用铅污染农田土壤做盆栽试验,研究了氮肥品种和施用量对小白菜吸收铅及土壤中铅形态的影响。结果表明,在氮肥施用量相同的条件下,施用不同形态氮肥对小白菜地上部及根系吸收铅有显著影响;适量的NH5NO3不会对小白菜地上部造成显著影响,增施Ca(NO3)2也不会造成小白菜地上部含铅量的继续增加;各施氮处理的土壤pH较不施氮处理的土壤pH均有不同程度的降低,且以(NH4)2SO04处理的土壤pH下降幅度最大,施用Ca(NO3)2的处理的土壤pH变化不显著;氮肥在一定程度上会影响土壤中各形态含铅量,其中对交换态、碳酸盐结合态、无定形氧化锰结合态、无定形氧化铁结合态及有机结合态含铅量影响较大,但并未改变各形态铅的分布顺序;小白菜吸收的铅主要来源于土壤中的交换态铅,但也可吸收部分碳酸盐结合态铅、铁锰氧化物结合态铅及有机结合态铅,甚至可吸收部分残渣态铅。
Pot experiments of growing pakchoi on the Pb contaminated rice paddy soil were conducted to determine the effects of using nitrogen fertilizer on distribution of Pb in the soil; 5 N fertilizers (NH4NO3, NH4Cl, (NH4)2SO4, Ca(NO3 )2, CO(NH2 )2 ) at 4 doses were applied 4 times (totaling 0,100, 200, 300 mg/kg DW) during the 60 d test period. The experimental results (average of 4 replicate runs) showed that the use of N fertilizers., 1) increased the lead content of pakchoi shoot, with small increases due to the additions of NH4 NO3 and a low dose of Ca(NO3 )2, 2) with the exceptions of a low dose of NH4 NO3 and high doses of (NH4)2SO4, decreased the lead content of pakchoi root, 3) affected the distribution of various forms of Pb in the soil, with more changes found in exchangeable, carbonate, Mn- and Fe- and organic-complexed Pb,but did not change the abundance order, and 4) promoted the extraction of soluble and exchangeable Pb. Using NH4NO3 as the primary N fertilizer at a dose of 4200 mg/kg DW will prevent the accumulation of Pb to a toxic level in pakchoi shoot.