Ascorbic acid, β-carotene, sugars, phenols, and heavy metals in sweet potatoes grown in soil fertilized with municipal sewage sludge

George F. Antonious, Sam O. Dennis, Jason M. Unrine, John C. Snyder

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Municipal sewage sludge (MSS) used for land farming typically contains heavy metals that might impact crop quality and human health. A completely randomized experimental design with three treatments (six replicates each) was used to monitor the impact of mixing native soil with MSS or yard waste (YW) mixed with MSS (YW + MSS) on: i) sweet potato yield and quality; ii) concentration of seven heavy metals (Cd, Cr, Mo, Cu, Zn, Pb, and Ni) in sweet potato plant parts (edible roots, leaves, stem, and feeder roots); and iii) concentrations of ascorbic acid, total phenols, free sugars, and β-carotene in sweet potato edible roots at harvest. Soil samples were collected and analyzed for total and extractable metals using two extraction procedures, concentrated nitric acid (to extract total metals from soil) as well as CaCl2 solution (to extract soluble metals in soil that are available to plants), respectively. Elemental analyses were performed using inductively coupled plasma mass spectrometry (ICP-MS). Overall, plant available metals were greater in soils amended with MSS compared to control plots. Concentration of Pb was greater in YW than MSS amendments. Total concentrations of Pb, Ni, and Cr were greater in plants grown in MSS+YW treatments compared to control plants. MSS+YW treatments increased sweet potato yield, ascorbic acid, soluble sugars, and phenols in edible roots by 53, 28, 27, and 48%, respectively compared to plants grown in native soil. B-carotene concentration (157.5 μg g-1 fresh weight) was greater in the roots of plants grown in MSS compared to roots of plants grown in MSS+YW treatments (99.9 μg g-1 fresh weight). Concentration of heavy metals in MSS-amended soil and in sweet potato roots were below their respective permissible limits.

Original languageEnglish
Pages (from-to)112-121
Number of pages10
JournalJournal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes
Issue number2
StatePublished - Feb 2011

Bibliographical note

Funding Information:
We would like to thank Eric Turley, Regina Hill, and Kentucky State University farm crew for maintaining the field plots. This investigation was supported by a grant from USDA/CSREES to Kentucky State University under agreements Nos.KYX-10–08-43P & KYX-2006–1587.


  • Biosolids
  • Cadmium
  • Lead
  • Nickel
  • Nutritional composition
  • Soil conditioners
  • Sweet potato quality

ASJC Scopus subject areas

  • Food Science
  • Pollution


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