磷肥和黑麦草结合修复铅污染贫磷潮土的研究（Remediation of Lead Polluted Chaotu Soil with Low Phosphorus Availability by Phosphorus Fertilizer Amendment and Ryegrass）

在Pb污染土壤中施用磷肥是降低Pb有效性的有效方法.在低磷或高Pb胁迫下,植物根际的一系列变化将促进植物对磷的吸收或对Pb毒性的降低,但低磷胁迫下植物对土壤Pb有效性的影响研究不多.为探讨Pb污染低磷土壤上施用磷肥对Pb有效性、植物吸收Pb的影响及黑麦草(LoliumperenneL.)对土壤Pb有效性的影响,设置0、500和1000mg·kg-13个Pb用量和0、2729mg·kg-1两个普通过磷酸钙磷肥用量,种植黑麦草,0和1000mg·kg-1Pb下设置不种植植物的对照的盆栽试验,植物生长48d后收获,测定植物地上部和根系产量、长度、Pb浓度及土壤DTPA-Pb含量.结果表明,施用磷肥后植物产量和地上部长度增加、根冠比、根系长度和Pb浓度减小,500mg·kg-1Pb用量时,未施用磷肥和施用磷肥时植物产量分别为0.37和1.70g·pot-1,1000mg·kg-1Pb用量时这两个数值分别为0.24和1.50g·pot-1,500mg·kg-1Pb用量时,植物产量与未施Pb处理(产量为0.75g·pot-1)差异显著(p<0.05);施用磷肥后,地上部吸收的Pb的比例和植物体吸收的Pb数量均增加.1000mg·kg-1Pb用量下,植物产量、地上部长度均小于500mg·kg-1Pb用量处理时的水平,而土壤DTPA-Pb浓度、植物Pb浓度、Pb吸收量均大于500mg·kg-1Pb处理,表明2729mg·kg-1普通过磷酸钙用量并不能完全抵消1000mg·kg-1Pb对植物生长的抑制作用.施用磷肥降低了土壤DTPA-Pb含量,但500mg·kg-1Pb用量时降低效果不显著(p>0.05).0mg·kg-1Pb用量下,种植植物的处理土壤DTPA-Pb含量比未种植植物处理高54.3%;1000mg·kg-1Pb处理时,种植植物处理土壤DTPA-Pb含量比未种植植物平均低18.5%.以上结果表明,在0mg·kg-1Pb用量下,植物生长受到了一定程度的磷胁迫.在磷胁迫下,种植植物提高了土壤Pb有效性,而在1000mg·kg-1Pb用量下,不管是否施用磷肥,种植植物均降低了土壤Pb有效性.本研究结果表明,在低磷和高Pb胁迫下,施用水溶性磷肥可降低土壤Pb有效性,促进黑麦草生长,促进Pb向植物地上部转移;在低磷胁迫且无Pb污染条件下,黑麦草对土壤Pb的有效性表现为促进;在高Pb胁迫下,不管是否施用磷肥,黑麦草均可降低土壤Pb有效性.

Remediation of Lead Polluted Chaotu Soil with Low Phosphorus Availability by Phosphorus Fertilizer Amendment and Ryegrass

Phosphorus(P)amendment is an effective way to reduce lead(Pb)availability in Pb polluted soil.When plant is confronted with low phosphorus stress or high Pb stress in soil,changes in plant rhizosphere often promote the P uptake by plant or suppress Pb toxicity to plant.However,the effect of plant on soil Pb availability in soil with low phosphorus availability has not been investigated yet.This work was conducted to explore the effect of P fertilizer on the Pb availability,uptake of Pb by ryegrass and the effect of plant on soil Pb availability in a soil with low P availability. Chaom soil with 2.36mg·kg~(-1)Olsen-P was used in a pot experiment with three Pb rates(0,500 and 1000mg·kg~(-1))and two P fertilizer rates(0 and 2729mg·kg~(-1)in single superphosphorate),ryegrass(Lolium perenne L.)was planted for 48 days.After harvest,yield,length,Pb concentration of shoot and root of ryegrass plants,soil DTPA-Pb content were determined.Results indicated that P fertilizer reduced soil DTPA-Pb concentration,but the effect was not statistically significant at 500mg·kg~(-1) Pb rate(p>0.05).P amendment increased plant yields,shoot length,while decreased shoot/root ratio and plant Pb concentration.Plant yields with and without P amendment were 0.37 and 1.70g·pot~(-1),respectively at 500mg·kg~(-1)Pb rate,while these two values at 1000mg·kg~(-1) Pb rate were 0.24 and 1.50g·pot~(-1),respectively.Compared with the control,whose yield was 0.75g·pot~(-1),P fertilizer increased plant yield significantly at 500mg·kg~(-1)Pb rate(p<0.05).Plant Pb accumulation.the ratio between shoot Pb accumulation and plant Pb accumulation were both improved by P amendment.At 1000mg·kg~(-1)Pb rate,the planted soil had lower DTPA-Pb content than the unplanted soil,whether spiked with P or not,however,the difference was not significant(p<0.05),because the plant uptake of Pb only accounted for 1.06% of the spiked Pb,this result indicated that the plant may very likely decrease the soil Pb availability by its rhizosphere process.At 0mg·kg~(-1) Pb rate.DTPA-Pb of the planted soil was 54.3% higher than the unplanted soil.At 1000mg·kg~(-1)Pb rate,soil DTPA-Pb content,plant Pb concentration,plant Pb uptake were all larger than the 500mg·kg~(-1)Pb rate treatment,while plant yield,plant shoot length lower than 500mg·kg~(-1)Pb treatment,whether spiked with P fertilizer or not,indicating that the present P fertilizer rate was not high enough for compensating the toxicity at 1000mg·kg~(-1)Pb rate.These results suggest that phytoavailability of Pb in soil with low P availability and high Pb availability soil can be reduced markedly by soil amendment with water-soluble phosphorus fertilizer;in soil with low phosphorus and Pb availability,planting improves Pb availability,while in soil with low P availability and high Pb availability,whether spiked with P fertilizer or not,planting reduces Pb availability.