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Events Pre-1600

598 – Balkan Campaign: The Avars lift the siege at the Byzantine stronghold of Tomis. Their leader Bayan I retreats north of the Danube River after the Avaro-Slavic hordes are decimated by the plague. *1282 – The people of Sicily rebel against the Angevin king Charles I, in what becomes known as the Sicilian Vespers. *1296 – Edward I sacks Berwick-upon-Tweed, during armed conflict between Scotland and England. 1601–1900 *1699 – Guru Gobind Singh establishes the Khalsa in Anandpur Sahib, Punjab. *1815 – Joachim Murat issues the Rimini Proclamation which would later inspire Italian unification. *1818 – Physicist Augustin Fresnel reads a memoir on optical rotation to the French Academy of Sciences, reporting that when polarized light is "depolarized" by a Fresnel rhomb, its properties are preserved in any subsequent passage through an optically-rotating crystal or liquid. *1822 – The Florida Territory i

Identification of chemistry-dependent artifacts on gravimetric PM fine readings at the T1 site during the MILAGRO field campaign

Athanasios Nenes

As part of the MIRAGE (MILAGRO) study conducted 7-30 March 2006 in Mexico City and its Metropolitan Area (MCMA), fine particulate matter (PM2.5) was collected using two Tapered Element Oscillating Microbalance (TEOM) systems, and a Partisol instrument at the T1 super-site (Tecamac, State of Mexico). Inorganic analysis was performed on filter-based (PM1, PM2.5-URG) measurements also collected at this site. Measurements from the gravimetric (TEOMs, Partisol) and URG systems were inter-compared with chemical speciation measurements using a Particle Into Liquid Sampler (PILS) and Thermal Optical methods.Mass and chemical balances applied over the first part of the study (11-22 March) showed that a TEOM using a device (SES) which reduces particle-bound water and retains a fraction of semi-volatile compounds (SVM) gives readings ∼30% larger than a conventional TEOM. In the second part of the study (26-30 March), the loss of SVM during TEOM-heated filter collection (both systems) represented a significant fraction of PM2.5 mass due to changes in particle composition. Overall, when nonvolatile nitrate dominated (i.e., when associated with crustal species and not NH4+) and/or sulfate dominates (SO42-/NO3- molar ratio is >1), PM2.5 mass readings are in agreement with those reported for the T1 site if TEOM is using a SES device. However, when volatile nitrate dominates (i.e., NH4NO3) or SO42-/NO3- molar ratio is <1, a larger fraction is lost from both TEOMs (with or without the SES device). Under the latter regime, uncertainties are large and gravimetric losses may reach 30%-50%. The gravimetric PARTISOL instrument recorded lower readings under all of the aforementioned conditions with differences versus TEOMs decreasing with increasing RH. These findings call for a careful characterization of such volatilization biases to improve current PM (PM10, PM2.5) measurements/networks, especially in alkaline-rich environments that can favor such biases.With regards to PM1 and PM2.5 filter-based measurements, findings are: 1) crustal-related elements are important features in the PM2.5-1 size fraction; 2) a factor of ∼2 overestimation of SO42- concentrations is recorded on substrates during PM collection and 3) main elements of a typical urban aerosol size distribution are concentrated in the 1μm (versus 2.5μm) size fraction. © 2010 Elsevier Ltd.

2011

Identification of chemistry-dependent artifacts on gravimetric PM fine readings at the T1 site during the MILAGRO field campaign

Athanasios Nenes

2011