水溶性磷和铅在潮土中有效性变化过程

在人为加入500mg.kg-1水溶铅的土壤中分别加入Ca(H2PO4)2.H2O和KH2PO4n(P)∶n(Pb)=1.95∶1],在30d内的不同时间采样,测定土壤磷有效性(Olsen-P)和铅有效性(DTPA-Pb)。结果表明,KH2PO4处理在1～4d土壤磷有效性略高于Ca(H2PO4)2.H2O处理,此后二者磷有效性差异较小;土壤磷有效性在1～18d内快速下降,此后磷有效性下降变缓。在1～4和24～30d,Ca(H2PO4)2.H2O处理铅有效性高于KH2PO4处理,其余时间二者铅有效性差异不大;铅有效性的快速下降主要发生在1～4d,此后下降较慢。数据分析表明,土壤b(Olsen-P)下降量与b(DTPA-Pb)下降量比值为0.893～10.9。加铅土壤中施入Ca(H2PO4)2.H2O后分别保持15%、30%和45%土壤质量含水量,10d后各处理土壤铅有效性差异不显著(P>0.5),而土壤磷有效性依次增加且差异显著(P<0.05)。铅污染土壤中施入水溶性磷酸盐后磷或铅有效性的下降均仅是另一元素有效性下降的部分原因。

Availability Dynamics of Soluble Lead and Phosphorus in a Chaotu Soil

A soil spiked with 500 mg·kg-1 Pb was amended with calcium dihydrogen pyrophosphate(CDP) or potassium dihydrogen pyrophosphate(PDP) at the rate of P∶Pb=1.95∶1(mol∶mol),and was sampled periodically during 30 days for Pb and phosphorus availability determination.The results indicated that,phosphorus availability of soil amended with PDP was a little higher than that amended with CPD during the first 4 d,after that,no obvious difference of phosphorus availability between these two treatments was detected.Phosphorus availability decreased faster during 1 to 18 d after amendment,followed by slower decrease.PDP amended soils had higher Pb availability during 1 to 4 d and 24 to 30 d than the CDP treatment,no obvious difference was observed during the rest time.Rapid decrease of Pb availability appeared only during 1 to 4 d.Data analysis indicated that the ratio between phosphorus availability decrease and that of Pb(mol∶mol) ranged between 0.893 and 10.9.No significant difference was observed for the Pb availability(P>0.5) while significant difference was found for phosphorus availability(P<0.05) after Pb-spiked soil was amended with PDP and kept at 10%,30% and 45% water contents and let stand for 10 d.The results of this work suggest that after Pb polluted soil is amended with soluble phosphorus,the availability decrease of phosphorus or Pb is only part of the reason of the availability decrease of another element.