4.7 Article

Cadmium uptake by onions, lettuce and spinach in New Zealand: Implications for management to meet regulatory limits

Journal

SCIENCE OF THE TOTAL ENVIRONMENT
Volume 668, Issue -, Pages 780-789

Publisher

ELSEVIER
DOI: 10.1016/j.scitotenv.2019.03.010

Keywords

Cadmium uptake; Cultivar; Onion; Spinach; Plant-soil relationship

Funding

  1. Fertiliser Association of New Zealand
  2. Taranaki Regional Council
  3. Manaaki Whenua Landcare Research
  4. Foundation for Arable Research
  5. Waikato Regional Council
  6. DairyNZ
  7. Flour Millers Association
  8. Bakers Industry Research Trust
  9. Greater Wellington Regional Council
  10. Ministry for the Environment
  11. Beef + Lamb NZ
  12. Bay of Plenty Regional Council
  13. Vegetable New Zealand
  14. OnionsNZ
  15. Gisborne District Council
  16. Environment Canterbury
  17. Marlborough District Council
  18. Ministry for Primary Industries

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Paired soil and plant samples collected from the main commercial growing areas for onions (Allium cepa), lettuce (Lactuca sativa) and spinach (Spinacia olearacea) in New Zealand were used to assess the influence of plant and soil factors on cadmium (Cd) uptake in these crops. Differences in Cd concentration between eight lettuce sub-types were not consistent across sites, nor were differences in Cd concentrations in three crisphead cultivars assessed at two sites. Similarly, differences in Cd concentrations between four onion cultivars were inconsistent across sites. Mean lettuce Cd concentrations in eight lettuce varieties (range 0.005-0.034 mg.kg(-1) (fresh weight, FW) were markedly lower than those in baby leaf and bunching spinach, (range 0.005-0.19 mg.kg(-1) FW). Significant regional variation was observed in Cd concentrations in one onion cultivar (mean range 0.007-0.05 mg.kg(-1) FW). Soil Cd concentration, pH and region were statistically significant predictors of onion Cd concentration, explaining low (38% for soil Cd and pH) to moderate (50% for all three parameters) percentage of the variation. Soil Cd concentration and exchangeable magnesium or total carbon were statistically significant predictors of Cd concentration in baby leaf and bunching spinach, respectively, explaining a moderate percentage (49% and 42%) of the variation in Cd concentration. Increasing pH and soil carbon may assist in minimising Cd uptake in onion and bunching spinach, respectively. The low to moderate proportion of explained variation is partly attributable to the narrow range in some measured soil properties and indicates factors other than those assessed are influencing plant uptake. This highlights a challenge in using these relationships to develop risk-based soil guideline values to support compliance with food standards. Similarly, the inconsistency in Cd concentrations in different cultivars across sites highlights the need for multi-site assessments to confirm the low Cd accumulation status of different cultivars. (C) 2019 Published by Elsevier B.V.

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