Determination of Motor Vehicle Profiles for Non-Methane Organic Compounds in the Mexico City Metropolitan Area

ABSTRACT

Non-methane organic compound (NMOC) profiles for on-road motor vehicle emissions were measured in a downtown tunnel and parking garages in Mexico City during 1996. Hydrocarbon samples from the tunnel and ambient air samples (C2-C12) were collected using stainless steel canisters, and carbonyl compounds were collected using 2,4-dinitrophenylhydrazine (DNPH) impregnated cartridges. Canister samples were analyzed by gas chromatog-raphy/flame ionization detection (GC/FID) to ascertain detailed hydrocarbon composition. DNPH samples were analyzed by high performance liquid chromatography (HPLC). NMOC source profiles were quantified for evaporative emissions from refueling, cold start, and hot soak, and on-road operating conditions. The ultimate purpose will be to determine the apportionment of ambient NMOC concentrations using the Chemical Mass Balance (CMB) model. The tunnel profile contained 42.3 ppbC% of alkanes, 20.6 ppbC% of unsaturated compounds, and 22.4 ppbC% of aromatics. The most abundant species were acetylene with 7.22 ppbC%, followed by ipentane with 5.69 ppbC%, and toluene with 5.42 ppbC%. These results were compared with those from studies in the United States. The cold start profile was found to be similar to the tunnel profile, although there were differences in the content of acetylene, isopentane, and oxygenates. The abundance of saturated NMOC in the hot soak profile was similar to gasoline head space profiles; it was also much larger than saturated NMOC in the roadway profile.     

Electrical resistivity tomography as monitoring tool for unsaturated zone transport: an example of preferential transport of deicing chemicals

Non-invasive spatially resolved monitoring techniques may hold the key to observe heterogeneous flow and transport behavior of contaminants in soils. In this study, time-lapse electrical resistivity tomography (ERT) was employed during an infiltration experiment with deicing chemical in a small field lysimeter. Deicing chemicals like potassium formate, which frequently impact soils on airport sites, were infiltrated during snow melt. Chemical composition of seepage water and the electrical response was recorded over the spring period 2010. Time-lapse electrical resistivity tomographs are able to show the infiltration of the melt water loaded with ionic constituents of deicing chemicals and their degradation product hydrogen carbonate. The tomographs indicate early breakthrough behavior in parts of the profile. Groundtruthing with pore fluid conductivity and water content variations shows disagreement between expected and observed bulk conductivity. This was attributed to the different sampling volume of traditional methods and ERT due to a considerable fraction of immobile water in the soil. The results show that ERT can be used as a soil monitoring tool on airport sites if assisted by common soil monitoring techniques.     

Uptake of heavy metals by some edible vegetables irrigated using wastewater: a preliminary study in Accra, Ghana

The heavy metals (Fe, Zn, Pb, Ni, Cr, Co, and Cd) burden in wastewater, soil, and vegetable samples from a wastewater irrigated farm located at KorleBu, Accra has been investigated. Flame atomic absorption spectrometry after microwave digestion using a combination of HNO₃, HCl, and H₂O₂ (for water), and HNO₃ and HCl (for soil and vegetables). The mean concentrations (in milligrams per kilogram) of heavy metals in the soil samples were in the order of Fe (171?±?5.22)?>?Zn (36.06?±?4.54)?>?Pb (33.35?±?35.62)?>?Ni (6.31?±?8.15)?>?Cr (3.40?±?3.63)?>?Co (1.36?±?0.31)?>?Cd (0.43?±?0.24), while the vegetables were in the order of Fe (183.11?±?161.2)?>?Zn (5.38?±?3.50)?>?Ni (3.52?±?1.27)?>?Pb (2.49?±?1.81)?>?Cr (1.46?±?0.51)?>?Co (0.66?±?0.25)?>?Cd (0.36?±?0.15). The bioconcentration factors suggest environmental monitoring for the heavy metals as follows: Cd (0.828), Cr (0.431), Ni (0.558), Co (0.485), and Fe (1.067). Estimated daily intakes were very low for both children and adults except Fe (0.767 mg/kg/day) in children. The population that consume vegetables from the study area were, however, estimated to be safe based on the results obtained from the health risk index, which were all?<?<1. The sodium absorption ratio according to FAO (1985) classifications indicate that the wastewater in the study area is unsuitable for irrigation purposes.     

Quantification and source identification of polycyclic aromatic hydrocarbons in sediment, soil, and water spinach from Hanoi, Vietnam

Polycyclic aromatic hydrocarbons (PAHs) were quantified in sediment, soil, and plant material from Hanoi, Vietnam, and an aquatic production system in peri-urban Hanoi. The sum of the concentration of 16 US-EPA priority PAHs ( summation PAH16) ranged between 0.44 and 6.21 mg kg(-1) dw in sediment and between 0.26 and 1.35 mg kg(-1) dw in soil, with decreasing concentrations from the urban area to the peri-urban area, indicating contributions from urban and industrial sources. Double plots of diagnostic source ratios indicate that PAHs originate from mixed petrogenic and pyrogenic sources, the latter being predominant. The predominance of low molecular weight (LMW) PAHs in the sediment samples suggests that petrogenic sources are more prevalent in the water environment than in the soil. In contrast, high molecular weight (HMW) PAHs dominated in water spinach which probably reflects the plant's uptake of particle-bound PAHs that originate from pyrogenic sources.     

Minimization of the environmental impact of chrome tanning: a new process with high chrome exhaustion

In all tanning technology operations wastes are generated. These reach the environment as residual waters, solid and liquid waste as well as atmospheric emissions and odours.

This study tests an alternative method to the traditional tanning method at an industrial level. The new method is based on tanning without float and by significantly increasing the temperature at the end of the tanning process. The properties of the leathers obtained using the two methods have been compared and the results indicate that those leathers have similar physical, chemical, and organoleptic properties. However, the differences existing from the environmental point of view are significant. It is not necessary to use clean water for this tanning. Moreover, there is a 75% reduction of the residual float, a 91% reduction of the chrome discharged, and a 94% reduction of the chlorides discharged. A financial assessment was carried out to demonstrate that the newly proposed system is 32% more economic than the traditional one.     

The influence of subordinate age on managerial actions: An attributional analysis

The present research examined the effects of employee age on managers attributions and actions toward subordinates. The major prediction was that managers attributions would mediate the effects of age on managerial actions. One-hundred and twenty-four undergraduate management students participated in a laboratory experiment in which subordinate age (30 versus 60 years) and performance (high versus low) were manipulated. A laboratory study was conducted so that subordinate credentials and performance levels could be controlled. Analyses indicated that poor performance by older subordinates was attributed more to stable factors than similar performance by younger subordinates. In addition, job simplification was rated as more appropriate and training was recommended as less appropriate for older subordinates. A series of hierarchical regression analyses indicated that the differences in managerial actions were a function of subjects' attributional patterns. Implications of the findings for practice and future research are discussed.     

Analysis of maternal serum alpha-fetoprotein and free beta human chorionic gonadotrophin in the first trimester: Implications for down's syndrome screening

The aim of this study was to determine the maternal population, pregnancy, serum alpha-fetoprotein (AFP) and free β subunit of human chorionic gonadotrophin (FβhCG) parameters in a large series of women attending prenatal clinics before 15 weeks' gestation and to assess the practical problems of population screening for Down's syndrome in the first trimester using these markers. Serum samples were collected from 8600 women attending prenatal clinic booking visits. Maternal serum AFP and FβhCG medians were calculated for each day of gestation (49–104 days), using both dates and ultrasound estimates of gestation. The effects of maternal weight, twin pregnancies, and threatened abortion on AFP and FβhCG levels were analysed. The median age of the population was 27.1 years and the median weight 62.1 kg. Twenty-six per cent of samples were collected before 70 days and 50 per cent before 78 days' gestation. Eighty-nine per cent of all samples had gestational estimates by dates, 60 per cent by ultrasound and 52 per cent by both dates and ultrasound. The AFP median was 5 kU/1 at 49 days, 5.9 kU/1 at 70 days, and 17.9 kU/1 at 100 days. The peak median FβhCG level was 66.4 ng/ml at 64 days, falling to 20.6 ng/ml at 100 days' gestation. Both AFP and FβhCG levels showed log Gaussian distributions but the standard deviation for AFP was 20 per cent greater than that found in the second trimester. AFP and FβhCG levels showed an inverse relationship with maternal weight and were increased in twin pregnancies (1.68 and 1.97 multiples of the median, respectively). AFP and FβhCG can be readily measured in a large screening population in the first trimester. Down's syndrome screening protocols based on these markers could be refined by the use of gestations in individual days but AFP is likely to be a less effective marker and detection rates are likely to be lower than in the second trimester. To realize the potential of first-trimester screening, more women should be encouraged to attend the prenatal clinic in early pregnancy and ultrasound dating should be carried out for all pregnancies at this stage.     

Trimethylamine abatement in algal-bacterial photobioreactors

Trimethylamine (TMA) is an odorous volatile organic compound emitted by industries. Algal-based biotechnologies have been proven as a feasible alternative for wastewater treatment, although their application to abate polluted air emissions is still scarce. This work comparatively assessed the removal of TMA in a conventional bacterial bubble column bioreactor (BC) and a novel algal-bacterial bubble column photobioreactor (PBC). The PBC exhibited a superior TMA abatement performance compared to the conventional BC. In this sense, the BC reached a removal efficiency (RE) and an elimination capacity (EC) of 78% and 12.1 g TMA m^?3 h^?1, respectively, while the PBC achieved a RE of 97% and a EC of 16.0 g TMA m^?3·h^?1 at an empty bed residence time (EBRT) of 2 min and a TMA concentration ~500 mg m^?3. The outstanding performance of the PBC allowed to reduce the operating EBRT to 1.5 and 1 min while maintaining high REs of 98 and 94% and ECs of 21.2 and 28.1 g m^?3·h^?1, respectively. Moreover, the PBC improved the quality of the gas and liquid effluents discharged, showing a net CO₂ consumption and decreasing by ~ 30% the total nitrogen concentration in the liquid effluent via biomass assimilation. A high specialization of the bacterial community was observed in the PBC, Mumia and Aquamicrobium sp. being the most abundant genus within the main phyla identified.

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Fate of methidathion residues in biological waste during anaerobic digestion

The aim of this study was to examine the fate of the organothiophosphorus pesticide methidathion during anaerobic digestion of biological waste. Three reactor experiments were conducted under various conditions of temperature, pH and retention time. The influence of pH and temperature as well as the partitioning between solid and aqueous phase were studied in batch experiments. The mesophilic (25, 35 degrees C) reactor experiments showed a decline to about 10% of the maximum methidathion concentration within 30-80 d. In the thermophilic (55 degrees C) reactor experiment, methidathion disappeared within 20 d. The batch experiments showed an abiotic hydrolysis of methidathion over the experiment period of 4 d, accelerated by alkaline conditions (pH 10.5 and 12.8) and high temperatures (55 degrees C). The hydrolysis was also noticeable at a neutral pH, while methidathion was most stable at weakly acid pH values. Methidathion bonded strongly to the biological waste, and the amount released into the water phase was below the maximum aqueous solubility. About 10% of methidathion remained non-extractable. High concentrations of dissolved organic carbon and yeast extract as a model substance for disintegrated cells further reduced the content of methidathion in the water phase, possibly caused by co-sorption to the solid organic matter.