Bruce Gandrud, another Scientist from Droplet Measurement Technologies, adds: “Until recently, photoacoustic instruments had to be custom built and have generally been available only for intensive field and laboratory campaigns. However, we are now able to make this technology accessible to a wider group of users, including monitoring, where accurate measurements of black carbon will be crucial to any efforts to regulate the particles from a climate change perspective.


“In addition, the photoacoustic measurement of light absorption is the fundamental property relevant to black carbon climate forcing. The PAX instrument also measures light scattering by particles, which provides an additional check on particulate mass measurements and together with absorption provides information required to determine aerosol optical properties relevant for climate forcing.”


PAX – technical specifications


Enviro Technology is now supplying the PAX system, the world’s most advanced black carbon monitoring equipment. The fact that it is sensitive and provides a highly accurate, speedy, high- resolution measurement means that it is ideal for use in a range of measurement applications including air quality and visibility,


atmosphere & climate, health effects, combustion source emissions and biomass burning.


It is suitable for fixed site, mobile or airborne sampling and the technical specification includes:


• Direct in-situ measurement of light absorption and scattering in a single instrument


• Absorption measurement correlates to black carbon mass concentration


• Reciprocal nephelometry provides excellent scattering coefficient sensitivity


• Choice of wavelengths: 870 nm (standard); optional 405 nm, 532 nm or 781 nm


• Fast response, one-second resolution, real-time data display


• Wide dynamic range suitable for pristine regions to source sampling


• Continuous and autonomous operation


• High-resolution touch screen display for real-time data and instrument status


• No filter collection required - no filter data artefacts


UK Focus - Air Monitoring A tale of two cities


vii


The deployment of PAX black carbon monitors has led to a better understanding of pollution in Los Angeles and Mexico City.


The equipment has been used to deliver a more accurate picture of daily Black Carbon trends in these two similarly densely- populated cities.


Monitors in the two cities demonstrated quite different weekend and weekday trends. Los Angeles had higher concentrations on weekends, whereas Mexico City had much higher concentrations during the week. Overall, Mexico City’s daily peak values were double those of Los Angeles, but hourly maximum values were similar, reaching almost 10µg m-3


.


The differences can be clearly attributed to contrasts in meteorology and traffic patterns, particularly wind patterns and the percentage of diesel-burning vehicles on the road.


This tale of two cities has important implications for the understanding of the monitoring of black carbon levels and highlights the effectiveness of photoacoustic technology for accurate measurements.


All of our articles are online! To view and download them, visit: www.envirotech-online.com


FTIR Analyser Reveals Surprising Solution


Emissions analysers have to be checked annually by certified testers and during recent functionality tests for a Gasmet FTIR continuous emissions monitor (CEM) at a UK Energy from Waste plant, the Nitrogen Dioxide span check results were found to be incorrect. A subsequent investigation revealed surprising results that would not have been apparent had the plant been using traditional CEMs. NO2 values should have been 76mg/m3 but the FTIR was reading 31mg/m3


, so Dominic Duggan from Quantitech (UK), the company which installed the monitor, was contacted to investigate.


As a multigas monitoring technology, FTIR provides a complete analysis spectrum from the sample gas and as a result it was possible to investigate the response peaks for NO2 in addition to any other gases present. Duggan’s investigation showed peaks for NO2 and also found peaks for NO and HCl. In addition he found an unknown peak at 1750-1850 cm-1 in the sample spectrum.


The investigators speculated that there may be a problem with the regulator, which had previously been used to deliver HCl test gas and a quick piece of internet research revealed that Nitrosyl Chloride (NOCl) can be formed if NO2 and HCl are mixed. This gas is a decomposition product of Aqua Regia and was found to be responsible for the ‘unknown’ peak.


Aqua Regia (a mixture of Nitric and Hydrochloric acids) is so-called because it is able to dissolve royal or noble metals such as gold. Aqua regia is a highly corrosive chemical, so it is important to avoid its generation. A clean regulator was therefore fitted to the CEM and subsequent analysis showed the correct result for NO2.


Dominic Duggan says “The main advantage of FTIR is that it provides continuous analytical data for an almost endless list of chemicals. Most CEMs are configured to monitor up to 50 parameters, the most


common configurations include H2O, CO2, CO, SO2, NO, NO2, N2O, HCl, HF and NH3, however, it is also a simple and low cost process to add further parameters at a


later date, which means that the monitoring regime is ‘future proof’.


“This investigation highlights a further advantage of FTIR; if traditional single parameter analysers, such as chemiluminescence or NDIR, had been in place, the logical conclusion would have been to blame the analyser for reading incorrectly, resulting in a costly exercise to have it replaced. But the FTIR enabled us to study the complete spectrum and quickly identify and resolve the problem.”


Reader Reply Card No. 163


New Gas Analyser Rental Website Launched


Signal Group(UK) is very excited to have launched their all new rental website with full on-line booking facilities. Utilising the very latest web technology, this site is a cut above the rest.


Signal have been supplying rental gas analysers and accessories for a few years now but they've just moved forward another step by launching a fully interactive rental website. Customers can see what's available and then place their booking directly on-line. An email confirmation is sent on receipt of the booking and the system keeps them updated every step of the way. For a look at all the features just go to www.signal-rental.com.


Signal Group is one of the largest UK manufacturers of source emissions test equipment. They provide a wide range of gas analysers, systems and sample handling components for every kind of industry and application.


Reader Reply Card No. 164 Reader Reply Card No. www.envirotech-online.com 165 IET November / December 2012


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60