Integrated Analysis of Pollution Characteristic and Ecotoxicological Effect Reveals the Fate of Lithium in Soil-Plant Systems: A Challenge to Global Sustainability.

Lithium, as an emerging contaminant, lacks sufficient information regarding its environmental and ecotoxicological implications within soil-plant systems. Employing maize, wheat, pea, and water spinach, we conducted a thorough investigation utilizing a multispecies, multiparameter, and multitechnique approach to assess the pollution characteristics and ecotoxicological effects of lithium. The findings suggested that lithium might persist in an amorphous state, altering surface functional groups and chemical bonds, although semiquantitative analysis was unattainable. Notably, lithium demonstrated high mobility, with a mild acid-soluble fraction accounting for 29.66-97.02% of the total, while a minor quantity of exogenous lithium tended to be a residual fraction. Plant analysis revealed that in 10-80 mg Li/kg soils lithium significantly enhanced certain growth parameters of maize and pea, and the calculated LC50 values for aerial part length across the four plant species varied from 173.58 to 315.63 mg Li/kg. Lithium accumulation in the leaves was up to 1127.61-4719.22 mg/kg, with its inorganic form accounting for 18.60-94.59%, and the cytoplasm fraction (38.24-89.70%) predominantly harbored lithium. Furthermore, the model displayed that growth stimulation might be attributed to the influence of lithium on phytohormone levels. Water spinach exhibited superior accumulation capacity and tolerance to lithium stress and was a promising candidate for phytoremediation strategies. Our findings contribute to a more comprehensive understanding of lithium's environmental behavior within soil-plant systems, particularly within the context of global initiatives toward carbon neutrality.

Effects of earthworms on antibiotic resistance genes in different soil-plant systems.

Earthworms play an important role in the soil environment. To explore the difference in earthworms influence on various media in different soil-plant systems, the abundance of tetracycline, sulfonamide and quinolone resistance genes and the structure of the bacterial community were analysed from five different media including non-rhizosphere soil, rhizosphere soil, phyllosphere, root endophytes and earthworm intestine by real-time quantitative PCR and high-throughput 16S rRNA sequencing. Studies have shown that earthworms can reduce the absolute abundance of antibiotic resistance genes (ARGs) in non-rhizosphere soil. Root endophytes in the soil-cabbage system and rhizosphere soil in the soil-setaria system had the same findings. Earthworms can change the bacterial community structure, especially that of Proteobacteria and Cyanobacteria in the phyllosphere and root endophytes. Redundancy analysis (RDA) results that bacterial community change was the main factor affecting ARGs. In addition, earthworms increased the proportion of Cyanobacteria in root endophytes, and Cyanobacteria was significantly positively correlated with sul3. This study provides a scientific basis for controlling the migration and diffusion of ARGs and reducing environmental risks in soil-plant systems in the future.

Phthalate esters and their metabolites in paired soil-crop systems from farmland in major provinces of eastern China: Pollution characteristics and implications for human exposure.

The extensive application of phthalate esters (PAEs) as plasticizers has raised considerable concern regarding their environmental load, but the associated occurrence of PAE metabolites has often been ignored. The soil-plant system is a vital source of human exposure to PAEs via crop intake. Here, paired soil-plant samples were collected from eastern China to investigate the occurrence characteristics of seven PAE congeners and two primary monoester phthalate metabolites (mPAEs) in farmland. The detection frequencies of PAEs and mPAEs in the investigated soil-plant systems were 100 %. The total concentrations of PAEs in the collected soil and plant samples ranged from 0.07 to 1.83 mg/kg (dw) and from 3.9 to 24 mg/kg (dw), respectively. Moreover, di-(2-ethylhexyl) phthalate, diisobutyl phthalate and di-n-butyl phthalate were the predominant PAE congeners in the farmlands of eastern China, collectively accounting for >90 % of the total concentration of PAEs. In addition, the total concentrations of the two mPAEs were markedly higher in plant samples (49 ng/g dw to 549 ng/g dw) than in soil samples (3 ng/g dw to 22 ng/g dw), indicating that PAEs are readily metabolized in plants. The hazard index (HI) values of all PAEs in all crops were <1, demonstrating that the risks of PAEs in the crops were acceptable. However, the daily intake of mPAEs from the consumption of cabbage was higher than or comparable to that of some PAEs (such as di-n-octyl phthalate). This highlights the importance of taking metabolites into consideration in further environmental investigations and risk assessments of PAEs.

Effects of microplastics on cadmium accumulation by rice and arbuscular mycorrhizal fungal communities in cadmium-contaminated soil.

Both microplastics (MPs) and cadmium (Cd) are common contaminants in soil-rice systems, but their combined effects remain unknown. Thereby, we explored the effects of three MPs, i.e., polyethylene terephthalate (PET), polylactic acid (PLA), and polyester (PES), on Cd accumulation in rice and the community diversity and structure of arbuscular mycorrhizal fungi (AMF) in soil spiked with or without Cd. Results showed that 2% PLA decreased shoot biomass (-28%), but PET had a weaker inhibitive effect. Overall, Cd alone did not significantly change shoot and root biomass and increased root biomass in combination with 0.2% PES. MPs generally increased soil Cd availability but decreased Cd accumulation in rice tissues. Both MPs and Cd improved the bioavailability and uptake of Fe and Mn in rice roots. MPs altered the diversity and community composition of AMF, depending on their type and dose and co-existing Cd. Overall, 2% PLA caused the most distinct changes in soil properties, plant growth and Cd accumulation, and AMF communities, but showed no synergistic interactions with Cd. In conclusion, MPs can mediate rice performance and Cd accumulation via altering soil properties, nutrient uptake, and root mycorrhizal communities, and biodegradable PLA MPs thought environment-friendly can exhibit higher phytotoxicity than conventional MPs.

Microplastics addition reduced the toxicity and uptake of cadmium to Brassica chinensis L.

The coexistence of microplastics (MPs) and toxic metal contaminants in soils is becoming increasingly common, thereby posing serious threat to soil-plant systems. Cadmium (Cd) is the most common metal contaminant in soil and can easily combine with MPs, thereby altering its bioavailability. However, few studies have focused on the co-pollution of MPs and Cd, particularly the complex phytotoxicity caused by their interaction and the effect of co-exposure on Cd uptake in plants. We conducted pot experiments to compare the effects of exposure to polystyrene (PS) and Cd, as well as the effects of co-exposure (PS + Cd), on the physiological characteristics of Brassica chinensis L. and explored the regulatory factors of MPs on Cd uptake in plant tissues. The results showed that plant biomass, photosynthetic parameters, and chlorophyll content significantly decreased (p < 0.05) with increasing PS doses under treatment with MPs alone. Although the negative effects of PS and Cd co-exposure on plants were higher than those of PS alone, however, the addition of MPs reduced the toxicity effects of Cd on plants and decreased the uptake and accumulation of Cd by plants compared with the Cd treatment alone. Furthermore, plants can resist the increased malondialdehyde content and oxidative stress induced by PS and Cd exposure by increasing the activities of superoxide dismutase and peroxidase. Under the PS + Cd treatment, linear models showed that soil organic carbon and sucrase activity were the key variables affecting Cd uptake by plant shoots and roots, respectively. The results of the partial least squares path modeling further showed that PS indirectly affected Cd uptake by B. chinensis by significantly affecting the physicochemical properties of soil, Cd concentration, and enzyme activity. Our results provide a new perspective and an important reference for further understanding the effects of MPs on the bioavailability and fate of heavy metals.

Uptake and transport of steroid estrogens in soil-plant systems and their dissipation in rhizosphere: Influence factors and mechanisms.

Residual steroid estrogens (SEs) in soil may be absorbed by plants, and subsequently threaten human health via food chains. However, the environmental behavior of SEs in soil-plant systems remains unclear. In this study, a wheat pot experiment using rhizosphere bags was performed to investigate the uptake and dissipation of target SEs (17 beta-estradiol (E2) and estrone (E1)) in different soils. The results indicated that soils with higher organic matter and silt and clay reduced the plant uptake of estrogens. Compared with E1, E2 was less accumulated in plants, which was mainly correlated with its higher hydrophobicity and shorter half-life. Estrogens tended to concentrate in the plant roots instead of translocating to the shoots. In addition, plant cultivation enhanced estrogen dissipation in the rhizosphere with an improvement of 10-21%. This improvement mainly resulted from stimulating the activities of estrogen-degrading enzymes, increasing the total bacterial populations, and promoting the development of estrogen degraders. Furthermore, this promotion effect will increase with plant growth. These findings will help us understand the characteristics of SEs taken up by plants and the role of the rhizosphere in SEs elimination, and provide theoretical insights into reducing the pollution risk of SEs in agricultural soils.

Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon.

The continental bio-cycling of silicon (Si) plays a key role in global Si cycle and as such partly controls global carbon (C) budget through nutrition of marine and terrestrial biota, accumulation of phytolith-occluded organic carbon (PhytOC) and weathering of silicate minerals. Despite the key role of elemental composition of phytoliths on their solubility in soils, the impact of plant cultivar and organ on the elemental composition of phytoliths in Si high-accumulator plants, such as rice (Oryza sativa) is not yet fully understood. Here we show that rice cultivar significantly impacts the elemental composition of phytoliths (Si, Al, Fe, and C) in different organs of the shoot system (grains, sheath, leaf and stem). The amount of occluded OC within phytoliths is affected by contents of Si, Al, and Fe in plants, while independent of the element composition of phytoliths. Our data document, for different cultivars, higher bio-available Si release from phytoliths of leaves and sheaths, which are characterized by higher enrichment with Al and Fe (i.e., lower Si/Al and Si/Fe ratios), compared to grains and stems. We indicate that phytolith solubility in soils may be controlled by rice cultivar and type of organs. Our results highlight that the role of the morphology, the hydration rate and the chemical composition in the solubility of phytoliths and the kinetic release of Si in soil solution needs to be studied further. This is central to a better understanding of the impact of soil amendment with different plant organs and cultivars on soil OC stock and on the delivery of dissolved Si as we show that sheath and leaf rice organs are both characterized by higher content of OC occluded in phytolith and higher phytolith solubility compared to grains and stems. Our study shows the importance of studying the impact of the agro-management on the evolution of sinks and sources of Si and C in soils used for Si-high accumulator plants.