E. Brüggemann

Mixing state of elemental carbon and non-light-absorbing aerosol components derived from in situ particle optical properties at Xinken in Pearl River Delta of China

Received 29 November 2005; revised 28 April 2006; accepted 5 June 2006; published 21 October 2006. [1] The aerosol mixing state was investigated with an optical closure study at Xinken, Pearl River Delta of China in 2004. On the basis of in situ aerosol microphysical and chemical measurements and a two-component aerosol optical model an internal consistency algorithm was developed to model the mass ratio (r) of externally mixed elemental carbon (EC) to total EC, which minimized the discrepancies between measured and calculated optical properties. The rest of EC was assumed to be internally mixed. A time series of r was retrieved. Good agreement between model and observation was found, on the order of ±15% for total/back scattering coefficients and ±10% for absorption coefficient. The EC mixing state was strongly dependent on the local wind patterns. When north/northeasterly winds prevailed, the air came from the urban and industrial areas of mainland China, and EC was mainly externally mixed with an average r of 85 ± 12%. When the airflow was controlled by a weak local wind system, the mixing state showed a pronounced diurnal variation. During daytime the wind speed was nearly zero. This favored the increase of local pollution, and the average r was about 95%. However, during nighttime the EC mixing state transformed to be internally mixed apparently with an average r of 53 ± 15%, which can be explained by a more aged air mass. The south/ southeasterlywindscomingfromtheseawerefoundtohavethemostimportanteffectonthe transformation of EC mixing state in the night, but fairly rapid local aging processing was also observed. The uncertainties of the model were explored by a Monte Carlo simulation.

Performance of an Aerodyne Aerosol Mass Spectrometer (AMS) during Intensive Campaigns in China in the Summer of 2006

An Aerodyne quadrupole aerosol mass spectrometer (AMS) was deployed in China in the summer of 2006. The measurements were made in the Pearl River Delta region in July 2006 (PRD campaign) and also in Beijing in August–September 2006 (CAREBEIJING campaign). The AMS successfully measured size-resolved chemical composition of submicron non-refractory aerosol (vaporized at 600°C in vacuum) with a time resolution of 10 min, although some quantification issues have been identified. We observed extremely large signals at m/z 39 ( 39 K + ) and 41 (41K + ), which significantly exceeded m/z 28 (N + 2 ) signals. We also found large signals of m/z 85 ( 85 Rb + ), 87 (87Rb + ), and 133 (Cs + ). Laboratory experiments suggest that the large enhancement of K + could have been due to the presence of K-containing particles in ambient air. The interferences of alkali metals at m/z 41, 85, 87, and 133 were significant and need to be corrected for better quantification of organic aerosol. The AMS measurements are compared with other, collocated measurements: a particle-into-liquid sampler combined with an ion chromatograph (PILS-IC), a Sunset Laboratory semi-continuous carbonaceous aerosol analyzer, and a Berner impactor sampler followed by off-line ion chromatography analysis (for major inorganic ions). We have found good agreement between the AMS and the other instruments when we assume an AMS particle collection efficiency (CE) of 0.5 for the PRD data and CE = 1.0 for the CAREBEIJING data. These results suggest that the AMS CE could be significantly different in different locations. Possible factors affecting the variability in the CE values are discussed.

Trends of pollution in rain over East Germany caused by changing emissions

Large changes in emissions also cause a significant change in pollutant concentrations in rain water. The influence of these changes on pollutant concentrations in rain water and wet deposition were investigated in different regions and time periods from 1983 to 1999 in East Germany. Initially, this period is characterized by large emissions of SO2(about 5400 kt a−1), NOx(about 750 kt a−1), and dust (about 2000 kt a−1) at the end of the 1980s. After the reunification of Germany in 1990 and restructuring of industry and agriculture, emissions drastically decreased. For example, from 1990 to 1998 in Saxony emissions of SO2, NOx and dust decreased by 84, 44 and 97%, respectively. Alkaline components also strongly decreased through efficient dust removal, while no desulphurization was used in flue gases of power and heating plants. As a consequence, the mean acidity of precipitation strongly rose by a factor of three from before 1990 up to 1995 (the mean pH value in 1995 was about 3.9, with minimum values down to 3.6). In 1996 desulphurization techniques were established in power plants and resulted in an increase of pH values to the level in the period from 1983 to 1989/1990. The results for ionic composition (Cl−, NO3−, SO42−, Na+, NH4+, K+, Ca2+, and Mg2+, the pH value (acidity), and conductivity) are based on precipitation samples collected in periods > 4 h. The data were classified with backward trajectories and entry sectors which are characterized by similar emissions and/or geographical regions.

Measured profiles of aerosol particle absorption and its influence on clear‐sky solar radiative forcing

Using a particle/soot absorption photometer (PSAP), airborne measurements of aerosol volume absorption coefficients were done in differently polluted air masses over a rural area in Germany under cloudless conditions in December 1997. Together with measurements of aerosol particle size distribution, particle chemical composition, and meteorological parameters, the PSAP-measurements were used (1) to estimate vertical profiles of black carbon (BC) volume fraction and (2) to quantify the influence of particle absorption on solar radiative transfer by calculating their solar radiative forcing at the top of the atmosphere (TOA). Three case studies with different levels of absorption were investigated in detail. The vertical profiles of the volume absorption coefficient showed maximum values close to the ground (>6×10−5 m−1 in the most absorbing case) and a strong drop-off toward higher altitudes. The estimated BC volume fractions were typically largest near the ground and decreased rapidly with increasing altitude. Radiative transfer calculations were carried out with and without consideration of the measured absorption of the particles. In the polluted cases and assuming a low surface albedo, the negative TOA solar radiative forcing of the aerosol particles decreased significantly when the measured particle absorption profiles were included in the calculations. Assuming a snow-covered ground in these cases, the aerosol forcing changed from a cooling without aerosol particle absorption into a heating if the measured absorption of the particles was considered. An investigation of the forcing dependence on the solar zenith angle showed an increasing influence of the particle absorption for higher sun elevations.

A new method to study aerosol source contributions along the tracks of air parcels and its application to the near-ground level aerosol chemical composition in central Europe

Abstract A novel method is presented to reveal the significance and contribution of source types and characteristic formation times for individual aerosol constituents: Backward trajectory analyses are used to allocate time-resolved information about residence time of air masses over different types of ground surfaces. The correlations between the residence time of air mass over individual ground surface types and aerosol constituent concentrations (or particulate matter mass fractions) are investigated by a time-weighting method. The correlation coefficients between the concentrations of individual aerosol constituents and the residence times of air masses over certain types of ground surfaces at a certain time difference to arrival time were used to compose time profiles. These are suggested to reflect the time-resolved ground emissions’ influence on aerosol composition, which is particularly relevant for secondary aerosol constituents. The method has been applied to aerosol chemical composition data from various seasons and from rural and urban sites in Germany. For various ground types, we obtain correlations between weighted (and normalized) residence times (‘source loadings’) on one hand and the abundances of trace constituents known as markers for marine (Na, Cl), continental-rural (e.g. mineral dust components) and industrial sources (e.g., organic and elemental C, As, Pb) on the other hand. The occurrence of super-μm particulate NO 3 − in central Europe is found to originate largely in the marginal seas. The time profiles indicate that the characteristic formation time of the secondary aerosol is 48– 72 h , while the coarse mode particulate matter including some heavy metals was determined by emissions h back. The occurrence of particulate elemental carbon was temporally bimodal with regard to the elapsed time since emission (maxima at Δ t≈60 h and Δ t =12– 24 h ), which indicates the presence of two types undergoing a selection process during aging. The factors which explained most of the variability of the aerosol chemical composition were the season and the type of ground surface in contact with the air mass during its transport. More immediate influences on the samples, such as the weather conditions during sampling and the type of site (rural or urban) were distinctly less significant.

Atmospheric research program for studying changing emission patterns after German unification

Abstract A dramatic decrease in emission of sulphur dioxide (SO 2 , 60%), dust (82%), nitrogen oxide (NO, 30%) and other pollutants (hydrochloric acid (HCl); ammonia (NH 3 )) has been observed in East Germany after German unification in 1989. The smaller decrease in total NO is due to significant increase of NO from traffic. Air-pollutant concentrations in both parts of Germany before and after 1989 will be compared and their development will be discussed, based on precipitation and cloud chemistry data from long-term continuous record. Sectoral rain data, based on backward trajectory calculations, clearly show that the significant decline in annual volume weighted precipitation ions (sulphate, calcium, ammonium, chloride) in rain water from sector “East” since 1989 and particularly since about 1992 is roughly correlated with a similar percentage decline in SO 2 , dust and NH 3 emissions for the region East Germany. The acidity of the precipitation from sector “East” has increased very strikingly from 1993 up to 1995 threefold more than from sector “West”. Despite the strong decrease in SO 2 emission, this decrease of the atmospheric neutralising capacity was caused by the much steeper decline in atmospheric base cations in that region. Precipitation data from all transport directions show high variation, but no significant trend in the annual average H + ion concentration. At Mt. Brocken the annual average volume weighted cloud-water acidity during frost-free periods increased by a factor of three between 1992 and 1995. This result, confirmed also by the annual frequency distributions of the pH values, reflects the atmospheric pollutant loading also from all entry sectors. After 1995 this trend is reversed. Detailed classification of the cloud-water data by entry sector, and by meteorological and especially microphysical factors is currently being carried out and preliminary results are presented.

Size-resolved aerosol characterization for a polluted episode at the IfT research station Melpitz in autumn 1997

Inorganic ions, organic carbon (OC), elemental carbon (EC) and a variety of organic single species in airborne particles have been determined at the research station of the Leibniz – Institut für Troposphärenforschung (IfT) in Melpitz (Germany) in autumn 1997.Samples of eight selected measurement events were divided in two groups in order to investigate differences in the chemical composition of particles originating from southwesterly (SW – developed EU countries) or from easterly directions (E – less developed eastern countries). Differences between these two groups were tested statistically by Students t-test.Five stage cascade impactor samples show nitrate as most abundant in the accumulation mode in the SW group. EC and sulphate show the most abundant mass fractions in the E group. That can be considered as a consequence of domestic coal heating and coal-fired power plant emissions in the region of westerly Poland, northern Czech Republic and easterly Germany. Higher nitrate concentrations in the SW group can be explained by stronger NOx emissions caused by the leeward plume of the conurbation of Leipzig, as well as by the still higher traffic density in western Germany.The methane sulphonic acid (MSA) mass fraction was higher for SW air masses in accumulation mode particles, probably indicating marine origin. Succinic acid also showed higher mass fractions for the SW group. This could be caused by primary emission in automobile exhaust gases and photochemical formation during transport from SW. Indeed, during SW sampling, solar radiation intensity was higher than during E sampling.The observed differences in the particle composition are an expression of the still existing technology gradient in Europe. Future campaigns could show the development to a joint economy with smaller differences in anthropogenic emissions.

Long-term trends in chemistry of precipitation after longscale transport : Effects of atmospheric rehabilitation in East Germany

Components in precipitation are dominantly dependent on structure and quantity of emissions on the course of the rainy air masses. It can be proved after meso-and long-range transport. Starting in 1982, precipitation is collected in 4-hour-periods at sites far from industry in East-Germany. For regions with specific geographical or uniform emission features arrival sectors are established, e. g. former GDR, Scandinavia, Poland, or Czech. The classification of the samples is done by back-trajectories. From the former GDR the anthropogenical components were most significantly raised before the political change, but acidity remained on an average level. After the change, the most emission products decline considerably —except NOX. Consequently, those lead to essential changes of pollutants in precipitation. The reduction is not uniformly.The report represents long-term data and discusses clear differences between components in deposition from sectors of the former GDR and West-Germany. The effects of atmospheric rehabilitation are analysed.Specially starting in 1993 the acidity of rain from the former GDR increases very strikingly up to now threefold more than from West-Germany (average ≤pH 4 at some sites). An explanation in terms of emission components only is devious, a complex consideration of change of dust composition as neutralizing factors and of processes of cloud formation and dispersal is necessary. It must be mentioned, that the acidity of precipitation from West-Germany and Scandinavia declines slightly in recent period. Therefore only sector-classified data show the real range of acidity.

On the Horizontal Homogeneity of Mass-Related Aerosol Properties

We studied the mass-related aerosol properties, simultaneously attwo sites at the urban roof top level in the same city. Nosystematic influence of the wind vector on the difference in theaerosol concentrations between the two locations could be found.These results are compared with results from a second, similarexperiment over a larger distance including one urban and onerural site. Surprisingly, we could not detect a tendency whichwould indicate that sampling air at distance in the order of 1 kmwould be less affected by the heterogeneity than samplingdistanced in the order of 10 km apart. On the contrary, theresults suggest that mass-related properties at two sites in thesame city are not necessarily more similar than at an urban and arural site outside the city. These results stress the limitedhorizontal homogeneity of urban atmospheric aerosol. As aconclusion it is suggested that single-site measurements of mass-related aerosol properties should be considered to berepresentative for an area smaller than 1 km2 on size.

Bestimmung von Spurenstoffen in Niederschlagsproben

ZusammenfassungIm Rahmen des Verbundforschungsprojekts SANA wurde ein Niederschlags-Meßnetz auf dem Gebiet der Neuen Bundesländer aufgebaut, um die Auswirkungen der durch Strukturveränderungen in der Industrie, dem Verkehr und der Landwirtschaft auftretenden Emissionsveränderungen auf die nasse Deposition von Luftschadstoffen zu untersuchen.Es werden erste Meßergebnisse des Jahres 1992 und aus langjährigen Meßreihen sichtbar werdende Trends dargestellt.AbstractA precipitation network consisting of 15 sites as part of the national project SANA was established to document and characterize the spatial and temporal changes of pollutants in the precipitation of East Germany. Long-term data records show a significant decrease of sulfate and calcium in the precipitation.The acidity and the nitrogen-containing ions have been remained unchanged up to now.