Study on remediation technology of cadmium pollution in aeolian sand soil in Northwest China: Fly ash combined with ryegrass bioreintervention

Abstract With the development of urbanization and industrialization, a large number of heavy metal pollutants continue to enter the environment, which has caused severe harm to human health and ecological environment. The heavy metal pollution in soil has been aggravated, and the soil quality has deteriorated seriously. Therefore, cost‐saving and efficient soil remediation technology is imminent. Aiming at resolving a series of soil problems existing in Cadmium‐polluted aeolian sandy soil in Ningdong Energy Base of Ningxia, northwest China, it is very important to explore green and effective bioremediation technology for local ecosystem restoration and healthy and sustainable development. A pot experiment was designed with three different fly ash compound modifiers being added to the Cadmium‐polluted aeolian sandy soil. The perennial ryegrass was used as the test material, and 13 different formula treatments were set. By measuring and analysing soil physical and chemical properties, total Cadmium content, four forms of Cadmium and Cadmium enrichment in various parts of plants, the biological combined remediation effect of fly ash and different material compound modifiers combined with ryegrass were comprehensively evaluated by principal component analysis. Treatment with multiple application of amendments can improve soil water holding capacity and saturated water content, among which the field water holding capacity of FS4 treatment increased the most, increasing by 26.40% compared with without improver (CK), and the saturated water content of the modifier was added with 80% fly ash and 20% organic fertilizer, and the mass ratio of the modifier to soil was 2% (FY2) treatment increased the most, increasing by 20.85% compared with CK. The application of fly ash alone and the application of fly ash apatite compound amendment had no significant effect on soil alkaline nitrogen lysis, while the other two compound modifiers can increase the soil alkali‐hydrolysable nitrogen, and the modifier was added with 80% fly ash and 20% organic fertilizer, and the mass ratio of the modifier to soil was 4% (FY4) treatment increased the most, with an increase of 269.23%. Except for the add 100% fly ash modifier, and the mass ratio of the modifier to soil was 1% (F1) treatment, the dry weight of ryegrass was significantly increased by applying amendments, Although the Cd content of plants decreased, the Cd enrichment of plants increased after the application of the amendments. Applying amendments combined with ryegrass can reduce the total amount of Cd and the proportion of available Cd in soil, and the proportion of available Cd continues to decrease with time. After applying the improver, the biomass and the total amount of heavy metals in ryegrass increased significantly, while the total content of heavy metal Cd and the proportion of available Cd in soil decreased. The ecological remediation effects of FY4, FY2 and FS4 were better, among which FY4 is recommended as the remediation of Cd‐contaminated aeolian sand in Ningdong Energy and Chemical Industry Base.