Xia Jia,Chunyan Zhang,Yonghua Zhao,Tuo Liu,Yunhua He
Few studies have explored the long-term effects of elevated atmospheric CO 2 combined with lead (Pb) contamination on plants. The objective of this study was to examine the effects of 3 years of elevated CO 2 (700 ± 23 μmol mol –1 ) on Pb accumulation and plant defenses in leaves of Robinia pseudoacacia L. seedlings in exposed to Pb (500 mg kg −1 soil). Elevated CO 2 increased Pb accumulation in leaves and Pb removal rate in soils. In plants exposed to Pb stress, total chlorophyll and carotenoid contents in leaves were lower under elevated CO 2 than under ambient CO 2 , but seedling height and width increased under elevated CO 2 relative to ambient CO 2 . Elevated CO 2 significantly ( p < .01) stimulated malondialdehyde content in leaves under Pb exposure. Superoxide dismutase and catalase activity increased significantly ( p < .01), peroxidase activity decreased significantly ( p < .01), and glutathione , cystine, and phytochelatin contents increased under elevated CO 2 + Pb relative to Pb alone. Elevated CO 2 stimulated the production of soluble sugars, proline, flavonoids , saponins, and phenolics in plants exposed to Pb stress. Ove rall, long-term elevation of CO 2 increased Pb-induced oxidative damage in seedlings, but enhanced the phytoextraction of Pb from contaminated soils.
Jingjing Fang,Shiyu Chen,Yaling Leng,Wen Shi,Gaoxiang Zhang,Yijie Lin,Feili Li
In aquatic ecosystems, dissolved organic matter (DOM) enhances the adsorption of heavy metals onto microalgae by participating in the formation of algae–heavy metal–DOM ternary complexes, thereby increasing environmental risks. The functional groups in the DOM play a crucial role. However, a quantitative description based on these groups is lacking. This study investigates the effects of amino acids (AAs) with varying functional group ratios on the accumulation of lead (Pb) in Chlorella pyrenoidosa ( C. pyrenoidosa ) using batch experiments. Isotherm model fitting, and Fourier transform infrared spectroscopy (FTIR) are employed for characterisation. Results indicate that the addition of AAs facilitated Pb enrichment in microalgae. In particular, incorporating lysine (Lys) led to maximum accumulation, reaching 1.45 mmol g −1 . The adsorption rate decreased after AA addition, particularly with Lys, dropping form 0.0032 g mg −1 min −1 to 0.0009 g mg −1 min −1 . The reaction sequence showed carboxyl groups taking precedence over amino groups. The model developed from the data on Pb adsorption by C. pyrenoidosa following AA addition, demonstrated reliability with an R 2 of 0.91 and an F -value of 157.6. Notably this study employed two-dimensional correlation spectroscopy (2D–COS), offering novel insights into the key roles of functional groups and their distinct contributions. These valuable insights contribute to intensive research on the ternary complex of algae − heavy metal − DOM and elucidating their ecological risks.
With the increasing production and applications of TiO 2 nanoparticles (NPs), their presence in aquatic environments, especially in sediments, will inevitably increase over time. Most studies investigating the influence of TiO 2 NPs on the bioaccumulation of co-existing contaminants have focused on the aqueous phase; however, few have examined the sediment phase, which contains more TiO 2 NPs and contaminants. We investigated the effects of TiO 2 NPs on Pb accumulation by Corbicula fluminea in sediments, and explored extracellular and intracellular Pb concentrations in the various soft tissues of the bivalve. Pb was spiked with 50 mg/kg in sediment and TiO 2 NPs/sediments ratios were within the range 0.2–3.0%. The results showed that TiO 2 NPs presented larger adsorption capacity and affinity to Pb ions than the sediments. In addition, the large adsorption capacity of TiO 2 NPs and the strong adsorption affinity to Pb ions caused part of the Pb ions released from sediments to aqueous phase were re-adsorbed by TiO 2 NPs in sediments. The concentration of TiO 2 NPs in C. fluminea tissues significantly increased with increasing TiO 2 NP content in sediments, following the order: gill > mantle > foot > visceral mass, which differed from the results found in the aqueous phase. In addition, the proportions of extracellular and intracellular Pb concentrations changed significantly in all the tissues as a result of TiO 2 NP contamination of sediments. TiO 2 NPs promote increased extracellular Pb in foot, mantle, and gill tissues, and increased intracellular Pb in the visceral mass. These results may be beneficial to more scientifically evaluate and predict the environmental risks of TiO 2 NPs to benthic organisms in sediments contaminated by heavy metals.
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