# Chemicals from Brominated Flame Retardants: Analytical Methods, Occurrence, Transport and Risks
## 4 Transport Mechanisms of BFRs
### Soil Sorption and Fate Processes
#### 4.3.2 Plant Uptake of BFRs in Soil  
Plants play a crucial role in terrestrial ecosystems, especially in soil environments. They have the ability to absorb and metabolize BFRs, which can then transfer from the soil to the aboveground parts of plants. This process can lead to the accumulation of BFRs in the food chain.  
The scientific community has extensively discussed the effects of BFRs on plant absorption and phytotoxicity [107]. Studies have specifically investigated BFR absorption by various plant species such as vegetables, tobacco leaves, and maize plant in both soil-based trials [99] and hydroponic solutions [36]. However, hydroponic research is known to have limitations, particularly in replicating the complex interactions present in soil ecosystems. These interactions can significantly influence the availability of contaminants, highlighting the need for caution when extrapolating findings from hydroponic studies to real-world soil environments.  
Recently, [PERSON] et al. [108] conducted a study using the RHIZOtest, a soil-based biotest optimized for organic substances, to investigate the absorption and translocation of four PBDEs and four NBFRs in tomato plants (_Solanum Lycopersicum_ L.). Their findings revealed higher concentrations of NBFRs in both the roots (ranging from 0.23 to 8.01 ng g dw for PBDEs and from 1.25 to 18.51 ng g\({}^{-1}\) dw for NBFRs) and the shoots (ranging from 0.09 to 5.58 ng g\({}^{-1}\) dw and from 0.47 to 7.78 ng g\({}^{-1}\) dw for PBDEs). The average values of the soil-root concentration factor (RCF) for PBDEs were lower than those for NBFRs at both initial spiking levels. However, no significant differences were found between PBDEs and NBFRs in the root-shoot transfer factor (TF) calculations. These findings suggest that the characteristics of PBDEs and NBFRs can explain the differences and similarities within and between the two groups of compounds reported in the RCF and TF. Their study also observed a decreasing trend in computed RCF and TF values as the number of bromine atoms in the PBDEs increased. Additionally, a strong negative linear association was found between the RCF values and the corresponding log K\({}_{\text{ow}}\) values for PBDEs, indicating that the hydrophobicity of PBDEs influences their root uptake. The hydrophobicity of NBFRs was found to negatively correlate with root absorption; however, this relationship was not observed during root-to-shoot transfer. The presence of a second aromatic ring in NBFRs, such as biphenyl NBFRs (BTBPE and DBDPE), was identified as a key factor affecting their uptake and translocation potential, as these compounds exhibited lower uptake and decreased translocation potential compared to monophenyl PBE and HBB.  
The studies generally suggest that inside the plant, BFRs can undergo various metabolic transformations. Plants have enzymes that can metabolize BFRs to less toxic or more easily excretable forms. The metabolism of BFRs in plants can lead to the formation of metabolites that may have different chemical properties and toxicity profiles compared to the parent compounds. Furthermore, several factors influence the uptake and metabolism of BFRs in plants, including the concentration and duration of BFR exposure, soil properties (e.g., organic matter content, pH), plant species, and environmental conditions (e.g., temperature, humidity).  
Understanding the transport mechanisms of BFRs and associated chemicals is crucial for assessing their environmental fate and potential risks. Further research is needed to improve our understanding of the fate and transport of BFRs in the terrestrial environment and to develop strategies to mitigate their impact on human health and the environment.