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Title: The T1-T2 study : evolution of aeorsol properties downwind of Mexico City.

Abstract

As part of a major atmospheric chemistry and aerosol field program carried out in March 2006, a study was conducted in the area to the north and northeast of Mexico City to investigate the evolution of aerosols and their associated optical properties in the first few hours after their emission. The focus of the T1-T2 aerosol study was to investigate changes in the specific absorption a{sub ABS} (absorption per unit mass, with unit of m{sup 2} g{sup -1}) of black carbon as it aged and became coated with compounds such as sulfate and organic carbon, evolving from an external to an internal mixture. Such evolution has been reported in previous studies. The T1 site was located just to the north of the Mexico City metropolitan area; the T2 site was situated approximately 35 km farther to the northeast. Nephelometers, particle soot absorption photometers, photoacoustic absorption spectrometers, and organic and elemental carbon analyzers were used to measure the optical properties of the aerosols and the carbon concentrations at each of the sites. Radar wind profilers and radiosonde systems helped to characterize the meteorology and to identify periods when transport from Mexico City over T1 and T2 occurred. Organic and elemental carbonmore » concentrations at T1 showed diurnal cycles reflecting the nocturnal and early morning buildup from nearby sources, while concentrations at T2 appeared to be more affected by transport from Mexico City. Specific absorption during transport periods was lower than during other times, consistent with the likelihood of fresher emissions being found when the winds blew from Mexico City over T1 and T2. The specific absorption at T2 was larger than at T1, which is also consistent with the expectation of more aged particles with encapsulated black carbon being found at the more distant location. In situ measurements of single scattering albedo with an aircraft and a ground station showed general agreement with column-averaged values derived from rotating shadowband radiometer data, although some differences were found that may be related to boundary-layer evolution.« less

Authors:
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Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
950211
Report Number(s):
ANL/EVS/JA-63793
TRN: US200910%%118
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Atmos. Chem. Phys.; Journal Volume: 7; Journal Issue: 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
54 ENVIRONMENTAL SCIENCES; ABSORPTION; AEROSOLS; AIRCRAFT; ALBEDO; ATMOSPHERIC CHEMISTRY; BUILDUP; CARBON; METEOROLOGY; OPTICAL PROPERTIES; PHOTOMETERS; RADAR; RADIOMETERS; SCATTERING; SOOT; SPECTROMETERS; SULFATES; TRANSPORT; URBAN AREAS

Citation Formats

Doran, J. C., Barnard, J. C., Arnold, W. P., Cary, C., Coulter, R., Fast, J. D., Kassianov, E. I., Kleinman, L., Laulainen, N. S., Martin, T., Paredes-Miranda, G., Pekour, M. S., Shaw, W. J, Smith, D. F., Springston, S. R., Yu, X.-Y., Environmental Science Division, PNNL, Desert Reseach Inst., Sunset Lab., Inc., and BNL. The T1-T2 study : evolution of aeorsol properties downwind of Mexico City.. United States: N. p., 2007. Web. doi:10.5194/acp-7-1585-2007.
Doran, J. C., Barnard, J. C., Arnold, W. P., Cary, C., Coulter, R., Fast, J. D., Kassianov, E. I., Kleinman, L., Laulainen, N. S., Martin, T., Paredes-Miranda, G., Pekour, M. S., Shaw, W. J, Smith, D. F., Springston, S. R., Yu, X.-Y., Environmental Science Division, PNNL, Desert Reseach Inst., Sunset Lab., Inc., & BNL. The T1-T2 study : evolution of aeorsol properties downwind of Mexico City.. United States. doi:10.5194/acp-7-1585-2007.
Doran, J. C., Barnard, J. C., Arnold, W. P., Cary, C., Coulter, R., Fast, J. D., Kassianov, E. I., Kleinman, L., Laulainen, N. S., Martin, T., Paredes-Miranda, G., Pekour, M. S., Shaw, W. J, Smith, D. F., Springston, S. R., Yu, X.-Y., Environmental Science Division, PNNL, Desert Reseach Inst., Sunset Lab., Inc., and BNL. Mon . "The T1-T2 study : evolution of aeorsol properties downwind of Mexico City.". United States. doi:10.5194/acp-7-1585-2007.
@article{osti_950211,
title = {The T1-T2 study : evolution of aeorsol properties downwind of Mexico City.},
author = {Doran, J. C. and Barnard, J. C. and Arnold, W. P. and Cary, C. and Coulter, R. and Fast, J. D. and Kassianov, E. I. and Kleinman, L. and Laulainen, N. S. and Martin, T. and Paredes-Miranda, G. and Pekour, M. S. and Shaw, W. J and Smith, D. F. and Springston, S. R. and Yu, X.-Y. and Environmental Science Division and PNNL and Desert Reseach Inst. and Sunset Lab., Inc. and BNL},
abstractNote = {As part of a major atmospheric chemistry and aerosol field program carried out in March 2006, a study was conducted in the area to the north and northeast of Mexico City to investigate the evolution of aerosols and their associated optical properties in the first few hours after their emission. The focus of the T1-T2 aerosol study was to investigate changes in the specific absorption a{sub ABS} (absorption per unit mass, with unit of m{sup 2} g{sup -1}) of black carbon as it aged and became coated with compounds such as sulfate and organic carbon, evolving from an external to an internal mixture. Such evolution has been reported in previous studies. The T1 site was located just to the north of the Mexico City metropolitan area; the T2 site was situated approximately 35 km farther to the northeast. Nephelometers, particle soot absorption photometers, photoacoustic absorption spectrometers, and organic and elemental carbon analyzers were used to measure the optical properties of the aerosols and the carbon concentrations at each of the sites. Radar wind profilers and radiosonde systems helped to characterize the meteorology and to identify periods when transport from Mexico City over T1 and T2 occurred. Organic and elemental carbon concentrations at T1 showed diurnal cycles reflecting the nocturnal and early morning buildup from nearby sources, while concentrations at T2 appeared to be more affected by transport from Mexico City. Specific absorption during transport periods was lower than during other times, consistent with the likelihood of fresher emissions being found when the winds blew from Mexico City over T1 and T2. The specific absorption at T2 was larger than at T1, which is also consistent with the expectation of more aged particles with encapsulated black carbon being found at the more distant location. In situ measurements of single scattering albedo with an aircraft and a ground station showed general agreement with column-averaged values derived from rotating shadowband radiometer data, although some differences were found that may be related to boundary-layer evolution.},
doi = {10.5194/acp-7-1585-2007},
journal = {Atmos. Chem. Phys.},
number = 2007,
volume = 7,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • As part of a major atmospheric chemistry and aerosol field program carried out in March of 2006, a study was conducted in the area to the north and northeast of Mexico City to investigate the evolution of aerosols and their associated optical properties in the first few hours after their emission. The focus of the T1-T2 aerosol study was to investigate changes in the specific absorption αABS (absorption per unit mass, with unit of m2g-1) of black carbon as it aged and became coated with compounds such as sulfate and organic carbon, evolving from an external to an internal mixture.more » Such evolution has been reported in previous studies. The T1 site was located just to the north of the Mexico City metropolitan area; the T2 site was situated approximately 35 km farther to the northeast. Nephelometers, particle soot absorption photometers, photoacoustic absorption photometers, and organic and elemental carbon analyzers were used to measure the optical properties of the aerosols and the carbon concentrations at each of the sites. Radar wind profilers and radiosonde systems helped to characterize the meteorology and to identify periods when transport from Mexico City over T1 and T2 occurred. Organic and elemental carbon concentrations at T1 showed diurnal cycles reflecting the nocturnal and early morning buildup from nearby sources, while concentrations at T2 appeared to be more affected by transport from Mexico City. Specific absorption during transport periods was lower than during other times, consistent with the likelihood of fresher emissions being found when the winds blew from Mexico City over T1 and T2. The specific absorption at T2 was larger than at T1, which is also consistent with the expectation of more aged particles with encapsulated black carbon being found at the more distant location. In situ measurements of single scattering albedo with an aircraft and a ground station showed general agreement with column-averaged values derived from rotating shadowband radiometer data, although some differences were found that may be related to boundary-layer evolution.« less
  • In order to study particulate matter transport and transformation in the Megacity environment, fine particulate carbons were measured simultaneously at two supersites, suburban T1 and rural T2, downwind of Mexico City during the MILAGRO field campaign in March 2006. Organic carbon (OC), element carbon (EC), and total carbon (TC=OC+EC) were determined near real-time by the Sunset semi-continuous field analyzer at both sites. The semi-empirical EC tracer method was used to derive primary organic carbon (POC) and secondary organic carbon (SOC). Diurnal variations of primary and secondary carbons were observed at T1 and T2, which resulted from boundary layer inversion andmore » impacted by local traffic patterns. The majority of organic carbons at T1 and T2 were secondary. The SOC% (SOC%=SOC/TC*100%) at T1 ranged from 1.2 - 100% with an average of 80.7 ± 14.4%. The SOC% at T2 ranged from 12.8 - 100% with an average of 80.1 ± 14.0%. The average EC to PM2.5 percentage (ECPM%=EC/PM2.5*100%)) and OCPM% were 6.0 % and 20.0% over the whole sampling time. The POC to PM percentage (POCPM%) and SOCPM% were 3.7% and 16.3%, respectively. The maximum ECPM% was 21.2%, and the maximum OCPM% was 57.2%. The maximum POCPM% was 12.9%, and the maximum SOC% was 49.7%. The SOC and POC during T1 to T2 transfer favourable meteorological conditions showed similar characteristics, which indicated that transport between the two supersites took place. Strong correlations between EC and carbon monoxide (CO) and odd nitrogens (NO and NOx) were observed at T1. This indicated that EC had proximate sources such as local traffic emissions. The EC/CO ratio derived by linear regression analysis when parameters are in μgC/m3 and μg/m3, respectively, was 0.0045. A strong correlation was also seen between OC and SOC vs. the sum of oxidants such as O3 and NO2 or O3, NO2 and SO2, suggesting the secondary nature of carbons observed at T1.« less
  • One hundred and ten patients with base of tongue tumors less than or equal to 4 cm in diameter (T1 and T2 by the UICC staging system) were treated according to three different methods: surgery followed by external radiation in 27 cases, external radiation followed by interstitial implantation in 29 cases, and external radiation alone in 54 cases. The median follow-up is 8 years with a minimum of 4 years. Local failure occurred twice as often in patients treated by external radiation alone (43%) compared to the other two therapeutic modalities (20.5% for external radiation plus implantation and 18.5% formore » surgery plus radiation). Ninety per cent of recurrences occurred within the first 2 years. The 5-year survival rate for N0 and N1 nodal disease is 30.5% for patients treated by external radiation alone and 50% for the other two methods. This survival difference is related to poorer local control. Surgery plus external radiation gives identical results to those of external radiation and interstitial implantation, but surgery is only practical for peripheral base of tongue tumors and it has poorer functional results. External radiation followed by interstitial implantation is, in our opinion, the best of the three therapeutic techniques for T1 and T2 base of tongue tumors.« less
  • Volatile organic compound (VOC) mixing ratios were measured with two different instruments at the T1 ground site in Mexico City during the Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign in March of 2006. A gas chromatograph with flame ionization detector (GC-FID) quantified 18 light alkanes, alkenes and acetylene while a proton-transfer-reaction ion-trap mass spectrometer (PIT-MS) quantified 12 VOC species including oxygenated VOCs (OVOCs) and aromatics. A GC separation system was used in conjunction with the PIT-MS (GC-PIT-MS) to evaluate PIT-MS measurements and to aid in the identification of unknown VOCs. The VOC measurements are also compared to simultaneousmore » canister samples and to two independent proton-transfer-reaction mass spectrometers (PTR-MS) deployed on a mobile and an airborne platform during MILAGRO. VOC diurnal cycles demonstrate the large influence of vehicle traffic and liquid propane gas (LPG) emissions during the night and photochemical processing during the afternoon. Emission ratios for VOCs and OVOCs relative to CO are derived from early-morning measurements. Average emission ratios for non-oxygenated species relative to CO are on average a factor of {approx}2 higher than measured for US cities. Emission ratios for OVOCs are estimated and compared to literature values the northeastern US and to tunnel studies in California. Positive matrix factorization analysis (PMF) is used to provide insight into VOC sources and processing. Three PMF factors were distinguished by the analysis including the emissions from vehicles, the use of liquid propane gas and the production of secondary VOCs + long-lived species. Emission ratios to CO calculated from the results of PMF analysis are compared to emission ratios calculated directly from measurements. The total PIT-MS signal is summed to estimate the fraction of identified versus unidentified VOC species.« less
  • Magnetic resonance imaging (MRI) has become an essential part of clinical imaging due to its ability to render high soft tissue contrast. Instead of ionizing radiation, MRI use strong magnetic field, radio frequency waves and field gradients to create diagnostic useful images. It can be used to image the anatomy and also functional and physiological activities within the human body. Knowledge of the basic physical principles underlying MRI acquisition is vitally important to successful image production and proper image interpretation. This lecture will give an overview of the spin physics, imaging principle of MRI, the hardware of the MRI scanner,more » and various pulse sequences and their applications. It aims to provide a conceptual foundation to understand the image formation process of a clinical MRI scanner. Learning Objectives: Understand the origin of the MR signal and contrast from the spin physics level. Understand the main hardware components of a MRI scanner and their purposes Understand steps for MR image formation including spatial encoding and image reconstruction Understand the main kinds of MR pulse sequences and their characteristics.« less