title: Phytoavailability, human risk assessment and transfer characteristics of cadmium and zinc contamination from urban gardens in Kano, Nigeria.
abstract: BACKGROUND
  Quantitative data about phytoavailability and transfer into consumed plant parts for heavy metals in intensively managed urban vegetable production areas of sub-Saharan Africa are scarce. We therefore studied the transfer of zinc (Zn) and cadmium (Cd) from soil to the root and subsequent translocation to edible portions of four vegetables in six urban gardens.
  
  
  RESULTS
  While respective diethylenetriaminepentaacetic acid (DTPA)-available Zn and Cd concentrations ranged from 18 to 66 mg kg(-1) and from 0.19 to 0.35 mg kg(-1) , respectively, in soils, total Zn and Cd were 8.4-256 mg kg(-1) and 0.04-1.7 mg kg(-1) in shoot parts. Metal transfer factor (MTF) ratios were higher in Zn (0.2-0.9) than in Cd (0.1-0.6). Our data suggest that total Zn concentration in soil is a reliable indicator to assess its transfer from soil to crop in lettuce, carrot and parsley, while for Cd DTPA-extractable concentration may be used to estimate soil-crop transfer of Cd in amaranthus and carrot. Overall, Cd was more easily translocated to the aerial plant parts than Zn.
  
  
  CONCLUSIONS
  Zinc and Cd accumulation by vegetables in our soils is mainly a metabolically controlled process. Such accumulation can contaminate the ecosystem but under our conditions intake and ingestion of these metals will likely have to occur over a prolonged period to experience health hazard.
authors.affiliation: Department of Soil Science, Faculty of Agriculture, Ahmadu Bello University, Zaria, Nigeria.
authors.forename: Nafiu
authors.initials: N
authors.lastname: Abdu
authors.forename: John O
authors.initials: JO
authors.lastname: Agbenin
authors.forename: Andreas
authors.initials: A
authors.lastname: Buerkert
mesh_terms: D027721:Amaranthus / Q000737:chemistry; D001692:Biological Transport; D002104:Cadmium / Q000032:analysis*; D018552:Daucus carota / Q000737:chemistry; D004781:Environmental Exposure / Q000032:analysis*; D005506:Food Contamination; D018545:Lactuca / Q000737:chemistry; D019216:Metals, Heavy / Q000032:analysis*; D009549:Nigeria; D004369:Pentetic Acid / Q000378:metabolism; D028528:Petroselinum / Q000737:chemistry; D035261:Plant Components, Aerial / Q000737:chemistry; D018517:Plant Roots; D018570:Risk Assessment; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis; D014675:Vegetables / Q000737:chemistry*; D015032:Zinc / Q000032:analysis*
chemical_list: D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D004369:Pentetic Acid; D015032:Zinc