Novel Dynamic Technique, Nano-DIHM, for Rapid Detection of Oil, Heavy Metals, and Biological Spills in Aquatic Systems.

Numerous anthropogenic and natural particle contaminants exist in diverse aquatic systems, with widely unknown environmental fates. We coupled a flow tube with a digital in-line holographic microscopy (nano-DIHM) technique for aquatic matrices, for in situ real-time analysis of particle size, shape, and phase. Nano-DIHM enables 4D tracking of particles in water and their transformations in three-dimensional space. We demonstrate that nano-DIHM can be automated to detect and track oil spills/oil droplets in dynamic systems. We provide evidence that nano-DIHM can detect the MS2 bacteriophage as a representative biological-viral material and mercury-containing particles alongside other heavy metals as common toxic contaminants. Nano-DIHM shows the capability of observation of combined materials in water, characterizing the interactions of various particles in mixtures, and particles with different coatings in a suspension. The observed sizes of the particles and droplets ranged from ∼1 to 200 µm. We herein demonstrate the ability of nano-DIHM to characterize and distinguish particle-based contaminants in water and their interactions in both stationary and dynamic modes with a 62.5 millisecond time resolution. The fully automated software for dynamic and real-time detection of contaminants will be of global significance. A comparison is also made between nano-DIHM and established techniques such as S/TEM for their different capabilities. Nano-DIHM can provide a range of physicochemical information in stationary and dynamic modes, allowing life cycle analysis of diverse particle contaminants in different aquatic systems, and serve as an effective tool for rapid response for spills and remediation of natural waters.

Novel Technology for the Removal of Brilliant Green from Water: Influence of Post-Oxidation, Environmental Conditions, and Capping.

Chemical dyes are used in a wide range of anthropogenic activities and are generally not biodegradable. Hence, sustainable recycling processes are needed to avoid their accumulation in the environment. A one-step synthesis of Fecore-maghemiteshell (Fe-MM) for facile, instantaneous, cost-effective, sustainable, and efficient removal of brilliant green (BG) dye from water has been reported here. The homogenous and monolayer type of adsorption is, to our knowledge, the most efficient, with a maximum uptake capacity of 1000 mg·g-1, for BG on Fe-MM. This adsorbent was shown to be efficient in occurring in time-scales of seconds and to be readily recyclable (ca. 91%). As iron/iron oxide possesses magnetic behavior, a strong magnet could be used to separate Fe-MM coated with BG. Thus, the recycling process required a minimum amount of energy. Capping Fe-MM by hydrophilic clay minerals further enhanced the BG uptake capacity, by reducing unwanted aggregation. Interestingly, capping the adsorbent by hydrophobic plastic (low-density polyethylene) had a completely inverse effect on clay minerals. BG removal using this method is found to be quite selective among the five common industrial dyes tested in this study. To shed light on the life cycle analysis of the composite in the environment, the influence of selected physicochemical factors (T, pH, hν, O3, and NO2) was examined, along with four types of water samples (melted snow, rain, river, and tap water). To evaluate the potential limitations of this technique, because of likely competitive reactions with metal ion contaminants in aquatic systems, additional experiments with 13 metal ions were performed. To decipher the adsorption mechanism, we deployed four reducing agents (NaBH4, hydrazine, LiAlH4, and polyphenols in green tea) and NaBH4, exclusively, favored the generation of an efficient adsorbent via aerial oxidation. The drift of electron density from electron-rich Fecore to maghemite shells was attributed to be responsible for the electrostatic adsorption of N+ in BG toward Fe-MM. This technology is deemed to be environmentally sustainable in environmental remediation, namely, in waste management protocol.

Athabasca oil sands region snow contains efficient micron and nano-sized ice nucleating particles.

The Athabasca Oil Sands Region (AOSR) in Alberta, Canada, is an important source of atmospheric pollutants, such as aerosols, that have repercussions on both the climate and human health. We show that the mean freezing temperature of snow-borne particles from AOSR was elevated (-7.1 ±â€¯1.8 °C), higher than mineral dust which freezes at ∼ -15 °C and is recognized as one of the most relevant ice nuclei globally. Ice nucleation of nanosized snow samples indicated an elevated freezing ability (-11.6 ±â€¯2.0 °C), which was statistically much higher than snow-borne particles from downtown Montreal. AOSR snow had a higher concentration (∼2 orders of magnitude) of >100 nm particles than Montreal. Triple quadrupole ICP-(QQQ)-MS/MS analysis of AOSR and Montreal snow demonstrated that most concentrations of metals, including those identified as emerging nanoparticulate contaminants, were much more elevated in AOSR in contrast to Montreal: 34.1, 34.1, 16.6, 5.8, 0.3, 0.1, and 9.4 mg/m3 for Cr, Ni, Cu, As, Se, Cd, and Pb respectively, in AOSR and 1.3, 0.3, 2.0, <0.03, 0.1, 0.03, and 1.2 mg/m3 in Montreal snow. High-resolution Scanning Transmission Electron Microscopy/Energy-dispersive X-ray Spectroscopy (STEM-EDS) imaging provided evidence for various anthropogenic nano-materials, including carbon nanotubes resembling structures, in AOSR snow up to 7-25 km away from major oil sands upgrading facilities. In summary, particles characterized as coming from oil sands are more efficient at ice nucleation. We discuss the potential impacts of AOSR emissions on atmospheric and microphysical processes (ice nucleation and precipitation) both locally and regionally.

Sources of Methylmercury to Snowpacks of the Alberta Oil Sands Region: A Study of In Situ Methylation and Particulates.

Snowpacks in the Alberta Oil Sands Region (AOSR) of Canada contain elevated loadings of methylmercury (MeHg; a neurotoxin that biomagnifies through foodwebs) due to oil sands related activities. At sites ranging from 0 to 134 km from the major AOSR upgrading facilities, we examined sources of MeHg by quantifying potential rates of MeHg production in snowpacks and melted snow using mercury stable isotope tracer experiments, as well as quantifying concentrations of MeHg on particles in snowpacks (pMeHg). At four sites, methylation rate constants were low in snowpacks (km = 0.001-0.004 d-1) and nondetectable in melted snow, except at one site (km = 0.0007 d-1). The ratio of methylation to demethylation varied between 0.3 and 1.5, suggesting that the two processes are in balance and that in situ production is unlikely an important net source of MeHg to AOSR snowpacks. pMeHg concentrations increased linearly with distance from the upgraders (R2 = 0.71, p < 0.0001); however, snowpack total particle and pMeHg loadings decreased exponentially over this same distance (R2 = 0.49, p = 0.0002; R2 = 0.56, p < 0.0001). Thus, at near-field sites, total MeHg loadings in snowpacks were high due to high particle loadings, even though particles originating from industrial activities were not MeHg rich compared to those at remote sites. More research is required to identify the industrial sources of snowpack particles in the AOSR.

Role of snow and cold environment in the fate and effects of nanoparticles and select organic pollutants from gasoline engine exhaust.

Exposure to vehicle exhaust can drive up to 70 % of excess lifetime cancer incidences due to air pollution in urban environments. Little is known about how exhaust-derived particles and organic pollutants, implicated in adverse health effects, are affected by freezing ambient temperatures and the presence of snow. Airborne particles and (semi)volatile organic constituents in dilute exhaust were studied in a novel low-temperature environmental chamber system containing natural urban snow under controlled cold environmental conditions. The presence of snow altered the aerosol size distributions of dilute exhaust in the 10 nm to 10 µm range and decreased the number density of the nanoparticulate (<100 nm) fraction of exhaust aerosols, yet increased the 100-150 nm fraction. Upon 1 hour exhaust exposure, the total organic carbon increased in the natural snow from 0.218 ± 0.014 to 0.539 ± 0.009 mg L(-1), and over 40 additional (semi)volatile organic compounds and a large number of exhaust-derived carbonaceous and likely organic particles were identified. The concentrations of benzene, toluene, ethylbenzene, and xylenes (BTEX) increased from near the detection limit to 52.48, 379.5, 242.7, and 238.1 µg kg(-1) (± 10 %), respectively, indicating the absorption of exhaust-derived toxic organic compounds by snow. The alteration of exhaust aerosol size distributions at freezing temperatures and in the presence of snow, accompanied by changes of the organic pollutant content in snow, has potential to alter health effects of human exposure to vehicle exhaust.

Co-adsorption of gaseous benzene, toluene, ethylbenzene, m-xylene (BTEX) and SO2 on recyclable Fe3O4 nanoparticles at 0-101% relative humidities.

We herein used Fe3O4 nanoparticles (NPs) as an adsorption interface for the concurrent removal of gaseous benzene, toluene, ethylbenzene and m-xylene (BTEX) and sulfur dioxide (SO2), at different relative humidities (RH). X-ray diffraction, Brunauer-Emmett-Teller, and transmission electron microscopy were deployed for nanoparticle surface characterization. Mono-dispersed Fe3O4 (Fe2O3·FeO) NPs synthesized with oleic acid (OA) as surfactant, and uncoated poly-dispersed Fe3O4 NPs demonstrated comparable removal efficiencies. Adsorption experiments of BTEX on NPs were measured using gas chromatography equipped with flame ionization detection, which indicated high removal efficiencies (up to (95±2)%) under dry conditions. The humidity effect and competitive adsorption were investigated using toluene as a model compound. It was observed that the removal efficiencies decreased as a function of the increase in RH, yet, under our experimental conditions, we observed (40±4)% toluene removal at supersaturation for Fe3O4 NPs, and toluene removal of (83±4)% to (59±6)%, for OA-Fe3O4 NPs. In the presence of SO2, the toluene uptake was reduced under dry conditions to (89±2)% and (75±1)% for the uncoated and coated NPs, respectively, depicting competitive adsorption. At RH>100%, competitive adsorption reduced the removal efficiency to (27±1)% for uncoated NPs whereas OA-Fe3O4 NPs exhibited moderate efficiency loss of (55±2)% at supersaturation. Results point to heterogeneous water coverage on the NP surface. The magnetic property of magnetite facilitated the recovery of both types of NPs, without the loss in efficiency when recycled and reused.

Gas-phase HO-initiated reactions of elemental mercury: kinetics, product studies, and atmospheric implications.

Mercury is an environmentally volatile toxic fluid metal that is assumed to have a long atmospheric residence time and hence is subject to long-range transport. The speciation and chemical transformation of mercury in the atmosphere strongly influences its bioaccumulation potential in the human food chain as well as its global cycling. To investigate the oxidation of Hg0 by HO, the dominantdaytime atmospheric oxidant, we performed kinetic and product studies over the temperature range 283-353 K under near atmospheric pressure (100+/-0.13 kPa) in air and N2 diluents. Experiments were carried out by the relative rate method using five reference molecules and monitored by gas chromatography with mass spectroscopic detection (GC-MS). The HO were generated using UV photolysis of isopropyl nitrite at 300 < or = lambda < or = 400 nm in the presence of NO. The room-temperature rate constant was found to be (9.0+/-1.3) x 10(-14) cm3 molecule(-1) s(-1). The temperature dependence of the reaction can be expressed as a simple Arrhenius expression (in unit of 10(-14) cm3 molecule(-1) s(-1)) using ethane as the reference molecule: kHg + HO = 3.55 x 10(-14) exp((294+/-16)/T). The major reaction product, HgO, was identified in the gaseous form, as aerosols and as deposits on the container walls, using chemical ionization mass spectrometry (CI-MS), electron impact mass spectrometry (EI-MS), GC-MS, and cold vapor atomic fluorescence spectrometry (CVAFS). Experimental results reveal that ca. 6% of the reaction products were collected on a 0.2 microm filter as suspended aerosol, ca. 10% were in the gaseous form, and about 80% were deposited on the reaction vessel wall. The potential implications of our results in the understanding of tropospheric mercury transformation are herein discussed.

Product study of the gas-phase BrO-initiated oxidation of Hg0: evidence for stable Hg1+ compounds.

Mercury is a key toxic environmental pollutant, and its speciation affects its bioavailability. BrO radicals have been identified as key oxidants during mercury depletion events observed in Arctic and sub-Arctic regions. We report the first experimental product study of BrO-initiated oxidation of elemental mercury at atmospheric pressure of ca. 0.987 bar and T= 296+/-2 K. We used chemical ionization and electron impact mass spectrometry, gas chromatography coupled to a mass spectrometer, a MALDI-TOF mass spectrometer, a cold vapor atomic fluorescence spectrometer, and high-resolution transmission electron microscopy coupled to energy dispersive spectrometry. BrO radicals were formed using visible and UV photolysis of Br2 and CH2Br2 in the presence of ozone. We have analyzed the products in the gas phase, on suspended aerosols and on wall deposits, and identified HgBr, HgBrO/HgOBr, and HgO as reaction products. Mercury aerosols with a characteristic width of ca. 0.2 microm were observed as products. We herein discuss the implications of our results to the chemistry of atmospheric mercury and its potential implications in the biogeochemical cycling of mercury.