Alteration of Crop Yield and Quality of Three Vegetables upon Exposure to Silver Nanoparticles in Sludge-Amended Soil

The impacts of land application of sludge contaminated with silver nanoparticles (Ag NPs) on crop yield and nutritional quality are relatively unknown. Chili ( Capsicum annuum L.), lettuce ( Lactuca sativa ), and radish ( Raphanus sativus L.) were grown for 52–71 days in soil amended by sludge with or without Ag NPs. Then root-exposed chili and lettuce continued to grow until day 75 and 105, during which they were simultaneously exposed to 107 Ag NPs via leaves for 3 days. Root exposure reduced the yield of lettuce and radish by 42 and 61%. It had minimal effects on essential element (Ca, K, Mg, P, Fe, Mn, and Zn) contents in chili fruits and radish roots or on protein, amino acid, and most essential element contents in lettuce leaves. Exceptions were K and Mg in lettuce leaves, which decreased by ∼25%. Further, root uptake dominated over foliar uptake (86 and 95% of total Ag) in Ag accumulation in younger leaves and flowers of lettuce, as revealed by the stable isotope tracer technique, suggesting unintended residual transgenerational effects of land application of sludge contaminated with Ag NPs. These results guide the agricultural application of Ag NPs in a more efficient and safer manner.