Many industrial wastewaters are contaminated with both heavy metal ions and organic compounds, posing a major threat to public health and the environment. In this study, magnetic nanoparticle adsorbents, namely Mag-PCMA-T, which contain a maghemite core and a silica mesoporous layer that permanently confines surfactant micelles within the mesopores, were synthesized to achieve simultaneous removal of polycyclic aromatic hydrocarbons (PAHs) (1mg/L) and metal contaminants (1mg/L). The individual removal efficiency of Cd(2+) and acenaphthene using Mag-PCMA-T was evaluated under a range of initial ion concentrations and adsorbent dosages, as well as the competitive adsorption with Cd(2+) and acenaphthene simultaneously present. The isotherms and kinetics of Cd(2+) and acenaphthene sorption onto Mag-PCMA-T were determined. Mag-PCMA-T removed >85% of the acenaphthene in <30min, with relatively high sorption capacity (up to 1060mg/kg). Mag-PCMA-T also exhibited high sorption capacity for Cd(2+) (up to 2250mg/kg). The simultaneous sorption performance was stable across a wide pH range (4-9) as well as in the presence of competitive metal ions (Ca(2+) and Mg(2+)) or natural organic matters. The Mag-PCMA-T can be regenerated and reused, providing a sustainable, fast, convenient, and efficient approach for water treatment.

Geomorphologists have studied and debated over the processes responsible for natural riffle-pool maintenance for decades. Most studies have focused on small wadable rivers, but they lack much description of overbank flood conditions or a spatially explicit characterization of morphodynamics. In this study, 1-m horizontal resolution digital elevation models were collected from a riffle-pool-run sequence before and after an overbank flood with a 7.7-year recurrence interval on the relatively large gravel-bed lower Yuba River, California. Digital elevation model differencing was used to quantify the magnitude and pattern of flood-induced morphodynamic change. Cross section based analysis and two-dimensional hydrodynamic modeling of flows ranging from 0.147 to 7.63 times bankful discharge were completed to evaluate the hydraulic mechanisms responsible for the observed topographic changes. One key finding was that riffle-pool relief increased by 0.42 m, confirming the occurrence of natural hydrogeomorphic maintenance. Spatially complex patterns of scour and deposition exceeding 0.15 m at the scale of subwidth morphological units were reasonably predicted by the two-dimensional mechanistic model that accounts for convective acceleration. The one-dimensional cross section based method underperformed the two-dimensional model significantly. Consequently, multiple scales of channel non-uniformity and a dynamic flow regime caused the observed maintenance of the pool-riffle morphology through the mechanism of "flow convergence routing" proposed by MacWilliams et al. [MacWilliams, M.L., Wheaton, J.M., Pasternack, G.B., Kitanidis, P.K., Street, R.L., 2006. The flow convergence-routing hypothesis for riffle-pool maintenance in alluvial rivers. Water Resources Research 42, W10427, doi:10.1029/2005WR004391]. © 2009 Elsevier B.V. All rights reserved.

Cu-containing nanopesticides are increasingly being used as fungicides in modern agriculture. However, their fate, transport and toxicity in crop plants have been less studied. Here, we exposed 3 week-old cucumber plants cultivated in artificial media to different concentrations of a Cu(OH)2 nanopesticide (0, 2.5 and 25 mg) for 7 d. The physiological and molecular responses were investigated. In order to elucidate the contribution of copper ions to the response, we also exposed the plants to CuSO4. Results showed that the Cu(OH)2 nanopesticide did not reduce the photosynthetic pigment production. In contrast, 10 mg Cu ions induced a significant decrease in photosynthetic pigment levels (around 25%) and leaf chlorosis symptoms. Foliar exposure to 25 mg Cu(OH)2 nanopesticide induced significant changes in mRNA levels of antioxidant and detoxification-related genes; 6 genes (SOD, GPX4, GPX, MDAR, POD, WRKY6) were up-regulated up to 9-fold, and one (cAPX) was down-regulated by 32%. The Cu(OH)2 nanopesticide at both dose levels (2.5 and 25 mg per plant) decreased the transcript production of a stress-related gene (DNAJ) by 40% and 80%, respectively. The up-regulation of the transcript levels of SOD, GPX4, GPX, MDAR, POD, and WRKY6 and down-regulation of DNAJ was also observed in CuSO4 treated plants (with increases of up to 7-fold), indicating that most of the responses are due to released copper ions. We postulate that the increased mRNA levels of antioxidants and detoxification enzymes reflect plant adaptation to over-generated reactive oxygen species (ROS) triggered by copper ions. The activated genes could serve as potential biomarkers of nanopesticide exposure and may be applicable to other plant/Cu nanopesticide interactions.