Thermodynamics of interaction of lindane on silty loam and silty clay loam Indian soils

Abstract

Interaction of lindane with silty loam and silty clay loam soils was studied in batch tests at 23, 30 and 37° C. Sorption experiments were carried out at four concentrations and for varying time of contact upto 72 hours. This was followed by desorption studies. No desorption was observed. The sorption data was analysed using sorption equations and evaluating the thermodynamic parameters. The sorption was found to be predominantly entropic in nature and a combined effect of adsorption and chemisorption. The effect of organic matter and other chemical and mineralogical constituents of soils has also been discussed. The sorption with single application of lindane with the two soil types indicates that the insecticide is less likely to reach groundwater.     

Nonideal transport of contaminants in heterogeneous porous media: 9 - impact of contact time on desorption and elution tailing

A series of miscible-displacement experiments was conducted to examine the impact of sorption contact time on desorption and elution of trichloroethene from a well-characterized soil. A large number of contact times were examined, spanning 1 h to 4 years (∼2 × 10⁶ h). Effluent trichloroethene concentrations were monitored over a range of greater than six orders of magnitude, allowing characterization of potential asymptotic tailing. The results of the column experiments showed that trichloroethene exhibited extensive elution tailing for all experiments. Each increase in contact time resulted in a successive increase in the extent of tailing. In total, the number of pore volumes of water flushing required to reach the analytical detection limit increased from approximately 1000 for the 1-h contact time to almost 9000 for the 4-year contact time. These results indicate that a contact time of less than 1 h produced a sorbed phase that is relatively resistant to desorption, and that a progressive increase in resistance to desorption occurred with increased contact time. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous-distribution reaction function was used to successfully simulate the measured data. The nonlinear sorption, the apparent rapid development of desorption resistance, and the progressive increase in resistance with increasing contact time are consistent with behavior anticipated for sorbate interactions with hard-carbon components of the soil.     

Sorption and desorption of the diketonitrile metabolite of isoxaflutole in soils

Isoxaflutole is a new pre-emergence corn herbicide that undergoes rapid conversion to a diketonitrile derivative (DKN) in soils. Sorption-desorption studies were conducted in five different soils varying in physical and chemical properties. A batch equilibration technique was used with total initial aqueous solution concentrations of DKN at 0.25, 0.75, 2.0, 8.0, 25, 75, 150, and 250 mg l(-1). After the sorption process, two subsequent desorptions were conducted with an equilibration period of 7 days. A high correlation existed between the desorption coefficient, K(Fd) and the organic matter content of soils (r(2)=0.844 for the first desorption and r(2)=0.861 for the second desorption), while the clay content did not greatly influence the desorption of DKN. Although the sorption of DKN was generally reversible, a sorption-desorption hysteresis was apparent in all soils. The site energy distribution curves emphasized the fact that DKN binds tightly to soils with higher organic matter content and greater proportion of DKN was retained by those soils     

Sorption and desorption of imidazolium based ionic liquids in different soil types

This study investigates the influence of the two different clay minerals kaolinite and smectite as well as of organic matter on the cation sorption and desorption behaviour of three imidazolium based ionic liquids -1-butyl-3-methyl-imidazolium tetrafluoroborate (IM14 BF(4)), 1-methyl-3-octyl-imidazolium tetrafluoroborate (IM18 BF(4)) and 1-butyl-3-methyl-imidazolium bis[(trifluoromethyl)sulfonyl]imide (IM14 (CF(3)SO(2))(2)N) - in soil. The German standard soil Lufa 2.2 - a natural soil classified as a loamy sand - was the basis substrate for the different soil compositions and also served as a reference soil. The addition of organic matter and clays increases the sorption of the substances and in particular smectite had striking effects on the sorption capacity for all three ionic liquids indicating that ionic interactions play an important role for sorption and desorption processes of ionic liquids in soil. One exception was for kaolinite-containing soils and the IM14 cation: with (CF(3)SO(2))(2)N(-) as an anion the sorption was identical at either 10 wt% or 15 wt% clay content, and with BF(4)(-) sorption was even lower at 15 wt% kaolinite than at 10 wt%. Desorption was weak for IM18 BF(4), presumably owing to the longer alkyl side chain. With regard to the influence of kaolinite on desorption, the same pattern was observed as it was found for the sorption of IM14 BF(4) and IM14 (CF(3)SO(2))(2)N.     

Long-term tillage effects on soil metolachlor sorption and desorption behavior

Sorption and desorption are two important processes that influence the amount of pesticides retained by soils. However, the detailed sorption mechanisms as influenced by soil tillage management are unclear. This study examined the sorption and desorption characteristics of metolachlor [2-chloro-N-(2-ethyl-6-methyphenyl)-N-(2-methoxy-1-methylethyl)-acetamide] using the soil samples collected from the long-term conservation tillage (CnT) and conventional tillage (CT) research plots established in 1979 in Darlinton, SC. Humic acid (HA) and humin were extracted from the soils and used in the sorption experiments along with the whole soil samples. The sorption experiments were conducted using a batch-equilibration method. Three sequential desorption rinses were carried out following the sorption experiments. By comparing metolachlor sorption and desorption results we observed hysteresis for all soil samples and their organic matter fractions. Sorption nonlinearity (N) and hysteresis were dependent on the structure and composition of soil organic matter (SOM), e.g., Freundlich isotherm exponents (N) of HA and humin from CnT were higher than those of CT treatment, which may be related to high aromaticity of SOM fractions in CT treatment. Sorption capacity (K'f) was positively correlated with soil organic carbon (SOC) content. These results show that long-term tillage management can greatly affect metolachlor sorption and desorption behavior probably by qualitative differences in the structural characteristics of the humic substances.     

Effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene

Biochars are anthropogenic carbonaceous sorbent and their influences on the sorption of environmental contaminants need to be characterized. Here we evaluated the effect of Pinus radiata derived biochars on soil sorption and desorption of phenanthrene. Two biochars separately produced at 350 °C and 700 °C and three soils were tested. Biochar amendment generally enhanced the soil sorption of phenanthrene. The biochar produced at 700 °C generally showed a greater ability at enhancing a soil’s sorption ability than that prepared at 350 °C. The single-step desorption measurement showed an apparent hysteresis in biochar-amended soils. After 28 d equilibration, the sorptive capacity of biochar-amended soil (with an organic carbon content of 0.16%) significantly decreased. This study clearly suggested that biochar application enhanced soil sorption of hydrophobic organic compounds, but the magnitude of enhancement depended on the preparation of biochars, the indigenous soil organic carbon levels, and the contact time between soil and biochar.     

Sorption, desorption, and degradation of (4-chloro-2-methylphenoxy)acetic acid in representative soils of the Danubian Lowland, Slovakia

Herbicide leaching through soil into groundwater greatly depends upon sorption-desorption and degradation phenomena. Batch adsorption, desorption and degradation experiments were performed with acidic herbicide MCPA and three soil types collected from their respective soil horizons. MCPA was found to be weakly sorbed by the soils with Freundlich coefficient values ranging from 0.37 to 1.03 mg^1−1/n kg⁻¹ L^1/n. It was shown that MCPA sorption positively correlated with soil organic carbon content, humic and fulvic acid carbon contents, and negatively with soil pH. The importance of soil organic matter in MCPA sorption by soils was also confirmed by performing sorption experiments after soil organic matter removal. MCPA sorption in these treated soils decreased by 37-100% compared to the original soils. A relatively large part of the sorbed MCPA was released from soils into aqueous solution after four successive desorption steps, although some hysteresis occurred during desorption of MCPA from all soils. Both sorption and desorption were depth-dependent, the A soil horizons exhibited higher retention capacity of the herbicide than B or C soil horizons. Generally, MCPA sorption decreased in the presence of phosphate and low molecular weight organic acids. Degradation of MCPA was faster in the A soil horizons than the corresponding B or C soil horizons with half-life values ranging from 4.9 to 9.6 d in topsoils and from 11.6 to 23.4 d in subsoils.     

Studies on the sorption and desorption characteristics of Zn(II) on the surface soils of nuclear power plant sites in India using a radiotracer technique

Zinc adsorption was studied in the soils of three nuclear power plant sites of India. 65Zn was used as a radiotracer to study the sorption characteristics of Zn(II). The sorption of zinc was determined at 25 and 45 degrees C at pH 7.8+/-0.2 in the solution of 0.01 M Ca(NO3)2 as supporting electrolyte. The sorption data was tested both in Freundlich and Langmuir isotherms and could be described satisfactorily. The effect of organic matter and other physico-chemical properties on the uptake of zinc was also studied in all the soil samples. The results showed that the cation exchange capacity, organic matter, pH and clay content were the main contributors to zinc sorption in these soils. The adsorption maximum was found to be higher in the soil on Kakarpara Atomic Power Plant sites soils having high organic matter and clay content. The zinc supply parameters of the soils are also discussed. In the desorption studies, the sequential extraction of the adsorbed zinc from soils showed that the diethylene triamine penta acetic acid extracted maximum amount of adsorbed zinc than CaCl2 and Mg(NO3)2. The zinc sorption on the soil and amount of zinc retention after extractants desorption shows a positively correlation with vermiculite and smectite mineral content present in the clay fraction of the soil. The amount desorbed by strong base (NaOH) and demineralised water was almost negligible from soils of all the sites, whereas the desorption by strong acid (HNO3) was 75-96% of the adsorbed zinc.     

Sorption behavior of a new acidic herbicide in soils

The sorptive behavior of the experimental herbicide quinmerac (7-chloro-3-methyl-quinoline-8-carboxylic acid) was investigated in soils of different organic carbon content. Distribution coefficients are low (K_d = 0.03 - 12 mL g⁻¹) and are mainly determined by the soil organic carbon content. The adsorption mechanism operating in neutral to slightly acid agricultural soils is supposed to be cation bridging with the anionic form of quinmerac. Under acid conditions (pH 5.2) the predominating sorption mechanism is hydrophobic interaction. Therefore soil pH and cationic composition are also major factors determining the sorptive capacity of soils for quinmerac.

Adsorption kinetics, equilibrium adsorption and desorption isotherms were determined in batch experiments. Sorption kinetics were investigated at various times from 15 min to 96 hours. A two-step sorption behavior with time was found for the anionic form indicating two types of sorption mechanisms or sorption sites. Equilibrium for the first type was reached at a time-scale of minutes and for the second type after 24 hours. Adsorption isotherms were determined for two soil/solution ratios 1/5 and 1/3. Alteration of the adsorbent concentration exerted a strong influence on the adsorption isotherms. An increase of sorption was found with increasing adsorbent concentration. Under natural soil conditions sorption is therefore expected to be higher compared to the batch experiments. Desorption isotherms were obtained using the consecutive desorption method. Desorption hysteresis was not observed which indicates weak interactions. Implications of the results for the movement of quinmerac under field conditions and for models describing transport are discussed.     

Sorption, degradation and mobility of ptaquiloside, a carcinogenic Bracken (Pteridium sp.) constituent, in the soil environment

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glucoside produced by Bracken in amounts up to at least 500 mg m(-2). The toxin is transferred from Bracken to the underlying soil from where it may leach to surface and groundwater's impairing the quality of drinking water. The objectives of the present study were to characterize the solubility, degradation and retention of PTA in soils in order to evaluate the risk for groundwater contamination. PTA was isolated from Bracken. The logarithmic octanol-water and ethyl acetate-water partitioning coefficients for PTA were -0.63 and -0.88, respectively, in agreement with the high water solubility of the compound. PTA hydrolysed rapidly in aqueous solution at pH 4 or lower, but was stable above pH 4. Incubation of PTA with 10 different soils at 25 degrees C showed three different first order degradation patterns: (i) rapid degradation observed for acid sandy soils with half life's ranging between 8 and 30 h decreasing with the soil content of organic matter, (ii) slow degradation in less acid sandy soils with half-lives of several days, and (iii) fast initial degradation with a concurrent solid phase-water partitioning reaction observed for non-acid, mostly clayey soils. The presence of clay silicates appears to retard the degradation of PTA, possibly through sorption. Degradation at 4 degrees C was generally of type (iii) and degradation rates were up to 800 times lower than at 25 degrees C. Sorption isotherms for the same set of soils were almost linear and generally showed very low sorption affinity with distribution coefficients in the range 0.01-0.22 l kg(-1) at a solution concentration of 1 mg l(-1) except for the most acid soil; Freundlich affinity coefficients increased linearly with clay and organic matter contents. Negligible sorption was also observed in column studies where PTA and a non-sorbing tracer showed almost coincident break-through. Leaching of PTA to the aqueous environment will be most extensive on sandy soils, having pH >4 and poor in organic matter which are exposed to high precipitation rates during cold seasons.     

Two-compartment sorption of phenanthrene on eight soils with various organic carbon contents

Sorption characteristics of phenanthrene (PHE) were studied on eight soils with organic carbon contents spanning over an order of magnitude using phase distribution relationships (PDRs) at 1 h, 48 h, and 720 h contact times. A new algebraic method was employed to describe the sorption characteristics at different time intervals (between 1 h and 48 h, and 1 h and 720 h). It was found that nonlinearity increased with increasing contact time and sorption that occurred in the subsequent time interval following the initial 1 h exhibited stronger isotherm nonlinearity. Sorption coefficients were positively correlated with the organic carbon contents of the soils. Detailed sorption dynamics were also examined on these soils. A two-compartment, first-order model was used to describe the sorption dynamics. The rate constants of the two compartments differed 18-170 times, suggesting the dissimilar sorption behaviors of the mathematically separated compartments. These two compartments were labeled fast and slow sorption compartment according to the rate constants. Calculation showed that the fast compartment accounted for over 80% of the overall sorption at the initial 1 h, while the slow compartment predominated the total sorption in the following 47 h. By combining the discussion of PDRs and sorption dynamics, the contributions of the two compartments to linear and nonlinear sorption were differentiated. The slow sorption compartment made a major contribution to nonlinear sorption and possibly to sequestration of organic pollutants by these soils.     

Effects of SOM, surfactant and pH on the sorption-desorption and mobility of prometryne in soils

Sorption and desorption of the herbicide prometryne in two types of soil subjected to the changes of pH and soil organic matter and surfactant were investigated. The sorption and desorption isotherms were expressed by the Freundlich equation. Freundlich K_f and n values indicate that soil organic matter was the major factor affecting prometryne behavior in the test soils. We also quantified the prometryne sorption and desorption behavior in soils, which arose from the application of Triton X-100 (TX100), a nonionic surfactant and change in pH. Application of TX100 led to a general decrease in prometryne sorption to the soils and an increase in desorption from the soils when applied in dosages of the critical micella concentration (CMC) 0.5, 1 and 2. At the concentration below the CMC, the non-ionic surfactant showed a tendency to decrease prometryne sorption and desorption. It appeared that TX100 dosages above CMC were required to effectively mobilize prometryne. Results indicate that the maximum prometryne sorption and minimum prometryne desorption in soils were achieved when the solution pH was near its pK_a. Finally, the influence of TX100 on the mobility of prometryne in soils using soil thin-layer chromatography was examined.     

Sorption and desorption of sulfentrazone in Brazilian soils

This study was undertaken to obtain information about the behavior of sulfentrazone in soil by evaluating the sorption and desorption of the herbicide in different Brazilian soils. Batch equilibrium method was used and the samples were analyzed by high performance liquid chromatography. Based on the results obtained from the values of Freundlich constants (Kf), we determined the order of sorption (Haplic Planosol < Red-Yellow Latosol < Red Argisol < Humic Cambisol < Regolitic Neosol) and desorption (Regolitic Neosol < Red Argisol < Humic Cambisol < Haplic Planosol < Red-Yellow Latosol) of sulfentrazone in the soils. The process of pesticide sorption in soils was dependent on the levels of organic matter and clay, while desorption was influenced by the organic matter content and soil pH. Thus, the use of sulfentrazone in soils with low clay content and organic matter (low sorption) increases the probability of contaminating future crops.     

Sulfamethoxazole sorption by sediment fractions in comparison to pyrene and bisphenol A

The environmental behavior of antibiotics has attracted great research attention. However, their sorption mechanisms in soils/sediments are still unknown. Comparison of the sorption properties between the widely-studied hydrophobic organic contaminants (HOCs) and antibiotics may provide valuable insight to antibiotic sorption mechanisms. Thus, in this study batch experiments for pyrene (PYR), bisphenol A (BPA), and sulfamethoxazole (SMX) sorption were conducted on a sediment sample and its separated fractions. Our results showed the high sorption of PYR on black carbon and organic matter. Although high sorption of SMX was observed for both separated organic fractions (humic acids) and inorganic mineral particles, the original sediment particles showed relatively low sorption. Competitive sorption between SMX and dissolved humic acid on mineral particles was observed in this study. This competitive interaction is a unique process for antibiotic sorption in soils/sediments compared with apolar HOCs and may be one of the important factors controlling the antibiotic sorption.     

Sorption of 3,4-dichloroaniline on four contrasting Greek agricultural soils and the effect of liming

Sorption of 3,4-dichloroaniline (3,4-DCA) on four typical Greek agricultural soils, with distinct texture, organic matter content and cation exchange capacities, was compared by using sorption isotherms and the parameters calculated from the fitted Freundlich equations. The sorption process of 3,4-DCA to the soil was completed within 48-72 h. The 3,4-DCA sorption on all soils was well described by the Freundlich equation and all sorption isotherms were of the L-type. The sandy clay loam soil with the highest organic matter content and a slightly acidic pH was the most sorptive, whereas the two other soil types, a high organic matter and neutral pH clay and a low organic matter and acidic loam, had an intermediate sorption capacity. A typical calcareous soil with low organic matter had the lowest sorption capacity which was only slightly higher than that of river sand. The 3,4-DCA sorption correlated best to soil organic matter content and not to clay content or cation exchange capacity, indicating the primary role of organic matter. The distribution coefficient (K(d)) decreased with increasing initial 3,4-DCA concentration and the reduction was most pronounced with the highly sorptive sandy clay loam soil, suggesting that the available sorption sites of the soils are not unlimited. Liming of the two acidic soils (the sandy clay loam and the loam) raised their pH (from 6.2 and 5.3, respectively) to 7.8 and reduced their sorption capacity by about 50 %, indicating that soil pH may be the second in importance factor (after organic matter) determining 3,4-DCA sorption.     

Enhancement of chlorophenol sorption on soil by geophagous earthworms (Metaphire guillelmi)

Earthworms are the dominant soil biomass of many terrestrial ecosystems and markedly influence the physico-chemical and biological properties of soil; however, little is known about the effects of earthworm activities on the environmental behavior of micropollutants in soil. We studied the sorption and desorption of 2,4-dichlorophenol, 2,4,6-trichlorophenol, and pentachlorophenol on geophagous earthworm (anecic Metaphire guillelmi) casts of various aging times and on the parent soil. The casts were characteristic of lower pH and higher content of fine particles (silt and clay) than the parent soil. The sorption of the chlorophenols on the soil and casts were well fitted to linear isotherms, with sorption capacity in the order of pentachlorophenol > 2,4-dichlorophenol > 2,4,6-trichlorophenol. The sorption on the cast with different aging time was quite similar and was higher than on the parent soil. The sorption on the soil did not change between pH 7.07 of the soil and pH 6.76 of the casts. The desorption hysteresis of the chlorophenols on the soil and casts was compound specific and 2,4,6-trichlorophenol showed the highest hysteresis. The higher sorption capacity of the casts was not owing to the lowered pH of the casts, but mainly to the higher fine particles in the casts and the possible changes of nature of the soil organic matter through the earthworm gut passage. Our results indicate that geophagous earthworms may change sorption behavior and thus the bioavailability and transport of chlorophenols in soil. Earthworm effects should be considered when evaluating the environmental behavior and risk of organic pollutants in the ecosystems where earthworms are abundant.     

Characteristic and mechanism of sorption and desorption of benzene on humic acid

Environmental Science and Pollution Research - The sorption/desorption behaviors of benzene, toluene, ethylbenzene, and xylene (BTEX) on soil organic matter (SOM) have a significant influence on...     

水溶性羧甲基壳聚糖对Cd2+的解吸行为研究

为改善壳聚糖(CTS)的水溶性及对重金属的配位能力,合成水溶性好并能与重金属形成配位作用的水溶性羧甲基壳聚糖(WSCC),研究了WSCC对镉的增溶、解吸行为,考察了pH、离子强度、有机质含量和WSCC初始浓度对镉的解吸影响。结果表明:WSCC对碳酸镉的增溶效果显著,当其质量浓度为2g/L时溶液中Cd2+可达到275mg/L;WSCC对镉解吸能力随着土壤中有机质含量的增加而降低,pH的升高、离子强度的增加和WSCC初始浓度的增加有利于镉的解吸;WSCC对镉污染土壤的解吸更符合准二级动力学方程,该静态解吸研究可以为镉污染土壤的修复提供基础信息及依据。     

Soil phosphorus fractions in solution: influence of fertiliser and manure, filtration and method of determination.

This study investigated the forms of soil P released to solution, accuracy of their determination, and influence of colloids on P sorption/desorption dynamics. A Hagerstown silt loam, amended with dairy and poultry manure or superphosphate at five rates (0, 25, 50, 100, and 200 kg P ha(-1)), was extracted at two soil:solution ratios (1:5 and 1:100) and filtered at three pore sizes (0.8, 0.45, and 0.22 microm). Results showed that relative to the proportion of dissolved organic P (DOP, determined as the difference between total dissolved P [TDP] and P detected by ion chromatography), DRP increased with amendment rate. Relative to Mehlich-3 extractable P, DRP exhibited a power relationship with a much greater potential for soil P release at concentrations in excess of ca. 50 mg Mehlich-3 P kg(-1). Concentrations of DRP, determined by the acid molybdate method, were on average 12.5% greater than P detected by ion chromatography indicating P was solubilised during colorimetric determination. A linear relationship was found between total Al and DRP, which could indicate acid mediated hydrolysis of A1-humic-P substances, although acid mediated desorption of P from colloids cannot be discounted. No difference in solubilised P was found between solutions filtered at 0.22 and 0.45 microm, but was found between 0.8 microm and smaller filter sizes. Organic P extracted from manured soils was more recalcitrant than that extracted from soils amended with superphosphate, the later attributed to its accumulation in more labile pools. The sorption/desorption of P by colloids in solution were greatly affected by the rate of amendment and the soil:solution extraction ratio. More P was sorbed by superphosphate solutions compared to dairy manure amended soil solutions and was attributed to the saturation of colloidal P sorption sites by organic matter. In order to minimise the effects of colloids on P dynamics and the potential for hydrolysis in solution, filtration to at least 0.45 microm is required. However, soils with a lesser aggregate stability may require additional filtration.     

2,4-Dichlorophenoxyacetic acid (2,4-D) sorption and degradation dynamics in three agricultural soils

The fate and transport of 2,4-dichlorophenoxyacetic acid (2,4-D) in the subsurface is affected by a complex, time-dependent interplay between sorption and mineralization processes. 2,4-D is biodegradable in soils, while adsorption/desorption is influenced by both soil organic matter content and soil pH. In order to assess the dynamic interactions between sorption and mineralization, 2,4-D mineralization experiments were carried using three different soils (clay, loam and sand) assuming different contact times. Mineralization appeared to be the main process limiting 2,4-D availability, with each soil containing its own 2,4-D decomposers. For the clay and the loamy soils, 45 and 48% of the applied dose were mineralized after 10 days. By comparison, mineralization in the sandy soil proceeded initially much slower because of longer lag times. While 2,4-D residues immediately after application were readily available (>93% was extractable), the herbicide was present in a mostly unavailable state (<2% extractable) in all three soils after incubation for 60 days. We found that the total amount of bound residue decreased between 30 and 60 incubation days. Bioaccumulation may have led to reversible immobilization, with some residues later becoming more readily available again to extraction and/or mineralization.