###### Abstract
There are complex interactions between heavy metals and organic pollutants in the environment, including in the adsorption behaviour, chemical processes (complexation and dissociation, redox, acid base reaction, precipitation and dissolution, etc. ), and microbial processes [21]. These interactions make heavy metals and organic compounds form more complicated combined pollution. Combined pollution not only has the toxicity of heavy metals or organic compounds but also can produce additive, synergistic, or antagonistic effects, thus changing the nature of the pollutants, biological toxicity, and environmental behaviour. Electronic waste and its dismantling sites contain large amounts of heavy metals and PBDEs and plants are vulnerable to compound pollution during growth and development. It was found that under the combined pollution of copper and BDE-209, the presence of copper could induce damage in the cell membranes in maize roots, resulting in an increase in the BDE-209 content in the aboveground parts of the plants [22]. Similarly, the growth of pumpkin and the absorption and metabolism of BDE-209 were also affected by copper stress to varying degrees. Higher concentrations of copper inhibited the absorption and metabolism of BDE-209, while the hydroxylation of polybrominated diphenyl ethers was enhanced at the 50 mg/kg copper level [23]. In addition, heavy metal pollution usually reduces the soil's enzyme activity and weakens soil respiration, thereby indirectly extending the half-life of organic pollutant degradation to a certain extent [24]. The combined effects of combined pollution also affect plant growth, rhizosphere biological populations, and microecological processes, including the soil's physical and chemical properties and biological changes, thereby further affecting plants' physiological and biochemical properties and the uptake and transformation of pollutants [25]. However, the toxicity of co-pollutants in _Amaranthus mangostanus_ L. has still scarcely been reported. Hence, the environmental risk of co-pollutants is clearly elucidated to provide a basis for establishing a reasonable control technology to prevent the migration of co-pollutants into _Amaranthus mangostanus_ L.  
In this study, we exposed amaranth to Cd, BDE-153, and both Cd and BDE-153 under simulated hydroponic conditions to better analyse the effects of Cd and BDE-153 on the growth and related physiological and biochemical indexes of the amaranth under single and interactive stress. The photosynthetic parameters, antioxidant mechanisms, cell integrity, and time accumulation characteristics of the Cd and BDE-153 in the plants under Cd/BDE-153 combined pollution stress were studied, which provided data support for the study of the phytoremediation of heavy metal-polybrominated diphenyl ether combined pollution. As far as we know, this is the first time the physiological response of amaranth under the combined pollution of Cd and BDE-153 has been studied, and it is the first time that different concentrations of a heavy metal environment have been to found to have different effects on the absorption and transport of polybrominated diphenyl ethers in the same plant.