Time-series analysis of above-road particulate matter at the Caldecott Tunnel exit

On November 18, 1997, above-road particulate matter (PM) lidar (light detection and ranging) signals and heavy-duty (HD) and light-duty (LD) vehicle counts were simultaneously collected for 894 10-sec sampling periods at the Caldecott Tunnel in Orinda, CA, for the purpose of measuring the relative contributions of LD and HD vehicles to the PM lidar signal under real-world driving conditions. The relationship between the PM lidar signal and traffic activity (i.e., LD and HD traffic volumes) was examined using a time-series analysis technique, multilagged regression. The time-series model results indicate that the PM lidar signal in the current sampling period (PMt) depended on the level recorded in the previous three sampling periods (i.e., PMt-1, PMt-2, and PMt-3), the number of LD vehicles in the seventh past sampling period (LDt-7), and the number of HD vehicles measured 80 sec previous to the current sampling period (HDt-8). On a 10-sec period basis, the model results indicate that HD vehicles contributed, on average, 3 times more to above-road PM lidar signals than did LD vehicles. The observed lag in the relationship between vehicle types and the lidar signal 20 m above the road suggests that resuspended road dust, rather than tailpipe exhaust emissions, was the main source of the detected PM. Detection of road dust at such heights above the road suggests the need for investigating the processes governing the vertical transport and recycling of PM over the road as a function of vehicle dynamics under a range of meteorological conditions.     

Analysis of gaseous diisocyanates in air using chemosorption sampling

A sampling procedure for 2,4- and 2,6-toluenediisocyanate (TDI) and 4,4′-diphenylmethane diisocyanate (MDI) in the range 0.007-0.7 mg/m³ in a 15 L air sample is described. The sampling is performed with 9-(N-methylaminomethyl)-anthracene (MAMA) adsorbed on a solid sorbent, Amberlite XAD-2. The recoveries are 80–100% in this chemosorption reaction. The urea derivatives are desorbed with N,N-dimethylformamide and analysed by high performance liquid chromatography (HPLC). Samples and prepared chemosorption tubes are stable for at least two weeks if stored in the dark. To complete the investigation, field measurements of TDI were performed in an industrial atmosphere.     

Phenolic compounds in oat grains (Avena sativa L.) grown in conventional and organic systems

The concentrations of avenanthramides (AVAs), hydroxycinnamic acids (HCAs), a sucrose-linked truxinic acid (TASE), and certain agronomic parameters were analyzed in organically and conventionally grown oats. Three cultivars of oats (i.e. Freja, Sang, and Matilda) were grown according to standards for both conventional and organic farming in Sweden, from 1998 to 2000. Two levels of nitrogen (N) and three replicates were included. Overall, there were significant differences between years, cultivars, and N rate for AVA concentration in the grains, but there were no differences in concentration as a consequence of the conventional or organic cropping system used. The AVA content was higher in the samples grown in 2000, particularly in the cultivar Matilda, and was negatively affected by higher N rates. The HCAs showed cultivar and year differences, but were not influenced by N rates or the cropping system. The HCA content was highest in Matilda, and was significantly lower in samples grown in 1999. The concentration of TASE differed only between years, and was about 100% higher in samples from 1999, compared with samples from 1998 and 2000. The AVA and HCA concentrations were negatively correlated to the yield and specific weight of the grains and positively correlated to the protein content. Conversely, the concentration of TASE was positively correlated to the yield. The specific parameters responsible for the variation in the phenolic compounds are not known, but it seems that factors affecting the yield and/or the specific weight also affect the concentrations of AVAs, HCAs, and TASE in oat grains.     

Sublethal toxicity of two wastewater treatment polymers to lake trout fry (Salvelinus namaycush)

Lake trout fry (Salvelinus namaycush) were exposed in laboratory experiments to two wastewater treatment polymers, one anionic (MagnaFloc 156) and one cationic (MagnaFloc 368; Ciba Speciality Chemical), to determine if these chemicals which are used and discharged by mining operations in Canada's North pose a significant hazard to juvenile fishes. The cationic polymer was substantially more toxic to lake trout fry than the anionic polymer, with 96-h LC50 estimates of 2.08 and >600 mg/l, respectively. Separate 30-d exposure experiments yielded no observed and lowest observed effect concentrations, respectively, of 0.25 and 0.5mg/l for MagnaFloc 368, and 75 and 150 mg/l for MagnaFloc 156. In both cases, behavioural responses, especially startle response, were the most sensitive test endpoints. Histopathological assessment revealed that gill pathology appeared within a few days of exposure to both polymers, apparently as a result of localized hypoxia. Acute (4 d) effects included cloudy swelling of epithelial cells, increased gill vascularization, and thickening and shortening of the gill lamella. Chronic (30 d) polymer exposure produced only slightly greater pathological effects than acute exposure, with comparable responses observed only at >1.0mg/l MagnaFloc 368 and 150 mg/l MagnaFloc 156, suggesting that the fish displayed some level of both behavioural and physiological adaptation to the respiratory stress imposed by the two polymers.     

Time of flight secondary ion mass spectrometry studies of the distribution of metals between the soil, rhizosphere and roots of Populus tremuloides Minchx growing in forest soil

Time of flight secondary ion mass spectroscopy has been used to study the metal distribution at the soil/root interface of tree roots extracted from smelter-impacted soils. The results, augmented by scanning electron microscopy, show that the technique is capable of resolving metal distributions at the cellular level. In addition, the distribution of metals between the root plaque and the root interior may be useful in interpreting local metal transport mechanisms.     

Hydrocarbon pollution fixed to combined sewer sediment: a case study in Paris

Over a period of two years (2000-2001), sediment samples were extracted from 40 silt traps (STs) spread through the combined sewer system of Paris. All sediment samples were analysed for physico-chemical parameters (pH, organic matter content, grain size distribution), with total hydrocarbons (THs) and 16 polycyclic aromatic hydrocarbons (PAHs) selected from the priority list of the US-EPA. The two main objectives of the study were (1) to determine the hydrocarbon contamination levels in the sediments of the Paris combined sewer system and (2) to investigate the PAH fingerprints in order to assess their spatial variability and to elucidate the PAH origins. The results show that there is some important inter-site and intra-site variations in hydrocarbon contents. Despite this variability, TH and PAH contamination levels (50th percentile) in the Parisian sewer sediment are estimated at 530 and 18 microg g(-1), respectively. The investigation of the aromatic compound distributions in all of the 40 STs has underlined that there is, at the Paris sewer system scale, a homogeneous PAH background pollution. Moreover, the study of the PAH fingerprints, using specific ratios, suggests the predominance of a pyrolytic origin for those PAHs fixed to the sewer sediment.     

Comparison of different physiological parameter responses in Lemna minor and Scenedesmus obliquus exposed to herbicide flumioxazin

The sensitivity of different physiological parameters in Scenedesmus obliquus and Lemna minor exposed to herbicide (flumioxazin) was investigated to indicate the most convenient and sensitive parameter. To assess toxicity of flumioxazin, we used a panel of biomarkers: pigment contents, chlorophyll fluorescence parameters and antioxidative enzyme activities. Algae and duckweed were exposed to 48-h IC50 for growth rate. In L. minor, the sensitivity of the parameters was as follows: QN > Oxygen emmision > phiS(PSII) > QP > phi(PSII) > CAT, GR > Pigment> APO > Growth. For S. obliquus, this ranking was as follows: CAT > Oxygen emission > QP > APO > GR > Pigment > phiS(PSII) > Growth > phi(PSII) > QN (from the greatest to the least sensitive). The results demonstrated that the observed toxicity is related not only to interspecific variations but also to the selected parameter.     

Roadside particle number distributions and relationships between number concentrations, meteorology, and traffic along a northern California freeway

Particle number distributions were measured simultaneously upwind and downwind of a suburban-agricultural freeway to determine relationships with traffic and meteorological parameters. Average traffic volumes were 6330 vehicles/hr with 10% heavy-duty vehicles, and volumes were higher in July than November. Most downwind particle number distributions were bimodal, with a primary mode at approximately 10-25 nm, indicating that newly formed particles were sampled. Total downwind 6-237 nm particle number concentrations (Ntot) ranged from 9.3 x 10(3) to 2.5 x 10(5) cm(-3), with higher daily average concentrations in November compared with July. Ntot correlated with wind speed, temperature, and relative humidity. Upwind photochemically initiated nucleation likely led to elevated background nanoparticle concentrations in July, as evidenced by increasing upwind distribution modal diameter with increasing temperature and a strong correlation between upwind Ntot and solar radiation. Also in summer, Ntot showed stronger correlation with heavy-duty vehicle volumes than wind speed, temperature, and relative humidity. These results indicate the importance of measuring background particle size distributions simultaneously with roadside distributions. There may be a minimum vehicle volume from which useful real-world vehicle particle number distributions can be measured at roadside, even when collecting samples within 10 m of the traveled lanes.     

Transfer of hexazinone and glyphosate through undisturbed soil columns in soils under Christmas tree cultivation

Field studies monitoring pesticide pollution in the Morvan region (France) have revealed surface water contamination by some herbicides. The purpose of this study was to investigate in greater detail the transport of two herbicides, used in Christmas tree production in the Morvan, under controlled laboratory conditions. Thus, the leaching of hexazinone (3-cyclohexyl-6-dimethyl-amino-1-methyl-1,3,5-triazine-2,4 (1H,3H) dione) and glyphosate (N-(phosphono-methyl-glycine)) through structured soil columns was studied using one loamy sand and two sandy loams from sites currently under Christmas tree cultivation in the Morvan. The three soils were cultivated sandy brunisol [Sound reference base for soils, D. Baize, M.C. Girard (Coord.), INRA, Versailles, 1998, 322 p] or, according to the FAO [FAO, World reference base for soil resources, ISSS-ISRIC-FAO, FAO, Rome, Italy, 1998], the La Garenne was an arenosol and the two other soils were cambisols. The clay contents of the soils ranged from 86 to 156 g kg(-1) and the organic carbon ranged from 98 to 347 g kg(-1). After 160 mm of simulated rainfall applied over 12 days, 2-11% of the applied hexazinone was recovered in the leachate. The recovery was much higher than that of glyphosate, which was less than 0.01%. The greater mobility of hexazinone might be related to its much lower adsorption coefficient, K(oc), 19-300 l kg(-1), compared with 8.5-10231 l kg(-1) for glyphosate (literature values). Another factor that may explain the higher amounts of hexazinone recovered in the leachates of the three soil columns is its greater persistence (19.7-91 days) relative to that of glyphosate (7.9-14.4 days). The mobility of both herbicides was greater in the soils with higher gravel contents, coarser textures, and lower organic carbon contents. Moreover, glyphosate migration seems negatively correlated not only to soil organic carbon, but also to aluminium and iron contents of soils. This soil column study suggests that at the watershed scale, surface water contamination by hexazinone could occur via the horizontal subsurface flow in upper centimeters of soil. In contrast, the surface water contamination with glyphosate by this mechanism appears unlikely.     

Prediction of ozone concentration in ambient air using multivariate methods

Multivariate statistical methods including pattern recognition (Principal Component Analysis--PCA) and modeling (Multiple Linear Regression--MLR, Partial Least Squares--PLS, as well as Principal Component Regression--PCR) methods were carried out to evaluate the state of ambient air in Miskolc (second largest city in Hungary). Samples were taken from near the ground at a place with an extremely heavy traffic. Although PCA is not able to determine the significance of variables, it can uncover their similarities and classify the cases. PCA revealed that it is worth to separate day and night data because different factors influence the ozone concentrations during all day. Ozone concentration was modeled by MLR and PCR with the same efficiency if the conditions of meteorological parameters were not changed (i.e. morning and afternoon). Without night data, PCR and PLS suggest that the main process is not a photochemical but a chemical one.