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.
Highlights
Phthalate esters (PAEs) are a class of synthetic organic compounds with important environmental hormone-like activities and are the most commonly used plastic additives used to increase the flexibility of plastic polymers [1]
The results indicate that, under neutral soil conditions, an increase in lettuce leaf size occurred with increasing di (2-ethyl hexyl) phthalate (DEHP) concentration compared with the controls
Di-n-butyl phthalate (DnBP) treatment was associated with a decline in lettuce leaf size compared with the control in about half of its treatments but not related with DnBP concentrations, soil water content or soil organic matter content, especially under neutral soil conditions
Summary
Phthalate esters (PAEs) are a class of synthetic organic compounds with important environmental hormone-like activities and are the most commonly used plastic additives used to increase the flexibility of plastic polymers [1]. PAEs are present in thousands of industrial, medical, agricultural, and domestic products such as fabrics, surfactants, detergents, mulching membranes, toys, wallpaper, medical tubes, wrappers and personal care products [2,3]. They are combined physically rather than chemically with the polymer matrix so that PAE compounds can be readily released into the atmosphere, water, soil, sediments and foods in relatively large quantities because of their large-scale and worldwide use [2,4,5,6].
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