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Reduction in the dissolved phosphorus (P) desorption from agricultural soils could be an effective measure to prevent eutrophication. Lime is a high calcium–containing mineral that can have promising but varying responses on P desorption depending on soil type. The main objective of this research was to evaluate and compare the potential of hydrated lime and lime kiln dust, its cheaper alternative, as soil amendments to increase soil P adsorption capacity and to reduce dissolved P desorption from four soil types (sandy, sandy loam, loam, and clay loam). A batch adsorption study with varying P concentrations of 0, 0.2, 0.4, 0.6. 0.8, and 1.0 mM P and an adsorbent dose of 1% lime by air-dried soil mass at a fixed pH of 6.5 was carried out. The adsorption data fit best the Freundlich adsorption isotherm model. Both hydrated lime and lime kiln dust significantly increased the Freundlich adsorption coefficient by 3.2, 2.4, 2.0, and 1.6 times in loam, sandy, sandy loam, and clay loam soils, respectively. Although the hydrated lime showed a higher potential to increase the Langmuir maximum adsorption capacity in comparison to lime kiln dust, they both exhibited similar performance at lower P concentration ranges that are representative of the soil solution. The cumulative phosphorus desorption in the ten consecutive days agreed with the adsorption results. Therefore, lime kiln dust as a by-product could be a promising soil amendment to increase soil phosphorus adsorption capacity leading to less phosphorus desorption to water bodies. Further studies on its interaction with crop growth at field scale are required.

During the last four decades, tremendous advances have been made towards the understanding of transport characteristics of contaminants in soils, solutes, and tracers in geological media. This book offers a comprehensive treatment of the subject complete with supporting examples of mathematical models that describe contaminants reactivity and transport in soils and aquifers. This approach makes it a practical guide for designing experiments and collecting data that focus on characterizing retention as well as release kinetic reactions in soils and contaminant transport experiments in the laboratory, greenhouse, and in the field.The book provides the basic framework of the principals governing the sorption and transport of chemicalsin soils. It focuses on physical processes such as fractured media, multiregion, multiple porosities, and heterogeneity and effect of scale as well as chemical processes such as nonlinear kinetics, release and desorption hysteresis, multisite and multireaction reactions, and competitive-type reactions.

For effective soil remediation, it is vital to apply environmentally friendly and cost-effective technologies following the notion of green sustainable development. In the context of recycling waste and preserving nutrients in the soil, biochar production and utilization have become widespread. There is an urgent need to develop high-efficiency biochar-based sorbents for pollution removal from soil. This research examined the efficacy of soil remediation using biochar made from three distinct sources: wood, and agricultural residues (sunflower and rice husks). The generated biochars were characterized by SEM/SCEM, XRF, XRD, FTIR, BET Specific Surface Area, and elemental compositions. The presence of hydroxyl and phenolic functional groups and esters in wood, sunflower and rice husk biochar were noted. The total volume of pores was in the following descending order: rice husk > wood > sunflower husk. However, wood biochar had more thermally stable, heterogeneous, irregular-shaped pores than other samples. Adsorption of soil-heavy metals into biochars differed depending on the type of adsorbent, according to data derived from distribution coefficients, sorption degree, Freundlich, and Langmuir adsorption models. The input of biochars to Calcaric Fluvic Arenosol increased its adsorption ability under contamination by Cu(II), Zn(II), and Pb(II) in the following order: wood > rice husk > sunflower husk. The addition of sunflower husk, wood, and rice husk biochar to the soil led to an increase in the removal efficiency of metals in all cases (more than 77%). The increase in the percentage adsorption of Cu and Pb was 9–19%, of Zn was 11–21%. The present results indicated that all biochars functioned well as an absorbent for removing heavy metals from soils. The tailor-made surface chemistry properties and the high sorption efficiency of the biochar from sunflower and rice husks could potentially be used for soil remediation.

Soil phosphorus (P) adsorption and desorption occur in an important endogenous cycle linked with soil fertility problems and relevant to the environmental risk assessment of P. In our study, the effect of long-term inorganic and organic fertilization on P adsorption and desorption characteristics in relation to changes in soil properties was evaluated by selecting three long-term experimental sites in southern China. The selected treatments at each site were CK (unfertilized), NPK (synthetic nitrogen, phosphorus and potassium) and NPKM (synthetic NPK plus manure). The adsorption and desorption characteristics of P were evaluated using Langmuir and Freundlich isotherms. The results showed that long-term application of NPK plus manure significantly increased soil organic carbon (SOC), total P and available P at all three sites compared with the NPK and CK treatments. All three treatments fit these equations well. The maximum adsorption capacity (Q m ) of P increased with NPKM treatment, and the binding energy of P (K) and the maximum buffering capacity (MBC) showed increasing trends. NPKM showed the highest Q m (2346.13 mg kg -1 ) at the Jinxian site, followed by Nanchang (221.16 mg kg -1 ) and Ningxiang (2219.36 mg kg -1 ). Compared to CK and NPK, the NPKM treatment showed a higher MBC as 66.64, 46.93 and 44.39 L kg -1 at all three sites. The maximum desorption capacity (D m ) of P in soil was highest with the NPKM treatment (157.58, 166.76, 143.13 mg kg -1 ), showing a better ability to release P in soil. The correlation matrix showed a significant positive correlation of SOC, total and available P with Q m , D m and MBC. In conclusion, it is suggested that manure addition is crucial to improve P utilization in red paddy soils within the recommended range to avoid the risk of environmental pollution.

With increasing global awareness of soil health, attention must be paid to fluorine exposure in soils, which poses a threat to human health. Therefore, this study aimed to study the fluorine adsorption characteristics of swine manure and straw biochars and their impact on fluorine adsorption-desorption in soil with batch experiments. The biochar samples originated from high-temperature anaerobic cracking of swine manure (350°C, 500°C, and 650°C) and straw (500°C). Results indicated that the adsorption of soil fluorine reached adsorption equilibrium at around 4 h after the mixing of swine manure and straw biochar. Fluorine adsorption kinetics using these biochars conformed to the quasi-two-stage kinetic model. The fluorine adsorption kinetics for biochar-treated soils conformed to the double-constant equation and the Elovich equation, and the soil treated with straw biochar showed the fastest fluorine adsorption rate. The adsorption isotherms of fluorine for biochars and biochar-treated soils could be fitted by the isothermal adsorption model of Langmuir and Freundlich. The maximal equilibrium quantity of fluorine was 73.66 mg/g for swine manure biochar. The soil, adding with 2% of swine manure biochar achieved with showed at 650°C had the smallest adsorption. This study also shows that the adsorption of fluorine by biochar gradually decreased with the increase of pH. Comparing with other factors, the mixture pH with biochars added had a significant effect on fluorine adsorption. The decreased fluorine adsorption capacities for soils treated with swine manure and straw biochars were closely related to the increased pH in soils after adding biochars. Considering the fluorine threat in soil, this study provides a theoretical basis for the application of biochars on soil fluorine adsorption.

The study of competitive adsorption of heavy metals on soil is important for heavy metals contaminated soil remediation. However, there have been few studies on the impact of desorption reagents on heavy metal adsorption in soil. Batch adsorption studies were used to investigate the competitive adsorption mechanism of two heavy metals, Pb and Zn, on a loess soil in the presence of a new chelating surfactant, sodium N-lauroyl ethylenediamine triacetate (LED3A). Results showed that competitive adsorption equilibria of Pb and Zn were reached at 3 and 10 h, respectively. The maximum equilibrium adsorption capacities were 19.55 and 18.35 g.kg-1, respectively. LED3A affected the competitive adsorption kinetics of Pb and Zn by increasing the change in external mass transfer and reducing the change in internal mass transfer. LED3A reduced Pb and Zn adsorption capacities onto the soil through competitive chelation of the heavy metals. The heavy metal chelating ability of LED3A was higher for Zn than for Pb. When its concentration was larger than 5 g.L-1, LED3A showed a significant effect on the competitive adsorption of Pb and Zn. In the competitive system, the effect of Pb concentration on the Zn adsorption capacity was greater than the effect of Zn concentration on the Pb adsorption capacity. LED3A weakened the effect of Pb concentration and enhanced the effect of Zn concentration. LED3A showed a significant potential for efficiently leaching remediation of Pb and Zn co-contaminated soil.

This study investigated the effects of maize (Zea mays L.) straw biochar on phosphorus (P) availability in two soils with different P sorption capacities (iron and aluminum dominated slight acid Red earth and calcium dominated alkaline Fluvo-aquic soil). A 42-day incubation experiment was conducted to study how applications of biochar at different rates (0, 2, 4, and 8 % soil, w/w), in combination with and without mineral KH₂PO₄fertilizer, affected contents of soil Olsen-P and soil microbial biomass P (SMB-P) and phosphomonoesterase activity. In addition, P sorption characteristics of soils amended with biochar, as well as main properties of the biochar and the soils, were determined. Application of 8 % biochar after 42 days of incubation substantially increased soil Olsen-P from 3 to 46 mg kg⁻¹in Red earth and from 13 to 137 mg kg⁻¹in Fluvo-aquic soil and increased SMB-P from 1 to 9 mg kg⁻¹in Red earth and from 9 to 21 mg kg⁻¹in Fluvo-aquic soil. The increase was mainly due to high concentrations of P in the ash fraction (77 % of total biochar P). Biochar effect on soil Olsen-P and SMB-P increased by higher biochar application rates and by lower P sorption capacity. Biochar application significantly reduced acid phosphomonoesterase activity in Red earth and alkaline phosphomonoesterase activity in Fluvo-aquic soil due to large amount of inorganic P added. We conclude that maize straw biochar is promising to potentially improve soil P availability in low-P soils, but further research at field scale is needed to confirm this.

The adsorption and desorption of phosphorus (P) in soil constitute a crucial internal cycle that is closely associated with soil fertility, exerting direct influence on the quantity, form, and availability of P within the soil. The vertical spatial variation characteristics of soil adsorption and desorption were investigated for the 0–100 cm soil layer in the northeast black soil region in this study. The maximum adsorption capacity (Q max ) and maximum adsorption buffer capacity (MBC) of black soil in the study area ranged from 313.8 to 411.9 mg kg -1 and from 3.1 to 28.8 L kg -1 , respectively, within the soil layer of 0–100 cm depth, exhibiting an increasing trend with greater soil depth. The degree of P adsorption saturation (DPS) exhibited a contrasting trend with the variations in Q max and MBC, ranging from 3.8% to 21.6%. The maximum desorption capacity (D max ) and desorption rate (D r ) of soil P ranged from 112.8 to 215.7 mg kg -1 and 32.1% to 52.5%, respectively, while the readily desorbable P (RDP) in soil was within the range of 1.02 to 3.35 mg kg -1 . Both D max , D r , and RDP exhibited a decreasing trend with increasing soil depth before showing an upward trend. These research findings not only provide essential background data for the systematic investigation of soil P in the black soil region but also serve as a valuable reference for assessing soil quality in this area.

In the tropics, warm temperatures and high rainfall contribute to acidic soil formation because of the significant leaching of base cations (K+, Ca2+, Mg2+, and Na+), followed by the replacement of the base cations with Al3+, Fe2+, and H+ ions at the soil adsorption sites. The pH buffering capacity of highly weathered acid soils is generally low because of their low pH which negatively impacts soil and crop productivity. Thus, there is a need to amend these soils with the right amount of inorganic liming materials which have relatively high neutralizing values and reactivity to overcome the aforementioned problems. Soil leaching and the pH buffering capacity studies were conducted to determine whether the co-application or co-amendment of a calcium carbonate product (Calciprill) and sodium silicate can improve soil nutrient retention and pH buffering capacity of the Bekenu series (Typic Paleudults). A 30 day soil leaching experiment was carried out using a completely randomized design with 16 treatments and 3 replications after which the leached soil samples were used for a pH buffering capacity study. The Calciprill and sodium silicate treatments significantly improved soil pH, exchangeable NH4+, available P, exchangeable base cations, Effective Cation Exchange Capacity (ECEC), and pH buffering capacity in comparison with the untreated soil. The improvements were attributed to the alkalinity of Calciprill and sodium silicate due to their high inherent K+, Ca2+, Mg2+, and Na+ contents. The neutralizing effects of the amendments impeded the hydrolysis of Al3+ (96.5%), Fe2+ (70.4%), and Mn2+ (25.3%) ions resulting in fewer H+ ions being produced. The co-application of Calciprill and sodium silicate reduced the leaching of Ca2+ (58.7%) and NO3− (74.8%) from the amended soils. This was due to the ability of sodium silicate to reduce soil permeability and protect the Calciprill and available NO3− from being leached. This also improved the longevity of Calciprill to enhance the soil pH buffering capacity. However, the amounts of NH4+, P, and base cations leached from the amended soils were higher compared with the un-amended soils. This was due to the high solubility of sodium silicate. The most suitable combination amendment was 7.01 g Calciprill and 9.26 g sodium silicate (C2S5) per kilogram soil. It is possible for farmers to adopt the combined use Calciprill and sodium silicate to regulate soil nutrient retention and improve the soil pH buffering capacity of highly weathered acidic soils. This will enhance soil and crop productivity.

For the first time, a nonspecific neutralizing effect of rhizodeposits of medicinal plants has been found in a leached chernozem. The neutralization of actual, exchangeable, and total acidity of the soil takes place against the background of a decrease in the activity of calcium ions in the soil solution. It can be supposed that this effect is due to the release of secondary metabolites of phenol nature in the rhizodeposits. These substances can change the anionic composition of the soil adsorption complex. Plant species with the maximum effect on the composition of the soil adsorption complex have been identified.