Physicochemical Characterization of Agricultural Soil and Biochemical Profiling of Soil-cultivated Leafy Vegetables in Relation to Baseline Triclopyr (TCP) and 4-Chlorophenoxyacetic Acid (4-CPA) Pesticide Residues

Agricultural intensification in peri-urban belts of central India has raised concerns about the concurrent presence of physicochemical soil degradation and low-level pesticide residues in leafy vegetables that are consumed with minimal processing. The present study characterises a composite agricultural soil (0–15 cm) and seven soil-cultivated leafy vegetable species -- Amaranthus viridis, Trigonella foenum-graecum L., Corchorus olitorius L., Coriandrum sativum, Mentha arvensis, Cicer arietinum and Spinacia oleracea L. -- collected from a single agricultural field, and screens both matrices for baseline residues of 3,5,6-trichloro-2-pyridinol (TCP), the principal soil metabolite of the herbicide triclopyr, and 4-chlorophenoxyacetic acid (4-CPA), a chlorophenoxy-class plant growth regulator with herbicidal application at elevated dose. Soil texture (45.8% sand, 30.7% silt, 23.5% clay) placed the composite sample in the loam class, with a near-neutral pH (6.5), moderate cation exchange capacity (15.7 cmol(+)/kg) and organic carbon content (0.71%) consistent with regional literature ranges. Proximate biochemical profiling showed protein content ranging from 3.6–5.1 mg/g fresh weight and carbohydrate content ranging from 4.0–5.9 mg/g fresh weight across species, with Corchorus olitorius recording the highest values for both parameters and Spinacia oleracea the highest tissue moisture (92.4%). TCP and 4-CPA were detected in the composite soil at 0.167 ± 0.019 and 0.113 ± 0.015 mg/kg, respectively, and in vegetable tissue at concentrations one to two orders of magnitude lower (0.008–0.021 mg/kg TCP; below detection limit (BDL)–0.015 mg/kg 4-CPA), with detection frequencies ranging from 33.3% to 100% across species. Apparent soil-to-plant transfer ratios were consistently below unity (0.05–0.13), indicating limited but measurable translocation. A positive association was observed between tissue moisture content and residue concentration for both analytes. These findings establish a quantitative baseline against which post-remediation or seasonal monitoring data can be compared, and they are discussed in relation to reported soil-plant transfer behaviour of structurally related organic pollutants.