# Residual Level of Chlorpyrifos in Lettuces Grown on Chlorpyrifos-Treated Soils
## 3 Results and Discussion
In this study, lettuce absorbed 0.6-3.4% of the initial concentration in the soil. The uptake of boscalid by the lettuce was higher  
Figure 2: Residual amount of chlorpyrrifos in lettuce grown in the treated soils. (**A**) Lettuce samples from field 1; (**B**) Lettuce samples from field 2.  
than that of chlorfenapyr. The water solubility of boscalid, chlorfenapyr, and chlorpyrifos were 4.6, 0.14, and 1.4 mg/L, respectively, and the log P values of these chemicals were 2.96, 4.83, and 4.7, respectively. Boscalid is more polar and water-soluble; thus, it is absorbed and translocated to the upper part of lettuce through the evaporation stream to a greater extent [29; 37]. Apart from water solubility, the systemic properties of a pesticide are critical parameters for understanding the uptake and translocation of the chemical to a plant. Chlorpyrifos is a systemic insecticide absorbed from the roots that move to the upper part of the plant. Chlorfenapyr is a limited systemic, and boscalid is a foliar fungicide; however, the systematicity of boscalid is not well known [2]. [PERSON] et al. [11] demonstrated that plant growth, concentration dependency, and duration are important parameters in understanding the transportation pattern of chlorpyrifos in cucumbers. They found that approximately 0.03% to 0.04% of the initial concentration of chlorpyrifos in the soil was transported to the cucumbers in a green house study. With regard to this report, our results were significantly different from the results suggested by [PERSON] et al. [11] due to the difference in plant species. Lettuce has wider leaves and grows quickly. The residue of chlorpyrifos in lettuce was determined as approximately 0.66-5.98% and 2.71-13.26% compared to the initial concentration in field 1 soil and field 2 soil, respectively. [PERSON] and [PERSON] [38] demonstrated that different uptake levels of prochloraz between plant species were dependent on the addition of surfactant, while 2,4-dichlorophenoxyacetic acid (2.4-D) was variable. Furthermore, they suggested that the uptake of chemicals might be correlated to the combined interactions of the active ingredient, surfactant, and the leaf surfaces as well as cuticular morphology, as they conducted foliar-sprayed treatment. According to the results of the previous study by [39], differences between [PERSON] et al. [11] and our study on the residue level of chlorpyrifos might have been caused by the different morphology of roots because of the use of pesticide pre-treated soil samples or the use of different surfactants in the formulation. As the residue levels of chlorpyrifos varied between cucumbers and lettuce, [PERSON] et al. [40] exhibited similar results, as the translocation factor of chlorpyrifos was very different when they determined the root uptake rate using Pak choi (_Brassica chinensis_) and lettuce at high concentration treatments of chlorpyrifos. [PERSON] et al. [24] concluded that RCFs and translocation were not proportional to the \(K_{\text{ow}}\) values of the compounds from the results of the uptakes of \(O\)-methylcarbamoylocyanimes and substituted ureas with different lipophilicities from a water solution by barley roots. The accumulation of non-ionic compounds by barley roots was described by the partitioning of the chemical to the root lipophilic part and uptake into the aqueous part in the roots. The lipophilic compound had a considerable partition value, but the uptake of chemicals to the polar phase was demonstrated for polar compounds. Translocation to the shoot was a passive process and was shown to have a maximum value with intermediate polarity, having log \(K_{\text{ow}}\) values of 1.5-2.0 [24; 27; 28]. The contaminant in the soil could be absorbed by soil particles and by the plant root after eluting into soil water. This means that the partitioning of the pesticide between soil particles and water as well as between soil water and the plant is important for the translocation of the pesticide to the plant.