China
Africa
Explore chapters and articles related to this topic
Effects of Biochars on Sorption and Desorption of Herbicides in Soil
Published in Kassio Ferreira Mendes, Interactions of Biochar and Herbicides in the Environment, 2022
Kamila Cabral Mielke, Kassio Ferreira Mendes, Tiago Guimarães
CEC is an indirect measure of the ability of soils to retain and exchange nutrients. The acidic aromatic carbon on the biochar surface is oxidized to form abundant functional groups (-OH, -COOH), increasing the cation adsorption capacity of the soil (Atkinson et al. 2010). Even the addition of a small amount of biochar can increase the content of cations and alkali nutrients in the soil (Hossain et al. 2010). Soils amended with biochar increased CEC by 4% to 30%, as compared to unamended soils (Laird et al. 2010). The CEC of a weathered soil increased from 7.41 to 10.8 cmol kg-1 after being amended with Leucaena leucocephala biochar (Jien and Wang 2013). The addition of biochar to highly organic soils may not improve the CEC of the soil due to the high organic matter contents they already have and consequently a high CEC (Schulz and Glaser 2012).
Soil Chemical Properties
Published in L.B. (Bert) McCarty, Golf Turf Management, 2018
The CEC of many soils also is pH dependent. With organic matter, most CEC sites are pH dependent with a 10% to 30% increase in CEC per pH unit. Maintaining a pH between 5.5 and 6.5 is the first step to increase CEC values in sandy soils. Adding organic matter or inorganic amendment prior to construction or by topdressing following establishment would be the next most efficient means of increasing sandy soil CEC values (Figure 3.6). Increasing CEC by adding clay or organic matter to soil, however, is difficult due to the large amount of material needed. For example, to increase the CEC of a soil 1 meq/100 g, it is necessary to increase the soil content of clay or organic matter by 10 tons/acre (22,417 kg/ha) of soil (assuming a CEC of 100 meq/100 g for the clay or organic matter and incorporation 6 inches, 15 cm, deep). Adding this much material would increase the clay or organic matter content of the soil 1%. In general, organic matter has a greater potential to increase CEC than clay. For example, a 5% content of organic matter by weight equals the CEC provided by a 30% content of an illitic clay. Although additions of clay and organic matter may increase the CEC of sandy soils, excessive increases in these materials may adversely affect the soil’s physical properties such as infiltration and percolation rate.
Sewage sludge disposal on land – impacts on soils and groundwater quality
Published in R. Hranova, Diffuse Pollution of Water Resources, 2005
Chemicals and pollutant constituents exist in soils in different phases: solid, liquid or gaseous. Constituents in solid phase are associated with soil particles – adsorbed on their surfaces or precipitated in different forms and chemical complexes. Liquid constituents are dissolved in water or soil moisture. Gaseous fractions may result as the product of chemical or biological processes. In general, only the constituents in the solid phase are immobilized in the soils and are non-available for biological degradation by microorganisms or plant uptake. The parameters, which characterize the soil capacity to immobilize pollutants, also known as “capacity controlling parameters” are OC and the CEC. OC represents the organic material in soils, which has a strong binding capacity, while CEC is dependent on the surface area and the nature of soil particles. The smallest particles, typical for clay soils, have the highest adsorbing capacity. CEC is also associated with soils’ permeability, and represents the capacity of soil to retain its structure.
Biochar application on heavy metal immobilization in unsaturated soil with vegetation: a review
Published in International Journal of Geotechnical Engineering, 2023
The electrostatic interactions between surface charges of biochar and heavy metals are also an effective method to remediate heavy metals in contaminated soil, which mainly depends on CEC of soil. CEC is a measurement of the negative charge to evaluate the ability of material to neutralize the exchangeable cations like heavy metal ions and also improve the soil capacity to hold nutrients (Mukherjee, Zimmerman, and Harris 2011). Biochar can elevate CEC of soil resulting from increases in charge density in the given surface of organic matter, which is similar as a greater degree of oxidation or larger surface area for cation adsorption (Liang et al. 2006). Chintala et al. (2013) showed that the CEC of bare soil was about 7.86 cmol kg−1, while the CEC of biochar-amended soil was 14.71 cmol kg−1 (52 Mg ha−1 biochar) and 17.33 cmol kg−1 (104 Mg ha−1 biochar). Heavy metals were adsorbed by biochar due to the electrostatic interactions between positive metals and negative functional groups (-COO−, etc) of biochar (Qiu et al. 2008).
Ecological and Human Health Risk Assessment of Sediments near to Industrialized Areas along Langat River, Selangor, Malaysia
Published in Soil and Sediment Contamination: An International Journal, 2021
Jia Xin Ng, Rosazlin Abdullah, Sharifah Norkhadijah Syed Ismail, Mohammed ELTurk
The sediment CEC ranged from 7.36 Cmol./kg to 13.93 Cmol./kg. CEC measures the amount of sites on soil surfaces that can retain positively charged ions by electrostatic forces and these cations are easily exchangeable with other cations in the soil solution and are thus readily available to be uptake by plants and benthic animals (Yuswir et al. 2015). A study conducted at the river Scheldt estuary (Belgium) concluded that CEC is one of the important factors that determine the bioavailability of heavy metals in intertidal sediment (Du Laing et al. 2002). Major bases such as Na, K, Mg and Ca compete with heavy metals for the sorption site on the surface of clay and organic matter (Tam and Wong 1999). S1 which recorded for the highest K⁺ and Na⁺ concentration had measured for below mean concentration of Cd, Cr and Pb.
Effect of Compost and Biochar on Heavy Metals Phytostabilization by the Halophytic Plant Old Man Saltbush [Atriplex Nummularia Lindl]
Published in Soil and Sediment Contamination: An International Journal, 2019
A soil sample (0–30 cm) was collected from Illwan, Assiut, Egypt where the soils have been irrigated with sewage waste water for more than 50 years. Table 1 shows some physiochemical properties of the studied soil. The collected soil sample was air dried and sieved to pass through a 2 mm sieve. Pipette method was used to determine the soil texture (Burt, 2004). A digital pH meter was used to measure the soil pH in a 1:2 (soil to water) suspension. Organic matter content was determined using the dichromate oxidation method as described by Walkley and Black (Burt, 2004). Total carbonates were measured by Collins calcimeter and expressed as CaCO3 (Burt, 2004). The electrical conductivity (EC) was estimated in 1:2 soil to water extract using the salt bridge method (Burt, 2004). Total nitrogen was determined by micro-kjeldahl method (Burt, 2004). 0.005 M diethylene triamine penta acetic acid (DTPA) solution buffered at pH 7.3 was used to extract the available Zn, Cu, Cd, and Pb from the soil samples (Lindsay and Norvell, 1969). The digestion of soil samples was made by a mixture of HF–HNO3–HClO4 (1:1:1, v/v) to extract the total soil Zn, Cu, Cd, and Pb. The CEC was measured using the ammonium acetate (pH = 7) method (Burt, 2004).