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Title: Plant Uptake of Organic Pollutants from Soil: A Critical Review ofBioconcentration Estimates Based on Modelsand Experiments

Abstract

The role of terrestrial vegetation in transferring chemicals from soil and air into specific plant tissues (stems, leaves, roots, etc.) is still not well characterized. We provide here a critical review of plant-to-soil bioconcentration ratio (BCR) estimates based on models and experimental data. This review includes the conceptual and theoretical formulations of the bioconcentration ratio, constructing and calibrating empirical and mathematical algorithms to describe this ratio and the experimental data used to quantify BCRs and calibrate the model performance. We first evaluate the theoretical basis for the BCR concept and BCR models and consider how lack of knowledge and data limits reliability and consistency of BCR estimates. We next consider alternate modeling strategies for BCR. A key focus of this evaluation is the relative contributions to overall uncertainty from model uncertainty versus variability in the experimental data used to develop and test the models. As a case study, we consider a single chemical, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and focus on variability of bioconcentration measurements obtained from 81 experiments with different plant species, different plant tissues, different experimental conditions, and different methods for reporting concentrations in the soil and plant tissues. We use these observations to evaluate both the magnitude of experimental variabilitymore » in plant bioconcentration and compare this to model uncertainty. Among these 81 measurements, the variation of the plant/soil BCR has a geometric standard deviation (GSD) of 3.5 and a coefficient of variability (CV-ratio of arithmetic standard deviation to mean) of 1.7. These variations are significant but low relative to model uncertainties--which have an estimated GSD of 10 with a corresponding CV of 14.« less

Authors:
;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director, Office of Science; Environmental ProtectionAgency
OSTI Identifier:
927246
Report Number(s):
LBNL-60273
Journal ID: ISSN 0730-7268; ETOCDK; R&D Project: E12301; BnR: 400408000; TRN: US200811%%68
DOE Contract Number:
DE-AC02-05CH11231; DW-988-38190-01-01
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Toxicology and Chemistry; Journal Volume: 0; Journal Issue: 0; Related Information: Journal Publication Date: 07/30/2007
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AIR; ALGORITHMS; EVALUATION; PERFORMANCE; PLANT TISSUES; PLANTS; POLLUTANTS; RELIABILITY; SIMULATION; SOILS

Citation Formats

McKone, Thomas E., and Maddalena, Randy L. Plant Uptake of Organic Pollutants from Soil: A Critical Review ofBioconcentration Estimates Based on Modelsand Experiments. United States: N. p., 2007. Web. doi:10.1897/06-269.
McKone, Thomas E., & Maddalena, Randy L. Plant Uptake of Organic Pollutants from Soil: A Critical Review ofBioconcentration Estimates Based on Modelsand Experiments. United States. doi:10.1897/06-269.
McKone, Thomas E., and Maddalena, Randy L. Mon . "Plant Uptake of Organic Pollutants from Soil: A Critical Review ofBioconcentration Estimates Based on Modelsand Experiments". United States. doi:10.1897/06-269. https://www.osti.gov/servlets/purl/927246.
@article{osti_927246,
title = {Plant Uptake of Organic Pollutants from Soil: A Critical Review ofBioconcentration Estimates Based on Modelsand Experiments},
author = {McKone, Thomas E. and Maddalena, Randy L.},
abstractNote = {The role of terrestrial vegetation in transferring chemicals from soil and air into specific plant tissues (stems, leaves, roots, etc.) is still not well characterized. We provide here a critical review of plant-to-soil bioconcentration ratio (BCR) estimates based on models and experimental data. This review includes the conceptual and theoretical formulations of the bioconcentration ratio, constructing and calibrating empirical and mathematical algorithms to describe this ratio and the experimental data used to quantify BCRs and calibrate the model performance. We first evaluate the theoretical basis for the BCR concept and BCR models and consider how lack of knowledge and data limits reliability and consistency of BCR estimates. We next consider alternate modeling strategies for BCR. A key focus of this evaluation is the relative contributions to overall uncertainty from model uncertainty versus variability in the experimental data used to develop and test the models. As a case study, we consider a single chemical, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and focus on variability of bioconcentration measurements obtained from 81 experiments with different plant species, different plant tissues, different experimental conditions, and different methods for reporting concentrations in the soil and plant tissues. We use these observations to evaluate both the magnitude of experimental variability in plant bioconcentration and compare this to model uncertainty. Among these 81 measurements, the variation of the plant/soil BCR has a geometric standard deviation (GSD) of 3.5 and a coefficient of variability (CV-ratio of arithmetic standard deviation to mean) of 1.7. These variations are significant but low relative to model uncertainties--which have an estimated GSD of 10 with a corresponding CV of 14.},
doi = {10.1897/06-269},
journal = {Environmental Toxicology and Chemistry},
number = 0,
volume = 0,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • A bioconcentration ratio (BCR) represents the ratio of the concentration of a chemical found in an exposed biological system, such as a plant or fish, to the concentration in the exposure medium (water, soil, or air). A comparison is made of the precision and accuracy of the molecular connectivity index (MCI) and the octanol/water partition coefficient (K{sub ow}) as predictors of BCRs from the soil matrix into above- or below-ground vegetation tissues. Calculated octanol/air partition coefficient (K{sub oa}) values are compared with calculated K{sub ow} and MCI values as predictors of measured air-to-plant BCRs. Based on a statistical evaluation ofmore » explained variance, residual error, and cross-validation, this evaluation reveals that the MCI provides higher precision, greater ease of use, and a more cost-effective method for predicting the potential bioconcentration of a chemical from soil into above-ground vegetation. Statistical analyses of the various methods reveal that both the K{sub ow} and MCI approaches have a similar level of precision for predicting BCRs from soil solution into roots and, among MCI, K{sub oa} and K{sub ow}; K{sub oa} is somewhat more precise and valid than MCI and K{sub ow} for estimating uptake, but all have limited accuracy as bioconcentration predictors. These latter results are derived mainly from the paucity of both reliable K{sub oa} values and measured air-to-plant BCRs and indicate a need for more experimental measurements from which more accurate models may be developed.« less
  • Post-Chernobyl experience has demonstrated that persistently high plant transfer of {sup 137}Cs occurs from organic soils in upland and seminatural ecosystems. The soil properties influencing this transfer have been known for some time but have not been quantified. A pot experiment was conducted using 23 soils collected from selected areas of Great Britain, which were spiked with {sup 134}Cs, and Agrostis capillaris grown for 19--45 days. The plant-to-soil {sup 134}Cs concentration ratio (CR) varied from 0.06 to 44; log CR positively correlated to soil organic matter content (R{sup 2} = 0.84), and CR values were highest for soils with lowmore » distribution coefficients (K{sub d}) of {sup 134}Cs. Soils with high organic matter contents and high concentrations of NH{sub 4}{sup +} in solution showed high {sup 134}Cs mobility (low K{sub d}). The plant-to-soil solution {sup 134}Cs ratio decreased sharply with increasing soil solution K{sup +}. A two parameter linear model, used to predict log CR from soil solution K{sup +} and K{sub d}, explained 94% of the variability in CR values. In conclusion, the high transfer of {sup 134}Cs in organic soils is related to both the high {sup 134}Cs mobility (low clay content and high NH{sub 4}{sup +} concentrations) and low K availability.« less
  • Contamination of water and soil that might eventually contact human skin makes it imperative to include the dermal uptake route in efforts to assess potential environmental health risks. Direct measurements of dermal uptake from either water or soil are only available for a small number of the thousands of chemicals likely to be found in the environment. We propose here a mass-transfer model for estimating skin permeability and dermal uptake for organic chemicals that contaminate soil and water. Statistical relationships between measured permeabilities and chemical properties reveal that permeability varies primarily with the octanol-water partition coefficient (K[sub ow]) and secondarilymore » with the molecular weight. From these results, we derive a fugacity-based model for skin permeability that addresses the inherent permeability of the skin, the interaction of the skin with the environmental medium on skin (water or soil), and retains a relatively simple algebraic form. Model predictions are compared to measured human skin permeabilities for some 50 compounds in water and four compounds in soil. The model is adjusted to account for dermal uptake during both short-term (10-20 min) and long-term (several hour) exposures. This model is recommended for compounds with molecular weight less than or equal to 280 g.« less
  • The effects of several soil factors on cadmium (Cd) accumulation by plants were determined. Cadmium concentration in oat shoots (Avena sativa L.) was decreased by increasing the cation exchange capacity (CEC) of the soil. Except for its CEC effect, organic matter did not influence the concentration of Cd in oat shoots. The results indicate that the retaining power of organic matter for Cd is predominately through its CEC property rather than chelating ability. Cadmium concentration of soybean shoots (Glycine max L.) increased soil temperature. In the presence of 10 ppm of soil-applied Cd, the addition of Zn from the 5more » to 50 ppm range, apart from raising the Zn concentration, significantly increased the Cd concentration of soybean shoots. The increased Cd concentration was primarily due to decreased plant growth. A depression in Cd concentration of soybean shoots, relative to control, began to occur at the 100 ppm Zn level. 12 references, 5 tables.« less
  • The authors model sounding rocket gas release experiments in the ionosphere, to study the apparant lack of observation of critical ionization velocity phenomena in space plasmas. Laboratory evidence has been seen for the occurance of critical ionization velocity effects. Their simulations indicate that in space plasmas it is necessary to have some type of a seed ionization process to initiate the process, and mechanisms such as charge exchange are too slow to accomplish this.