Non-Standard Errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

Non-standard errors

In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence generating process (EGP). We claim that EGP variation across researchers adds uncertainty: Non-standard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for better reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants

A new method to study aerosol source contributions along the tracks of air parcels and its application to the near-ground level aerosol chemical composition in central Europe

A novel method is, presented to reveal the significance and contribution of source types and characteristic formation times for individual aerosol constituents: Backward trajectory analyses are used to allocate time-resolved information about residence time of air masses over different types of ground surfaces. The correlations between the residence time of air mass over individual ground surface types and aerosol constituent concentrations (or particulate matter mass fractions) are investigated by a time-weighting method. The correlation coefficients between the concentrations of individual aerosol constituents and the residence times of air masses over certain types of ground surfaces at a certain time difference to arrival time were used to compose time profiles'. These are suggested to reflect the time-resolved ground emissions' influence on aerosol composition, which is particularly relevant for secondary aerosol constituents. The method has been applied to aerosol chemical composition data from various seasons and from rural and urban sites in Germany. For various ground types, we obtain correlations between weighted (and normalized) residence times ('source loadings') on one hand and the abundances of trace constituents known as markers for marine (Na, Cl), continental-rural (e.g. mineral dust components) and industrial sources (e.g., organic and elemental C, As, Pb) on the other hand. The occurrence of super-pm particulate NO3 in central Europe is found to originate largely in the marginal seas. The time profiles indicate that the characteristic formation time of the secondary aerosol is 48-72 h, while the coarse mode particulate matter including some heavy metals was determined by emissions < 36 h back. The occurrence of particulate elemental carbon was temporally bimodal with regard to the, elapsed time since emission (maxima at At 60 h and At = 12-24 h), which indicates the presence of two types undergoing a selection process during aging. The factors which explained most of the variability of the aerosol chemical composition were the season and the type of ground surface in contact with the air mass during its transport. More immediate influences on the samples, such as the weather conditions during sampling and the type of site (rural or urban) were distinctly less significant. (C) 2002 Elsevier Science Ltd. All rights reserved

Determination of UV filters in river water samples by in-line SPE-CE-MS

10.1002/elps.201200267The use of SPE coupled in-line to CE using electrospray MS detection (in-line SPECE- ESI-MS) was investigated for the preconcentration and separation of four UV filters: benzophenone-3 (BP-3), 2,2-dihydroxy-4-methoxybenzophenone (DHMB), 2,4- dihydroxybenzophenone (DHB) and 2-phenylbenzimidazole sulphonic acid (PMDSA). First, a CE-ESI-MS method was developed and validated using standard samples, obtaining LODs between 0.06 g/mL and 0.40 g/mL. For the in-line SPE-CE-ESI-MS method, three different sorbents were evaluated and compared: Oasis HLB, Oasis MCX, and Oasis MAX. For each sorbent, the main parameters affecting the preconcentration performance, such as sample pH, volume, and composition of the elution plug, and sample injection time were studied. The Oasis MCX sorbent showed the best performance and was used to validate the in-line SPE-CE-ESI-MSmethodology. The LODs reached for standard samples were in the range between 0.01 and 0.05 ng/mL with good reproducibility and the developed strategy provided sensitivity enhancement factors between 3400-fold and 34 000-fold. The applicability of the developed methodology was demonstrated by the analysis of UV filters in river water samples

A new method to study aerosol source contributions along the tracks of air parcels and its application to the near-ground level aerosol chemical composition in central Europe

A novel method is, presented to reveal the significance and contribution of source types and characteristic formation times for individual aerosol constituents: Backward trajectory analyses are used to allocate time-resolved information about residence time of air masses over different types of ground surfaces. The correlations between the residence time of air mass over individual ground surface types and aerosol constituent concentrations (or particulate matter mass fractions) are investigated by a time-weighting method. The correlation coefficients between the concentrations of individual aerosol constituents and the residence times of air masses over certain types of ground surfaces at a certain time difference to arrival time were used to compose time profiles'. These are suggested to reflect the time-resolved ground emissions' influence on aerosol composition, which is particularly relevant for secondary aerosol constituents. The method has been applied to aerosol chemical composition data from various seasons and from rural and urban sites in Germany. For various ground types, we obtain correlations between weighted (and normalized) residence times ('source loadings') on one hand and the abundances of trace constituents known as markers for marine (Na, Cl), continental-rural (e.g. mineral dust components) and industrial sources (e.g., organic and elemental C, As, Pb) on the other hand. The occurrence of super-pm particulate NO3 in central Europe is found to originate largely in the marginal seas. The time profiles indicate that the characteristic formation time of the secondary aerosol is 48-72 h, while the coarse mode particulate matter including some heavy metals was determined by emissions < 36 h back. The occurrence of particulate elemental carbon was temporally bimodal with regard to the, elapsed time since emission (maxima at At 60 h and At = 12-24 h), which indicates the presence of two types undergoing a selection process during aging. The factors which explained most of the variability of the aerosol chemical composition were the season and the type of ground surface in contact with the air mass during its transport. More immediate influences on the samples, such as the weather conditions during sampling and the type of site (rural or urban) were distinctly less significant. (C) 2002 Elsevier Science Ltd. All rights reserved

Transformation of aerosol chemical properties due to transport over a city

The change of the chemical composition of the near-ground level atmospheric aerosol was studied during two summer episodes by a Lagrangian type of experimental approach. Bulk and single-particle chemical analyses of ions and elements in the particulate phase were deployed. N(-III) and N(V) components were also measured in the gas-phase. The measurements were completed by particle size distributions. Secondary inorganic aerosols (SIA) and fine particles of ≈0.2–0.4 µm size were still elevated 50 km downwind of the city. The direct comparison of transport over the city in contrast to transport over the surrounding areas showed that SIA was formed from emission from the city within less than 3 h. Relative increases, i.e., enrichment during transport were observed for primary and secondary aerosol components. The degree of mixing on the individual particle level increased significantly during transport in the area. In particular, newly emitted carbonaceous particles became internally mixed within hours with pre-existing sulphate particles. Mostly due to secondary aerosol formation the average particle size (mass median diameter) of major constituents of the aerosol was significantly decreased while being transported over 13 h. Given recent insights which link fine particles number and mass concentrations with health risks, the results suggest that rural populations in areas which frequently are located within an urban plume might run an elevated health risk relative to populations in areas not affected by urban plumes

Dominant aerosol chemical components and their contribution to extinction during the Aerosols99 cruise across the Atlantic

The Aerosols99 cruise crossed the Atlantic Ocean from Norfolk, Virginia, to Cape Town, South Africa, during January and February of 1999. On the basis of back trajectories, aerosol number concentrations and size distributions, and trace gas concentrations, seven “air mass” regions were encountered. These included North America, Northern Hemisphere (NH) marine, African dust, a mixture of dust and biomass burning from Africa, biomass burning from Africa, Southern Hemisphere (SH) marine tropics, and SH marine temperate. Simultaneous measurements of aerosol chemical composition, number size distribution, scattering and absorption coefficients, vertical profiles, and optical depth allowed for a thorough characterization of the aerosol. Presented here are the concentrations and mass fractions of the aerosol chemical components that were dominant in each region and the aerosol scattering and absorption coefficients, single scattering albedos, Ångström exponents, and optical depths measured in each region. Also presented is the percent of the extinction measured at the surface due to each chemical component and mass extinction efficiencies of the individual aerosol components estimated from Mie calculations and a multiple linear regression. All results are reported at the measurement relative humidity of 55±5%. Non‐sea‐salt (nss) SO4= aerosol was a significant contributor to the submicron mass concentration in all air mass regions (mean mass fractions ranged from 20 to 67%). It made the largest contribution to submicron extinction in the North America region (45±30%, mean and 1σ standard deviation). Sea‐salt mean submicron mass fractions ranged from 9 to 49% with the lowest value in the biomass burning region and highest values in the NH marine and dust regions. Its contribution to submicron extinction ranged from a mean of 29 to 66%. Sea‐salt mean supermicron mass fractions ranged from 52 to 98% with the highest values in the marine regions. Its contribution to supermicron extinction ranged from 60 to 98%. Mean submicron and supermicron mass fractions of dust in the dust region were 22±3.3% (mean and 95% uncertainty) and 26±3.9%, respectively. Corresponding submicron and supermicron extinction contributions were 24±7.5 and 18±4.0%, respectively. Submicron mass fractions of particulate organic matter (POM) ranged from below detection limits in the dust region to 18±11% in the biomass burning region. Contributions to submicron extinction ranged from below detection limits to 24% in the North America region. In the biomass burning region the black carbon mean submicron mass fraction was 6.7±1.3% with a contribution of 6.4±2.7% to the submicron extinction. Extinction fractions of each component for particles with aerodynamic diameters less than 10 μm also are reported in the paper. Sea salt dominated the extinction measured at the surface due to sub‐10 μm aerosol for all air mass regions, even those influenced by continental sources. The fraction of the measured column aerosol optical depth due to aerosol within the boundary layer was estimated for the NH marine, dust, biomass burning, and SH marine tropics regions. Mean values ranged from 35±15% for the biomass burning region to 95±46% for the NH marine region