Department of Ecosystem Science and Management, The Pennsylvania State University, University Park, PA 16802, United States.
Adaptive Cropping Systems Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, MD 20705, United States.
Sci Total Environ. 2018 Mar;616-617:279-287. doi: 10.1016/j.scitotenv.2017.11.016. Epub 2017 Nov 6.
Cadmium contamination in soil is a substantial global problem, and of significant concern due to high food-chain transfer. Cadmium hyperaccumulators are of particular interest because of their ability to tolerate and take up significant amounts of heavy metal pollution from soils. One particular plant, Noccaea caerulescens (formerly, Thlaspi caerulescens), has been extensively studied in terms of its capacity to accumulate heavy metals (specifically Zn and Cd), though these studies have primarily utilized hydroponic and metal-spiked model soil systems. We studied Cd and nutrient uptake by two N. caerulescens ecotypes, Prayon (Zn-only hyperaccumulator) and Ganges (Zn- and Cd-hyperaccumulator) in four long-term field-contaminated soils. Our data suggest that individual soil properties such as total soil Cd, Zn:Cd molar ratio, or soil pH do not accurately predict Cd uptake by hyperaccumulating plants. Additionally, total Cd uptake by the hyperaccumulating Ganges ecotype was substantially less than its physiological capacity, which is likely due to Cd-containing solid phases (primarily iron oxides) and pH that play an important role in regulating and limiting Cd solubility. Increased P accumulation in the Ganges leaves, and greater plant Fe accumulation from Cd-containing soils suggests that rhizosphere alterations via proton, and potentially organic acid, secretion may also play a role in nutrient and Cd acquisition by the plant roots. The current study highlights the role that soil geochemical factors play in influencing Cd uptake by hyperaccumulating plants. While these plants may have high physiological potential to accumulate metals from contaminated soils, individual soil geochemical factors and the plant-soil interactions in that soil will dictate the actual amount of phytoextractable metal. This underlines the need for site-specific understanding of metal-containing solid phases and geochemical properties of soils before undertaking phytoextraction efforts.
土壤中的镉污染是一个全球性的重大问题，由于食物链的高转移率而引起了极大的关注。镉超富集植物因其能够耐受和吸收大量土壤重金属污染的能力而备受关注。一种特殊的植物，Noccaea caerulescens（以前称为 Thlaspi caerulescens），因其积累重金属（特别是 Zn 和 Cd）的能力而被广泛研究，尽管这些研究主要利用水培和金属添加的模型土壤系统。我们研究了两种 N. caerulescens 生态型（Prayon 型[仅 Zn 超富集型]和 Ganges 型[Zn 和 Cd 超富集型]）在四种长期污染土壤中对 Cd 和养分的吸收。我们的数据表明，个别土壤特性，如总土壤 Cd、Zn:Cd 摩尔比或土壤 pH 值并不能准确预测超积累植物对 Cd 的吸收。此外，超积累型 Ganges 生态型对 Cd 的总吸收量大大低于其生理吸收能力，这可能是由于含 Cd 的固相（主要是铁氧化物）和 pH 值在调节和限制 Cd 溶解度方面发挥了重要作用。Ganges 叶片中 P 的积累增加以及 Cd 污染土壤中植物 Fe 的积累增加表明，通过质子（可能还有有机酸）分泌改变根际环境也可能在植物根系对养分和 Cd 的获取中发挥作用。本研究强调了土壤地球化学因素在影响超积累植物对 Cd 吸收中的作用。虽然这些植物可能具有从污染土壤中积累金属的高生理潜力，但个别土壤地球化学因素和该土壤中的植物-土壤相互作用将决定实际可提取的金属量。这强调了在进行植物修复之前，需要对含金属的固相和土壤地球化学性质进行特定地点的了解。
