Adsorption kinetics of pesticide in soil assessed by optofluidics-based biosensing platform

Sorption and mobility assessment of tembotrione in soils of upper, trans and middle Gangetic plain zones of India

The presence of undesired agrochemicals residues in soil and water poses risks to both human health and the environment. The behavior of pesticides in soil depends both on the physico-chemical properties of pesticides and soil type. This study examined the adsorption-desorption and leaching behavior of the maize herbicide tembotrione in soils of the upper (UGPZ), trans (TGPZ) and middle Gangetic plain zones of India. Soil samples were extracted using acetone followed by partitioning with dichloromethane, whereas liquid-liquid extraction using dichloromethane was used for aqueous samples. Residues of tembotrione and its metabolite TCMBA, {2-chloro-4-(methylsulfonyl)-3-[(2,2,2-trifluoroethoxy) methyl] benzoic acid}, were quantified using liquid chromatography-tandem mass spectrometry. The data revealed that tembotrione adsorption decreased with increasing pH and dissolved organic matter but increased with salinity. The maximum adsorption occurred at pH 4, 0.01 m sodium citrate and 4 g/L NaCl, with corresponding Freundlich constants of 1.83, 2.28 and 3.32, respectively. The hysteresis index <1 indicated faster adsorption than desorption. Leaching studies under different flow conditions revealed least mobility in UGPZ soil and high mobility in TGPZ soil, consistent with groundwater ubiquity scores of 4.27 and 4.81, respectively. Soil amendments decreased tembotrione mobility in the order: unamended > wheat straw ash > wheat straw > farm yard manure > compost. The transformation of tembotrione to TCMBA and its mobility in soil columns were also assessed.

Reusable smartphone-facilitated mobile fluorescence biosensor for rapid and sensitive on-site quantitative detection of trace pollutants

Increasing exposure to toxic pollutants highlights the need for their sensitive detection technologies that can be rapidly adapted and deployed in various settings. Optical biosensors are an excellent solution due to their outstanding features. However, the sophisticated and expensive optical design limits their scalability and actual application. Herein, an innovative reusable smartphone-facilitated mobile fluorescence biosensor (s-MFB) was built through integrating miniaturized all-fiber optical system and microfluidic system with smartphone. An asymmetric Y-shaped fiber optic coupler (Y-FOC) is constructed for simultaneous transmission of excitation light and the collected fluorescence. In particular, the incidence rays are introduced into the fiber bio-probe at a specific angle through the single-mode fiber of the Y-FOC, which enhances the evanescent wave field and the number of total internal reflections. The s-MBF showed a LOD for free Cy5.5 of 0.1 nM. Combining indirect competitive immunoassay with the s-MFB, this new assay, which achieve quantitative detection of bisphenol A and norfloxacin in 15 min with high sensitivity and reusability, substantially reduces the complexity and improves the scalability of trace pollutants detection. The adjunctive smartphone application allows on-site real-time quantitative detection, automated interpretation of reporting results, and early-warning of pollution accidents.

Novel combination of high voltage nanopulses and in-soil generated plasma micro-discharges applied for the highly efficient degradation of trifluralin

Cold plasma is considered a highly competitive advanced oxidation process for the removal of organic pollutants from soil. Herein, we describe for the first time the combination of in-soil generated plasma micro-discharges with the advantageous high voltage nanosecond pulses (NSP) towards the high-efficient degradation of trifluralin in soil. We performed a detailed parametric analysis (pulse frequency, pulse voltage, soil thickness, soil type, energy efficiency) to determine the optimum operational conditions. High trifluralin degradation was achieved even at the higher soil thickness, indicating that the production of plasma discharges directly inside the soil pores enhanced the mass transfer of plasma reactive oxygen and nitrogen species (RONS) in soil. The energy efficiency achieved was outstanding, being up to 2-3 orders of magnitude higher than those reported for other plasma systems. We identified the intermediate degradants and proposed the most dominant degradation pathways whereas a thorough exhaust gases analysis, optical emission spectroscopy (OES) and active species inhibition by using trapping agents revealed the main RONS involved. This effort constitutes a significant advancement in the "green" credentials and application of plasma-induced degradation of pollutants as it describes for the first time the removal of the highly harmful and toxic pesticide trifluralin from soil and provides a novel perspective towards the future development of cold plasma-based soil remediation technologies.

Sorption kinetics of sulfometuron-methyl in different Brazilian soils

The speed of the sorption reaction alters the bioavailability of herbicides in the soil and, consequently, the transport and transformation processes of the molecule in the environment. In this research, the sorption kinetics of sulfometuron-methyl was evaluated in different Brazilian soils in which sugarcane is grown. The sorption speed was carried out by the batch equilibrium method. The amount of sulfometuron-methyl adsorbed and remaining in the soil solution was used to build kinetic models in fifteen soils. Pearson's correlation coefficients were determined between maximum sorption capacity and soil properties. The pseudo-second-order model presented the best fit to report the sorption kinetics of sulfometuron-methyl in soils. The sorption equilibrium time varied between 69.1 and 524.7 min. The properties of cation exchange capacity (CEC), soil hydrogenionic potential (pH), and total organic carbon (TOC) affected the sorption kinetics of sulfometuron-methyl. The pH showed a negative correlation with the maximum adsorption capacity at equilibrium, while TOC and CEC positively correlated with the maximum adsorption. The results demonstrate that the sorption speed of sulfometuron-methyl varies between soils; this must be considered when defining the rate of use of the herbicide for weed control, minimizing the risk of environmental contamination.

Influence of Glyphosate Formulations on the Behavior of Sulfentrazone in Soil in Mixed Applications

The selection of weed biotypes that are resistant to glyphosate has increased the demand for its use mixed with other herbicides, such as sulfentrazone. However, when chemical molecules are mixed, interactions may occur, modifying the behavior of these molecules in the environment, such as the sorption and desorption in soil. In this study, we hypothesized that the presence of glyphosate-formulated products might increase the sorption or decrease the desorption of sulfentrazone, thereby increasing the risk of the contamination of water resources. Therefore, our work aimed to evaluate the sorption, desorption, and leaching of sulfentrazone in the soil in an isolated and mixed application with different glyphosate formulations. The sorption coefficients (Kfs) for the sulfentrazone, sulfentrazone + Roundup Ready, sulfentrazone + Roundup Ultra, and sulfentrazone + Zapp Qi foram were 1.3, 2.1, 2.3, and 1.9, respectively. The desorption coefficients (Kfd) for the sulfentrazone, sulfentrazone + Roundup Ready, sulfentrazone + Roundup Ultra, and sulfentrazone + Zapp Qi foram were 65.7, 125.2, 733.3 and 239.8, respectively. The experiments demonstrated that the sorption and desorption of sulfentrazone in combination with the other formulated glyphosate products are altered, supporting the hypothesis suggested by this work, i.e., that the presence of other molecules is a factor that affects the behavior of herbicides in the soil. This phenomenon altered the vertical mobility of sulfentrazone. Situations involving mixtures of pesticides should be evaluated in order to improve our understanding of the dynamics of these molecules and thus avoid environmental contamination.

Removal and extraction efficiency of Quaternary ammonium herbicides paraquat (PQ) from aqueous solution by ketoenol-pyrazole receptor functionalized silica hybrid adsorbent (SiNPz)

Pesticides and herbicides have been used extensively in agricultural practices to control pests and increase crop yields. Paraquat (PQT²⁺, 1,1-dimethyl-4,4-dipyridinium chloride) is one of the herbicide that belois classified as bipyridines and is used over the world. The objective of this study is to use ketoenol–pyrazole receptor functionalized silica hybrid as adsorbent for removal PQT²⁺ from aqueous solution. The adsorbent was synthesized, and characterized using scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), Thermal analysis and other techniques. Different experimental parameters such as the effect of the amount of adsorbent, solution pH and temperatures and contact times were studied. Pseudo-order kinetics models were studied, and our data followed a pseudo second order. Experimental data were analyzed for both Langmuir and Freundlich models and the data fitted well with the Langmuir isotherm model. To understand the mechanism of adsorption, thermodynamic parameters like standard enthalpy, standard Gibbs free energy, and standard entropy were studied. The study indicated that the process is spontaneous, exothermic in nature and follow physisorption mechanisms. The novelty of this study showed surface of pyrazol-enol-imine-substituted silica (SiNPz) has the ability to highlight the surface designed for efficient removal of PQT²⁺, from aqueous solutions more than other studies. The study also showed that ketoenol–pyrazole receptor can be regenerated in five cycles using HNO₃ without affecting its adsorption capacity.

Occurrence of Pesticides and Their Removal From Aquatic Medium by Adsorption

Large amounts of pesticides are used annually, and in some cases, a part of the pesticide enters the water bodies by surface runoff to form long-term residues. In the recent past, the adverse effects of pesticides on the environment and human health received serious attention by the public and the competent authorities. Various conventional methods are used to remove these pesticides from water, but those methods are either costly or typical in operation. Therefore, adsorption is considered as an ecofriendly method. The adsorbent derived from biomaterial is considered an encouraging adsorbent due to its cost-effective and high adsorption capacity. In this chapter, detailed information on different types of pesticides, their metabolites, environmental concerns, and present status on degradation methods using adsorbents will be reviewed. This chapter presents a comprehensive overview on the recent advancement in the utilization of different adsorbents for the removal of pesticides. Overall, this study assists researchers to move forward in exploring a simple and economically viable technique to produce adsorbents with outstanding physiochemical properties and excellent adsorption capacity, so that the pesticides can be removed from aquatic ecosystem.

Isotherm and kinetic studies on adsorption of oil sands process-affected water organic compounds using granular activated carbon

The production of oil from oil sands in northern Alberta has led to the generation of large volumes of oil sands process-affected water (OSPW) that was reported to be toxic to aquatic and other living organisms. The toxicity of OSPW has been attributed to the complex nature of OSPW matrix including the inorganic and organic compounds primarily naphthenic acids (NAs: C_nH_2n+ZO_x). In the present study, granular activated carbon (GAC) adsorption was investigated for its potential use to treat raw and ozonated OSPW. The results indicated that NA species removal increased with carbon number (n) for a fixed Z number; however, the NA species removal decreased with Z number for a fixed carbon number. The maximum adsorption capacities obtained from Langmuir adsorption isotherm based on acid-extractable fraction (AEF) and NAs were 98.5 mg and 60.9 mg AEF/g GAC and 60 mg and 37 mg NA/g GAC for raw and ozonated OSPW, respectively. It was found that the Freundlich isotherm model best fits the AEF and NA equilibrium data (r² ≥ 0.88). The adsorption kinetics showed that the pseudo-second order and intraparticle diffusion models were both appropriate in modeling the adsorption kinetics of AEF and NAs to GAC (r² ≥ 0.97). Although pore diffusion was the rate limiting step, film diffusion was still significant for assessing the rate of diffusion of NAs. This study could be helpful to model, design and optimize the adsorption treatment technologies of OSPW and to assess the performance of other adsorbents.

Isoelectric Bovine Serum Albumin: Robust Blocking Agent for Enhanced Performance in Optical-Fiber Based DNA Sensing

Surface blocking is a well-known process for reducing unwanted nonspecific adsorption in sensor fabrication, especially important in the emerging field where DNA/RNA applied. Bovine serum albumin (BSA) is one of the most popular blocking agents with an isoelectric point at pH 4.6. Although it is widely recognized that the adsorption of a blocking agent is strongly affected by its net charge and the maximum adsorption is often observed under its isoelectric form, BSA has long been perfunctorily used for blocking merely in neutral solution, showing poor blocking performances in the optical-fiber evanescent wave (OFEW) based sensing toward DNA target. To meet this challenge, we first put forward the view that isoelectric BSA (iep-BSA) has the best blocking performance and use an OFEW sensor platform to demonstrate this concept. An optical-fiber was covalently modified with amino-DNA, and further coupled with the optical system to detect fluorophore labeled complementary DNA within the evanescent field. A dramatic improvement in the reusability of this DNA modified sensing surface was achieved with 120 stable detection cycles, which ensured accurate quantitative bioassay. As expected, the iep-BSA blocked OFEW system showed enhanced sensing performance toward target DNA with a detection limit of 125 pM. To the best of our knowledge, this is the highest number of regeneration cycles ever reported for a DNA immobilized optical-fiber surface. This study can also serve as a good reference and provide important implications for developing similar DNA-directed surface biosensors.

Evanescent wave fluorescence biosensors: Advances of the last decade

Biosensor development has been a highly dynamic field of research and has progressed rapidly over the past two decades. The advances have accompanied the breakthroughs in molecular biology, nanomaterial sciences, and most importantly computers and electronics. The subfield of evanescent wave fluorescence biosensors has also matured dramatically during this time. Fundamentally, this review builds on our earlier 2005 review. While a brief mention of seminal early work will be included, this current review will focus on new technological developments as well as technology commercialized in just the last decade. Evanescent wave biosensors have found a wide array applications ranging from clinical diagnostics to biodefense to food testing; advances in those applications and more are described herein.