Templated Mesoporous Silica Outer Shell for Controlled Silver Release of a Magnetically Recoverable and Reusable Nanocomposite for Water Disinfection.

In this work, we encapsulated Fe3O4@SiO2@Ag (MS-Ag), a bifunctional magnetic silver core-shell structure, with an outer mesoporous silica (mS) shell to form an Fe3O4@SiO2@Ag@mSiO2 (MS-Ag-mS) nanocomposite using a cationic CTAB (cetyltrimethylammonium bromide) micelle templating strategy. The mS shell acts as protection to slow down the oxidation and detachment of the AgNPs and incorporates channels to control the release of antimicrobial Ag+ ions. Results of TEM, STEM, HRSEM, EDS, BET, and FTIR showed the successful formation of the mS shells on MS-Ag aggregates 50-400 nm in size with highly uniform pores ∼4 nm in diameter that were separated by silica walls ∼2 nm thick. Additionally, the mS shell thickness was tuned to demonstrate controlled Ag+ release; an increase in shell thickness resulted in an increased path length required for Ag+ ions to travel out of the shell, reducing MS-Ag-mS' ability to inhibit E. coli growth as illustrated by the inhibition zone results. Through a shaking test, the MS-Ag-mS nanocomposite was shown to eradicate 99.99+% of a suspension of E. coli at 1 × 106 CFU/mL with a silver release of less than 0.1 ppb, well under the EPA recommendation of 0.1 ppm. This high biocidal efficiency with minimal silver leach is ascribed to the nanocomposite's mS shell surface characteristics, including having hydroxyl groups and possessing a high degree of structural periodicity at the nanoscale or "smoothness" that encourages association with bacteria and retains high Ag+ concentration on its surface and in its close proximity. Furthermore, the nanocomposite demonstrated consistent antimicrobial performance and silver release levels over multiple repeated uses (after being recovered magnetically because of the oxidation-resistant silica-coated magnetic Fe3O4 core). It also proved effective at killing all microbes from Long Island Sound surface water. The described MS-Ag-mS nanocomposite is highly synergistic, easy to prepare, and readily recoverable and reusable and offers structural tunability affecting the bioavailability of Ag+, making it excellent for water disinfection that will find wide applications.

Concentrations of DDTs and dieldrin in Long Island Sound sediment.

The concentrations of three frequently detected organochlorine pesticides (OCPs) and one degradation product, p,p'-DDT, p,p'-DDD, dieldrin, and p,p'-DDE were determined in recently collected (2005-2006) and archived (1986-1989) surficial sediments and sediment cores from Long Island Sound (LIS). The concentration of dieldrin ranged from 0.05 to 5.27 ng g(-1) dry weight in the surficial sediments, and from 0.05 to 11.7 ng g(-1) dry weight in the sediment cores. Total DDXs (the sum of p,p'-DDE, p,p'-DDD and p,p'-DDT) concentrations ranged from 1.31 to 33.2 ng g(-1) in surficial sediments and 1.11 to 66.4 ng g(-1) in sediment cores. The results indicate that the three OCPs and DDE were still widely present in LIS surficial sediments two decades after the use of these pesticides in the United States was banned. In addition, the surficial concentrations did not decrease significantly when compared to the concentrations in archived samples collected two decades ago. Sediments in the western part of LIS were more contaminated (with concentrations in some western sites being still above probable effect levels) than those in the eastern part, probably as a result of the net westward sediment transport in LIS. The three OCPs and DDE were detected at all depths (down to ~50 cm) in the sediment cores, and concentration profiles indicated a depositional sedimentary environment with significant sediment mixing. Such mixing may redistribute OCPs deposited earlier (deeper in sediment bed) to the sediment surface and lead to enhanced persistence of OCP concentrations in surficial sediments.

Estrogens in streams associated with a concentrated animal feeding operation in upstate New York, USA.

Estrogens (estrone, 17 alpha-estradiol, 17beta-estradiol, and estriol) in three headwater streams within a concentrated animal feed operation (CAFO) site were monitored on a monthly base for a year (November 2006-October 2007). This CAFO is certified as organic (no growth promoters are administrated) and uses many Whole Farm Planning practices (e.g., 12-month-capacity waste storage lagoons). In general, estrogen concentrations in the streams are low (<1 ng L(-1)), and appeared to increase in spring, likely due to the mobilization of estrogens from soils upon snow melting/precipitation. Estrogens were detected in the streams during dry periods, indicating the contribution of estrogens from groundwater. The low concentrations of estrogens in stream water were probably the result of the long residence time (approximately 8 months) of the manure in the lagoons where most of the estrogens were degraded during storage. An analysis of liquid manure at the beginning of manure application season (after approximately 8 months storage) showed that over 99.8% of the estrogens potentially excreted by the cows were degraded. Moreover, about 90% of the estrogens in the liquid manure were associated with particulates larger than 0.7 microm. Batch experiments with spiked deuterium-labeled 17beta-estradiol-16,16,17-d(3) (d(3)-E2 beta) in the liquid manure demonstrated sorption of d(3)-E2 beta onto particulates in the liquid manure, and rapid degradation of d(3)-E2 beta in the aqueous phase and on particulates of the liquid manure under aerobic conditions.

Persistent chlordane concentrations in Long Island Sound sediment: implications from chlordane, 210Pb, and 137Cs profiles.

Concentrations of chlordane, a banned termiticide and pesticide, were examined in recently collected surficial sediment (10 sites) and sediment cores (4 sites) in Long Island Sound (LIS). The highest chlordane concentrations were observed in western LIS, near highly urbanized areas. Chlordane concentrations did not decrease significantly in the past decade when compared to the data collected in 1996, consistent with the observation of near-constant chlordane levels in blue mussel tissues collected during the same time period. Chlordane concentrations in many of the sites exceeded levels above which harmful effects on sediment-dwelling organisms are expected to frequently occur. Chlordane concentrations in two of the four sediment cores showed a peak below the sediment surface, suggesting reduced chlordane inputs in recent years. The lack of a chlordane concentration maximum below the sediment surface in the other two cores, coupled with the lack of a well-defined 137Cs peak, indicated significant sediment mixing. Simulations of 137Cs and 210Pb profiles in sediment cores with a simple sediment-mixing model were used to constrain both the deposition rate and the bioturbation rate of the sediment. Simulations of the chlordane profiles indicated continued chlordane input to LIS long after chlordane was phased out in the U.S. Continued chlordane input and significant sediment mixing may have contributed to the persistent chlordane concentrations in surficial sediment, which poses long-term threats to benthic organisms in LIS.

Lack of enantioselective microbial degradation of chlordane in Long Island Sound sediment.

Numerous studies have examined the enantiomeric compositions of trans- and cis-chlordane in soils (agricultural, background, and house foundation soils) and in the atmosphere. In contrast, little is known aboutthe enantiomeric compositions of chlordane in sediment. In this work, surficial sediments and sediment cores were collected at various sites in Long Island Sound (LIS) previously surveyed by the National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends (NS&T) Program. Archived surficial sediments at selected sites were acquired from the NS&T Specimen Bank. The chlordanes were racemic or nearly racemic in most archived and recently collected sediments, indicating thatthe enantiomeric compositions of the sources of chlordane to LIS sediment did not change in the past two decades, and that house foundation soils are likely the major source of chlordanes to LIS. Invariant enantiomeric compositions temporally in surficial sediments and at different depths in sediment cores clearly indicate the lack of enantioselective biodegradation in LIS sediment, in striking contrast to the widely observed enantioselective biodegradation of chlordanes in soils.