon Q 10 Acidic soil Lime is commonly applied on agricult... more ABSTRACT Mulch Inorganic and organic carbon Q 10 Acidic soil Lime is commonly applied on agricultural lands for ameliorating soil acidity. However, lime dissolution and its concomitant contribution to carbon dioxide (CO 2) fluxes with the addition of organic residues at varying temper-atures in acidic soils are not well known. We conducted laboratory incubation experiments for 96 days (20 +/− 1 °C and 40 +/− 1 °C) to quantify the priming effects of lime (0.46 and 0.92% w/w) and mulch (0.5% w/w) additions on carbon (C) release in a Chromic Luvisol. The C released from lime (δ 13 C of −8.67‰), mulch (−13.02‰) and soil (−25.2‰) was quantified using their distinct δ 13 C values. Total lime derived C in soils without mulch constituted approximately 32% and 17% of the total C fluxes at 20 °C and 40 °C, respectively. During the 96-day incubation period, in the absence of mulch addition between 64% and 100% of the applied lime C was released as CO 2 at both incubation temperatures. Furthermore, lime derived, mulch derived and soil de-rived C increased by 59, 48 and 284% respectively, when the incubation temperature was increased from 20 °C to 40 °C. These results suggest that mineralization of native soil C was more sensitive to temperature than the C released by lime dissolution and mulch mineralization. Temperature sensitivity of soil derived C was lower in treatments with mulch and lime addition compared to soil without C amendments. We obtained a Q 10 value of 2.41 ± 0.06 for the C released by the lime dissolution in the acidic soil. These findings are important for modelling the contribution of different C sources to atmospheric CO 2 concentrations in soils, such as the acidic limed and mulched soils.

Environmental Science & Technology

Biochar, a form of pyrogenic carbon, can contribute to agricultural and environmental sustainabil... more Biochar, a form of pyrogenic carbon, can contribute to agricultural and environmental sustainability by increasing soil reactivity. In soils, biochar could change its role over time through alterations in its surface chemistry. However, a mechanistic understanding of the aging process and its role in ionic nutrient adsorption and supply remain unclear. Here, we aged a wood biochar (550 °C) by chemical oxidation with 5-15% H2O2 and investigated the changes in surface chemistry and the adsorption behavior of ammonium and phosphate. Oxidation changed the functionality of biochar with the introduction of carboxylic and phenolic groups, a reduction of oxonium groups and the transformation of pyridine to pyridone. After oxidation, the adsorption of ammonium increased while phosphate adsorption decreased. Ammonium adsorption capacity was nonlinearly related to the biochar&amp;amp;amp;amp;amp;#39;s surface charge density (r(2) = 0.94) while electrostatic repulsion and loss of positive charge due to destruction of oxonium and pyridine, possibly caused the reduced phosphate adsorption. However, the oxidized biochar substantially adsorbed both ammonium and phosphate when biochar derived organic matter (BDOM) was included. Our results suggest that aging of biochar could reverse its capacity for the adsorption of cationic and anionic species but the inclusion of BDOM could increase ionic nutrient and contaminant retention.

$Research paper thumbnail of Cd-substituted Goethites - A Structural Investigation by Synchrotron X-ray Diffraction$

Clays and Clay Minerals, 2003

ABSTRACT The structural and physical effects of partially substituting Cd for Fe in goethite have... more ABSTRACT The structural and physical effects of partially substituting Cd for Fe in goethite have been investigated. The solubility of Cd2+ in goethite is ~10 mol.%, i.e. Fe0.905Cd0.095OOH. The structures of the substituted goethites have been refined, using the Rietveld method, from synchrotron X-ray powder diffraction data. There is a progressive increase in the size of the unit-cell parameters and unit-cell volume, upon the incorporation of much larger Cd2+ ion (0.95 Å) compared with Fe3+ (0.645 Å) in the goethite structure, together with a reduction in crystallinity. Transmission electron microscopy measurements confirm the crystallite size decreases as the Cd2+ content increases in goethite structure.