With the fast-developing nanotechnology, metal based nanoparticles (NPs) production and application are increased significantly. These metal based NPs can enter agricultural land through both direct and indirect pathways. This review presents an overview of the fate and transport of metal based NPs and their interactions with plants in agricultural ecosystem system. The physical chemical properties of both metal based NPs (e.g. size, surface charge, surface coating) and soil matrix (e.g. pH, ionic strength, mineral composition, dissolved organic matter) all play important roles in determining the mobility, transformation and potential risks of metal based NPs in plant and soil system. NPs can be accumulated to plant roots and translocated to other parts of the plants. The properties of both plant and metal based NPs are playing critical roles to this process. Systematic research of metal based NPs in environmentally relevant concentrations and conditions is needed for the future study.

Sulfamethoxazole (SMX) and sulfapyridine (SPY), two representative sulfonamide antibiotics, have attracted much attention recently because of their potential ecological risks. This work systematically investigated the adsorption characteristics of SMX and SPY on carbon nanotubes (CNTs), a newly introduced nano-adsorbent, under various physicochemical conditions. Laboratory batch adsorption experiments and mathematical models were used to determine the adsorption kinetics and isotherms of the two antibiotics to the CNTs. We found that SMX and SPY had very fast adsorption kinetics to the CNTs, which could be simulated with both the pseudo-second-order and the intraparticle diffusion models. These results suggest that the adsorption of the antibiotics to the CNTs were controlled by surface adsorption and intraparticle diffusion processes. Isotherm studies showed that sonication-aided dispersion slightly increased the adsorption of the antibiotics to the CNTs probably because the dispersion process might increase CNT surface area. When solution pH increased from 3.0 to 9.0, the Langmuir maximum sorption capacities of the antibiotics to the CNTs decreased from 98.0 to 18.6 mg/g (SMX) and from 108.6 to 83.2 mg/g (SPY), indicating pH is a controlling factor of the removal of the two antibiotics in aqueous solutions. We also found that the Langmuir adsorption capacity of the CNTs decreased slightly for both SMX and SPY when more adsorbents were in the solution. The findings from this study suggest that CNTs can be used as a high efficiency adsorbent to removal antibiotics from aqueous solution under various conditions.