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dc.contributor.advisorAngle, Jay Sen_US
dc.contributor.authorWang, Shengchunen_US
dc.date.accessioned2005-02-02T06:42:15Z
dc.date.available2005-02-02T06:42:15Z
dc.date.issued2004-11-29en_US
dc.identifier.urihttp://hdl.handle.net/1903/2083
dc.description.abstractThe major aims of this research were to determine whether reducing soil pH can enhance phytoextraction and to examine the ecological risks of reducing pH. Two soils differing in Cd and Zn concentrations were used and adjusted to 5 or 6 different pH levels ranging from 7.27 to 4.74 and seeded with a hyperaccumulator of Cd and Zn, Thlaspi caerulescens. Plants were harvested after six months, the pH were restored to above 6.5, incubated for 6 months. Soils were analyzed for biological activities and microbial population changes after both pH adjustments. Reducing pH significantly (p=0.05) enhanced plant metal uptake. For the high metal soil, plant grew best at the lowest pH treatment (4.74) and the highest metal concentration was at the second lowest pH treatment (5.27). For the low metal soil, due to low pH induced Al and Mn toxicity, plant growth and metal uptake were highest at the intermediate pH level (6.07). Metal sequential extraction results further verified that reducing pH redistributed Cd and Zn among five fractions. The most soluble metal form (F1) was greatly increased. In addition, T. caerulescens was able to differentially utilize Cd in all 5 fractions while it could only access Zn from the F1 and F2 pools. Reducing soil pH significantly reduced a number of soil biological activities and shifted the community structure at different levels. Generally, soil biological activities were more sensitive than soil microbial populations to pH change. Good indicators of soil pH status were acid phosphatase activity, alkaline phosphatase activity, acid to alkaline phosphatase activity ratio, arylsulphatase, nitrification potential, soil microbial biomass C and N, and population of rhizobium. After raising pH to > 6.5, negatively impacted soil parameters were partially restored to original levels. Soil biological activities showed lower recovery than soil microbial populations. The threshold pHs were 6.1 and 5.3 for low and high metal soils, respectively. Above this value, most soil biological activities and all microbial populations returned to background levels within a short period.en_US
dc.format.extent1800689 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.titleEfficiency and Ecological Risks of Reducing Soil pH during Thlaspi caerulescens Phytoextraction of Cadmium and Zincen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentNatural Resource Sciencesen_US
dc.subject.pqcontrolledBiology, Microbiologyen_US
dc.subject.pqcontrolledAgriculture, Soil Scienceen_US
dc.subject.pqcontrolledBiology, Ecologyen_US
dc.subject.pquncontrolledSoil microbial ecosystemen_US
dc.subject.pquncontrolledpHen_US
dc.subject.pquncontrolledThlaspi caerulescensen_US
dc.subject.pquncontrolledPhytoextractionen_US
dc.subject.pquncontrolledCadmiumen_US
dc.subject.pquncontrolledZincen_US


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