土壤砷有效性及其在柑桔中累积特征研究

Availability of Arsenic in Soil and Its Accumulation in Citrus Plants

在对全国柑桔主产区部分土壤和植株系统采样基础上,采用1.0mol/L HCl、0.5mol/L NaHCO3和1.0mol/L NH4Cl对土壤砷提取测定,结合土壤总砷、柑桔植株枝条、叶片和果肉中砷的测定结果,研究柑桔园土壤砷的总量、有效性及砷在柑桔中分布累积规律.结果表明:供试土壤总砷含量在1.77～16.0mg/kg之间,按土壤类型,黄棕壤最高,以下依次为黄壤、红壤和紫色土;砷在柑桔植株中累积分布规律为,叶片最高,枝条次之,果肉最少.其中,果肉与叶片砷含量呈极显著正相关(R=0.735 6**n=13),且叶片累积远大于果肉;三种提取剂中,0.5mol/L NaHCO3无论在酸性或石灰性土壤上提取结果均表现与柑桔果肉砷含量具极显著正相关性(R=0.541 0**n=45),可作为柑桔土壤砷有效性指标;0.5mol/L NaHCO3提取有效砷与土壤Olsen磷呈极显著正相关(R=0.600 6**n=45),且在不同酸碱性质土壤上砷的提取量与Olsen磷的大小具有相同趋势,证明砷在土壤中具有与磷相似的化学行为和吸附-解吸特征.

Concentrations of total and available As in soils of citrus orchards,and As distribution in citrus plants were studied based on soil and plant samples collected from the main citrus producing areas all over China.Three solutions,1.0 mol/L HCl,0.5 mol/L NaHCO3 and 1.0 mol/L NH4Cl,were used to extract arsenic from the soil samples,and the results were compared with the concentrations of arsenic in branches,leaves and pulps of the citrus plants.The soil samples of the yellow brown soil had the highest total arsenic concentrations,ranging from 16.0 to 1.77 mg/kg,followed in order by yellow soil,red soil and purple soil.The distribution of arsenic in the plant appeared in the order of leaves branches pulps.Arsenic concentration of the pulps was significantly correlated with that of the leaves（R=0.735 6＊＊ n=13）,while the latter was far higher than the former.Arsenic concentrations extracted by 0.5 mol/L NaHCO3 from both acid and calcareous soils were significantly correlated with As concentrations extracted from citrus fruits（R=0.541 0＊＊ n=45）,suggesting that this method could be used as standard to decide the availability of As in soil to citrus fruits.Furthermore,arsenic concentrations extracted by 0.5 mol/L NaHCO3 were significantly correlated with Olsen P from the same soil samples（R=0.600 6＊＊ n=45）,which implied that soil As and P shared similar absorbing/desorbing behavior.