Fossil versus contemporary sources of fine elemental and organic carbonaceous particulate matter during the DAURE campaign in Northeast Spain

We present results from the international field campaign DAURE (Detn. of the sources of atm. Aerosols in Urban and Rural Environments in the Western Mediterranean), with the objective of apportioning the sources of fine carbonaceous aerosols. Submicron fine particulate matter (PM1) samples were collected during Feb.-March 2009 and July 2009 at an urban background site in Barcelona (BCN) and at a forested regional background site in Montseny (MSY). We present radiocarbon (14C) anal. for elemental and org. carbon (EC and OC) and source apportionment for these data. We combine the results with those from component anal. of aerosol mass spectrometer (AMS) measurements, and compare to levoglucosan-based ests. of biomass burning OC, source apportionment of filter data with inorg. compn. + EC + OC, submicron bulk potassium (K) concns., and gaseous acetonitrile concns. At BCN, 87 % and 91 % of the EC on av., in winter and summer, resp., had a fossil origin, whereas at MSY these fractions were 66 % and 79 %. The contribution of fossil sources to org. carbon (OC) at BCN was 40 % and 48 %, in winter and summer, resp., and 31 % and 25 % at MSY. The combination of results obtained using the 14C technique, AMS data, and the correlations between fossil OC and fossil EC imply that the fossil OC at Barcelona is ∼47 % primary whereas at MSY the fossil OC is mainly secondary (∼85 %). Day-to-day variation in total carbonaceous aerosol loading and the relative contributions of different sources predominantly depended on the meteorol. transport conditions. The estd. biogenic secondary OC at MSY only increased by ∼40 % compared to the order-of-magnitude increase obsd. for biogenic volatile org. compds. (VOCs) between winter and summer, which highlights the uncertainties in the estn. of that component. Biomass burning contributions estd. using the 14C technique ranged from similar to slightly higher than when estd. using other techniques, and the different estns. were highly or moderately correlated. Differences can be explained by the contribution of secondary org. matter (not included in the primary biomass burning source ests.), and/or by an over-estn. of the biomass burning OC contribution by the 14C technique if the estd. biomass burning EC/OC ratio used for the calcns. is too high for this region. Acetonitrile concns. correlate well with the biomass burning EC detd. by 14C. K is a noisy tracer for biomass burning. [on SciFinder(R)]

The Rasikajy civilization in northeast Madagascar: a pre-European Chinese community?

Archaeological excavations in northern Madagascar during the first half of the 20th century have revealed the presence of a former prosperous civilisation known as the Rasikajy civilisation. Little is known about the origin of this civilisation and how and when they first arrived in Madagascar. The most striking evidence for the Rasikajy civilisation comes from excavations at a necropolis in Vohemar located along the northeast coast, where more than 600 tombs containing spectacular objects were unearthed in the 1940s (Vernier & Millot 1971). The findings in the tombs included, amongst others, Chinese ceramics, silver and gold jewellery, iron weapons, glassware, bronze mirrors and chlorite-schist objects (ibid.). The latter objects were produced from chlorite schist mined at quarries in northern and eastern Madagascar and there is evidence that jewellery and iron objects were also produced by the Rasikajy from locally available raw material. Chlorite-schist objects have not only been found in coastal sites in Madagascar, but also in the Comores and eastern Africa suggesting an active engagement of the Rasikajy in western Indian Ocean trade. Our re-evaluation of published literature on archaeological sites in northern Madagascar indicates that the majority of Chinese ceramics found in the tombs at Vohemar dates from the 15th and first half of the 16th century with some dating back to the 14th century or earlier. Our comparative analysis of burial objects at Vohemar shows that locally produced chlorite-schist tripod vessels exhibit remarkable resemblances to ancient Chinese bronze ritual tripod vessels. The objects encountered in the tombs and their positions with respect to the body indicate that the Rasikajy practiced burial rites similar to those practised in the past in China. Our re-evaluation of the literature suggests that communities with Chinese roots were present in northeastern Madagascar prior to the arrival of the first Europeans in 1500 and participated in the Indian Ocean trade network. The demise of the Rasikajy civilisation seems to have occurred in the second half of the 16th century when production of chlorite-schist objects ceased. It is still unclear why this occurred.

Fossil and Nonfossil Sources of Organic and Elemental Carbon Aerosols in the Outflow from Northeast China

Source quantification of carbonaceous aerosols in the Chinese outflow regions still remains uncertain despite their high mass concentrations. Here, we unambiguously quantified fossil and nonfossil contributions to elemental carbon (EC) and organic carbon (OC) of total suspended particles (TSP) from a regional receptor site in the outflow of Northeast China using radiocarbon measurement. OC and EC concentrations were lower in summer, representing mainly marine air, than in other seasons, when air masses mostly traveled over continental regions in Mongolia and northeast China. The annual-mean contribution from fossil-fuel combustion to EC was 76 ± 11% (0.1−1.3 μg m−3). The remaining 24 ± 11% (0.03−0.42 μg m−3) was attributed to biomass burning, with slightly higher contribution in the cold period (∼31%) compared to the warm period (∼21%) because of enhanced emissions from regional biomass combustion sources in China. OC was generally dominated by nonfossil sources, with an annual average of 66 ± 11% (0.5−2.8 μg m−3), approximately half of which was apportioned to primary biomass burning sources (34 ± 6%). In winter, OC almost equally originated from primary OC (POC) emissions and secondary OC (SOC) formation from fossil fuel and biomass-burning sources. In contrast, summertime OC was dominated by primary biogenic emissions as well as secondary production from biogenic and biomass-burning sources, but fossil-derived SOC was the smallest contributor. Distinction of POC and SOC was performed using primary POC-to-EC emission ratios separated for fossil and nonfossil emissions.