- Title
- Pesticide use in urban environment and food safety
- Creator
- Islam, Md Meftaul
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2022
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Pesticides are the most cost-effective way of pest management; nevertheless, the concern is about the non-target impacts due to their extensive and intensive use in urban agricultural and non-agricultural settings. The current research investigated the fate and behaviour of four extensively used pesticides, glyphosate, 2,4-D, chlorothalonil, and dimethoate, in terms of sorption-desorption, degradation (half-life), and plant uptake from soils to assess potential human and environmental health hazards. Mostly, the rate-determining step of pesticide sorption in urban landscape soils involved chemisorption processes through exchanging or sharing electrons that followed the pseudo-second-order kinetic model. As evidenced by the Freundlich isotherm model, pesticides get partitioned into heterogeneous surfaces of soil organic matter (OM) and clay minerals and then diffused into soil micropores. Soil OM, oxides of Al and Fe, and contents of clay and silt were positively correlated with the distribution coefficient (Kd) of pesticides in urban soils, while alkaline pH and sand content negatively correlated with Kd values. Well-decomposed soil OM, consisting of C–H and C–O functional groups, enhanced pesticide sorption, whereas partially decomposed/undecomposed OM facilitated the desorption process. Desorption of pesticides was favoured in almost all the selected urban soils due to adverse hysteresis effects. In contrast, the degradation rate constant (k) values (day−1) for the studied pesticides were inversely proportional to those of organic carbon (OC), silt, clay, and Fe and Al oxides and directly proportional to pH and sand content in soils. The half-life (DT50) values (days) of all four pesticides in five soils positively correlated with OC, clay, silt, and oxides of Fe and Al, whereas soil pH and sand content exhibited a negative correlation. The calculated values of environmental indices, groundwater ubiquity score (GUS), and leachability index (LIX), for the selected pesticides, indicate their potential portability into water bodies, affecting non-target organisms as well as food safety. The evaluation for human non-cancer risk of these pesticides, based on hazard quotient (HQ) and hazard index (HI), suggested that exposure of adults and children to soils contaminated with 50% of initially applied concentrations through ingestion, dermal, and inhalation pathways might cause negligible or no non-carcinogenic risks. In case of plant growth study, the detected leftover residue (LoR) of glyphosate, 2,4-D, chlorothalonil, and dimethoate were above EU-MRLs in almost all the spinach and lettuce samples. Multivariate analysis revealed a significant negative correlation between LoR of selected pesticides in leafy salad vegetables and soil properties, particularly OC, silt, Fe, and Al oxides. In contrast, LoR positively correlated with pH, sand and clay content. The calculated values of aHI indicated that the consumption of leafy salad vegetables grown in soils spiked at 10 times higher (D10×) than the recommended doses (DR) of dimethoate and chlorothalonil poses a potential acute health hazard (aHI >100%) to children, whereas chronic health hazards based on hazard quotient (HQ >1) pointed out the potential threat for both adults and children. Our present study, for the first time, provides awareness of the non-target impacts of pesticide contamination in urban environments so that legislators can set new guidelines for the safe application of pesticides in urban landscapes, particularly in home gardens, to ensure food safety. Therefore, pesticides should be applied judiciously at recommended concentrations in urban landscapes, mainly on impervious surfaces, to minimize their impacts on human and environmental health.
- Subject
- urban pesticide; food safety; sorption-desorption; degradation; leafy salad vegetables
- Identifier
- http://hdl.handle.net/1959.13/1513753
- Identifier
- uon:56765
- Rights
- Copyright 2022 Md Meftaul Islam
- Language
- eng
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