Investigation into Effect of Soil Moisture Depletion on Vegetable Crop Uptake of Microcontaminants under Recycled Water Irrigation
Water Management and Conservation Research
2013 Annual Report
1a.Objectives (from AD-416):
Reclaimed wastewater has been increasingly used for irrigation throughout the world, but questions remain about potential public health risks. The accumulation of emerging contaminants in crops has been proposed but no data exists regarding the uptake of these compounds by crops consumed fresh by humans.
1b.Approach (from AD-416):
Greenhouse experiments will be conducted to determine the potential for 4 compounds found in treated effluent to accumulate in crops eaten fresh. The compounds selected are carbamazepine, lincomycin, ibuprofen, and caffeine. Crops will be irrigated with the known concentrations of the compounds irrigated at different soil moisture depletions. Concentrations of the compounds will be determined from the edible portions of the crops. Documents Reimbursable with U of HI (AFRI). Log 42145.
This research relates to objective 2 of the inhouse project plan, "Determine the processes that govern the fate and transport of emerging contaminants, pathogens, and nutrients found in treated wastewater used for irrigation to provide a research basis for potential regulation of these constituents". The uptake of 20 human drugs by nasturtiums was measured. It was found that the highest drug concentrations were found in the roots and leaves. Total drug uptake was greatest for the topical anesthetic lidocaine with 78.5% of the applied drug accumulating in the plant and no uptake was found for the antibiotics oxytetracycline and triclosan. Nine of the compounds accumulated less than 1% of the applied compound and only three of the compounds had accumulations greater than 10%. Lidocaine, carbamazepine and diphenhydramine accumulation indicated that there is a potential hazard from these three drugs, however, the actual mass of these compounds in the entire plant is 10 to 50 times lower than a typical single recommended dose. One experiment to measure the effect of soil moisture depletion on the uptake of the human drugs atenolol, ofloxacin and diclofenac has been conducted using irrigation water containing the drugs at 10 times the average concentration found in typical sewage effluent. The crop has been grown, harvested and freeze dried. Currently the samples are being extracted, cleaned and concentrated for compound analysis. Additionally, a second experiment at 5 times the average drug concentration is being harvested.