Abstract. We have investigated methane emissions from urban sources in the former East Germany using innovative measurement techniques including a mobile real-time methane instrument and tracer release experiments. Anthropogenic and biogenic sources were studied with the emphasis on methane emissions from gas system sources, including urban distribution facilities and a production plant. Methane fluxes from pressure regulating stations ranged from 0.006 to 24. l/min. Emissions from diffuse sources in urban areas were also measured with concentration maps and whole city flux experiments. The area ftuxes of the two towns studied were 0.37 and 1.9 IJgjm 2 ts. The emissions from individual gas system stations and total town emissions of this study are comparable to results of similar sites examined in the United States.
Rate constants for the gas-phase reaction of NO3 radicals with 1 -butene, trans-butene, 2-methyl-2-butene and 2.3-dimethyl-2-butene have been obtained in a flow system at 298i2 K and a pressure of 3 mbar He using NO3 LIF measurements. NO3 radicals were produced via thermal decomposition of N205 at ca. 400 K, i.e.Applying pseudo-first-order conditions, the rate constants for 1 -butene and trans-butene were found to be ( I .04*0.1 I). I O-I4 and (3.74i0.45).respectively. For 2-methyl-2-butene and 2,3-dimethyl-2-butene the rate constants were obtained under second-order conditions to be (1.03+0.09)~10-" and (5.49a0.42).10-", respectively (unit: cm3 molecule-' s-').N20s+M + N03+N02+M.
Abstract.Boundary layer trace gas and particulate extinction measurements in the wavelength region from 320nm to 680nm have been performed by means of a differential optical absorption spectroscopy (DOAS) system at Cape Arkona (Island Rfigen/Germany). The wavelength-dependent extinction coefficient ere(A) is determined from the attenuation of radiation along two paths of different lengths. Nearly simultaneous recording of the concentrations of Oa and NO2 within the same air mass allows a correction of their contribution to ere(A). The extinction coefficients are compared with volume scattering coefficients measured by an open integrating nephelometer. Differences between the measurements can be attributed to atmospheric inhomo. geneities. A simplified model involving monomodal log-normal distributions is applied to approximate the total particle surface area concentration and an upper limit of the accumulation mode radius. This allows a rough estimate of the particle number concentration. During the summer of 1995 the mean (median) surface area concentration was about 350 (250)ttm2/cm 3, and the particle number concentration ranged from about 100 cm -3 to some 1000 cm-3.
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