Effects of compound passivation material on soil arsenic availability and cabbage growth in farmland

【Objective】To explore the effects of applying different compound passivation materials on soil As speciation and cabbage growth in karst mountainous areas in Guizhou, and to screen passivation material which were able to reduce heavy metal content in crops, so as to provide a theoretical basis for the remediation of arsenic-polluted soil.【Method】Pot experiment was carried out. Taking the soil with no passivation as control(CK), and different compound passivation iron ore powder+steel slag(AB), iron ore powder+cinder(AC), iron ore powder+steel slag+cinder(ABC), iron ore powder+steel slag+humus(ABD), iron ore powder+steel slag+cinder+humus(ABCD) were applied in contaminated soil, and As content in soil and cabbage was determined by atomic fluorescence spectrometer to analyze passivation effects of different compound passivation materials.【Result】Compared with CK, adding four kinds of compound passivation materials, AB, AC, ABC and ABCD could significantly reduce the effective content of As in the soil (P<0.05, the same below), while the passivation effect of ABD was not significant(P>0.05), and treatment ABC had the highest passivation rate of 60.91%. The proportions of O-As and Al-As in the tested soil showed a gradually increasing trend, and the proportions ranged from 32.52% to 34.88%, 16.44% to 28.17%; and the proportions of AE-As, Fe-As and Ca-As showed a downward trend, and the proportions ranged from 0.66% to 1.50%, 19.63% to 31.28%, and 16.64% to 17.15%. After the applying compound passivation agents, the biomass of cabbage was significantly increased, and the highest increase of 91.46% was witnessed in treatment ABC, and the plant height and plant width also increased correspondingly, reaching a significant level(except for plant width in treatment AC). The variation range of arsenic content in the above-ground and underground parts was 0.306-0.588 mg/kg, 0.622-1.592 mg/kg, which indicated the materials effectively inhibitedarsenic accumulation in the above-ground and under-ground parts of cabbage. The arsenic content of the above-ground parts(edible parts) treated by AB, AC, ABC and ABD were all lower than the national standard(GB 2762-2017) (fresh vegetables As ≤ 0.5 mg/kg); treatments AB, AC, and ABC inhibited the ability of cabbage to transport arsenic to the above-ground to different degrees.【Conclusion】Applying 2.5% iron ore powder+1.0% steel slag+2.0% cinder can not only effectively reduce the effective content of arsenic in the soil, but also minimize arsenic accumulation of in the above-ground of the cabbage (edible part) to promote the growth and development of cabbage.