A Preliminary Study On Screening And Remediation Potential Of Flower Plants For The Remediation Of Heavy Metal-contaminated Agricultural Soils Under Photovoltaic Panel In Northern Guangdong

Intercropping flower plants with hyperaccumulators can not only effectively remediate contaminated soils,but also beautify the environment,and increase land use efficiency and economic production.Photovoltaic is a kind of clean and renewable energy source.At present,photovoltaic agriculture has been put into practice at a large scale,while a few researches and practices on the combination of photovoltaic agriculture and soil remediation.In this study,the first case of farmland soil remediation-photovoltaic power generation project in China was taken as an example to explore the remediation potential of flower plants in polluted farmland under photovoltaic panel to obtain some flower plants with great remediation potential and high economic value.Subsequently,a pot experiment was conducted to study the effects of root interaction on plant growth and cadmium(Cd)and zinc(Zn)uptake of Excoecaria cochinchinensis and Sedum plumbizincicola under an intercropping system.Similarly,a field experiment was also carried out to investigate the effects of photovoltaic construction on plant growth,Cd and Zn uptake by plants,and economic benefits under an intercropping system of E.cochinchinensis with S.plumbizincicola,or Schefflera octophylla with S.plumbizincicola.The main results were as follows.(1)Significant differences for plant growth and Cd and Zn accumulation were observed among the 9 flower plants.The photovoltaic panel significantly affected the growth of the three herbaceous plants,which presented a smaller biomass and C d and Zn accumulation.The three herbaceous plants were thereby not suitable for the remediation of contaminated soil under the photovoltaic panels.E.cochinchinensis and Duranta repens showed higher bioaccumulation factors for Cd and Zn,thus greater potential for Cd and Zn accumulation.Photovoltaic shading didn’t affect plant growth of E.cochinchinensis and D.repens,with no changes for biomass and economic benefits.Thus,E.cochinchinensis and D.repens could be ideal flower plants for soil remediation under photovoltaic panels.(2)In the pot experiment,the biomass of S.plumbizincicola in the plastic board intercropping system was slightly higher than that in the monoculture system,and significantly higher than that in the nylon net intercropping system and the no separation intercropping system by 100% and 149%,respectively.With increasing root activities,Cd and Zn accumulation amounts per plant under nylon net separation system and unseparated intercropping system were significantly lower than that under plastic sheet separation system and monoculture system.Cd and Zn accumulation amounts per plant under plastic sheet separation system was significantly higher than that under monoculture system by 28.3% and 14.0%,respectively.E.cochinchinensis showed similar changes for plant growth and Cd/Zn uptake with S.plumbizincicola.The intercropping of E.cochinchinensis with S.plumbizincicola inhibited plant growth and Cd/Zn uptake due to root activities,which are possibly related to root exudates and worth further investigations.(3)The intercropping of S.plumbizincicola with E.cochinchinensis or S.octophylla under photovoltaic panels was carried out,as a practice for the combination of phytoremediation and intercropping system.Under the field condition,there was no change for plant growth and heavy metal uptake by S.plumbizincicola,E.cochinchinensis and S.octophylla,indicating that the intercropping of S.plumbizincicola with E.cochinchinensis or S.octophylla could be considered for practice.The biomass of S.octophylla was significantly different among different planting borders of photovoltaic panels,and the biomass of S.octophylla in border 2was significantly lower than that in border 1 and border 3.Photovoltaic shading didn’t affect the growth of S.plumbizincicola and E.cochinchinensis,while significantly affect plant growth and economic benefit of S.octophylla.Taking all of these into consideration,the intercropping of S.plumbizincicola with E.cochinchinensis could be a better choice for soil remediation practice with greater phytoextraction efficiency and economic benefit of flower plants.