Mechanisms for high Cd activity in a red soil from southern China undergoing gradual reduction

Soil Research ◽  
2010 ◽  
Vol 48 (4) ◽  
pp. 371 ◽  
Author(s):  
Yichun Li ◽  
Ying Ge ◽  
Chunhua Zhang ◽  
Quansuo Zhou
Keyword(s):  
Soil Solution ◽  
Southern China ◽  
Soil Surface ◽  
Red Soil ◽  
Soil Suspension ◽  
Surface Sites ◽  
Mn Oxide ◽  
Exchangeable Fraction ◽  
Close Relationship ◽  
Solid Phases

Cadmium (Cd) activity may vary in flooded soils but the mechanisms underlying these variations have remained conflicting and ambiguous. In this study, a continuous N2 bubbling experiment was conducted using a red soil from the subtropical region of southern China to identify factors controlling Cd activity under reductive conditions. The results showed that Cd solubility, although very low, increased gradually with time during the experiment. From 0 to 14 h, the pH and pe+pH of soil suspension decreased, respectively, from 5.6 to 5.5 and from 11.1 to 9.6. The solubility of Cd was enhanced within this period due to the kinetics of solubilisation of salts or dispersion of colloids upon rewetting, the pH decrease resulting from the hydrolysis of soluble Al and Fe(III) and the competition for soil surface sites from dissolved organic carbon (DOC) and cations, including Al3+, K+, and Mg2+ in the soil solution. From 14 to 114 h, however, the reductive dissolution of Fe and Mn oxides, the DOC consumption by microbial respiration, and the competition of Cd2+ with K+ and Mg2+ for the soil surface sites were the major mechanisms promoting the release of Cd into the soil solution, as the pH of soil suspension increased from 5.5 to 5.8 and the pe+pH continued to decrease from 9.6 to 7.5. On the other hand, more than half of the total Cd was present in the exchangeable fraction during the experiment, indicating that Cd activity remained high. Further, it was observed that Cd transformed from the Fe-Mn oxide-bound fraction to the carbonate-bound fraction and Fe from the oxide- and carbonate-bound fractions to the exchangeable fraction during the experiment. Cadmium redistribution had a close relationship with Fe redistribution, suggesting that the chemical behaviours of Fe oxides affected the physicochemical properties of soil solid phases and further controlled Cd redistribution among soil solid phases. The above results implied that the mechanisms controlling the solubility of Cd were different within the different ranges of pH and pe+pH after rewetting of the air-dried soil, and Fe chemistry might be an important factor inducing the transformation of Cd among several soil solid phases when soil became reducing.

COMPARISON OF EXCHANGEABLE Al, EXTRACTABLE Al, AND Al IN SOIL FRACTIONS

1990 ◽  
Vol 70 (3) ◽  
pp. 263-275 ◽  
Author(s):  
L. M. SHUMAN
Keyword(s):  
Soil Solution ◽  
Organic Fraction ◽  
Soil Fractions ◽  
Mn Oxide ◽  
Soil Aluminum ◽  
Exchangeable Al ◽  
Exchangeable Fraction ◽  
Exchangeable Aluminum ◽  
Extractable Al ◽  
Al Oxide

Previous results indicated that the activity of Al3+ in soil solution, Al saturation of the CEC, and 0.01 M CaCl2-extractable Al were related to plant growth. Exchangeable Al values determined by 1 M KCl and 1 M NH4Cl, extractable Al values determined by 1 M NH4OAc, pH 4.8, 0.01 M CaCl2, 0.5 M CuCl2, 0.33 M LaCl3, and 0.005 M NTA, were compared with each other and to the activity of Al3+ in soil solution as well as Al in soil fractions. Aluminum in fractions was measured to determine the forms solubilized by the extradants. The fractions extracted were exchangeable [M Mg(NO3)2], organic bound, Mn oxide, amorphous Fe and Al oxide, and crystalline Fe and Al oxide. The order of Al extracted was CuCl2 > NH4OAc, [Formula: see text]. One M KCl and NH4Cl, and CuCl2, LaCl3, NTA, and NH4OAc, pH 4.8, gave similar relative Al values, especially for topsoils, and were not correlated with CaCl2-Al values. The exchangeable fraction Al [M Mg(NO3)2] was well correlated with the activity of Al3+ in the soil solution and Al saturation of the CEC. Organic fraction Al was negatively correlated with the activity of Al3+ in the soil solution indicating that organic matter can bind Al lowering its concentration in the soil solution. Aluminum in the crystalline Fe/Al oxide fraction correlated well with that extracted by CuCl2, LaCl3, NTA, and NH4OAc, pH 4.8, leading to the possible conclusion that these extradants solubilize Al from plant-unavailable fractions. Key words: Soil aluminum, aluminum extractants, aluminum fractions, exchangeable aluminum

scholarly journals Micro-Water Harvesting and Soil Amendment Increase Grain Yields of Barley on a Heavy-Textured Alkaline Sodic Soil in a Rainfed Mediterranean Environment

Agronomy ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 713
Author(s):  
Edward G. Barrett-Lennard ◽  
Rushna Munir ◽  
Dana Mulvany ◽  
Laine Williamson ◽  
Glen Riethmuller ◽  
...  
Keyword(s):  
Soil Solution ◽  
Elemental Sulfur ◽  
Root Zone ◽  
Soil Surface ◽  
Conventional Tillage ◽  
Barley Grain ◽  
Control Treatment ◽  
Water Harvesting ◽  
Hordeum Vulgare L ◽  
Salt Leaching

This paper focuses on the adverse effects of soil sodicity and alkalinity on the growth of barley (Hordeum vulgare L.) in a rainfed environment in south-western Australia. These conditions cause the accumulation of salt (called ‘transient salinity’) in the root zone, which decreases the solute potential of the soil solution, particularly at the end of the growing season as the soil dries. We hypothesized that two approaches could help overcome this stress: (a) improved micro-water harvesting at the soil surface, which would help maintain soil hydration, decreasing the salinity of the soil solution, and (b) soil amelioration using small amounts of gypsum, elemental sulfur or gypsum plus elemental sulfur, which would ensure greater salt leaching. In our experiments, improved micro-water harvesting was achieved using a tillage technique consisting of exaggerated mounds between furrows and the covering of these mounds with plastic sheeting. The combination of the mounds and the application of a low rate of gypsum in the furrow (50 kg ha−1) increased yields of barley grain by 70% in 2019 and by 57% in 2020, relative to a control treatment with conventional tillage, no plastic sheeting and no amendment. These increases in yield were related to changes in ion concentrations in the soil and to changes in apparent electrical conductivity measured with the EM38.

scholarly journals Identifying Human-Induced Spatial Differences of Soil Erosion Change in a Hilly Red Soil Region of Southern China

2019 ◽  
Vol 11 (11) ◽  
pp. 3103
Author(s):  
Dong Huang ◽  
Xiaohuan Yang ◽  
Hongyan Cai ◽  
Zuolin Xiao ◽  
Dongrui Han
Keyword(s):  
Soil Erosion ◽  
Human Impact ◽  
Human Impacts ◽  
Southern China ◽  
Red Soil ◽  
Jiangxi Province ◽  
Negative Effects ◽  
Gravity Center ◽  
Local Conditions ◽  
Spatial Differences

Soil erosion (SE) processes are closely related to natural conditions and human activities, posing a threat to environment and society. Identifying the human impact on regional SE changes is increasingly essential for pertinent SE management. Jiangxi province is studied here as a representative area of hilly-red-soil regions within southern China. The main objectives of this study were to investigate the changing trend of SE within Jiangxi and identify human impacts on regional SE change from the perspective of spatial differences, through a new approach based on a gravity-center model. Our results showed that SE status presented an overall amelioration from 1990 to 2015, while the average soil erosion modulus (SEM) declined from 864 to 281 Mg/(km2·a). Compared to the situation under human and natural impacts, human-induced spatial differences of SE change demonstrated that the western and northwest regions showed stronger negative effects; the southern region shifted towards negative effects; the northeast region presented a much weaker negative effect. Our results indicated that 4 cities with strong negative effects need more attention in further SE management suited to their local conditions and development, and also suggested that the approach based on a gravity-center has potential for identifying the human impact on regional SE change from the perspective of spatial patterns.

Amelioration of subsurface acidity in sandy soils in low rainfall regions .2. Changes to soil solution composition following the surface application of gypsum and lime

Soil Research ◽  
1994 ◽  
Vol 32 (4) ◽  
pp. 847 ◽  
Author(s):  
CDA Mclay ◽  
GSP Ritchie ◽  
WM Porter ◽  
A Cruse
Keyword(s):  
Ionic Strength ◽  
Soil Solution ◽  
Ion Pairs ◽  
Chemical Properties ◽  
Sandy Soils ◽  
Soil Surface ◽  
Field Trials ◽  
Annual Rainfall ◽  
First Year ◽  
Solution Composition

Two field trials were sampled to investigate the changes to soil solution chemical properties of a yellow sandplain soil with an acidic subsoil following the application of gypsum and lime to the soil surface in 1989. The soils were sandy textured and located in a region of low annual rainfall (300-350 mm). Soil was sampled annually to a depth of 1 m and changes in soil solution composition were estimated by extraction of the soil with 0.005 M KCl. Gypsum leaching caused calcium (Ca), sulfate (SO4) and the ionic strength to increase substantially in both topsoil and subsoil by the end of the first year. Continued leaching in the second year caused these properties to decrease by approximately one-half in the topsoil. Gypsum appeared to have minimal effect on pH or total Al (Al-T), although the amount of Al present as toxic monomeric Al decreased and the amount present as non-toxic AlSO+4 ion pairs increased. Magnesium (Mg) was displaced from the topsoil by gypsum and leached to a lower depth in the subsoil. In contrast, lime caused pH to increase and Al to decrease substantially in the topsoil, but relatively little change to any soil solution properties was observed in the subsoil. There was an indication that more lime may have leached in the presence of gypsum in the first year after application at one site. Wheat yields were best related to the soil acidity index Al-T/EC (where EC is electrical conductivity of a 1:5 soil:water extract), although the depth at which the relationship was strongest in the subsoil varied between sites. The ratio Al-T/EC was strongly correlated with the activity of monomeric Al species (i.e. the sum of the activities of Al3+, AlOH2+ and Al(OH)+2 in the soil solution. An increase in the concentration of sulfate in the subsoil solution (which increased the ionic strength, thereby decreasing the activity of Al3+, and also increased the amount of Al present as the AlSO+4 ion pair) was probably the most important factor decreasing Al toxicity to wheat. The results indicated that gypsum could be used to increase wheat growth in aluminium toxic subsoils in sandy soils of low rainfall regions and that a simple soil test could be used to predict responses.

scholarly journals IMMOBILIZATION OF EXCHANGEABLE CROMIUM IN A CONTAMINATED SOIL USING NATURAL ZEOLITE AS AN EFFECTIVE ADSORBENT

2020 ◽  
Vol 58 (5A) ◽  
pp. 10
Author(s):  
Van Minh Dang ◽  
Huu Tap Van ◽  
Thi Bich Hanh Nguyen ◽  
Dinh Vinh Nguyen ◽  
Thị Tuyet Nguyen ◽  
...  
Keyword(s):  
Soil Ph ◽  
Contaminated Soil ◽  
Contaminated Soils ◽  
Natural Zeolite ◽  
Organic Matters ◽  
Amended Soils ◽  
Mn Oxide ◽  
Content Ratio ◽  
Incubation Experiments ◽  
Exchangeable Fraction

This work investigated the effects of soil pH and the content ratio of natural zeolite on Cr contaminated soil. The immobilization experiments of the exchangeable Cr in contaminated soils were conducted using the batch method. The incubation experiments were carried out over 30 days in plastic bottles to determine five fraction of Cr existence (exchangeable fraction (F1), Fe/Mn/Oxide (F2), carbonate bound (F3), organic matters (F4) and residual (F5)) in amended soils after incubation. Results showed that the content and proportion of the exchangeable Cr decreased with an increase in soil pH from 5 to 9. At soil pH 5, the exchangeable Cr in soil reduced from 44.80±0.772 mg/kg (initial soil) to 17.72±0.300 mg/kg after 30 days of incubation with natural Zeolite 3%. Meanwhile, the exchangeable Cr of soil also decreased with increasing the content ratio of natural zeolite from 1% to 5% in soil. The ratio of 3% was suitable for incubation of the exchangeable Cr in contaminated soil with natural zeolite. The exchangeable Cr in contaminated soil decreased from 80.34% at un-amended soil treatment to 25.06% after incubation of 30 days. The forms of carbonate bound (F3) and organic matters (F4) in amended soils increased to 36.54% and 28% compared with 4.26% and 6.90% in un-amended contaminated soil. Ion exchange, precipitation and adsorption on the surface of natural zeolite  might be the potential mechanisms of immobilization of the exchangeable Cr. The results indicated that natural zeolite can be used as the effective adsorbent for immobilizing the exchangeable Cr in contaminated soils and leading to a decrease in the environmental risk from Cr toxicity.

scholarly journals Effects of Land Use and Slope Gradient on Soil Erosion in a Red Soil Hilly Watershed of Southern China

2015 ◽  
Vol 7 (10) ◽  
pp. 14309-14325 ◽  
Author(s):  
Zhanyu Zhang ◽  
Liting Sheng ◽  
Jie Yang ◽  
Xiao-An Chen ◽  
Lili Kong ◽  
...  
Keyword(s):  
Land Use ◽  
Soil Erosion ◽  
Southern China ◽  
Red Soil ◽  
Slope Gradient ◽  
Hilly Watershed ◽  
Effects Of Land Use

Effects of stand age on soil respiration in Pinus massoniana plantations in the hilly red soil region of Southern China

CATENA ◽  
2019 ◽  
Vol 178 ◽  
pp. 313-321 ◽  
Author(s):  
Kunyong Yu ◽  
Xiong Yao ◽  
Yangbo Deng ◽  
Zhuangjie Lai ◽  
Lingchen Lin ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Southern China ◽  
Pinus Massoniana ◽  
Red Soil ◽  
Stand Age ◽  
Hilly Red Soil Region
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