Roadside Samples Research Articles

Strong versus weak digestions: ligand-based soil extraction geochemistry

ABSTRACT Ligand-based soil extraction geochemistry is a high resolution, multi-element soil analysis technique for mineral exploration. The use of strong complexing ligands in the extraction procedure limits matrix element interference, reduces background analyte values (noise) and overcomes potential pH effects. Improvements in the spatial and amplitude (signal to noise) resolution of this technique compared to total digestion or more aggressive partial digestions is useful not only in areas with exotic cover, but in residual and weathered terrain where duricrust development and mechanical transport can cause dispersion of anomalies. At the Green Tree Frog Prospect in Queensland, Australia, superior amplitude contrast and more accurate delineation of sub-surface mineralization is observed for ligand-based geochemistry compared to fire assay in terrain with exotic tertiary cover. In Guinea, West Africa, ligand-based soil extraction of gold has outlined five new economic zones since its introduction. Comparison of a range of weak and strong digestions and extractions from glacial till at Cross Lake, a VMS (volcanogenic massive sulphide) deposit in the Abitibi belt of Canada, provides very good evidence as to the value of strong ligands in the extraction. More recent developments of this technique utilize compatible and incompatible elements (principally Ni and Ce) to obtain inferred geology images, which are of direct assistance to exploration where outcrop and sub-crop are limited or of low density. A prospect scale image of inferred geology from The Mount SE, Widgiemooltha in the Eastern Goldfields of the Yilgarn Craton, Western Australia obtained from a ligand based soil geochemistry program provides superior detail to 1:40 000 standard geological mapping. A semi-regional scale roadside sampling program at Wongan Hills on the western side of the Yilgarn Craton illustrates that this type of geochemistry has a role to play in early stage, regional-scale exploration where geological outcrop and sub-crop are limited.

Characteristics of Traffic-related Emissions: A Case Study in Roadside Ambient Air over Xi’an, China

Traffic-related emissions were measured at a heavy-traffic roadside in Xi’an at the end of April, 2008 to survey the exposure levels of freshly emitted carbon monoxide (CO), mass and chemical composition (OC, EC, inorganic ions, and PAHs) of PM 10, and ozone (O3). In general, high levels of mass concentration and chemical species in PM10 were observed during daily heavy traffic periods (morning, noon, and evening traffic rush hours), especially in the morning traffic rush hour. OC and EC accounted for 9.3% and 3.0% of PM10 mass, respectively, and the ratios of OC/EC were constant during the heavy traffic periods (with a mean value of 3.2). Water-soluble ions constituted 14.0% of PM10 and the dominant ionic species were Ca 2+ , SO4 2- , and NO3 - in the roadside samples. Re-suspended road dust constituted a large fraction of PM10, causing the PM10 samples to become more alkaline. The concentrations of 12 prior-controlled PAHs revealed the potential high health risk of this roadside area in Xi’an. The diurnal variation in CO and O3 exhibited a different trend, which indicated that CO level was largely influenced by the instantaneous emission of vehicles while O3 was closely associated with the overall traffic conditions and meteorological status.

Comparison of Water-Soluble Organic Components in Size-Segregated Particles between a Roadside and a Suburban site in Saitama, Japan

To clarify the characteristics of the water-soluble organic components in atmospheric aerosols, size-separated aerosol samples were simultaneously collected at a roadside site (R) and a suburban background site (S) in Saitama, Japan, during spring and summer 2007 and winter 2008. Chemical compositions, including water-soluble organic carbon (WSOC), organic carbon, inorganic ionic components, and individual water-soluble organic acids (saturated dicarboxylic acids, unsaturated dicarboxylic acids, ketocarboxylic acids, and dicarbonyls), were analyzed in size-separated samples. The seasonal variation of WSOC in Saitama aerosols was larger than the spatial difference between the two sites, with summer WSOC concentrations being 2.5-2.8 times those in the other seasons. Seasonal average concentrations of the detected organic acids in PM7.0 were 542 ng/m^3 (R) and 670 ng/m^3 (S). Strong correlations were observed between C2-C5 n-dicarboxylic acids and ambient oxidants. The concentration ratios of individual n-dicarboxylic acids (C2-C5) to elemental carbon were significantly higher in suburban samples than in roadside samples, indicating that the contribution of secondary formation to these acids was larger in suburban samples. During the warm seasons, the concentrations of sulfate, ammonium, WSOC, and individual acids in fine particles were very high, whereas nitrate, chloride, sodium, and calcium concentrations were higher in coarse particles. Comparisons between the two sites showed that secondary formation contributed more to the total amount of particulate water-soluble organic acids in Saitama aerosols than direct emissions from anthropogenic and natural sources. However, vehicle exhaust was also an important source of dicarboxylic acids in Saitama aerosols, especially in the near-roadside environment.

Fractionation of Cd, Cr, Pb and Ni in roadside soils of Uyo, Niger Delta Region: Nigeria using the optimized BCR sequential extraction technique

The optimized BCR sequential extraction procedure was applied to nine roadside soil samples for the determination of Cd, Cr, Pb and Ni. The extractable metals were isolated into three operationally defined fractions viz: acid extractable, reducible and oxidizable. The residue was treated with aqua regia solution. Metal analysis was done using flame atomic absorption spectrophotometry with air–acetylene flame. Results obtained showed the concentrations of the metals as relative abundance in the mobile phases of the samples (based on the sum of the first three fractions) are in the following order: Cd(91.9) > Pb(82.8) > Ni(49.5) > Cr(39.0). The most non-mobilizable metals were Cr and Ni which are generally lithogenic, associated with the silicate matrix, and the order is as follows: Cr(61.0) > Ni(50.5) > Pb(17.2) > Cd(8.1). The recovery of all the metals expressed as the ratio of total metal concentration to fractional sum of the optimized BCR sequential extraction procedure was of the order: Cr(95.6) > Pb(95.0) > Ni(94.8) > Cd(92.4).

Pt and Pd concentrations and source in urban roadside soils from Xuzhou, China

This investigation represented the preliminary study to characterize Pt and Pd concentrations and enrichment ratios in urban roadside soils. Roadside soil samples were analyzed by ICP-MS. Data from 21 roadside topsoil samples show medians of Pt and Pd concentrations are 2.9 and 2.8ngg−1, respectively. These values are higher than those of upper crust that average 0.4 and 0.4ngg−1, respectively. The relatively lower Pt and Pd concentrations are expected due to recent introduction of catalysts to China compared to the prolonged use of catalysts in Europe. Hierarchical clustering analysis indicates that Pt and Pd in Xuzhou urban roadside soils were mainly from the traffic emissions. Computation of enrichment ratios using the upper crust values as background levels suggests that the roadside soils had enrichment medians of 6.4 for Pt (range 2.5–11.75) and of 6.75 for Pd (range 2.75–9.25). Lower Pt/Pd ratios (range 0.35–2.86) in relation to similar studies in other countries were observed due to the different automobile catalytic converters. In general, fine fraction (<250μm) contains higher Pt and Pd concentrations compared to the coarse fraction (250–500μm).

Genotoxicity of total and fractionated extractable organic matter in fine air particulate matter from urban Guangzhou: Comparison between haze and nonhaze episodes

To investigate the genotoxic potencies of extractable organic matter (EOM) in aerosols, fine air particulate matter (PM(2.5)) was collected simultaneously at a roadside (1.2 m above ground) and at a rooftop location (50 m above ground) in urban Guangzhou (China) during a nonhaze period in September 2006 and a haze period in October 2006. Particle-bound organics were extracted and separated into aliphatic, aromatic, and polar fractions. The genotoxicity of total and fractionated extracts were tested by single-cell electrophoresis (comet assay) with human blood lymphocytes. The PM(2.5) concentrations usually exceeded the U.S. National Ambient Air-Quality Standard level (65 microg/m(3)) at both the roadside and the rooftop. During nonhaze days, the roadside samples showed substantially higher PM(2.5) levels (108-130 microg/m(3)) and significantly higher genotoxic effects of total and fractionated EOM (p < 0.05 for >10 m(3) air equivalent/ml) than the rooftop samples. During haze days, however, PM(2.5) levels and genotoxic potencies of rooftop samples were drastically elevated and comparable to those of roadside samples, implying that during haze episodes, most people in the urban area are exposed to PM(2.5) pollution as serious as in the heavily polluted roadside microenvironment. All total EOM samples showed significant (p < 0.05) dose-response effects, and their effects as olive tail moment were less than the sums of the three fractions. Aromatic fractions of EOM exhibited the greatest genotoxic potencies, but polar fractions also contributed substantially to DNA-damaging effects. Polycyclic aromatic hydrocarbons and nitrated derivatives likely are the most important species responsible for the genotoxicity of EOM in PM(2.5).

Chemical composition of atmospheric aerosols in the general environment and around a trunk road in the Tokyo metropolitan area

To evaluate the influence of vehicle exhaust particles on the urban atmosphere, atmospheric aerosols collected in the general environment and at a trunk road sampling site in the Tokyo metropolitan area were analyzed for carbonaceous and ionic components. Samples were collected as fine (<2.1 μm) and coarse particle (2.1–7.0 μm) from April 2003 to March 2004 using low-volume Andersen sampler. The carbonaceous components were analyzed by a thermal method and a thermal/optical method. Elemental carbon (EC) determined by thermal method was higher than those by thermal/optical method, and slope of linear regression of the thermal method versus the thermal/optical method differed at both sampling points. These results suggested possible analytical artifacts, a difference in the composition of the carbonaceous components of the aerosols, or both. The EC concentrations in fine particles in the roadside were higher than in the general environment by 5 μg m −3, and it was accounted for 68% of the difference of the mass concentration. The mass concentration reconstructed by the mass closure model using element analysis results corresponded more closely to the observed mass concentration in the general environment samples than in the roadside samples. It is suggested that the contribution of the organic compounds in the roadside particles was underestimated. Diesel vehicle emission control regulations implemented in October 2003 seem to have had an effect because there was a significant difference in the average concentration of suspended particulate matter and NO x before and after implementation of the regulations. Moreover, the EC/TC ratio has been decreasing over time.

Adaptive roadside sampling for bark beetle damage assessment

Bark beetle infestations are often scattered throughout the forest landscape and therefore difficult to accurately and rapidly assess. We tested a roadside sampling technique in a pure maritime pine forest ( Pinus pinaster) of ca. 1300 ha where bark beetle outbreak foci were observed following a windstorm. The sampling method relied on the count along stand edges of all dying or dead trees sighted within a fixed distance from the road. About 2300 trees attacked by Ips sexdentatus were recorded and located using colour-infrared aerial photography. Accuracy of the infestation map was verified by ground sampling. Piles of cut logs stored along the edge significantly increased the percentage of attacked trees in the neighbouring stand. However, the percentage of attacked trees within the stand edges did not differ with the percentage within the stand interior. It allowed us to use stand edges as sampling units to estimate the mean percentage of attacked trees per stand. At the stand scale, the use of a fixed 10 m wide strip along stand edges maximized the detection of attacked trees and minimized the bias of estimated percent of attacked trees. Based on GIS data, various stratified roadside sampling plans with increasing numbers of edges per stand and increasing numbers of stands per forest were simulated by bootstrap resampling. In a forest without any storage of cut logs, systematic roadside surveys underestimated the level of damage. The sampling accuracy increased with the kilometers of edges surveyed. In a forest with piles of cut logs on which bark beetles can breed, the best option was an adaptive sampling plan where at least two additional consecutive edges were observed in stands close to the pile. As compared to systematic sampling plans, adaptive plans were three times less expensive in terms of sampling effort for the same accuracy. Overall, adaptive sampling plans were also more robust as they provided less biased estimates as the proportion of stands with nearby piles increased in simulated forests.

Factors influencing particle number concentrations, size distributions and modal parameters at a roof-level and roadside site in Leicester, UK

Measurements of urban particle number concentrations and size distributions in the range 5-1000 nm were taken at elevated (roof-level) and roadside sampling sites on Narborough Road in Leicester, UK, along with simultaneous measurements of traffic, NO(x), CO and 1,3-butadiene concentrations and meteorological parameters. A fitting program was used to determine the characteristics of up to five modal groups present in the particle size distributions. All particle modal concentrations peaked during the morning and evening rush hours. Additional events associated with the smallest mode, that were not observed to be connected to primary emissions, were also present suggesting that this mode consisted of newly formed secondary particles. These events included peaks in concentration which coincided with peaks in solar radiation, and lower concentrations of the larger modes. Investigation into the relationships between traffic flow and occupancy indicated three flow regimes; free-flow, unstable and congested. During free-flow conditions, positive linear relationships existed between traffic flow and particle modal number concentrations. However, during unstable and congested periods, this relationship was shown to break-down. Similar trends were observed for concentrations of the gas phase pollutants NO(x), CO and 1,3-butadiene. Strong linear relationships existed between NO(x), CO, 1,3-butadiene concentrations, nucleation and Aitken mode concentrations at both sampling locations, indicating a local traffic related emission source. At the roadside, both nucleation and Aitken mode are best represented by a decreasing exponential function with wind speed, whereas at the roof-level this relationship only occurred for Aitken mode particles. The differing relationships at the two sampling locations are most likely due to a combination of meteorological factors and distance from the local emission source.

Characteristics and diurnal variations of NMHCs at urban, suburban, and rural sites in the Pearl River Delta and a remote site in South China

The Pearl River Delta (PRD) is one of the most industrialized and urbanized regions in China. With rapid growth of the economy, it is suffering from deteriorating air quality. Non-methane hydrocarbons (NMHCs) were investigated at urban and suburban sites in Guangzhou (GZ), a rural site in PRD and a clean remote site in South China, in April 2005. Additional roadside samples in GZ and Qingxi (QX, a small industrial town in PRD), ambient air samples at the rooftop of a printing factory in QX and exhaust samples from liquefied petroleum gas (LPG)—fueled taxis in GZ were collected to help identify the source signatures of NMHCs. A large fraction of propane (47%) was found in exhaust samples from LPG-fueled taxis in GZ and extremely high levels of toluene (2.0–3.1 ppmv) were found at the rooftop of the printing factory in QX. Vehicular and industrial emissions were the main sources of NMHCs. The effect of vehicular emission on the ambient air varied among the three PRD sites. The impact of industrial emissions was widespread and they contributed greatly to the high levels of aromatic hydrocarbons, especially toluene, at the three PRD sites investigated. Leakage from vehicles fueled by LPG contributed mainly to the high levels of propane and n-butane at the urban GZ site. Ethane and ethyne from long-range transport and isoprene from local biogenic emission were the main contributors to the total hydrocarbons at the remote site. Diurnal variations of NMHCs showed that the contribution from vehicular emissions varied with traffic conditions and were more influenced by fresh emissions at the urban site and by aged air at the suburban and rural sites. Isoprene from biogenic emission contributed largely to the ozone formation potential (OFP) at the remote site. Ethene, toluene and m/ p-xylene were the main contributors to the OFP at the three PRD sites.

An investigation into unpaved road emissions from a UK surface limestone quarry using cylindrical adhesive pad collectors and image analysis

Demand for increased aggregates extraction combined with ongoing pressure to adhere to existing and future environmental regulatory requirements requires sustained research and investigation into associated particulate emissions. Open pit quarries commonly operate ‘blast and haul’ extraction methods, implying that any increase in production will lead to increases in quarry traffic and hence unpaved haul road particulate emissions. This paper presents an analysis and discussion of experimental data collected during a roadside particulate emission sampling study conducted within a major UK limestone quarry. The particulate samples were collected using a total of six cylindrical adhesive pad type collectors located symmetrically, at equally spaced intervals upwind and downwind of an unpaved truck haul road. A total of three sampling studies were conducted, each representing approximately 1 hour of road activity and between 6 and 8 vehicle passes. The first two sampling periods were conducted on an initially unwetted haul road. The third sampling period was conducted following road wetting by a bowser. The surface characteristics of the haul road surface were obtained by the collection of a series of swept surface material samples. An analysis of these samples collected prior to and during each of the sampling periods established the surface moisture and silt content of the unpaved road surface. Weather data were obtained using a permanently sited metrological station located on a hill above the quarry, together with a portable weather station located upwind of the haul road to providing accurate localized data. The dust samples collected on the adhesive pads were sized using an image analysis (IA) based method. The IA method employed advanced image enhancement functions to characterize the captured particulates in terms of total count, captured mass, particle aspect ratio and size distribution. These characteristics were compared for each collector sample over each of the three sampling periods. The study concluded that the IA method was able to provide a useful and consistent range of sample characteristics, although the limit of the resolution of the sizing of the particulates sampled was found to be approximately 5 μm. It was found that there was minimal variation in the sampled particulate size distribution and aspect ratio up to a collection distance of 29 m from the roadside in the downwind direction. A clear attenuation in the capture of particles was identified in terms of particle count and total captured mass reporting to measured upwind background levels at 29 m from source. The directionality of the particulate concentrations collected on the pads was found to vary significantly. It was concluded that IA offers a viable method for the analysis of samples collected from cylindrical adhesive pad collectors.

Investigation of Past and Present Multi-metal Input along Two Highways of British Columbia, Canada, Using Lead Isotopic Signatures

A multi-media monitoring field investigation, which included atmospheric, road sediment and soil samples, was carried out at two highway study sites to identify past and present Pb sources. Past Pb anthropogenic sources such as paint and leaded gasoline were linked to significant Pb accumulation in roadside soils at both sites through Pb isotopic analyses. This was achieved by identifying the distinct Pb isotopic composition in older versus newer Pb accumulation at different depths across the soil profile. Older Pb accumulations exhibited lower 206Pb/207Pb isotopic ratios, consistent with Canadian Pb-bearing ores, whereas newer Pb accumulations reflected a mixture of the 206Pb/207Pb ratios of road sediment samples, with the Pb isotopic signature of uncontaminated soil. Isotopic analyses were also helpful in identifying road sediment as an important current source of Pb in roadside soils, by comparing the isotopic signatures derived from road sediment and atmospheric dustfall. The known association of Pb with anthropogenic sources was used to indirectly relate other metals (Cu, Mn, Zn) to the same source by the Enrichment Ratio method. Significant positive correlations at the 90–95% confidence level were found between Cu, Zn and Pb Enrichment Ratios in roadside and dust deposition samples. Weaker correlations were found between Mn and Pb, at the highway study site with the least amount of traffic. However, correlations between these two metals were significant at the 90% confidence level for the busier highway site highlighting Mn potential anthropogenic source. An isotopic tracer study is suggested to further investigate the process of Mn redistribution in the environment due to exhaust fuel emissions. More research is needed regarding the potential impact from using a Mn-based fuel additive.

Preconcentration of cobalt using Amberlyst 36 as a solid-phase extractor and its determination in various environmental samples by flame atomic absorption spectrometry

A new and simple column-solid-phase extraction method has been developed to separate and preconcentrate trace cobalt in water and soil prior to its determination by flame atomic absorption spectrometry (FAAS). Different factors such as pH of sample solution, sample volume, amount of resin, flow rate of aqueous solution, volume and concentration of eluent, and matrix effects for preconcentration were optimized. Under optimized experimentally established conditions, an analytical detection limit of 0.44 µg L−1, precision (RSD) of 1.9%, enrichment factor of 200, and capacity of resin of 82 mg g−1 were obtained. The method was applied for cobalt determination by FAAS in tap water, natural drinking water, soil, and roadside dust samples. The accuracy of the method is confirmed by analysing standard reference material (Montana Soil, SRM 2711).

Mixing ratios and sources of halocarbons in urban, semi-urban and rural sites of the Pearl River Delta, South China

The pearl river delta (PRD) region is one of the most important industrial and manufacturing centers of China and the world. In order to explore the regional mixing ratios of halocarbons in the PRD atmosphere and to reconcile the major halocarbon emission sources, air samples were collected in an urban site in Guangzhou City, a semi-urban site in Panyu and a rural site on Dinghu Mountain, as well as roadside sites and vehicular tunnels of the PRD in 2001 and 2004. The samples were analyzed for a variety of carbon-containing compounds. The results revealed elevated regional mixing ratios of most halocarbons, especially trichloroethene (C 2HCl 3), methyl iodide (CH 3I), tetrachloroethene (C 2Cl 4), bromochlorodifluoromethane (Halon-1211, CBrClF 2), 1-dichloro-1,1-fluoroethane (HCFC-142b, CH 3CClF 2) and trichloromethane (CHCl 3) when compared with the background levels of the western Pacific and East Asian coast, and the Northern Hemisphere suggesting that there are significant sources of halocarbons in the PRD region. Higher dichlorodifluoromethane (CFC-12, CCl 2F 2), 1,1,1-trichlorotrifluoroethane (CFC-113, CCl 2FCClF 2), dibromomethane (CH 2Br 2) and tribromomethane (CHBr 3) mixing ratios were found in the tunnels and roadside samples when compared with the ambient samples. In these samples, CH 2Br 2 and CHBr 3 correlated well with each other and methyl bromide (CH 3Br) suggesting they are associated with exhaust emissions from vehicles running on leaded gasoline. High levels of methyl halides: methyl chloride (CH 3Cl), CH 3Br and CH 3I, and CH 2Br 2, bromodichloromethane (CHBrCl 2), CHBr 3 and dimethyl sulfide (C 2H 6S, DMS) were simultaneously observed in the oceanic air masses that originated from the coastal areas of southeast China and had passed over the Pearl River Estuary. Good correlations were found between CH 2Br 2 and CHBr 3 with linear regression slopes of 0.17 and 0.15 for the Dinghu Mountain and Guangzhou City samples, respectively, and between CH 3I and CHBr 3, and DMS suggesting that emissions from the coastal territorial ecosystems of the PRD are important sources of the methyl halides, CH 2Br 2, CHBrCl 2, CHBr 3 and DMS observed.

Vehicular fuel composition and atmospheric emissions in South China: Hong Kong, Macau, Guangzhou, and Zhuhai

Abstract. Vehicular emission is an important source of air pollutants in urban cities in the Pearl River Delta (PRD) region of South China. In order to study the impact of evaporative loss of vehicular fuel on air quality, several commonly used fuel samples were collected in four main cities in the PRD region – Hong Kong, Guangzhou, Macau and Zhuhai, and analyzed for their volatile organic compounds (VOCs) composition. Source profiles of vapors of the vehicular fuels used in these cities were constructed and are believed to be the first reported for the PRD region. The C8-C10 hydrocarbons were the main constituents of diesel. Different from diesel, gasoline used in the PRD region was mainly comprised of lighter C4-C7 hydrocarbons, with toluene and i-pentane being the two most abundant species. The toluene content in the Hong Kong and Macau gasoline samples were higher than that in Guangzhou and Zhuhai, while the reverse was true for the benzene content. The benzene levels in Guangzhou and Zhuhai exceeded the maximum allowable benzene levels for Mainland China unleaded gasoline. Liquefied Petroleum Gas (LPG) samples were collected only in Hong Kong and were comprised mainly of n-butane, propane and i-butane. Traffic samples indicated that evaporative loss and vehicular combustion were the primary contributors to elevated VOC levels in roadside atmospheres. Significant i-pentane and toluene concentrations were observed in roadside atmospheres in all four cities. Ratio of i-pentane in gasoline vapors to that in roadside samples were calculated and this showed that the degree of evaporative loss were higher in Guangzhou and Zhuhai than that in Hong Kong and Macau. We suggest the difference is due to the better maintenance and more new cars in Hong Kong and Macau. From tunnel samples collected in Hong Kong in two different years, we found that the relative amount of propane, i-butane, and n-butane increased between 2001 to 2003, consistent with the 40% increase in LPG fueled vehicles. Propane to butanes ratios were calculated for LPG samples and tunnels samples, and the comparable ratios illustrated the LPG leakages from LPG fueled vehicles crossing the tunnel.

Black Carbon and Polycyclic Aromatic Hydrocarbon Emissions from Vehicles in the United States–Mexico Border Region: Pilot Study

The investigators developed a system to measure black carbon (BC) and particle-bound polycyclic aromatic hydrocarbon (PAH) emission factors during roadside sampling in four cities along the United States–Mexico border, Calexico/Mexicali and El Paso/Juárez. The measurement system included a photoacoustic analyzer for BC, a photoelectric aerosol sensor for particle-bound PAHs, and a carbon dioxide (CO2) analyzer. When a vehicle with measurable emissions passed the system probe, corresponding BC, PAH, and CO2 peaks were evident, and a fuel-based emission factor was estimated. A picture of each vehicle was also recorded with a digital camera. The advantage of this system, compared with other roadside methods, is the direct measurement of particulate matter components and limited interference from roadside dust. The study revealed some interesting trends: Mexican buses and all medium-duty trucks were more frequently identified as high emitters of BC and PAH than heavy-duty trucks or passenger vehicles. In addition, because of the high daily mileage of buses, they are good candidates for additional study. Mexican trucks and buses had higher average emission factors compared with U.S. trucks and buses, but the differences were not statistically significant. Few passenger vehicles had measurable BC and PAH emissions, although the highest emission factor came from an older model passenger vehicle licensed in Baja California.

Soil radioactivity and radiation absorbed dose rates at roadsides in high-traffic density areas in Ibadan metropolis, southwestern Nigeria

The effect of ionising radiation on biological systems depends among other factors on time and place of exposure and population involved. Socio-economic factors in human daily activities have subjected humans to certain environmental health risks. In most cases the risk appears to be higher outdoors than indoors. In order to quantify the radiation exposure levels to individuals in the outdoors in areas with high human and vehicular densities, roadside soil samples were collected from major bus stops and round-about in the metropolis of Ibadan and were analysed for their activity concentration levels using gamma-ray spectrometry. The 40K activity concentration ranged between 96.1 and 336.5 Bq kg(-1) with a mean of 219.8 +/- 71.4 Bq kg(-1); 238U was in the range of 10.2-40.7 Bq kg(-1) with a mean of 20.3 +/- 6.9 Bq kg(-1) while that of 232Th ranged between 13.3 and 29.7 Bq kg(-1) with a mean of 21.2 +/- 5.3 Bq kg(-1). The total gamma absorbed dose rates in air ranged between 17.2 and 41.8 nGy h(-1) with an average of 32.0 +/- 5.8 nGy h(-1). The gamma absorbed dose rates at the roadsides in traffic density areas were found to be lower when compared with previously reported values in natural and undisturbed locations in non-traffic density areas in the city.

Volatile organic compounds in 43 Chinese cities

Whole air samples were collected in 43 Chinese cities in January and February 2001, and methane and nonmethane hydrocarbon (NMHC) concentrations for those samples are here discussed. In order to identify the main sources of the hydrocarbons in these cities, cross-correlations with the general combustion tracer ethyne and the gasoline marker i-pentane were investigated. Most of the identified NMHCs correlated with ethyne or i-pentane suggesting that their primary source is combustion or gasoline evaporation. To differentiate between vehicular and other combustion sources, the benzene to toluene ratio characteristic of the Chinese vehicular fleet was calculated using roadside samples (collected in 25 cities). Cities where the main source of the NMHCs was traffic related were identified. The slope resulting from the correlation of selected gases was used to identify the likely sources of the NMHCs measured. Vehicular emissions were found to be an important source of isoprene in some cities. Different VOC mixing ratio distributions throughout the country were also investigated. This paper gives a general overview of urban VOCs in many Chinese cities. Future more rigorous studies will be necessary to further characterize VOC sources in China.

Comparison of survey methods for an invasive plant at the subwatershed level

Invasive plant survey methods that are practical and economical are needed to describe established colonies and detect nascent invaders. We compared results from random and roadside surveys of Alliaria petiolata (Bieb.) Cavara & Grande across a 5730-ha subwatershed. The random survey included 150 1-ha plots; the roadside survey examined 0.1-mile increments (10-m deep) along paved roads (totaling 1104 0.16-ha plots). In the random survey, agriculture was the dominant land use (49% of sampled area), and most A. petiolata patches were in wooded, shaded riparian, and waste areas (34%, 34%, and 29% of patches, respectively). In the roadside survey, right-of-way land use was dominant (38% of sampled area), and most A. petiolata patches were in right-of-way, wooded, and shaded riparian areas (53%, 22%, and 19% of patches, respectively). According to generalized linear model analysis, survey methods did not differ in the overall probability of finding A. petiolata (P=0.17 and 0.11 for random and roadside surveys, respectively). Shaded riparian, wooded, and mixed-species right-of-way land uses were the dominant habitat for A. petiolata in both surveys, but only the random survey indicated waste areas as significant habitat. Alliaria petiolata occurred mostly as small patches in roadsides, but as large patches in random plots, suggesting faster spread in the roadside. Results indicated that disturbed lands along roadsides were important for invasion and spread of A. petiolata; therefore, the roadside survey was a useful, practical method for detecting nascent invasions and management planning. The random sampling lacked a land use bias, and provided data that could be generalized across the subwatershed; however, this method required at least four times more person hours to complete than the roadside survey for a similar amount of area. Although roadside sampling did not provide a completely reliable assessment of target plant populations within the landscape, it may provide an adequate approximation, depending on the specific goals of the survey. Concurrent surveys would provide the most complete information.

Seasonal and Spatial Variation of Solvent Extractable Organic Compounds in Fine Suspended Particulate Matter in Hong Kong

The results of a 12-month study of more than 100 solvent extractable organic compounds (SEOC) in particulate matter (PM) less than or equal to 2.5 μm (PM2.5) collected at three air monitoring stations located at roadside, urban, and rural sites in Hong Kong are reported. The total yield of SEOC that accounts for ∼8–18% of organic carbon (OC) determined by a thermal optical transmittance method was 125-2060 ng/m3, which included 14.6–128 ng/m3 resolved aliphatic hydrocarbons, 39.4–1380 ng/m3 unresolved complex mixtures, 0.6–17.2 ng/m3 polycyclic aromatic hydrocarbons, 41.6–520 ng/m3 fatty acids, and <0.1–12.1 ng/m3 alkanols. Distinct seasonal variations (summer/winter differences) were observed with higher concentrations of the total and each class of SEOC in the winter and lower concentrations in the summer. Spatial variations are also obvious, with the roadside samples having the highest concentrations of SEOC and the rural samples having the lowest concentrations in all seasons. Characteristic ratios of petroleum hydrocarbons, such as carbon preference index, unresolved to resolved components, and carbon number with maximum concentration, suggest that PM2.5 carbon in Hong Kong originates from both biogenic and anthropogenic sources. The proportion of SEOC in PM2.5 from anthropogenic sources is estimated.