Presence, distribution and risk assessment of phthalic acid esters (PAEs) in suburban plastic film pepper-growing greenhouses with different service life.

The widespread usage of plastic film increased the content of phthalic acid esters (PAEs) in the environment, causing PAE residue in vegetables and subsequently increasing health risks to humans when consuming them. In this work, the presence, distribution and risk assessment of 15 PAEs in soils and peppers from suburban plastic film pepper-growing greenhouses were investigated. The total PAE contents in soil and pepper samples ranged from 320.1 to 971.2 µg/kg (586.3 µg/kg on average) and from 196.6 to 304.2 µg/kg (245.4 µg/kg on average), respectively. Di (2-ethyl)hexyl, dibutyl and diisobutyl phthalates (DEHP, DnBP and DiBP, respectively) were the most abundant in both soil and pepper samples. Specifically, DEHP showed the highest content in soils, while the DnBP content was the highest in peppers. The total PAE content in soils from pepper-greenhouses was much lower than in the agricultural soils mulched with plastic films, but significantly higher than in the agricultural soils from open uncovered fields. The total PAE content in peppers decreased as the service life of plastic film greenhouses increased. Correlation analysis suggested that the difference in distribution and accumulation behaviors of individual PAEs in greenhouse systems was correlated with their physicochemical properties. The non-cancer and carcinogenic risks of priority PAEs show low risks of PAEs detected in pepper and soil samples from the suburban plastic film greenhouses to human health.

Accumulation and transport patterns of six phthalic acid esters (PAEs) in two leafy vegetables under hydroponic conditions.

In this study, we investigated the accumulation and transport patterns of six phthalic acid esters (PAEs) in two leafy vegetables under hydroponic conditions. The tested PAEs included dibutyl phthalate (DBP), diethyl phthalate (DEP), diallyl phthalate (DAP), diisobutyl phthalate (DIBP), dimethyl phthalate (DMP) and benzyl butyl phthalate (BBP), and the tested vegetables included Gaogengbai and Ziyoucai. The results revealed that the six PAEs were taken up by vegetables from the solution, although their accumulation and distribution varied among PAEs. The ability of concentrating PAEs into the roots followed the order of BBP > DBP > DIBP > DAP > DEP > DMP, whereas the ability of concentrating PAEs in plant shoots had the opposite order. By analysing the fractionation of the six PAEs in vegetable roots, DMP had the largest proportion in terms of apoplastic movement, while BBP had the largest proportion in terms of symplastic movement. Correlation analyses revealed that the differences among the accumulation and distribution behaviours of the six PAEs in plant tissues were not only related to their physicochemical parameters, such as alkyl chain length and the octanol/water partition coefficient (logKow), but also related to the proportion of apoplastic and symplastic movement in the plant roots. In addition, PAEs were more readily accumulated in the Gaogengbai roots than in the Ziyoucai roots; however, the opposite trend was observed for the shoots.

Uptake, translocation and accumulation of imidacloprid in six leafy vegetables at three growth stages.

The uptake, translocation and accumulation behaviours of imidacloprid in six leafy vegetables, including Xiadi cabbage (XDC), Huaguan cabbage (HGC), Gaogengbai (GGB), Shanghaiqing (SHQ), Kangresijiqing (KRQ) and Ziyoucai (ZYC), were investigated under hydroponic conditions. Seedling stage (S-stage), rapid growth stage (R-stage) and maturation stage (M-stage) for each vegetable were considered. The root concentration factor (RCF), translocation factor (TF) and bioconcentration factor (BCF) were used to compare the difference. The results show that during 48 h of exposure, the total amount of imidacloprid taken up by the test vegetables increased with vegetable growth; however, the imidacloprid concentration in vegetable tissues varied significantly according to the variety and growth stage. For individual vegetables, imidacloprid was most easily accumulated into HGC and GGB shoots at R-stage, but into XDC, KRC and ZYC shoots at S-stage. For varieties, the ability of accumulating imidacloprid from solution to shoots seemed to follow the order of GGB > XDC > SHQ > KRQ > HGC > ZYC. Pearson's correlation analysis revealed significant negative correlations between daily transpiration and logBCF and between logRCF and logTF, indicating that the difference of uptake, translocation and accumulation behaviours of imidacloprid in vegetable varieties and growth stages may be related to the daily transpiration and the ability of concentrating imidacloprid in vegetable roots.

Comparison of uptake, translocation and accumulation of several neonicotinoids in komatsuna (Brassica rapa var. perviridis) from contaminated soils.

The accumulation of pesticides in vegetables may have serious effects on human health and ecosystems via food chains; therefore, it is of great importance to investigate the uptake and accumulation behaviours of pesticides in vegetable tissues. In the present study, the uptake, translocation and accumulation of five neonicotinoids, thiamethoxam (THIM), clothianidin (CLO), thiacloprid (THID), acetamiprid (ACE) and dinotefuran (DIN), in komatsuna (Brassica rapa var. perviridis, a vegetable) were investigated. The concentrations of neonicotinoids in vegetable tissues ranged from 0.068 ±â€¯0.002 to 29.6 ±â€¯2.5 mg/kg. During the cultivation (except for the first day), the concentration of each neonicotinoid in shoots was the highest, followed by roots and the soil. The concentrating of neonicotinoids from the soil to roots followed the order of THIM > CLO > THID > DIN > ACE, while the order of the ability of translocation neonicotinoids from roots to shoots was the just opposite. The difference in uptake and translocation behaviours of the test neonicotinoids seems to be not correlated with the octanol/water partition coefficient (logKow), water solubility or dissociation constant (pKa), but significantly correlated with molecular weight. In addition, a greater concentration of the THIM-metabolite clothianidin (M-CLO) was detected in vegetable shoots than in roots and the soil.

Uptake and translocation of imidacloprid, thiamethoxam and difenoconazole in rice plants.

Uptake and translocation of imidacloprid (IMI), thiamethoxam (THX) and difenoconazole (DFZ) in rice plants (Oryza sativa L.) were investigated with a soil-treated experiment at two application rates: field rate (FR) and 10*FR under laboratory conditions. The dissipation of the three compounds in soil followed the first-order kinetics and DFZ showed greater half-lives than IMI and THX. Detection of the three compounds in rice tissues indicated that rice plants could take up and accumulate these pesticides. The concentrations of IMI and THX detected in leaves (IMI, 10.0 and 410 mg/kg dw; THX, 23.0 and 265 mg/kg dw) were much greater than those in roots (IMI, 1.37 and 69.3 mg/kg dw; THX, 3.19 and 30.6 mg/kg dw), which differed from DFZ. The DFZ concentrations in roots (15.6 and 79.1 mg/kg dw) were much greater than those in leaves (0.23 and 3.4 mg/kg dw). The bioconcentration factor (BCF), representing the capability of rice to accumulate contaminants from soil into plant tissues, ranged from 1.9 to 224.3 for IMI, from 2.0 to 72.3 for THX, and from 0.4 to 3.2 for DFZ at different treated concentrations. Much higher BCFs were found for IMI and THX at 10*FR treatment than those at FR treatment, however, the BCFs of DFZ at both treatments were similar. The translocation factors (TFs), evaluating the capability of rice to translocate contaminants from the roots to the aboveground parts, ranged from 0.02 to 0.2 for stems and from 0.02 to 9.0 for leaves. The tested compounds were poorly translocated from roots to stems, with a TF below 1. However, IMI and THX were well translocated from roots to leaves. Clothianidin (CLO), the main metabolite of THX, was detected at the concentrations from 0.02 to 0.5 mg kg-1 in soil and from 0.07 to 7.0 mg kg-1 in plants. Concentrations of CLO in leaves were almost 14 times greater than those in roots at 10*FR treatment.