长期施肥对汞在典型壤质潮土及作物中累积影响的研究

研究了长期(1989~2009年)不同施肥条件下,汞在典型壤质潮土中的累积趋势、形态变化,及其在冬小麦/夏玉米体系作物体内的富集与转移。田间试验设置7个不同施肥处理,有机肥(OM)、OM+化肥氮磷钾(NPK)、NPK、NP、PK、NK、和不施肥(CK),其中OM+NPK处理有机肥和化肥氮磷钾各占50%。每个处理4个重复。结果显示,经过20年的不同施肥处理,汞在表层土壤(0～20 cm)中的含量呈现先增加后减少的趋势。磷肥的长期施用是土壤中汞的重要来源,但对其在土壤中的累积趋势影响较小。弱酸溶解态和有机结合态汞的生物毒性较强,但在供试土壤中的含量较低,均约占其全量的6%;而铁锰结合态(18%)和残渣态(70%)是该土壤中汞的主要形态。汞在小麦茎叶和籽粒中的含量差异较小,显著的低于其在根系中的含量;汞在玉米根系和茎叶中的含量相似,明显高于其在籽粒中的含量。经过长期不同的施肥处理,汞在土壤中的含量表现为NPK≈OM+NPK≈NP≈PK>OM>NK≈CK,与其在作物根系及茎叶中含量的趋势总体一致;汞在两种作物籽粒中的含量表现为NPK≈CK>OM≈OM+NPK>NK>PK>NP,在作物产量较高及较低的情况下均容易导致汞在籽粒中的富集。在OM、OM+NPK、NK和CK几种施肥处理下,汞在土壤及作物根系中的含量与其余处理相比均较低,但作物通过加强对汞的转移能力,提高了其在作物茎叶及籽粒中的含量,尤其CK处理汞在两种作物籽粒中的含量。

Long-term Fertilization Impacts on Mercury Accumulation in Typical Fluvo-aquil Soil and Crops

The objective of this experiment was to study the effects of long-term different fertilization practices on the accumulation of mercury in soil,and its fraction changes through the method of three step extraction(BCR).This study also investigated the accumulation and transfer of mercury in crops.The field experiment was designed in 1989,including seven treatments:OM(Organic Manure),OM+NPK(50% Organic Manure + 50% Chemical Fertilizer),NPK,NP,PK,NK,CK(Control,no Fertilizer),and each treatment with four replicates.Although the application of phosphate fertilizer was a major source of soil mercury,long-term fertilization of phosphate didn't cause a significant accumulation of mercury in soil.The Acid-soluble-fraction and Oxidizable-fraction contents of mercury in soil were very low(6%,6%),as Reducible-fraction(18%) and Residual-fraction(70%) were the dominating fractions of mercury in soil.Most of mercury was accumulated in wheat root,and mercury contents in wheat root were significantly higher than its contents in wheat stalk or grain.Mercury contents in corn root and stalk were similar,which were higher than the contents of mercury in corn grain significantly.After long-term different fertilization,the trend of total mercury contents in soils for different treatments was:NPK≈OM+NPK≈NP≈PK>OM>NK≈CK,and the trend was similar in crop roots or stalks.The mercury contents in crops grain for different treatments followed the order as:NPK≈CK>OM≈OM+NPK>NK>PK>NP,which was mainly affected by crop yields.Although mercury contents in soil and crops were lower in treatments of OM,OM+NPK,NK and CK than other treatments,both crops increased its mercury contents in stalk and grain through strengthening the transfer ability of mercury in crops.