1
|
Lopez AM, Pacheco JL, Fendorf S. Metal toxin threat in wildland fires determined by geology and fire severity. Nat Commun 2023; 14:8007. [PMID: 38086795 PMCID: PMC10716285 DOI: 10.1038/s41467-023-43101-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Accepted: 10/31/2023] [Indexed: 12/18/2023] Open
Abstract
Accentuated by climate change, catastrophic wildfires are a growing, distributed global public health risk from inhalation of smoke and dust. Underrecognized, however, are the health threats arising from fire-altered toxic metals natural to soils and plants. Here, we demonstrate that high temperatures during California wildfires catalyzed widespread transformation of chromium to its carcinogenic form in soil and ash, as hexavalent chromium, particularly in areas with metal-rich geologies (e.g., serpentinite). In wildfire ash, we observed dangerous levels (327-13,100 µg kg-1) of reactive hexavalent chromium in wind-dispersible particulates. Relatively dry post-fire weather contributed to the persistence of elevated hexavalent chromium in surficial soil layers for up to ten months post-fire. The geographic distribution of metal-rich soils and fire incidents illustrate the broad global threat of wildfire smoke- and dust-born metals to populations. Our findings provide new insights into why wildfire smoke exposure appears to be more hazardous to humans than pollution from other sources.
Collapse
Affiliation(s)
- Alandra Marie Lopez
- Earth System Science Department, Stanford University, Stanford, CA, 94305, USA
| | - Juan Lezama Pacheco
- Earth System Science Department, Stanford University, Stanford, CA, 94305, USA
| | - Scott Fendorf
- Earth System Science Department, Stanford University, Stanford, CA, 94305, USA.
| |
Collapse
|
2
|
Titus T, Robertson D, Sankey JB, Mastin L, Rengers F. A review of common natural disasters as analogs for asteroid impact effects and cascading hazards. NATURAL HAZARDS (DORDRECHT, NETHERLANDS) 2023; 116:1355-1402. [PMID: 36776703 PMCID: PMC9900588 DOI: 10.1007/s11069-022-05722-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 11/15/2022] [Indexed: 06/18/2023]
Abstract
Modern civilization has no collective experience with possible wide-ranging effects from a medium-sized asteroid impactor. Currently, modeling efforts that predict initial effects from a meteor impact or airburst provide needed information for initial preparation and evacuation plans, but longer-term cascading hazards are not typically considered. However, more common natural disasters, such as volcanic eruptions, earthquakes, wildfires, dust storms, and hurricanes, are likely analogs that can provide the scope and scale of these potential effects. These events, especially the larger events with cascading effects, are key for understanding the scope and complexity of mitigation, relief, and recovery efforts for a medium-sized asteroid impact event. This paper reviews the initial and cascading effects of these natural hazards, describes the state of the art for modeling these hazards, and discusses the relevance of these hazards to expected long-term effects of an asteroid impact. Emergency managers, resource managers and planners, and research scientists involved in mitigation and recovery efforts would likely derive significant benefit from a framework linking multiple hazard models to provide a seamless sequence of related forecasts.
Collapse
Affiliation(s)
- Timothy Titus
- Astrogeology Science Center, U.S. Geological Survey, Flagstaff, AZ USA
| | - D. Robertson
- NASA Ames Research Center, Mountain View, CA USA
| | - J. B. Sankey
- Southwest Biological Science Center, Grand Canyon Monitoring and Research Center, U.S. Geological Survey, Flagstaff, AZ USA
| | - L. Mastin
- U.S. Geological Survey Volcano Observatory, Vancouver, WA USA
| | - F. Rengers
- Geologic Hazards Science Center, U.S. Geological Survey, Golden, CO USA
| |
Collapse
|
3
|
Hamilton DS, Perron MMG, Bond TC, Bowie AR, Buchholz RR, Guieu C, Ito A, Maenhaut W, Myriokefalitakis S, Olgun N, Rathod SD, Schepanski K, Tagliabue A, Wagner R, Mahowald NM. Earth, Wind, Fire, and Pollution: Aerosol Nutrient Sources and Impacts on Ocean Biogeochemistry. ANNUAL REVIEW OF MARINE SCIENCE 2022; 14:303-330. [PMID: 34416126 DOI: 10.1146/annurev-marine-031921-013612] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
A key Earth system science question is the role of atmospheric deposition in supplying vital nutrients to the phytoplankton that form the base of marine food webs. Industrial and vehicular pollution, wildfires, volcanoes, biogenic debris, and desert dust all carry nutrients within their plumes throughout the globe. In remote ocean ecosystems, aerosol deposition represents an essential new source of nutrients for primary production. The large spatiotemporal variability in aerosols from myriad sources combined with the differential responses of marine biota to changing fluxes makes it crucially important to understand where, when, and how much nutrients from the atmosphere enter marine ecosystems. This review brings together existing literature, experimental evidence of impacts, and new atmospheric nutrient observations that can be compared with atmospheric and ocean biogeochemistry modeling. We evaluate the contribution and spatiotemporal variability of nutrient-bearing aerosols from desert dust, wildfire, volcanic, and anthropogenic sources, including the organic component, deposition fluxes, and oceanic impacts.
Collapse
Affiliation(s)
- Douglas S Hamilton
- Department of Earth and Atmospheric Science, Cornell University, Ithaca, New York 14853, USA;
| | - Morgane M G Perron
- Institute for Marine and Antarctic Studies, University of Tasmania, Battery Point, Tasmania 7004, Australia
| | - Tami C Bond
- Department of Mechanical Engineering, Colorado State University, Fort Collins, Colorado 80521, USA
| | - Andrew R Bowie
- Institute for Marine and Antarctic Studies, University of Tasmania, Battery Point, Tasmania 7004, Australia
| | - Rebecca R Buchholz
- Atmospheric Chemistry Observations and Modeling Laboratory, National Center for Atmospheric Research, Boulder, Colorado 80301, USA
| | - Cecile Guieu
- Laboratoire d'Océanographie de Villefranche, Sorbonne Université, CNRS, 06230 Villefranche-sur-Mer, France
| | - Akinori Ito
- Yokohama Institute for Earth Sciences, Japan Agency for Marine-Earth Science and Technology, Yokohama, Kanagawa 236-0001, Japan
| | - Willy Maenhaut
- Department of Chemistry, Ghent University, 9000 Ghent, Belgium
| | - Stelios Myriokefalitakis
- Institute for Environmental Research and Sustainable Development, National Observatory of Athens, 15236 Penteli, Greece
| | - Nazlı Olgun
- Climate and Marine Sciences Division, Eurasia Institute of Earth Sciences, Istanbul Technical University, 34469 Maslak, Istanbul, Turkey
| | - Sagar D Rathod
- Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80521, USA
| | - Kerstin Schepanski
- Institute of Meteorology, Freie Universität Berlin, 12165 Berlin, Germany
| | - Alessandro Tagliabue
- School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, United Kingdom
| | - Robert Wagner
- Leibniz Institute for Tropospheric Research, 04318 Leipzig, Germany
| | - Natalie M Mahowald
- Department of Earth and Atmospheric Science, Cornell University, Ithaca, New York 14853, USA;
| |
Collapse
|
4
|
Whicker JJ, Breshears DD, McNaughton M, Chastenet de Gery MJ, Bullock C. Radionuclide resuspension across ecosystems and environmental disturbances. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2021; 233:106586. [PMID: 33774592 DOI: 10.1016/j.jenvrad.2021.106586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 02/28/2021] [Accepted: 03/05/2021] [Indexed: 06/12/2023]
Abstract
Exposure assessment from radionuclides and other soil-bound contaminants often requires quantifying the amount of contaminant resuspended in the air. Rates and controlling factors of radionuclide resuspension and wind erosion of soil are clearly related but have largely been studied separately. Here, we review both and then integrate wind erosion measurements with the radiological resuspension paradigm to provide better estimates of resuspension factors across a broad range of ecosystems and environmental conditions. Radionuclide resuspension by wind was initially investigated during the era of aboveground nuclear weapons testing. Predictive dose models were developed from empirically-derived ratios of air and soil concentrations, otherwise called the resuspension factor. Resuspension factors were shown to generally predict radionuclide concentrations in air, but they were site-specific and largely derived from the arid and semi-arid environments surrounding nuclear weapons testing locations. In contrast, wind erosion studies from the agricultural and environmental sciences have produced more mechanistic models and a relatively robust data set of wind erosion rates and model parameters across a range of ecosystems. We sequentially show the mathematics linking measured sediment flux from wind erosion rate measurements to resuspension factors using the concept of transport capacity and its relationship to the deposition velocity. We also describe the conceptual framework describing how resuspension factors change through time and the mathematical models describing this decrease. We then show how vertical mass flux measurements across ecosystems were categorized and used to calculate ecosystem-based resuspension factors. These calculations allow generalized estimation of radionuclide resuspension factors across ecosystem types as a function of disturbance and as input for dose calculations.
Collapse
Affiliation(s)
- Jeffrey J Whicker
- Los Alamos National Laboratory, Mail Stop J978, Los Alamos, NM, 87545, USA.
| | - David D Breshears
- University of Arizona, School of Natural Resources, Institute for the Study of Planet Earth, Department of Ecology and Evolutionary Biology, Biological Sciences East 325, P.O. Box 210043, Tucson, AZ, 85721-0043, USA
| | - Michael McNaughton
- Los Alamos National Laboratory, Mail Stop J978, Los Alamos, NM, 87545, USA
| | | | - Christine Bullock
- Los Alamos National Laboratory, Mail Stop J978, Los Alamos, NM, 87545, USA
| |
Collapse
|
5
|
Duniway MC, Pfennigwerth AA, Fick SE, Nauman TW, Belnap J, Barger NN. Wind erosion and dust from
US
drylands: a review of causes, consequences, and solutions in a changing world. Ecosphere 2019. [DOI: 10.1002/ecs2.2650] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Affiliation(s)
- Michael C. Duniway
- U.S. Geological Survey Southwest Biological Science Center Moab Utah 84532 USA
| | - Alix A. Pfennigwerth
- U.S. Geological Survey Southwest Biological Science Center Moab Utah 84532 USA
- Department of Ecology and Evolutionary Biology University of Colorado at Boulder Boulder Colorado 80309 USA
| | - Stephen E. Fick
- U.S. Geological Survey Southwest Biological Science Center Moab Utah 84532 USA
- Department of Ecology and Evolutionary Biology University of Colorado at Boulder Boulder Colorado 80309 USA
| | - Travis W. Nauman
- U.S. Geological Survey Southwest Biological Science Center Moab Utah 84532 USA
| | - Jayne Belnap
- U.S. Geological Survey Southwest Biological Science Center Moab Utah 84532 USA
| | - Nichole N. Barger
- Department of Ecology and Evolutionary Biology University of Colorado at Boulder Boulder Colorado 80309 USA
| |
Collapse
|
6
|
Pi H, Sharratt B, Lei J. Windblown sediment transport and loss in a desert-oasis ecotone in the Tarim Basin. Sci Rep 2017; 7:7723. [PMID: 28798390 PMCID: PMC5552775 DOI: 10.1038/s41598-017-04971-4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Accepted: 05/22/2017] [Indexed: 11/17/2022] Open
Abstract
The Tarim Basin is regarded as one of the most highly erodible areas in China. Desert comprises 64% of the land use in the Basin, but the desert–oasis ecotone plays a prominent role in maintaining oasis ecological security and stability. Yet, little is known concerning the magnitude of windblown sediment transport in a desert-oasis ecotone. Therefore, aeolian sediment transport and loss was assessed from a desert-oasis experimental site located near Alaer City in the northwestern Tarim Basin. Sediment transport and factors governing transport were measured during three high wind events in 2012 and four events in 2013. Sediment transport was measured to a height of 10 m using passive aeolian airborne sediment samplers. The mass flux profile over the eroding surface was well represented by the power-law (R2 > 0.77). Sediment loss from the site ranged from 118 g m−2 for the 20–24Apr 2012 wind event to 2925 g m−2 for the 31Mar–11Apr 2012 event. Suspension accounted for 67.4 to 84.8% of sediment loss across all high wind events. Our results indicate the severity of wind erosion in a desert-oasis ecotone and thus encourage adoption of management practices that will enhance oasis ecological security.
Collapse
Affiliation(s)
- Huawei Pi
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, 830011, China.,University of Chinese Academy of Sciences, Beijing, 100049, China.,Washington State University, Pullman, WA, 99164, USA
| | - Brenton Sharratt
- USDA-ARS, 215 Johnson Hall, Washington State University, Pullman, WA, 99164, USA
| | - Jiaqiang Lei
- State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi, Xinjiang, 830011, China.
| |
Collapse
|
7
|
Duniway MC, Palmquist E, Miller ME. Evaluating rehabilitation efforts following the Milford Flat Fire: successes, failures, and controlling factors. Ecosphere 2015. [DOI: 10.1890/es14-00318.1] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
8
|
Sunlight and Soil–Litter Mixing: Drivers of Litter Decomposition in Drylands. PROGRESS IN BOTANY 2015. [DOI: 10.1007/978-3-319-08807-5_11] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
|
9
|
Michelotti EA, Whicker JJ, Eisele WF, Breshears DD, Kirchner TB. Modeling aeolian transport of soil-bound plutonium: considering infrequent but normal environmental disturbances is critical in estimating future dose. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2013; 120:73-80. [PMID: 23455230 DOI: 10.1016/j.jenvrad.2013.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 01/08/2013] [Accepted: 01/08/2013] [Indexed: 06/01/2023]
Abstract
Dose assessments typically consider environmental systems as static through time, but environmental disturbances such as drought and fire are normal, albeit infrequent, events that can impact dose-influential attributes of many environmental systems. These phenomena occur over time frames of decades or longer, and are likely to be exacerbated under projected warmer, drier climate. As with other types of dose assessment, the impacts of environmental disturbances are often overlooked when evaluating dose from aeolian transport of radionuclides and other contaminants. Especially lacking are predictions that account for potential changing vegetation cover effects on radionuclide transport over the long time frames required by regulations. A recently developed dynamic wind-transport model that included vegetation succession and environmental disturbance provides more realistic long-term predictability. This study utilized the model to estimate emission rates for aeolian transport, and compare atmospheric dispersion and deposition rates of airborne plutonium-contaminated soil into neighboring areas with and without environmental disturbances. Specifically, the objective of this study was to utilize the model results as input for a widely used dose assessment model (CAP-88). Our case study focused on low levels of residual plutonium found in soils from past operations at Los Alamos National Laboratory (LANL), in Los Alamos, NM, located in the semiarid southwestern USA. Calculations were conducted for different disturbance scenarios based on conditions associated with current climate, and a potential future drier and warmer climate. Known soil and sediment concentrations of plutonium were used to model dispersal and deposition of windblown residual plutonium, as a function of distance and direction. Environmental disturbances that affected vegetation cover included ground fire, crown fire, and drought, with reoccurrence rates for current climate based on site historical patterns. Using site-specific meteorology, accumulation rates of plutonium in soil were modeled in a variety of directions and distances from LANL sources. Model results suggest that without disturbances, areas downwind to the contaminated watershed would accumulate LANL-derived plutonium at a relatively slow rate (<0.01 Bq m(-2) yr(-1)). However, model results under more realistic assumptions that include environmental disturbances show accumulation rates more than an order-of-magnitude faster. More generally, this assessment highlights the broader need in radioecology and environmental health physics to consider infrequent but normal environmental disturbances in longer-term dose assessments.
Collapse
Affiliation(s)
- Erika A Michelotti
- Los Alamos National Laboratory, Environmental Stewardship Group, Mail Stop J978, Los Alamos, NM 87544, USA
| | | | | | | | | |
Collapse
|
10
|
Whicker JJ, Baltz D, Eisele WF, Hart OF, McNaughton MW, Green AA. Operational experience of continuous air monitoring of smoke for ²³⁹Pu during a wildfire. HEALTH PHYSICS 2012; 103:S161-S168. [PMID: 22739970 DOI: 10.1097/hp.0b013e318259f286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Smoke from a wildfire in northern New Mexico that moved along the border of the Los Alamos National Laboratory (LANL) was monitored for ²³⁹Pu in the event that the fire might cross into LANL property containing locations with low, but greater than background, levels of ²³⁹Pu and other alpha-emitting radionuclides. Three Environmental Continuous Air Monitors (ECAMs) in operation at LANL at the time of the fire provided near real-time measurements of the ²³⁹Pu in the smoke. Sampling data from routine measurements of PM-10 and PM-2.5 concentrations in the city of Los Alamos showed that smoke in the air rose during the fire to several hundred μg m⁻³, which produced limited visibility (several hundred meters) and resulted in poor air quality alerts for about a week-long period. Previous studies have shown that airborne dust can significantly impair continuous air monitors, so the purpose of this study was to assess the performance of the ECAMs under smoky conditions, which is important for many emergency response scenarios. Additionally, ECAMs are not required to be tested in smoke by ANSI standards, so there is little to no published data on performance of any ECAM while sampling smoke. Results show that the deployed ECAMs had reduced flow as the filter clogged with fine particles, but the goodness-of-fit parameter of the peak shape fitting algorithms and the minimum detectable concentration and dose were not impacted until the flow was reduced by more than about 20%, and even then they were within tolerable limits. Overall, ECAM performance was not impacted during the fire even under heavy smoke conditions and fluctuating radon levels, though changing the filters to limit any reductions in flow to less than 20% would maintain optimal ECAM performance.
Collapse
Affiliation(s)
- Jeffrey J Whicker
- Los Alamos National Laboratory, Mail Stop M996, Los Alamos, NM 87545, USA.
| | | | | | | | | | | |
Collapse
|
11
|
Copeland NS, Sharratt BS, Wu JQ, Foltz RB, Dooley JH. A wood-strand material for wind erosion control: effects on total sediment loss, PM10 vertical flux, and PM10 loss. JOURNAL OF ENVIRONMENTAL QUALITY 2009; 38:139-148. [PMID: 19141803 DOI: 10.2134/jeq2008.0115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Fugitive dust from eroding land poses risks to environmental quality and human health, and thus, is regulated nationally based on ambient air quality standards for particulate matter with mean aerodynamic diameter < or = 10 microm (PM10) established in the Clean Air Act. Agricultural straw has been widely used for rainfall-induced erosion control; however, its performance for wind erosion mitigation has been less studied, in part because straw is mobile at moderate wind velocities. A wood-based long-strand material has been developed for rainfall-induced erosion control and has shown operational promise for control of wind-induced erosion and dust emissions from disturbed sites. The purpose of this study was to evaluate the efficacy of both agricultural straw and wood-strand materials in controlling wind erosion and fugitive dust emissions under laboratory conditions. Wind tunnel tests were conducted to compare wood strands of several geometries to agricultural wheat straw and bare soil in terms of total sediment loss, PM10 vertical flux, and PM10 loss. Results indicate that the types of wood strands tested are stable at wind speeds of up to 18 m s(-1), while wheat straw is only stable at speeds of up to 6.5 m s(-1). Wood strands reduced total sediment loss and PM10 emissions by 90% as compared to bare soil across the range of wind speeds tested. Wheat straw did not reduce total sediment loss for the range of speeds tested, but did reduce PM10 emissions by 75% compared to a bare soil at wind speeds of up to 11 m s(-1).
Collapse
Affiliation(s)
- N S Copeland
- USDA Forest Service Rocky Mountain Research Stn., Moscow, ID 83843, USA.
| | | | | | | | | |
Collapse
|
12
|
Engle DL, Sickman JO, Moore CM, Esperanza AM, Melack JM, Keeley JE. Biogeochemical legacy of prescribed fire in a giant sequoia-mixed conifer forest: A 16-year record of watershed balances. ACTA ACUST UNITED AC 2008. [DOI: 10.1029/2006jg000391] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Diana L. Engle
- Marine Science Institute; University of California; Santa Barbara California USA
| | - James O. Sickman
- Department of Environmental Sciences; University of California; Riverside California USA
| | - Claudette M. Moore
- National Park Service, Inventory and Monitoring Program, Southwest Alaska Network; Katmai National Park and Preserve; King Salmon Alaska USA
| | - Annie M. Esperanza
- Division of Natural Resources; Sequoia and Kings Canyon National Parks; Three Rivers California USA
| | - John M. Melack
- Department of Ecology, Evolution, and Marine Biology and Donald Bren School of Environmental Science and Management; University of California; Santa Barbara California USA
| | - Jon E. Keeley
- U.S. Geological Survey, Western Ecological Research Center; Sequoia and Kings Canyon National Parks; Three Rivers California USA
- Department of Ecology and Evolutionary Biology; University of California; Los Angeles California USA
| |
Collapse
|
13
|
Whicker JJ, Pinder JE, Ibrahim SA, Stone JM, Breshears DD, Baker KN. Uranium partition coefficients (Kd) in forest surface soil reveal long equilibrium times and vary by site and soil size fraction. HEALTH PHYSICS 2007; 93:36-46. [PMID: 17563491 DOI: 10.1097/01.hp.0000258924.55225.cd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The environmental mobility of newly deposited radionuclides in surface soil is driven by complex biogeochemical relationships, which have significant impacts on transport pathways. The partition coefficient (Kd) is useful for characterizing the soil-solution exchange kinetics and is an important factor for predicting relative amounts of a radionuclide transported to groundwater compared to that remaining on soil surfaces and thus available for transport through erosion processes. Measurements of Kd for 238U are particularly useful because of the extensive use of 238U in military applications and associated testing, such as done at Los Alamos National Laboratory (LANL). Site-specific measurements of Kd for 238U are needed because Kd is highly dependent on local soil conditions and also on the fine soil fraction because 238U concentrates onto smaller soil particles, such as clays and soil organic material, which are most susceptible to wind erosion and contribute to inhalation exposure in off-site populations. We measured Kd for uranium in soils from two neighboring semiarid forest sites at LANL using a U.S. Environmental Protection Agency (EPA)-based protocol for both whole soil and the fine soil fraction (diameters<45 microm). The 7-d Kd values, which are those specified in the EPA protocol, ranged from 276-508 mL g-1 for whole soil and from 615-2249 mL g-1 for the fine soil fraction. Unexpectedly, the 30-d Kd values, measured to test for soil-solution exchange equilibrium, were more than two times the 7-d values. Rates of adsorption of 238U to soil from solution were derived using a 2-component (FAST and SLOW) exponential model. We found significant differences in Kd values among LANL sampling sites, between whole and fine soils, and between 7-d and 30-d Kd measurements. The significant variation in soil-solution exchange kinetics among the soils and soil sizes promotes the use of site-specific data for estimates of environmental transport rates and suggests possible differences in desorption rates from soil to solution (e.g., into groundwater or lung fluid). We also explore potential relationships between wind erosion, soil characteristics, and Kd values. Combined, our results highlight the need for a better mechanistic understanding of soil-solution partitioning kinetics for accurate risk assessment.
Collapse
Affiliation(s)
- Jeffrey J Whicker
- Los Alamos National Laboratory, Radiation Protection Division, Mail Stop G761, Los Alamos, NM 87544, USA.
| | | | | | | | | | | |
Collapse
|
14
|
Whicker JJ, Pinder JE, Breshears DD, Eberhart CF. From dust to dose: Effects of forest disturbance on increased inhalation exposure. THE SCIENCE OF THE TOTAL ENVIRONMENT 2006; 368:519-30. [PMID: 16618498 DOI: 10.1016/j.scitotenv.2006.03.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2005] [Revised: 03/03/2006] [Accepted: 03/06/2006] [Indexed: 05/08/2023]
Abstract
Ecosystem disturbances that remove vegetation and disturb surface soils are major causes of excessive soil erosion and can result in accelerated transport of soils contaminated with hazardous materials. Accelerated wind erosion in disturbed lands that are contaminated is of particular concern because of potential increased inhalation exposure, yet measurements regarding these relationships are lacking. The importance of this was highlighted when, in May of 2000, the Cerro Grande fire burned over roughly 30% of Los Alamos National Laboratory (LANL), mostly in ponderosa pine (Pinus ponderosa) forest, and through areas with soils containing contaminants, particularly excess depleted and natural uranium. Additionally, post-fire thinning was performed in burned and unburned forests on about 25% of LANL land. The first goal of this study was to assess the potential for increased inhalation dose from uranium contaminated soils via wind-driven resuspension of soil following the Cerro Grande Fire and subsequent forest thinning. This was done through analysis of post-disturbance measurements of uranium air concentrations and their relationships with wind velocity and seasonal vegetation cover. We found a 14% average increase in uranium air concentrations at LANL perimeter locations after the fire, and the greatest air concentrations occurred during the months of April-June when wind velocities are highest, no snow cover, and low vegetation cover. The second goal was to develop a methodology to assess the relative contribution of each disturbance type towards increasing public and worker exposure to these resuspended soils. Measurements of wind-driven dust flux in severely burned, moderately burned, thinned, and unburned/unthinned forest areas were used to assess horizontal dust flux (HDF) in these areas. Using empirically derived relationships between measurements of HDF and respirible dust, coupled with onsite uranium soil concentrations, we estimate relative increases in inhalation doses for workers ranging from 15% to 38%. Despite the potential for increased doses resulting from these forest disturbances, the estimated annual dose rate for the public was <1 microSv yr(-1), which is far below the dose limits for public exposures, and the upper-bound dose rate for a LANL worker was estimated to be 140 microSv yr(-1), far below the 5 x 10(4) microSv yr(-1) occupational dose limit. These results show the importance of ecosystem disturbance in increasing mobility of soil-bound contaminants, which can ultimately increase exposure. However, it is important to investigate the magnitude of the increases when deciding appropriate strategies for management and long-term stewardship of contaminated lands.
Collapse
Affiliation(s)
- Jeffrey J Whicker
- Los Alamos National Laboratory, Health Physics Measurements Group, Mail Stop J573, Los Alamos NM 87545, USA.
| | | | | | | |
Collapse
|