洪泽湖湿地重金属含量与N_2O释放特征及关系

Relationship between heavy metal contents and N_2O emission in sediments from Hung-tse Lake wetland

以洪泽湖河湖交汇区5种典型土地利用/覆被类型(芦苇地、杨树林、柳树林、水稻田、养殖塘)为对象,研究沉积物重金属含量与N_2O释放特征及关系.结果表明:水稻田的Cd、Cr、Cu、Pb、Zn含量分别为(0.3±0.0)mg·kg^(-1)、(72.4±6.1)mg·kg^(-1)、(37.7±1.4)mg·kg^(-1)、(24.8±0.5)mg·kg^(-1)、(115.3±6.2)mg·kg^(-1),显著高于其他4种土地利用/覆被(P<0.05);水稻田土壤的N_2O潜在释放速率最高,达到(5.83±1.82)mg·kg^(-1)·h^(-1),芦苇地,杨树林,柳树林,养殖塘的释放速率较低且4者间无显著性差异,除了养殖塘为N_2O汇.芦苇覆被方式下,土壤中N_2O潜在释放速率与Cd、Cu含量极显著正相关(P<0.01),与As、Mn、Zn含量显著正相关(P<0.05).结合土壤Cd、Cu、As、Mn、Zn的含量特征,可以认为,低剂量Cd、Cu、Mn、Zn和较高浓度的As可能刺激芦苇地土壤N_2O的释放.人为对湿地土地利用的改变使土壤重金属含量与N_2O释放之间关系的不确定性增加.

To investigate the potential relationship between heavy metal contents and N_2O emissions,soils were sampled from 5 typical land use/cover types,namely reed cover,poplar forest,willow forest,paddy field and aquafarm in the meeting place of Hungtse Lake and Huai River. The results showed that contents of Cd,Cr,Cu,Pb and Zn in paddy field were( 0.3±0.0),( 72.4±6.1),(37.7±1.4),(24.8±0.5) and(115.3±6.2) mg·kg^(-1),respectively,which were significantly higher than those from other 4 land use/cover types. Meanwhile,average N_2O emission rate in paddy field [( 5. 83 ± 1. 82) mg · kg^(-1)·h^(-1)] was notably higher than those of other 4 land use/cover types. In contrast,no significant difference among reed cover,poplar forest,willow forest and aquafarm was found for N_2O emissions. In addition,N_2O emission rates in soils were significantly positively correlated with the contents of Cd and Cu( P<0.01),and the contents of As,Mn and Zn( P<0.05) under reed cover. Combined with profiles of Cd,Cu,Mn,Zn and As,it can be concluded that N_2O emissions under reed cover were substantially stimulated by low contents of Cd,Cu,Mn,Zn,and high As contents. The results suggest that land use change would notably increase the uncertainty of relationship between heavy metal contents and N_2O emissions.