Cadmium is a toxic non-essential metal for almost all living systems. It is one of the biggest challenges for farmlands and the food chain because of its toxic effect on human health. This research aims to determine the Cd content in soils, litter and cacao beans, following the Cd fluxes within each cacao system using the two-dimensional electrical resistivity tomography technique. The study was carried out in four farms located in the Magdalena basin in Antioquia, Colombia. The farms showed a heterogeneity in relation to cacao cultivars, altitude, topography and geology. The soil cation electrical capacity, pH and soil organic matter levels, as well as the Al, Al³⁺H⁺, Ca, K, Mg and P contents were measured at different depths. Moreover, the Cd content was correlated to the resistivity values of samples taken in situ using ERT. Soil Al³⁺H⁺ and the altitude of the farms fitted as the best predictors of the beans’ Cd content. Furthermore, the Cd content in soils from the assessed farms ranged between 1.22 and 2.03 mg kg⁻¹. The Cd content in cocoa beans ranged from 0.07 to 1.44 mg kg⁻¹, with a value of 0.40 mg kg⁻¹ on average. The resistivity values obtained in field showed a high correlation with the soil Cd content determined (R² = 0.82). The predictive tomography plots highlighted topsoil Cd dynamics between litter, amendments and fertilizers. Therefore, these results underlie the utility of the combined geophysical techniques and soil chemical properties including the analysis of fertilizer amendments to improve the understanding of Cd dynamic.

Graphic abstract

中文翻译：

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土壤，土壤垫料和可可豆中的镉分布：哥伦比亚的一个案例研究

镉几乎对所有生物系统都是有毒的非必需金属。由于其对人体健康的毒性作用，这是农田和食物链的最大挑战之一。这项研究旨在利用二维电阻层析成像技术，根据每个可可系统中的Cd通量，确定土壤，垃圾和可可豆中的Cd含量。这项研究是在哥伦比亚安蒂奥基亚的马格达莱纳盆地的四个农场进行的。这些农场在可可品种，海拔，地形和地质方面表现出异质性。土壤阳离子电容，pH和土壤有机质含量以及Al，Al ³⁺ H ⁺，钙，钾，镁和磷的含量是在不同深度下测量的。此外，Cd含量与使用ERT现场采集的样品的电阻率值相关。土壤Al ³⁺ H ⁺和农场的海拔高度可以作为豆中Cd含量的最佳预测指标。此外，来自评估农场的土壤中的Cd含量在1.22至2.03 mg kg ^-1之间。可可豆中的Cd含量在0.07至1.44 mg kg ^{-1的范围内}，平均值为0.40 mg kg ^-1。在田间获得的电阻率值与确定的土壤镉含量具有高度相关性（R ² = 0.82）。预测层析成像图突出了凋落物，改良剂和肥料之间的表土镉动态。因此，这些结果为结合地球物理技术和土壤化学性质的实用性奠定了基础，其中包括分析肥料改良剂以增进对Cd动力学的理解。

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