Uptake and Accumulation of Pharmaceuticals in Vegetables.

Land application of animal manure/sewage sludge and irrigation with reclaimed water in agricultural production result in the dissemination of pharmaceuticals in agroecosystems, which can be taken up and accumulate in vegetable crops. In this study, the accumulation and transportation of six pharmaceuticals caffeine, carbamazepine, lamotrigine, trimethoprim, monensin sodium and tylosin in lettuce were examined using hydroponic experimental settings. The uptake of target pharmaceuticals by mature lettuce was measured from 0 to 144 h. The results revealed that for caffeine and carbamazepine greater pharmaceutical concentrations were found in lettuce shoots than that in roots. Lamotrigine, trimethoprim, monensin sodium and tylosin appeared to more accumulate in lettuce roots than in shoots. Sorption by vegetable tissues from nutrient solution showed that lettuce roots sorbed more lamotrigine and trimethoprim than caffeine and carbamazepine, monensin sodium and tylosin. These results demonstrated that lamotrigine and trimethoprim, with relatively strong affinity for plant root constituents, tend to accumulate in lettuce roots rather than in shoots. Conversely, caffeine and carbamazepine were observed to significantly transport to lettuce shoots with water transpiration flow, which could be due to their weak sorption by root constituents. Monensin sodium and tylosin also demonstrated a weak affinity to lettuce root constituents, but manifested a great accumulation in lettuce roots. This could be due to the sieve of plasmodesmata on the cell wall of lettuce root obstruct the large molecular size of monensin sodium and tylosin, with molecular weight of 693 and 916.