Spatial differences in ambient coarse and fine particles in the Monterrey metropolitan area,Mexico: Implications for source contribution

The ambient air of the Monterrey Metropolitan Area (MMA) in Mexico frequently exhibits high levels of PM₁₀ and PM_2.5. However, no information exists on the chemical composition of coarse particles (PM_c = PM₁₀ – PM_2.5). A monitoring campaign was conducted during the summer of 2015, during which 24-hr average PM₁₀ and PM_2.5 samples were collected using high-volume filter-based instruments to chemically characterize the fine and coarse fractions of the PM. The collected samples were analyzed for anions (Cl^–, NO₃^–, SO₄^2–), cations (Na⁺, NH₄⁺, K⁺), organic carbon (OC), elemental carbon (EC), and 35 trace elements (Al to Pb). During the campaign, the average PM_2.5 concentrations did not showed significance differences among sampling sites, whereas the average PM_c concentrations did. In addition, the PM_c accounted for 75% to 90% of the PM₁₀ across the MMA. The average contribution of the main chemical species to the total mass indicated that geological material including Ca, Fe, Si, and Al (45%) and sulfates (11%) were the principal components of PM_c, whereas sulfates (54%) and organic matter (30%) were the principal components of PM_2.5. The OC-to-EC ratio for PM_c ranged from 4.4 to 13, whereas that for PM_2.5 ranged from 3.97 to 6.08. The estimated contribution of Secondary Organic Aerosol (SOA) to the total mass of organic aerosol in PM_2.5 was estimated to be around 70–80%; for PM_c, the contribution was lower (20–50%). The enrichment factors (EF) for most of the trace elements exhibited high values for PM_2.5 (EF: 10–1000) and low values for PM_c (EF: 1–10). Given the high contribution of crustal elements and the high values of EFs, PM_c is heavily influenced by soil resuspension and PM_2.5 by anthropogenic sources. Finally, the airborne particles found in the eastern region of the MMA were chemically distinguishable from those in its western region.

Implications: Concentration and chemical composition patterns of fine and coarse particles can vary significantly across the MMA. Public policy solutions have to be built based on these observations. There is clear evidence that the spatial variations in the MMA’s coarse fractions are influenced by clearly recognizable primary emission sources, while fine particles exhibit a homogeneous concentration field and a clear spatial pattern of increasing secondary contributions. Important reductions in the coarse fraction can come from primary particles’ emission controls; for fine particles, control of gaseous precursors—particularly sulfur-containing species and organic compounds—should be considered.     

Comparison of quantitation of polychlorinated dibenzodioxins and polychlorinated dibenzofurans in complex environmental samples by high resolution gas chromatography with flame ionization, electron capture and mass spectrometric detection

A complete separation of PDDD and PCDF from a complex sample matrix by a two-step HPLC clean-up procedure shows the feasibility of analysis of PCDD and PCDF using less expensive instruments. This is demonstrated by a comparison of quantitative results of PCDD and PCDF in a complex flyash sample analyzed using GC/FID, GC/ECD, and GC/MSD.     

An analytical method to determine Henry's law constant for selected volatile organic compounds at concentrations and temperatures corresponding to tap water use

Henry's law constants (H) are needed to model human exposure to Volatile Organic Compounds (VOCs) in indoor air resulting from the use of tap water. This paper presents an experimental method to determine Hs for several common tap water pollutants at concentrations and temperatures used in household water. For 5 VOCs Henry's law constants were obtained simultaneously over the 25 degrees C to 45 degrees C temperature range, providing data on H beyond the currently available data (up to 35 degrees C). Henry's law constants were obtained as the ratio of equilibrium concentrations of VOCs in air and water, using simultaneous sampling from sealed bottles kept at constant temperatures. Air and water samples were concentrated by a purge-and-trap method, thermally desorbed from a Tenax trap, and analyzed with a gas chromatograph with an electron capture detector (GC-ECD). Experimental results agreed well with available literature data.     

Microbial kinetic analysis of three different types of EBNR process

The disadvantages of developed biological nutrient removal (BNR) processes (additional energy for liquid circulation and addition of external carbon substrate for denitrification in anoxic zones) were improved by reconfiguring the process into (1) an anaerobic zone followed by multiple stages of aerobic-anoxic zones (TNCU3 process) or (2) anaerobic, oxic, anoxic, oxic zones in sequence (TNCU2 process). These two pilot plants were operated at a recycling sludge ratio of 0.5 without internal recycle of nitrified supernatant. The sludge retention time was maintained at 10 d. The main objective of this study is to analyze the kinetics of different microorganisms in these two processes and A2O process by using the Activated Sludge Model No. 2d. The effective removal efficiency of carbon, total phosphorus and total nitrogen at 87-98%, 92-100% and 63-80%, respectively, were achieved in the testing runs. According to model simulations, the microbial kinetics in the TNCU3 and TNCU2 processes would be affected by different operations. When the step feeding strategy was adopted, the HRT was longer due to the less influent flowrate in the front stages and the microbes would grow in quantities by about 6% in the aerobic reactors. In the followed anoxic reactors, the microbes would decrease in quantities by about 12% due to the dilution effect. The dilution effects in TNCU3 and TNCU2 processes did not take place in A2O process because the recycling mixed liquid from the aerobic reactor to the anoxic reactor still contained particulate components. The XH, XPAO, and XAUT concentrations in the effluent of the last tank were lower when the step-feeding mode was adopted. The TNCU3 and TNCU2 processes could be operated efficiently without nitrified liquid circulation and addition of external carbon substrate for denitrification.     

Methane mass balance at three landfill sites: What is the efficiency of capture by gas collection systems?

Many developed countries have targeted landfill methane recovery among greenhouse gas mitigation strategies, since methane is the second most important greenhouse gas after carbon dioxide. Major questions remain with respect to actual methane production rates in field settings and the relative mass of methane that is recovered, emitted, oxidized by methanotrophic bacteria, laterally migrated, or temporarily stored within the landfill volume. This paper presents the results of extensive field campaigns at three landfill sites to elucidate the total methane balance and provide field measurements to quantify these pathways. We assessed the overall methane mass balance in field cells with a variety of designs, cover materials, and gas management strategies. Sites included different cell configurations, including temporary clay cover, final clay cover, geosynthetic clay liners, and geomembrane composite covers, and cells with and without gas collection systems. Methane emission rates ranged from -2.2 to >10,000 mg CH(4) m(-2) d(-1). Total methane oxidation rates ranged from 4% to 50% of the methane flux through the cover at sites with positive emissions. Oxidation of atmospheric methane was occurring in vegetated soils above a geomembrane. The results of these studies were used as the basis for guidelines by the French environment agency (ADEME) for default values for percent recovery: 35% for an operating cell with an active landfill gas (LFG) recovery system, 65% for a temporary covered cell with an active LFG recovery system, 85% for a cell with clay final cover and active LFG recovery, and 90% for a cell with a geomembrane final cover and active LFG recovery.     

Distribution of uranium contamination in weathered fractured saprolite/shale and ground water

The objective of this study was to determine how structure, stratigraphy, and weathering influence fate and transport of contaminants (particularly U) in the ground water and geologic material at the Department of Energy (DOE) Environmental Remediation Sciences Department (ERSD) Field Research Center (FRC). Several cores were collected near four former unlined adjoining waste disposal ponds. The cores were collected, described, analyzed for U, and compared with ground water geochemistry from surrounding multilevel wells. At some locations, acidic U-contaminated ground water was found to preferentially flow in small remnant fractures weathering the surrounding shale (nitric acid extractable U [U(NA)] usually < 50 mg kg(-1)) into thin (<25 cm) Fe oxide-rich clayey seams that retain U (U(NA) 239 to 375 mg kg(-1)). However, greatest contaminant transport occurs in a 2 to 3 m thick more permeable stratigraphic transition zone located between two less permeable, and generally less contaminated zones consisting of (i) overlying unconsolidated saprolite (U(NA) < 0.01 to 200 mg kg(-1)) and (ii) underlying less-weathered bedrock (U(NA) generally < 0.01 to 7 mg kg(-1)). In this transition zone, acidic (pH < 4) U-enriched ground water (U of 38 mg L(-1)) has weathered away calcite veins resulting in greater porosity, higher hydraulic conductivity, and higher U contamination (U(NA) 106 to 745 mg kg(-1)) of the weathered interbedded shale and sandstone. These characteristics of the transition zone produce an interval with a high flux of contaminants that could be targeted for remediation.     

Polychlorinated biphenyls in polysulfide sealants--occurrence and emission from a landfill station

Approximately 80,000 kg polysulfide sealant containing 10,000-18,000 kg polychlorinated biphenyls (PCB) was deposited at a Swedish municipal landfill station during 1965-1973. Investigations during 1994 showed that soil layers underneath the landfill had concentration of PCB not alarmingly high. The concentration of PCB congeners in ground water samples was elevated 4-750 times compared to a reference sample. Based on samples of ground water, leachate water, and flux chambers measuring evaporation of PCB from the landfill surface, the emission of PCB was estimated to be 1 g sigmaPCB/yr. This very low rate was attributed to the high sorptive capacity of the sealant. Compared to a reference site, the evaporation flux was elevated for the most volatile congeners, but factors 20-1400 lower than from another landfill which was contaminated with PCB in paper-pulp fibres.     

Genetic divergence between two morphologically similar varieties of the kuruma shrimp<Emphasis Type="Italic"> Penaeus japonicus</Emphasis>

The kuruma shrimp Penaeus japonicus is widely distributed throughout the Indo-West Pacific. Two morphologically similar varieties, I and II, are recognized from the South China Sea. The two varieties are characterized by different color banding patterns on the carapace, but there are no distinct differences in morphometric traits between them based on measurement of 13 characters. Sequence data and restriction profiles of the mitochondrial genes reveal that these two varieties represent distinct clades, with sequence divergences of about 1% (473 bp) in 16S rRNA, 6–7% (504 bp) in cytochrome oxidase I, and 16–19% (470 bp) in the control region. Analysis of amplified fragment length polymorphism confirms that the two varieties are genetically distinct. We also investigated the geographical distribution of the two varieties in the western Pacific by analyzing specimens collected from Japan and Singapore. Shrimps from Japan and Singapore have been found to belong to varieties I and II, respectively, suggesting that the two varieties have different geographical distribution. Phylogenetic study reveals that the two varieties are more closely related to each other than to the other phylogenetically related Penaeus species. Results from this study suggest the occurrence of two cryptic species in the kuruma shrimp P. japonicus.Communicated by M.S. Johnson, Crawley     

Improvement of Waste Recycling in PET Fiber Production

Production of polyethylene teraphtalate (PET) fiber in the world is increasing every year and reached to an amount of about 20 million tons a year in 2001. The wastes occur in the production of PET fiber in the amount of about 3–5% of total production. The PET does not degrade for a long time in nature. Since PET is a derivative of petroleum, the wastes of PET are valuable and must be recycled. One of the recycling method of PET wastes is re-melting. Thus, various properties of the PET wastes were improved using the re-melting method by employing an extruder manufactured for the work. Degradation during re-melting decreases the properties of the final product. The results indicate that the properties of recycled PET wastes can be monitored by designing the parameters of the extruder. Also, the further degradation of the material can be prevented and the recycling costs are minimized.     

Quantifying dry NH3 deposition to an ombrotrophic bog from an automated NH3 field release system

Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH₃ inputs to moorland vegetation growing on a bog at a field scale, a field release NH₃ fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH₃ from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s^–1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH₃ concentration with distance from the source. In a complementary study, using a NH₃ flux chamber system, the relationships between NH₃ concentrations and cuticular resistances were quantified for a range of NH₃ concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH₃ concentration from 11 s m^–1 at 3.0 g m^–3 to 30 s m^–1 at 30 g m^–3. The NH₃ concentration data and the concentration-dependent canopy resistance are used to calculate NH₃ deposition taking into account leaf surface wetness. The implications of using an NH₃ concentration-dependent cuticular resistance and the importance for refining critical loads are discussed.