Toxicity of phthalate esters to lettuce (Lactuca sativa) and the soil microbial community under different soil conditions

Abstract

Phthalate esters (PAEs) are globally used plasticizers and typical endocrine disruptors that can readily accumulate in agricultural products and represent a substantial risk to human health via the food chain. The range of soil properties has an important influence on the expression of PAE toxicity, and the mechanisms by which soil physical and chemical properties affect the expression of toxicity of target PAEs to plants and microorganisms requires further investigation. Important soil factors affecting the eco-toxicological effects of two typical PAEs, di-n-butyl phthalate (DnBP) and bis (2-ethylhexyl) phthalate (DEHP), on lettuce (Lactuca sativa) in a spiked soil were investigated in the present study. Soil at various pH values was spiked with three PAE concentrations (1, 5 and 20 mg DnBP or DEHP kg-1 soil), organic matter contents and water holding contents to simulate the greenhouse soil environment for 30 days. Their influence on the biomass, photosynthetic pigment contents, various physiological changes and soil microbial communities was determined as endpoints. The toxicity to lettuce of DnBP was higher than that of DEHP in the soil and soil pH was the most important factor affecting their single toxicity, followed by soil organic matter content and soil moisture content in agreement with the Biolog test results. Under different soil conditions total protein, total soluble sugar and free amino acid contents were positively correlated with concentrations of the target PAEs, but leaf area, biomass, •O2- activity, vitamin C content and soil microbial diversity indices showed the opposite trend. Chlorophyll a and carotenoid contents were more inhibited by DnBP together with impacts on indices of soil microbial diversity. The results suggest that soil conditions in greenhouses directly explain the patterns of pollutant toxicity displayed and impact the quantity, quality and food safety of vegetables produced using highly intensive production systems.

Effects of Phthalate Esters on Ipomoea aquatica Forsk. Seedlings and the Soil Microbial Community Structure under Different Soil Conditions

“…DBP (99.1%) and DEHP (99.6%) certified reference materials (CRMs), assay kits (catalog number A052, inhibition and production of superoxide radical; A018, hydroxyl radical) and other analytical-grade reagents were purchased, and details of their use are as described in Ma et al [29].…”

“…Detailed information about the selected soil can be found in Ma et al [29]. The soil background concentration levels of DBP and DEHP were 0.037 ± 0.002 and 0.087 ± 0.004 mg kg −1 (dry weight (DW), freeze dry basis), respectively.…”

“…were obtained from the Chinese Academy of Agricultural Sciences in Nanjing. The storage and sterilization of the seeds and the preparation methods of glassware were as described in Ma et al [29].…”

“…Xenobiotic phytotoxicity can be demonstrated by the production of morphological, physiological, and molecular stress responses by plants [22]. PAEs can induce germination inhibition, photosynthesis blocking, biomass and nutrition (vitamin C and soluble sugar) content decline, abnormal cell division, root morphology, and metabolism in vegetables [23,24,25,26,27,28,29]. Increases in the micronucleus rate, membrane permeability, oxidative damage, and genotoxicity in plants have also been detected [22].…”

Characterization of Di-n-Butyl Phthalate Phytoremediation by Garden Lettuce (Lactuca sativa L. var. longifolia) through Kinetics and Proteome Analysis

“…The total PAE concentrations ranged from 0.14 to 2.13 mg kg −1 (mean 0.99 mg kg −1 ) in soils and from 0.15 to 6.94 mg kg −1 (mean 1.49 mg kg −1 ) in vegetables [38]. The latest study, carried out in 2018, indicated that the toxicity to lettuce of DBP was higher than that of di-(2-ethylhexyl) phthalate (DEHP) in soil, and DBP treatment is associated with a decline in lettuce leaf size, as well as chlorophyll a and carotenoid content when compared to the control lettuce plants [39].…”