Adsorption-desorption and hysteresis phenomenon of tebuconazole in Colombian agricultural soils: Experimental assays and mathematical approaches

Adsorption and mineralization of metalaxyl-m and chlorpyrifos in irrigated Mediterranean soil under the effects of salinity

To evaluate the effects of salinity on the fate of pesticides in a Mediterranean irrigated system, experiments were carried out under laboratory conditions to determine the adsorption, desorption, and mineralization of chlorpyrifos (CPF) and metalaxyl-M (MET) in a soil sample from an irrigated field in northern Tunisia. Adsorption/desorption isotherms and mineralization kinetics data were obtained over a realistic range of salinities via batch equilibrium and incubation techniques. On the basis of the experimental results, MET has a lower sorption capacity than CPF does, and the adsorption data for both compounds were better fitted by the Freundlich equation, with Kf values of 0.477, 0.486, 0.426, 0.444 and 0.474 L kg-1 for MET and 38.994, 39.084, 40.644, 44.055 and 45.185 L kg-1 for CPF at salinities of 0, 1, 2, 5 and 10 g L-1, respectively. According to the mineralization experiments, increasing salinity increased the half-lives of both pesticides. For MET, the DT50 values in unsterilized soil were 206.68, 220.74, 222.16, and 238.73 days, and those in sterilized soil were 2772.58, 4077.33, 6301.33, and 8664.33 days at salinities of 0, 1, 2, 5, and 10 g L⁻1, respectively. For CPF, the DT50 values were 115.52, 138.62, 157.53, and 177.73 days in unsterilized soil and 346.57, 533.19, 693.14, and 990.21 days in sterilized soil. In terms of leaching behavior, the calculated groundwater ubiquity score (GUS) values for the MET and CPF indicate that the MET is classified as a leacher and that the CPF is classified as a nonleacher.

Empirical model to assess leaching of pesticides in soil under a steady-state flow and tropical conditions

Abstract

An empirical model of leaching of pesticides was developed to simulate the concentration of fungicides throughout unsaturated soil. The model was based on chemical reactions and the travel time of a conservative tracer to represent the travel time required for water to flow between soil layers. The model's performance was then tested using experimental data from dimethomorph and pyrimethanil applied to the soil under field and laboratory conditions. The empirical model simulated fungicide concentration on soil solids and in soil solution at different depths over time (mean square error between 2.9 mg2 kg-2 and 61mg2 kg-2) using sorption percentages and degradation rates under laboratory conditions. The sorption process was affected by the organic carbon, clay, and the effective cation exchange capacity of the soil. The degradation rate values of dimethomorph (0.039 d-1-0.009 d-1) and pyrimethanil (0.053 d-1-0.004 d-1) decreased from 0 to 40 cm and then remained constant in deeper soil layers (60-80 cm). Fungicide degradation was a critical input in the model at subsurface layers. The model was determined to be a reliable mathematical tool to estimate the leachability of pesticides in tropical soil under a steady-state flow. It may be extended to other substances and soils for environmental risk assessment projects.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13762-023-05038-w.

Sorption and desorption of epiandrosterone and cortisol on sewage sludge: Comparison to aquatic sediment

Steroids have aroused global concern due to their potent endocrine-disrupting effects. Androgens and glucocorticoids are the most abundant species in sewage; however, our understanding of their fate and risks from the source to environmental sinks remains elusive. This study compared the sorption-desorption characteristics of epiandrosterone (EADR) and cortisol (CRL) in sewage sludge and aquatic sediment, and the surface and molecular interactions were tentatively investigated through infrared spectroscopy and the fluorescence excitation-emission matrix. The results showed that the sorption capacities of EADR and CRL in the sludge were 4015 L/kg and 81.17 L/kg, respectively, which are much larger than those in the sediment (EADR: 78.77 L/kg, CRL: 6.39 L/kg); 0.02%-1.2% of EADR and 0.2%-14.5% of CRL could be desorbed from sludge, while the desorption ratios were even lower in the sediment. The high organic content in the sludge might contribute to the larger sorption capacities, while the weak interaction between steroids and organic matter could lead to larger desorption potential. The sediment contained more mineral content and featured a larger specific surface area, which could be responsible for the greater desorption hysteresis for EADR and CRL. These results will help to better understand the potential risk of sewage sludge-associated steroids and their distribution in sediment-water systems.

Adsorption and desorption characteristics of arsenic in calcareous soils as a function of time; equilibrium and thermodynamic study

Irrigation of carbonate-rich agricultural soils with arsenic (As)-contaminated water leads to the accumulation of As in these soils. In this regard, there is an opportunity to adsorb and fix the As in soil and decrease the As transportation to the plants and subsequently the human food chain. So, the present study aimed to investigate the adsorption-desorption characteristics of As in calcareous soils and the potential of As fixation over time. First, to achieve this purpose, 53 soil samples were gathered from the study site and after the laboratory analysis, the soils were categorized into four groups based on their physicochemical properties. Then, four representative samples of these groups were selected, namely soil 1, soil 2, soil 3, and soil 4. Afterward, the As adsorption-desorption was investigated in a lab-scale batch experiment. Next, the effect of age was assessed by incubating the As-adsorbed soils for 60 days, and to study the impact of temperature, the adsorption was performed at four temperature levels (10, 20, 30, and 40 °C). Finally, the isotherm models were fitted to experimental data, and the amount of loosely and tightly held As was quantified. Results revealed that the As adsorption isotherms were L-type, in which As adsorption increased with the increase of As loading. The double-site Langmuir (DSL) estimated that a limited amount of As was adsorbed on high-energy surfaces and a large amount of As was adsorbed on low-energy surfaces. Desorption results showed that a significant amount of As desorbed immediately; however, the desorption significantly decreased with the increase of age, especially at low equilibrium concentrations. By aging the loosely held As transformed into non-labile forms so that in soils 1, 2, 3, and 4, the fraction of As adsorbed on high-energy surfaces increased from 72.5, 93.2, 63.2, and 123 mg/kg to 167, 141, 70.6, and 196 mg/kg, respectively, and the fraction of As adsorbed on low-energy surfaces decreased from 397, 256, 202, and 317 mg/kg to 182, 238, 173, and 172 mg/kg, respectively (after aging for 60 days). Aging proved to be a promising solution for decreasing As transport into the human food chain and could be employed for crops with longer irrigation cycles. ΔH_ad values were positive and varied from 9.26 to 13.0 kJ/mol, confirming the endothermic nature of adsorption. ΔG_ad values were negative and varied from - 18.8 to - 22.8 kJ/mol at all temperatures, demonstrating the spontaneous nature of adsorption.

Removal of lead and chromium from solution by organic peels: effect of particle size and bio-adsorbent

A variety of organic wastes can be used in innovative methods to treat water pollution through the adsorption process. In this work, we evaluated the effect of particle size (500-2000, 250-500, and less than 250 μm) and bio-adsorbent (orange, potato, and passion fruit peels) on the removal of lead and chromium from solution. The size and type of peels affected the capacity to adsorb metal ions (p < 0.05). Passion fruit peel had the highest metal adsorption, followed by orange and potato, since the cation exchange capacity (217.70 ± 39.57 cmol (+) kg-1) and the specific surface area (141.10-1095.29 cm2 g-1) were higher in the passion fruit rind. The size of the adsorbent did not affect the organic matter, ash, exchange capacity, surface chemistry, or pH of the peels. However, these properties differed among the bio-adsorbents (p < 0.05). The Freundlich equation explained the adsorption of the metallic ions on the orange rind and of lead on the passion fruit. The linear model was the best fit for the adsorption isotherms of the metals on potato peel. The adsorption of chromium on the passion fruit had a maximum adsorption capacity of 3.3 mg g-1. These results indicate that plant waste materials, especially passion fruit peel, have the potential as feasible and low-cost adsorbents in pilot studies for the treatment of polluted water.

Mechanisms of Tebuconazole Adsorption in Profiles of Mineral Soils

The study attempted to identify the soil components and the principal adsorption mechanisms that bind tebuconazole in mineral soils. The KF values of the Freundlich isotherm determined in 18 soils from six soil profiles in batch experiments after 96 h of shaking ranged from 1.11 to 16.85 μg1-1/n (mL)1/n g-1, and the exponent 1/n values from 0.74 to 1.04. The adsorption of tebuconazole was inversely correlated with the soil pH. Both neutral and protonated forms of this organic base were adsorbed mainly on the fraction of humins. The adsorption of the protonated form increased in the presence of hydrogen cations adsorbed in the soil sorption sites. Fourier transform infrared spectroscopy coupled with the molecular modeling studies and partial least squares regression analysis indicated that the tebuconazole molecule is bound in the organic matter through the formation of hydrogen bonds as well as hydrophobic and π-π interactions. Ion exchange was one of the adsorption mechanisms of the protonated form of this fungicide. The created mathematical model, assuming that both forms of tebuconazole are adsorbed on the organic matter and adsorption of the protonated form is affected by the potential acidity, described its adsorption in soils well.

Environmental disappearance of acetochlor and its bioavailability to weed: A general prototype for reduced herbicide application instruction

The consecutive application of herbicide acetochlor has resulted in the widespread drug resistance of weeds and the high risks to environment and human health. To assess environmental behaviors and minimal dosage of acetochlor application in the realistic soil, we systematically investigated the acetochlor adsorption/desorption, mobility, leaching, degradation, weed bioavailability and lethal dosage of acetochlor in three soil types including Nanjing (NJ), Yancheng (YC) and Yingtan (YT). Under the same conditions (60% moisture and darkness), acetochlor had a half-life of disappearance 3 days in NJ, 4.9 days in YC and 25.7 days in YT soils. The HRLC-Q-TOF-MS/MS analyses identified ten metabolites and eight conjugates generated through dealkylation, hydroxylation, thiol conjugation and glycosylation pathways. The acetochlor adsorption to soils ranked in the order of YT > YC > NJ and was committed to the Freundlich model. By examining the effects of soil moisture, microbial activity, illumination/darkness, etc. on acetochlor degradation in soils, we showed that the chemical metabolisms could undergo multiple processes through soil microbial degradation, hydrolysis or photolysis-mediated mechanisms. The longitudinal migration assay revealed that acetochlor leaching ability in the three soils was YT > YC > NJ, which was negatively associated with the order of adsorption behavior. Four kinds of weed were grown in the acetochlor-contaminated NJ soil. The lethal concentrations for the weed plantlets were 0.16-0.3 mg/kg, much lower than the dosage of realistic field application. Overall, our work provided novel insights into the mechanism for acetochlor behaviors in soils, the natural degradation process in the environment, and the lethal concentration to the tested weed plants.

Physiochemical assessment of environmental behaviors of herbicide atrazine in soils associated with its degradation and bioavailability to weeds

Atrazine residue in soil is one of the serious environmental problems and continues to risk ecosystem and human health. To address the environmental behaviors and dissipation of atrazine and better manage the application of atrazine in reality, we comprehensively investigated the adsorption and desorption, migration ability, and vanishing of atrazine in three distinct soils in China including Jiangxi (JX, pH 5.45, TOC 0.54%), Nanjing (NJ, pH 6.15, TOC 2.13%), and Yancheng (YC, pH 8.60, TOC 0.58%) soils. The atrazine adsorptive capacity to the soils was arranged in the order of NJ > YC > JX. The leaching assay with profiles of the soils showed strong migration, suggesting it had a high bioavailability to weeds and potential for underground water contamination. We further investigated the effects of environmental factors such as soil moisture, microbial activity and photolysis on atrazine degradation and showed that the degradation of atrazine in the soil mainly underwent the abiotic process, most likely through hydrolysis and photolysis-mediated mechanisms, and to less extend through soil microbial catabolism. Using HRLC-Q-TOF-MS/MS and by comparing the measured and theoretical m/z values and fragmentation data, ten metabolites comprising eight degraded products and two conjugates were characterized. Atrazine existing in the soils and sprayed coordinately blocked the growth of three common weeds, which prompted us to use the minimal atrazine in practice to control the waste of the pesticide and its impact on the environment. Overall, our work provided an insight into the mechanisms for the degradation of atrazine residues in the soils and contributed to the environmental risk assessment of the pesticide and management in its application control in the crop rotation and safe production.

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.

Sorption and desorption behaviors of triphenyl phosphate (TPhP) and its degradation intermediates on aquatic sediments

As triphenyl phosphate (TPhP) can biodegrade extensively in sediments, researches should further the understanding of the fate and transport of TPhP and its degradation intermediates in the environment. Therefore, the sorption/desorption behaviors of TPhP, diphenyl phosphate (DPhP) and phenyl phosphate (PhP) on sediments were investigated. The kinetic process was well-fitted by pseudo-second-order model, suggesting that chemisorption was involved. And the Langmuir model could describe the sorption isotherms of TPhP and DPhP well except for PhP. The redundancy analysis revealed that the sorption amount had a positive correlation with sediment organic matter, zeta potential and C/H of sediments. Besides the sorption/desorption behaviors were greatly influenced by the physicochemical properties of the sorbates. PhP with high molecular electrostatic potential (0.132 e⁰) was prone to protonation and formed hydrogen bonds, leading to higher sorption. Furthermore, hydrophobicity, π-π interactions, Lewis acid-base interaction and hydrogen bonding were involved in the sorption process and resulted in nonlinear sorption isotherms. TPhP, DPhP and PhP exhibited apparent desorption hysteresis on the sediments. Sediments with organic matter removed, which have complex pore distributions, exhibited more hysteresis. These results may contribute to the risk assessment and fate modeling of TPhP and its degradation products in sediments.

Factors affecting coupled degradation and time-dependent sorption processes of tebuconazole in mineral soil profiles

This laboratory degradation and adsorption study aimed to determine the tebuconazole degradation parameters for 6 profiles of Polish mineral soils and to find links between the tebuconazole degradation rate, its adsorption, soil microbial activity and other significant soil properties. The values of the adsorption distribution coefficient K_d, obtained in batch experiments after 96 h of shaking were in the range of 6.2-34.6 mL g^-1. In both batch experiments and incubation experiments at 20 °C, the typical course of adsorption processes was observed, an initial rapid stage followed by a slow stage. In 3 of the 18 soils examined, adsorption was not reached within 51 days. The range of the half-life values was 201-433 days for the Ap horizon and up to 3904 days for subsoils, which were estimated using the two-site nonequilibrium adsorption model coupled with first-order degradation for dissolved and adsorbed pesticide. It was found that modeling the degradation of tebuconazole on the basis of the coefficients of microbial biomass activity for topsoil and two subsoils explained almost 96% of the variance of the estimated pore water degradation rate coefficients in examined soils. The degradation rate was also negatively correlated with the amount adsorbed in the time dependent adsorption sites. This fraction was the least available for soil microorganisms because it was strongly adsorbed in soil pores with a radius <2.5 nm, determined from the H₂O desorption isotherm. The degradation rate was also affected by the ratio of the water content in soil during degradation experiments to the water content at field capacity. The results indicated that degradation occurred in the soil liquid phase only.

Enhanced fluoride uptake by bimetallic hydroxides anchored in cotton cellulose/graphene oxide composites

A novel hybrid nanomaterial was synthesized by embedding the bimetallic Zr and La (hydro)xides onto the cotton cellulose/graphene oxide composites (CC/GO composites), forming the Zr-La-CC/GO nanocomposites. Selective uptake of fluoride onto the Zr-La /GO hybrids in multiple competitive environments were evaluated. Morphological characteristics of Zr-La-CC/GO nanocomposites reflected the well distributions of embedded Zr and La hydroxides in the nanocomposites. Results also indicated that the encapsulated bimetallic hydroxides in Zr-La-CC/GO hybrids exhibited extremely high fluoride adsorption capacity and stability. XPS investigation exhibited the strong ZrF and LaF bonds in spent Zr-La-CC/GO nanocomposites, and the bonds were weakened at higher pH, which was consistent with the adsorption results. In addition, CC/GO composites using as the host could also exert the strong shielding effect to improve the stability of embedded La and Zr species so as only a low La dissolution (<4.2%) and almost no Zr leaching (0.1%) were observed in high HA concentration. What's more, the Zr-La-CC/GO nanocomposites have also shown great potential application for defluoridation in field.

Adsorption and Desorption of Carbendazim and Thiamethoxam in Five Different Agricultural Soils

The adsorption and desorption behaviors of carbendazim (CBD) and thiamethoxam (TMX) were systematically studied in five different agricultural soils. The adsorption and desorption isotherms of CBD and TMX in the five different soils were fitted well by the Freundlich model. The Freundlich adsorption coefficient (K_f^ads) and Freundlich desorption coefficient (K_f^des) of CBD in the five different soils were 1.46-19.53 and 1.81-3.33, respectively. The corresponding values of TMX were 1.19-4.03 and 2.07-6.45, respectively. The adsorption affinity and desorption ability of the five different soils for CBD and TMX depended mainly on soil organic matter content (OMC) and cation exchange capacity (CEC). Desorption hysteresis occurred in the desorption process of CBD and TMX in the five different agricultural soils, especially for TMX. It is concluded that the adsorption-desorption ability of CBD was much higher than that of TMX in the five different agricultural soils, which was attributed to soil OMC and CEC.

Uptake and distribution of fluopyram and tebuconazole residues in tomato and bell pepper plant tissues

The present study describes the uptake and distribution of fungicides, fluopyram, and tebuconazole in tomato and bell pepper plant tissues from the soil drench application of their combination product fluopyram17.7% + tebuconazole 17.7%. For extraction and cleanup of fluopyram, its metabolite fluopyram benzamide, and tebuconazole samples, the QuEChERS method was used in conjunction with LC-MS/MS. The limit of detection (LOD) and limit of quantification (LOQ) of the method determined were 1.5 μg kg^-1 and 0.005 mg kg^-1, respectively, and recoveries of all analytes from sample matrices remained within the acceptable range of 70-120%. Rapid uptake of the fungicides by tomato and bell pepper plants was observed from the first day onwards. In the tomato plant, the major part of the fungicides accumulated in the roots, whereas in bell pepper plant, it accumulated both in the roots and in the leaves. Accumulation of fluopyram and tebuconazole residues was lowest in tomato and bell pepper fruits which were much below their respective maximum residue limits (MRLs). The highest residue concentration of fluopyram and tebuconazole in tomato fruits was 0.060 and 0.009 mg kg^-1; the corresponding values in bell pepper fruits were 0.080 and 0.013 mg kg^-1. In field soil, fluopyram residues were 3.18-3.570 mg kg^-1 initially which dissipated at the half-life of 36 days. Tebuconazole concentration was 1.57-1.892 mg kg^-1 initially, and it dissipated at the half-life of 44.5-49.5 days. The major metabolite of fluopyram, fluopyram benzamide, was detected in plant tissues as well as in soil, and remained within 12% of the parent compound. The results of the study indicated that fluopyram and tebuconazole are less likely of entry into food chain through intake of tomato and bell pepper fruits if these crops are grown on soil contaminated with these fungicides.

Using Qmsax* to evaluate the reasonable As(V) adsorption on soils with different pH

As a toxic metalloid element, arsenic (As) derived from human activities can pose hazardous risks to soil and water. The bioavailability of arsenic is influenced by its behavior, in particular its adsorption-desorption in the soil environment. The maximum adsorption amount (Q_max) calculated from Langmuir equation is an important parameter to estimate the adsorption capacity of adsorbents. However, the soil is a more complicated system compared with specific adsorbents. Thus, in this study, we tried to find a more reasonable parameter (Q_max^*) to evaluate the adsorption capacity of soils. Eighteen Chinese soil samples with different pH were used for adsorption-desorption experiments. The maximum As(V) adsorption capacity calculated through Langmuir fitting for 18 samples were ranged from 50.25 (S13) to 312.50 (S4) mg kg^-1. Besides, Q_max was highly related with soil pH. Using the difference value of adsorption amount and desorption amount to indicate the amount of non-electrostatic adsorption of As(V) onto soils, calculated the maximum adsorption amount of non-electrostatic adsorption (Q_max^*). The average Q_max^* of acidic and neutral soils was 162.18 mg kg^-1 whereas that for alkaline soils it was only 79.52 mg kg^-1. The result from multiple linear regression analysis showed Q_max^* was strongly influenced by Fe_ox and clay contents. Furthermore, hysteresis index (HI) in the As(V) desorption varied from 0.83 (S13) to 1.82 (S6). The results further indicated the risk of secondary pollution originating from the desorption process cannot be ignored.