Field Sampling Campaigns Research Articles

Anaerobic microorganisms in astrobiological analogue environments: from field site to culture collection

AbstractAstrobiology seeks to understand the limits of life and to determine the physiology of organisms in order to better assess the habitability of other worlds. To successfully achieve these goals we require microorganisms from environments on Earth that approximate to extraterrestrial environments in terms of physical and/or chemical conditions. The most challenging of these environments with respect to sample collection, isolation and cultivation of microorganisms are anoxic environments. In this paper, an approach to this challenge was implemented within the European Union's MASE (Mars Analogues for Space Exploration) project. In this review paper, we aim to provide a set of methods for future field work and sampling campaigns. A number of anoxic environment based on characteristics that make them analogous to past and present locations on Mars were selected. They included anoxic sulphur-rich springs (Germany), the salt-rich Boulby Mine (UK), a lake in a basaltic context (Iceland), acidic sediments in the Rio Tinto (Spain), glacier samples (Austria) and permafrost samples (Russia and Canada). Samples were collected under strict anoxic conditions to be used for cultivation and genomic community analysis. Using the samples, a culturing approach was implemented to enrich anaerobic organisms using a defined medium that would allow for organisms to be grown under identical conditions in future physiological comparisons. Anaerobic microorganisms were isolated and deposited with the DSMZ (Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH) culture collection to make them available to other scientists. In MASE, the selected organisms are studied with respect to survival and growth under Mars relevant stresses. They are artificially fossilized and the resulting biosignatures studied and used to investigate the efficacy of life detection instrumentation for planetary missions. Some of the organisms belong to genera with medical and environmental importance such asYersiniaspp., illustrating how astrobiology field research can be used to increase the availability of microbial isolates for applied terrestrial purposes.

Quantitative cancer risk assessment and local mortality burden for ambient air pollution in an eastern Mediterranean City.

Health risks posed by ambient air pollutants to the urban Lebanese population have not been well characterized. The aim of this study is to assess cancer risk and mortality burden of non-methane hydrocarbons (NMHCs) and particulates (PM) based on two field-sampling campaigns conducted during summer and winter seasons in Beirut. Seventy NMHCs were analyzed by TD-GC-FID. PM2.5 elemental carbon (EC) components were examined using a Lab OC-EC aerosol Analyzer, and polycyclic aromatic hydrocarbons were analyzed by GC-MS. The US EPA fraction-based approach was used to assess non-cancer hazard and cancer risk for the hydrocarbon mixture, and the UK Committee on Medical Effects of Air Pollutants (COMEAP) guidelines were followed to determine the PM2.5 attributable mortality burden. The average cumulative cancer risk exceeded the US EPA acceptable level (10-6) by 40-fold in the summer and 30-fold in the winter. Benzene was found to be the highest contributor to cancer risk (39-43%), followed by 1,3-butadiene (25-29%), both originating from traffic gasoline evaporation and combustion. The EC attributable average mortality fraction was 7.8-10%, while the average attributable number of deaths (AD) and years of life lost (YLL) were found to be 257-327 and 3086-3923, respectively. Our findings provide a baseline for future air monitoring programs, and for interventions aiming at reducing cancer risk in this population.

Atmospheric aerosol compositions and sources at two national background sites in northern and southern China

Abstract. Although China's severe air pollution has become a focus in the field of atmospheric chemistry and the mechanisms of urban air pollution there have been researched extensively, few field sampling campaigns have been conducted at remote background sites in China, where air pollution characteristics on a larger scale are highlighted. In this study, an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS), together with an Aethalometer, was deployed at two of China's national background sites in northern (Lake Hongze site; 33.23° N, 118.33° E; altitude 21 m) and southern (Mount Wuzhi site; 18.84° N, 109.49° E; altitude 958 m) China in the spring seasons in 2011 and 2015, respectively, in order to characterize submicron aerosol composition and sources. The campaign-average PM1 concentration was 36.8 ± 19.8 µg m−3 at the northern China background (NCB) site, which was far higher than that at the southern China background (SCB) site (10.9 ± 7.8 µg m−3). Organic aerosol (OA) (27.2 %), nitrate (26.7 %), and sulfate (22.0 %) contributed the most to the PM1 mass at NCB, while OA (43.5 %) and sulfate (30.5 %) were the most abundant components of the PM1 mass at SCB, where nitrate only constituted a small fraction (4.7 %) and might have contained a significant amount of organic nitrates (5–11 %). The aerosol size distributions and organic aerosol elemental compositions all indicated very aged aerosol particles at both sites. The OA at SCB was more oxidized with a higher average oxygen to carbon (O ∕ C) ratio (0.98) than that at NCB (0.67). Positive matrix factorization (PMF) analysis was used to classify OA into three components, including a hydrocarbon-like component (HOA, attributed to fossil fuel combustion) and two oxygenated components (OOA1 and OOA2, attributed to secondary organic aerosols from different source areas) at NCB. PMF analysis at SCB identified a semi-volatile oxygenated component (SV-OOA) and a low-volatility oxygenated component (LV-OOA), both of which were found to be secondary species and could be formed from precursors co-emitted with BC. Using the total potential source contribution function model, the likely source areas of the major PM1 components at both sites were a on large regional scale in East Asia. The possible sources may include not only emissions from the Chinese mainland but also emissions from ocean-going cargo ships and biomass burning in neighboring countries.

Oxygen transport and reactivity within a sandy seepage face in a mesotidal lagoon (Ria Formosa, Southwestern Iberia)

Sandy sediments are now recognized as sites of high carbon turnover enhanced by porewater flow. However, it is unclear how coupling between porewater advection and benthic metabolism might permit O2-saturated areas and suboxic environments to coexist in close proximity. Field sampling campaigns, flow-through reactor (FTR) experiments and diagenetic modeling were used to study benthic O2 dynamics in surface sediments of a permeable intertidal seepage face (Ria Formosa; Southwestern Iberia). Field results demonstrated that the pressure gradient imposed by tidal oscillation at the seepage face permits seawater infiltration at high tide, and hence resupplies the benthos in O2 and organic matter (OM). Significant aerobic respiration rates (12.1–26.8 nmol cm−3 “bulk sediment” (bs) h−1) were derived from vertical O2 gradients taken from the top 28 cm of the sediment during active seepage. FTR experiments showed a vertical zonation of respiration rates following benthic OM availability (from 8.63 ± 1.88 nmol cm−3 bs h−1 at 12–32 cm depth to 53.55 ± 7.93 nmol cm−3 bs h−1 at 0–2 cm depth). Advection enhances O2 consumption rates, but respiration is ultimately limited by OM availability at high seepage rates. Diagenetic modeling of O2 distribution in the porewater suggests that even within a well-oxygenated beach aquifer, local respiration is sufficiently high to lower the porewater O2 concentration near the sediment surface during active seepage. Our results indicate that high seepage rates, OM and O2 loading promoted by tidally-driven seawater infiltration control the O2 consumption at the sediment surface, thus favoring the occurrence of suboxic biogeochemical processes near the sediment surface.

Marine and continental distribution and dynamic of the early spawning migration of twaite shad (Alosa fallax (Lacépède, 1803)) and allis shad (Alosa alosa (Linnaeus, 1758)) in the north-west of the Iberian Peninsula

Knowledge regarding the marine phase of twaite shad (Alosa fallax (Lacépède, 1803)) and allis shad (Alosa alosa (Linnaeus, 1758)) remains limited. To understand the coastal and continental distribution and dynamic of migration of these species, in the present study we collected official data records of marine landings (kg), separated according to species, for all fish markets in Galicia (north-west of the Iberian Peninsula) and undertook freshwater field sampling campaigns. The findings indicate that both species of shad exhibit a coastal distribution near the rivers where they spawn, namely the Minho and Ulla rivers. Catches at sea declined from January, a phenomenon that can be understood as the onset of migration to the rivers. Bycatch reports are important because both A. fallax and A. alosa are listed in the Annex V of the European Union Habitats Directive, which lists animal species whose exploitation and taking in the wild may be subject to management measures. However, for a better management of these species it is necessary to understand the magnitude of displacements and connection of shad populations at sea.

Soil organic carbon as a factor in passive microwave retrievals of soil water content over agricultural croplands

Remote sensing has the potential to deliver global soil water content (SWC) on vast scales with frequent revisit times for progress in the fields of climate, weather forecasting, agriculture and hydrology. Although surface roughness, vegetation and soil texture have been established as sources of variability in passive microwave interpretation, soil organic carbon (SOC) has not typically been considered as a factor that affects SWC estimation during field sampling campaigns. SOC was observed along with soil texture and bulk density during the Soil Moisture Active Passive Validation Experiment in 2012 (SMAPVEX12), the Soil Moisture Active Passive (SMAP) satellite algorithm development field sampling campaign held June 6 to July 19 in Southern Manitoba, Canada. Aerial measurements from the PALS (Passive Active L-band System) instrument were recorded over agricultural fields and forest areas from aircraft while SWC was measured simultaneously on the ground with resistance probes on 17 sampling dates. Additionally, fields were sampled for surface roughness, vegetation growth and water content, soil and vegetation temperature and soil physical characteristics. A soil core was collected on each field each sampling time to assess bulk density, soil particle size and SOC. SOC accounted for more variability in the anomalies between PALS and ground sampled SWC than sand, clay or bulk density, although all soil variables explained significant variability. With analysis by partial least squares multiple regression over 11 sampling dates and 39 fields where both ground and PALS data were well represented, only SOC contributed significantly to the regression of SWC beyond the variance all soil variables had in common. The significance of SOC in the relative SWC anomalies was highest in very wet and very dry conditions and in loam soil over all sampling dates, while bulk density was more significant in sand soils. This analysis suggests SOC is a simple variable that incorporates multiple aspects of soil hydrology and may improve the algorithms for remotely sensing estimation of SWC in various landscapes.

NOM degradation during river infiltration: Effects of the climate variables temperature and discharge

Most peri-alpine shallow aquifers fed by rivers are oxic and the drinking water derived by riverbank filtration is generally of excellent quality. However, observations during past heat waves suggest that water quality may be affected by climate change due to effects on redox processes such as aerobic respiration, denitrification, reductive dissolution of manganese(III/IV)- and iron(III)(hydr)oxides that occur during river infiltration. To assess the dependence of these redox processes on the climate-related variables temperature and discharge, we performed periodic and targeted (summer and winter) field sampling campaigns at the Thur River, Switzerland, and laboratory column experiments simulating the field conditions. Typical summer and winter field conditions could be successfully simulated by the column experiments. Dissolved organic matter (DOM) was found not to be a major electron donor for aerobic respiration in summer and the DOM consumption did not reveal a significant correlation with temperature and discharge. It is hypothesized that under summer conditions, organic matter associated with the aquifer material (particulate organic matter, POM) is responsible for most of the consumption of dissolved oxygen (DO), which was the most important electron acceptor in both the field and the column system. For typical summer conditions at temperatures >20 °C, complete depletion of DO was observed in the column system and in a piezometer located only a few metres from the river. Both in the field system and the column experiments, nitrate acted as a redox buffer preventing the release of manganese(II) and iron(II). For periodic field observations over five years, DO consumption showed a pronounced temperature dependence (correlation coefficient r = 0.74) and therefore a seasonal pattern, which seemed to be mostly explained by the temperature dependence of the calculated POM consumption (r = 0.7). The river discharge was found to be highly and positively correlated with DO consumption (r = 0.85), suggesting an enhanced POM input during flood events. This high correlation could only be observed for the low-temperature range (T < 15 °C). For temperatures >15 °C, DO consumption was already high (almost complete) and the impact of discharge could not be resolved. Based on our results, we estimate the risk for similar river-infiltration systems to release manganese(II) and iron(II) to be low during future average summer conditions. However, long-lasting heat waves might lead to a consumption of the nitrate buffer, inducing a mobilization of manganese and iron.

An approach for global sensitivity analysis of a complex environmental model to spatial inputs and parameters: A case study of an agro-hydrological model

A methodology is presented to assess the sensitivity of a complex model involved in integrated assessment and modeling approaches to spatial factors. The application considers the spatially-distributed agro-hydrological model TNT2, and its sensitivity to soil characteristics and their spatial distribution (soil pattern). The final goal is to identify soil input data that require more accurate description (measurement) and the relevant spatial resolution for soil information. Based on methods commonly used for non-spatially-distributed models (Morris method and a fractional factorial design with ANOVA), the proposed approach is innovative in the way that spatial input factors are considered in the global sensitivity analysis. The global sensitivity analysis is performed in three steps (i) screening among soil input data to identify those that most affect model outputs, (ii) quantifying the sensitivity of TNT2 to the dominant soil input factors and their interactions when considering a single soil and (iii) incorporating the soil pattern into the global sensitivity as an explicit input factor. The results indicate differences in the hierarchy of influential input factors between the screening and quantitative methods. The model's low sensitivity to spatial patterns provides recommendations for further field sampling campaigns. The hierarchical approach developed in this paper is based on sensitivity analysis methods with relatively low computational demand. The approach is generic and applicable to any complex spatial model.

Stabilisation of groundwater samples for the quantification of organic trace pollutants

The concentration of contaminants in groundwater samples can be decreased by degradation in the time course between field sampling and quantification in the laboratory, especially in samples from sites where degradation activity is enhanced by remediation measures. The sampling sites covered a variety of priority organic pollutants such as volatile aromatic and chlorinated compounds, phenols and petroleum hydrocarbons and different remediation strategies such as anaerobic and aerobic microbial in situ degradation, in situ chemical oxidation, and on-site purification with biological treatment. The stability of the contaminants' concentration was investigated over a time range of several hours without cooling in the autosampler of the analytical equipment (short term) and over several days of storage until analysis (long term). A number of stabilisation techniques suggested in international standards ISO 5667-3:2013 and ASTM D6517:2000 were compared both with regard to short term and long term stabilisation of the contaminants and their practicability for field sampling campaigns. Long term storage turned out to be problematic for most compound groups even under cooling. Short term stability was problematic also for volatiles such as benzenic aromates, naphthalene and volatile organic halogenated compounds to be analysed by headspace gas chromatography. Acidification (pH <2) was sufficient to prevent degradation of benzenic aromates, naphthalene, phenols and petrol hydrocarbons for up to seven days. The use of acids was not applicable to stabilise volatiles in waters rich in carbonates and sulphides due to stripping of the volatiles with the liberated gases. The addition of sodium azide was successfully used for stabilisation of volatile organic halogenated compounds.

The integration of field measurements and satellite observations to determine river solid loads in poorly monitored basins

The use of satellite imagery to assess river sediment discharge is discussed in the context of poorly monitored basins. For more than three decades, the Peruvian hydrological service SENAMHI has been maintaining several gauging stations in the lower part of the Amazon River catchment. This network has been recently supplemented by the Hydro-geodynamics of the Amazon Basin (HYBAM) program, which has a water quality monitoring network distributed over five locations and allows the assessment of river discharge and surface suspended sediment (SSS) concentration. In this paper, the three stations that are located near the confluence of the Marañon and Ucayali Rivers, which form the Amazon River, are reviewed in detail. Two of the stations provide a complete time series of 10-day SSS samples over the studied period. The third station, along the Ucayali River, failed to provide valid estimates of sediment concentration at the river surface. The objective is to use satellite data as a substitute for the missing records in order to assess the Ucayali River sediment discharge, which has never been directly assessed before. An additional goal was to extend the river sediment discharge records for the other two stations. Water reflectance, assessed from the time series of MODIS satellite images, is calibrated using field-sampling campaigns to provide satellite-based SSS estimates. Validation is achieved using an independent dataset consisting of the 10-day SSS samples derived from the HYBAM network. Over a 4-year period between 2004 and 2008, there is greater than 10% agreement between satellite-derived data and network data for the two stations that provided complete field records. Based on satellite-derived SSS estimates assessed from 2000 to 2009, the river sediment balance is shown to be consistent between upstream and downstream stations. The use of satellite data and their integration with field data in the context of poorly monitored basins is discussed, and different cases are proposed.

Processing of atmospheric polycyclic aromatic hydrocarbons by fog in an urban environment

Polycyclic aromatic hydrocarbons (PAH) are ubiquitous pollutants in the atmosphere, predominantly known for their toxicity. Although there has been substantial work on the atmospheric degradation of PAH, little is known about how the presence of atmospheric droplets (e.g., a fog cloud) affects the fate of PAH. In order to assess the processing of PAH and their corresponding oxidation products during a fog event, two field-sampling campaigns in Fresno, CA and Davis, CA were conducted. The simultaneous evaluation of concentrations of the PAH and oxygenated polycyclic aromatic compounds (OPAC) in the gas phase, particulate matter and fog water droplets before, during and after fog allows for the characterization of transformative and transport processes in a fog cloud. By tracking the ratio of OPAC to PAH in the individual atmospheric phases, two major polycyclic aromatic compounds-processing pathways can be identified: (i) the dissolution of OPAC from particulate matter and (ii) the uptake and oxidation of PAH in the fog water droplets. Wet deposition steadily decreases the pollutant concentration in the fog cloud droplets during a fog event; however, uptake and concentration via evaporative water loss upon the dissipation of a fog cloud cause an increase in the atmospheric pollutant concentration.

Monitoring Urban Tree Cover Using Object-Based Image Analysis and Public Domain Remotely Sensed Data

Urban forest ecosystems provide a range of social and ecological services, but due to the heterogeneity of these canopies their spatial extent is difficult to quantify and monitor. Traditional per-pixel classification methods have been used to map urban canopies, however, such techniques are not generally appropriate for assessing these highly variable landscapes. Landsat imagery has historically been used for per-pixel driven land use/land cover (LULC) classifications, but the spatial resolution limits our ability to map small urban features. In such cases, hyperspatial resolution imagery such as aerial or satellite imagery with a resolution of 1 meter or below is preferred. Object-based image analysis (OBIA) allows for use of additional variables such as texture, shape, context, and other cognitive information provided by the image analyst to segment and classify image features, and thus, improve classifications. As part of this research we created LULC classifications for a pilot study area in Seattle, WA, USA, using OBIA techniques and freely available public aerial photography. We analyzed the differences in accuracies which can be achieved with OBIA using multispectral and true-color imagery. We also compared our results to a satellite based OBIA LULC and discussed the implications of per-pixel driven vs. OBIA-driven field sampling campaigns. We demonstrated that the OBIA approach can generate good and repeatable LULC classifications suitable for tree cover assessment in urban areas. Another important finding is that spectral content appeared to be more important than spatial detail of hyperspatial data when it comes to an OBIA-driven LULC.

Greenhouse Gas Emissions from Ground Level Area Sources in Dairy and Cattle Feedyard Operations

A protocol that consisted of an isolation flux chamber and a portable gas chromatograph was used to directly quantify greenhouse gas (GHG) emissions at a dairy and a feedyard operation in the Texas Panhandle. Field sampling campaigns were performed 5 consecutive days only during daylight hours from 9:00 am to 7:00 pm each day. The objective of this research was to quantify and compare GHG emission rates (ERs) from ground level area sources (GLAS) at dairy and cattle feedyard operations during the summer. A total of 74 air samples using flux chamber were collected from the barn (manure lane and bedding area), loafing pen, open lot, settling basin, lagoons, and compost pile within the dairy operation. For the cattle feedyard, a total of 87 air samples were collected from four corner pens of a large feedlot, runoff holding pond, and compost pile. Three primary GHGs (methane, carbon dioxide, and nitrous oxide) were measured and quantified from both operations. The aggregate estimated ERs for CH4, CO2, and N2O were 836, 5573, 3.4 g hd−1 d−1 (collectively 27.5 kg carbon dioxide equivalent (CO2e) hd−1 d−1), respectively, at the dairy operation. The aggregate ERs for CH4, CO2, and N2O were 3.8, 1399, 0.68 g hd−1 d−1 (1.7 kg CO2e hd−1 d−1), respectively, from the feedyard. The estimated USEPA GHG ERs were about 13.2 and 1.16 kg CO2e hd−1 d−1, respectively, for dairy and feedyard operations. Aggregate CH4, CO2 and N2O ERs at the dairy facility were about 219, 4 and 5 times higher, respectively, than those at the feedyard. At the dairy, average CH4 ERs estimated from the settling basin, primary and secondary lagoons were significantly higher than those from the other GLAS, contributing about 98% of the aggregate CH4 emission. The runoff holding pond and pen surface of the feedyard contributed about 99% of the aggregate CH4 emission. Average CO2 and N2O ERs estimated from the pen surface area were significantly higher than those estimated from the compost pile and runoff pond. The pen surface alone contributed about 93% and 84% of the aggregate CO2 and N2O emission, respectively. Abatement and management practices that address GHG emissions from these sources will likely be most effective for reducing facility emissions.

Impact of hydrogeological data on measures of uncertainty, site characterization and environmental performance metrics

The significance of conditioning predictions of environmental performance metrics (EPMs) on hydrogeological data in heterogeneous porous media is addressed. Conditioning EPMs on available data reduces uncertainty and increases the reliability of model predictions. We present a rational and concise approach to investigate the impact of conditioning EPMs on data as a function of the location of the environmentally sensitive target receptor, data types and spacing between measurements. We illustrate how the concept of comparative information yield curves introduced in de Barros et al. [de Barros FPJ, Rubin Y, Maxwell R. The concept of comparative information yield curves and its application to risk-based site characterization. Water Resour Res 2009;45:W06401. doi:10.1029/2008WR007324 ] could be used to assess site characterization needs as a function of flow and transport dimensionality and EPMs. For a given EPM, we show how alternative uncertainty reduction metrics yield distinct gains of information from a variety of sampling schemes. Our results show that uncertainty reduction is EPM dependent (e.g., travel times) and does not necessarily indicate uncertainty reduction in an alternative EPM (e.g., human health risk). The results show how the position of the environmental target, flow dimensionality and the choice of the uncertainty reduction metric can be used to assist in field sampling campaigns.

Biomass carbon stocks and their changes in northern China’s grasslands during 1982–2006

Grassland covers approximately one-third of the area of China and plays an important role in the global terrestrial carbon (C) cycle. However, little is known about biomass C stocks and dynamics in these grasslands. During 2001-2005, we conducted five consecutive field sampling campaigns to investigate above-and below-ground biomass for northern China's grasslands. Using measurements obtained from 341 sampling sites, together with a NDVI (normalized difference vegetation index) time series dataset over 1982-2006, we examined changes in biomass C stock during the past 25 years. Our results showed that biomass C stock in northern China's grasslands was estimated at 557.5 Tg C (1 Tg=10(12) g), with a mean density of 39.5 g C m(-2) for above-ground biomass and 244.6 g C m(-2) for below-ground biomass. An increasing rate of 0.2 Tg C yr(-1) has been observed over the past 25 years, but grassland biomass has not experienced a significant change since the late 1980s. Seasonal rainfall (January-July) was the dominant factor driving temporal dynamics in biomass C stock; however, the responses of grassland biomass to climate variables differed among various grassland types. Biomass in arid grasslands (i.e., desert steppe and typical steppe) was significantly associated with precipitation, while biomass in humid grasslands (i.e., alpine meadow) was positively correlated with mean January-July temperatures. These results suggest that different grassland ecosystems in China may show diverse responses to future climate changes.

Application of a Rule-Based Model to Estimate Mercury Exchange for Three Background Biomes in the Continental United States

Ecosystems that have low mercury (Hg) concentrations (i.e., not enriched or impacted by geologic or anthropogenic processes) cover most of the terrestrial surface area of the earth yet their role as a net source or sink for atmospheric Hg is uncertain. Here we use empirical data to develop a rule-based model implemented within a geographic information system framework to estimate the spatial and temporal patterns of Hg flux for semiarid deserts, grasslands, and deciduous forests representing 45% of the continental United States. This exercise provides an indication of whether these ecosystems are a net source or sink for atmospheric Hg as well as a basis for recommendation of data to collect in future field sampling campaigns. Results indicated that soil alone was a small net source of atmospheric Hg and that emitted Hg could be accounted for based on Hg input by wet deposition. When foliar assimilation and wet deposition are added to the area estimate of soil Hg flux these biomes are a sink for atmospheric Hg.

Evaluating methods for predicting indoor residential volatile organic compound concentration distributions

Accurate modeling of exposure to volatile organic compounds (VOCs) over a large study population depends on proper characterization of concentrations in the indoor residential environment. However, owing to the high expense of field sampling campaigns for determining indoor air concentrations, such studies have only been conducted for limited populations. Therefore, there is a need to determine the degree to which results can be extrapolated to unstudied settings through the use of models, the most appropriate information required to do so and the potential errors associated with the use of sub-optimal information. The goal of this analysis is to evaluate three different source indicators used to predict indoor VOC concentration distributions for a new study population. Data from two field studies are used. For each data set, source strength, indoor-outdoor (I-O) difference and indoor/outdoor (I/O) ratio, collectively referred to as source indicators, are calculated and fit with distributions. These distributions, as well as distributions for air exchange, volume and outdoor concentrations for the new study population, are used for predicting indoor concentrations using Monte Carlo simulations, which are then compared with actual distributions. As expected, the source strength often provides the most effective predictions (11 out of 20 instances), but is slightly outperformed by, although is still comparable with, the I-O difference on some occasions (4 out of 20). The I/O ratio generally has the greatest prediction errors, given its dependence on outdoor concentrations, but performs optimally in a limited number of cases (5 out of 20). When deciding between the source strength and I-O difference, one must consider the availability and fidelity of both current and future data. On the basis of our findings, exposure-monitoring studies should report the distribution statistics for I-O differences and, if the data are available, for source strengths.

Testing the use of range-finder OSL dating to inform field sampling and laboratory processing strategies

A newly developed range-finder luminescence dating method is applied to samples from the eastern Punjab region of Pakistan. Overbank sediments from this area are the subject of an ongoing project into the demise of the Harappan civilization about 4.2 ka and the range-finder technique was used to ascertain whether samples from three pits are from this part of the Holocene. Luminescence measurements of raw sample gave a signal dominated by feldspars, even when using a [post-IR] optically stimulated luminescence (OSL) signal. Following etching in hydrofluoric acid samples gave OSL signals characteristic of quartz and these were used to calculate the equivalent dose. The total dose rate was estimated from beta counting. Eight range-finder OSL ages extend from 4000 to 6600 years ago and are consistent with two radiocarbon ages from the same pits demonstrating that these sediments do straddle the period of interest for this project. The range-finder approach provides a rapid means of informing future field sampling campaigns.

Intercity transferability of land use regression models for estimating ambient concentrations of nitrogen dioxide

Land use regression (LUR) is a method for predicting the spatial distribution of traffic-related air pollution. To facilitate risk and exposure assessment, and the design of future monitoring networks and sampling campaigns, we sought to determine the extent to which LUR can be used to predict spatial patterns in air pollution in the absence of dedicated measurements. We evaluate the transferability of one LUR model to two other geographically comparable areas with similar climates and pollution types. The source model, developed in 2003 to estimate ambient nitrogen dioxide (NO(2)) concentrations in Vancouver (BC, Canada) was applied to Victoria (BC, Canada) and Seattle (WA, USA). Model estimates were compared with measurements made with Ogawa passive samplers in both cities. As part of this study, 42 locations were sampled in Victoria for a 2-week period in June 2006. Data obtained for Seattle were collected for a different project at 26 locations in March 2005. We used simple linear regression to evaluate the fit of the source model under three scenarios: (1) using the same variables and coefficients as the source model; (2) using the same variables as the source model, but calculating new coefficients for local calibration; and (3) developing site-specific equations with new variables and coefficients. In Scenario 1, we found that the source model had a better fit in Victoria (R(2)=0.51) than in Seattle (R(2)=0.33). Scenario 2 produced improved R(2)-values in both cities (Victoria=0.58, Seattle=0.65), with further improvement achieved under Scenario 3 (Victoria=0.61, Seattle=0.72). Although it is possible to transfer LUR models between geographically similar cities, success may depend on the between-city consistency of the input data. Modest field sampling campaigns for location-specific model calibration can help to produce transfer models that are equally as predictive as their sources.

Sampling precautions for the measurement of nitrated polycyclic aromatic hydrocarbons in ambient air

Because of the toxicity of polycyclic aromatic hydrocarbons (PAHs) and of their oxidation products, such as nitrated and oxygenated PAHs (NPAHs and OPAHs), the determination of their concentrations is of great interest in terms of atmospheric pollution control. Then, normalisation of sampling procedures appears essential. In this context, this paper presents a comparison of particulate PAH, OPAH and NPAH concentrations determined with two different samplers (cascade impactor and conventional high volume sampler) installed in parallel during several field sampling campaigns carried out under different environmental conditions. For winter and summer periods, the PAH and OPAH concentrations determined with both sampling systems were considered as equivalent. In the summer period, NPAH concentrations quantified with both sampling devices were similar whereas in the winter period, the conventional high volume sampler underestimated their concentrations by a factor of 3–4. This underestimation was observed in the same proportion for all the 17 quantified NPAHs. Analytical error, NPAH formation during the sampling and NPAH degradation by reaction with gaseous oxidants associated to sampling methodology were unable to explain such differences between both samplers used in parallel. A probable hypothesis is that the heating of the PM 10 head of the high volume sampler in the winter period generates an increase of the internal sampler temperature that could intensify the chemical degradation of the NPAHs inducing the underestimation of their concentrations in the atmosphere. Further investigations will be necessary to confirm the importance of the temperature on the chemical degradation of these compounds and to understand the different behaviour of PAHs and OPAHs. Consequently, we suggest using oxidant scrubber to prevent chemical degradation of PAHs and derivatives during their sampling. Moreover, we advise against the heating of the sampling head which could induce an increase of these reactions of degradation especially for NPAHs.