Leaching of the organophosphorus nematicide fosthiazate

Green and sustainable practices for an energy plant cultivation on naturally contaminated versus spiked soils. The impact of ageing soil pollution in the circular economy framework

Silybum marianum L. Gaertn. or milk thistle is an energy-produced weed that has been shown to be tolerant of heavy metal-contaminated soils. In the present study, its cultivation was studied in soils laboratory-spiked (artificial) with Cu and Zn solutions. Meanwhile, plant growing on naturally contaminated soils of Mediterranean regions, both urban and rural, was investigated. The metal concentrations spiked in artificial polluted soils were estimated to be roughly equivalent to those in naturally contaminated soils. Plants grown in artificially contaminated soils incorporated the metal added to the soils more rapidly and in higher proportions. The contamination of soil samples was carried out using different chemical reagents, salts containing the metals with oxidation number II, highlighting the fact that the reagent containing the metal is crucial regarding artificial soil pollution. Statistically significant differences were observed between the individual pollution patterns, as far as plant metals uptake concern. It was also found that the aged, contaminated soils transfer lower levels of metals to the plants. Therefore, aging or weathering of contamination alters toxicity levels in the soil environment by determining transport and uptake into the soil-to-plant system. Eventually, from the present research, it emerged the fact that in urban soils that have aged perennial pollution, the uptake of metals by plants is probably lower than in rural ones. Furthermore, with proper management, it is possible to grow plants, with low nutrient requirements, in urban soils by adopting smart, green and eco-friendly techniques, enhancing sustainable cultivation in the framework of circular economy.

Ecotoxicological risk assessment of 14 pesticides and corresponding metabolites to groundwater and soil organisms using China-PEARL model and RQ approach

Global use of pesticides brings uncertain risks to human and nontarget species via environmental matrix. Currently, various models for exposure risk assessment are developed and widely used to forecast the impact of pesticides on environmental organisms. In this study, five commonly used insecticides, seven herbicides and three fungicides were chosen to analyze the subsequent risks in groundwater in simulated scenarios using China-PEARL (Pesticide Emission Assessment at Regional and Local Scales) model. In addition, their exposure risks to soil organisms were characterized based on risk quotient (RQ) approach. The results indicated that 23.3% of the total 528 predicted environmental concentrations (PECs) of pesticides and respective metabolites in groundwater from six Chinese simulated locations with ten crops were above 10 μg L^-1. Furthermore, acceptable human risks of pesticides in groundwater were observed for all simulation scenarios (RQ < 1). Based on the derived PECs in soil short-term and long-term exposure simulation scenarios, all compounds were evaluated to be with acceptable risks to soil organisms, except that imidacloprid was estimated to be with unacceptable chronic risk (RQ = 27.5) to earthworms. Overall, the present findings provide an opportunity for a more-comprehensive understanding of exposure toxicity risks of pesticides leaching into groundwater and soil.

Stereoselective environmental fate of fosthiazate in soil and water-sediment microcosms

The stereoselective fates of chiral pesticides in the environment has been reported in many studies. However, there is little data focused on the fate of chiral fosthiazate in the soil and aquatic ecosystems at chiral view. This study investigated the stereoselective fate of fosthiazate in the soil and aquatic ecosystems using ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) and liquid chromatography tandem time-of-flight mass spectrometry (LC-TOF/MS/MS). Significant stereoselective degradation among four fosthiazate stereoisomers were found in both greenhouse soil and water-sediment microcosms. In greenhouse soil, (1R,3S)-fosthiazate degraded faster than other three stereoisomers with the half-life of 2.7 d. The fosthiazate stereisomers in the seawater-sediment microcosm degraded more rapidly than in the river water-sediment microcosm. However, (1S,3R)-fosthiazate and (1S,3S)-fosthiazate possessed shorter degradation half-lives than their enantiomers in both microcosms, with the half-lives ranging from 3.4 d to 15.8 d. Ten degradation products were identified in the water-sediment microcosms, and, six of them were reported for the first time. Oxidation and hydrolysis were confirmed as the main degradation pathways of fosthiazate in the water-sediment microcosms. Our results revealed that the (1R,3S)-fosthiazate and (1R,3R)-fosthiazate may cause more serious ecotoxicity due to the longer half-lives than the other two stereoisomers in environment.

Study on the stereoselective behaviors of fosthiazate stereoisomers in legume vegetables by supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS)

A separation and analysis method of fosthiazate stereoisomers was established utilizing supercritical fluid chromatography-tandem mass spectrometry (SFC-MS/MS) with a CHIRALPAK AD-3 column. The determination of the four fosthiazate stereoisomers could be completed within 6 min. The environmental behaviors of fosthiazate stereoisomers were studied in legume vegetables. After applying fosthiazate granules to soil, the concentrations of fosthiazate stereoisomers in the legume vegetables increased with time, reached maximum values in 7-10 days, and then decreased gradually in all legumes except for in Glycine max. No obvious dissipation behaviors were observed in Glycine max. Interestingly, the stereoselective behaviors were species-specific. A-(-), B-(-) and B-(±)-fosthiazate were preferentially enriched in Phaseolus vulgaris Linn and Vigna unguiculata, while A-(+) and A-(±)-fosthiazate preferentially accumulated in Vicia faba Linn, Pisum sativum Linn and G. max. The opposite stereoselectivity of B-(±)-fosthiazate was observed in different growth stage of G. max. No stereoselective dissipation occurred in soil.

The potential of eugenol as a nematicidal agent against Meloidogyne javanica (Treub) Chitwood

Root-knot nematodes (RKN; Meloidogyne spp.) are the most destructive plant parasites in vegetable production and their control is very challenging. This study aimed to define the nematicidal activity of eugenol on different life stages at 33.75 to 1,000 ppm doses against the root-knot nematode Meloidogyne javanica (Treub) Chitwood, 1949. This work is the first to report the effect of eugenol on egg differentiation and its vapor and sublethal doses activities. Second-stage juveniles (J2) were dead (99.5-100%) after 48 hr of exposure at a dose of 500 ppm. At this concentration, eugenol inhibited more than 70% nematode hatching. Additionally, the use of eugenol at sublethal doses reduced the number of females per gram in tomato roots in a pot test, and also inhibited egg differentiation. To the contrary, no nematostatic effects were observed in nematode motility bioassays. The phenolic monoterpenoid eugenol described herein merits further study as potential nematicide against the rootknot nematode Meloidogyne javanica.

Isolation and characterization of soil bacteria able to rapidly degrade the organophosphorus nematicide fosthiazate

Foshtiazate is an organophosphorus nematicide commonly used in protected crops and potato plantations. It is toxic to mammals, birds and honeybees, it is persistent in certain soils and can be transported to water resources. Recent studies by our group demonstrated, for the first time, the development of enhanced biodegradation of fosthiazate in agricultural soils. However, the micro-organisms driving this process are still unknown. We aimed to isolate soil bacteria responsible for the enhanced biodegradation of fosthiazate and assess their degradation potential against high concentrations of the nematicide. Enrichment cultures led to the isolation of two bacterial cultures actively degrading fosthiazate. Denaturating Gradient Gel Electrophoresis analysis revealed that they were composed of a single phylotype, identified via 16S rRNA cloning and phylogenetic analysis as Variovorax boronicumulans. This strain showed high degradation potential against fosthiazate. It degraded up to 100 mg l^-1 in liquid cultures (DT₅₀  = 11·2 days), whereas its degrading capacity was reduced at higher concentration levels (500 mg l^-1 , DT₅₀  = 20 days). This is the first report for the isolation of a fosthiazate-degrading bacterium, which showed high potential for use in future biodepuration and bioremediation applications. SIGNIFICANCE AND IMPACT OF THE STUDY: This study reported for the first time the isolation and molecular identification of bacteria able to rapidly degrade the organophosphorus nematicide fosthiazate; one of the few synthetic nematicides still available on the global market. Further tests demonstrated the high capacity of the isolated strain to degrade high concentrations of fosthiazate suggesting its high potential for future bioremediation applications in contaminated environmental sites, considering high acute toxicity and high persistence and mobility of fosthiazate in acidic and low in organic matter content soils.

Fluensulfone sorption and mobility as affected by soil type

BACKGROUND

Fluensulfone is a fluoroalkenyl chemical with activity against multiple genera of plant-parasitic nematodes. The adsorption, desorption, and mobility of fluensulfone were evaluated on multiple soils from the USA in laboratory and column experiments.

RESULTS

Adsorption data regressed to the logarithmic Freundlich equation resulted in isotherm values of 1.24 to 3.28. Soil adsorption of fluensulfone correlated positively with organic matter (0.67) and clay (0.34), but negatively with sand (-0.54). Fluensulfone soil desorption correlated to pH (0.38) and cation exchange capacity (0.44). Fluensulfone desorption from Arredondo sand soil was 26%, and from other soils ranged from 43 to 70%. In mobility experiments, fluensulfone in the leachate peaked at 3 h, gradually declining and becoming undetectable after 9 h. Recovery from leachate was 45% of the initial fluensulfone applied to the soil surface. In separate experiments, 30-cm-long soil columns were saturated with 1 L of water, and then segregated into three 10-cm sections. Fluensulfone recovery was 41, 34, 29, and 13% in Chualar sandy loam, Arredondo sand, Greenville sandy clay loam, and Tifton loamy sand, respectively, in the top 10-cm section.

CONCLUSION

Data indicated that soil organic matter and clay contents will affect sorption, mobility, and dissipation of fluensulfone. © 2017 Society of Chemical Industry.

Sorption of the nematicide fluensulfone in six UK arable soils – implications for control of the potato cyst nematode Globodera pallida

Batch adsorption experiments were performed to determine the sorption of the nematicide fluensulfone as a technical-grade and a granular formulation (as Nimitz 15G) in six UK arable soils. The Freundlich and equilibrium sorption coefficients and , respectively, were generally low. and correlated positively with soil organic matter in all instances. The sorption kinetics was similar for both forms, but the was about four times lower for Nimitz 15G than the technical-grade, suggesting concentration dependency of fluensulfone sorption. The low sorption of fluensulfone across the soils indicates that partitioning of fluensulfone to the soil liquid phase may be unlimited. Therefore, substantial availability in the soil to be effective is likely. Sorption, therefore, may not limit fluensulfone efficacy. Nonetheless, these results call for cautious use of the nematicide because leaching is possible.

Persistence of the nematicide fluensulfone in potato (Solanum tuberosum ssp. tuberosum) beds under field conditions

As part of a broader study to evaluate the efficacy of fluensulfone for control of the potato cyst nematode,Globodera pallida, two field experiments in Shropshire (at Woodcote and Howle in 2010 and 2011, respectively) England, were used to monitor the persistence of fluensulfone in potato beds treated with Nimitz 15G®(fluensulfone) at 27 kg ha−1. Fluensulfone dissipated at similar rates in the two fields, with a trend best described by a sigmoidal curve. The time to 50% dissipation (DT50) was 24.3 days at Woodcote, and 23.7 days at Howle. No differences were found between the DT50for fluensulfone and that observed for fosthiazate. The short DT50demonstrated for fluensulfone in this study is a positive attribute as this nematicide may pose a negligible hazard to the environment. However, its persistence at an effective dose may be long enough to be effective over the peak hatch period ofG. pallida.

Effective removal of nemacide fosthiazate from an aqueous solution using zero-valent iron

In this study, the removal of fosthiazate in an aqueous solution using zero valent iron (ZVI) and the related removal reaction mechanism were investigated. The results indicate that the dissipation of fosthiazate adheres to a pseudo-first order reaction law. The apparent rate constant of fosthiazate removal could be improved by increasing the ZVI dosage, control temperature and initial pH. The observed pseudo-first-order degradation rate constants (Kobs) of fosthiazate removal using ZVI were varied in the different electrolyte solutions, and were determined as follows: Kobs (MgSO4) < Kobs (KCl) < Kobs (Control) <Kobs (NaCl) < Kobs (CaCl2) < Kobs (NaNO3) < Kobs (Na2SO4). In addition, the effects of Fe(2+) and Fe(3+) ions on the fosthiazate removal were also investigated, and the fosthiazate removal efficiencies were measured as 1.3% and 5.7% with Fe(2+) and Fe(3+), respectively. The characterizations of ZVI before/after the reaction were employed to gain insight into the reaction mechanism. Finally, the main degradation products were investigated by means of an Agilent 1100 LC/MSD Ion Trap.

Soil column leaching of pesticides

In this review, I address the practical and theoretical aspects of pesticide soil mobility.I also address the methods used to measure mobility, and the factors that influence it, and I summarize the data that have been published on the column leaching of pesticides.Pesticides that enter the unsaturated soil profile are transported downwards by the water flux, and are adsorbed, desorbed, and/or degraded as they pass through the soil. The rate of passage of a pesticide through the soil depends on the properties of the pesticide, the properties of the soil and the prevailing environmental conditions.Because large amounts of many different pesticides are used around the world, they and their degradates may sometimes contaminate groundwater at unacceptable levels.It is for this reason that assessing the transport behavior and soil mobility of pesticides before they are sold into commerce is important and is one indispensable element that regulators use to assess probable pesticide safety. Both elementary soil column leaching and sophisticated outdoor lysimeter studies are performed to measure the leaching potential for pesticides; the latter approach more reliably reflects probable field behavior, but the former is useful to initially profile a pesticide for soil mobility potential.Soil is physically heterogeneous. The structure of soil varies both vertically and laterally, and this variability affects the complex flow of water through the soil profile, making it difficult to predict with accuracy. In addition, macropores exist in soils and further add to the complexity of how water flow occurs. The degree to which soil is tilled, the density of vegetation on the surface, and the type and amounts of organic soil amendments that are added to soil further affect the movement rate of water through soil, the character of soil adsorption sites and the microbial populations that exist in the soil. Parameters that most influence the rate of pesticide mobility in soil are persistence (DT50) of the pesticide, and its sorption/desorption(Koc) characteristics. These parameters may vary for the same pesticide from geographic site-to-site and with soil depth. The interactions that normally occur between pesticides and dissolved organic matter (DOM) or WDC are yet other factors that may complicate pesticide leaching behavior.The soil mobility of pesticides is normally tested both in the laboratory and in the field. Lab studies are initially performed to give researchers a preliminary appraisal of the relative mobility of a pesticide. Later, field lysimeter studies can be performed to provide more natural leaching conditions that emulate the actual field use pattern. Lysimeter studies give the most reliable information on the leaching behavior of a pesticide under field conditions, but these studies are time-consuming and expensive and cannot be performed everywhere. It is for this reason that the laboratory soil column leaching approach is commonly utilized to profile the mobility of a pesticide,and appraise how it behaves in different soils, and relative to other pesticides.Because the soil structure is chemically and physically heterogenous, different pesticide tests may produce variable DT50 and Koc values; therefore, initial pesticide mobility testing is undertaken in homogeneously packed columns that contain two or more soils and are eluted at constant flow rates. Such studies are done in duplicate and utilize a conservative tracer element. By fitting an appropriate mathematical model to the breakthrough curve of the conservative tracer selected,researchers determine key mobility parameters, such as pore water velocity, the column-specific dispersion coefficient, and the contribution of non equilibrium transport processes. Such parameters form the basis for estimating the probable transport and degradation rates that will be characteristic of the tested pesticide. Researchers also examine how a pesticide interacts with soil DOM and WDC, and what contribution from facilitated transport to mobility is made as a result of the effects of pH and ionic strength. Other methods are used to test how pesticides may interact with soil components to change mobility. Spectroscopic approaches are used to analyze the nature of soil pesticide complexes. These may provide insight into the mechanism by which interactions occur. Other studies may be performed to determine the effect of agricultural practices (e.g., tillage) on pesticide leaching under controlled conditions using intact soil cores from the field. When preferential flow is suspected to occur, dye staining is used to examine the contribution of macropores to pesticide transport. These methods and others are addressed in the text of this review.

Residues and dissipation dynamics of fosthiazate in tomato and soil

Residue dynamics of fosthiazate in tomato and soil was studied in this paper utilizing liquid chromatography with tandem mass spectrometry (LC-MS/MS). The field trial was conducted in three sites: Beijing, Liaoning, Hubei in China. Fosthiazate dissipated with the half-life 0.75-2.6 days in tomato or tomato plants and 2.5-11.6 days in soil. In the terminal residue experiment, no higher residue than 0.023 mg kg(-1) in tomato and 0.27 mg kg(-1) in soil was detected. Residues of fosthiazte in tomato were far below Japan maximum residue levels (0.2 mg kg(-1)).