Global health organizations recommend the use of cloth face coverings to slow the spread of COVID-19. Seemingly overnight, companies whose primary business is in no way related to healthcare or personal protective equipment—from mattresses manufacturers to big box stores—transitioned into the “mask business.” Many companies advertise antimicrobial masks containing silver, copper, or other antimicrobials. Often, the techniques used to load such antimicrobials onto mask fibers are undisclosed, and the potential for metal leaching from these masks is yet unknown. We exposed nine so-called “antimicrobial” face masks (and one 100% cotton control mask) to deionized water, laundry detergent, and artificial saliva to quantify the leachable silver and copper that may occur during mask washing and wearing. Leaching varied widely across manufacturer, metal, and leaching solution, but in some cases was as high as 100% of the metals contained in the as-received mask after 1 h of exposure.

Abstract. Atmospheric ammonia (NH3) is a critical component of our atmosphere that contributes to air quality degradation and reactive nitrogen deposition; however, our knowledge of NH3 in urban environments remains limited. Year-long ambient NH3 and related species were measured for concentrations and the nitrogen isotopic compositions (δ15N) of NH3 and particulate ammonium (pNH4+) were measured to understand the temporal sources and chemistry of NH3 in a northeastern US urban environment. We found that urban NH3 and pNH4+ concentrations were elevated compared to regional rural background monitoring stations, with seasonally significant variations. Local and transported sources of NHx (NH3+ pNH4+) were identified using polar bivariate and statistical back trajectory analysis, which suggested the importance of vehicles, volatilization, industry, and stationary fuel combustion emissions. Utilizing a uniquely positive δ15N(NH3) emission source signature from vehicles, a Bayesian stable isotope mixing model (SIMMR) indicates that vehicles contribute 46.8±3.5 % (mean ±1σ) to the annual background level of urban NHx, with a strong seasonal pattern with higher relative contribution during winter (56.4±7.6 %) compared to summer (34.1±5.5 %). The decrease in the relative importance of vehicle emissions during the summer was suggested to be driven by temperature-dependent NH3 emissions from volatilization sources, seasonal fuel-combustion emissions related to energy generation, and change in seasonal transport patterns based on wind direction, back trajectory, and NH3 emission inventory analysis. This work highlights that reducing vehicle NH3 emissions should be considered to improve wintertime air quality in this region.

Abstract. Atmospheric ammonia (NH3) is a critical component of our atmosphere that contributes to air quality degradation and reactive nitrogen deposition; however, our knowledge of NH3 in urban environments remains limited. Year-long ambient NH3 and related species were measured for concentrations and the nitrogen isotopic compositions (δ15N) of NH3 and particulate ammonium (pNH4+) to understand the temporal sources and chemistry of NH3 in a northeastern US urban environment. We found that urban NH3 and pNH4+ concentrations were elevated compared to regional rural background monitoring stations, with seasonally significant variations. Local and transported sources of NHx (NH3 + pNH4+) were identified using polar bivariate and statistical back trajectory analysis, which suggested the importance of vehicles, volatilization, industry, fuel combustion, and biomass burning emissions. Utilizing a uniquely positive δ15N(NH3) emission source signature from vehicles, a Bayesian stable isotope mixing model indicates that vehicles contribute 30.7±11.6 % (mean±1σ) to the annual background level of urban NHx, with a strong seasonal pattern with higher relative contribution during winter (45.8±13.0 %) compared to summer (20.8±9.7 %). The decrease in the relative importance of vehicle emissions during the summer was suggested to be driven by temperature-dependent NH3 emissions from volatilization sources based on wind direction, back trajectory, and NH3 emission inventory analysis. This work highlights that reducing vehicle NH3 emissions should be considered to improve wintertime air quality in this region.