Grass Vetiveria zizanioides (L.) Nash for Immobilization of Copper in the Orange-growing Soil Contaminated by the Overuse of Fungicides: A Casestudy at Cao Phong, Hoa Binh

The overuse of copper (Cu) fungicides has resulted in an accumulation of Cu in the orange-growing soil in Cao Phong district, Hoa Binh province. In this study, we analyzed the fractionation and accumulation of Cu in soils treated with two types of fungicides: Norshield 86.2WG  and Epolists 85WP. Using vetiver grass has been known as a approach to immobilize heavy metals in soil, herein, its effect on the fate of Cu was also considered. The bioavailability of Cu was relatively high for both the tested soils treated with Norshield 86.2WG  (~9.82-11.03%) and Epolists 85WP (~8.46-10.79%). Noting that Cu in different fractions increased following the order F1 (water soluble) < F2 (exchange adsorption) < F3 (special adsorption) < F4 (bound with Fe/Al hydroxide) < F5 (bound to organic matter) < F6 (remaining form). The use of vetiver grass resulted in different accumulation levels of Cu  between natural soil (9.5 ± 0.53 ppm) and Cu-added soils (from 16.17 ± 1.72 to 27.13 ± 1.31 ppm). The application of Norshield 86.2WG  and Epolists 85WP has exacerbated the contamination of soil by Cu, therefore, to manage and enhance soil health in this area, we need to consider reducing the use of fungicides in the orange-growing areas. Keywords: Cao Phong orange, fungicides, Cu pollution, Cu accumulation, Vetiver grass.