- Title
- Herbicide fate and behaviour in urban and agricultural soils: implications to food safety
- Creator
- Parven, Aney
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2024
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Herbicides play a vital role in controlling weeds and maintaining crop productivity in modern agriculture. However, improper use can lead to environmental, biodiversity, and food safety concerns due to potential contamination. This study evaluates the sorption-desorption, degradation, and plant uptake behaviour, followed by human and environmental health hazards of three widely used pre-emergence herbicides, dimethenamid-P, metazachlor, and pyroxasulfone in both urban and agricultural settings. Current findings reveal that the sorption kinetics of these herbicides in five soils followed a pseudo-second-order model, while Freundlich model best fitted the sorption isotherms. This indicates that these herbicides primarily partition into heterogeneous surface sites on clay minerals and organic matter (OM) before diffusing into soil micropores. It is emphasized that decomposed OM, rich in C=O and C–H functional groups, enhances herbicide sorption, whereas undecomposed or partially decomposed OM facilitates desorption. The absence of hysteresis (H = 0.27‒0.88) suggests a high propensity for herbicide desorption in soils. The leachability index (LIX < 0.02–0.64) and groundwater ubiquity score (GUS 0.02‒3.59) indicate a low to moderate potential for herbicides to leach into water bodies, impacting water quality, nontarget organisms, and food safety. Hazard quotient (HQ) and hazard index (HI) data for human adults and adolescents suggest minimal to no non-carcinogenic risks from exposure to herbicide-contaminated soils through dermal contact, ingestion, and inhalation. On the other hand, the dissipation rate constants (k, day⁻¹) positively correlate with total organic carbon (TOC), silt, clay, soil pH, and Al and Fe oxides, while sand content shows a negative correlation. Conversely, the half-life values (DT50, days) of these herbicides negatively correlate with TOC, clay, silt, soil pH, and Fe and Al oxides, but positively with sand content. Minimal impact on soil dehydrogenase activity (DHA) was observed, with urban soils showing increased DHA levels due to the influence of OM. Environmental indicators like GUS and LIX suggest that herbicides could reach groundwater, posing potential risks to nontarget biota and food safety. The human non-cancer risk evaluation shows minimal or no risks from exposure to herbicide residues in soils at 50% of initial concentrations. The study also analyzed herbicide residues in peas (pods, roots, and shoots) grown in agricultural soil (MAT) and potting mix (POM), and the levels residue were at or above EU-MRLs. The non-cancer acute health hazard index (aHI < 100%) and hazard quotient (HQ < 1) suggest no significant risk to humans from consuming peas grown in herbicide treated soils. Minimal differences in DHA and phosphatase activity (PHA) levels between treated and untreated soils indicate little impact on soil health and microbial activity, with POM showing higher DHA levels due to its higher organic matter content. This research highlights the crucial impact of pre-emergence herbicide residues on soil microbes and human health, offering vital insights for safer agricultural practices and aiding stakeholders and regulatory authorities in balancing herbicide use with environmental and human health protection.
- Subject
- pre-emergence herbicides; sorption‒desorption; dissipation; nontarget effect; soil health; food safety
- Identifier
- http://hdl.handle.net/1959.13/1513184
- Identifier
- uon:56697
- Rights
- This thesis is currently under embargo and will be available from 10.10.2025. Copyright 2024 Aney Parven
- Language
- eng
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