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The hidden cost of using low-resolution concentration data in the estimation of NH3 dry deposition fluxes.

ABSTRACT: Long-term monitoring stations for atmospheric pollutants are often equipped with low-resolution concentration samplers. In this study, we analyse the errors associated with using monthly average ammonia concentrations as input variables for bidirectional biosphere-atmosphere exchange models, which are commonly used to estimate dry deposition fluxes. Previous studies often failed to account for a potential correlation between ammonia exchange velocities and ambient concentrations. We formally derive the exact magnitude of these errors from statistical considerations and propose a correction scheme based on parallel measurements using high-frequency analysers. In case studies using both modelled and measured ammonia concentrations and micrometeorological drivers from sites with varying pollution levels, we were able to substantially reduce bias in the predicted ammonia fluxes. Neglecting to account for these errors can, in some cases, lead to significantly biased deposition estimates compared to using high-frequency instrumentation or corrected averaging strategies. Our study presents a first step towards a unified correction scheme for data from nation-wide air pollutant monitoring networks to be used in chemical transport and air quality models.

SUBMITTER: Schrader F

PROVIDER: S-EPMC5772562 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Project description:Size-segregated aerosol particles were collected using a high volume MOUDI sampler at a coastal urban site in Xiamen Bay, China, from March 2018 to June 2020 to examine the seasonal characteristics of aerosol and water-soluble inorganic ions (WSIIs) and the dry deposition of nitrogen species. During the study period, the annual average concentrations of PM1, PM2.5, PM10, and TSP were 14.8 ± 5.6, 21.1 ± 9.0, 35.4 ± 14.2 μg m−3, and 45.2 ± 21.3 μg m−3, respectively. The seasonal variations of aerosol concentrations were impacted by the monsoon with the lowest value in summer and the higher values in other seasons. For WSIIs, the annual average concentrations were 6.3 ± 3.3, 2.1 ± 1.2, 3.3 ± 1.5, and 1.6 ± 0.8 μg m−3 in PM1, PM1-2.5, PM2.5–10, and PM>10, respectively. In addition, pronounced seasonal variations of WSIIs in PM1 and PM1-2.5 were observed, with the highest concentration in spring-winter and the lowest in summer. The size distribution showed that SO42−, NH4+ and K+ were consistently present in the submicron particles while Ca2+, Mg2+, Na+ and Cl− mainly accumulated in the size range of 2.5–10 μm, reflecting their different dominant sources. In spring, fall and winter, a bimodal distribution of NO3− was observed with one peak at 2.5–10 μm and another peak at 0.44–1 μm. In summer, however, the fine mode peak disappeared, likely due to the unfavorable conditions for the formation of NH4NO3. For NH4+ and SO42−, their dominant peak at 0.25–0.44 μm in summer and fall shifted to 0.44–1 μm in spring and winter. Although the concentration of NO3–N was lower than NH4–N, the dry deposition flux of NO3–N (35.77 ± 24.49 μmol N m−2 d−1) was much higher than that of NH4–N (10.95 ± 11.89 μmol N m−2 d−1), mainly due to the larger deposition velocities of NO3–N. The contribution of sea-salt particles to the total particulate inorganic N deposition was estimated to be 23.9—52.8%. Dry deposition of particulate inorganic N accounted for 0.95% of other terrestrial N influxes. The annual total N deposition can create a new productivity of 3.55 mgC m−2 d−1, accounting for 1.3–4.7% of the primary productivity in Xiamen Bay. In light of these results, atmospheric N deposition could have a significant influence on biogeochemistry cycle of nutrients with respect to projected increase of anthropogenic emissions from mobile sources in coastal region. Supplementary Information The online version contains supplementary material available at 10.1007/s10874-021-09427-8.

Project description:BackgroundQuitlines (QLs) are free, effective sources of treatment for tobacco dependence. Although the QL number is toll-free, the use of cell phones as the sole source of telephony may impose an unintended cost, in terms of cell minutes.ObjectivesTo quantify the use of cell-only telephony among self-pay or Medicaid smokers, assess their calling plans, and estimate the impact of a typical course of QL counseling.MethodsA survey of smokers age at least 18 years visiting an American urban emergency department from April to July, 2013.ResultsSeven-hundred seventy-three smokers were surveyed, of whom 563 (72.8%) were low-income, defined as having Medicaid or no insurance. All low-income smokers had at least one phone: 48 (8.5%) reported land-lines only, 159 (28.2%) land-lines and cells, and 356 (63.2%) cells only. Of the cell phone owners, monthly calling plans provided unlimited minutes for 339/515 (65.8%), at most 250 minutes for 124 (24.1%), and more than 250 minutes for 52 (10.0%). Another recent trial found that QL users make a median of 1 call lasting 28 minutes, with the 75th and 90th percentiles of calls and minutes at 3 and 4 calls, and 48 and 73.6 minutes, respectively. Thus, robust use of QL services could consume 11%-29% of a low-income smoker's typical 250 monthly cell minutes.ConclusionAmong low-income smokers, cell phones are often the sole telephone. Robust use of the QL may impose a substantial burden on low-income smokers' calling plans, and therefore deter use of the QL. Exempting calls to QLs from counting against smokers' plans may help promote QL utilization.ImplicationsLow-income individuals have high rates of smoking, and are more likely to own only cell phones, not landlines, for telephone access. Because cell phone calling plans often have limited numbers of monthly minutes, cell-only individuals may have to spend a substantial proportion of their monthly minutes on QL services. This may act as a deterrent to using an otherwise free, effective means of treatment for tobacco dependence. Exempting QLs from monthly calling plans may improve access for low-income smokers.

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The hidden cost of using low-resolution concentration data in the estimation of NH3 dry deposition fluxes.

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