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723641 
Journal Article 
Influence of iron plaque on accumulation of lead by yellow flag (Iris pseudacorus L.) grown in artificial Pb-contaminated soil 
Zhong, S; Shi, J; Xu, J 
2010 
Yes 
Journal of Soils and Sediments
ISSN: 1439-0108
EISSN: 1614-7480 
10 
5 
964-970 
WOS:000278741300020 
The relationship between plant absorption and accumulation
of heavy metals and the effect of iron plaque on roots of wetland plants are unknown, especially
for plants grown in heavy metal-contaminated soil. This experiment was designed to study the
effects of iron addition on the formation of iron plaque in the rhizosphere of the wetland plant
species Iris pseudacorus L. in artificial Pb-contaminated soil and the effects of iron plaque on
Pb accumulation by plants. Soil was collected from 0- to 30-cm depth of a clayey illitic thermic
typic epiaqualfs in an abandoned paddy field in Jiaxing of Zhejiang Province, China. The seeds of
yellow flag (I. pseudacorus L.) were germinated in soil mixed with vermiculite and grown for 30
days. Three treatments of iron (0, 100, and 500 mg Fe kg(-1) as FeSO4) were added when uniform
seedlings were transplanted into plastic pots filled with 1.0-kg soil, which had been previously
treated with four treatments of Pb [0, 100, 500, and 1,000 mg Pb kg(-1) as Pb(NO3)(2)] and
waterlogged for 72 days. The yellow flags were grown in a greenhouse for 60 days. The plaque on
roots was extracted using the cold DCB (dithionite-citrate-bicarbonate) technique. The plant
samples were digested with 10 mL concentrated nitric acid by microwave digestion. The
concentration of Fe and Pb were determined using atomic spectrophotometry (NovAA300, Germany).
The amount of iron plaque on the roots of yellow flag (I. pseudacorus L.) was markedly affected
by Fe addition but not by Pb addition. The total Pb accumulated in plants was increased initially
and then decreased with the addition of Fe in three lower Pb treatments (0, 100, and 500 mg Pb
kg(-1)) but decreased with more Fe addition in the 1,000 mg Pb kg(-1) treatment. The pH value was
decreased with the addition of more iron, which increases Pb availability, and heavy doses of
iron caused iron toxicity. Plant growth decreased due to iron toxicity at higher iron additions
(500 mg kg(-1)), while Pb accumulation decreased. Intermediate levels of iron supply (100 mg kg
(-1)) enhanced Pb absorption in roots, which improved phytoremediation effectiveness. Iron supply
enhanced the amount of iron plaque and increased both Pb adsorbed on the roots and Pb uptake by
plants. However, plant growth was inhibited by iron toxicity at high iron dose (500 mg kg(-1))
and biomass decreased. The intermediate iron dose (100 mg kg(-1)) generally enhanced Pb
absorption and accumulation, which enhances the ability of yellow flag to remove Pb from Pb-
contaminated soils. 
Iron plaque; Lead; Phytoremediation; Waterlogged soil; Yellow flag