Evaluation of irrigation water quality guidelines for arsenic and lead, with implications for food and feed safety

Dissertation (MSc)--University of Pretoria, 2019.

As mining and industry continue to impact agricultural lands and waterways, and as competition for access to fresh water increases, the agricultural industry must adapt to grow crops in increasingly polluted lands using ever more contaminated water sources. As a result, the likelihood that crops grown under such conditions could pose a food safety risk is set to rise. This research assesses the extent to which potentially hazardous trace elements, As and Pb, present in irrigation water at concentrations deemed acceptable by the Irrigation Water Quality Guidelines, impact the food (and feed) safety of crops. Four crops are investigated under two glasshouse trials. The first assesses foliar absorption of As and Pb under irrigation to the aboveground biomass and the second assesses root uptake of As and Pb via the effects of medium- to long-term irrigation programs. Results indicate that under such trace element loaded conditions, some crop parts exceed food (or feed) safety thresholds, with concentrations ranging from 0.01 mg.kg-1 to 33.38 mg.kg-1 As, and 0.01 mg.kg-1 to 62.41 mg.kg-1 Pb, on a dry mass basis. Leafy vegetables present the highest food safety risk. Therefore, if international food safety standards for fresh produce are to be adhered to, the Irrigation Water Quality Guidelines for As and Pb should be critically reviewed so as to negate all possible future contamination of fresh produce as a result of irrigation inputs. A food (and feed) safety consequence matrix is proposed as a means of modelling the effect of irrigating according to the Irrigation Water Quality Guidelines on food (and feed) safety.

Plant Production and Soil Science

MSc

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