Optimisation of microwave assisted extraction (MAE) for polycyclic aromatic hydrocarbon (PAH) determination in smoked meat

A rapid extraction method involving microwave assisted extraction (MAE), followed by sample clean-up on a silica cartridge, reversed-phase high performance liquid chromatography (RP-HPLC) and spectrofluorimetric detection, was optimised for polycyclic aromatic hydrocarbon (PAH) determination in smoked meat. Compared to solvent extraction assisted by sonication, MAE, carried out with n-hexane on 2g of lyophilised sample at 115°C for 15min, allowed to obtain better extraction efficiencies. Limits of quantification (LOQ, s/n=10) lower than 0.2μg/kg wet weight were found for all PAHs, except for Fl (0.3μg/kg), P (0.6μg/kg) and IP (0.4μg/kg). The optimised procedure, that presented good analytical performances (with recoveries ranging from 77% to 103%, and precision within 10% for most of the PAHs), was applied to determine PAH content in different smoked meat products from the Italian market.     

Concentration profile of selected polycyclic aromatic hydrocarbon (PAH) fractions in some processed meat and meat products

This study investigates the concentration profiles of selected polycyclic aromatic hydrocarbon (PAH) fractions in selected processed meats, in order to evaluate their dietary and health implications. Smoked, grilled and boiled meat products were bought from different locations in Cape Town and Cape Town environs. PAHs were extracted from each meat sample according to standard methods. The concentrations of benzo[k]fluoranthene (BkP), benzo[a]pyrene (BaP), indeno[1, 2, 3-cd]pyrene (IP), and benzo[g, h, i]perylene(BghiP) in the processed meat extracts were determined using a gas chromatograph coupled with flame ionization detector. Total PAH concentrations in smoked, grilled and boiled chicken fillets, pork, and beef stripes were ranged 2.79, 0.99, 2.33 μg/kg; 19.11, 11.17, 15.04 μg/kg; and 14.84, 9.29, 7.20 μg/kg respectively. There were significant differences (p > 0.05) in the concentration levels of PAHs detected in different types, with the highest levels observed in smoked pork meat. The concentration of BkP, BaP, IP and BghiP detected in the various meat samples were below the EU and WHO dietary exposure limit.     

Biodegradation, bioaccessibility, and genotoxicity of diffuse polycyclic aromatic hydrocarbon (PAH) pollution at a motorway site

Diffuse pollution of surface soil with polycyclic aromatic hydrocarbons (PAHs) is problematic in terms of the large areas and volumes of polluted soil. The levels and effects of diffuse PAH pollution at a motorway site were investigated. Surface soil was sampled with increasing distance from the asphalt pavement and tested for total amounts of PAHs, amounts of bioaccessible PAHs, total bacterial populations, PAH degrader populations, the potential for mineralization of 14C-PAHs, and mutagenicity. Elevated PAH concentrations were found in the samples taken 1-8 m from the pavement. Soil sampled at greater distances (12-24 m) contained only background levels of PAHs. The total bacterial populations (CFU and numbers of 16S rDNA genes) were similar for all soil samples, whereas the microbial degrader populations (culturable PAH degraders and numbers of PAH dioxygenase genes) were most abundant in the most polluted samples close to the pavement. Hydroxypropyl-beta-cyclodextrin extraction of soil PAHs, as a direct estimate of the bioaccessibility, indicated that only 1-5% of the PAHs were accessible to soil bacteria. This low bioaccessibility is suggested to be due to sorption to traffic soot particles. The increased PAH level close to the pavement was reflected in slightly increased mutagenic activity (1 m, 0.32 +/- 0.08 revertants g(-1) soil; background/ 24 m: 0.08 +/- 0.04), determined by the Salmonella/ microsome assay of total extractable PAHs activated by liver enzymes. The potential for lighter molecular weight PAH degradation in combination with low bioaccessibility of heavier PAHs is proposed to lead to a likely increase in concentration of heavier PAHs over time. These residues are, however, likely to be of low biological significance.     

Carcinogenic polycyclic aromatic hydrocarbons (PAH) determined in Nigerian kundi (smoke-dried meat)

Chemical analyses of kundi show that, apart from a high level of carcinogenic benzo (a)pyrene (10·5–66·9 ng g^?1), eight other polycyclic aromatic hydrocarbons (PAH) are present at various concentrations. The high levels of PAH in kundi are due to the high glow and smoking temperatures averaging 926°C and 191·5°C, respectively. Column chromatography was used for PAH extraction with propylene carbonate as the eluting chemical; thin layer chromatography (TLC) on acetylated cellulose layer plates was used for separation, and the determination was performed using spectrophotofluorimetry. The public health implications of PAH as one of the possible carcinogenic factors in the high incidence of primary liver and stomach cancer reported in Nigeria are highlighted.     

Effect of fuel and kiln type on the polycyclic aromatic hydrocarbon (PAH) levels in smoked shrimp,a Beninese food condiment

Smoked shrimp is a food condiment widely used in Beninese local cooking practices. A previous study revealed that this product is highly contaminated with polycyclic aromatic hydrocarbons (PAH). The present study explored possibilities to reduce PAH levels in shrimp smoked using cottage industry smoking techniques with barrel and chorkor kilns, by replacing wood by charcoal from Acacia auriculiformis and Mangifera indica, as fuels. Results showed that only shrimp smoked using acacia charcoal in a chorkor kiln had PAH levels (benzo[a]pyrene = 5 µg kg^?1 and sum of benzo[a]pyrene, chrysene, benzo[a]anthracene and benzo[b]fluoranthene = 28 µg kg^?1) in accordance with a European standard of 5 and 30 µg kg^?1, respectively, and suitable physicochemical characteristics for good storage (moisture content = 11.9% ± 1.5%; water activity = 0.46 ± 0.03). However, further investigations still needs to be done to reduce the duration of product contact with combustion gasses in order to reduce the PAH content of smoked shrimp to safer levels, largely below standards.     

Reduction of the polycyclic aromatic hydrocarbon (PAH) content of charcoal smoke during grilling by charcoal preparation using high carbonisation and a preheating step

Charcoal-grilling may lead to contamination of food with carcinogenic polycyclic aromatic hydrocarbons (PAHs) during the grilling process. The objective of this work was to determine the effect of charcoal preparation on 16 USEPA priority PAHs in the smoke produced during the grilling process. Firstly, mangrove charcoal was prepared at carbonisation temperatures of 500, 750 and 1000°C. The charcoal were then preheated by burning at 650°C. This preheating step is usually used to prepare hot charcoal for the grilling process in the food industry. In this study, charcoal was preheated at different burning times at 5, 20 min and 5 h, at which time partial and whole charcoal glowed, and charcoal was completely burnt, respectively. Finally, PAHs in the smoke were collected and determined by GC/MS. The result showed that charcoal prepared at a carbonisation temperature of 500°C had higher levels of PAHs released into the smoke. In contrast, charcoal produced at 750 and 1000°C had lower PAHs released for all burning times. In addition, PAHs released for 5, 20 min and 5 h of burning time were about 19.9, 1.2 and 0.7 µg g^?1 dry charcoal for charcoal produced at 500°C, and about 0.9–1.4, 0.8–1.2 and 0.15–0.3 µg g^?1 dry charcoal for charcoal produced at 750 and 1000°C, respectively. Therefore, this research suggests that food grilled using charcoal carbonised at a high temperature of about 750°C presents a lower risk of PAH contamination. In addition, in the preheating step, whole charcoal should fully glow in order to reduce the PAH content in charcoal before grilling.     

Spatial distributions and profiles of atmospheric polycyclic aromatic hydrocarbons in two industrial cities in Japan

The spatial distribution and concentration profiles of 39 vapor and particulate polycyclic aromatic hydrocarbons (PAHs) have been investigated in two Japanese industrial cities (Fuji and Shimizu; a summer and winter season in each). The concentrations of particulate PAHs in winter tended to be higher than those in the summer, but for vapor PAHs, this was not the case. Significant correlations (p < 0.01) were found between most of the PAH concentrations monitored in winter, suggesting the presence of common emission sources. To identify PAH spatial distributions and emission sources in the area, we created contour maps for PAHs monitored; this indicates that the distinctive local distributions correspond to the emission sources. PAH profiles based on benzo[e]pyrene (BeP) concentration, especially for certain relatively heavy molecular weight PAHs, showed differential behaviors among divided areas related to potential regional emission sources such as paper-making plants, power plants, and traffic. We conclude that the origins of atmospheric PAHs in the surveyed areas were dominated by not only traffic but also by stationary emission sources such as paper-making plants and power plants and that local distributions were dependent on the local wind direction.     

Preparation and stability of ampouled polycyclic aromatic hydrocarbon solutions

Summary A 1-year stability study of ampouled polycyclic aromatic hydrocarbon (PAH) solutions was carried out. Two solutions of seven pure PAHs were prepared, one in acetonitrile and one in toluene, and ampouled. Solutions were tested for mass concentration and impurities before and after ampouling. No differences were found. After 0, 3, 6, 9 and 12 months, three ampoules were selected for analysis from the acetonitrile and the toluene lots stored at +20° and at –20 °C. The acetonitrile solution was analysed by high performance liquid chromatography and the toluene solution by glass capillary gas chromatography. The results demonstrate that both solutions were stable and no contamination. occurred during storage.

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Herstellung und Stabilität von polycyclischen aromatischen Kohlenwasserstofflösungen in Ampullen

Zusammenfassung Für eine einjährige Studie über die Stabilität von PAK-Lösungen in Ampullen wurde je eine Lösung von sieben reinen polycyclischen aromatischen Kohlenwasserstoffen in Acetonitril und in Toluol hergestellt und in Ampullen eingeschlossen. Die Lösungen wurden vor und nach dem Einschluß in Ampullen auf ihren Gehalt und ihre Zusammensetzung untersucht, wobei keine Abweichungen festgestellt wurden. Nach 0, 3, 6, 9 und 12 Monaten wurden jeweils drei Ampullen der bei –20 °C and +20 °C gelagerten Lösungen untersucht, und zwar die Acetonitrillösung mit Hochdruckflüssigchromatographie und die Toluollösung mit Capillar-Gaschromatographie. Die Ergebnisse zeigen, daß beide Lösungen während der ganzen Lagerungszeit stabil und kontaminationsfrei waren.

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This study has been carried out on behalf of the Community Bureau of Reference (BCR) Brussels/Belgium — Commission of the European Communities Contract BCR 2093/1/5/204/85/2-BCR-NL(10) of April 12th. 1985     

Monitoring of polycyclic aromatic hydrocarbons (PAH) in food supplements containing botanicals and other ingredients on the Dutch market

Food supplements can contain polycyclic aromatic hydrocarbons (PAH). The European Food Safety Authority (EFSA) has defined 16 priority PAH that are both genotoxic and carcinogenic and identified eight priority PAH (PAH8) or four of these (PAH4) as good indicators of the toxicity and occurrence of PAH in food. The current study aimed to determine benzo[a]pyrene and other EFSA priority PAH in different categories of food supplements containing botanicals and other ingredients. From 2003 to 2008, benzo[a]pyrene exceeded the limit of quantification (LOQ) in 553 (44%) of 1258 supplements with a lower-bound mean of 3.37?µg?kg^?1. In 2008 and 2009, benzo[a]pyrene and 12 other EFSA priority PAH were determined in 333 food supplements. Benzo[a]pyrene exceeded the LOQ in 210 (63%) food supplements with a lower-bound mean of 5.26?µg?kg^?1. Lower-bound mean levels for PAH4 and PAH8(-indeno[1,2,3-cd]pyrene) were 33.5 and 40.5?µg?kg^?1, respectively. Supplements containing resveratrol, Ginkgo biloba, St. John's wort and propolis showed relatively high PAH4 levels in 2008 and 2009. Before 2008, supplements with these ingredients and also dong quai, green tea or valerian contained relatively high benzo[a]pyrene levels. On average, PAH4 intake resulting from food supplement use will be at the lower end of the range of contributions of main food groups to PAH4 exposure, although individual food supplements can contribute significantly to PAH4 exposure. Regular control of EFSA indicator PAH levels in food supplements may prove a way forward to reduce further the intake of PAH from food.     

Preparation and stability of ampouled polycyclic aromatic hydrocarbon solutions

A 1-year stability study of ampouled polycyclic aromatic hydrocarbon (PAH) solutions was carried out. Two solutions of seven pure PAHs were prepared, one in acetonitrile and one in toluene, and ampouled. Solutions were tested for mass concentration and impurities before and after ampouling. No differences were found. After 0, 3, 6, 9 and 12 months, three ampoules were selected for analysis from the acetonitrile and the toluene lots stored at +20 degrees and at -20 degrees C. The acetonitrile solution was analysed by high performance liquid chromatography and the toluene solution by glass capillary gas chromatography. The results demonstrate that both solutions were stable and no contamination occurred during storage.     

Trends in polycyclic aromatic hydrocarbon concentrations in the great lakes atmosphere

Atmospheric polycyclic aromatic hydrocarbon (PAHs) concentrations were measured in both the vapor and particle phases at seven sites near the Great Lakes as a part of the Integrated Atmospheric Deposition Network. Lower molecular weight PAHs, including fluorene, phenanthrene, fluoranthrene, and pyrene, were dominant in the vapor phase, and higher molecular weight PAHs, including chrysene, benzo[a]pyrene, and coronene, were dominant in the particle phase. The highest PAH concentrations in both the vapor and particle phases were observed in Chicago followed by the semiurban site at Sturgeon Point, NY. The spatial difference of PAH concentrations can be explained by the local population density. Long-term decreasing trends of most PAH concentrations were observed in both the vapor and particle phases at Chicago, with half-lives ranging from 3-10 years in the vapor phase and 5-15 years in the particle phase. At Eagle Harbor, Sleeping Bear Dunes, and Sturgeon Point, total PAH concentrations in the vapor phase showed significant, but slow, long-term decreasing trends. At the Sturgeon Point site, which was impacted by a nearby city, particle-phase PAH concentrations also declined. However, most particle-phase PAH concentrations did not show significant long-term decreasing trends at the remote sites. Seasonal trends were also observed for particle-phase PAH concentrations, which were higher in the winter and lower in the summer.     

Emissions of polycyclic aromatic hydrocarbons (PAH) from creosoted railroad ties and their relevance for life cycle assessment (LCA)

Based on the analysis of cross sections of railroad ties, which were in use for up to 46 years, inventory, emission factors and total yearly emissions of creosote, PAH and phenols from the Swiss railway network were determined. During the service time of a railroad tie of 20 to 30 years, roughly 5 kg creosote are emitted. PAH emissions are in the order of about 0.5 kg (sum of 16 EPA-PAH) and occur as emissions of the volatile 2- and 3-ring PAH (such as naphthalene, acenaphthylene, acenaphthene, anthracene, fluorene, and phenanthrene). Emissions of phenolic compounds are in the range of 10 g for each tie. According to our study, about 1710 t of creosote components, 139 t of EPA-PAH and 4 t of phenolic compounds are emitted by the creosoted ties of the Swiss railway network, every year. Based on these results and on a previous study on environmental life cycle assessment (LCA) of railway ties made of creosoted beech, prestressed concrete and sectional steel, the environmental effects caused by wooden ties were compared with the environmental effects of rail and road traffic. The PAH emissions from wooden ties have an enormous influence on the two effect oriented impact categories photochemical ozone creation and human toxicity. For all other impact categories, the PAH emissions are not relevant. If the road traffic (including its upstream processes) is included in the LCA, it is clearly dominating all impact categories. The use of new creosotes according to the WEI-C standard (lower benzo[a]pyrene content, less evaporation) improves the rating in the impact category photochemical ozone creation. Less than 14% of the total impact are caused by PAH emissions if creosote WEI-C is used, compared to more than 50% for creosote WEI-A. The LCA also demonstrates that the most effective measure to reduce the potential of photochemical ozone creation and human toxicity is a reduction of the road traffic. Zusammenfassung Gestützt auf die Analyse von Querschnittsprofilen durch ausgewählte Eisenbahnschwellen, die bis zu 46 Jahre lang im Einsatz waren, wurden Inventar, Emissionsfaktoren und totale jährliche Emissionen von Teeröl, PAK und Phenolen aus dem Schweizer Schienennetz bestimmt. Eine teerölbehandelte Eisenbahnschwelle (Buchen- oder Eichenholz) emittiert während einer Einsatzdauer von 20 bis 30 Jahren rund 5 kg Teeröl. PAK Emissionen liegen im Bereich von etwa 0,5 kg (Summe der 16 EPA-PAK) und liegen als Emissionen der flüchtigen 2- und 3-Ring PAK (Naphthalin, Acenaphthylen, Acenaphthen, Anthracen, Fluoren und Phenanthren) vor. Die Emissionen phenolischer Verbindungen liegen im Bereich von 10 g pro Schwelle. Gemäss unseren Untersuchungen werden aus den teerölbehandelten Eisenbahnschwellen des schweizerischen Schienennetzes pro Jahr rund 1710 t Teeröl, 139 t EPA-PAK und 4 t phenolische Verbindungen emittiert. Basierend auf diesen Resultaten und einer bereits veröffentlichten Studie zur ökologischen Bewertung von Streckenschwellen aus vorgespanntem Beton, Profilstahl und teerölimprägniertem Buchenholz in der Schweiz wurden die Umwelteinflüsse von teerölbehandelten Eisenbahnschwellen mit denen des Schienen- und Strassenverkehrs verglichen. Die PAK Emissionen aus teerölbehandelten Holzschwellen haben einen enormen Einfluss auf die beiden effektorientierten Bewertungsparameter photochemische Ozonbildung und Humantoxizität. Für alle anderen Bewertungsparameter sind die PAK Emissionen nicht relevant. Falls der Strassenverkehr (inklusive Vorketten) mit in den Vergleich einbezogen wird, dominiert dieser alle Bewertungskategorien klar. Der Einsatz des neuen Teeröl nach WEI-C (tieferer Benzo[a]pyren Gehalt, tiefere Verdunstungsneigung) stellt in Bezug auf die photochemische Ozonbildung eine klare Verbesserung dar. Weniger als 14% der Gesamtbelastung werden erreicht, wenn Teeröl nach WEI-C eingesetzt wird, verglichen mit 50% im Falle von Teeröl nach WEI-A. Die ökologische Bewertung zeigt, dass die Bedeutung der PAK-Emissionen aus Holzschwellen im Vergleich zu anderen Emissionsquellen des Verkehrs gering ist. Ein größeres Potential zur Reduktion der Bewertungsparameter photochemische Ozonbildung und Humantoxizität besteht in einer Reduktion des Strassenverkehrs, insbesondere des motorisierten Individualverkehrs.     

Emissions of polycyclic aromatic hydrocarbons (PAH) from creosoted railroad ties and their relevance for life cycle assessment (LCA)

Based on the analysis of cross sections of railroad ties, which were in use for up to 46 years, inventory, emission factors and total yearly emissions of creosote, PAH and phenols from the Swiss railway network were determined. During the service time of a railroad tie of 20 to 30 years, roughly 5 kg creosote are emitted. PAH emissions are in the order of about 0.5 kg (sum of 16 EPA-PAH) and occur as emissions of the volatile 2- and 3-ring PAH (such as naphthalene, acenaphthylene, acenaphthene, anthracene, fluorene, and phenanthrene). Emissions of phenolic compounds are in the range of 10 g for each tie. According to our study, about 1710 t of creosote components, 139 t of EPA-PAH and 4 t of phenolic compounds are emitted by the creosoted ties of the Swiss railway network, every year. Based on these results and on a previous study on environmental life cycle assessment (LCA) of railway ties made of creosoted beech, prestressed concrete and sectional steel, the environmental effects caused by wooden ties were compared with the environmental effects of rail and road traffic. The PAH emissions from wooden ties have an enormous influence on the two effect oriented impact categories photochemical ozone creation and human toxicity. For all other impact categories, the PAH emissions are not relevant. If the road traffic (including its upstream processes) is included in the LCA, it is clearly dominating all impact categories. The use of new creosotes according to the WEI-C standard (lower benzo[a]pyrene content, less evaporation) improves the rating in the impact category photochemical ozone creation. Less than 14% of the total impact are caused by PAH emissions if creosote WEI-C is used, compared to more than 50% for creosote WEI-A. The LCA also demonstrates that the most effective measure to reduce the potential of photochemical ozone creation and human toxicity is a reduction of the road traffic.     

Contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages depending on smoking conditions using glow smoke

The contents of polycyclic aromatic hydrocarbons (PAH) and phenolic substances in Frankfurter-type sausages were investigated depending on hot smoking conditions (glow smoke). For the 24 smoking experiments (performed in duplicates) three different smoke densities and ventilator velocities as well as wood chips with five different moisture contents were tested. During the smoking process, concentrations of O₂, CO₂ and CO, humidity and temperature in the smoking chamber as well as smoke generation temperature were determined. The chemical analysis included the contents of the 15 + 1 EU priority PAH and the phenolic substances guaiacol, 4-methylguaiacol, syringol, eugenol and trans-isoeugenol. The smoking conditions had a significant influence on smoke generation temperature, organoleptic properties and the formation of PAH and phenolic substances. The PAH contents increased with smoke density and ventilator velocity. No correlation between the contents of PAH and phenols was observed.     

Remediation of polycyclic aromatic hydrocarbon compounds in groundwater using poplar trees

A seven-year study was conducted to assess the effectiveness of hybrid poplar trees to remediate polycyclic aromatic hydrocarbon (PAH) compounds in soil and groundwater at a creosote-contaminated site. A reduction in the areal extent of the PAH plume was observed in the upper half of the 2-m-thick saturated zone, and PAH concentration levels in the groundwater declined throughout the plume. PAH concentrations began to decline during the period between the third and fourth growing seasons, which coincided with the propagation of the tree roots to the water table region. Remediation was limited to naphthalene and several three-ring PAHs (acenaphthylene and acenaphthene). PAH concentrations in soil and aquifer sediment samples also declined over time; however, levels of four-ring PAHs persisted at the lower depths during the study period. The naphthalene to total PAH concentration ratio in the most contaminated groundwater decreased from >0.90 at the beginning of the second growing season to approximately 0.70 at the end the study. Remediation in the lower region of the saturated zone was limited bythe presence of a 0.3-m-thick layer of creosote present as a dense nonaqueous phase liquid (DNAPL). The nearly steady-state condition of the PAH concentrations observed during the last three years of the study suggests that the effectiveness of the phytoremediation system is limited by the rate of PAH dissolution from the DNAPL source.     

A GC/MS method for the determination of carcinogenic polycyclic aromatic hydrocarbons (PAH) in smoked meat products and liquid smokes

A GC/MS method for the determination of ten polycyclic aromatic hydrocarbons (PAH) with four to six condensed aromatic carbon rings (including the six carcinogenic PAH) in smoked meat products and liquid smokes has been developed. The method implies accelerated solvent extraction (ASE), gel permeation chromatography for efficient lipid removal without saponification and ¹³C-labelled PAH for quantification. The calibration curves showed a good linearity for all PAH in the concentration range 0.01–10,000 ppb, the repeatabilities (RSDs, n=6) of different PAH ranged from 3 to 12%. Using this method, the analysis of a standard reference material of the National Institute of Standards and Technology (mussel tissue, SRM 2977) resulted in a good accordance between measured and certified PAH concentrations. The determination of PAH contents in 26 samples of smoked meat products and liquid smokes further confirmed the analytical power of the new method and gave a first insight into the specific PAH patterns.     

Evolution of the concentrations of polycyclic aromatic hydrocarbons in burnt woodland soils

Little is known of the fate of polycyclic aromatic hydrocarbons (PAHs) in soils under burnt woodland. It is not clear what the behavior of the overlying wood ash layer will be along months. In this study, the levels of eight representative PAHs in the 1-5 cm layer of a periurban woodland soil that had undergone wildfire were compared with those measured in nearby and distant unburnt periurban woodland soils and in a distant unburnt rural woodland soil, and the levels at the burnt site were monitored during some 10 months. The analytical method optimized for the purpose afforded recoveries of 74-111% (depending on PAH) and repeatabilities (RSDs) better than 9%, with limits of detection ranging from 1 to 7 microg/kg. PAH levels in the 1-5 cm layer of the burnt periurban soil were very similar to those of distant unburnt periurban soil (188 vs 173 microg/kg), about seven times the 26 microg/kg measured in unburnt rural soil, which furthermore contained no detectable quantities of the highest molecular weight PAHs typical of traffic and other urban sources, as the periurban soils did. At the burnt site, PAH levels fell along the months (the total PAH level from 188 to 119 microg/kg), apparently as the result of rainfall and the prevention of further input from the atmosphere by the overlying layer of wood ash, which had a very high PAH adsorption capacity (1169 microg/kg) and did not itself appear to act as a source of PAHs. PAH transport may have been assisted by increased mobilization of PAHs associated with dissolvable organic matter due to an increase in soil pH due to alkaline ash components.