Loss Of Particulate Matter Research Articles

Experimental study on particulate matter emissions in a lab-scale pressurized reactor

Pressurized oxy-combustion (POC) is a promising carbon capture and storage (CCS) technology to improve the process efficiency and economics as compared with first-generation oxy-combustion. However, compared with traditional air combustion, pollutant emissions would be significantly changed in pressurized conditions, and the sampling method has always been disputed. A novel particulate matter (PM) sampling system, consisting of a pressurized PM10 cyclone, a three-stage aerosol dilution system, and a depressurization device was developed to investigate PM emissions at elevated pressure. After being depressurized, PM10 size distribution in the flue gas was measured by using an Electrical Low-Pressure Impactor plus (ELPI+). The PM losses in three depressurization devices were evaluated. Results show that, compared to a needle or ball valve as a pressure regulator, the designed nozzle performed better in terms of controlling system pressure and reducing PM loss in the channel. The sampling system was then used to evaluate the effect of pressure on PM formation. At pressure, there is a greater production of PM below 30 nm, while the generation of coarse mode PM is reduced. Sulfur-based compounds in the combusting particles are prone to be evaporated into the gas phase at higher pressure, which contributes to the formation of fine mode PM, while Fe, Si, and Ca are reduced significantly. The coarse mode PM is reduced at higher pressure, which is mainly due to the weak fragmentation; as a result, more PM is captured in the PM10 cyclone. Compared with O2-N2 conditions, the O2-CO2 conditions can promote the formation of the fine mode PM.

No‐till marginally mitigates the impact of harvesting corn stover on soil microbial parameters

AbstractHarvesting corn stover can negatively impact soil chemical and physical properties, but less is known regarding its effects on soil microbiology. We evaluated the impact of corn (Zea mays L.) stover removal level (SRL) on soil microbial biomass (MB) and extracellular enzyme activities (EEAs) in irrigated, continuous corn located in eastern Nebraska. Soil fatty acid‐methyl esters (FAMEs) and EEA of eight soil enzymes were measured over 2 years, 0‐ to 20‐cm soil depth, under conventional disk tillage (CT) and no‐till (NT) under three SRLs. Soil chemical properties were measured as explanatory variables for changes in soil microbial communities and their enzymatic potential. Potential EEA of all enzymes decreased with stover removal and tillage. Soil bacterial biomass (BB) and fungal biomass (FB) decreased with SRL, while mycorrhizal biomass was unresponsive. Impacts of tillage on MB groups varied by year; however, FB was consistently higher under CT. At all growth stages, NT with all stover retained, a “soil conservation target” had distinct soil enzyme and bacterial FAME profiles compared to CT across all SRLs and to NT under high and sometimes moderate SRLs. Principal component analysis of soil properties was dominated by SRL with EEAs, BB, soil organic matter (SOM), water‐extractable carbon, and H3A‐extractable potassium being positively correlated to stover retention. Reduced input of microbial substrates also led to a loss of fine particulate organic matter, an indicator correlated to stable macroaggregation. Because NT partially ameliorated the negative impact of stover removal on BB, SOM fractions, and soil enzymes critical to nutrient cycling, pairing NT with stover removal may be more sustainable in the long term.

Design and Simulation of Aerosol Inlet System for Particulate Matter with a Wide Size Range

A novel aerodynamic lens-based inlet system was developed for a wide particle size range, and it could extend the size range of transmitted particulate matter (PM) to 50 nm–10 μm. The lens system adopted a seven-stage aerodynamic focusing orifice to extend the range of transmitted PM, and a relaxation system with a virtual impact function was introduced at the front of the aerodynamic lens. Through the innovative design, the system could concentrate the input samples as well as effectively enhance the focusing effect on large PM. Furthermore, an additional aerodynamic pre-focusing inlet system was innovatively added to the front of the sampling orifice of the traditional aerodynamic lens, and it could pre-focus large PM into the axis region before it entered the small orifice and then solve the previous problem with loss of large PM. Fluid simulations indicated that the inlet system could achieve 100% effective transmission and focusing for PM in the range of 0.18–10 μm. The characterization and verification results obtained from the improved single-particle aerosol mass spectrometer (SPAMS) were remarkably consistent with the theoretical values. The practical tests indicated that bioaerosol particles up to 10 μm could be detected. Compared with the observation for the same type of lens, the focusing performance of this novel lens system has better advantages in particle size range and transmission efficiency and therefore, it has broad application prospects in bioaerosol research, single-cell analysis, etc.

A semicontinuous study on the ecotoxicity of atmospheric particles using a versatile aerosol concentration enrichment system (VACES): development and field characterization

Abstract. Oxidative stress can be used to evaluate not only adverse health effects but also adverse ecological effects, but limited research uses eco-toxicological assay to assess the risks posed by particle matters to non-human biomes. One important reason might be that the concentration of toxic components of atmospheric particles is far below the high detection limit of eco-toxic measurement. To solve the rapid detection problem, we extended a versatile aerosol concentration enrichment system (VACES) for ecotoxicity aerosol measurement and firstly used VACES to provide a comparison of ecotoxicity between non-concentrated and concentrated aerosols in ambient air. In this study, the total concentration (number or mass), the concentration of chemical components and the ecotoxicity were all increased by approximately 7 to 10 times in VACES, making the detection of ecotoxicity above the baseline. The comparison of ecotoxicity data and PM2.5 concentration showed that low concentration was not matched with ecotoxicity, although high concentration corresponded to higher ecotoxicity. In addition, the higher saturation temperature in VACES caused a loss of particulate matter, of which nitrate accounted for about 18 %.

Development of a mobile platform for monitoring gaseous, particulate, and greenhouse gas (GHG) pollutants.

The Michigan Pollution Assessment Laboratory (MPAL) is a mobile air quality monitoring platform designed to measure conventional, toxic, and greenhouse gas (GHG) air pollutants. The spatially and temporally resolved data collected can be used for multiple purposes, such as mapping spatial patterns and identifying peaks. The truck-based platform includes instrumentation for 11 gaseous pollutants and for particulate matter (PM), size distribution (7nm to 20μm), PM10, black and brown carbon, and trace metals. MPAL is equipped with meteorological instruments, a high-accuracy GPS, forward and reverse cameras, and a data logging and display system. We selected commercially available instrumentation based on sensitivity, response time, and robustness. The vehicle's power system allows ~ 6.5h of continuous operation with all instruments operating. This article details the design, construction, and evaluation of MPAL and summarizes data collected in its first year (March 2019 to March 2020) of operation. We completed a series of runs on 84days in Detroit, Michigan, an area with a diverse set of traffic, industrial, and commercial emission sources, and collected 265,816 1-s observations (excluding collocations, zero checks, and other quality assurance measurements). Using data from these runs as well as special tests, we present results of performance evaluations that examined the response time, PM losses, and wind measurements and compare results to stationary regulatory monitoring data. We highlight key issues and provide practical solutions to help evaluate and resolve these issues and share many lessons learned in developing and using a mobile platform.

Dependence of the Dust Emission on the Aggregate Sizes in Loess Soils

Dust emission resulted from soil erosion by wind with significant impacts of soil (nutrient) loss and air pollution of particulate matter (PM). The ejection of dust from soil aggregates due to saltation has been hypothesized to play a major role in dust emission. Yet empirical information on the role of different aggregate sizes in dust emission is still lacking. The main goal of this study was to explore the dust emission threshold in different aggregate sizes of a semiarid loess soil. To this end, we conducted targeted wind-tunnel experiment on dust emission. The results show that dust emission from aggregate at size of 63–250 µm, 250–500 µm, and 500–1000 µm is enabled only under the conditions of saltation. The dust-PM threshold at shear velocities of 0.24–0.52 m/s depends on the aggregates size. Aggregates at the size of saltators (125–500 µm) were the most productive in dust generation by the mechanism of aggregate disintegration. In our bulk sample, the aggregate group of 63–250 µm has the highest contribution to the total dust emission. The study aimed to advance our capability in soil resources management and for model parameterization in dust emission schemes.

Agricultural land use alters temporal dynamics and the composition of organic matter in temperate headwater streams

AbstractIntensification of agricultural land use leads to riparian clear cutting, which disrupts stream aquatic-terrestrial linkages through the loss of terrestrial particulate organic matter (POM)...

The health economic loss of fine particulate matter (PM2.5) in Beijing

PM2.5 is the fine particle matter with the size smaller than 2.5 μm, and it is considered to be one of the atmospheric pollutants whose effects are the greatest on the public health. In recent years, the effects of PM2.5 in Beijing are getting more and more public attention. Based on this situation, using the exposure-response relationship model, the health loss assessment model and the annual average concentration data of PM2.5 from 2014 to 2015, this paper quantified the public health effect losses of PM2.5 and estimated the economic loss utilizing the willingness to pay in Beijing. The results demonstrated that in the four different concentrations baseline levels and the three different categories, the health economic loss caused by PM2.5 pollution was 4.83–6.63 billion yuan in 2014 and 4.32–6.32 billion yuan in 2015 in Beijing. And, the loss of the total death, cardiovascular disease death and respiratory system disease death accounted for the major loss in all kinds of health effect loss. From the results, it could also be seen that the number of people damaged by PM2.5 and the economic loss were falling from 2014 to 2015, which showed the worsening trend of air quality began to reverse in Beijing. It had played a positive role for Beijing to continue to control atmospheric pollution. However, because the annual concentration of PM2.5 in Beijing is still higher than four annual mean concentration baseline levels, it still exists a larger threat to the health effects.

The geochemical filter of large river confluences

This study reports the behaviour and fate of major and trace elements in solid and solution in the Encontro das Aguas mixing zone in the Amazonian basin. This area results from the confluence of acidic, organic-rich Rio Negro and Andean sediment-rich Rio Solimões. The differences existing between these two water masses are likely to modify the partitioning of elements between solid and solution or to induce losses by physical or chemical removal. To account for lateral and vertical heterogeneities in the river sections, the fluxes of elements in dissolved and solid loads were estimated as accurately as possible using an interpolation technique.A general loss of suspended particulate matter (SPM) of 23% is measured 80km after the confluence but the various elements and their associated hosted minerals are not affected in a similar way. SiSPM, CaSPM, NaSPM or SrSPM, mostly associated with coarse phases (quartz and Ca-Na feldspars) are preferentially lost. Refractory elements (CoSPM, CrSPM, TiSPM, AlSPM, NiSPM), other alkali (A) and alkali earth (AE) elements (KSPM, MgSPM, BaSPM), FeSPM or organic carbon (OC) are lost to a lesser extent due to their occurrence in finer fractions such as clays (smectite, illite or kaolinite), oxides and particulate organic matter (POM).In solution A-AE and Cudiss, mostly originating from the Rio Solimões behave conservatively. By contrast, refractory elements, coming mostly from the Rio Negro, exhibit important losses (from −10% for DOC to −60% for Codiss). Changes in pH and ionic strength during the mixing may induce a sorption of these elements to particles supplied by the Rio Solimões, a clustering and/or a settling of nanokaolinites phases or a sorption of Aldiss, Fediss, Codiss, Mndiss or Zndiss by dissolved organic matter (DOM).The differential elemental settling at a river confluence could thus induce a phase shift between element supply and export out of a watershed. The physical and chemical processes reported here for a river confluence could be applied in other mixing zones such as estuaries or mining exhausts.

Particulate organic matter higher concentrations, terrestrial sources and losses in bottom waters of the turbidity maximum, Delaware Estuary, U.S.A.

The pathway and fate of land-derived suspended particulate organic matter (POM) as it passes through estuaries remains a poorly constrained component of coastal carbon dynamics. The δ13C of bulk POC (particulate organic carbon; δ13C-POC) and n-alkane biomarkers were used to assess the proportion of algal- and land- (vascular plant) derived POM through the Delaware Estuary, on five cruises in 2010–2011. We found that POC was highly correlated with suspended sediment concentrations (SSC). Higher SSC was present in bottom waters, causing bottom waters to have consistently higher concentrations of POC than surface waters, with the bottom waters of the estuarine turbidity maximum (ETM) exhibiting maximum POC concentrations for all seasons and flow regimes. Algal-derived POM seasonally affected the δ13C-POC and n-alkane geochemical signatures of surface waters, whereas bottom waters were dominated by vascular plant-derived POM. δ13C-POC results suggested a gradual loss in vascular plant-derived POM between the riverine and marine endmember stations. In contrast, n-alkane concentrations peaked in bottom waters of the ETM at 2–5 times surface water concentrations. Indices of the relative proportions of n-alkanes and n-alkanes as a proportion of total POC had their levels decrease considerably downstream of the ETM. These biomarker analyses suggest enhanced loss of land-derived material across the ETM and that the ETM acts as a geochemical filter for vascular plant-derived POM in a classic well mixed estuary.

A new approach to estimate the in situ fractional degradation rate of organic matter and nitrogen in wheat yeast concentrates

In the classic in situ method, small particles are removed during rinsing and hence their fractional degradation rate cannot be determined. A new approach was developed to estimate the fractional degradation rate of nutrients in small particles. This approach was based on an alternative rinsing method to reduce the particulate matter loss during rinsing and on quantifying the particulate matter loss that occurs during incubation in the rumen itself. To quantify particulate matter loss during incubation, loss of small particles during the in situ incubation was studied using undegradable silica with different particle sizes. Particulate matter loss during incubation was limited to particles smaller than ~40 μm with a mean fractional particulate matter loss rate of 0.035 h−1 (first experiment) and 0.073 h−1 (second experiment) and an undegradable fraction of 0.001 and 0.050, respectively. In the second experiment, the fractional particulate matter loss rate after rinsing in a water bath at 50 strokes per minute (s.p.m.) (0.215 h−1) and the undegradable fraction at 20 s.p.m. (0.461) were significantly larger than that upon incubation in the rumen, whereas the fractional particulate matter loss rate (0.140 and 0.087 h−1, respectively) and the undegradable fraction (0.330 and 0.075, respectively) after rinsing at 30 and 40 s.p.m. did not differ with that upon rumen incubation. This new approach was applied to estimate the in situ fractional degradation rate of insoluble organic matter (OM) and insoluble nitrogen (N) in three different wheat yeast concentrates (WYC). These WYC were characterised by a high fraction of small particles and estimating their fractional degradation rate was not possible using the traditional washing machine rinsing method. The new rinsing method increased the mean non-washout fraction of OM and N in these products from 0.113 and 0.084 (washing machine method) to 0.670 and 0.782, respectively. The mean effective degradation (ED) without correction for particulate matter loss of OM and of N was 0.714 and 0.601, respectively, and significant differences were observed between the WYC products. Applying the correction for particulate matter loss reduced the mean ED of OM to 0.676 (30 s.p.m.) and 0.477 (40 s.p.m.), and reduced the mean ED of N to 0.475 (30 s.p.m.) and 0.328 (40 s.p.m.). These marked reductions in fractional degradation rate upon correction for small particulate matter loss emphasised the pronounced effect of correction for undegraded particulate matter loss on the fractional disappearance rates of OM and N in WYC products.

Estimation of the in situ degradation of the washout fraction of starch by using a modified in situ protocol and in vitro measurements

The in situ degradation of the washout fraction of starch in six feed ingredients (i.e. barley, faba beans, maize, oats, peas and wheat) was studied by using a modified in situ protocol and in vitro measurements. In comparison with the washing machine method, the modified protocol comprises a milder rinsing method to reduce particulate loss during rinsing. The modified method markedly reduced the average washout fraction of starch in these products from 0.333 to 0.042 g/g. Applying the modified rinsing method, the fractional degradation rate (k d) of starch in barley, oats and wheat decreased from on average 0.327 to 0.144 h−1 whereas for faba beans, peas and maize no differences in k d were observed compared with the traditional washing machine rinsing. For barley, maize and wheat, the difference in non-fermented starch in the residue between both rinsing methods during the first 4 h of incubation increased, which indicates secondary particle loss. The average effective degradation of starch decreased from 0.761 to 0.572 g/g when using the new rinsing method and to 0.494 g/g when applying a correction for particulate matter loss during incubation. The in vitro k d of starch in the non-washout fraction did not differ from that in the total product. The calculated ratio between the k d of starch in the washout and non-washout fraction was on average 1.59 and varied between 0.96 for oats and 2.39 for maize. The fractional rate of gas production was significantly different between the total product and the non-washout fraction. For all products, except oats, this rate of gas production was larger for the total product compared with the non-washout fraction whereas for oats the opposite was observed. The rate of increase in gas production was, especially for grains, strongly correlated with the in vitro k d of starch. The results of the present study do not support the assumption used in several feed evaluation systems that the degradation of the washout fraction of starch in the rumen is much faster than that of the non-washout fraction.

Organic matter cycling in a neotropical reservoir: effects of temperature and experimental conditions

AIM:This study reports a comparison between decomposition kinetics of detritus derived from two macrophyte species (Polygonum lapathifolium L.: Polygonaceae; Eichhornia azurea (Sw.) Kunth.: Pontederiaceae) growing in a neotropical reservoir (Brazil), under laboratory and field conditions, in order to assess hypotheses on the main differences in factors affecting organic matter cycling, including the effect of temperature. METHODS: Plant and water samples were collected from the reservoir in August 2009. In field incubation mass loss was assessed using a litter bag technique and in the laboratory the decay was followed using a decomposition chamber maintained under controlled conditions (i.e. in the dark, at 15 ºC and 25 ºC). A kinetic model was adopted to explain and compare the organic matter decay, ANOVA (Repeated Measures) testing was used to describe the differences between the treatments and a linear correlation was used to compare in situ and in vitro experiments. RESULTS: The mass decay was faster in natural conditions with rapid release of the labile-soluble portion. The simulated values of mineralization rates of dissolved organic matter and refractory organic matter were rapid in high temperatures (25 ºC). The high Q10 results (mainly for E. azurea), and experimental conditions, and outcomes of ANOVA testing indicate the temperature variation (10 ºC) influence the rates of mass decay. CONCLUSIONS: The results suggested rapid organic matter cycling in warm months (from October to December) supporting the microbial loop. Although the particulate organic matter losses are high in field conditions the results are of the same magnitude in both conditions suggesting an equivalence of the mass decay kinetic.

Investigation of the mass loss of water soluble ionic compounds caused by EDXRF analysis of PM10 loaded filters

The mass loss of particulate matter (PM) due to EDXRF analysis was gravimetrically evaluated on co-located PM10 loaded filters analyzed both using EDXRF under vacuum and using Ion Chromatography. Then, this comparison was repeated with air and helium (He) instead of evacuating the measurements chamber of the EDXRF spectrometer. It was shown that EDXRF application using vacuum medium led to mass loss of water soluble ionic compounds and other volatile constituents of PM10. The use of a He and air medium considerably reduced the PM mass losses. It is demonstrated that the mass loss of PM and ionic compounds mainly resulted from vacuum medium and from a lower extent to the level of X-ray energy. The influence of EDXRF application using vacuum medium on the mass losses of ionic compounds were further investigated. Different amounts of NO3−, NH4+, Cl−, Na+, Mg++ and Ca++ were lost whereas SO4−− and K+ remained unchanged. The relationship between vacuum and application time was also studied for quartz and Teflon filters. The longer the application time, the higher the PM mass loss was observed. The mass loss of PM on quartz filter was shown by experiments to be 2 times higher than on Teflon filter.

An evaluation of resident exposure to respirable particulate matter and health economic loss in Beijing during Beijing 2008 Olympic Games

Previous epidemiological studies showed that air pollutants, especially respirable particulate matter, including PM 10, could impose harmful effects on human health. The assessment of the effects of PM 10 on mortality and morbidity makes an important basis for enhancing pollution control efforts, and for protecting public health. In this study, we measured the levels of Beijing residents' exposure to PM 10 during three different time periods around the Beijing Olympic Games held in 2008, and calculated the economic cost associated with human health. A comparative analysis of human exposure to PM 10 and associated health economics was also made to see the difference between 2005 and 2008. GIS technology was employed to interpolate the distribution of population and PM 10 data collected by 27 stations at a scale of 1 km × 1 km. Study results show that Beijing's population is distributed in a highly inhomogeneous manner, with the majority of people dwelling in the city proper. During the Olympic Games, population-weighted PM 10 exposure came down by 46% and 19% respectively, compared with the pre-OG and the post-OG periods. Consequently, the economic cost associated with human health during the Games came down by 38% and 16% respectively, compared with the pre-OG and the post-OG periods. Comparative analysis shows that during the Olympic Games, both PM 10 and the economic cost associated with health as a proportion of GDP sat at the bottom of the 4-year statistics, indicating that in addition to favorable weather conditions, enhanced traffic and emission control policies and measures have produced a noticeable effect on PM 10 reduction.

Chemical analysis of cigarette smoke particulate generated in the MSB-01 in vitro whole smoke exposure system

Cigarette mainstream smoke (MS) is a dynamic aerosol consisting of a gas–vapor phase and a particulate phase. In recent years, novel in vitro whole smoke exposure systems have been developed to expose cells directly to whole MS. One such system is the Burghart Mimic Smoker-01 (MSB-01). Our previous data using the MSB-01 indicated that a 50 ± 10% loss of particulate matter occurred prior to MS delivery into the exposure chamber. Additionally, a change in aerosol particle diameter was also measured, suggesting that the chemical composition of MS might be changing within the system. In this study, we have expanded on our previous work and compared the particulate phase chemical composition of undiluted and diluted MS generated by the instrument and that of the MS delivered into the exposure chamber. The average percent delivery of cigarette smoke condensate (CSC) detected for all the measured chemical constituents was 35 ± 13% for undiluted MS and 23 ± 8% for 1:1 diluted MS. The data also indicate that under our experimental conditions, incomplete mixing of the freshly generated MS occurs during its dilution by the system. Taken together, the data presented here show that significant chemical changes occur between the generation of MS by the system and its delivery into the exposure chamber. This indicates that due to the dynamic nature of cigarette smoke, it is important to characterize the exposure conditions in order to gain the best insight and accurately correlate exposure with biological endpoints.

Atmospheric Transfer and Deposition Mechanisms of 210Pb Aerosols onto Forest Soils

Activities of 210Pb carrier aerosols in an age-graded Sitka spruce conifer, three deciduous (oak, lime and sycamore) foliage and in rain and throughfall samples have been measured during the period of 2001–2002. The 210Pb concentrations in the age-graded Sitka leaf needles have shown to accumulate until a steady state between accretion and loss of particulate matter is maintained with time. Similarly, the concentrations of 210Pb on deciduous tree leaves increased with time until the leaves began to senesce. The 210Pb inventory in bulk precipitation was significantly (r 2 = 0.99; P < 0.001) large compared with that in throughfall samples, as indicated by a ratio of 1 to 0.1 of 210Pb deposition in bulk precipitation to throughfall. This suggests that 210Pb is retained in the Sitka spruce foliage during deposition until transfer to the ground mainly through litterfall. These findings suggest that the presence of woodland is responsible for enhanced 210Pb deposition fluxes beneath wooded areas relative to open grassland soils.

Development and validation of the volatile correction model for PM 10 – An empirical method for adjusting TEOM measurements for their loss of volatile particulate matter

EU Directives stipulate that PM 10 should be measured using the gravimetric reference method as laid out in EN12341 [CEN, 1998. Air Quality – Determination of the PM 10 Fraction of Suspended Particulate Matter – Reference Method and Field Test Procedure to Demonstrate Reference Equivalence of Measurement Methods. European Committee for Standardisation], or an equivalent method as demonstrated using EC guidance [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. There is however a conflict between the requirement to measure PM 10 using the gravimetric reference method and the need for rapid public reporting, and many member states, including the UK, rely on non-gravimetric techniques to measure PM 10. In the UK the majority of PM 10 measurements are made using the Tapered Element Oscillating Microbalance (TEOM), which does not meet the equivalence criteria [Harrison, D., 2006. UK Equivalence Programme for Monitoring of Particulate Matter. Defra, London]. The implied need to upgrade or replace TEOMs with an equivalent automated measurement technique has significant cost implications. The model described in this paper was based on analysis of daily mean measurements of PM 10 by the Filter Dynamics Measurement System (FDMS) and the TEOM at UK sites. It uses the FDMS measurement of the volatile component of PM 10 (referred to here as FDMS purge) to correct for differences in the sensitivity to volatile PM 10 between the TEOM and the EU gravimetric reference method. The model equation for the correction of TEOM PM 10 measurements is: TEOM VCM = TEOM − 1.87 FDMS purge due to the regional homogeneity of volatile PM, the FDMS purge concentration may be measured at a site distant to the TEOM, allowing the possibility of using a single FDMS instrument to correct PM 10 measurements made by several TEOMs in a defined geographical area. The model was assessed against the criteria for the EC Working Group's Guidance for the Demonstration of Equivalence of Ambient Air Monitoring Methods [EC, 2005. Demonstration of Equivalence of Ambient Air Monitoring Methods. European Commission Working Group on Guidance for the Demonstration of Equivalence]. The model satisfies the equivalence criteria using remote FDMS purge measurements for distances up to 200 km (in 22 out of 23 data sets). These data provide strong evidence that the model is a viable tool for correcting measurements from TEOM instruments on the national and local government networks.

Loss of PM2.5 Nitrate from Filter Samples in Central California

Evaporative loss of particulate matter (with aerodynamic diameter <2.5 μm, [PM2.5]) ammonium nitrate from quartz-fiber filters during aerosol sampling was evaluated from December 3, 1999, through February 3, 2001, at two urban (Fresno and Bakersfield) and three nonurban (Bethel Island, Sierra Nevada Foothills, and Angiola) sites in central California. Compared with total particulate nitrate, evaporative nitrate losses ranged from <10% during cold months to >80% during warm months. In agreement with theory, evaporative loss from quartz-fiber filters in nitric acid denuded samplers is controlled by the ambient nitric acid-to-particulate nitrate ratio, which is determined mainly by ambient temperature. Accurate estimation of nitrate volatilization requires a detailed thermodynamic model and comprehensive chemical measurements. For the 14-month average of PM2.5 acquired on Teflon-membrane filters, measured PM2.5 mass was 8–16% lower than actual PM2.5 mass owing to nitrate volatilization. For 24-hr samples, measured PM2.5 was as much as 32–44% lower than actual PM2.5 at three California Central Valley locations.

Transformation of a Podocarpus falcatus dominated natural forest into a monoculture Eucalyptus globulus plantation at Munesa, Ethiopia: soil organic C, N and S dynamics in primary particle and aggregate-size fractions

Abstract Changes in land use and management can affect soil structure, soil organic carbon (SOC) and other nutrients reserve (such as N, P, S). We analyzed organic carbon (OC), total nitrogen (N), and total sulfur (S) in particle-size, aggregate-size and size/density fractions of soil organic matter (SOM) in order to identify the SOM pools most affected by the conversion of a Podocarpus falcatus dominated mixed natural forest into a monoculture Eucalyptus globulus plantation 21 years ago on a reddish brown Nitisol at Munesa, Ethiopia. Bulk soil OC, N, and S concentrations and stocks in soil to 20 cm depth were not significantly changed after the conversion of the natural forest into Eucalyptus plantation, but C/N ratio narrowed significantly. Soil organic C, N and S concentrations, and C/N and C/S ratios in sand and silt separates from the plantation samples were significantly reduced, while clay N and S concentrations had slightly increased. The losses of SOC, N and S in the sand fraction were more pronounced than that in the silt. Aggregate stability and total SOC, N and S concentrations of the aggregates were not significantly different in samples from the Eucalyptus plantation and the natural forest. In the plantation samples, both the free light fraction (LF) and the intra-particulate organic matter (iPOM) C, N and S concentrations associated with the macroaggregates were significantly reduced. Differences in the total amount of the free LF (on the basis of water-stable aggregates proportion) between the two forest types were not apparent, suggesting that SOM quality is more prone to changes in land use and soil management strategies than the total amount of SOM. The loss of iPOM was higher than that of free LF probably due to gaseous losses of organic matter (OM) inside the aggregates caused by high fire temperatures during clearing and site preparation. In both forest types, the LF OM comprised the highest percentage of whole soil OM and the loss of particulate organic matter (POM) accounted for much of the losses of OM. Overall, the results showed that analysis of OC, N and S concentrations in soil particle and aggregate-sizes, and size/density fraction of SOM allowed sensitive detection of changes in SOM dynamics and soil fertility resulting from changes in land use.