Earth Sciences

Exposure of restaurant personnel to environmental tobacco smoke was assessed in 23 restaurants in 2002-2003 after the Finnish Tobacco Act--including restrictions on smoking at bar desks and demands on non-smoking sections--had been extended to restaurants. Air samples were collected using passive samplers from the breathing zone of non-smoking workers during entire work shifts. 3-ethenylpyridine (3-EP) was used as a tobacco-specific vapour-phase marker. The overall median concentration of airborne 3-EP for 97 workers was 1.2 microg/m3, the individual concentrations ranging from <0.06 to 9.4 microg/m3 (n=292). Higher concentrations were measured for staff working in smoking areas or at bar counters than that recorded for those working in non-smoking areas or across different areas. Area samples were collected by passive sampling of 3-EP on organic vapour monitors and by active sampling of 3-EP and nicotine in charcoal tubes. The median concentrations of 3-EP and nicotine were 1.5 microg/m3 (n=292) and 11 microg/m3 (n=92), respectively. In non-smoking areas and at the bar, 3-EP concentrations were 41% and 69% of those measured in smoking areas, with a third of the restaurants having concentrations below 20% in their non-smoking areas. The method applied here--based on diffusive sampling of 3-ethenylpyridine--proved adequate even at low environmental tobacco smoke (ETS) levels. The easy-to-use sampler is thus well suited to detect whether a non-smoking room or area is actually smoke-free or contaminated by smoke drifting from a smoking area. Only a third of the restaurants participating in this study achieved low concentrations of 3-ethenylpyridine in their non-smoking areas. In these cases, the non-smoking area was usually strictly separated from the smoking area. Despite the ban on smoking at bar counters in most restaurants, the drifting smoke was usually a problem if the counter was located in the middle of the smoking area. However, exposure to ETS behind the bar desk was reduced if the counter was located in a non-smoking area.

The hydrogen isotopic composition of plant leaf-wax n-alkanes (δDwax) is a novel proxy for estimating δD of past precipitation (δDp). However, vegetation life-form and relative humidity exert secondary effects on δDwax, preventing quantitative estimates of past δDp. Here, we present an approach for removing the effect of vegetation-type and relative humidity from δDwax and thus for directly estimating past δDp. We test this approach on modern day (late Holocene; 0–3 ka) sediments from a transect of 9 marine cores spanning 21°N–23°S off the western coast of Africa. We estimate vegetation type (C3 tree versus C4 grass) using δ13C of leaf-wax n-alkanes and correct δDwax for vegetation-type with previously-derived apparent fractionation factors for each vegetation type. Late Holocene vegetation-corrected δDwax (δDvc) displays a good fit with modern-day δDp, suggesting that the effects of vegetation type and relative humidity have both been removed and thus that δDvc is a good estimate o...

ABSTRACT The hydrogen isotopic composition of plant leaf-wax n-alkanes (δDwax) is a novel proxy for estimating δD of past precipitation (δDp). However, vegetation life-form and relative humidity exert secondary effects on δDwax, preventing quantitative estimates of past δDp. Here, we present an approach for removing the effect of vegetation-type and relative humidity from δDwax and thus for directly estimating past δDp. We test this approach on modern day (late Holocene; 0–3 ka) sediments from a transect of 9 marine cores spanning 21°N–23°S off the western coast of Africa. We estimate vegetation type (C3 tree versus C4 grass) using δ13C of leaf-wax n-alkanes and correct δDwax for vegetation-type with previously-derived apparent fractionation factors for each vegetation type. Late Holocene vegetation-corrected δDwax (δDvc) displays a good fit with modern-day δDp, suggesting that the effects of vegetation type and relative humidity have both been removed and thus that δDvc is a good estimate of δDp. We find that the magnitude of the effect of C3 tree – C4 grass changes on δDwax is small compared to δDp changes. We go on to estimate δDvc for the mid-Holocene (6–8 ka), the Last Glacial Maximum (LGM; 19–23 ka) and Heinrich Stadial 1 (HS1; 16–18.5 ka). In terms of past hydrological changes, our leaf-wax based estimates of δDp mostly reflect changes in wet season intensity, which is complementary to estimates of wet season length based on leaf-wax δ13C.

ABSTRACT [1] The stable oxygen isotope ratio (δ18O) in precipitation is an integrated tracer of atmospheric processes worldwide. Since the 1990s, an intensive effort has been dedicated to studying precipitation isotopic composition at more than 20 stations in the Tibetan Plateau (TP) located at the convergence of air masses between the westerlies and Indian monsoon. In this paper, we establish a database of precipitation δ18O and use different models to evaluate the climatic controls of precipitation δ18O over the TP. The spatial and temporal patterns of precipitation δ18O and their relationships with temperature and precipitation reveal three distinct domains, respectively associated with the influence of the westerlies (northern TP), Indian monsoon (southern TP), and transition in between. Precipitation δ18O in the monsoon domain experiences an abrupt decrease in May and most depletion in August, attributable to the shifting moisture origin between Bay of Bengal (BOB) and southern Indian Ocean. High-resolution atmospheric models capture the spatial and temporal patterns of precipitation δ18O and their relationships with moisture transport from the westerlies and Indian monsoon. Only in the westerlies domain are atmospheric models able to represent the relationships between climate and precipitation δ18O. More significant temperature effect exists when either the westerlies or Indian monsoon is the sole dominant atmospheric process. The observed and simulated altitude-δ18O relationships strongly depend on the season and the domain (Indian monsoon or westerlies). Our results have crucial implications for the interpretation of paleoclimate records and for the application of atmospheric simulations to quantifying paleoclimate and paleo-elevation changes.

While natural marine habitats with motion capabilities, e.g., kelps and seaweeds, have been studied alongside their associated fouling communities, little is known of the effect of motion on the communities of floating artificial habitats such as buoys, rafts, and pontoons, particularly in tropical systems. Hydrodynamic features greatly differ between floating and fixed artificial substrata, which in turn affect the structure of their associated communities. This study tested the hypothesis that floating and fixed artificial installations in a tropical reef system (Eilat, Red Sea) would support different benthic communities throughout space and time. Specifically, we examined differences in communities recruited onto settlement plates between floating and fixed installations deployed at three different sites, along a two-year monitoring period. The three sites exhibited distinct differences in species assemblages between the monitoring dates (6, 12, 18 and 24 months post deployment), mainly between the first and the last two dates. The average level of dissimilarity between floating and fixed installations increased over time at all sites. Over 50% of the dissimilarity between the floating and fixed installations resulted from five taxonomic groups i.e., bryozoans, bivalves, barnacles, sponges, including the amount of bare space on the settlement plates. The contribution of these groups to the dissimilarity changed both temporally within each site, and spatially among sites. The observed differences were related to the hydrodynamic characteristics of floating and fixed habitats, interacting with biotic features such as predation, successional processes and seasonality; and abiotic features including small-scale spatial changes, light, and position in the water column.