Correction to "Solvent-Free Nonthermal Destruction of PFAS Chemicals and PFAS in Sediment by Piezoelectric Ball Milling"

[This corrects the article DOI: 10.1021/acs.estlett.2c00902.].

Variations of oxidative potential of PM2.5 in a medium-sized residential city in South Korea measured using three different chemical assays

Although it is evident that PM2.5 has serious adverse health effects, there is no consensus on what the biologically effective dose is. In this study, the intrinsic oxidative potential (OPm) and the extrinsic oxidative potential (OPv) of PM2.5 were measured using three chemical assays including dithiothreitol (DTT), ascorbic acid (AA), and reduced glutathione (GSH), along with chemical compositions of PM2.5 in South Korea. Among the three chemical assays, only OPmAA showed a statistically significant correlation with PM2.5 while OPmGSH and OPmDTT were not correlated with PM2.5 mass concentration. When the samples were categorized by PM2.5 mass concentrations, the variations in the proportion of Ni, As, Mn, Cd, Pb, and Se to PM2.5 mass closely coincided with changes in OPm across all three assays, suggesting a potential association between these elements and PM2.5 OP. Multiple linear regression analysis identified the significant PM components affecting the variability in extrinsic OPv. OPvAA was determined to be significantly influenced by EC, K+, and Ba while OC and Al were common significant factors for OPvGSH and OPvDTT. It was also found that primary OC was an important variable for OPvDTT while secondary OC significantly affected the variability of OPvGSH.

Distribution and risk assessment of microplastic pollution in a rural river system near a wastewater treatment plant, hydro-dam, and river confluence

Rivers are the natural drainage system, transporting anthropogenic wastes and pollution, including microplastics (plastic < 5 mm). In a riverine system, microplastics can enter from different sources, and have spatial variance in concentration, physical and chemical properties, and imposed risk to the ecosystem. This pilot study presents an examination of microplastics in water and sediment samples using a single sample collection from the rural Raquette River, NY to evaluate a hypothesis that distinct locations of the river, such as downstream of a wastewater treatment plant, upstream of a hydro-dam, and river confluence, may be locations of higher microplastics concentration. In general, our results revealed the presence of high microplastic concentrations downstream of the wastewater treatment plant (in sediments), upstream of the hydro dam (both water and sediment), and in the river confluence (water sample), compared to other study sites. Moreover, the risk assessment indicates that even in a rural river with most of its drainage basin comprising forested and agricultural land, water, and sediment samples at all three locations are polluted with microplastics (pollution load index, PLI > 1; PLIzone = 1.87 and 1.68 for water and sediment samples respectively), with risk categories between Levels I and IV ("minor" to "danger"). Overall, the river stands in a "considerable" risk category (PRIzone = 134 and 113 for water and sediment samples respectively). The overall objective of this pilot study was to evaluate our hypothesis and advance our understanding of microplastic dynamics in rural river systems, elucidating their introduction from a point source (wastewater treatment plant), transit through an impediment (hydro-dam), and release into a vital transboundary river (confluence of Raquette-St. Lawrence Rivers).

PFAS-CTAB Complexation and Its Role on the Removal of PFAS from a Lab-Prepared Water and a Reverse Osmosis Reject Water Using a Plasma Reactor

Electrical discharge plasma reactors with argon bubbling can effectively treat long-chain perfluoroalkyl acids (PFAAs) in contaminated water, and the addition of a cationic surfactant cetrimonium bromide (CTAB) is known to enhance the removal of short-chain PFAAs. However, the roles of PFAA chain length, functional group, and water matrix properties on PFAA-CTAB complexation are largely unknown. This work investigated the bulk liquid removal of different PFAAs by CTAB in the absence of plasma. Stepwise addition of CTAB was subsequently used to efficiently treat PFAAs in a lab-prepared water and a reverse osmosis (RO) reject water using an enhanced contact plasma reactor. The results show that CTAB inhibited the bulk liquid removal of long-chain PFAAs in the absence of plasma likely due to the formation of hydrophilic CTAB-PFAA mixed micelles and competition for interfacial access between long-chain PFAAs and CTAB. On the contrary, CTAB enhanced the removal of short- and ultrashort-chain PFAAs by forming hydrophobic complexes. After 6 h of treatment in the plasma reactor with CTAB, PFAAs were 86 to >99% removed from the lab-prepared water and 29 to >99% removed from the RO reject water. This study provides important insights for overcoming mass transfer limitations for PFAA treatment technologies.

Can blood proteome diversity among fish species help explain perfluoroalkyl acid trophodynamics in aquatic food webs?

Per- and polyfluoroalkyl substances (PFAS) are a diverse family of industrially significant synthetic chemicals infamous for extreme environmental persistence and global environmental distribution. Many PFAS are bioaccumulative and biologically active mainly due to their tendency to bind with various proteins. These protein interactions are important in determining the accumulation potential and tissue distribution of individual PFAS. Trophodynamics studies including aquatic food webs present inconsistent evidence for PFAS biomagnification. This study strives to identify whether the observed variability in PFAS bioaccumulation potential among species could correspond with interspecies protein composition differences. Specifically, this work compares the perfluorooctane sulfonate (PFOS) serum protein binding potential and the tissue distribution of ten perfluoroalkyl acids (PFAAs) detected in alewife (Alosa pseudoharengus), deepwater sculpin (Myoxocephalus thompsonii), and lake trout (Salvelinus namaycush) of the Lake Ontario aquatic piscivorous food web. These three fish sera and fetal bovine reference serum all had unique total serum protein concentrations. Serum protein-PFOS binding experiments showed divergent patterns between fetal bovine serum and fish sera, suggesting potentially two different PFOS binding mechanisms. To identify interspecies differences in PFAS-binding serum proteins, fish sera were pre-equilibrated with PFOS, fractionated by serial molecular weight cut-off filter fractionation, followed by liquid chromatography-tandem mass spectrometry analysis of the tryptic protein digests and the PFOS extracts of each fraction. This workflow identified similar serum proteins for all fish species. However, serum albumin was only identified in lake trout, suggesting apolipoproteins are likely the primary PFAA transporters in alewife and deepwater sculpin sera. PFAA tissue distribution analysis provided supporting evidence for interspecies variations in lipid transport and storage, which may also contribute to the varied PFAA accumulation in these species. Proteomics data are available via ProteomeXchange with identifier PXD039145.

Solvent-Free Nonthermal Destruction of PFAS Chemicals and PFAS in Sediment by Piezoelectric Ball Milling

Studies on the destruction of solid per- and polyfluoroalkyl substances (PFAS) chemicals and PFAS-laden solid wastes significantly lag behind the urgent social demand. There is a great need to develop novel treatment processes that can destroy nonaqueous PFAS at ambient temperatures and pressures. In this study, we develop a piezoelectric-material-assisted ball milling (PZM-BM) process built on the principle that ball collisions during milling can activate PZMs to generate ∼kV potentials for PFAS destruction in the absence of solvents. Using boron nitride (BN), a typical PZM, as an example, we successfully demonstrate the complete destruction and near-quantitative (∼100%) defluorination of solid PFOS and perfluorooctanoic acid (PFOA) after a 2 h treatment. This process was also used to treat PFAS-contaminated sediment. Approximately 80% of 21 targeted PFAS were destroyed after 6 h of treatment. The reaction mechanisms were determined to be a combination of piezo-electrochemical oxidation of PFAS and fluorination of BN. The PZM-BM process demonstrates many potential advantages, as the degradation of diverse PFAS is independent of functional group and chain configurations and does not require caustic chemicals, heating, or pressurization. This pioneering study lays the groundwork for optimizing PZM-BM to treat various PFAS-laden solid wastes.

Bioaccumulation of perfluoroalkyl substances in the Lake Erie food web

The bioaccumulation and biomagnification of perfluoroalkyl substances (PFAS) in the Lake Erie food web was investigated by analyzing surface water and biological samples including 10 taxa of fish species, 2 taxa of benthos and zooplankton. The carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic composition and fatty acids profiles of biological samples were used to evaluate the food web structure and assess the biomagnification of PFAS. Perfluorooctane sulfonate (PFOS) dominated the total PFAS (ΣPFAS) concentration (50-90% of ΣPFAS concentration), followed by C9-C11 perfluorinated carboxylic acids (PFCAs). The highest PFOS concentrations (79 ± 4.8 ng/g, wet weight (wwt)) and ΣPFAS (88 ± 5.2 ng/g, wwt) were detected in yellow perch (Perca flavescens). The C8-C14 PFAS biomagnification factors (BMFs) between apex piscivorous fish and prey fish were found to be generally greater than 1, indicative of PFAS biomagnification, while biodilution (BMF<1) was observed between planktivorous fish and zooplankton. Trophic magnification factors (TMFs) of C8-C14 PFCA were not correlated with perfluoroalkyl chain length. The C4-C9 PFAS were detected in the surface water of Lake Erie, and PFBA was found to have the highest concentrations (2.1-2.8 ng/L) among all PFAS detected. The log of bioaccumulation factor (BAF) was found to generally increase with increasing log K_ow for C6, 8, and 9 PFAS in all selected species from three tropic levels.

Suspect Screening and Nontargeted Analysis of Per- and Polyfluoroalkyl Substances in a Lake Ontario Food Web

Per- and polyfluoroalkyl substances (PFAS) are globally distributed in the natural environment, and their persistent and bioaccumulative potential illicit public concern. The production of certain PFAS has been halted or controlled by regulation due to their adverse effect on the health of humans and wildlife. However, new PFAS are continuously developed as alternatives to legacy PFAS. Additionally, many precursors are unknown, and their metabolites have not been assessed. To better understand the PFAS profiles in the Lake Ontario (LO) aquatic food web, a quadrupole time-of-flight mass spectrometer (QToF) coupled to ultrahigh-performance liquid chromatography (UPLC) was used to generate high-resolution mass spectra (HRMS) from sample extracts. The HRMS data files were analyzed using an isotopic profile deconvoluted chromatogram (IPDC) algorithm to isolate PFAS profiles in aquatic organisms. Fourteen legacy PFAAs (C5-C14) and 15 known precursors were detected in the LO food web. In addition, over 400 unknown PFAS features that appear to biomagnify in the LO food web were found. Profundal benthic organisms, deepwater sculpin(Myoxocephalus thompsonii), and Mysis were found to have more known precursors than other species in the food web, suggesting that there is a large reservoir of fluorinated substances in the benthic zone.

Bioaccumulation of polyfluoroalkyl substances in the Lake Huron aquatic food web

Polyfluoroalkyl substances (PFAS) are a group of fluorinated organic chemicals that have been produced for industrial and commercial application since the 1950s. PFAS are highly persistent and ubiquitous in water, sediment, and biota. Toxic effects of PFAS on humans and the ecosystem have increased scientific and public concern. To better understand the distribution of PFAS in the Laurentian Great Lakes, carbon (¹²C and ¹³C) and nitrogen (¹⁴N and ¹⁵N) stable isotope enrichment, fatty acid profiles, and PFAS were measured in the Lake Huron (LH) aquatic food web. The trophic level of the organisms was estimated using δ¹⁵N and found to be a determinant of PFAS biomagnification. The δ¹³C and fatty acid profiles were used to assess the carbon/energy flow pathway and predator-prey relationships, respectively. The δ¹³C, δ¹⁵N, and fatty acids were used to elucidate the trophodynamics and understand the PFAS trophic transfer in the LH aquatic food web. Perfluorooctanesulfonic acid (PFOS) was the dominant PFAS observed, followed by C9 - C11 perfluorinated carboxylic acids (PFCA). The highest PFOS concentrations (45 ± 11 ng/g, wet weight (wwt)) were detected in lake trout (Salvelinus namaycush), while the highest total PFCA concentrations (sum of C4 - C16 PFCAs) were detected in deepwater sculpin (Myoxocephalus thompsonii). With the exception of perfluorooctanoic acid (PFOA), C8-C14 PFAS biomagnification factors (BMFs) were found to be generally greater than 1, suggesting PFAS biomagnification from prey to predator. Trophic magnification factors (TMFs) of C8-C14 PFCA were found to be independent of compound hydrophobicity.

Characterization of Halogenated Organic Compounds in Pelagic Sharks and Sea Turtles Using a Nontargeted Approach

Halogenated organic compounds (HOCs) in marine species collected from the Atlantic Ocean [3 shortfin mako (Isurus oxyrinchus) and 1 porbeagle (Lamna nasus)], and 12 sea turtles collected from the Pacific Ocean [3 loggerhead (Caretta caretta), 3 green (Chelonia mydas), 3 olive ridley (Lepidochelys olivacea), and 3 hawksbill (Eretmochelys imbricata)] were analyzed with a nontargeted analytical method using two-dimensional gas chromatography coupled to high-resolution time-of-flight mass spectrometry. Sharks and sea turtles had distinct HOC profiles. Halogenated methoxyphenols (halo-MeOPs) were the most abundant compound class identified in sea turtle livers, while polychlorinated biphenyls (PCBs) were the most abundant in shark livers. In addition to legacy contaminants and halo-MeOPs, a total of 110 nontargeted/novel HOCs (NHOCs) were observed in the shark livers. Shortfin mako collected from the northern Gulf of Mexico contained the largest number (89) and most diverse structural classes of NHOCs. Among all NHOCs, a group of compounds with the elemental composition C₁₄H_12-nCl_n (n = 5-8) exhibited the highest concentrations, followed by chlorocarbazoles and tris(chlorophenyl) methanes (TCPMs). Using nontargeted workflows, a variety of known and unknown HOCs were observed, which demonstrate the need to develop more complete chemical profiles in the marine environment.

Systematic Study on the Removal of Per- and Polyfluoroalkyl Substances from Contaminated Groundwater Using Metal-Organic Frameworks

Harmful per- and polyfluoroalkyl substances (PFAS) are ubiquitously detected in aquatic environments, but their remediation remains challenging. Metal-organic frameworks (MOFs) have been recently identified as an advanced material class for the efficient removal of PFAS, but little is known about the fundamentals of the PFAS@MOF adsorption process. To address this knowledge gap, we evaluated the performance of 3 different MOFs for the removal of 8 PFAS classes from aqueous film-forming foam-impacted groundwater samples obtained from 11 U.S. Air Force installations. Due to their different pore sizes/shapes and the identity of metal node, MOFs NU-1000, UiO-66, and ZIF-8 were selected to investigate the role of MOF structures, PFAS properties, and water matrix on the PFAS@MOF adsorption process. We observed that PFAS@MOF adsorption is (i) dominated by electrostatic and acid-base interactions for anionic and non-ionic PFAS, respectively, (ii) preferred for long- over short-chain PFAS, (iii) strongly dependent on the nature of PFAS head group functionality, and (iv) compromised in the presence of ionic and neutral co-contaminants by competing for ion-exchange sites and PFAS binding. With this study, we elucidate the PFAS@MOF adsorption mechanism from complex water sources to guide the design of more efficient MOFs for the treatment of PFAS-contaminated water bodies.

Proteomic analysis of the lake trout (Salvelinus namaycush) heart and blood: The beginning of a comprehensive lake trout protein database

Lake trout (Salvelinus namaycush) are a top-predator species in the Laurentian Great Lakes that are often used as bioindicators of chemical stressors in the ecosystem. Although many studies are done using these fish to determine concentrations of stressors like legacy persistent, bioaccumulative and toxic chemicals, there are currently no proteomic studies on the biological effects these stressors have on the ecosystem. This lack of proteomic studies on Great Lakes lake trout is because there is currently no complete, comprehensive protein database for this species. Here, we employed proteomics approaches to develop a lake trout protein database that could aid in future research on this fish, in particular exposomics and adductomics. The current study utilized heart tissue and blood from two lake trout. Our previous work using lake trout liver revealed 4194 potential protein hits in the NCBI databases and 3811 potential protein hits in the UniProtKB databases. In the current study, using the NCBI databases we identified 838 proteins for the heart and 580 proteins for the blood tissues in the biological replicate 1 (BR1) and 1180 potential protein hits for the heart and 561 potential protein hits for the blood in BR2. Similar results were obtained using the UniProtKB databases. This study builds on our previous work by continuing to build the first comprehensive lake trout protein database and provides insight into protein homology through evolutionary relationships. This data is available via the PRIDE partner repository with the dataset identifier PXD023970.

Trends (2005-2016) of perfluoroalkyl acids in top predator fish of the Laurentian Great Lakes

This work presents the first assessment of temporal trends (2005-2016) for perfluoroalkyl acids (PFAAs) in top predator fish of the Laurentian Great Lakes except Lake Ontario, for which we provide a post-2008 update. Lake trout (Salvelinus namaycush) or walleye (Sander vitreus; Lake Erie only) collected annually from 2005 to 2016 were analyzed for 12 perfluoroalkyl carboxylic acids (PFCAs) and 4 perfluoroalkyl sulfonic acids (PFSAs) with carbon chain lengths between 4 and 16 (C4-C16). Individual analyte concentrations generally decreased in fish basin-wide between 2005 and 2016, including Lake Ontario lake trout previously found to lack declining PFAA concentrations up until 2008. Declining fish PFAA burden reflects a positive response to the industrial phase-outs of these chemicals. Notable exceptions to this general decline included most analytes in lake trout collected from Lake Superior near Keweenaw Point and C6 and C8 PFSAs and C9 PFCAs in Lake Erie lake trout and walleye, which exhibited constant or increasing concentrations in recent years. Recent increases in Lake Superior shoreline development and mobilization from increased sediment resuspension and contamination from biosolids-amended agricultural soils in the Lake Erie watershed are plausible explanations for these cases. However, data scarcity prohibits confirmation of these suspected causes. The lingering lack of declining concentrations noted in this study together with the ongoing evolution of the fluorinated chemical industry emphasize the vigilance needed to better understand how past and future emissions will affect the Great Lakes and global ecosystems.

Treatment of PFAS-containing landfill leachate using an enhanced contact plasma reactor

A bench-scale plasma reactor was used to degrade poly- and perfluoroalkyl substances (PFAS) in landfill leachate samples obtained from three different locations. In the leachate samples before treatment, five long-chain, six short-chain perfluoroalkyl acids (PFAAs) and eight PFAA precursors were detected in a wide concentration range (~10² to 10⁵ ng/L; total oxidizable precursors (TOP) ~10⁶ ng/L). The concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 2000 and 3000 ng/L. Plasma-based water treatment of 500 mL samples resulted in faster removal rates for longer-chain than shorter chain length PFAAs. Both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations (<70 ng/L) in 10-75 min; 90% PFOA and PFOS removal was achieved in 10 min. Long-chain and short-chain PFAAs were removed by >99.9% and 10-99.9%, respectively. The removal rate constant (k_PFOA+PFOS) for combined PFOA and PFOS ranged between 0.20 and 0.34 min^-1. Overall, 60 ± 2% of the TOP concentration and 34 ± 2% of the TOC were removed. No effect of non-PFAS co-contaminants (e.g., total initial organic carbon concentration ~2000 mg/L) on the degradation efficiency was observed. Short-chain PFAA removal efficacy was enhanced by adding a cationic surfactant (cetrimonium bromide). Overall, the results indicate that plasma-based technology may be a viable technology for the treatment of PFAS-contaminated landfill leachates.

Nontargeted Discovery of Novel Contaminants in the Great Lakes Region: A Comparison of Fish Fillets and Fish Consumers

Sport fish fillets and human sera (fish consumers) were collected in the Lake Superior and Lake Michigan basin and screened for novel contaminants using the isotopic profile deconvoluted chromatogram (IPDC) algorithm. The IPDC algorithm was extended beyond traditional Cl/Br filters to detect additional potential bioaccumulative and toxic (PBT) such as perfluoroalkyl substances (PFAS). The IPDC algorithm screened for approximately 13.5 million theoretical molecular formulas. Additional algorithm modules were developed to detect data independent MS/MS fragmentation products and a retention time index calculator using a series of ¹³C-labeled perfluoroalkyl carboxylic acids (¹³C-PFCAs). Ten potential compound classes were isolated including six untargeted PFAS, six homologue groups of polyfluorinated carboxylic acids, polyfluorinated telomer alcohols (PoFTOHs), two hydroxylated polychlorobiphenyls, pesticides, herbicides, antifungals, pharmaceuticals, artificial sweeteners, and personal care products with minimal postprocessing efforts. The algorithm isolated 48 ubiquitous PoFTOHs in both fish fillet and serum of fish consumers suggesting a region wide distribution of this class of compounds. The 3, 4, and 7 fluorine substituted PoFTOH were the most abundant congeners in both biological matrices.

Nontargeted Screening of Halogenated Organic Compounds in Fish Fillet Tissues from the Great Lakes

Fish have been used for decades as bioindicators for assessing toxic contaminants in the Great Lakes ecosystem. Routine environmental monitoring programs target predetermined compounds that do not reflect the complete exposure of chemicals to biota and do not provide the complete halogenated fingerprint of the biota. In the current work, a nontargeted screening method was developed using a two-dimensional gas chromatograph coupled to a high-resolution time-of-flight mass spectrometer and was applied to 149 edible fish fillets from different species in the Great Lakes to characterize a more robust set of halogenated organic compounds across species and among lakes. Lake Ontario had the largest number of novel halogenated organic compounds (NHOCs). Seven NHOCs were observed in species from all lakes, indicating that this regional signature was not species-dependent. Hierarchical cluster analysis showed identical NHOC profiles between bottom dwelling and pelagic species. The NHOCs were grouped into seven clusters with similar structures and potentially similar environmental behaviors. Seven of the 29 NHOCs likely containing methoxy or ethoxy groups on a benzene or benzene-methanol backbone were clustered into one group with similar retention times. Five NHOCs were clustered with legacy contaminants that likely have similar structures or are their degradation products.

Decadal Differences in Emerging Halogenated Contaminant Profiles in Great Lakes Top Predator Fish

Legacy halogenated contaminants have been monitored in the Great Lakes for decades, but there are many additional unknown halogenated contaminants potentially affecting the Great Lakes ecosystem. To address this concern, lake trout (Salvelinus namaycush) were collected in 2005/2006 and 2015/2016 from each lake and screened for previously unidentified compounds. The isotopic profile deconvoluted chromatogram algorithm was used to isolate unknown halogenated components using high-resolution mass spectrometry data files generated by an atmospheric pressure gas chromatography-quadrupole time-of-flight mass spectrometer operated in positive and negative modes. The temporal and spatial differences in the newly detected features were used to isolate new potential contaminants. Decadal differences in the unknown halogenated compounds (or features) were compared with the total polychlorinated biphenyl concentration trends. Greater than 2000 unknown halogenated features were detected. As expected, Lake Superior contained the lowest number of unknown halogenated features, whereas Lake Ontario contained the highest. Unknown features tended to have fewer Cl and/or Br atoms compared to traditional legacy contaminant features typically monitored. Diverse patterns of unknown halogenated compounds between lakes suggested that there continues to be unidentified sources of halogenated contaminants in the Great Lakes missed by current monitoring programs.

Removal of Poly- and Per-Fluorinated Compounds from Ion Exchange Regenerant Still Bottom Samples in a Plasma Reactor

"High-concentration" and "low-concentration" bench-scale batch plasma reactors were used to effectively degrade per- and polyfluoroalkyl substances (PFAS) at a high concentration (∼100 mg/L) and a low concentration (<1 μg/L), respectively, in ion exchange (IX) regenerant still bottom (SB) solutions. In the SBs, numerous PFAS were detected with a wide concentration range (∼0.01 to 100 mg/L; total oxidizable precursors (TOP) ∼4000 to 10000 mg/L). In the "high-concentration" plasma reactor, the concentrations of PFAS precursors and long-chain perfluoroalkyl acids (PFAAs) (≥6C for PFSAs and ≥8C for perfluorocarboxylic acids (PFCAs)) were decreased by >99.9% in 2 h, and short-chain PFAAs (<6C for perfluorocarboxylic acids (PFSAs) and <8C PFCAs) were decreased by >99% in 6 h of treatment. Subsequently, a "low concentration" plasma reactor was used to remove additional PFAAs. In this reactor, the addition of CTAB (cetrimonium bromide, a cationic surfactant) caused short-chain PFAAs, other than PFBA, to be removed to below detection limits in 90 min of treatment time. Overall, >99% of the TOP present in SBs was removed during the treatment. Fluorine recovery of 47 to 117% was obtained in six SB samples. Energy requirement (EE/O) for the treatment of PFOA and PFOS from SBs ranged from 380 to 830 kWh/m³.

Concentrations and Long-Term Temporal Trends of Hexabromocyclododecanes (HBCDD) in Lake Trout and Walleye from the Great Lakes

Hexabromocyclododecane (HBCDD) is a hazardous, persistent, bioaccumlative brominated flame retardant. To investigate how its use has affected the Great Lakes, total HBCDD (∑HBCDD) concentrations and temporal trends in homogenized whole fish samples from the Great Lakes region (1978 to 2016) were determined. ∑HBCDD concentrations (ng/g ww) for each lake are Erie (0.49-2.60), Ontario (3.12-8.90), Michigan (3.91-9.01), Superior (5.69-13.1), and Huron (5.57-13.7). Early years (1978 to 1992) showed no significant trend. However, recent trends (2004 to 2016) suggest concentrations are increasing in Lakes Erie and Ontario, decreasing in Lakes Superior and Michigan, and not changing in Lake Huron. Decreasing trends for Lakes Superior and Michigan are likely the result of decreased usage of the compound globally, regionally, and locally. For the other lakes, increasing or zero trends are consistent with food web changes due to invasive species and climate change, which has caused more intense storms and less ice cover leading to increased sediment resuspension.

Automated Isotopic Profile Deconvolution for High Resolution Mass Spectrometric Data (APGC-QToF) from Biological Matrices

An isotopic profile matching algorithm, the isotopic profile deconvoluted chromatogram (IPDC), was developed to screen for a wide variety of organic compounds in high-resolution mass spectrometry (HRMS) data acquired from instruments with resolution power as low as 22 000 fwhm. The algorithm initiates the screening process by generating a series of C/Br/Cl/S isotopic patterns consistent with the profiles of approximately 3 million molecular formulas for compounds with potentially persistent, bioaccumulative, and toxic (PBT) properties. To evaluate this algorithm, HRMS data were screened using these seed profiles to isolate relevant chlorinated and/or brominated compounds. Data reduction techniques included mass defect filtering and retention time prediction from estimated boiling points predicted using molecular formulas and reasonable elemental conformations. A machine learning classifier was also developed using spectrometric and chromatographic variables to minimize false positives. A scoring system was developed to rank candidate molecular formulas for an isotopic feature. The IPDC algorithm was applied to a Lake Michigan lake trout extract analyzed by atmospheric pressure gas chromatography-quadrupole time-of-flight (APGC-QToF) mass spectrometry in positive and negative modes. The IPDC algorithm detected isotopic features associated with legacy contaminants and a series of unknown halogenated features. The IPDC algorithm resolved 313 and 855 halogenated features in positive and negative modes, respectively, in Lake Michigan lake trout.

Proteomic Analysis of the Lake Trout (Salvelinus namaycush) Liver Identifies Proteins from Evolutionarily Close and -Distant Fish Relatives

Lake trout are used as bioindicators for toxics exposure in the Great Lakes ecosystem. Here the first lake trout (Salvelinus namaycush) liver proteomics study is performed and searched against specific databases: (NCBI and UniProtKB) Salvelinus, Salmonidae, Actinopterygii, and Oncorhynchus mykiss, and the more distant relative, Danio rerio. In the biological replicate 1 (BR1), technical replicate 1 (TR1), (BR1TR1), a large number of lake trout liver proteins are not in the Salvelinus protein database, suggesting that lake trout liver proteins have homology to some proteins from the Salmonidae family and Actinopterygii class, and to Oncorhynchus mykiss and Danio rerio, two more highly studied fish. In the NCBI search, 4194 proteins are identified: 3069 proteins in Actinopterygii, 1617 in Salmonidae, 68 in Salvelinus, 568 in Oncorhynchus mykiss, and 946 in Danio rerio protein databases. Similar results are observed in the UniProtKB searches of BR1RT1, as well as in a technical replicate (BR1TR2), and then in a second biological replicate experiment, with two technical replicates (BR2TR1 and BR2TR2). This study opens the possibility of identifying evolutionary relationships (i.e., adaptive mutations) between various groups (i.e., zebrafish, rainbow trout, Salmonidae, Salvelinus and lake trout) through evolutionary proteomics. Data are available via the PRIDE Q2 (PXD011924).

Rapid Removal of Poly- and Perfluorinated Compounds from Investigation-Derived Waste (IDW) in a Pilot-Scale Plasma Reactor

A pilot-scale plasma reactor installed into an 8 × 20 ft² mobile trailer was used to rapidly and effectively degrade poly- and perfluoroalkyl substances (PFAS) from liquid investigation-derived waste (IDW; development and purge water from monitoring wells) obtained from 13 different site investigations at Air Force installations. In the raw water, numerous PFAS were detected in a wide concentration range (∼10-10⁵ ng/L; total oxidizable precursors (TOP) ∼10²-10⁵ ng/L, total fluorine by combustion ion chromatography ∼10² to 5 × 10⁶ ng F/L). The concentration of total PFAS (12 perfluorocarboxylic acids (PFCAs) and perfluoroalkyl sulfonates (PFSAs)) in the 13 samples ranged between 2.7 and 1440 μg/L and the concentration of perfluorooctane sulfonate (PFOS) plus perfluorooctanoic acid (PFOA) ranged between 365 and 73700 ng/L. Plasma-based water treatment resulted in rapid perfluoroalkyl acids (PFAAs) removal from 4 L individual IDW samples with faster rates for longer-chain PFCAs (C ≥ 8) and PFSAs (C ≥ 6) than for PFCAs and PFSAs of shorter chain length. In 9 of the 13 IDW samples, both PFOS and PFOA were removed to below United States Environmental Protection Agency's (USEPA's) health advisory concentration level (HAL) concentrations in <1 min, whereas longer treatment times (up to 50 min) were required for the remaining four IDW samples due to either extremely high solution electrical conductivity, which decreased the plasma-liquid contact area (one IDW sample) or high concentrations of PFAAs and their precursors; the latter was found to be converted to PFAAs during the treatment. Overall, 36-99% of the TOP concentration present in the IDWs was removed during the treatment. There was no effect of non-PFAS co-contaminants on the degradation efficiency. Overall, the results indicate that plasma-based water treatment is a viable technology for the treatment of PFAS-contaminated IDW.

Legacy Polybrominated Diphenyl Ethers (PBDEs) Trends in Top Predator Fish of the Laurentian Great Lakes (GL) from 1979 to 2016: Will Concentrations Continue to Decrease?

Polybrominated diphenyl ethers (PBDEs) were widely used as fire retardants and have been detected throughout the Great Lakes (GL) ecosystem. The concentration trends (after fish age normalization) of PBDEs in top predator fish (lake trout and walleye) of the GLs were determined from 1979 to 2016, which includes most of the period when PBDEs were manufactured and used in this region. The fish samples were collected by two national (U.S. and Canada) long-term monitoring and surveillance programs. Trends in total concentrations (age-normalized) of the five major PBDE congeners (BDE-47, 99, 100, 153, and 154) found in fish across all five lakes have varied over time. Significant increases were observed from 1990 to 2000 (16.3% per year). Rapidly decreasing concentrations (-19.5% per year) were found from 2000 to 2007. Since 2007, the decreasing trend has become smaller (less than -5.5% per year) and relatively unchanged from 2011 to 2015. BDE-47, the congener with the highest concentrations in lake trout, has decreased continuously (ranging from -6.7% to -16.2% per year) in all lakes except Lake Erie. This decrease can be associated with the voluntary and regulatory phase out of production and/or usage of PBDEs since 2000. However, it has been offset by recent (since 2007) increasing trends of the other four higher brominated BDE congeners, especially BDE-100 and 154. Production and usage of commercial penta- and octa- BDE mixtures containing primarily the five major PBDE congeners was discontinued in 2004 in the U.S.A. and 2008 in Canada. These results indicate increasing fish uptake and bioaccumulation of higher brominated BDE congeners may be related to the transformation of BDE-209 to lower brominated BDE compounds in the GL environment or food web. Considering the abundance of BDE-209 in existing products and sediment in GL region, the duration of the unchanging total PBDE concentration trend in GL fish could be longer than expected.

Breakdown Products from Perfluorinated Alkyl Substances (PFAS) Degradation in a Plasma-Based Water Treatment Process

Byproducts produced when treating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in water using a plasma treatment process intentionally operated to treat these compounds slowly to allow for byproduct accumulation were quantified. Several linear chain perfluoroalkyl carboxylic acids (PFCAs) (C4 to C7) were identified as byproducts of both PFOA and PFOS treatment. PFOA, perfluorohexanesulfonate (PFHxS), and perfluorobutanesulfonate (PFBS) were also found to be byproducts from PFOS degradation. Significant concentrations of fluoride ions, inorganic carbon, and smaller organic acids (trifluoroacetic acid, acetic acid, and formic acid) were also identified. In addition to PFCAs, PFHxS, and PFBS, trace amounts of 43 PFOA-related and 35 PFOS-related byproducts were also identified using a screening and search-based algorithm. Minor concentrations of gas-phase byproducts were also identified (<2.5% of the F originally associated with the parent molecules) some of which are reported for the first time in perfluoroalkyl substance degradation experiments including cyclic perfluoroalkanes (C₄F₈, C₅F₁₀, C₆F₁₂, C₇F₁₄, and C₈F₁₆). The short chain PFCAs detected suggest the occurrence of a stepwise reduction of the parent perfluoroalkyl substances (PFAS) molecule, followed by oxidation of intermediates, perfluoroalkyl radicals, and perfluoro alcohols/ketones. Using a fluorine mass balance, 77% of the fluorine associated with the parent PFOA and 58% of the fluorine associated with the parent PFOS were identified. The bulk of the remaining fluorine was determined to be sorbed to reactor walls and tubing using sorption experiments in which plasma was not generated.

Spatial and Temporal Trends (2004-2016) of Selected Alternative Flame Retardants in Fish of the Laurentian Great Lakes

Following the phase-out of polybrominated diphenyl ether (PBDE) and hexabromocyclododecane (HBCDD) flame retardants (FRs) from North American markets, the use of alternative FRs has increased. In this study the occurrence and spatiotemporal distributions of 18 dechlorane analogues (collectively referred to as DECs) and 20 alternative brominated FRs (referred to as ABFRs, i.e., brominated FRs other than PBDEs and HBCDD) were investigated in top predator fish megacomposites (i.e., a composite of all 50 fish) collected yearly from each of the Great Lakes from 2004 to 2016. Frequently detected substances include dechlorane 602, 603, 604 Component B, anti- and syn-dechlorane plus, and chlordene plus, as well as several brominated benzene FRs (i.e., hexabromobenzene, pentabromotoluene, and tetrabromo- o-chlorotoluene). Concentrations of ΣDECs and ΣABFRs ranged from 0.33-31.9 ng/g lipid weight (lw) (0.01-8.3 ng/g wet weight or ww) and 0.91-54.7 ng/g lw (0.09-7.1 ng/g ww), respectively. Flame retardant contamination exhibited chemical-specific spatial variations across the five lakes. Concentrations of ΣABFRs in Lake Erie fish were generally lower than those from other lakes. By contrast, fish ΣDEC concentrations were highest in Lake Ontario and the composition of dechlorane analogues differed significantly between Lake Ontario and the other lakes, indicating likely point-source influences. Temporal analyses revealed declining trends of ΣDECs and ΣABFRs in most lakes except Lake Erie, with age corrected trend slopes of -13.5% to -8.8% and -20.1% to -7.0% per year, respectively.

Ambient mercury source identification at a New York State urban site: Rochester, NY

Gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) were measured continuously in Rochester, NY (NY43) from January 2012 to December 2014. Continuous measurements of ozone (O₃), sulfur dioxide (SO₂), carbon monoxide (CO), nitrogen oxide (NO), nitrogen dioxide (NO₂), particulate matter (PM_2.5), and meteorological data were also made at this site. A principal component analysis (PCA) of the resulting 15 variables showed that the ambient mercury in Rochester was primarily produced by non-local sources in contrast to earlier studies that showed that local sources were present. Positive matrix factorization (PMF) analysis of the atmospheric mercury and other pollutant species concentrations showed that transport and atmospheric processes have become the major source of mercury in Rochester. Conditional bivariate probability function (CBPF) and potential source contribution function (PSCF) were used to identify local and distant mercury sources. The results in this study showed that the closure of a coal-fired power plant and promulgation of several fuel quality policies reduced local mercury emissions making long-distance transport the major source of mercury in Rochester.

Temporal trends of PCBs and DDTs in Great Lakes fish compared to those in air

Regulations designed to lower the concentrations of PCBs and DDTs in the environment have been in place since the 1970s, but the levels of PCBs are still high enough to cause fish consumption advisories for Great Lakes fish. The levels of PCBs and DDTs have been tracked in these fish since about 1975, and the rates at which these age-adjusted concentrations have been decreasing over the period 1999-2014 have been recently been estimated. This paper compares these rates to ones estimated from the entire data set (~1975-2014) and to rates estimated from changes in atmospheric concentrations, which have been tracked since 1992. In general the halving times (9-17 years for PCBs and 7-10 years for DDTs) estimated from the full fish dataset are similar to those estimated from the atmospheric data, suggesting that the atmospheric and the fish levels are coupled. The more recent, age-adjusted rates are sometimes significantly faster than those from the full fish and atmospheric datasets, suggesting that the air-water dynamic may now be changing.

Mercury wet deposition and speciated mercury air concentrations at rural and urban sites across New York state: Temporal patterns, sources and scavenging coefficients

Measurements of ambient speciated mercury (Hg) concentrations and Hg wet deposition were made at two urban sites (Bronx, NY and Rochester, NY) and one rural site (Potsdam, NY) in New York State in 2013 and 2014 to: 1) determine the factors influencing Hg wet deposition concentrations, 2) identify the contribution of gaseous oxidized Hg (GOM) and particulate bound Hg (PBM) scavenging to Hg wet deposition concentrations, and 3) identify potential source areas associated with high concentration events. The Bronx had the highest mean gaseous elemental Hg (GEM) and GOM concentrations, Rochester had the highest mean PBM and the lowest GOM concentrations, and Potsdam had the lowest mean GEM and PBM concentrations. The annual volume weighted mean (VWM) Hg concentrations and Hg wet deposition fluxes in the Bronx, Rochester, and Potsdam were significantly different with mean values of 10.3 ± 8.16, 10.2 ± 9.06, and 5.07 ± 1.79 ngL^-1 and 8.45 ± 0.64, 6.65 ± 0.21, and 5.25 ± 0.49 μg/m² year^-1, respectively. Hg wet deposition flux and precipitation depth were positively correlated at all three sites as were Hg concentration in precipitation and weekly GOM concentrations at the Bronx and Potsdam sites. Scavenging coefficients (SC) of 680, 630, 850 for GOM and 410, 320, and 410 for PBM at Bronx, Rochester, and Potsdam, respectively, suggest GOM is responsible for most of the scavenged Hg. Measured GOM and PBM concentrations were relatively constant before precipitation events and Hg concentrations in precipitation did not vary significantly during precipitation events implying the scavenging process mainly occurred in clouds. VWM Hg concentrations, monthly accumulated Hg flux, and SCs for GOM and PBM were higher at the urban sites and significantly different for non-snow and snow events. Local sources appeared more important at the rural site while regional sources affected high urban concentrations.

Polychlorinated biphenyls and organochlorine pesticides concentration patterns and trends in top predator fish of Laurentian Great Lakes from 1999 to 2014

Concentration patterns and temporal trends of legacy persistent, bioaccumulative and toxic (PBT) contaminants were determined using the Great Lake Fish Monitoring and Surveillance Program (GLFMSP) top predator fish data from 1999 to 2014 and applying Kendall-Theil robust regression after cluster-based age normalization. For most Great Lakes sites, significant decreasing concentration trends ranging from -4.1% to -21.6% per year (with the only exception being mirex in Lake Erie walleye) were found for PBTs including polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichlorethane (DDTs), dieldrin, endrin, chlordane, oxychlordane, nonachlor, mirex, and hexachlorobenzene (HCB) reflecting the successful historical and ongoing reduction of fugitive releases and remediation efforts in the U.S. and Canada including physical removal (dredging) coupled with sediment sequestration. Generally, lower concentrations and faster decreasing trends are observed in western/northern sampling sites compared to eastern/southern sites as the former sites are generally more remote from population centers and industrial activities. PCBs, which can be released from ongoing sources, have the highest concentration, the second slowest decreasing trend, and increasing mass fractions of the contaminants studied suggesting that they will continue to be the legacy contaminant of greatest concern into the future.

CYP1A1 gene polymorphisms modify the association between PM10 exposure and lung function

Genetic epidemiological studies have provided evidence that several genes modify the link between air pollution and lung function. We assessed whether the adverse impacts of particulate matter with an aerodynamic diameter ≤10 μm (PM₁₀) on lung function are modified by CYP1A1 gene polymorphisms in Korean adults. We used health check-up data from 1817 men, and the annual mean concentrations of ambient PM₁₀ estimated from the ambient data. Three single nucleotide polymorphisms (SNPs) of CYP1A1 were selected for our study. We identified significant CYP1A1 SNPs-by-PM₁₀ interactions for forced expiratory volume 1 s (FEV₁) and forced vital capacity (FVC) (all p_int < 0.05). Minor allele carriers of the SNPs were more susceptible to PM₁₀-induced FEV₁ and FVC reduction. The subgroup analysis of SNP genotypes showed that no significant association between PM₁₀ and FEV₁ or FVC was observed in homozygous reference genotype groups of all SNPs (all p_assoc > 0.05), whereas in heterozygous or homozygous alternate genotype groups, PM₁₀ was significantly associated with decreased FEV₁ (all p_assoc for FEV₁ < 0.05). The association between persistent exposure to PM₁₀ and lung function decline in Korean men may be determined in part by several functional variants of the CYP1A1 gene.

Bioaccumulation and Spatiotemporal Trends of Polyhalogenated Carbazoles in Great Lakes Fish from 2004 to 2016

Polyhalogenated carbazoles (PHCZs) were recently discovered in Great Lakes sediment and other aquatic systems. However, knowledge about their bioaccumulation and potential risks to fish and wildlife remains very limited. The present study investigated PHCZs in Great Lakes lake trout ( Salvelinus namaycush) and walleye ( Sander vitreus; Lake Erie only) composites collected between 2004 and 2016. Median concentrations of ∑PHCZs by lake ranged from 54.7 to 154 ng/g lipid weight or lw (6.8-28.0 ng/g wet weight). Dominant congeners included 3,6-dichlorocarbazole, 1,3,6-tribromocarbazole, and 1,3,6,8-tetrachlorocarbazole. The highest ∑PHCZs concentrations were found in Lakes Michigan and Ontario fish, followed by Lake Huron, whereas Lakes Erie and Superior fish contained the lowest concentrations. Congener profiles of PHCZs also exhibited spatial variations. After age normalization to minimize fish age influence on bioaccumulation rates, fish ∑PHCZs' concentrations declined significantly over time in all lakes except Lake Erie, with slopes ranging from -10.24% to -3.85% per year. The median toxic equivalent (TEQ) of PHCZs due to their dioxin-like activity was determined to range from 8.7 to 25.7 pg/g lw in Great Lakes fish. This study provides the first insight into the bioaccumulation and spatiotemporal trends of PHCZs in Great Lakes and suggests the need for further research on this group of chemicals.

Factors Affecting Mercury Stable Isotopic Distribution in Piscivorous Fish of the Laurentian Great Lakes

Identifying the sources of methylmercury (MeHg) and tracing the transformations of mercury (Hg) in the aquatic food web are important components of effective strategies for managing current and legacy Hg sources. In our previous work, we measured stable isotopes of Hg (δ²⁰²Hg, Δ¹⁹⁹Hg, and Δ²⁰⁰Hg) in the Laurentian Great Lakes and estimated source contributions of Hg to bottom sediment. Here, we identify isotopically distinct Hg signatures for Great Lakes trout ( Salvelinus namaycush) and walleye ( Sander vitreus), driven by both food-web and water-quality characteristics. Fish contain high values for odd-isotope mass independent fractionation (MIF) with averages ranging from 2.50 (western Lake Erie) to 6.18‰ (Lake Superior) in Δ¹⁹⁹Hg. The large range in odd-MIF reflects variability in the depth of the euphotic zone, where Hg is most likely incorporated into the food web. Even-isotope MIF (Δ²⁰⁰Hg), a potential tracer for Hg from precipitation, appears both disconnected from lake sedimentary sources and comparable in fish among the five lakes. We suggest that similar to the open ocean, water-column methylation also occurs in the Great Lakes, possibly transforming recently deposited atmospheric Hg deposition. We conclude that the degree of photochemical processing of Hg is controlled by phytoplankton uptake rather than by dissolved organic carbon quantity among lakes.

Comprehensive Analysis of the Great Lakes Top Predator Fish for Novel Halogenated Organic Contaminants by GC×GC-HR-ToF Mass Spectrometry

The U.S. Environmental Protection Agency's Great Lakes Fish Monitoring and Surveillance Program (GLFMSP) has traced the fate and transport of anthropogenic chemicals in the Great Lakes region for decades. Isolating and identifying halogenated species in fish is a major challenge due to the complexity of the biological matrix. A nontargeted screening methodology was developed and applied to lake trout using a 2-dimensional gas chromatograph coupled to a high resolution time-of-flight mass spectrometer (GC×GC-HR-ToF MS). Halogenated chemicals were identified using a combination of authentic standards and library spectral matching, with molecular formula estimations provided by exact mass spectral interpretation. In addition to the halogenated chemicals currently being targeted by the GLFMSP, more than 60 nontargeted halogenated species were identified. Most appear to be metabolites or breakdown products of larger halogenated organics. The most abundant compound class was halomethoxyphenols accounting for more than 60% of the total concentration of halogenated compounds in top predator fish from all five Great Lakes illustrating the need and utility of nontargeted halogenated screening of aquatic systems using this platform.

Estimation of CO2 emissions from waste incinerators: Comparison of three methods

Climate-relevant CO₂ emissions from waste incineration were compared using three methods: making use of CO₂ concentration data, converting O₂ concentration and waste characteristic data, and using a mass balance method following Intergovernmental Panel on Climate Change (IPCC) guidelines. For the first two methods, CO₂ and O₂ concentrations were measured continuously from 24 to 86 days. The O₂ conversion method in comparison to the direct CO₂ measurement method had a 4.8% mean difference in daily CO₂ emissions for four incinerators where analyzed waste composition data were available. However, the IPCC method had a higher difference of 13% relative to the direct CO₂ measurement method. For three incinerators using designed values for waste composition, the O₂ conversion and IPCC methods in comparison to the direct CO₂ measurement method had mean differences of 7.5% and 89%, respectively. Therefore, the use of O₂ concentration data measured for monitoring air pollutant emissions is an effective method for estimating CO₂ emissions resulting from waste incineration.

Age-Corrected Trends and Toxic Equivalence of PCDD/F and CP-PCBs in Lake Trout and Walleye from the Great Lakes: 2004-2014

Our research reports polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CP-PCBs) concentrations and age-corrected trends for lake trout and walleye in the Great Lakes over the 2004-2014 period. We determined that age-contaminant corrections are required to accurately report contaminant trends due to significant lake trout age structure changes. The age-trend model (ATM) described here uses a lake-specific age-contaminant regression to mitigate the effect of a fluctuating lake trout age structure to directly improve the log-linear regression model. ATM results indicate that half-life (t_1/2) and percent decreases for PCDD/Fs, CP-PCBs, and toxic equivalence (TEQ) (average -56 to 70%) were fairly uniform and consistent across the Great Lakes over the 2004-2014 period. The vast majority of TEQ associated with all Great Lakes lake trout and walleye samples is due to the nonortho CP-PCBs (average = 79%) as compared with PCDD/Fs (average = 21%). On average, CP-PCB_126 individually accounted for over 95% of the total CP-PCB TEQ. A retrospective analysis (1977-2014) of 2378-TCDF and 2378-TCDD raw concentrations in Lake Ontario lake trout revealed decreases of 94% and 96%, respectively. Tissue residue guidelines for wildlife protection based on lake trout and walleye total TEQ were uniformly exceeded in all the Great Lakes.

Mercury Temporal Trends in Top Predator Fish of the Laurentian Great Lakes from 2004 to 2015: Are Concentrations Still Decreasing?

Mercury (Hg) concentration trends in top predator fish (lake trout and walleye) of the Great Lakes (GL) from 2004 to 2015 were determined by Kendall-Theil robust regression with a cluster-based age normalization method to control for the effect of changes in lake trophic status. When data from the GLs (except Lake Erie) are combined, a significant decreasing trend in the lake trout Hg concentrations was found between 2004 and 2015 with an annual decrease of 4.1% per year, consistent with the decline in regional atmospheric Hg emissions and water Hg concentrations. However, a breakpoint was detected with a significant decreasing slope (-8.1% per year) before the breakpoint (2010), and no trend after the breakpoint. When the lakes are examined individually, Lakes Superior and Huron, which are dominated by atmospheric Hg inputs and are more likely than the lower lakes to respond to declining emissions from areas surrounding the GL, have significant decreasing trends with rates between 5.2 and 7.8% per year from 2004 to 2015. These declining trends appear to be driven by decreasing regional atmospheric Hg emissions although they may be partly counterbalanced by other factors, including increasing local emissions, food web changes, eutrophication, and responses to global climate change. Lakes Michigan, Erie and Ontario may have been more impacted by these other factors and their trends changed from decreasing to non-decreasing or increasing in recent years.

Plasma-Based Water Treatment: Efficient Transformation of Perfluoroalkyl Substances in Prepared Solutions and Contaminated Groundwater

A process based on electrical discharge plasma was tested for the transformation of perfluorooctanoic acid (PFOA). The plasma-based process was adapted for two cases, high removal rate and high removal efficiency. During a 30 min treatment, the PFOA concentration in 1.4 L of aqueous solutions was reduced by 90% with the high rate process (76.5 W input power) and 25% with the high efficiency process (4.1 W input power). Both achieved remarkably high PFOA removal and defluorination efficiencies compared to leading alternative technologies. The high efficiency process was also used to treat groundwater containing PFOA and several cocontaminants including perfluorooctanesulfonate (PFOS), demonstrating that the process was not significantly affected by cocontaminants and that the process was capable of rapidly degrading PFOS. Preliminary investigation into the byproducts showed that only about 10% of PFOA and PFOS is converted into shorter-chain perfluoroalkyl acids (PFAAs). Investigation into the types of reactive species involved in primary reactions with PFOA showed that hydroxyl and superoxide radicals, which are typically the primary plasma-derived reactive species, play no significant role. Instead, scavenger experiments indicated that aqueous electrons account for a sizable fraction of the transformation, with free electrons and/or argon ions proposed to account for the remainder.

The Estimated Six-Year Mercury Dry Deposition Across North America

Dry deposition of atmospheric mercury (Hg) to various land covers surrounding 24 sites in North America was estimated for the years 2009 to 2014. Depending on location, multiyear mean annual Hg dry deposition was estimated to range from 5.1 to 23.8 μg m^-2 yr^-1 to forested canopies, 2.6 to 20.8 μg m^-2 yr^-1 to nonforest vegetated canopies, 2.4 to 11.2 μg m^-2 yr^-1 to urban and built up land covers, and 1.0 to 3.2 μg m^-2 yr^-1 to water surfaces. In the rural or remote environment in North America, annual Hg dry deposition to vegetated surfaces is dominated by leaf uptake of gaseous elemental mercury (GEM), contrary to what was commonly assumed in earlier studies which frequently omitted GEM dry deposition as an important process. Dry deposition exceeded wet deposition by a large margin in all of the seasons except in the summer at the majority of the sites. GEM dry deposition over vegetated surfaces will not decrease at the same pace, and sometimes may even increase with decreasing anthropogenic emissions, suggesting that Hg emission reductions should be a long-term policy sustained by global cooperation.

Comprehensive Emerging Chemical Discovery: Novel Polyfluorinated Compounds in Lake Michigan Trout

A versatile screening algorithm capable of efficiently searching liquid chromatographic/mass spectrometric data for unknown compounds has been developed using a combination of open source and generic computing software packages. The script was used to search for select novel polyfluorinated contaminants in Great Lakes fish. However, the framework is applicable whenever full-scan, high-resolution mass spectral and chromatographic data are collected. Target compound classes are defined and a matrix of candidates is generated that includes mass spectral profiles and likely fragmentation pathways. The initial calibration was performed using a standard solution of known linear perfluoroalkyl acids. Once validated, Lake Michigan trout data files were analyzed for polyfluoroalkyl acids using the algorithm referencing 3570 possible compounds including C4-C10 perfluoro- and polyfluoroalkyl, polyfluorochloroalkyl acids and sulfonates, and potential ether forms. The results suggest the presence of 30 polyfluorinated chemical formulas which have not been previously reported in the literature. The identified candidates included mono- to hexafluoroalkyl carboxylic acids, mono- and trifluoroalkyl carboxylic acid ethers, and novel polyfluoroalkyl sulfonates. Candidate species identified in lake trout were qualified using theoretical isotopic profile matching, characteristic fragmentation patterns based on known linear perfluoroalkyl acid (PFAA) fragmentation, and retention time reproducibility among replicate extractions and injections. In addition, the relative retention times of multiple species within a compound class were compared based on theoretical octanol-water partition coefficients.

Computational fluid dynamics (CFD) simulation of a newly designed passive particle sampler

In this work a series of computational fluid dynamics (CFD) simulations were performed to predict the deposition of particles on a newly designed passive dry deposition (Pas-DD) sampler. The sampler uses a parallel plate design and a conventional polyurethane foam (PUF) disk as the deposition surface. The deposition of particles with sizes between 0.5 and 10 μm was investigated for two different geometries of the Pas-DD sampler for different wind speeds and various angles of attack. To evaluate the mean flow field, the k-ɛ turbulence model was used and turbulent fluctuating velocities were generated using the discrete random walk (DRW) model. The CFD software ANSYS-FLUENT was used for performing the numerical simulations. It was found that the deposition velocity increased with particle size or wind speed. The modeled deposition velocities were in general agreement with the experimental measurements and they increased when flow entered the sampler with a non-zero angle of attack. The particle-size dependent deposition velocity was also dependent on the geometry of the leading edge of the sampler; deposition velocities were more dependent on particle size and wind speeds for the sampler without the bend in the leading edge of the deposition plate, compared to a flat plate design. Foam roughness was also found to have a small impact on particle deposition.

Experimental and density functional theoretical study of the effects of Fenton's reaction on the degradation of Bisphenol A in a high voltage plasma reactor

A novel electrical discharge plasma reactor configuration with and without iron ions was evaluated for the degradation of 0.02 mM Bisphenol A (BPA). The pseudo-first-order reaction rate constant calculated for the plasma treatment of BPA with a stainless steel electrode in the presence of dissolved ferrous ion (Fe(2+)) salts (termed plasma/Fenton treatment) was higher than in the plasma treatment in the absence of iron salts. At the optimal ferrous ion concentration, longer plasma treatment times resulted in higher BPA degradation rates, likely due to increased hydroxyl (OH) radical concentration formed through the decomposition of H2O2. Replacing the stainless steel with a carbon steel grounded electrode resulted in the release of iron ions from the carbon steel thereby increasing the rate of BPA removal and eliminating the need for iron salts. After the plasma/Fenton treatment, >97% of the residual iron salts were removed by coagulation/flocculation/sedimentation. Byproduct identification coupled with density functional theory (DFT) calculations confirmed that OH radical attack on BPA's hydroxyl group is the primary pathway for byproduct formation.

Bioaerosol Deposition to Food Crops near Manure Application: Quantitative Microbial Risk Assessment

Production of both livestock and food crops are central priorities of agriculture; however, food safety concerns arise where these practices intersect. In this study, we investigated the public health risks associated with potential bioaerosol deposition to crops grown in the vicinity of manure application sites. A field sampling campaign at dairy manure application sites supported the emission, transport, and deposition modeling of bioaerosols emitted from these lands following application activities. Results were coupled with a quantitative microbial risk assessment model to estimate the infection risk due to consumption of leafy green vegetable crops grown at various distances downwind from the application area. Inactivation of pathogens ( spp., spp., and O157:H7) on both the manure-amended field and on crops was considered to determine the maximum loading of pathogens to plants with time following application. Overall median one-time infection risks at the time of maximum loading decreased from 1:1300 at 0 m directly downwind from the field to 1:6700 at 100 m and 1:92,000 at 1000 m; peak risks (95th percentiles) were considerably greater (1:18, 1:89, and 1:1200, respectively). Median risk was below 1:10,000 at >160 m downwind. As such, it is recommended that a 160-m setback distance is provided between manure application and nearby leafy green crop production. Additional distance or delay before harvest will provide further protection of public health.

Emission and Dispersion of Bioaerosols from Dairy Manure Application Sites: Human Health Risk Assessment

In this study, we report the human health risk of gastrointestinal infection associated with inhalation exposure to airborne zoonotic pathogens emitted following application of dairy cattle manure to land. Inverse dispersion modeling with the USEPA's AERMOD dispersion model was used to determine bioaerosol emission rates based on edge-of-field bioaerosol and source material samples analyzed by real-time quantitative polymerase chain reaction (qPCR). Bioaerosol emissions and transport simulated with AERMOD, previously reported viable manure pathogen contents, relevant exposure pathways, and pathogen-specific dose-response relationships were then used to estimate potential downwind risks with a quantitative microbial risk assessment (QMRA) approach. Median 8-h infection risks decreased exponentially with distance from a median of 1:2700 at edge-of-field to 1:13 000 at 100 m and 1:200 000 at 1000 m; peak risks were considerably greater (1:33, 1:170, and 1:2500, respectively). These results indicate that bioaerosols emitted from manure application sites following manure application may present significant public health risks to downwind receptors. Manure management practices should consider improved controls for bioaerosols in order to reduce the risk of disease transmission.

Autism spectrum disorder: an omics perspective

Current directions in autism spectrum disorder (ASD) research may require moving beyond genetic analysis alone, based on the complexity of the disorder, heterogeneity and convergence of genetic alterations at the cellular/functional level. Mass spectrometry (MS) has been increasingly used to study CNS disorders, including ASDs. Proteomic research using MS is directed at understanding endogenous protein changes that occur in ASD. This review focuses on how MS has been used to study ASDs, with particular focus on proteomic analysis. Other neurodevelopmental disorders have been investigated using MS, including fragile X syndrome (FXS) and Smith-Lemli-Opitz Syndrome (SLOS), genetic syndromes highly associated with ASD comorbidity.

Comparison of PoraPak Rxn RP and XAD-2 adsorbents for monitoring dissolved hydrophobic organic contaminants

Accurate determination of the levels of dissolved hydrophobic organic contaminants (HOCs) is an important step in estimating the dynamics of their inputs and losses in aqueous systems. This study explores an alternative method for efficiently sampling dissolved HOCs while mitigating a number of sampling artifacts associated with traditional methods. The adsorption characteristics of a new polymeric resin, PoraPak Rxn RP (PPR), were assessed using sorption isotherm experiments and fixed bed adsorption studies. The adsorption capacities and breakthrough times for four model contaminants (phenol, p-nitrophenol, naphthalene, and 2,4,6-tribromophenol) were proportional to the contaminant's hydrophobicity. The ability of PPR to isolate dissolved polychlorinated biphenyls (PCBs) in real samples was compared with that of XAD-2, a well-known macroporous polymer that suffers from high background contamination. The results indicated that the PPR resin can be effectively used for monitoring HOCs, with low ∑PCB levels in blanks, decreasing solvent use, and reducing extraction times.

Mercury wet deposition in the eastern United States: characteristics and scavenging ratios

Wet deposition is an important atmospheric mercury (Hg) pathway between air and terrestrial ecosystems. It is measured at numerous locations in the United States (U. S.) as part of the Mercury Deposition Network (MDN). The annual Hg wet deposition flux in 2009 at four locations in the northeastern U. S. (MDN sites MD08, VT99, NY20, and NY43) ranged from 6.4 to 13.4 μg per m(2) year which is higher than modeled reactive Hg (RM) dry deposition for this region. The highest ambient RM concentrations were seen at MD08, which is closest to significant anthropogenic sources; however, the volume-weighted mean Hg concentrations in precipitation were similar at these four sites. Mass based scavenging ratios (SC) of RM ranged from 1700 to 4500. Differences in SCs were likely a result of differences in meteorological conditions, the forms of RM in the atmosphere, vertical concentration variations, and measurement uncertainties, including precipitation depth and RM concentrations. RM SCs were higher than those reported for other soluble species. Multiple linear regression suggests that gaseous oxidized Hg is responsible for the majority of the scavenged RM.