Sherri A. Mason

High-levels of microplastic pollution in a large, remote, mountain lake

Despite the large and growing literature on microplastics in the ocean, little information exists on microplastics in freshwater systems. This study is the first to evaluate the abundance, distribution, and composition of pelagic microplastic pollution in a large, remote, mountain lake. We quantified pelagic microplastics and shoreline anthropogenic debris in Lake Hovsgol, Mongolia. With an average microplastic density of 20,264 particles km(-2), Lake Hovsgol is more heavily polluted with microplastics than the more developed Lakes Huron and Superior in the Laurentian Great Lakes. Fragments and films were the most abundant microplastic types; no plastic microbeads and few pellets were observed. Household plastics dominated the shoreline debris and were comprised largely of plastic bottles, fishing gear, and bags. Microplastic density decreased with distance from the southwestern shore, the most populated and accessible section of the park, and was distributed by the prevailing winds. These results demonstrate that without proper waste management, low-density populations can heavily pollute freshwater systems with consumer plastics.

Microplastic is an Abundant and Distinct Microbial Habitat in an Urban River

Recent research has documented microplastic particles (< 5 mm in diameter) in ocean habitats worldwide and in the Laurentian Great Lakes. Microplastic interacts with biota, including microorganisms, in these habitats, raising concerns about its ecological effects. Rivers may transport microplastic to marine habitats and the Great Lakes, but data on microplastic in rivers is limited. In a highly urbanized river in Chicago, Illinois, USA, we measured concentrations of microplastic that met or exceeded those measured in oceans and the Great Lakes, and we demonstrated that wastewater treatment plant effluent was a point source of microplastic. Results from high-throughput sequencing showed that bacterial assemblages colonizing microplastic within the river were less diverse and were significantly different in taxonomic composition compared to those from the water column and suspended organic matter. Several taxa that include plastic decomposing organisms and pathogens were more abundant on microplastic. These results demonstrate that microplastic in rivers are a distinct microbial habitat and may be a novel vector for the downstream transport of unique bacterial assemblages. In addition, this study suggests that urban rivers are an overlooked and potentially significant component of the global microplastic life cycle.

Complex Effects Arising in Smoke Plume Simulations due to Inclusion of Direct Emissions of Oxygenated Organic Species from Biomass Combustion

Oxygenated volatile organic species (oxygenates), including HCOOH, H 2 CO, CH 3 OH, HOCH 2 CHO (hydroxyacetaldehyde), CH 3 COOH, and C 6 H 5 OH, have recently been identified by Fourier transform infrared measurements as a significant component of the direct emissions from biomass combustion. These oxygenates have not generally been included in the hydrocarbon-based initial emission profiles used in previous photochemical simulations of biomass combustion smoke plumes. We explore the effects of oxygenates on this photochemistry by using an established initial emission hydrocarbon profile and comparing simulation results obtained both with and without addition of the above six oxygenates. Simulations are started at noon and carried out for 30 hours in an expanding Lagrangian plume. After an initial transient period during which [NO x ] falls rapidly, conditions within the oxygenated smoke plume are found to be strongly NO x -sensitive, and the simulated final species profile is thus strongly dependent upon the Δ[NO]/Δ[CO] initial emission profile. Oxygenate addition results in very significant and complex effects on net O 3 production, as well as on the relative amounts of long-lived HO, and NO, reservoir species (H 2 O 2 , organic hydroperoxides, HNO 3 , and peroxyacetyl nitrate (PAN)) that are mixed into the surrounding atmosphere. Oxygenates may either increase or decrease net O 3 production (depending upon the initial Δ[NO]/Δ[CO]). However, they always increase H 2 O 2 and organic hydroperoxide production as a result of increased rates of radical + radical reactions. These effects spring largely from accelerated removal of NO, from the smoke plume due to increased radical concentrations resulting both from photolysis of oxygenates (mainly CH 2 O) and from their relatively high reactivity. Predicted concentrations of H 2 O 2 , Δ[O 3 ]/Δ[CO], Δ[NH 3 ]/Δ[CO], and Δ[HCOOH]/Δ[CO] are compared with some available measured values.

Microplastic contamination in the San Francisco Bay, California, USA

Despite widespread detection of microplastic pollution in marine environments, data describing microplastic abundance in urban estuaries and microplastic discharge via treated municipal wastewater are limited. This study presents information on abundance, distribution, and composition of microplastic at nine sites in San Francisco Bay, California, USA. Also presented are characterizations of microplastic in final effluent from eight wastewater treatment plants, employing varying treatment technologies, that discharge to the Bay. With an average microplastic abundance of 700,000particles/km(2), Bay surface water appears to have higher microplastic levels than other urban waterbodies sampled in North America. Moreover, treated wastewater from facilities that discharge into the Bay contains considerable microplastic contamination. Facilities employing tertiary filtration did not show lower levels of contamination than those using secondary treatment. As textile-derived fibers were more abundant in wastewater, higher levels of fragments in surface water suggest additional pathways of microplastic pollution, such as stormwater runoff.

Rate constants for the gas-phase reactions of NO3 radicals and O3 with C6-C14 1-alkenes and 2-methyl-1-alkenes at 296 +/- 2 K.

Rate constants for the gas-phase reactions of NO(3) radicals and O(3) with a series of C(6)-C(14) 1-alkenes and 2-methyl-1-alkenes have been measured at 296 +/- 2 K and atmospheric pressure of air using relative rate methods. For the NO(3) radical reactions, the rate constants obtained (in units of 10(-14) cm(3) molecule(-1) s(-1)) were: 1-hexene, 2.00 +/- 0.16; 1-octene, 2.35 +/- 0.15; 1-decene, 2.55 +/- 0.16; 1-dodecene, 2.79 +/- 0.36; 1-tetradecene, 2.87 +/- 0.21; 2-methyl-1-pentene, 43.8 +/- 2.3; 2-methyl-1-hexene, 52.4 +/- 2.5; 2-methyl-1-octene, 57.8 +/- 2.6; 2-methyl-1-nonene, 60.8 +/- 2.9; 2-methyl-1-undecene, 60.8 +/- 3.3; 2-methyl-1-tridecene, 60.3 +/- 3.4; and cycloheptene, 49.4 +/- 2.0. For the O(3) reactions, the rate constants obtained (in units of 10(-17) cm(3) molecule(-1) s(-1)) were: 1-hexene, 0.898 +/- 0.054; 1-heptene, 1.05 +/- 0.07; 1-octene, 1.01 +/- 0.04; 1-decene, 1.11 +/- 0.05; 1-dodecene, 1.38 +/- 0.14; 1-tridecene, 1.92 +/- 0.12; 1-tetradecene, 2.44 +/- 0.24; 2-methyl-1-pentene, 1.26 +/- 0.13; 2-methyl-1-heptene, 1.35 +/- 0.05; 2-methyl-1-octene, 1.38 +/- 0.06; 2-methyl-1-decene, 1.48 +/- 0.07; 2-methyl-1-undecene, 1.46 +/- 0.11; and 2-methyl-1-tridecene, 2.85 +/- 0.42. The rate constants for the NO(3) radical reactions significantly increase with increasing carbon number, attaining a plateau at > or = C(14) for the 1-alkenes and at C(10)-C(14) for the 2-methyl-1-alkenes. In contrast, the rate constants for O(3) reactions increase only slightly with increasing carbon number up to approximately C(10) for the 1-alkenes and approximately C(12) for the 2-methyl-1-alkenes, with the significant increase in the measured rate constants for the > C(10) 1-alkenes and > C(12) 2-methyl-1-alkenes possibly being due to heterogeneous reactions. Reasons for the observed trends in NO(3) radical and O(3) reaction rate constants with alkene carbon number are discussed.

Anthropogenic contamination of tap water, beer, and sea salt

Plastic pollution has been well documented in natural environments, including the open waters and sediments within lakes and rivers, the open ocean and even the air, but less attention has been paid to synthetic polymers in human consumables. Since multiple toxicity studies indicate risks to human health when plastic particles are ingested, more needs to be known about the presence and abundance of anthropogenic particles in human foods and beverages. This study investigates the presence of anthropogenic particles in 159 samples of globally sourced tap water, 12 brands of Laurentian Great Lakes beer, and 12 brands of commercial sea salt. Of the tap water samples analyzed, 81% were found to contain anthropogenic particles. The majority of these particles were fibers (98.3%) between 0.1–5 mm in length. The range was 0 to 61 particles/L, with an overall mean of 5.45 particles/L. Anthropogenic debris was found in each brand of beer and salt. Of the extracted particles, over 99% were fibers. After adjusting for particles found in lab blanks for both salt and beer, the average number of particles found in beer was 4.05 particles/L with a range of 0 to 14.3 particles/L and the average number of particles found in each brand of salt was 212 particles/kg with a range of 46.7 to 806 particles/kg. Based on consumer guidelines, our results indicate the average person ingests over 5,800 particles of synthetic debris from these three sources annually, with the largest contribution coming from tap water (88%).

Synthetic Polymer Contamination in Bottled Water

Eleven globally sourced brands of bottled water, purchased in 19 locations in nine different countries, were tested for microplastic contamination using Nile Red tagging. Of the 259 total bottles processed, 93% showed some sign of microplastic contamination. After accounting for possible background (lab) contamination, an average of 10.4 microplastic particles >100 um in size per liter of bottled water processed were found. Fragments were the most common morphology (66%) followed by fibers. Half of these particles were confirmed to be polymeric in nature using FTIR spectroscopy with polypropylene being the most common polymer type (54%), which matches a common plastic used for the manufacture of bottle caps. A small fraction of particles (4%) showed the presence of industrial lubricants. While spectroscopic analysis of particles smaller than 100 um was not possible, the adsorption of the Nile Red dye indicates that these particles are most probably plastic. Including these smaller particles (6.5–100 um), an average of 325 microplastic particles per liter of bottled water was found. Microplastic contamination range of 0 to over 10,000 microplastic particles per liter with 95% of particles being between 6.5 and 100 um in size. Data suggests the contamination is at least partially coming from the packaging and/or the bottling process itself. Given the prevalence of the consumption of bottled water across the globe, the results of this study support the need for further studies on the impacts of micro- and nano- plastics on human health.

Kinetics and products of the OH radical-initiated reaction of 1,4-butanediol and rate constants for the reactions of OH radicals with 4-hydroxybutanal and 3-hydroxypropanal.

Rate constants for the gas-phase reactions of the OH radical with 1,4-butanediol,4-hydroxybutanal, and 3-hydroxypropanalwere measured at 298 +/- 2 K and atmospheric pressure using a relative rate technique and with 4-hydroxybutanal and 3-hydroxypropanal being formed in situ from the OH + 1,4-butanediol reaction, and were (in units of 10(-11) cm(3) molecule(-1) s(-1)) 3.67 +/- 0.31, 3.0(-1.0)(+1.5), and 3.5(-1.0)(+1.3), respectively, with the latter being a lower limit because of the possibility of second-generation formation of 3-hydroxypropanal from OH + 4-hydroxybutanal. The measured formation yields of 4-hydroxybutanal and 3-hydroxypropanal from the OH + 1,4-butanediol reaction in the presence of NO were 58 +/- 19% and 55 +/- 12%, respectively. In addition to the formation of 4-hydroxybutanal and 3-hydroxypropanal, gas chromatography-mass spectrometric analyses of reacted OH + 1,4-butanediol reactionsshowedformation of glycolaldehyde [HOCH(2)CHO], malonaldehyde [HC(O)CH2CHO], and 1,4-butanedial [HC(O)CH(2)CH(2)CHO]. Glycolaldehyde, malonaldehyde, and 1,4-butanedial are expected products of the reaction of OH radicals with 4-hydroxybutanal, and glycolaldehyde and malonaldehyde are expected products of the reaction of OH radicals with 3-hydroxypropanal. Reaction mechanisms are presented and discussed.

Microplastic in riverine fish is connected to species traits

Microplastic is a contaminant of concern worldwide. Rivers are implicated as major pathways of microplastic transport to marine and lake ecosystems, and microplastic ingestion by freshwater biota is a risk associated with microplastic contamination, but there is little research on microplastic ecology within freshwater ecosystems. Microplastic uptake by fish is likely affected by environmental microplastic abundance and aspects of fish ecology, but these relationships have rarely been addressed. We measured the abundance and composition of microplastic in fish and surface waters from 3 major tributaries of Lake Michigan, USA. Microplastic was detected in fish and surface waters from all 3 sites, but there was no correlation between microplastic concentrations in fish and surface waters. Rather, there was a significant effect of functional feeding group on microplastic concentration in fish. Neogobius melanostomus (round goby, a zoobenthivore) had the highest concentration of gut microplastic (19 particles fish−1) compared to 10 other fish taxa measured, and had a positive linear relationship between body size and number of microplastic particles. Surface water microplastic concentrations were lowest in the most northern, forested watershed, and highest in the most southern, agriculturally dominated watershed. Results suggest microplastic pollution is common in river food webs and is connected to species feeding characteristics. Future research should focus on understanding the movement of microplastic from point-source and diffuse sources and into aquatic ecosystems, which will support pollution management efforts on inland waters.