Changes in Metal Distribution, Vegetative Growth, Reactive Oxygen and Nutrient Absorption of Tagetes patula under Soil Cadmium Stress

Phytoremediation with hyperaccumulator plants has been recognized as a potential way for the clearing of cadmium (Cd)-contaminated soil. In this study, hyperaccumulator Tagetes patula was treated with seven concentrations of Cd, ranging from 0 to 300 mg kg−1. The Cd enrichment and nutrient contents in different organs during different growth phases were investigated. Under Cd concentrations ≤75 mg kg-1, the morphological growth of T. patula did not change significantly regardless of growth stage. However, when Cd concentration exceeded 150 mg kg−1, the morphological growth was remarkedly inhibited. The root/shoot ratio remained unchanged except for at 300 mg kg−1. In addition, Cd negatively influenced the flowering process at the concentration of 300 mg kg−1. Cd content increased significantly in Cd-treated plants. Nitrogen absorption was increased under Cd treatments, and phosphorus content was also increased under concentration ≤150 mg·kg−1. However, the potassium content in the flower was decreased under 300 mg kg−1. Furthermore, the contents of H2O2, O2− and malondialdehyde were increased during the seedling phase, especially when Cd concentration was ≥150 mg kg−1. In summary, T. patula showed a strong ability to tolerate Cd, and such ability might be explained by nutrient absorption and reactive oxygen clearness.

Lowering the Toxicity of Cd to Theobroma cacao Using Soil Amendments Based on Commercial Charcoal and Lime

Carbonaceous and calcareous materials are commonly used as amendments to decrease the Cd mobility in contaminated soils. This study evaluated the effect of amendments applied to cocoa seedlings in the greenhouse, considering the mobilization of soil cadmium toward the seedlings as the main response. The experimental conditions considered soil artificially contaminated with Cd at a concentration of 50 mg Cd kg−1 and applications of amendments in different treatments with the presence of charcoal dust and calcium carbonate. The charcoal was characterized by microscopy and by adsorption tests, and it proved to be a material with macropores, with a maximum capacity of 8.06 mg Cd g−1 and favorable kinetic behavior according to the adjustment of the data obtained to the pseudo-second-order model. The results also showed that the application of liming decreased the mobility of Cd toward the seedlings, with the liming combined with charcoal leading to the absence of Cd in the cocoa seedlings, considering a residual concentration of Cd in the soil of 35 mg Cd kg−1. The results, although limited to a small scale, demonstrated the possibility of applying low-cost and easy-to-handle amendments for the control of Cd in cocoa plantations.

Impact of Industrial Pollution of Cadmium on Traditional Crop Planting Areas and Land Management: A Case Study in Northwest China

Cadmium in soils not only reduces crop yield and quality but also threatens the safety of human health and wildlife due to bioaccumulation. Baiyin City, a typical industrial region located in northwest China, was evaluated to examine the spatial distribution of cadmium. We simulated soil cadmium concentrations in the laboratory, based on levels found at local sampling sites, to examine how both Medicago sativa and Zea mays plants accumulate cadmium. The experimental results revealed that cadmium in all soil samples exceeded China’s national standard levels for general farmland; in addition, cadmium accumulation in all tissues of M. sativa and Z. mays exceeded the national fodder standards. Therefore, M. sativa and Z. mays from the study area should not be used for fodder. However, about 36% of the planting area of M. sativa and Z. mays can be used for phytoextraction because of cadmium accumulation. For soil pollution management, we suggest dividing the study area into three different regions, including a non-planting region, a phytoremediation region, and a planting region. Our soil management model can effectively help local people to avoid food safety risks and to realize sustainable development of soil utilization in contaminated areas.

Nanoparticles Induced Restricted Cadmium Mobility and Accumulation in Wheat From Contaminated Soil

Nanotechnology has gained importance over conventional technologies to enhance crop yield and environmental sustainability. In agricultural soil, cadmium (Cd) contamination has been a serious issue, impacting food security and quality and caused serious human health and environmental problems. Nanoparticles (NPs) have large surface area and high adsorption capacity, due to which they are efficiently used to remediate Cd-contaminated agricultural soils. The aims to conduct this experiment were to evaluate the effects of iron (Fe), silicon (Si) and zinc (Zn) NPs on the growth, physiology, and accumulation of Cd in various parts of plants. Soil in bulk was collected and spiked with different Cd levels (0, 5, 10, 20 mg kg-1), and NPs @ 60 mg kg-1 of soil were applied at the time of wheat sowing. Plants showed significant increase in shoot length and grain yield with the NPs application compared to control (no NPs application). The results illustrated that NPs have a positive effect on stomatal conductance, transpiration rate, photosynthetic rate compared to control. The Cd concentration in roots, shoot and grains were reduced by 36%, 50% and 69% with the application of NPs. However, this reduction was more pronounced at 5 mg kg-1 Cd with Fe-NPs followed by Zn-NPS and Si-NPs. Overall, it was concluded that NPs play an important role in the enhancement of plant biomass, increase in nutrients availability, and decreasing the Cd accumulation in different plant parts.