To meet mounting water demands, treated wastewater has become an important source of irrigation. Thus, contamination of treated wastewater by pharmaceutical compounds (PCs) and the fate of these compounds in the agricultural environment are of increasing concern. This field study aimed to quantify PC uptake by treated wastewater-irrigated root crops (carrots and sweet potatoes) grown in lysimeters and to evaluate potential risks. In both crops, the nonionic PCs (carbamazepine, caffeine, and lamotrigine) were detected at significantly higher concentrations than ionic PCs (metoprolol, bezafibrate, clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, sulfamethoxazole, and sildenafil). PCs in leaves were found at higher concentrations than in the roots. Carbamazepine metabolites were found mainly in the leaves, where the concentration of the metabolite 10,11-epoxycarbamazepine was significantly higher than the parent compound. The health risk associated with consumption of wastewater-irrigated root vegetables was estimated using the threshold of toxicological concern (TTC) approach. Our data show that the TTC value of lamotrigine can be reached for a child at a daily consumption of half a carrot (∼60 g). This study highlights that certain PCs accumulated in edible organs at concentrations above the TTC value should be categorized as contaminants of emerging concern.

An increasing number of reports on plant uptake of pharmaceutical compounds (PCs) have been recently published, raising concerns of human exposure through dietary intake. In this study, PC uptake and translocation were evaluated in cucumber and tomato plants to elucidate the effects of PC physicochemical properties, soil type, and irrigation-water quality. Nonionic PCs were taken up and accumulated at higher levels in plants grown in soils of lower organic matter and clay content. While the concentration of most PCs in cucumber and tomato leaves were of similar order, their concentrations in the tomato fruit were much lower than in the cucumber fruit. This is related to differences in fruit physiology. Our data suggest that irrigation with treated wastewater reduces the bioavailability of acidic PCs for uptake by cucumber plants as compared to fresh water irrigation. This study sheds light on factors affecting the uptake of PCs by crops irrigated with treated wastewater, the governing role of PCs' physicochemical properties along with the physiological nature of the plant, soil properties and water quality that together determine uptake, translocation, and accumulation within plant organs. Occurrence of metabolites in plant suggests that PC metabolism has to be evaluated to reveal the total uptake.

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Phosphorus loss from land can be a major factor affecting surface water quality. We studied P-release mechanisms in wetland soils that had been drained and cultivated for four decades and then re-flooded. We measured redox, pH and solution composition in two sites in the field and in four peat and calcareous soils incubated in biogeochemical microcosms. The redox and pH measurements during the 120 days of incubation and the resulting soil solution composition indicated that the main process leading to P release is reductive dissolution of ferric hydroxides on which P was adsorbed and in which P was occluded. The molar Fe:P ratio increased with period of reduction from below 1 in the first week of re-flooding to 15-60 after 120 days. This suggests an increased P-retention capacity upon reoxidation of the soil solution, whether within the soil profile or in the drainage canals. Prolonged flooding of the calcite-poor, gypsumrich peat soils increased the oversaturation of soil solutions with respect to hydroxyapatite and occasionally -Ca 3 (PO 4 ) 2 (c), indicating that in spite of the large Ca concentration, the rate of Ca-P precipitation was insufficient to maintain the saturation status of the Ca-P system. In the calcareous soils the Ca-P system effectively controlled the P activity in soil solution throughout the incubation period. In both cases the precipitation of Ca-P minerals could be an important P-retention mechanism.

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