ALBERT

Description: Manganoquadratite, ideally AgMnAsS3, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as dark gray, anhedral to subhedral grains up 0.5 mm across, closely associated with alabandite, Mn-rich calcite, Mn-rich sphalerite, proustite, pyrite, pyrrhotite, tennantite, argentotennantite, stannite, and other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S. Manganoquadratite is opaque with a metallic luster and possesses a reddish-brown streak. It is brittle, the Vickers microhardness (VHN10) is 81 kg/mm2 (range 75–96) (corresponding Mohs hardness of 2–2½). The calculated density is 4.680 g/cm3 (on the basis of the empirical formula). In plane-polarized reflected light, manganoquadratite is moderately bireflectant and very weakly pleochroic from dark gray to a blue gray. Internal reflections are absent. Between crossed polars, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 29.5, 31.8 (471.1 nm), 28.1, 30.5 (548.3 nm), 27.3, 29.3 (586.6 nm), and 26.0, 28.2 (652.3 nm), respectively.Manganoquadratite is tetragonal, space group P4322, with unit-cell parameters: a = 5.4496(5), c = 32.949(1) Å, V = 978.5(1) Å3, c:a = 6.046, Z = 8. The structure, refined to R1 = 0.0863 for 907 reflections with Fo 〉 4σ(Fo), consists of a stacking along [001] of alabandite-like Mn2S2 layers connected to each to other by a couple of AgAsS2 sheets where As3+ forms typical AsS3 groups, whereas Ag+ cations are fivefold coordinated. The six strongest lines in the observed X-ray powder-diffraction pattern [d in Å (I/I0) (hkl)] are: 3.14 (60) (116), 2.739 (50) (0 0 12), 2.710 (100) (200), 1.927(70) (2 0 12 + 220), 1.645 (25) (3 0 16), and 1.573 (20) (22 12).Electron microprobe analyses gave the chemical formula (on the basis of six atoms) (Ag0.95Cu0.05)∑=1.00 (Mn0.96Pb0.04)∑=1.00(As0.87Sb0.14)∑=1.01S2.99, leading to the simplified formula AgMnAsS3.The name was chosen to indicate the close analogy of the formula and unit-cell dimensions with quadratite, Ag(Cd,Pb)(As,Sb)S3. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA 2011-008.

Description: Menchettiite, ideally AgPb2.40Mn1.60Sb3As2S12, is a new mineral from the Uchucchacua polymetallic deposit, Oyon district, Catajambo, Lima Department, Peru. It occurs as black, anhedral to subhedral grains up to 200 µm across, closely associated with orpiment, tennantite/tetrahedrite, other unnamed minerals of the system Pb-Ag-Sb-Mn-As-S, and calcite. Menchettiite is opaque with a metallic luster and possesses a black streak. It is brittle, with uneven fracture; the Vickers microhardness (VHN100) is 128 kg/mm2 (range 119–136) (corresponding to a Mohs hardness of 2½–3). The calculated density is 5.146 g/cm3 (on the basis of the empirical formula). In plane-polarized incident light, menchettiite is weakly to moderately bireflectant and weakly pleochroic from dark gray to a dark green. Internal reflections are absent. Between crossed polarizers, the mineral is anisotropic, without characteristic rotation tints. Reflectance percentages (Rmin and Rmax) for the four standard COM wavelengths are 33.1, 39.8 (471.1 nm), 31.8, 38.0 (548.3 nm), 30.9, 37.3 (586.6 nm), and 29.0, 35.8 (652.3 nm), respectively.Menchettiite is monoclinic, space group P21/n, with unit-cell parameters: a = 19.233(2), b = 12.633(3), c = 8.476(2) Å, ß = 90.08(2)°, V = 2059.4(8) Å3, a: b: c 1.522:1:0.671, Z = 2, and it is twinned on {100}. The crystal structure was refined to R = 0.0903 for 2365 reflections with Fo 〉 4s(Fo) and it resulted to be topologically identical to those of ramdohrite, uchucchacuaite, and fizélyite. The six strongest X-ray powder-diffraction lines [d in Å (I/I0) (hkl)] are: 3.4066 (39) (3¯12), 3.4025 (39) (312), 3.2853 (100) (520), 2.8535 (50) (2¯32), 2.8519 (47) (232), and 2.1190 (33) (004). Electron-microprobe analyses gave the chemical formula Ag1.95Cu0.01Pb4.81Mn3.20Fe0.02Zn0.01Sb6.09As3.94Bi0.01S23.95Se0.01, on the basis of 44 atoms and according to the structure refinement results. Menchettiite can be classified among the Sb-rich members of the lillianite homeotypic series, which are described with the general formula AgxPb3-2xSb2+xS6. Besides the heterovalent substitution 2Pb2+ ? Ag+ + Sb3+ taken into consideration by the above formula, two isovalent substitutions relate menchettiite to the other lillianite homeotypes, i.e., Mn2+ ? Pb2+ and As3+ ? Sb3+. The name is after Silvio Menchetti (1937–), Professor of Mineralogy and Crystallography at the University of Florence. The new mineral and mineral name have been approved by the Commission on New Minerals, Nomenclature and Classification, IMA (2011–009).

Description: Field blanks (bQF) and backup filters (quartz-fiber behind quartz-fiber filter; QBQ) have been adopted by US long-term air quality monitoring networks to estimate PM2.5 organic carbon (OC) sampling artifacts. This study documents bQF and QBQ carbon levels for the: 1) Interagency Monitoring of Protected Visual Environments (IMPROVE); 2) Speciation Trends Network (STN; part of the Chemical Speciation Network [CSN]); and 3) Southeastern Aerosol Research and Characterization (SEARCH) networks and examines the similarities/differences associated with network-specific sampling protocols. A higher IMPROVE sample volume and smaller filter deposit area results in PM2.5 areal density (μg/cm2 on filter) 3–11 times those of STN/CSN and SEARCH samples for the same ambient PM2.5 concentrations, thus reducing the relative contribution of sampling artifacts from passive OC adsorption. A relatively short (1–15 min) passive exposure period of STN/CSN and SEARCH bQF OC (0.8–1 μg/cm2) underestimates positive and negative OC artifacts resulting from passive adsorption or evaporation of semi-volatile organic compounds on quartz-fiber filters. This is supported by low STN/CSN and SEARCH bQF levels and lack of temporal or spatial variability among the sites within the networks. With a much longer period, ~7 days of ambient passive exposure, average IMPROVE bQF and QBQ OC are comparable (2.4±0.5 and 3.1±0.8 μg/cm2, respectively) and more than twice levels found in the STN/CSN and SEARCH networks. Sampling artifacts in STN/CSN were estimated from collocated IMPROVE samples based on linear regression. At six of the eight collocated sites in this study, STN/CSN bQFs underestimated OC artifacts by 11–34%. Using a preceding organic denuder in the SEARCH network minimized passive adsorption on QBQ, but OC on QBQ may not be attributed entirely to the negative sampling artifact (e.g., evaporated or volatilized OC from the front filter deposits after sample collection).

Description: Archived Federal Reference Method (FRM) Teflon filters used by state regulatory agencies for measuring PM2.5 mass were acquired from 15 sites throughout the southeastern US and analyzed for water-soluble organic carbon (WSOC), water-soluble ions and carbohydrates to investigate biomass burning contributions to fine aerosol mass. Based on over 900 filters that spanned all of 2007, levoglucosan and K+ were studied in conjunction with MODIS Aqua fire count data to compare their performances as biomass burning tracers. Levoglucosan concentrations exhibited a distinct seasonal variation with large enhancement in winter and spring and a minimum in summer, and were well correlated with fire counts, except in winter when residential wood burning contributions were significant. In contrast, K+ concentrations had no apparent seasonal trend and poor correlation with fire counts. Levoglucosan and K+ only correlated well in winter (r2=0.59) when biomass burning emissions were highest, whereas in other seasons they were not correlated due to the presence of other K+ sources. Levoglucosan also exhibited larger spatial variability than K+. Both species were higher in urban than rural sites (mean 44% higher for levoglucosan and 86% for K+). Positive Matrix Factorization (PMF) was applied to analyze PM2.5 sources and four factors were resolved: biomass burning, refractory material, secondary light absorbing WSOC and secondary sulfate/WSOC. The biomass burning source contributed 13% to PM2.5 mass annually, 27% in winter, and less than 2% in summer, consistent with other souce apportionment studies based on levoglucosan, but lower in summer compared to studies based on K+.

Description: Secondary organic aerosol (SOA) in the southeastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24-h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan 〈 50 ng m−3), WSOC and sulfate were highly correlated with PM2.5 mass (r2~0.7). Both components comprised a large mass fraction of PM2.5 (13% and 31%, respectively, or ~25% and 50% for WSOM and ammonium sulfate). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly linked to faster photochemistry and/or synoptic meteorology and less due to enhanced biogenic hydrocarbon emissions. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC were associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55 mgC m−2 h−1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the southeastern US, confirming the importance of SOA and the roles of both biogenic and anthropogenic emissions.

Description: Light absorption of fine particle (PM2.5) aqueous extracts between wavelengths of 200 and 800 nm were investigated from two data sets: 24-h Federal Reference Method (FRM) filter extracts from 15 Southeastern US monitoring sites over the year of 2007 (900 filters), and online measurements from a Particle-Into-Liquid Sampler deployed from July to mid-August 2009 in Atlanta, Georgia. Three main sources of soluble chromophores were identified: biomass burning, mobile source emissions, and compounds linked to secondary organic aerosol (SOA) formation. Absorption spectra of aerosol solutions from filter extracts were similar for different sources. Angstrom exponents were ~7±1 for biomass burning and non-biomass burning-impacted 24-h filter samples (delineated by a levoglucosan concentration of 50 ng m−3) at both rural and urban sites. The absorption coefficient from measurements averaged between wavelength 360 and 370 nm (Abs365, in units m−1) was used as a measure of overall brown carbon light absorption. Biomass-burning-impacted samples were highest during winter months and Abs365 was correlated with levoglucosan at all sites. During periods of little biomass burning in summer, light absorbing compounds were still ubiquitous and correlated with fine particle Water-Soluble Organic Carbon (WSOC), but comprised a much smaller fraction of the WSOC, where Abs365/WSOC (i.e., mass absorption efficiency) was typically ~3 times higher in biomass burning-impacted samples. Factor analysis attributed 50% of the yearly average Abs365 to biomass burning sources. Brown carbon from primary urban emissions (mobile sources) was also observed and accounted for ~10% of the regional yearly average Abs365. Summertime diurnal profiles of Abs365 and WSOC showed that morning to midday increases in WSOC from photochemical production were associated with a decrease in Abs365/WSOC. After noon, this ratio substantially increased, indicating that either some fraction of the non-light absorbing fresh SOA was rapidly (within hours) converted to chromophores heterogeneously, or that SOA from gas-particle partitioning later in the day was more light-absorbing. Factor analysis on the 24-h integrated filter data associated ~20 to 30% of Abs365 over 2007 with a secondary source that was highest in summer and also the main source for oxalate, suggesting that aqueous phase reactions may account for the light-absorbing fraction of WSOC observed throughout the Southeastern US in summer.

Description: Data from the Interagency Monitoring of Protected Visual Environments (IMPROVE) network are used to estimate organic mass to organic carbon (OM/OC) ratios across the United States by extending previously published multiple regression techniques. Our new methodology addresses common pitfalls of multiple regression including measurement uncertainty, colinearity of covariates, dataset selection, and model selection. As expected, summertime OM/OC ratios are larger than wintertime values across the US with all regional median OM/OC values tightly confined between 1.80 and 1.95. Further, we find that OM/OC ratios during the winter are distinctly larger in the eastern US than in the West (regional medians are 1.58, 1.64, and 1.85 in the great lakes, southeast, and northeast regions, versus 1.29 and 1.32 in the western and central states). We find less spatial variability in long-term averaged OM/OC ratios across the US (90% of our multiyear regressions estimate OM/OC ratios between 1.37 and 1.94) than previous studies (90% fell between 1.30 and 2.10). We attribute this difference largely to the inclusion of EC as a covariate in previous regression studies. Due to the colinearity of EC and OC, we find that up to one-quarter of the OM/OC estimates in a previous study are biased low. Assumptions about OC measurement artifacts add uncertainty to our estimates of OM/OC. In addition to estimating OM/OC ratios, our technique reveals trends that may be contrasted with conventional assumptions regarding nitrate, sulfate, and soil across the IMPROVE network. For example, our regressions show pronounced seasonal and spatial variability in both nitrate volatilization and sulfate neutralization and hydration.

Description: Fine particle (PM2.5) light absorption characteristics of aqueous extracts over wavelengths of 250 to 700 nm were investigated based on two data sets; 24-h Federal Reference Method (FRM) filter extracts from 15 southeastern US monitoring sites over the year of 2007 (900 filters), and online measurements from a Particle-Into-Liquid Sampler deployed from July to mid-August 2009 in Atlanta, Georgia. Three main sources of soluble chromophores were identified, biomass burning, mobile source emissions, and compounds linked to Secondary Organic Aerosol (SOA) formation. Absorption spectra of aerosol solutions from different sources were similar. Angstrom exponents were ~7±1 for biomass burning and non-biomass burning-impacted samples (delineated by a levoglucosan concentration of 50 ng m−3) at both rural and urban sites. The absorption coefficient from measurements averaged between wavelength 360 and 370 nm (Abs365, in units m−1) was used as a measure of overall brown carbon absorptivity. Biomass-burning-impacted samples were highest during colder months and Abs365 was correlated with levoglucosan at all sites. During periods of little biomass burning in summer, light absorbing compounds were still ubiquitous and correlated with fine particle Water-Soluble Organic Carbon (WSOC), but comprised a much smaller fraction of the WSOC, where Abs365/WSOC (i.e., mass absorption efficiency) was typically ~3 times higher in biomass burning-impacted samples. Factor analysis attributed 50% of the yearly average Abs365 to biomass burning sources. Brown carbon from primary urban emissions (mobile sources) was also observed and accounted for ~10% of the regional yearly average Abs365. Summertime diurnal profiles of Abs365 and WSOC showed that morning to midday increases in WSOC from photochemical production were associated with a decrease in Abs365/WSOC. After noon this ratio substantially increased, indicating that either some fraction of the non-light absorbing fresh SOA was rapidly (within hours) converted to chromophores heterogeneously, or that SOA from gas-particle partitioning later in the day was more light-absorbing. Factor analysis associated ~20 to 30% of Abs365 over 2007 with a secondary source that was highest in summer and also the main source for oxalic acid, suggesting that aqueous phase reactions may account for the light-absorbing fraction of WSOC observed throughout the southeastern US in summer.

Description: Archived Federal Reference Method (FRM) Teflon filters used by state regulatory agencies for measuring PM2.5 mass were acquired from 15 sites throughout the southeastern US and analyzed for Water-Soluble Organic Carbon (WSOC), water-soluble ions and carbohydrates to investigate biomass burning contributions to fine aerosol mass. Based on over 900 filters that spanned all of 2007, levoglucosan and K+ were studied in conjunction with MODIS Aqua fire count data to compare their performances as biomass burning tracers. Levoglucosan concentrations exhibited a distinct seasonal variation with large enhancement in winter and spring and a minimum in summer, and were well correlated with fire counts, except in winter when residential wood burning contributions were significant. In contrast, K+ concentrations had no apparent seasonal trend and poor correlation with fire counts. Levoglucosan and K+ only correlated well in winter (r2=0.59) when biomass burning emissions were highest, whereas in other seasons they were not correlated due to the presence of other K+ sources. Levoglucosan also exhibited larger spatial variability than K+. Both species were higher in urban than rural sites (mean 44% higher for levoglucosan and 86% for K+). Positive Matrix Factorization (PMF) was applied to analyze PM2.5 sources and four factors were resolved: biomass burning, refractory material, secondary light absorbing WSOC and secondary sulfate/WSOC. The biomass burning source contributed 13% to PM2.5 mass annually, 27% in winter, and less than 2% in summer, consistent with other souce apportionment studies based on levoglucosan, but lower in summer compared to studies based on K+.

Description: Secondary organic aerosol (SOA) in the Southeastern US is investigated by analyzing the spatial-temporal distribution of water-soluble organic carbon (WSOC) and other PM2.5 components from 900 archived 24 h Teflon filters collected at 15 urban or rural EPA Federal Reference Method (FRM) network sites throughout 2007. Online measurements of WSOC at an urban/rural-paired site in Georgia in the summer of 2008 are contrasted to the filter data. Based on FRM filters, excluding biomass-burning events (levoglucosan 〈 50 ng m−3), WSOC and sulfate were highly correlated with PM2.5 mass and both comprised a large mass fraction of PM2.5 (13% and 35%, respectively). Sulfate and WSOC both tracked ambient temperature throughout the year, suggesting the temperature effects were mainly on the photochemical processes that lead to secondary formation. FRM WSOC, and to a lesser extent sulfate, were spatially homogeneous throughout the region, yet WSOC was moderately enhanced (27%) in locations of greater predicted isoprene emissions in summer. A Positive Matrix Factorization (PMF) analysis identified two major source types for the summer WSOC; 22% of the WSOC were associated with ammonium sulfate, and 56% of the WSOC was associated with brown carbon and oxalate. A small urban excess of FRM WSOC (10%) was observed in the summer of 2007, however, comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008 showed substantially greater difference in WSOC (31%) relative to the FRM data, suggesting a low bias for urban filters. The measured Atlanta urban excess, combined with the estimated boundary layer heights, gave an estimated Atlanta daily WSOC production rate in August of 0.55 mg C m−2 h−1 between mid-morning and mid-afternoon. This study characterizes the regional nature of fine particles in the Southeastern US, confirming the importance of secondary organic aerosol and the roles of both biogenic and anthropogenic emissions.