Correction to: Development of methodology to generate, measure and characterize the chemical composition of oxidized mercury nanoparticles.

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Development of methodology to generate, measure, and characterize the chemical composition of oxidized mercury nanoparticles.

The phase of oxidized mercury is critical in the fate, transformation, and bioavailability of mercury species in Earth's ecosystem. There is now evidence that what is measured as gaseous oxidized mercury (GOM) is not only gaseous but also consists of airborne nanoparticles with distinct physicochemical properties. Herein, we present the development of the first method for the consistent and reproducible generation of oxidized mercury nano- and sub-micron particles (~ 5 to 400 nm). Oxidized mercury nanoparticles are generated using two methods, vapor-phase condensation and aqueous nebulization, for three proxies: mercury(II) bromide (HgBr2), mercury(II) chloride (HgCl2), and mercury(II) oxide (HgO). These aerosols are characterized using scanning mobility and optical sizing, high-resolution scanning transmission electron microscopy (STEM), and nano/microparticle interface coupled to soft ionization mercury mass spectrometric techniques. Synthetic nanoparticle stability was studied in aqueous media, and using a microcosm at ambient tropospheric conditions of ~ 740 Torr pressure, room temperature, and at relative humidity of approximately 20%. Analysis of microcosm airborne nanoparticles confirmed that generated synthetic mercury nanoparticles retain their physical properties once in air. KCl-coated denuders, which are currently used globally to measure gaseous mercury compounds, were exposed to generated oxidized mercury nanoparticles. The degree of synthetic mercury nanoparticle capture by KCl-coated denuders and particulate filters was assessed. A significant portion of nanoparticulate and sub-micron particulate mercury was trapped on the KCl-coated denuder and measured as GOM. Finally, we demonstrate the applicability of soft ionization mercury mass spectrometry to the measurement of mercury species present in the gaseous and solid phase. We recommend coupling of this technique with existing methodology for a more accurate representation of mercury biogeochemistry cycling. Graphical Abstract.

The Existence of Airborne Mercury Nanoparticles.

Mercury is an important global toxic contaminant of concern that causes cognitive and neuromuscular damage in humans. It is ubiquitous in the environment and can travel in the air, in water, or adsorb to soils, snow, ice and sediment. Two significant factors that influence the fate of atmospheric mercury, its introduction to aquatic and terrestrial environments, and its bioaccumulation and biomagnification in biotic systems are the chemical species or forms that mercury exists as (elemental, oxidized or organic) and its physical phase (solid, liquid/aqueous, or gaseous). In this work, we show that previously unknown mercury-containing nanoparticles exist in the air using high-resolution scanning transmission electron microscopy imaging (HR-STEM). Deploying an urban-air field campaign near a mercury point source, we provide further evidence for mercury nanoparticles and determine the extent to which these particles contain two long suspected forms of oxidized mercury (mercuric bromide and mercuric chloride) using mercury mass spectrometry (Hg-MS). Using optical particle sizers, we also conclude that the conventional method of measuring gaseous oxidized mercury worldwide can trap up to 95% of nanoparticulate mercuric halides leading to erroneous measurements. Finally, we estimate airborne mercury aerosols may contribute to half of the oxidized mercury measured in wintertime Montréal urban air using Hg-MS. These emerging mercury-containing nanoparticle contaminants will influence mercury deposition, speciation and other atmospheric and aquatic biogeochemical mercury processes including the bioavailability of oxidized mercury to biota and its transformation to neurotoxic organic mercury.

Exposure to nanoscale and microscale particulate air pollution prior to mining development near a northern indigenous community in Québec, Canada.

This study serves as a baseline characterization of indoor and outdoor air quality in a remote northern indigenous community prior to the start of a major nearby mining operation, including measurements of nanoparticles, which has never been performed in this context before. We performed aerosol sample collection and real-time aerosol measurements at six different locations at the Cree First Nation of Waswanipi and the Montviel campsite, located 45 km west of the Cree First Nation of Waswanipi, in the south of the Nord-du-Québec region. High concentrations of airborne nanoparticles (up to 3.98 × 104 ± 8.9 × 103 cm-3 at 64.9-nm midpoint particle diameter) and fine particles (up to 1.99 × 103 ± 1.6 × 102 cm-3 at 0.3-µm midpoint particle diameter) were measured inside a residential home, where we did not find any ventilation or air filtration systems. The most abundant particle sizes by mass were between 0.19 and 0.55 µm. The maximum concentration of analyzed heavy metals was detected at the d50 cut-off particle size of 0.31 µm; and the most abundant heavy metals in the aerosol samples were Al, Ba, Zn, Cu, Hg, and Pb. We concluded that the sources of the relatively high indoor particle concentrations were likely laundry machines and cooking emissions in the absence of a sufficient ventilation system. However, the chemical composition of particles resulting from mining activities is expected to be different from that of the aerosol particles from indoor sources. Installation and proper maintenance of sufficient ventilation and air filtration systems may reduce the total burden of disease from outdoor and indoor air pollution and remediate infiltrated indoor particulate pollution from the mining sources as well.

The presence of the top prescribed pharmaceuticals in treated sewage effluents and receiving waters in Southwest Nova Scotia, Canada.

From a list of the top prescribed drugs in Canada, 11 pharmaceuticals and two metabolites were selected for study in municipal sewage treatment plant effluents and receiving waters. Wastewater samples were collected from 16 wastewater treatment plants across Southwest Nova Scotia including the Annapolis Valley, South Shore, and Metropolitan Halifax. Samples were also collected between 100 and 200 m downstream of effluent outflows. Seven pharmaceuticals were found above µg/L levels with their highest concentrations as follows: metformin (10.6 µg/L), acetaminophen (28.9 µg/L), paraxanthine (18.2 µg/L), cotinine (3.10 µg/L), caffeine (115 µg/L), naproxen (29.1 µg/L), and venlafaxine (2.65 µg/L). Metformin, paraxanthine, caffeine, naproxen, ramipril, and venlafaxine were detected in every wastewater effluent sample. Statistical analysis revealed significant differences in pharmaceutical occurrence by treatment methods, weak dependence of pharmaceutical concentrations on populations, and the co-occurrence of some pharmaceuticals. Experimental results might indicate the limitation of primary only treatment methods in breaking down pharmaceuticals.

Membrane bioreactor technology: a novel approach to the treatment of compost leachate.

Compost leachate forms during the composting process of organic material. It is rich in oxidizable organics, ammonia and metals, which pose a risk to the environment if released without proper treatment. An innovative method based on the membrane bioreactor (MBR) technology was developed to treat compost leachate over 39days. Water quality parameters, such as pH, dissolved oxygen, ammonia, nitrate, nitrite and chemical oxygen demand (COD) were measured daily. Concentrations of caffeine and metals were measured over the course of the experiment using gas chromatography - mass spectrometry (GC/MS) and inductively coupled plasma - mass spectrometry (ICP-MS) respectively. A decrease of more than 99% was achieved for a COD of 116g/L in the initial leachate. Ammonia was decreased from 2720mg/L to 0.046mg/L, while the nitrate concentration in the effluent rose to 710mg/L. The bacteria in the MBR system adjusted to the presence of the leachate, and increased 4 orders of magnitude. Heavy metals were removed by at least 82.7% except copper. These successful results demonstrated the membrane bioreactor technology is feasible, efficient method for the treatment of compost leachate.

Treatment of 2,4-D, mecoprop, and dicamba using membrane bioreactor technology.

Phenoxyacetic and benzoic acid herbicides are widely used agricultural, commercial, and domestic pesticides. As a result of high water solubility, mobility, and persistence, 2,4-dichlorophenoxyacetic acid (2,4-D), methylchlorophenoxypropionic acid (mecoprop), and 3,6-dichloro-2-methoxybenzoic acid (dicamba) have been detected in surface and waste waters across Canada. As current municipal wastewater treatment plants do not specifically address chronic, trace levels of contaminants like pesticides, an urgent need exists for an efficient, environmentally friendly means of breaking down these toxic herbicides. A commercially available herbicide mix, WeedEx, containing 2,4-D, mecoprop, and dicamba, was subjected to treatment using membrane bioreactor (MBR) technology. The three herbicides, in simulated wastewater with a chemical oxygen demand of 745 mg/L, were introduced to the MBR at concentrations ranging from 300 µg/L to 3.5 mg/L. Herbicides and biodegradation products were extracted from MBR effluent using solid-phase extraction followed by detection using high-performance liquid chromatography coupled with mass spectrometry. 2,4-D was reduced by more than 99.0 % within 12 days. Mecoprop and dicamba were more persistent and reduced by 69.0 and 75.4 %, respectively, after 112 days of treatment. Half-lives of 2,4-D, mecoprop and dicamba during the treatment were determined to be 1.9, 10.5, and 28.3 days, respectively. Important water quality parameters of the effluent such as dissolved oxygen, pH, ammonia, chemical oxygen demand, etc. were measured daily. MBR was demonstrated to be an environmentally friendly, compact, and efficient method for the treatment of toxic phenoxyacetic and benzoic acid herbicides.

Membrane bioreactor treatment of commonly used organophosphate pesticides.

Five pesticide formulations registered for use in Canada containing organophosphate-insecticide active ingredients azinphos-methyl, chlorpyrifos, diazinon, malathion and phorate were subjected to treatment by membrane bioreactor (MBR) technology. The target active ingredients were introduced to the MBR at ppm level concentrations. The biodegradation of these compounds was analyzed daily using selected ion monitoring gas chromatography-mass spectrometry (GC/MS-SIM) following extraction of the analytes using solid-phase extraction (SPE). Amounts measuring 83 % to 98 % of the target analytes were removed with steady-state concentrations being reached within 5 days of their introduction. The dissolved oxygen, temperature, pH, and total heterotrophic bacterial population were monitored daily to ensure optimal conditions for biodegradation. The quality of the effluent from the MBR was assessed daily through spectrophotometric methods. Measurements were conducted for the concentration of ammonia, nitrate, nitrite, total and reactive phosphorus, as well as the chemical oxygen demand (COD) of the effluent. This study demonstrated that the MBR technology is feasible and efficient for treatment of organophosphate pesticides without introducing additional chemical additives.

The presence of acidic and neutral drugs in treated sewage effluents and receiving waters in the Cornwallis and Annapolis River watersheds and the Mill CoveSewage Treatment Plant in Nova Scotia, Canada.

Pharmaceuticals are designed to have physiological effects on target organisms. Their presence and effect in aquatic ecosystems in the Annapolis Valley in Nova Scotia is relatively unknown. Over-the-counter (OTC) and prescription drugs are continually introduced to aquatic ecosystems through treated sewage effluent outflows into rivers and other bodies of water. Fouracidic and two neutral pharmaceuticals were monitored in the effluents from nine sewage treatment plants in the Annapolis Valley and Halifax Regional Municipality (HRM) in Nova Scotia. Naproxen and ibuprofen, two highly used OTC drugs, were the most prominent and were detected at high ng/L to low µg/L levels. Caffeine, salicylic acid (a metabolite of acetylsalicylic acid) and cotinine were detected in the ng/L range. Warfarin was not detected above the detection limits. The urban sewage treatment plant in Mill Cove, HRM showed much higher concentrations of pharmaceuticals than rural facilities in the Annapolis Valley, despite the fact that more advanced facilities are used at the urban plant. Receiving waters both downstream and upstream from STP effluent outfalls were also studied, and trace levels of caffeine at several sites indicate some degree of pollution propagation into surrounding aquatic ecosystems.