Applied Injected Air into Subsurface Drip Irrigation: Plant Uptake of Pharmaceuticals and Soil Microbial Communities

The growing global food security crisis is complicated by the need for increased crop production with less arable land and limited water resources. Reuse of treated wastewater for agricultural irrigation is becoming more common, often paired with other conservation measures such as subsurface drip irrigation (SDI). Passively injecting air into SDI systems increases crop yields and overcomes root zone wetting issues. However, when used with treated irrigation water, contaminants in the water might be taken up by the crops. This paper investigates the impact of air-injected water containing caffeine, carbamazepine, and gemfibrozil on plant uptake and soil microbial communities in Salanova lettuce (Lactuca sativa). Aerated lettuce yielded higher plant mass and root length. The use of air-injected water reduced the uptake of caffeine and gemfibrozil and increased the uptake of carbamazepine. Gemfibrozil and carbamazepine were primarily detected in leachate, while caffeine was observed in the soil samples. Injected air significantly impacted (p-value<0.001) the fate and transport of gemfibrozil. Injection of pharmaceutically active compounds and the presence/absence of injected-air created a variation in soil microbial communities.