Investigation of Pesticide Penetration and Persistence on Harvested and Live Basil Leaves Using Surface-Enhanced Raman Scattering Mapping.

Understanding pesticide behavior in plants is important for effectively applying pesticides and in reducing pesticide exposures from ingestion. This study aimed to investigate the penetration and persistence of pesticides applied on harvested and live basil leaves. Surface-enhanced Raman scattering (SERS) mapping was applied for in situ and real-time tracking of pesticides over time using gold nanoparticles as probes. The results showed that, after surface exposure of 30 min to 48 h, pesticides (10 mg/L) penetrated more rapidly and deeply into the live leaves than the harvested leaves. The systemic pesticide thiabendazole and the nonsystemic pesticide ferbam can penetrate into the live leaves with depths of 225 and 130 μm, respectively, and the harvested leaves with depths of 180 and 18 μm, respectively, after 48 h of exposure. The effects of leaf integrity and age on thiabendazole penetration were also evaluated on live basil leaves after 24 h of exposure. Thiabendazole (10 mg/L) when applied onto intact leaves penetrated deeper (170 μm) than when applied onto damaged leaves (80 μm) prepared with 20 scrapes on the top surface of the leaves. Older leaves with a wet mass of 0.204 ± 0.019 g per leaf (45 days after leaf out) allowed more rapid and deeper penetration of pesticides (depth of 165 μm) than younger leaves with a wet mass of 0.053 ± 0.007 g per leaf (15 days after leaf out, depth of 95 μm). The degradation of thiabendazole on live leaves was detected after 1 week, whereas the apparent degradation of ferbam was detected after 2 weeks. In addition, the removal of pesticides from basil was more efficient when compared with other fresh produce possibly due to the specific gland structure of basil leaves. The information obtained here provides a better understanding of the behavior and biological fate of pesticides on plants.