长期施用畜禽养殖废弃物下潮土重金属的累积特征

摘要

An experiment was conducted since 2001 to study the accumulation, fraction change and transfer of heavy metals in soils under long-term livestock manure application. The treatments of field experiment included OM (pig manure) and balance-fertilization of chemical fertilizers (NPK). The results showed that over 13 years (2001—2013) of livestock manure application, Cu and Zn in soils, especially in tillage layer (0–20 cm) significantly accumulated, But in 2013 heavy metal concentrations (Cu: 38.71 mg/kg; Zn: 83.26 mg/kg) were very low, loading little negative effects on eco-agricultural safety. Results of sequential extraction showed that Cu, Zn, As concentrations in DTPA-, acid soluble (EXCH-), reducible (FeMnOX-) and oxidizable (OX-) factions under OM treatment were significantly higher than those in NPK treatment. However, Cr, Pb and Cd stabilized in soils, was less affected by different fertilizations. The dominant fraction of Cr in soil was residual fraction (RESD-) (>95%). Most of Cu added by livestock manure was accumulated in RESD- fraction (>50%), while added Zn was easily accumulated in EXCH- (40%) fraction and in FeMnOX- (60%) fraction. Long-term application of livestock manure is not only the major source of soil heavy metals, but also significantly affect their fractions through changing soil properties, which are also important reasons for more metals transferred to deeper soils.%通过田间试验研究了畜禽养殖废弃物长期施用(2001—2013年)对重金属(Cr、Cu、Zn、Pb、Cd、As)在潮土中累积、形态转化及迁移行为的影响.试验设置畜禽养殖废弃物(猪粪,OM)和化肥氮磷钾(NPK)两个处理,每处理设置3个重复.结果显示,畜禽养殖废弃物的长期施用造成Cu、Zn在OM处理土壤中的含量明显高于NPK处理,并主要累积于耕层土壤(0~20 cm),但总体含量(Cu:38.71 mg/kg;Zn:83.26 mg/kg)较低,对农田生态安全的影响较小.形态分析结果显示,OM处理土壤中DTPA络合态、弱酸结合态和铁锰结合态Cu、Zn、As的含量均显著高于NPK处理,但不同形态Cr、Pb、Cd在两种处理土壤中的差异相对较小.其中,Cr主要以非提取态的形式存在(Cr>95%).外源性Cu易累积于非提取态(52%),而Zn则以弱酸溶解态(40%)和铁锰结合态(60%)为主.畜禽养殖废弃物的农田施用不仅是土壤重金属的重要来源,也是土壤重金属活性提高的重要原因,并造成部分重金属在剖面土壤中发生明显迁移行为,累积于更深层土壤中.