CoChat
Sign Up
Cited by 107Fire effects on ecosystemsCoal and Its By-productsToxic Organic Pollutants Impact

Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

Open access
Sánchez-García, C., Santín, C., Neris, J., Sigmund, G., Otero, X.L., Manley, J., González-Rodríguez, G., Belcher, C.M. +8 more·2023·Environment International
DOI 10.1016/j.envint.2023.108065
Open this paper in CoChat — free accountOpen PDF

Abstract

The mobilisation of potentially harmful chemical constituents in wildfire ash can be a major consequence of wildfires, posing widespread societal risks. Knowledge of wildfire ash chemical composition is crucial to anticipate and mitigate these risks. Here we present a comprehensive dataset on the chemical characteristics of a wide range of wildfire ashes (42 types and a total of 148 samples) from wildfires across the globe and examine their potential societal and environmental implications. An extensive review of studies analysing chemical composition in ash was also performed to complement and compare our ash dataset. Most ashes in our dataset had an alkaline reaction (mean pH 8.8, ranging between 6 – 11.2). Important constituents of wildfire ash were organic carbon (mean: 204 g kg-1), calcium, aluminium, and iron (mean: 47.9, 17.9 and 17.1 g kg-1). Mean nitrogen and phosphorus ranged between 1 - 25 g kg-1, and between 0.2 to 9.9 g kg-1, respectively. The largest concentrations of metals of concern for human and ecosystem health were observed for manganese (mean: 1488 mg kg-1; three ecosystems > 1000 mg kg-1), zinc (mean: 181 mg kg-1; two ecosystems > 500 mg kg-1) and lead (mean: 66.9 mg kg-1; two ecosystems > 200 mg kg-1). Burn severity and sampling timing were key factors influencing ash chemical characteristics like pH, carbon and nitrogen concentrations. The highest readily dissolvable fractions (as a % of ash dry weight) in water were observed for sodium (18%) and magnesium (11.4%). Although concentrations of elements of concern were very close to, or exceeded international contamination standards in some ashes, the actual effect of ash will depend on factors like ash loads and the dilution into environmental matrices such as water, soil and sediment. Our approach can serve as an initial methodological standardisation of wildfire ash sampling and chemical analysis protocols.

Verified 2026-10-06 · 1 reference not checked yet

AI snapshot

Written from the paper’s full text.

TL;DR

This study compiles and analyzes chemical characteristics of 42 wildfire ash types (148 samples) from 29 sites across 8 countries and 11 ecosystems, comparing them with prior ash studies and international contamination guidelines. It finds highly variable, generally alkaline ash rich in organic carbon and calcium, with burn severity and rainfall/sampling timing as key controls, and some ashes approaching or exceeding contaminant thresholds.

Key findings

  • Ash was generally alkaline: mean pH 8.8 (range 6–11.2), mean EC 1,330 µS cm⁻¹ (32.5–13,700). Major constituents included organic carbon (mean 204 g kg⁻¹; range 37–450), Ca (47.9 g kg⁻¹; 1.3–215), Al (17.9 g kg⁻¹; 0.6–69.3), and Fe (17.1 g kg⁻¹; 0.6–77.2); mean N was 7.8 g kg⁻¹ (1–25) and mean P 2.5 g kg⁻¹ (0.2–9.9).
  • Metals of concern had mean concentrations of Mn 1,488 mg kg⁻¹ (34.5–15,350), Zn 181 mg kg⁻¹ (25.5–1,016), and Pb 66.9 mg kg⁻¹ (1–782). The highest readily dissolvable fractions in water were Na (18%) and Mg (11.4%), followed by Ca (4.6%) and P (1.7%); Mn, Al, and Fe dissolved least (0.02–0.3%).
  • Burn severity and rainfall/sampling timing influenced ash chemistry. High vs low severity ash had higher pH (8.9 vs 8.6), Ca (53.6 vs 37.5 g kg⁻¹), Al (22.3 vs 9.9 g kg⁻¹), and Fe (20.1 vs 11.7 g kg⁻¹), but lower OC (119 vs 362 g kg⁻¹) and N (6.2 vs 10.7 g kg⁻¹). Cluster analysis separated most pre-rainfall ashes from post-rainfall ashes, with post-rainfall ashes showing lower pH/EC and lower soluble base cations, and higher relative Al and Fe.
  • Some ashes approached or exceeded guidelines: NETHER peatland Pb (782 mg kg⁻¹) exceeded all cited international guidelines for fertilising products, soils, and sediments; Ni in SPAMA (54.0), MUSA-H (64.0), and UKSWANP (61.3 mg kg⁻¹) was slightly above EU organic fertiliser (50) and Australian sediment (52) levels; NETHER Zn (1,016 mg kg⁻¹) exceeded guidelines except EU inorganic fertiliser (1,500 mg kg⁻¹); NETHER Cu (99 mg kg⁻¹) was close to the Canadian sediment maximum (110 mg kg⁻¹). The paper states average P and Mn slightly exceeded Canadian threshold levels for contaminated sediments.

Methods

  • Dataset: 42 ash types from 148 samples collected at 29 sites in 8 countries (Australia, Austria, Canada, South Africa, Spain, The Netherlands, United Kingdom, USA), spanning 11 ecosystems. Sampling used transects or composite sampling; 15 ash types were collected within 7 days and 27 between 1 week and 3 months after burning; 20 of 42 ash types received rain before sampling.
  • Chemical analyses: pH and EC in water (1:20 ash-to-water); total C and N by Leco TruSpec CHN; major nutrients, metals, and metalloids by microwave-assisted acid digestion (EPA 3051A) and ICP-OES; carbonates by calcimeter; water-extractable elements by leaching test (1:20, 5 min shake, 0.45 µm filtration); selected samples by XRD and FE-SEM. An extensive review of 16 previous ash-composition studies complemented the dataset.
  • Statistics: median per ash type, then mean of medians; Spearman correlations; coefficient of variation; hierarchical clustering (Ward’s method) followed by k-means (n = 3); logistic regression with cross-validation; linear mixed models controlling for rainfall and ecosystem; ANOVA with Tukey post-hoc tests. Cluster 3 was excluded from some analyses due to extreme values.

Limitations

  • The paper states no standard procedure exists for sampling wildfire ash; the methods used are a first approach to standardisation, and an interlaboratory comparison is recommended. It also notes dissolved-fraction estimates are conservative because of the high water:sample ratio (1:20) and short shaking time (5 min), with actual effects depending on dilution into environmental matrices.
  • The paper states it did not examine other potentially hazardous ash constituents such as PAHs, cyanide, chloride, sulphate, and environmentally persistent free radicals; lithology and geogenic concentrations were not considered; and ash loads, fire-affected area, fuel type/structure/loads, and post-fire climatic/hydrological controls need further research.
  • Evident from the text: sampling before vs after rainfall is confounded with ash age/time-since-fire; cluster 3 ashes (NETHER, AUSTRIA, UKSWANP) were excluded from some analyses due to extreme values; and comparisons of burn severity across ecosystems should be made cautiously because fire behaviour and combustion dynamics differ.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1016/j.envint.2023.108065

Cites

90 of 91 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 52 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The highest readily dissolvable fraction in water was for sodium, at 18% of ash dry weight.

    “The highest readily dissolvable fractions (as a % of ash dry weight) in water were observed for sodium (18 %) and magnesium (11.4 %).”
    Quote in the paperNot a substantial claim
  • Findingcitation

    For the South African sub-tropical savanna sites (SAPB1, SAPB3, SAMB), total C contents in ash were an order of magnitude higher than in pre- and post-burn soils.

    “Similarly, for the study sites from the sub-tropical savanna in South Africa (SAPB1, SAPB3 and SAMB), we observed total C contents in the ash an order of magnitude higher than in the pre-and post-burn soils (Sánchez-García et al., 2021).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sánchez-García et al., 2021 source

      Not checked in the free run.

  • Findingown data

    Mean P in ash was 2.5 g kg−1.

    “Mean Mg and P in the ash were 5.4 and 2.5 g kg -1 ash (Table 3), respectively, and were similar to those reported in the literature (e.g., Brito et al., 2017;Ulery et al., 1993; Table 1).”
    Quote in the paperNot a substantial claim
  • Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    Mean organic carbon concentration in wildfire ash was 204 g kg−1.

    “Important constituents of wildfire ash were organic carbon (mean: 204 g kg -1 ), calcium, aluminium, and iron (mean: 47.9, 17.9 and 17.1 g kg -1 ).”
    Quote in the paperNot a substantial claim
  • Findingown data

    The sum of OC and IC in field samples was 215 g kg−1 ash.

    “The sum of OC and IC in our field samples (215 g kg -1 ash; Table 3) is within the overall ranges observed for total C in previous studies (50 -460 g kg -1 ; Table 1; e.g., Alshehri et al., 2002;Costa et al., 2014;Pereira et al., 2012;Ulery et al., 1993).”
    Quote in the paperNot a substantial claim
  • May combine two claims. 41
  • Classified as probably not a substantial claim. 14
  • The quote only partly states this claim. 7

  • May combine two claims.

    Findingown data

    After carbon, calcium was the most abundant analysed component in the ash, with average concentration 47.9 g kg−1 and range 5.9-209 g kg−1.

    “After C, Ca was the most abundant analysed component in the ash (average concentration 47.9 g kg -1 ash; ranging between 5.9 and 209 g kg -1 in ash from peatland and temperate mixed forest; Table 3 and 5).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The largest concentration of lead among metals of concern was mean 66.9 mg kg−1, with two ecosystems >200 mg kg−1.

    “The largest concentrations of metals of concern for human and ecosystem health were observed for manganese (mean: 1488 mg kg -1 ; three ecosystems > 1000 mg kg -1 ), zinc (mean: 181 mg kg -1 ; two ecosystems > 500 mg kg -1 ) and lead (mean: 66.9 mg kg -1 ; two ecosystems > 200 mg kg -1 ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Mean N content in ash was 7.8 g kg−1 (0.78%), ranging from 3 g kg−1 in temperate shrubland to 17.5 g kg−1 in upland grassland.

    “Mean N content in the ash was 7.8 g kg -1 ash (0.78 %), ranging from 3 g kg -1 (0.30 %), in temperate shrubland, to 17.5 g kg -1 (1.75 %) in upland grassland (Table 3 and 5).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The largest concentration of zinc among metals of concern was mean 181 mg kg−1, with two ecosystems >500 mg kg−1.

    “The largest concentrations of metals of concern for human and ecosystem health were observed for manganese (mean: 1488 mg kg -1 ; three ecosystems > 1000 mg kg -1 ), zinc (mean: 181 mg kg -1 ; two ecosystems > 500 mg kg -1 ) and lead (mean: 66.9 mg kg -1 ; two ecosystems > 200 mg kg -1 ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation

    Mean Mg and P were similar to those reported in the literature.

    “Mean Mg and P in the ash were 5.4 and 2.5 g kg -1 ash (Table 3), respectively, and were similar to those reported in the literature (e.g., Brito et al., 2017;Ulery et al., 1993; Table 1).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Brito et al., 2017 source

      Not checked in the free run.

    • cites Ulery et al., 1993 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    Most ashes in the dataset had an alkaline reaction, with mean pH 8.8 and range 6-11.2.

    “Most ashes in our dataset had an alkaline reaction (mean pH 8.8, ranging between 6 and 11.2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Carbon was the main ash component, with 96% of this C being in organic form.

    “Of the chemical elements analysed, carbon was the main ash component, with a 96 % of this C being in organic form (OC; mean: 204 g kg -1 ash; Table 3).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing).

    Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The highest readily dissolvable fraction in water was for magnesium, at 11.4% of ash dry weight.

    “The highest readily dissolvable fractions (as a % of ash dry weight) in water were observed for sodium (18 %) and magnesium (11.4 %).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The largest concentration of manganese among metals of concern was mean 1488 mg kg−1, with three ecosystems >1000 mg kg−1.

    “The largest concentrations of metals of concern for human and ecosystem health were observed for manganese (mean: 1488 mg kg -1 ; three ecosystems > 1000 mg kg -1 ), zinc (mean: 181 mg kg -1 ; two ecosystems > 500 mg kg -1 ) and lead (mean: 66.9 mg kg -1 ; two ecosystems > 200 mg kg -1 ).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Microcline, muscovite, and albite are frequently observed, while hornblende, andesine, and biotite are rare.

    “Microcline, muscovite and albite are also frequently observed, with hornblende, andesine or biotite being rare.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Al and Fe were the third and fourth most abundant analysed elements in the ash, after C and Ca, with mean Al 17.9 g kg−1 and Fe 17.1 g kg−1.

    “Al and Fe were the third and fourth most abundant analysed elements in the ash, after C and Ca, with similar mean values (Al: 17.9 g kg -1 ash; Fe: 17.1 g kg -1 ash; Table 3), which were closer to the upper values of the overall ranges reported in previous studies (Al: 2.30 -19.0 g kg -1 , Fe: 0.10 -12.3 g kg -1 ; e.g., Brito et al., 2017;Ulery et al., 1993; Table 1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    pH in ash from temperate eucalypt forest ranged from 6 to 11.1, with the lowest pH values collected after rainfall.

    “pH in ash from temperate eucalypt forest range from 6 to 11.1 (Table 5), with the lowest pH values having been collected after rainfall (Table S1).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Cu in NETHER ash (99.0 mg kg-1) was close to the Canadian maximum level for sediments (110 mg kg-1), and Zn in the same ash (1,016 mg kg-1) exceeded international guidelines except the EU regulation on inorganic fertilisers (1,500 mg kg-1).

    “Copper in the NETHER ash (99.0 mg kg -1 ) was close to the Canadian maximum level for sediments (110 mg kg -1 ), and Zn in the same ash exceeded international guidelines (1,016 mg kg -1 ), except for the EU regulation on inorganic fertilisers (1,500 mg kg -1 ).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: There are no existing guidelines for potentially hazardous ash.

  • May combine two claims.

    Findingown data

    Ni concentrations in SPAMA, MUSA-H, and UKSWANP ash (54.0, 64.0, and 61.3 mg kg-1) were slightly above European guidelines for organic fertilisers and Australian maximum sediment contamination levels.

    “for SPAMA (Mediterranean conifer forest), and MUSA-H and UKSWANP ash (both temperate conifer forests) Ni concentrations (54.0, 64.0 and 61.3 mg kg -1 , respectively) were slightly above the European guidelines for organic fertilisers and the Australian's maximum sediment contamination levels (50.0 and 52.0 mg kg -1 , respectively).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: There are no existing guidelines for potentially hazardous ash.

  • May combine two claims.

    Findingown data

    Among ecosystems, the lowest pH and EC values were in peatland ash (pH 7.1, EC 237 μS cm-1) and the highest in sub-tropical savanna ash (pH 10.1, EC 6,943 μS cm-1).

    “Among ecosystems, the lowest pH and EC values were observed in ash from peatland (pH: 7.1, EC: 237 μS cm -1 ; Table 5) and the highest in sub-tropical savanna (pH:10.1,EC: 6,943 μS cm -1 ; Table 5).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Sampling before rainfall seemed a determining factor for cluster assignment: 12 of 14 cluster 1 ash types were collected before rainfall, and 17 of 25 cluster 2 ash types were collected post-rainfall.

    “sampling before rainfall seemed, a priori, a determining factor of whether the ash types were classified in cluster 1 or 2, with 12 out of 14 ash types in cluster 1 having been collected before any rainfall, and 17 out of 25 ash types in cluster 2 collected post-rainfall (Table 2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Mean concentrations of elements in the wildfire ash generally fell below international maximum levels for fertilisers, soil, and sediments, except P and Mn, which slightly exceeded Canadian threshold levels for contaminated sediments.

    “In general, the mean concentration of elements observed in the wildfire ash fall below the international maximum levels for fertilisers, soil and sediments presented in Table 7. Exceptions are P and Mn, with average concentrations slightly exceeding the Canadian's threshold levels for contaminated sediments.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: There are no existing guidelines for potentially hazardous ash.

  • May combine two claims.

    Findingreasoning

    Al and Fe were higher in high severity ash: Al from 9.90 to 22.3 g kg-1 and Fe from 11.7 to 20.1 g kg-1 in low vs high burn severity ash.

    “Al and Fe were also higher in the high severity ash (Al: from 9.90 to 22.3 g kg -1 , Fe: from 11.7 to 20.1 g kg -1 in low and high burn severity ash, respectively; Table 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Previous studies generally reported dissolved element ranges in the lower end of the ranges reported here, except Pereira et al. (2012), whose Mediterranean conifer forest values were closer to the upper ranges of this study.

    “in general, the ranges reported in the aforementioned studies are in the lower end of the ranges reported here.An exception is the study by Pereira et al. (2012) whose dissolved concentration values from Mediterranean conifer forest are closer to the upper ranges reported in this study.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Pereira et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    In deionized-water leachates, Na and Mg were dissolved the most (18% and 11.4%), followed by Ca (4.6%) and P (1.7%); Mn, Al, and Fe were dissolved the least (0.02-0.3%).

    “where Na and Mg were dissolved the most (18 and 11.4 %, respectively), followed by Ca (4.6 %) and P (1.7 %).Mn, Al and Fe were dissolved the least with fractions ranging from 0.02 to 0.3 % (Table 4).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Quartz is present in all samples, in variable proportions from 9% to 84%.

    “Quartz is present in all samples although in variable proportions (9-84 %; Table 6).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For most samples, ash pH was alkaline, with a mean of 8.8 and overall values ranging from 6 to 11.2.

    “For most samples ash pH was alkaline, with a mean value of 8.8, and overall values ranging from 6 to 11.2 (Table 4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The average EC in deionized-water leachates was 1,330 μS cm-1, with values ranging from 32.5 to 13,700 μS cm-1.

    “Regarding EC, an average of 1,330 μS cm -1 in the deionized-water leachates was found, with values ranging from 32.5 to 13,700 μS cm -1 (Table 4).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    No significant differences were observed between low and high burn severity ash for Mn, Ni, Cu, Zn, Pb, and Hg, nor for most dissolved components.

    “No significant differences were observed between ash from low and high burn severity for the remaining metals (Mn, Ni, Cu, Zn, Pb and Hg; Table 3), nor for most of the dissolved components (Table 4, S6).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    Concentrations of Pb, Cu, Hg, Ni, Cr, and Cd in the wildfire ash were below 100 mg kg-1, similar to previous studies.

    “Lower concentrations (<100 mg kg -1 ) were obtained for the remaining metals analysed (i.e., Pb, Cu, Hg, Ni, Cr, and Cd) similar to the concentrations reported in previous studies (e.g., Brito et al., 2017;Campos et al., 2016;Santos et al., 2023; Table 1).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Brito et al., 2017 source

      Not checked in the free run.

    • cites Campos et al., 2016 source

      Not checked in the free run.

    • cites Santos et al., 2023 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingcitation

    Follow-up analysis on AUSTRIA ash showed an absence of dissolved Hg in the water.

    “Follow-up analysis on the AUSTRIA ash showed an absence of dissolved Hg in the water (Sigmund, 2022, pers. comm.)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Sigmund, 2022, pers. comm.

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    Cluster 2 had significantly lower pH, EC, P, Ca, Mg, Na, Zn, dPO4, dMg, and dNa, and significantly higher Al and Fe than cluster 1.

    “Cluster 2 exhibits significantly lower pH, EC and lower concentrations of P, Ca, Mg, Na, Zn, dPO 4 , dMg, and dNa, and significantly higher concentrations of Al and Fe than cluster 1 (Fig. S4 and S5).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Pb observed in wildfire ash in this study was 66.9 mg kg-1 (range 1-782).

    “| Pb | 66.9 | 120 | 120 | 220 | 250 | 530 | 82/2.6* |”
    • Also stated in: § 5. Conclusion · plain
      “| | (1-782) | | | | | | |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Ni observed in wildfire ash in this study was 22.1 mg kg-1 (range 1.7-99).

    “| Ni | 22.1 | 50 | 100 | 52 | 75 | 210 | 15,000 |”
    • Also stated in: § 5. Conclusion · plain
      “| | (1.7-99) | | | | | | |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingnone given

    Important constituents of wildfire ash include OC (mean 204 g kg-1; range 37-450), Ca (47.9 g kg-1; 1.3-215), Al (17.9 g kg-1; 0.6-69.3), and Fe (17.1 g kg-1; 0.6-77.2).

    “Important constituents of wildfire ash include OC (mean value 204 g kg -1 ; ranging between 37 and 450 g kg -1 ), Ca (47.9 g kg -1 ; 1.3 -215 g kg -1 ), Al (17.9 g kg -1 ; 0.6 -69.3 g kg -1 ), and Fe (17.1 g kg -1 ; 0.6 -77.2 g kg -1 ).”
    Quote in the paperSubstantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Cd observed in wildfire ash in this study was 0.3 mg kg-1 (range 0.08-1.1).

    “| Cd | 0.3 | 1.5 | 3-60 | 10 | 10 | 12 | 2100 |”
    • Also stated in: § 5. Conclusion · plain
      “| | (0.08-1.1) | | | | | | |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Average concentrations of chemical species of concern for environmental and human health in wildfire ash were below international contamination standards for several environmental matrices and products, except in a few ash types (NETHER, AUSTRIA, and UKS-WANP) where concentrations were very close to or exceeded thresholds.

    “Average concentrations of chemical species of concern for environmental and human health in wildfire ash were below international contamination standards for several environmental matrices and products, except in a few ash types (NETHER, AUSTRIA, and UKS-WANP) in which the concentrations were very close or exceeded contamination thresholds.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: There are no existing guidelines for potentially hazardous ash.

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Cr observed in wildfire ash in this study was 34 mg kg-1 (range 10-71.6).

    “| Cr | 34 | ns | ns | 370 | 110 | 380 | ns |”
    • Also stated in: § 5. Conclusion · plain
      “| | (10-71.6) | | | | | | |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of P observed in wildfire ash in this study was 2500 mg kg-1 (range 200-9900).

    “| P | 2500 | ns | ns | ns | 2000 | ns | ns |”
    • Also stated in: § 5. Conclusion · plain
      “| | (200-9900) | | | | | | |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Zn observed in wildfire ash in this study was 181 mg kg-1 (range 25.5-1016).

    “| Zn | 181 | 800 | 1500 | 410 | 820 | 720 | ns |”
    • Also stated in: § 5. Conclusion · plain
      “| | (25.5-1016) | | | | | | |”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    The mean concentration of Mn observed in wildfire ash in this study was 1488 mg kg-1 (range 34.5-15350).

    “| Mn | 1488 | ns | ns | ns | 1100 | ns | ns |”
    • Also stated in: § 5. Conclusion · plain
      “| | (34.5-15350) | | | | | | |”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    For the NAUS site, Santín et al. (2015b) reported 4 and 3.8% total C for unburnt and burnt soil, respectively, while 24.7% total C was observed in ash from the same fire.

    “For example, for the NAUS site (temperate eucalypt forest, Table 2), Santín et al. (2015b) reported 4 and 3.8 % (40.0 and 38.1 g kg -1 of total C) for unburnt and burnt soil, respectively, while 24.7 % (247 g kg -1 of total C) was observed in the ash from the same fire.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Santín et al., 2015b

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    The main contributor to ash is usually vegetation, and ash plays an important role in mobilizing and redistributing C in the landscape after fire.

    “This is because the main contributor to ash is usually vegetation and highlights the important role of ash in mobilizing and redistributing C in the landscape after fire (Bodí et al., 2014;Santín et al., 2012).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Bodí et al., 2014 source

      Not checked in the free run.

    • cites Santín et al., 2012 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductreasoning

    The study used a standard analysis approach to facilitate comparison across study sites.

    “We address this knowledge gap here by analysing and evaluating the chemical characteristics of wildfire ash produced in a wide range of scenarios and following a standard analysis approach to facilitate comparison across study sites.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationnone given
    § Chemical characteristics of wildfire ash across the globe and their environmental and socio-economic implications

    The paper's approach can serve as an initial methodological standardisation of wildfire ash sampling and chemical analysis protocols.

    “Our approach can serve as an initial methodological standardisation of wildfire ash sampling and chemical analysis protocols.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    When deposited and incorporated into soil, typically alkaline and nutrient-rich ash can induce changes in soil pH and represents a nutrient flux to soils.

    “When deposited and incorporated into the soil, the typically alkaline and nutrient-rich ash can induce changes in soil pH and represents a nutrient flux to soils (the so-called 'fertilizing effect') (Bodí et al., 2014;Maass, 1995).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Bodí et al., 2014 source

      Not checked in the free run.

    • cites Maass, 1995

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The effects of wildfire ash are wide-ranging, and its mobilization can pose a risk to human health, including respiratory problems through ash inhalation by firefighters, post-fire restoration teams, and the public nearby or downwind.

    “The effects of wildfire ash are wide-ranging, and its mobilization can also pose a risk to human health.These include, for example, respiratory problems through ash inhalation by firefighters or post-fire restoration teams, and to the public nearby or downwind of active fires and recently burnt areas (e.g., Alexakis, 2020;Wan et al., 2021).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Alexakis, 2020 source

      Not checked in the free run.

    • cites Wan et al., 2021 source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Wildfire ash was largely overlooked as a topic of research for several decades, partly due to its high mobility and rapid redistribution after fire, which makes it more challenging to collect than other post-fire components.

    “For several decades, and despite its ubiquitous presence and potential importance, wildfire ash was largely overlooked as a topic of research.This is partly due to its high mobility, and hence rapid redistribution after fire, which makes wildfire ash more challenging to collect than other components of the post-fire environment, such as fireaffected soils or the eroded sediment (Bodí et al., 2014)”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Bodí et al., 2014 source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous research indicated that ash chemical composition is highly heterogeneous even for ash from the same or similar ecosystems.

    “This previous research indicated that ash chemical composition is highly heterogeneous even for ash from the same or similar ecosystems (Table 1).”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    All fitted models met the assumptions concerning normally distributed residuals, homoscedasticity, and linearity.

    “All variables were transformed (square root or log) to satisfy assumptions of normality, and all fitted models met the assumptions concerning normally distributed residuals, homoscedasticity, and linearity.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    Different sampling and laboratory techniques used across studies make straightforward comparison difficult and highlight the need for standardized approaches.

    “The differences in ash characteristics among ecosystems are also very notable when comparing values among studies (Table 1), however, the different sampling and laboratory techniques used across the studies makes a straightforward comparison difficult and highlights the need for standardized approaches.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The nutrients, metals, and metalloids analyzed in this study represent the most common but not the only constituents of wildfire ash.

    “The nutrients, metals, and metalloids analyzed in this study represent the most common but not the only constituents of wildfire ash.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductown data

    In this study, sampling before or after rainfall is also an indication of ash age, with post-rainfall ash coinciding with later post-fire sampling times.

    “In this study sampling before or after rainfall is also an indication of the age of the ash (i.e., the time elapsed since the fire to collection), with ash collected post-rainfall coinciding with the later post-fire sampling times (Table S1).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    Lithology and geogenic concentrations, although not considered in this study, might be important drivers of ash composition and reactivity and contribute to higher geochemical heterogeneity in ash.

    “lithology and geogenic concentrations, although not considered in this study, might be an important driver of ash composition and reactivity and contribute towards higher geochemical heterogeneity in ash.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S2 (checkable), S3 (load-bearing).

    Interpretationreasoning

    A comparison of burn severities among ecosystems needs to be made with caution because fire behaviour and combustion dynamics that result in a particular burn severity may differ.

    “A comparison of burn severities among ecosystems needs to be made with caution as the fire behaviour and combustion dynamics that result in a particular burn severity may differ (e.g., smoulderingdominated combustion in peatland fuels vs. flaming-dominated combustion in other fuels).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    With aging, ash pH may decrease as well as the concentration of some elements.

    “Therefore with “aging”, ash pH may decrease as well as the concentration of some elements.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    Considering both rainfall and sampling timing is important when examining chemical properties and contamination risk in older ash; failure to do so might lead to inaccurate estimations of nutrient inputs and ash toxicity.

    “These observations highlight the importance of considering both rainfall and sampling timing (i.e., time-sincefire) when examining chemical properties and the potential contamination risk in older ash.Failure to do so might lead to inaccurate estimations of the input of chemical component in soil and water and the potential toxicity of ash both airborne and in solution.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Not only minerals in plants but also some of the mineral fraction from soil becomes part of the ash layer, sometimes in substantial quantities.

    “indicating that not only minerals in plants, but also some of the mineral fraction from soil becomes part of the ash layer, sometimes in substantial quantities.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Interpretationcitation

    Although higher OC, N, and P concentrations are typically found in low burn severity ash, the higher ash loads produced in high severity fires might result in larger nutrient delivery to aquatic ecosystems.

    “while higher concentrations of OC, N and P are typically found in ash from low burn severity, the higher ash loads produced in high severity fires might result in a larger nutrient delivery to aquatic ecosystems (Santín et al., 2015b).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Santín et al., 2015b

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    The higher pH and larger amount of some toxic metals and metalloids typically observed in high severity ash might be associated with a higher contamination risk.

    “the higher pH and larger amount of some toxic metals and metalloids typically observed in high severity ash might be associated with a higher contamination risk.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    pH controls the solubility of most elements; higher pH in high burn severity ash could directly influence the contamination potential of wildfire ash when in contact with water.

    “pH, which controls the solubility of most elements, was higher in ash from high burn severity, and this could have a direct influence on the contamination potential of wildfire ash when in contact with water.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S4 (based).

    Interpretationnone given

    The ash collection method, such as brush versus vacuum, will affect key determining factors of ash chemical composition such as the amount of mineral soil collected within the ash.

    “other aspects like the ash collection method (e.g., brush vs. vacuum) will affect key determining factors of ash chemical composition such as the amount of mineral soil that is collected within the ash.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: No standard procedure currently exists for sampling wildfire ash.
57 of 57

  • The paper relies on this without support.

    A large fraction of the chemical components mobilised during a fire are associated with the ash.

    “Although most research and public attention regarding contaminants and fire are focused on the mobilization of elements through smoke (Burke et al., 2021;Cascio, 2018;Chen et al., 2021;Xu et al., 2020), a large fraction of the chemical components mobilised during a fire are associated with the ash.”

  • The paper relies on this without support.

    The 42 ash types and 148 samples are representative of wildfire ash across the globe.

    “Here we present a comprehensive dataset on the chemical characteristics of a wide range of wildfire ashes (42 types and a total of 148 samples) from wildfires across the globe and examine their potential societal and environmental implications.”

  • The paper relies on this without support.

    International contamination standards are appropriate benchmarks for assessing potential effects of ash.

    “Although concentrations of elements of concern were very close to, or exceeded international contamination standards in some ashes, the actual effect of ash will depend on factors like ash loads and the dilution into environmental matrices such as water, soil and sediment.”

  • The paper relies on this without support.

    No standard procedure currently exists for sampling wildfire ash.

    “It is important to highlight that no standard procedure currently exists for sampling wildfire ash.”

  • The paper relies on this without support.

    No single standard procedure currently exists for the analysis of readily dissolvable elements in ash.

    “Given that no single standard procedure currently exists for the analysis of readily dissolvable elements in ash”

  • The paper relies on this without support.

    There are no existing guidelines for potentially hazardous ash.

    “Since there are no existing guidelines for potentially hazardous ash”
6 of 6

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Overall organic-carbon mean does not match severity-group means

    Minor

    Table 3 gives 15 low-severity and 27 high-severity ash types. Their reported OC means of 362 and 119 g kg -1 yield an overall mean of 205.8 g kg -1, not the reported 204; rounding the group means cannot account for the difference.

    Reported 204 · recomputed 207.902439

  • Arsenic mean also exceeds a listed contamination threshold

    Minor

    The text names only P and Mn as exceptions to its claim that mean concentrations fall below the Table 7 levels. Table 7 also gives a mean arsenic concentration of 3.5 mg kg -1, above its listed US EPA residential-soil screening level of 0.7 mg kg -1.

  • Ecosystem aluminium maximum exceeds the overall maximum

    Minor

    Table 5 gives 226 g kg -1 as the Mediterranean shrubland aluminium maximum, but Table 3 gives 69.3 g kg -1 as the maximum across all ash types.

  • Temperate mixed-forest lead value differs from Table 5

    Minor

    The text reports 453 mg kg -1 for temperate mixed-forest ash, while Table 5 reports 435 mg kg -1 for that ecosystem.

4 of 4

Cites

Flagged first, then by citations

Cited by

Sorted by citations

Related

Authors
Sánchez-García, C., Santín, C., Neris, J., Sigmund, G., Otero, X. L., Manley, J., González-Rodríguez, G., Belcher, C. M., Cerdà, A., Marcotte, A. L., Murphy, S. F., Rhoades, C. C., Sheridan, G., Strydom, T., Robichaud, P. R., & Doerr, S. H.
Affiliations
  • Swansea University (GB)
  • Consejo Superior de Investigaciones Científicas (ES)
  • Universidad de La Laguna (ES)
  • University of Vienna (AT)
  • Universidade de Santiago de Compostela (ES)
  • University of Exeter (GB)
  • Universitat de València (ES)
  • Wageningen University & Research (NL)
  • United States Geological Survey (US)
  • US Forest Service (US)
  • The University of Melbourne (AU)
  • South African National Parks (ZA)
ORCID
Venue
Environment International
Publisher
Elsevier BV
Published
2023-08
Volume
178
Pages
108065
ISSN
0160-4120 (ISSN-L)
DOI
10.1016/j.envint.2023.108065
OpenAlex
W4381948677
Cited by
107
References
90
Citations by year
2026: 37 · 2025: 43 · 2024: 27
FWCI
11.99
Type
journal article
Language
en
Open access
Licence
Locations
  • Environment International (publishedVersion, cc-by-nc-nd)
  • SSRN Electronic Journal (publishedVersion)
  • PubMed (publishedVersion)
  • Socio-Environmental Systems Modeling (submittedVersion, cc-by)
  • Repository of Digital Objects for Teaching Research and Culture (University of Valencia) (submittedVersion, cc-by-nc)
  • Cronfa (Swansea University) (submittedVersion, cc-by)
  • DIGITAL.CSIC (Spanish National Research Council (CSIC)) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Hispana (submittedVersion, cc-by)
Funders
  • Horizon 2020 Framework Programme (101003890, 860787)
  • Natural Environment Research Council (NE/R011125/1, NE/T003553/1)
  • Leverhulme Trust (RPG-2014-095)
  • European Commission
Topics
  • Physical Sciences › Environmental Science › Global and Planetary Change › Fire effects on ecosystems
  • Physical Sciences › Earth and Planetary Sciences › Geochemistry and Petrology › Coal and Its By-products
  • Physical Sciences › Environmental Science › Health, Toxicology and Mutagenesis › Toxic Organic Pollutants Impact
Keywords
wildfire ash, ash composition, heavy metals, manganese, zinc, lead, burn severity, organic carbon, nitrogen and phosphorus, water-soluble fraction, environmental contamination
MeSH terms
Wildfires, Carbon, Humans, Magnesium, Nitrogen, Socioeconomic Factors, Water, Ecosystem

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

Are you an author, or do you see a problem with this page? Request a review