A Mobile Laboratory for Measuring Greenhouse Gases and Gaseous Pollutants in Urban Airsheds

Traffic emissions are a significant source of greenhouse gases and air pollutants in urban areas. In this study, we describe a mobile laboratory for measuring these atmospheric species. The instruments are installed in a large van modified with shock absorbing instrument racks. They include ultraportable greenhouse gas analyzers for CH4 and CO2 (model UGGA, Los Gatos Research, Mountain View, CA, USA), a 13C-CO2 analyzer (model G1101-i, Picarro Inc., CA, USA), a N2O/CO analyzer (Los Gatos Research, Mountain View, CA, USA) and a suite of instrument for monitoring criteria pollutants (CEMS, Thermo Fisher Scientific Inc., MA, USA). These instruments are housed in a temperature controlled compartment and powered by an onboard generator. We tested the laboratory in a traffic tunnel and in several main streets in Nanjing, China. The CH4 to CO2 emissions ratio observed in the tunnel was in agreement with the IPCC inventory estimates but was much lower than the emissions ratio obtained in the streets where natural gas-powered taxis were more abundant than in the tunnel.