Abstract:

The objective of this study was to identify effective remediation materials for arsenic (As) immobilization in arsenic-contaminated alkaline soil and reducing As accumulation in hulless barley grains, thereby providing technical support for the safe production of hulless barley in arsenic-contaminated alkaline farmlands in Xizang region. The study employed biochar and various iron salts as raw materials to prepare iron-biochar materials via an impregnation method. A pot experiment was conducted to investigate the effects of different remediation materials (CK: control, BC: biochar, FeBC1: FeCl₃/biochar composite, FeBC2: FeSO₄/biochar composite, FeBC3: Fe₂(SO₄)₃/biochar composite) on soil available As content, As concentrations in various tissues of hulless barley, bioconcentration factor (BCF), transfer factor (TF), crop yield, and its components. The results showed that: (1) application of iron-biochar composites comprehensively regulated plant height, tiller number, effective panicles per plant, 1000-grain weight, and grains per panicle, thereby increasing hulless barley yield. The FeBC2_(2/40) and FeBC3_(1/40) treatments achieved the highest grain yields among all treatments, at 32.03±1.52 and 30.47±1.54 g, respectively. (2) Compared with CK, all treatments significantly reduced As concentrations in the stems, leaves, husk, and grains of hulless barley. The FeBC1 and FeBC3_(3/40) treatments reduced BCF_root, while all treatments reduced BCF_stem, BCF_leave, BCF_husk, and BCF_grain, as well as TF_stem/root. (3) Application of iron salt-biochar composites significantly decreased the contents of non-specifically adsorbed and specifically adsorbed As fractions, and increased the contents of amorphous Fe/Al oxides, crystallized Fe/Al oxides, and residue As fractions. The FeBC1_(2/40) treatment increased the total proportion of Fe/Al oxides and residue As from 57% to 71%, and decreased the total proportion of non-specifically and specifically adsorbed As from 43% to 29%. The As enrichment capacity in different tissues of hulless barley followed the order: roots > stems > leaves > husk > grains. After uptake, most As remained in the roots, with only a small amount transport to aboveground. Application of materials reduced soil available As content in alkaline arsenic-contaminated soil and regulated As enrichment in different tissues and translocation coefficients, with the FeBC1 treatment showing the most significant effects. Under the conditions of this experiment, total As concentrations in hulless barley grains treated with FeBC1_(2/40) and FeBC1_(3/40) were ≤0.5 mg/kg, indicating that safe production of hulless barley in arsenic-contaminated alkaline farmland can be achieved.

Key words: hulless barley, arsenic-contaminated soil, available arsenic, iron salts, biochar