Pesticide Use and Degradation Strategies: Food Safety, Challenges and Perspectives

While recognizing the gaps in pesticide regulations that impact consumer safety, public health concerns associated with pesticide contamination of foods are pointed out. The strategies and research directions proposed to prevent and/or reduce pesticide adverse effects on human health and the environment are discussed. Special attention is paid to organophosphate pesticides, as widely applied insecticides in agriculture, veterinary practices, and urban areas. Biotic and abiotic strategies for organophosphate pesticide degradation are discussed from a food safety perspective, indicating associated challenges and potential for further improvements. As food systems are endangered globally by unprecedented challenges, there is an urgent need to globally harmonize pesticide regulations and improve methodologies in the area of food safety to protect human health

Phytoremediation of cyanophos insecticide by Plantago major L. in water

Cyanophos is commonly used in Egypt to control various agricultural and horticultural pests. It is not easily hydrolyzed and thus they are highly persistent and accumulate in various aquatic compartments such as rivers and lakes. Such issues may be solved by phytoremediation, which is the use of plants for the cleanup of pollutants. Here, we tested Plantago major L. to clean water polluted with cyanophos insecticide under laboratory conditions.The biosorption capacity (K(F)) of cyanophos were 76.91, 26.18 and 21.09 μg/g for dry roots, fruit (seeds with shells) and leaves of the Plantago major L., respectively. Viable Plantago major L. in water significantly reduced cyanophos by 11.0% & 94.7% during 2 hours & 9 days of exposure as compared with 0.8% & 36.9% in water without the plantain. In water with plantain, cyanophos significantly accumulated in plantain roots and leaves to reach maximum levels after two and four hours of treatment, respectively. After 1 day, the concentration of cyanophos decreased in roots and shoots until the end of testing. Three major degradation products were detected at roots and leaf samples. Here we demonstrate that plantago major L. removes efficiently cyanophos residue in water and has a potential activity for pesticide phytoremediation

Characterizing transformation processes of environmental contaminants by multi-element isotope analysis – proving concepts and developing methods

Compound-specific stable isotope analysis (CSIA) is increasingly applied in fundamental research, environmental sciences and forensic studies. The analysis of stable isotopes may largely improve the evaluation of sources, transformation processes and sinks of organic compounds in the environment. To extend the CSIA application to new compounds and to improve the evaluation of organic pollutants transformation in the environment, this thesis focused on providing insights into the transformation of ubiquitous organic pollutants including pesticides (organophosphorus compounds (OPs), hexachlorocyclohexanes (HCHs)), plasticizers (phthalate esters (PAEs)) and substituted chlorobenzenes. Firstly, analytical challenges associated with the reproducibility and trueness of hydrogen isotope analysis of heteroatom-bearing OPs was overcome by applying the chromium based high temperature conversion system. Secondly, sample preparation procedures for extraction and clean-up of HCHs from various matrixes including water, soil, plants, milk, fish oil and pork liver were evaluated for conservation of isotopic values. The carbon, hydrogen and chlorine isotope fractionation observed in HCHs extracted from contaminated soil, plants and pork liver highlighted the potential of multi-element CSIA for investigating the transformation of persistent contaminants in food webs. The main focus of this thesis was to characterize the fundamental (bio)chemical processes of relevant organic pollutants using CSIA. To determine factors governing isotope fractionation and to characterize fundamental processes at the molecular level, the stable isotope fractionation patterns associated with (1) hydrolysis at various pH, (2) oxidation by sulfate and hydroxyl radicals, (3) biodegradation by whole cells and (4) enzymatic transformation of selected compounds were obtained under controlled laboratory conditions. The results demonstrated that CSIA has a diagnostic value for characterizing transformation mechanisms of the tested compounds. Finally, the natural attenuation of OPs by hydrolysis at a contaminated site was investigated using carbon and hydrogen isotope analysis, which delineated the potential of CSIA for field applications.Die Komponenten-spezifische Analyse stabiler Isotope (engl. CSIA) wird zunehmend in der Grundlagenforschung, den Umweltwissenschaften und in der Forensik eingesetzt. Die Analyse der isotopischen Zusammensetzung besitzt dabei ein großes Potential Quellen, Transformationsprozesse und Senken organischer Verbindungen in der Natur zu bewerten. Zur Ausweitung der Isotopenanalyse auf neue Verbindungsklassen wurden im Rahmen dieser Arbeit Studien mit organischen Modellverbindungen durchgeführt. Dabei wurden neben den als Pestizid verwendeten Organophosphaten (OPs) sowie Hexachlorozyklohexan (HCH), die als Weichmacher genutzten Phthalsäure-Ester (PAEs) und chlorierte Benzole untersucht. Es wurden Methoden für die Multiisotopenanalyse für OPs und HCHs entwickelt. Insbesondere wurde die Analyse der Wasserstoffisotopensignaturen heteroatomhaltiger organischer Verbindungen weiterentwickelt und validiert, wobei die Chrom-unterstütze Hochtemperaturpyrolyse verwendet wurde. Isotopenfraktionierungsfreie Techniken für die Extraktion und Aufreinigung von HCHs aus unterschiedlichen Matrices wurden entwickelt und für die Multiisotopenanalyse der HCHs (2H, 13C, 37Cl) aus Böden, Pflanzen, tierischen Produkten sowie Organen (z. B. Leber) eingesetzt. Die Ergebnisse dieser Versuche demonstrieren das Potential von CSIA für die Analyse von Transformationen persistenter Chemikalien innerhalb von Nahrungsketten. Isotopenfraktionierungsmuster wurden genutzt um Transformationsreaktionen wie (1) die Hydrolyse bei verschiedenen pH Werten, (2) die Oxidation durch Sulfat- und Hydroxylradikale, (3) den biologischen Abbau sowie (4) enzymatische Reaktionen zu untersuchen. Labor-Referenzexperimente wurden mit Modellkomponenten durchgeführt und die erhaltenen isotopenspezifischen Faktoren wurden zur Charakterisierung der fundamentalen Prinzipien dieser biogeochemischen Transformationsprozesse auf molekularer Ebene genutzt. Der natürliche Abbau der OPs durch chemische Hydrolyse wurde anhand der im Labor bestimmten 13C und 2H Fraktionierungsfaktoren an einem kontaminierten Standort überprüft und validiert, wodurch das Potential von CSIA zur Feldanwendung aufgezeigt wurde

Effects of Biochar in Soil and Water Remediation: A Review

In the last decades increased global environmental concerns to water and soils pollution. The main concerns are related to the contamination of the ecosystem, food security, and human health since many of the contaminants present in soil and water (residues of pesticides and antibiotics, genes of resistance to antibiotics, and heavy metals) are absorbed by plants and enter the food chain. Remediation of the contaminated water and soil to ensure sustainable water supply and food production is urgently needed. The use of biochar can have a positive effect on this remediation process. There are several studies that demonstrate the biochar’s ability to block/reduce the contaminating effect of pesticides, antibiotic residues, antibiotic resistance genes, and heavy metals. The objective of this chapter is to carry out a comprehensive review of the effect of using biochar on the availability/transmission of these contaminants to the soil and food supply chain.info:eu-repo/semantics/publishedVersio

Adsorption-Desorption Behavior and Pesticide Bioavailability of Biochar in Soil

Biochar is a porous carbon-rich substance generated by anoxic pyrolysis of biomass. Biochar has a high adsorption capacity for organic contaminants in water and soil environmental media due to its large specific surface area and surface physical and chemical characteristics. The effects of biochar application on the adsorption-desorption behavior and bioavailability of pesticides in soil are illustrated in this paper; biochar can strongly adsorb pesticides in soil due to its loose and porous properties, large specific surface area and surface energy, and highly aromatic structure. Residual pesticide pollutants are reduced, as is desorption hysteresis, which reduces pesticide desorption. Furthermore, the use of biochar reduced the absorption and efficacy of pesticides in soil. At the same time, it describes the present gaps in research on the influence of biochar on pesticide migration mechanisms and its application in pesticide pollution control, and it identifies the major scientific issues that need to be addressed. Finally, the potential application of biochar in pesticide pollution management is discussed

The interactions between xenobiotics and soil microbial communities

Excessive use and lack of appropriate disposal technology for industrial xenobiotics have resulted in the contamination of ecosystems globally impacting the self-regulating capacity of the biosphere. This often results in irreversible alterations of ecosystem’s structure and function, but the outcomes of these events on soil microbial communities (and their functional capabilities) are poorly understood. Assessing the impact of xenobiotics on soil microbial communities is of paramount importance as they play a vital role in ecosystem services and maintain soil health, which are key requirements for sustainable land use in terms of food security and environmental sustainability. Bacteria are the most abundant and diverse soil micro-flora and play a key role in the biogeochemical cycles of important elements including carbon (C), nitrogen (N), and phosphorus (P) and sulphur (S). The current work aimed to unravel the two-way interactions between xenobiotics and soil microbial communities; i.e., how soil microbial communities modulate xenobiotic persistence through biodegradation and what impacts xenobiotic have on soil microbial community’s structure and functions, with particular focus on widely used pesticides (chlorpyrifos and imidacloprid) and industrial solvents (trichloroethene). In Chapter 2, characterisation of active methanotrophs involved in trichloroethene (TCE) degradation under different methane (CH4) concentrations was evaluated. Methane (CH4) enriched methanotrophic consortia from three Australian soils (Sydney University, Victoria Park and Botany Industrial Park) were examined for their effectiveness in TCE (50μM) degradation at 1%, 10% and 33% CH4 concentration at 20oC. Only the methanotrophic consortium from Sydney University (SU) soil was able to co-metabolically degrade TCE. The (SU) methanotrophic growth and TCE degradation was accelerated under high CH4 concentration degrading up to 30% (within 2 days) and 20% (within 5 days) TCE under 33% and 10% CH4, respectively. No degradation of TCE was observed at 1% CH4 concentration or in the absence of CH4 suggesting the dependence on relatively high CH4 availability for TCE degradation. pmoA-based stable isotope probing (SIP), terminal restriction fragment length polymorphism (T-RFLP), clone library construction and sequencing of TCE degrading SU methanotroph consortium revealed the dominance of novel uncultivable Type I methanotrophs (distantly related to Methylovulum-88%) belonging to TRF-53 in TCE degradation. In Chapter 3, the effects of the pesticides chlorpyrifos (CP) and imidacloprid (IC) on soil microbial processes (e.g. biodegradation and respiration) and community structure were evaluated. Two soil treatments (from five sugarcane farms), one with no history of pesticide application (non-treated; 1H, 2H, 3H, 4H and 5H) and the other with ~20 years pesticide application (pesticide-treated; 1R, 2R, 3R, 4R and 5R), were used in this study. MicroRespTM, q-PCR and T-RFLP analyses were combined to explore the relationship between pesticide degradation and soil microbial communities in soils spiked (3 times) with 10 mg/kg of CP or IC, under lab conditions. The results showed that the half-lives of CP decreased with application frequency and were 23-47, 8-20 and 3-17 days following the first, second and third application, respectively (for soils from five sugarcane farms). In particular, the soils from 4R, 4H and 5R showed enhanced CP degradation even when not exposed to CP for last 13 years due to legacy effect of the pesticide. Parallel analyses of IC degradation (10 mg/kg) showed high persistence of this pesticide in soil where repeated application increased half-lives from 30-60 days for the first treatment to 45-65 days for second treatment. The application of both pesticides (CP and IC) reduced soil respiration (basal and substrate-induced) between 7-76% with the lowest respiration found in 5R and highest in 1R after the pesticides treatment, indicating that application of pesticides had an adverse impact on soil functional activity. The molecular analyses showed that both CP and IC significantly altered the soil bacterial community structure and reduced diversity, evenness and richness. In Chapter 4, sequential soil and liquid culture enrichments enabled the isolation of six bacterial CP degraders with sequence homologies to Xanthomonas sp. (3), Pseudomonas sp. (1), Rhizobium sp. (1) and Lysobacter sp. (1). The efficacy of the isolated strains: Xanthomonas sp. 4R3-M1, Pseudomonas sp. 4H1-M3 and Rhizobium sp. 4H1-M1 were further investigated for biodegradation of CP and its primary metabolic product, TCP (3,5,6-trichloro-2-pyridinol). The results indicated that all three bacterial strains utilised CP (10 mg/l) and TCP (as CP degradation product) in mineral salt media (MSM) as a sole source of C and N. Bacterial strains Xanthomonas sp. 4R3-M1 and Pseudomonas sp. 4H1-M3 could also degrade 10 mg/l TCP as a sole C- and N-source, when provided externally. Thus, these bacterial strains promise to be effective in practical application of bioremediation of both CP and TCP. In Chapter 5, using next-generation sequencing, the structure and potential functions of bacterial communities in pesticide-treated and non-treated reference sites was compared at finer levels. Across all soils, the functional beta diversity was correlated with taxonomic diversity indicating possible linkages between the structure and functioning of soil microbial communities. The pesticide-treated sites had higher relative abundance of Proteobacteria and Bacteroidetes, with Archaea exhibiting the opposite pattern. Metagenomic analysis revealed increases in the relative abundance of genes associated with key specialised functions (iron acquisition and metabolism, motility, cell signalling, stress response) at pesticide-treated sites. The results suggested impacts of long-term pesticide application on soil microbial community composition and potential functions. Despite, a CP legacy effect, no marked difference was observed in abundance of genes related to P-metabolism between pesticide-treated and non-treated sites. Overall, the results supported taxonomic and functional adaptations in the soil microbial communities following pesticide treatment. Overall, this study provides the novel insights into the interaction between xenobiotics and soil microbial communities both at structural (diversity, community structure) and functional (degradation) levels and should be considered in developing new bioremediation technologies and agronomic practices such as number and frequency of pesticide applications

Optimizing The Remediation Of Organophosphorus Pesticide Profenofos From Water Using Activated Date Pits: Mechanistic Studies

The aim of the study was to examine the efficiency of date pits as an adsorbent to remove the organophosphate pesticide profenofos from wastewater. Various adsorption isotherms models namely Langmuir isotherm, Freundlich isotherm, Dubinin-Radushkevich isotherm and Temkin isotherm models were examined in order to understand the interactions between the adsorbate (profenofos pesticide) and the prepared adsorbents. In addition, thermodynamic adsorption was carried out to determine the homogeneity and spontaneous of the adsorbents. In the first phase of the study, three types of adsorbents namely roasted date pits, activated date pits and nano-activated date pits were prepared from the date pits collected from different sources. Different physical and chemical characterizations were studied such as scanning electron microscopy (SEM), Fourier transform infrared (FTIR), BET surface area, pore radius and pore volume. The surface area of the nano-activated date pit was the highest 485.441 m2/g. Moreover, the pore volume and pore radius were also the highest for the nano-activated date pits with values 0.338 cm3/g and 17.8 Å, respectively. Therefore, nano-activated date pits have resulted in high removal percentage and removal capacity of profenofos from aqueous solution. Based on adsorption isotherm model, the values of R2 was the highest for the nano-activated date pits. The adsorption maximum capacity (qm) increased with temperature and was maximum for the nano-activated date pit following Langmuir adsorption isotherm model. In the case of roasted date pit and activated date pit, the adsorption fitted the Freundlich model. Thermodynamic parameters showed a negative ΔG for all three adsorbents and the value increased with temperature. The ΔH value was positive for the three adsorbents and was the highest for roasted date pit (23.59 KJmol-1); resulting in an endothermic reaction. Whereas, the value of ΔS was negative for the three adsorbents and was the highest for nano-activated date pits (-83.5 Jmol-1)