Publication
Soil pollution is a major environmental problem actually in China and in the world. It increases environmental risks and can affect humans through the food chain. Like solutions to clean-up the soils are generally expensive and can have side effects on environment, phytoremediation, an environmental friendly technology is a good alternative to traditional remediation. Nevertheless, some improvements must be done to increase its efficiency and make it economically viable. The goal of this work is to study two strategies respectful of the environment to improve the efficiency of phytoremediation: the co-cropping and the addition of amendments. Two Chinese species, Sedum alfredii (hyperaccumulator of cadmium) and Ricinus communis (accumulator of DDT) were co-cropped in pots with a soil contaminated by cadmium and DDT, in which different amendments (rapeseed waste, pig manure, a bio-surfactant: tea saponin, one of its by-product, and sulfur) were added to observe if they increase the efficiency of the phytoremediation. Bacteria were also used to improve DDT degradation. If the ricinus grew fast and easily, sedum biomass was very low and seems not suitable for co-cropping in these conditions. The rapeseed waste inhibit the growth of plants, suggesting that the dose was probably to high. Other amendments allowed a relatively similar growth with sensitively the best for tea saponin and microbes do not affect significantly the biomass. After determined in laboratory that tea saponin enhance the desorption of DDT and Cd in soil, an other pot experiment was started with Ricinus communis in soil amended with different concentrations of saponin to see if it also improve the phytoremediation. In the future, if the addition of amendments can enhance the phytoremediation as expected, analysis of parameters such as the quantity of nutrients or pollutants bioavailable or the structure of dissolve organic matter (DOM) might be done to see if they can explain this phenomenon. Further analysis in field conditions and with optimal concentrations of amendments are needed to determine if and in which conditions these strategies can be applicable at large scale.