Design and laboratory testing of a new flow-through directional passive air sampler for ambient particulate matter

A new type of directional passive air sampler (DPAS) is described for collecting particulate matter (PM) in ambient air. The prototype sampler has a non-rotating circular sampling tray that is divided into covered angular channels, whose ends are open to winds from sectors covering the surrounding 360°. Wind-blown PM from different directions enters relevant wind-facing channels, and is retained there in collecting pools containing various sampling media. Information on source direction and type can be obtained by examining the distribution of PM between channels. Wind tunnel tests show that external wind velocities are at least halved over an extended area of the collecting pools, encouraging PM to settle from the air stream. Internal and external wind velocities are well-correlated over an external velocity range of 2.0-10.0 m s?1, which suggests it may be possible to relate collected amounts of PM simply to ambient concentrations and wind velocities. Measurements of internal wind velocities in different channels show that velocities decrease from the upwind channel round to the downwind channel, so that the sampler effectively resolves wind directions. Computational fluid dynamics (CFD) analyses were performed on a computer-generated model of the sampler for a range of external wind velocities; the results of these analyses were consistent with those from the wind tunnel. Further wind tunnel tests were undertaken using different artificial particulates in order to assess the collection performance of the sampler in practice. These tests confirmed that the sampler can resolve the directions of sources, by collecting particulates preferentially in source-facing channels.     

The molecular composition of humic substances extracted from green composts and their potential for soil remediation

Humic substances play empirically several essential functions in biogeochemical cycles such as storage of carbon, pollutants, nutrients and water, yet the underlying mechanisms remain poorly known because their precise molecular structure is largely unknown so far. Here, we extracted humic substances from biomass waste of bell pepper, fennel, artichoke, coffee ground, coffee husks, and nursery residues. We analyzed humic extracts by ultra-high resolution Orbitrap Fusion Lumos Tribrid 1 M mass spectrometry, using both positive photoionization and negative electrospray ionization modes, and by ¹³C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy. We identified 5000–7000 unique organic compounds in humic substances by integrating photoionization with electrospray ionization. The chemical distribution of all components was depicted by nuclear magnetic resonance. Humic substances from green composts are composed by a wide variety of hydrophilic and hydrophobic moieties, thus providing the required biosurfactant properties for effective soil washing capacities, with carboxyl-rich alicyclic molecules, fatty acids, and phenolic acids as major constituents. Overall, our findings provide a major insight in the molecular structure of humic substances, thus opening research on mechanisms ruling the origin, fate and behavior of humic substances.

     

A case study of social behaviour in a natural disaster: the olivares landslide (Spain)

The modern sociological literature on disasters highlights the fact that many of the ideas about human behaviour in disasters which were long considered as valid, are wrong. The main discovery is based on the fact that situations of crisis increase people's moral principles and capability of response. This paper illustrates some of these ideas, in a case study of a village which was struck by a natural disaster in the north of Granada (Spain) in 1986. The population's attitude revealed a huge potential of resources that were underestimated by professionals of disaster management. The analysis shows that it is necessary to bring civil protection systems and the population's capability of response into close harmony.     

Variation in some chemical parameters and organic matter in soils regenerated by the addition of municipal solid waste

The organic fraction of a municipal solid waste was added in different doses to an eroded soil formed of loam and with no vegetal cover. After three years, the changes in macronutrient content and the chemical-structural composition of its organic matter were studied. The addition of the organic fraction from a municipal solid waste had a positive effect on soil regeneration, the treated soils being covered with spontaneous vegetation from 1 yr onwards. An increase in electrical conductivity and a fall in pH were noted in the treated soils as were increases in macronutrients, particularly N and available P and the different carbon fractions. Optical density measurements of the organic matter extracted with sodium pyrophosphate showed that the treated soils contained an organic matter with less condensed compounds and with a greater tendency to evolve than the control. A pyrolysis-gas chromatography study of the organic matter extracted with pyrophosphate showed large quantities of benzene both in the treated soils and control; pyrrole was also relatively abundant, although this fragment decreased as the dose rose. Xylenes and pyridine were present in greater quantities in the control and furfural in the treated soils. Three years after addition to the soil, the organic matter had a higher proportion of fragments derived from aromatic compounds and a smaller proportion derived from hydrocarbons. Similarity indices showed that, although the added and newly formed organic matter 3 yr after addition continued to differ from that of the original soil and to be more mineralizable, the transformations it has undergone made it more similar to the original organic matter of the soil than it was at the moment of being added.     

Comparison between chemical and isotopic measurements of biological nitrate utilization: further evidence of low new-production levels in the equatorial Pacific

New-production (nitrate uptake) rates in the equatorial Pacific were estimated by parallel measurements of nitrate disappearance from sea water using a colorimetric method and of ¹⁵N-labelled nitrate (¹⁵NO₃ ⁻) incorporation into particulate organic nitrogen (PON) collected on GF/F filters (net nitrate uptake, conventional ¹⁵N-tracer method) and Anopore (0.2 μm) membranes. Regression analyses of 74 sample pairs gathered during 12 and 24 h productivity experiments revealed a significant positive relationship between decreasing nitrate level and ¹⁵NO₃ ⁻ accumulation into PON retained on GF/F filters, but the slopes of Model I and Model II regression lines were 1.18 and 1.29, respectively, suggesting that 15 to 22% of ¹⁵NO₃ ⁻ removed from the dissolved fraction were lost to another N-pool. Two possible avenues for the missing ¹⁵NO₃ ⁻ have been examined: uptake by submicron particles passed through the GF/F filters, and loss as dissolved organic nitrogen (DON). Nitrate uptake by small cells not recovered on GF/F filters, could be safely eliminated as a cause of loss, since ¹⁵NO₃ ⁻ uptake rates obtained from ¹⁵N entering PON collected on GF/F filters agreed well with those obtained from ¹⁵N entering PON collected on Anopore membranes (32 sample pairs). Inspection of the DON pool of 0.2 μm filtrates for excess-¹⁵N enrichment (20 samples) revealed that in nitrate-rich waters (equatorial upwelling between 1°N and 10°S), loss of ¹⁵NO₃ ⁻ as DO¹⁵N accounted for <5% of net nitrate uptake. In samples from subtropical oligotrophic waters (from 11°S southward), however, ¹⁵NO₃ loss as DO¹⁵N represented up to 20% of net NO₃ ⁻ uptake. These results, as well as experimental considerations concerning the use of colorimetric and isotopic methods to measure new production show that: (1) earlier reported high discrepancies between nitrate decreases (ΔNO₃ ⁻) and ¹⁵NO₃ ⁻ incorporation into filterable particles (ΔNO₃ ⁻/¹⁵NO₃ ⁻ incorporation >2) were probably erroneous; (2) the use of GF/F filters does not result in an underestimation of new production, although it was found to underestimate PON concentrations by up to 60%; (3) in the equatorial upwelling area (1°N to 10°S), which has high ambient nitrate levels (>2000 nmol l⁻¹) but only slight changes in concentration (0 to 80 nmol l⁻¹ d⁻¹), new production is more accurately estimated by the isotopic method than by the chemical method; (4) in subtropical oligotrophic waters (from 11°S southward) with low ambient nitrate levels (0 to 100 nmol l⁻¹), both procedures are appropriate as long as nitrate removal per incubation period is >3 nmol l⁻¹ (lower rates are only detectable with the isotopic method); (5) the traditional ¹⁵N-tracer technique does not substantially underestimate net new-production in the equatorial Pacific, and failure to account for the loss of ¹⁵NO₃ ⁻ as DON, i.e. to estimate gross nitrate uptake (gross uptake = net uptake + ¹⁵N loss) tends to underestimate new production on an average by only 10%. Overall, the apparent low level of new production in the nitrate-rich area of the central equatorial Pacific seems to be a fact, and may be ascribable to other nutrient (macro and micro) deficiencies and/or to intense in situ recycling of ammonium and nitrate (regenerated production) rather than to inaccurate nitrate uptake rates measured with the classical ¹⁵N-tracer technique. Received: 24 November 1998 / Accepted 10 March 2000     

Trace gases and particulate matter emissions from wildfires and agricultural burning in Northeastern Mexico during the 2000 fire season

An inventory of air pollutants emitted from forest and agricultural fires in Northeastern Mexico for the period of January to August of 2000 is presented. The emissions estimates were calculated using an emissions factor methodology. The inventory accounts for the emission of carbon monoxide (CO), methane, nonmethane hydrocarbons, ammonia, nitrogen oxides, and particulate matter (PM). Particulate matter emissions include estimates for fine PM and coarse PM. A total of 2479 wildfires were identified in the domain for the period of interest, which represented approximately 810,000 acres burned and 621,130 short tons emitted (81% being CO). The main source of information used to locate and estimate the extent of the fires came from satellite imagery. A geographic information system was used to determine the type of vegetation burned by each fire. More than 54% of the total area burned during the period of study was land on the State of Tamaulipas. However, >58% of the estimated emissions came from the State of Coahuila. This was because of the mix of vegetation types burned in each state. With respect to the temporal distribution, 76.9% of the fires occurred during the months of April and May consuming almost 78% of the total area burned during the period of study. Analysis of wind forward trajectories of air masses passing through the burned areas and 850-mb wind reanalyses indicate possible transboundary transport of the emissions from Mexico to the United States during the occurrence of the major wildfires identified.     

Evaluation of heavy metal availability in polluted soils by two sequential extraction procedures using factor analysis

Superficial soil and grass samples from 13 locations affected by several anthropogenic sources (mining, metal factory, traffic emissions) were collected in Gipuzkoa, northern Spain. The more labile metal fractions, the mobile (extracted by 0.01 mol l(-1) CaCl(2)) and the mobilisable (extracted by 0.005 mol l(-1) DTPA), were evaluated using a short sequential procedure with two steps. From the results a short-medium term potential lability of Cd, Cu, Zn and Pb can be concluded. The labile levels were compared with the results obtained using the Tessier sequential procedure. Factor analysis was used to check the associations between the total metal contents in soil and grass, as well as between the levels of the different sequential fractions and the total content in grass. Cd, Cu and Zn labile levels were related to total metal grass contents indicating its suitability for the availability studies in polluted soil-plant system.     

Structure-activity relationships for association of linear alkylbenzene sulfonates with activated sludge

Sorption of linear alkylbenzene sulfonates (LAS) on sludge particles from wastewater treatment plants was studied. The effect of alkyl chain length and the water hardness were investigated. Sorption on sludge increases with increasing alkyl chain length in the LAS molecules. The results are interpreted in terms of a hydrophobic bonding mechanism being the critical micelle concentration a good index of the surfactant hydrophobicity. The increase in free energy of adsorption for the addition of successive methylene groups to the alkyl chain was estimated as 2.4 kJ/mol. Water hardness clearly enhances the sorption of LAS homologues on sludge and seems to promote cooperative sorption at high surfactant and calcium ion concentrations. An empirical equation was provided that allow to estimate the partition coefficient between aqueous and solid phases for LAS homologues as a function of the alkyl chain length and the water hardness.     

Trophic relationships in the recently impounded Bagré reservoir in Burkina Faso

The trophic dynamics of Bagré reservoir which has been recently impounded in Burkina Faso was based on the data collected during 1997–1998 period using the Ecopath model and software. Total fish biomass is 22.63 t km⁻² and mainly represents trophic levels (TLs) 2 and 3. The trophic food chain is relatively long and the overall transfer efficiency is quite low. Grazing foodweb based on primary producers is prominent in the reservoir ecosystem and detritus plays a less significant role. Seasonal and long-term variations in water quality have significant influences on the lower TLs clearly showing a bottom-up functioning of the ecosystem. Environmental degradations, such as siltation occurring in the lake, suggest possible risks in limiting ecosystem productivity.     

A cost worth paying: energetically expensive interactions with males protect females from intrasexual aggression

When approached by males, females of the Amarillo fish (Girardinichthys multiradiatus) perform a behaviour called vibration or they are aggressively challenged. We quantified vibration and assessed whether it compromises the rate of feeding attempts in dyads kept in outdoor enclosures. Male approaches resulted in female vibration and in a reduced feeding rate. Vibration was not evoked by female–female aggression, which was frequent and always ended in the subordinate fleeing from the dominant female. Using a closed respirometer we found that vibration is costly; oxygen consumption of females was greater in the presence of a male (which evoked vibration) than in the presence of a non-familiar female (when no vibration occurred). By recording interactions of females confined in aquaria in the presence and in the absence of males, we confirmed that escaping is the only available response to deal with female aggression. Females kept without males participated in frequent aggressive (even lethal) interactions that did not abate while the subordinate female was in sight of the dominant, and which caused premature births and injuries. Yet in the alternative treatment aggression ceased when a male approached, prompting vibration in both females. Thus, in the Amarillo, in as much as it evokes energetically costly female vibrations, male courtship is an expression of sexual conflict. However, in the absence of males, frequent female aggression potentially annuls the benefits of not vibrating. We propose that a complete appraisal of the consequences of sexual conflict must include an assessment of the costs imposed by intra-sexual interactions.