Phytoremediation of copper-contaminated soils by drip or sprinkling irrigation coupled with intercropping

Intercropping improves the phytoremediation of soil trace metal contamination. Dripping irrigation could further promote the phytoremediation of trace metals by influencing their speciation and total amount in soil. However, there is currently insufficient information elucidating this synergistic effect. In this study, the combined effect of drip irrigation and intercropping on the phytoremediation of Cu-contaminated soil was testified by investigating the changes of Cu spatial distribution and speciation in soil irrigated by dripping or sprinkling methods, as well as Cu bioconcentration factor and translocation factor by plants. Results showed that after a 30-day drip irrigation, the Cu level in soils near the drip outlet decreased by 4.7% and that in Triticum aestivum L. (T. aestivum) roots intercropped with Helianthus annuus L. (H. annuus) and Zea mays L. (Z. mays) dropped by 53.2% and 25.1%, respectively, relative to sprinkler irrigation. Meanwhile, the total Cu and exchangeable Cu levels in soils 6 cm away from the drip outlet increased by 10.8% and 20.4% after 30 days of drip irrigation, leading to 41.1% and 40.0% increases of Cu content in remediation plants H. annuus and Z. mays seedlings as compared to the values by sprinkler irrigation. Therefore, the drip irrigation enhanced the effect of intercropping on Cu phytoremediation.