Understanding Cadmium Uptake by Cocoa Plants via Cd Isotope Analyses

镉(Cd)是一种微量金属，即使在低浓度下也是高度有毒的。可可中的Cd丰度相对较高，这对发展中国家的可可生产商来说是一个严重的问题，因为欧盟计划在2019年实施严格的可可产品中Cd的新上限。最近，这一事态发展促使人们研究可可中镉含量升高的原因。这方面的工作主要集中在土壤类型、酸碱度和栽培措施等外部因素对可可Cd含量的影响上，但到目前为止，这些调查未能提供确凿的结果。因此，有人提出，不同可可品种的镉积累可能有所不同，但这种可能的联系尚未得到调查。目前的项目包括伦敦帝国理工学院的同位素地球化学家M Rehkamper教授和雷丁大学的植物生理学家J Dunwell教授的合作研究。Rehkamper之前的工作表明，最初为行星科学研究而开发的Cd浓度和稳定同位素分析相结合，可以为植物对Cd的吸收和转移提供独特的见解。此外，2015年对Rehkamper和Dunwell进行的一项试点研究显示，这种分析对可可也很有希望。在目前为期6个月的项目中，将验证2015年试点实验的结果，以确保耦合的Cd浓度和同位素数据确实为植物对Cd的吸收和转移提供了可靠的衡量标准。此外，还将分析一系列不同的可可品种，以描述不同类型可可对Cd的吸收和积累的总体变异性。综上所述，这些结果将使人们能够初步确定特别适合种植的可可品种，因为它们的特点是，由于植物对镉的吸收较低，从根部到果实的运输减少，豆类中的镉积累最少。因此，这项研究的结果可以为开发可持续的方法生产具有安全镉水平的可可豆做出重要贡献，从而确保发展中国家的可可生产者有可靠的收入来源，并促进农村社区的经济。

Cadmium (Cd) is a trace metal that is highly toxic even at low concentrations. The relatively high Cd abundances often found in cocoa are a serious problem for the cocoa producers of developing nations, as the European Union plans to implement strict new upper limits for Cd in cocoa products in 2019. This development has recently spurred research into the causes of Cd enrichment in cocoa. Such work has mainly focused on the impact of external factors, such as soil type, pH and cultivation practices, on the Cd content of cocoa but until now, these investigations have failed to provide conclusive results. Hence, it has been suggested that Cd accumulation may vary across different cocoa varieties but this possible link has yet to be investigated. The current project constitutes collaborative research by Prof M Rehkamper, an isotope geochemist at Imperial College London, and Prof J Dunwell, a plant physiologist at the University of Reading. Previous work of Rehkamper has shown that coupled Cd concentration and stable isotope analyses, initially developed for planetary science research, can provide unique insights into Cd uptake and translocation by plants. Furthermore, a 2015 pilot study of Rehkamper and Dunwell revealed that such analyses are also promising for cocoa. In the current 6-month project, the results of the 2015 pilot experiment will be verified, to ensure that coupled Cd concentration and isotope data indeed provide a reliable measure for Cd uptake by and translocation within plants. Furthermore, a suite of different cocoa varieties will be analysed to characterise the overall variability of Cd uptake and accumulation amongst different types of this plant. Together, the results will enable an initial identification of cocoa varieties that are particularly suitable for cultivation because they feature minimal Cd accumulation in beans, due to low uptake of Cd by the plant and reduced transport from the roots to the fruit.As such, the results of this study can make an important contribution to the development of sustainable methods for the production of cocoa beans with safe levels of Cd, thereby ensuring a reliable source of income for cocoa producers in developing nations and boosting the economies of rural communities.