Soil Thin-layer Chromatography Research Articles

Adsorption, mobility, and degradation of the pesticide propaquizafop in five agricultural soils in China

Propaquizafop is a fatty acid synthetic herbicide used to control annual and perennial grasses. To understand the potential environmental risks of propaquizafop to crops and food safety, the adsorption, mobility, and degradation of propaquizafop in five different soils were studied. At an initial concentration of 5 mg L−1 propaquizafop, its adsorption equilibrium was reached within 24 h, and the adsorption rates were between 46.98 and 57.76%. The Elovich kinetic model provided the best fit for the kinetic model, with R2 values between 0.9882 and 0.9940. For the isothermal adsorption tests, the Freundlich model was used to better fit the adsorption characteristics of propaquizafop in different soils, with R2 values between 0.9748 and 0.9885. Increasing the concentration of Ca2+ was beneficial for propaquizafop adsorption. In the soil thin-layer chromatography tests, the Rf of propaquizafop in the five soil samples ranged from 0.076 to 0.123. The results of the soil column leaching tests showed that propaquizafop did not migrate in the five soil columns; it was not detected in the leachate of each soil column, and propaquizafop in the soil columns only existed in the 0–5 cm soil layer. The results of soil thin-layer chromatography and soil column leaching tests showed that propaquizafop is a pesticide with a weak migration ability. Under the same environmental conditions, the degradation rate of propaquizafop in different soils followed the order LF fluvo–aquic soil (T1/2 = 1.41 d) > CS red loam (T1/2 = 2.76 d) > SX paddy soil (T1/2 = 3.52 d) > CC black soil (T1/2 = 5.74 d) > BS ginseng soil (T1/2 = 7.75 d). Considering the effects of soil moisture, incubation temperature, and microorganisms on propaquizafop degradation in the soil, temperature was found to have the greatest influence on its degradation rate.

Transport and Environmental Risks of Propachlor Within the Soil-Plant-Water Phase as Affected by Dissolved Organic Matter as a Nonionic Surfactant.

Propachlor is a widely used acylaniline herbicide for weeding annual gramineous and dicot plants in farmland. As a toxic agricultural chemical, it is overused in crop production and has become one of the most serious environmental pollutants. Yet, understanding the impact of environmental factors on its behavior in farmland soils is critically important for healthy crop production and food safety. In this study, we characterized the effect of dissolved organic matter (DOM) extracted from rice straw on the mobility behavior of propachlor in farmland soil using comprehensive approaches such as the batch equilibrium experiment, soil thin-layer chromatography, soil column leaching, and wheat bioaccumulation with Triton X-100 (TX-100) as a reference surfactant. The application of DOM at 60 and 120 mg DOC L-1 and TX-100 at 96, 192, and 288 mg L-1 reduced the sorption and increased the desorption of propachlor in soil. Freundlich constant K f values (sorption) of propachlor declined with the expansion of DOM and TX-100 concentrations. The addition of DOM and TX-100 increased the mobility of propachlor and the total concentration of propachlor in the leachate of soil columns. The retention factors (R f) were evaluated in the soil thin-layer chromatography as 0.741 and 0.772 (for DOM) and 0.731, 0.763, and 0.791 (for TX-100), all of which were greater than the control (0.710) under the treatment. The application of DOM or TX-100 reduced root growth (biomass) and increased bioaccumulation of propachlor in the roots and shoots of wheat. The outcome of the study can provide important references for the rational use of propachlor and help agronomic management to minimize pesticide contamination in realistic crop production.

Availability of Metribuzin-Loaded Polymeric Nanoparticles in Different Soil Systems: An Important Study on the Development of Safe Nanoherbicides.

Nanoformulations have been used to improve the delivery of fertilizers, pesticides, and growth regulators, with a focus on more sustainable agriculture. Nanoherbicide research has focused on efficiency gains through targeted delivery and environmental risk reduction. However, research on the behavior and safety of the application of these formulations in cropping systems is still limited. Organic matter contained in cropping systems can change the dynamics of herbicide−soil interactions in the presence of nanoformulations. The aim of this study was to use classical protocols from regulatory studies to understand the retention and mobility dynamics of a metribuzin nanoformulation, compared to a conventional formulation. We used different soil systems and soil with added fresh organic material. The batch method was used for sorption−desorption studies and soil thin layer chromatography for mobility studies, both by radiometric techniques. Sorption parameters for both formulations showed that retention is a reversible process in all soil systems (H~1.0). In deep soil with added fresh organic material, nanoformulation was more sorbed (14.61 ± 1.41%) than commercial formulation (9.72 ± 1.81%) (p < 0.05). However, even with the presence of straw as a physical barrier, metribuzin in nano and conventional formulations was mobile in the soil, indicating that the straw can act as a barrier to reduce herbicide mobility but is not impeditive to herbicide availability in the soil. Our results suggest that environmental safety depends on organic material maintenance in the soil system. The availability can be essential for weed control, associated with nanoformulation efficiency, in relation to the conventional formulation.

Separation and analysis of heavy metal ions by thin-layer chromatography (TLC)—a mini-review (2000–2019)

This review article describes the work reported on the separation and analysis of heavy metal ions by different modes of thin-layer chromatography (TLC) such as soil, micellar, and reversed-phase TLC during 2000–2019. The history of different modes of TLC has been briefly mentioned. The literature survey reveals that the number of papers reported during 2000–2019 on the separation of heavy metal ions by different modes of TLC follows the trend: micellar TLC > soil TLC > reversed-phase TLC.

Adsorption, mobility, biotic and abiotic metabolism and degradation of pesticide exianliumi in three types of farmland

Exianliumi is a newly developed pesticide for controlling diseases caused by microbes or meloidogynes during plant vegetable and reproductive stages. To date, little is known about the environmental behavior and fate of its residues in soil. To explore its potential environmental risks to crop production and food safety, three typical Chinese agricultural soils were examined by analyzing adsorption, mobility leaching, and degraded metabolites of exianliumi in soils. Exianliumi inclined to bind more to Heilongjiang soil (HLJS), followed by Nanjing soil (NJS) and Jiangxi soil (JXS). Soil thin-layer chromatography and column leaching tests showed a weak migration in HLJS and strong mobility in JXS. Under the same condition, exianliumi rapidly decayed in NJS, followed by HLJS and JXS. The differential degradative capacity for exianliumi in the soils was related to chemical, physical and biological interactions basically through organic matter content, temperature, soil moisture and microorganisms. The half-normal, normal and pareto effect plots demonstrated that temperature, microorganisms and soil moisture dominantly influenced the degradation of exianliumi. We further characterized metabolites of exianliumi catabolized in NJS using High Resolution Liquid Chromatography-Quadrupole-Time of Flight-Mass Spectrometer/Mass Spectrometer (HRLC-Q-TOF-MS/MS). Eight degradation products and three conjugates of exianliumi were detected and the possible degradative pathways were highlighted. This is the first report about exianliumi degradation in soils with multi-pathways, which provides the basic data for environmental risk assessment of crop production and food security.

Natural biochar effect on sorption–desorption and mobility of diclosulam and pendimethalin in soil

The amendment of anthropogenic soils with natural biochar (without pyrolysis process) presents several environmental and agronomic benefits. However, there is little information available on the interaction of natural biochar with the herbicides applied directly into the soil. To address this knowledge gap, the influence of natural biochar on the sorption–desorption and mobility of diclosulam and pendimethalin herbicides in an agricultural soil was evaluated. The biochar was extracted from the profile of an Oxisol and post-dates the Holocene. The Ultisol-Typic Hapludalf used in this study was amended with natural biochar at rates of 0 (control), 0.1, 0.5 and 1.0% (m m−1). The 14C-diclosulam and 14C-pendimethalin showed specific activities of 0.002587 and 5.55 MBq mg−1, respectively. The sorption–desorption process was assessed by batch–equilibrium experiments. Liquid scintillation counting and soil thin-layer chromatography were used to determine herbicides adsorption and mobility. Application of natural biochar slightly increased the linear sorption coefficient (Kd) of each herbicide (from 0.22 to 0.50 L kg−1 for diclosulam, and from 25.55 and 37.81 L kg−1 for pendimethalin) in the soil, and the corresponding sorption percentages were 18.53–34.14% and 96.22–97.42%, respectively. However, the soil amendment did not alter the mobility of either herbicide, with retention factor (Rf) values of ~0.99 and 0.20 for diclosulam and pendimethalin, respectively, regardless of the natural biochar amount. Therefore, the presence of biochar in soil may not interfere with the bioavailability of diclosulam and pendimethalin in weed control under field conditions.

Cow bone char as a sorbent to increase sorption and decrease mobility of hexazinone, metribuzin, and quinclorac in soil

Hexazinone, metribuzin, and quinclorac herbicides are used extensively throughout Brazil, and they can easily be leached to groundwater sources. Bone char (BC) has been shown to strongly sorb organic compounds and could be used as a sorbent to increase herbicide sorption and decrease leaching, although the better form of application is not known. The aim of this research was to assess the effect of cow BC on the sorption-desorption and mobility of hexazinone, metribuzin, and quinclorac applied to a sandy loam tropical soil under laboratory conditions. The methodology of the sorption-desorption studies was established using a batch equilibrium method, and the treatments were unamended soil, pure BC, and BC-amended soil (at a rate of 5% by weight). Herbicide mobility studies were evaluated by column leaching and soil thin-layer chromatography (TLC). In the column leaching studies, BC was either applied to the surface or incorporated into the 0–10 cm top layer of soil, the latter at a rate of 5% by weight (60 t ha−1). A glass column was prepared for each treatment, and analyses of 14C-herbicides were performed by liquid scintillation counting. Finally, for TLC studies the BC treatments were unamended soil, BC (5% by weight)-amended soil, soil + BC band (1 cm) in the middle, and soil + BC band at the top. We conclude that cow BC is an excellent sorbent to reduce mobility of hexazinone, metribuzin, and quinclorac in a tropical soil through the high sorption of these herbicides, regardless of application form of the material. Thus, it is possible to minimize the pollution of soil-applied herbicide simultaneously, as the BC and thus the herbicides can remain in the soil for a long time.

Impact of surfactant and dissolved organic matter on uptake of atrazine in maize and its mobility in soil

The purposes of this study were to investigate the activation and transport of atrazine in the presence of dissolved organic matter (DOM) and the surfactant (Triton X-100) and to understand interactions between DOM, Triton X-100, and atrazine. Uncontaminated soils collected from Nanjing, China, along with DOM extracted from rice straw and Triton X-100 (TX-100), were used in the study. The sorption and desorption experiments were carried out using the standard batch equilibration analysis. Soil column leaching was conducted with soil samples packed into PVC columns. Soil thin-layer chromatography was performed using soil and water mixture spread on a 0.5–0.7-mm-thick layer over 20 × 10-cm glass plates. Atrazine accumulation in maize was determined by planting maize in plastic pots (1 L) containing 1 kg soil mixed with 1.0 mg kg−1 atrazine. Soils were watered with different solutions, with the relative water content of 60%. Using batch experiment and soil thin-layer chromatography, application of DOM and surfactant reduced sorption and increased desorption of atrazine in soil. In column experiment, DOM and surfactant significantly promoted the mobility of atrazine in soil and the total concentration of atrazine in leachate of the soil column. Accumulation of atrazine in both maize roots and shoots increased with the elevated concentration of surfactant, whereas the content of atrazine declined with the increase of the DOM concentration. Dissolved organic matter and TX-100 affected the partitioning and transport of atrazine in soil–water and soil–plant ecosystems.

Effects of root exudates on the mobility of pyrene in mangrove sediment-water system

Mangrove ecosystems receive substantial polycyclic aromatic hydrocarbons (PAHs) from human activities. The mechanism of transport and translocation of PAHs within mangrove sediment is not well understood. In the present study, the mobility of pyrene in two typical mangrove sediments was studied using soil thin layer chromatography (TLC). The mobility of pyrene in the sediments displayed an inverse trend with organic carbon (foc) content. As one of the important fraction in sediment organic matter pool, the influence of root exudates on adsorption of pyrene within the tested sediments was also evaluated. In particular, root exudates significantly enhanced the bioavailability and mobility of pyrene in the sediments. The effectiveness of root exudates in promotion of pyrene mobility follows an order: citric acid>oxalic acid>malic acid>artificial root exudates (ARE). In addition, mobility factors of pyrene from root exudate treatments were significantly higher than the value determined in the control, and the magnitude of mobility factor (Rf) showed a positive correlation with root exudate concentrations. Results of this study could promote our understanding of the mobility of PAHs in contaminated mangrove sediments.

Influence of biochar amendments to soil on the mobility of atrazine using sorption-desorption and soil thin-layer chromatography

Biochars, the carbonaceous residue from biomass pyrolysis, have been proposed as an agriculture soil amendment to improve soil fertility and retain a broad range of environmental contaminants. The objective of this research was therefore to investigate whether the additions of cassava wastes-based biochars obtained at 750°C (noted as MS750) with the specific area of 430m2/g to an agriculture soil could effectively attenuate the transport of atrazine by using laboratory batch sorption studies and soil thin-layer chromatography. To illustrate the worst-case sorption, MS750 with different application percentages (w/w: 0%, 0.1%, 0.5%, 1%, 3%, 5%) were added into krasnozem soil only with 0.75% organic matter to determine sorption-desorption behavior and migration of atrazine. The results obtained indicated that the occurrence of cassava wastes-derived biochar significantly enhanced the sorption capacity of the soil for atrazine. The sorption affinity augmented as expected with application rates of MS750, and the distribution coefficients in biochar-added soils were greater than that in soil alone, likely due to enhancement of soil organic carbon content and favorable sorption domains for organic compounds caused by amendment of biochars. Sorption isotherms were characterized by nonlinear curves, which indicated the heterogeneous sites on MS750-soil mixture. Desorption work exhibited a remarkable impact of biochars amendment into soils on desorption of atrazine, in which an apparent hysteresis was undergone. This study clearly revealed that biochars from cassava wastes application enhanced retention of soil for atrazine to some extent, nevertheless, the magnitude of enhancement of the sorption affinity was still of dependence on the solution pH value, environmental temperature, as well as contact time between soil and biochars. The △Go values with less than −20kJ/mol and the effect of solution pH variation on sorption capacity of 6 sorbents indicated that the equilibrium process may be involved physisorption, as well as accompanied with chemisorption. The results from thermodynamic analysis showed that sorption of atrazine in soils amended with MS750 was thermodynamically endothermic. Positive correlation between the mobility level of pesticide and the addition percentage of biochars suggested that the application of biochars derived from cassava waste was available to retain pesticides and attenuate the leach into groundwater. These observations provide important information on the application of biochars produced at 750°C as engineered sorbents for soil remediation and compounds elimination.

Desorption and mobilization of three strobilurin fungicides in three types of soil.

Phenamacril (JS399-19 with independent intellectual property developed by China), azoxystrobin, and kresoxim-methyl are strobilurin fungicide. Due to their broad spectrum and good control of most of known fungi, strobilurin fungicide has been widely used in agriculture management. Thus, it is important to evaluate their environmental behaviors particularly in soils and underground water. In this study, the sorption/desorption and mobility of strobilurin fungicides in three Chinese soils (Jiangxi red soil, Taihu paddy soil, and Northeast China black soil) were conducted using comprehensively analytic approaches including batch experiment and soil thin-layer chromatography. The strobilurin fungicides were hard to be adsorbed in Jiangxi red soil but had medium adsorption capability in Tanhu paddy soil and Northeast China black soil, while the desorption of three strobilurin fungicides ranked in the order of Jiangxi red soil > Taihu paddy soil > Northeast China black soil. Soil properties including soil organic matter (SOM), pH, and cationic exchange capacity (CEC) affected the adsorption/desorption of the fungicides. Azoxystrobin and kresoxim-methyl had weak mobility in the soils. JS399-19 was moderately mobile in Jiangxi red soil but was not easily moved in Taihu paddy soil and Northeast China black soil. Due to their weak mobility in soils, these strobilurin fungicides tended to remain in the soil phase but not to shift downward to underground water. As azoxystrobin and JS399-19 had a long retention period in soil, there may become persistent residues in the soil environment.

Effect of Soil Chemical and Physical Properties on Cd Mobility Studied by Soil Thin-Layer Chromatography

Heavy metals contamination threat to the environment is a big concern. Predicting the movement of heavy metals such as Cd in soil is an important goal. In this study the effect of soil chemical and physical properties on Cd mobility were done using a thin layer chromatography (Soil TLC). The soils used in this research have a wide range of organic matter (2.1-29 g/kg), pH value (4.9-8.8), CEC (4.1-99 cmol/kg), bases saturation, iron and aluminum oxides to examines its effect on Cd mobility. The (Rf) values obtained from soil thin layer chromatography ranged from 0.25 to 0.95 and it showed that Cd was slightly mobile in 64 %, moderately mobile in 29 % and very mobile in 7 % of the soils. The Rf indicates that Cd mobility would decrease with increasing amounts of iron oxide fractions; silt % and exchangeable Mg2+ in the soils. Rcd values increased with increasing amounts of the iron oxide fractions (Feo, Fep, and Fed); silt % and exchangeable Mg2+ in the soils. Finally, both Rcd and Rf factors showed Cd mobility to be higher in those soils with a high percentage of sand.

Influence of Copper on Transport and Dissipation of Lambda-Cyhalothrin and Cypermethrin in Soils

Repeated applications of bordeaux mixture (a blend of copper sulfate and calcium hydroxide) and pyrethroid insecticides (Pys) have led to elevated copper (Cu) and Pys concentrations in vineyard surface soils. To understand the potential influence of Cu on the fate of Pys in the soil environment, we selected two Pys, cypermethrin (CPM) and lambda-cyhalothrin (λ-CHT), and two typical Chinese vineyard soils, Haplic Acrisol and Luvic Phaeozem, as experimental samples. The dissipation experiment was conducted at room temperature in the dark, and the transport of both Pys through the soils was investigated using soil thin-layer chromatography. The results showed that the transport of Pys in both soils increased as the Cu2+ concentration increased from 0 to 100 mg L−1, and Pys were more transportable in Haplic Acrisol (HA) than in Luvic Phaeozem (LP) under the same experimental conditions. For CPM, only 100 mg L−1 of Cu2+ significantly (P < 0.05) increased Pys transport through both soils relative to water. Lambda-CHT was significantly (P < 0.05) transported through HA by all the Cu2+ concentrations compared to water, and all but the 1 mg L−1 of Cu2+ significantly (P < 0.05) increased the transport of λ-CHT through LP relative to water. However, the dissipation rates of CPM and λ-CHT decreased with the addition of Cu to soils. Our findings suggest that the risk of groundwater contamination by Pys increases in the soils with elevated Cu concentrations.

Impact of coexistence of carbendazim, atrazine, and imidacloprid on their adsorption, desorption, and mobility in soil

The effect of coexisting pesticide on adsorption/desorption and mobility of another one was investigated with carbendazim (CBD), imidacloprid (IDP), and atrazine (ATR). The data indicated that adsorption of CBD, ATR, and IDP on the tested soil was fitted well by Freundlich equation and increased with an order of IDP < ATR ≪ CBD. Adsorption of a pesticide was decreased by the coexistence of another one through their competitive adsorption. The presence of coexisting solute of the more adsorbability played a more important role than that of the lesser adsorbability. The adsorption of IDP and ATR was easier to be affected by 28.9-52.0% and 31.1-60.7% with the addition of CBD, while that of CBD was much less influenced by 3.4-18.1% and 6.9-31.8% with the presence of ATR and IDP, respectively. An adsorbability-related enhancement in desorption of the three pesticides by the co-adsorbed solute was also observed. As a result of competitive adsorption/desorption, the mobility of the pesticides estimated from soil thin-layer chromatography was altered. The results clearly illustrated that adsorbability and concentration-related alteration in adsorption/desorption and mobility will be caused by the coexistence of pesticides.

Environmental impact of two organic amendments on sorption and mobility of propachlor in soils

The purposes of this study were to understand the sorption–desorption characteristics of propachlor in three types of soils with added solid organic matters and the effect of solid organic matters on propachlor mobilization in soil microstructures. Three soil types, Eutric gleysols (EG), Hap udic cambisols (HUC), and Haplic alisol (HA), along with the lakebed sludge (SL) and pig manure compost (PMC), were used in the study. The sorption and desorption experiments were carried out using the standard batch equilibration method. Soil column leaching was performed with soil samples packed into PVC columns. Soil thin-layer chromatography was performed using soils and water mixture spread on a 0.5–0.7-mm thick layer over 20 × 10-cm glass plates. Propachlor was shown to be more mobile in EG and HUC than in HA. Application of PMC and SL to soils affected the propachlor mobilization in the soils. Using batch experiment, soil column, and soil thin-layer chromatography, we showed that addition of SL and PMC increased the sorption and decreased desorption of propachlor in the soils. Addition of PMC and SL reduced the total concentration of propachlor in the soil leachate and migration of propachlor in the soil profiles. Physicochemical properties of the three soils were analyzed and showed that the content of organic carbon (in percentage) was higher in Haplic alisol than in Eutric gleysols and Hap udic cambisols. The soil organic matter played critical roles in modifying the absorption and mobility of organic chemicals (e.g., herbicide and contaminants) in soil ecosystem.

Effect of CPC, Brij-35, and SDBS Surfactants on the Adsorption and Movement of Carbofuran in Indian Soils

Laboratory studies were conducted to determine adsorption and movement of carbofuran in aqueous surfactant-free and surfactant [(cationic, cetyl pyridinium chloride (CPC), non-ionic, polyoxyethylene lauryl ether (Brij-35) and anionic, sodium dodecyl benezene sulphonate (SDBS)] solutions of different critical micellar concentrations (1/2 × CMC, 1.0 × CMC, and 2 × CMC) in four different Indian soils using batch shake and soil thin layer chromatography (soil TLC) techniques. The measured equilibrium adsorption isotherms were in agreement with the Freundlich equation. Higher adsorption of carbofuran in both systems was observed on FRI silt loam (FSL) soil followed by Alampur silt loam (ASL), Kalai loam (KL), and Bhoran sandy loam (BSL) soils, as anticipated from Freundlich constant KF and distribution coefficient KD, in surfactant-free systems and KF* and KD* in surfactant-soil-water systems. The adsorption of carbofuran in surfactant-soil-water systems followed the order cationic > anionic > non-ionic at all CMCs studied. The Rf values obtained from soil TLC studies confirmed the above order of adsorption. The KD and KD* values were used to evaluate remediation efficiency (KD*/KD) of surfactants. Non-ionic surfactant, Brij-35, and anionic surfactant, SDBS, are favorable for remediating soil contaminated with carbofuran as KD*/KD ratio is less than 1.

Comparison of the Interactions of Aminopyralid vs. Clopyralid with Soil

Laboratory studies were conducted to compare the soil adsorption of aminopyralid and clopyralid with the use of batch-slurry and centrifugation assays. The calculated soil binding constants for both herbicides varied between the two techniques, but the centrifugation assay had a lower coefficient of variation compared to the batch-slurry assay. These results indicate that a centrifugation assay is a more accurate procedure for measuring the interaction of aminopyralid and clopyralid with soils. Aminopyralid adsorbed more tightly than clopyralid to six of the eight soils tested. AdsorptionKdvalues ranged from 0.083 to 0.364 for clopyralid and 0.106 to 0.697 for aminopyralid. Pearson correlation analysis indicated that binding of both herbicides was highly correlated to soil organic matter and texture but not to soil pH. On average, soil thin-layer chromatography indicated that aminopyralid was less mobile (Rf= 0.82) than clopyralid (Rf= 0.91), although both were mobile. These results suggest that aminopyralid will have a lower leaching potential than clopyralid. Lower potential aminopyralid soil leaching, coupled with low use rates, suggests it may be the herbicide of choice in areas where potential for leaching could be a concern.

Effect of polar-dissolved organic matter fractions on the mobility of prometryne in soil

Purpose Using two fractions of dissolved organic matter (DOM) with different polarity, we carried out the experiments with standard batch equilibration, soil column leaching, and soil thin layer chromatography to investigate the behavior of the herbicide prometryne in soils. The purpose of the study was to: (1) separate DOM into hydrophilic matter and hydrophobic acid forms and characterize their chemical properties; (2) analyze interaction between the DOM fractions and prometryne in soils.

Effect of size-fractionation dissolved organic matter on the mobility of prometryne in soil

Import of organic materials in the form of compost, sludge or plant residues introduces large amounts of dissolved organic matter (DOM) into soils. DOM as a dynamic soil component affects the behaviors of organic pollutants. Different DOM constituents may affect herbicide action in a different way. However, the process of interaction between the distinct DOM-fractions and herbicides is largely unknown. In this study, DOM was separated by size-fractionation into three molecular size groups: MW < 3500 Da, 3500 Da < MW < 14 000 Da, and MW > 14 000 Da. Effects of DOM-fractions on prometryne sorption/desorption and mobility were analyzed using approaches of batch experiments, soil column and soil thin-layer chromatography. Application of varied DOM-fractions at 50 mg DOC L −1 to the soil reduced the sorption and increased desorption of prometryne. DOM-fraction with MW > 14 000 Da appeared most effective in prometryne mobilization in the soil than any other fractions. Finally, DOM-fractions were characterized by chemical analyses, fourier transformed infrared spectroscopy (FT-IR) and excitation-emission matrices (EEMs) fluorescence spectroscopy. Our studies revealed that the high-molecular weight fraction contained more aromatic framework and unsaturated structure that was most likely the dominant factor modulating the behavior of prometryne in soils.

Adsorption and movement of carbaryl in soils: A verification of cosolvent theory and comparison of batch equilibrium and soil thin layer chromatography results

Batch equilibrium and soil thin layer chromatography (TLC) techniques were used to investigate the influence of different volume fractions of organic cosolvents (acetone and methanol) on the adsorption and movement of carbaryl in four different types of Indian soils. L-shaped isotherms were obtained for both the cosolvent–water mixtures at all f s values and were in close agreement with the Freundlich equation. Higher adsorption was observed on F.R.I. soil (FSL) followed by Alampur soil (ASL), Kalai soil (KL), and Bhoran soil (BSL) at all f s values for both the cosolvent systems as was anticipated from the K and K D values. The K and K D values also confirmed that carbaryl adsorption was higher in methanol–water mixture than acetone–water mixture and decreased with increasing f s values. The frontal R f values obtained from soil TLC studies were inversely proportional to the K and K D values for both the cosolvent systems. The higher K and K D values and lower R f values in methanol–water mixtures relative to acetone–water mixtures for all the soils indicated that acetone had a greater potential for ground water contamination compared to methanol. The adsorption data were used to evaluate the cosolvent theory for describing adsorption of carbaryl in acetone–water and methanol–water mixtures. The aqueous phase partition coefficients, K DW (mol g−1), normalized with respect to f oc for carbaryl was evaluated by extrapolating f s → 0.