Modeling the formation and growth of organic films on indoor surfaces

Emission, transport, and fate of semi‐volatile organic compounds (SVOCs), which include plasticizers, flame retardants, pesticides, biocides, and oxidation products of volatile organic compounds, are influenced in part by their tendency to sorb to indoor surfaces. A thin organic film enhances this effect, because it acts as both an SVOC sink and a source, thus potentially prolonging human exposure. Unfortunately, our ability to describe the initial formation and subsequent growth of organic films on indoor surfaces is limited. To overcome this gap, we propose a mass transfer model accounting for adsorption, condensation, and absorption of multiple gas‐phase SVOCs on impervious, vertical indoor surfaces. Further model development and experimental research are needed including more realistic scenarios accounting for surface heterogeneity, non‐ideal organic mixtures, and particle deposition.     

Measurements and modeling of absorptive partitioning of volatile organic compounds to painted surfaces

Partitioning to surfaces is an important sink for volatile organic compounds (VOCs) indoors, but the mechanisms are not well understood or quantified. Here, a mass spectrometer was coupled to a portable surface reactor and a flow tube to measure partitioning of VOCs into paint films coated onto glass or wallboard, and their subsequent diffusion. A model was developed to extract values of the effective absorbing organic mass concentration of the film, C_w, which is a measure of absorption capacity, and VOC diffusion coefficients, D_f, from VOC time profiles measured during film passivation and depassivation. Values of C_w agreed well with the value estimated from the paint film mass and flow tube air volume, and D_f values (also measured using attenuated total reflectance-Fourier transform infrared spectroscopy) correlated well with VOC vapor saturation concentrations, C*, estimated using a group contribution method. The value of these relationships for estimating key parameters that control VOC partitioning into paint and the fate of VOCs indoors was demonstrated using a house model, which indicated that >50% of VOCs with C* ≤10⁸ μg/m³ (C* of octane, hexanone, and propanol) that contacted a paint film of typical thickness fully permeated the film regardless of emission duration.     

Quantification of alkenes on indoor surfaces and implications for chemical sources and sinks

Indoor surfaces are known to support organic films, but their thickness, composition, and variability between environments remain poorly characterized. Alkenes are expected to be a significant component of these films, with the reaction with O₃ being a major sink for O₃ and source of airborne chemicals. Here, we present a sensitive, microscale, nanospectrophotometric method for quantifying the alkene (C=C bond) content of surface films and demonstrate its applicability in five studies relevant to indoor air chemistry. Collection efficiencies determined for a filter wipe method were ~64%, and the overall detection limit for monoalkenes was ~10 nmol m⁻². On average, painted walls and glass windows sampled across the University of Colorado Boulder campus were coated by ~4 nm thick films containing ~20% alkenes, and a simple calculation indicates that the lifetime for these alkenes due to reaction with O₃ is ~1 hour, indicating that the films are highly dynamic. Measurements of alkenes in films of skin oil, pan-fried cooking oils, a terpene-containing cleaner, and on various surfaces in a closed classroom overnight (where carboxyl groups were also measured) provided insight into the effects of chemical and physical processes on film and air composition.     

Growth of organic films on indoor surfaces

We present a model for the growth of organic films on impermeable indoor surfaces. The model couples transport through a gas‐side boundary layer adjacent to the surface with equilibrium partitioning of semivolatile organic compounds (SVOCs) between the gas phase and the surface film. Model predictions indicate that film growth would primarily be influenced by the gas‐phase concentration of SVOCs with octanol‐air partitioning (K_oa) values in the approximate range 10≤log K_oa≤13. Within the relevant range, SVOCs with lower values will equilibrate with the surface film more rapidly. Over time, the film becomes relatively enriched in species with higher log K_oa values, while the proportion of gas‐phase SVOCs not in equilibrium with the film decreases. Given stable airborne SVOC concentrations, films grow at faster rates initially and then subsequently diminish to an almost steady growth rate. Once an SVOC is equilibrated with the film, its mass per unit film volume remains constant, while its mass per unit area increases in proportion to overall film thickness. The predictions of the conceptual model and its mathematical embodiment are generally consistent with results reported in the peer‐reviewed literature.     

Heterogeneous oxidation of indoor surfaces by gas‐phase hydroxyl radicals

We investigate heterogeneous oxidation kinetics of monolayer‐thick, surface‐sorbed organics, namely di‐n‐octyl phthalate (DnOP) and palmitic acid (PA), with gas‐phase OH. The pseudo‐first order rate constants for organic loss at OH concentrations of 1.6 × 10⁸ molecules/cm³ are: (2.3 ± 0.1) × 10^?4 to (4.8 ± 0.8) × 10^?4 s^?1, and (1.3 ± 0.5) × 10^?4 s^?1 for DnOP and PA, respectively. Films developed in indoor office environments over a few weeks are also oxidized using the same OH concentration. Heterogeneous decay rate constants of mass signals from these films, attributed to phthalates (MW = 390.6) and to PA, are similar to those for the single‐component films, ie, (1.9 ± 0.4) × 10^?4 to (3.4 ± 0.5) × 10^?4 s^?1, and (1.1 ± 0.4) × 10^?4 s^?1, respectively. These results suggest that the lifetimes for OH heterogeneous oxidation of monolayer‐thick indoor organic films will be on the timescale of weeks to months. To support this argument, we present the first analysis of the mass transfer processes that occur when short‐lived gas‐phase molecules, such as OH, are taken up by reactive indoor surfaces. Due to rapid chemical production, the diffusion limitation to mass transfer is less important for short‐lived molecules than for molecules with little chemical production, such as ozone.     

Speciation (including adsorbed species) of copper, lead, nickel and zinc in the Meuse River: Observed results compared to values calculated with a chemical equilibrium computer program

The adsorption of trace metals on sediments of the Meuse River was interpreted in terms of competition between metals and protons for surface sites. Surface constants (^*β₁^surf) were determined for Cu, Zn and Cd (10^−1.8, 10^−3.6 and 10^−3.7). The constants for Pb, Ni, Ca and Mg (10^−1.7, 10^−3.8, 10^−6.5 and 10^−5.2) were estimated using a correlation between hydrolysis and surface constants. A chemical equilibrium computer program in which surface sites (for adsorption reactions) are treated as conventional ligands was used to calculate the speciation of Cu, Pb, Ni and Zn in the Meuse River. Calculated values of the adsorbed/dissolved distribution agreed well with observed values, after some realistic data manipulation. This work indicates that dissolved trace metal concentrations in the Meuse River are controlled by adsorption and not by precipitation mechanisms. The relationship between organic matter and suspended matter greatly influences the adsorption of metals like Cu and Pb.     

Electrocatalytic characterization and dye degradation of Nano-TiO2 electrode films fabricated by CVD

A 20-40 nm anatase-titania film on a titanium electrode was fabricated using chemical vapor deposition (CVD). The film was characterized using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The CVD deposition time and number of deposition coatings were evaluated to establish the appropriate film fabrication parameters. Results indicate that two coatings at a deposition time of 6 h each produced the best nano-TiO₂ electrode films (NTEFs) with an even distribution of ca. 20 nm diameter nanoparticles in the anatase lattice. The NTEF was tested as an electrocatalytic anode to investigate the degradation efficiency in treating methyl orange dye wastewater. A high removal efficiency of methyl orange dye and total organic carbon (TOC) of 97 and 56%, respectively; was achieved using a current density of 20 mA cm^− 2 for 160 min. Cyclic voltammetry showed that the electrochemical degradation reaction rate at the NTEF surface was predominately driven by molecular diffusion. The electrocatalytic decomposition rate of organic pollutants at the NTEF is controlled by mass transport, which was associated with the nanostructure of the electrocatalytic electrode.     

Impact of surface ozone interactions on indoor air chemistry: A modeling study

An INdoor air Detailed Chemical Model was developed to investigate the impact of ozone reactions with indoor surfaces (including occupants), on indoor air chemistry in simulated apartments subject to ambient air pollution. The results are consistent with experimental studies showing that approximately 80% of ozone indoors is lost through deposition to surfaces. The human body removes ozone most effectively from indoor air per square meter of surface, but the most significant surfaces for C₆‐C₁₀ aldehyde formation are soft furniture and painted walls owing to their large internal surfaces. Mixing ratios of between 8 and 11 ppb of C₆‐C₁₀ aldehydes are predicted to form in apartments in various locations in summer, the highest values are when ozone concentrations are enhanced outdoors. The most important aldehyde formed indoors is predicted to be nonanal (5‐7 ppb), driven by oxidation‐derived emissions from painted walls. In addition, ozone‐derived emissions from human skin were estimated for a small bedroom at nighttime with concentrations of nonanal, decanal, and 4‐oxopentanal predicted to be 0.5, 0.7, and 0.7 ppb, respectively. A detailed chemical analysis shows that ozone‐derived surface aldehyde emissions from materials and people change chemical processing indoors, through enhanced formation of nitrated organic compounds and decreased levels of oxidants.     

Indoor boundary layer chemistry modeling

Ozone (O₃) chemistry is thought to dominate the oxidation of indoor surfaces. We consider the hypothesis that reactions taking place within indoor boundary layers result in greater than anticipated hydroxyl radical (OH) deposition rates. We develop models that account for boundary layer mass‐transfer phenomena, O₃‐terpene chemistry and OH formation, removal, and deposition; we solve these analytically and by applying numerical methods. For an O₃‐limonene system, we find that OH flux to a surface with an O₃ reaction probability of 10^?8 is 4.3 × 10^?5 molec/(cm² s) which is about 10 times greater than predicted by a traditional boundary layer theory. At very low air exchange rates the OH surface flux can be as much as 10% of that for O₃. This effect becomes less pronounced for more O₃‐reactive surfaces. Turbulence intensity does not strongly influence the OH concentration gradient except for surfaces with an O₃ reaction probability >10^?4. Although the O₃ flux dominates OH flux under most conditions, OH flux can be responsible for as much as 10% of total oxidant uptake to otherwise low‐reactivity surfaces. Further, OH chemistry differs from that for ozone; therefore, its deposition is important in understanding the chemical evolution of some indoor surfaces and surface films.     

Manganese flux associated with dissolved and suspended manganese forms in Lake Fukami-ike

Redissolved, particulate and sedimentary managanese were studied in the anoxic hypolimnion of the small monomictic Lake Fukami-ike in central Japan. The amounts of particulate and dissolved manganese in the water column were observed. The release of dissolved managanese starts gradually beginning in March. DMn reaches especially high levels of 93 mgMn m⁻² d⁻¹ from the end of May to the end of June calculated from the gradient of a regression formula for the daily change in DMn. The rate of accumulated PMn is 0.64 mgMn m⁻² d⁻¹ from the end of July calculated from the gradient of a regression formula for the daily change in PMn.An accumulation of PMn and an associated decrease in dissolved organic carbon (DOC) were observed at the transition zone of oxic and anoxic layers. These facts seem to suggest that the DOC decrease involves the consumption of DOC as an electron donor by bacterial catalysis for the reduction of MnO₂. The upward and downward DOC fluxes, 0.320 mmolC m⁻² d⁻¹, were calculated by the mean gradient values of the upward and downward DOC concentrations. The mean DOC flux was calculated by both the mean gradient DOC and the vertical diffusion coefficient (0.0304 m⁻² d⁻¹). Manganese-reducing bacteria could contribute as much as 24% to the DOC decrease in the oxic and anoxic layers, considering bacterial assimilation efficiency (64%). Vertical diffusion Mn flux from the interstitial water to the hypolimnion is then assumed to be 2 mgMn m⁻² d⁻¹.Mn for the vertical eddy diffusion flux, the vertical diffusion flux from interstitial water of the bottom sediment, the sinking flux and microbiological Mn flux were obtained, and the biogeochemical managanese cycle in Lake Fukami-ike was calculated. DMn flux in the oxic and anoxic layers by manganese-reducing bacteria is 0.004 gMn m⁻² d⁻¹, a value corresponding to 10% of DMn flux.     

Indoor ozone/human chemistry and ventilation strategies

This study aimed to better understand and quantify the influence of ventilation strategies on occupant‐related indoor air chemistry. The oxidation of human skin oil constituents was studied in a continuously ventilated climate chamber at two air exchange rates (1 h^?1 and 3 h^?1) and two initial ozone mixing ratios (30 and 60 ppb). Additional measurements were performed to investigate the effect of intermittent ventilation (“off” followed by “on”). Soiled t‐shirts were used to simulate the presence of occupants. A time‐of‐flight‐chemical ionization mass spectrometer (ToF‐CIMS) in positive mode using protonated water clusters was used to measure the oxygenated reaction products geranyl acetone, 6‐methyl‐5‐hepten‐2‐one (6‐MHO) and 4‐oxopentanal (4‐OPA). The measurement data were used in a series of mass balance models accounting for formation and removal processes. Reactions of ozone with squalene occurring on the surface of the t‐shirts are mass transport limited; ventilation rate has only a small effect on this surface chemistry. Ozone‐squalene reactions on the t‐shirts produced gas‐phase geranyl acetone, which was subsequently removed almost equally by ventilation and further reaction with ozone. About 70% of gas‐phase 6‐MHO was produced in surface reactions on the t‐shirts, the remainder in secondary gas‐phase reactions of ozone with geranyl acetone. 6‐MHO was primarily removed by ventilation, while further reaction with ozone was responsible for about a third of its removal. 4‐OPA was formed primarily on the surfaces of the shirts (~60%); gas‐phase reactions of ozone with geranyl acetone and 6‐MHO accounted for ~30% and ~10%, respectively. 4‐OPA was removed entirely by ventilation. The results from the intermittent ventilation scenarios showed delayed formation of the reaction products and lower product concentrations compared to continuous ventilation.     

Removal of arsenite and arsenate ions from aqueous solution by basic yttrium carbonate

A new method has been developed to remove arsenite and arsenate ions from aquatic systems by using basic yttrium carbonate (BYC). Various parameters such as pH, anion concentration and reaction time were studied to establish optimum conditions. The removal by adsorption of arsenite and arsenate ions was found to be > 99% depending on initial concentration in the pH range of 9.8–10.5 and 7.5–9.0, respectively. The arsenate was also removed by precipitation at pH lower than 6.5 due to dissolution of BYC. The kinetic study shows that the adsorption follows the first order reaction. The adsorption isotherms of these anions were also studied at different temperatures. The equilibrium data fit well in the Langmuir model of adsorption. The Langmuir constants were calculated at different temperatures and the adsorption capacity for both anions increases with temperature. Anions such as Cl⁻, Br⁻, I⁻, NO⁻₃ and SO²⁻₄ have no interference in the removal process. The mechanism of the removal by adsorption was interpreted in terms of the surface charge and ligand orientation of BYC. The method was applied on synthetic wastewaters. Arsenite was oxidized to arsenate by 3% hydrogen peroxide. The yttrium was regenerated as basic yttrium carbonate.     

Lead in coastal sediments: The case of the elefsis gulf,Greece

Lead was determined in surface sediments and cores of a typical, polluted, almost enclosed Mediterranean embayment, the Gulf of Elefsis, near Athens. Total lead concentrations of 500–600 μg g⁻¹ were found in the surface sediments of the northeast section of the gulf, near major industries. However, a few kilometers from the source the concentrations decrease to ∼ 40m μg g⁻¹; the background pre-industrial levels are ∼ 10 μg g⁻¹ (in the < 61 μm fraction). Sequential extractions, consideration of the Pb/Al and Pb/Zn ratios, etc., indicate that the upper 5–15 cm of the sediment column are greatly enriched with lead of anthropogenic origin, which is mainly associated with fine particles. Redox reactions play an important role in the distribution and chemistry of lead, most of which (∼ 40%) is associated with organic matter and sulphides (extracted by EDTA); another ∼ 30% is associated with iron and manganese coatings and carbonates, with only a small but significant 3–4% of the total in a readily exchangeable form. The latter, under given conditions, may influence the lead concentrations in the overlying waters.     

Effect of NOM, turbidity and floc size on the PAC adsorption of MIB during alum coagulation

The effect of natural organic material (NOM) and turbidity on the powdered activated carbon (PAC) adsorption of the odour compound 2-methylisoborneol (MIB) was evaluated during alum coagulation. The character of the flocs, in terms of their size and fractal dimensions (Df), was used to interpret the observed adsorption behaviour of MIB during the coagulation process. As the alum dose was increased, the adsorption of MIB decreased. This was determined to be due to the size of the flocs, with larger flocs incorporating PAC into their structure, reducing the efficiency of mixing, and the bulk diffusion kinetics for the MIB molecule. The presence of turbidity also reduced MIB adsorption due to the formation of larger flocs. The character of NOM was found to have a greater influence on the adsorption of MIB than the floc structure.     

A comparative analysis of iron,manganese, silica,phosphorus, and sulfur in the hypolimnia of calcareous lakes

The chemistry of the hypolimnion was studied in late summer in 23 individual basins of 19 calcareous lakes situated in the Midwestern U.S.A. The basins represented a broad range in morphometry, and drainage basin influences. All but two of the basins were anoxic by early September.The concentrations of Fe were low in the anoxic basins because of precipitation of FeS. Excess sulfide accumulated in the hypolimnion (up to 7 mg 1⁻¹) making these basins sulfuretums. The concentrations of total-P ranged widely—from 0.03 mg 1⁻¹ in several seepage lakes to > 0.5 mg 1⁻¹ in drainage lakes with very short τ_w, or influenced by agricultural or urban drainage, or municipal waste. Neither apatite nor vivianite limited the hypolimnetic build-up of this key nutrient. Hypolimnetic Mn was almost entirely soluble if the basin was anoxic. The concentrations indirectly reflected external inputs, not the thermodynamics of rhodochrosite. Concentrations of dissolved silica were generally much lower than in inflowing waters. The hypolimnetic Si/P ratio was low unless the lake lacked surface inflows and also experienced high rates of groundwater inflow rich in silica and very low in P.Because of the very low hypolimnetic Fe/P and Fe/Si ratios, phosphate and silica are liberated from significant chemical interactions with Fe accompanying their eddy diffusion transport upward within the hypolimnion, and across the metalimnetic oxycline. Because of external P inputs and the efficiency of internal P recycling, Si is potentially a limiting nutrient for diatoms in calcareous lakes.     

Equilibrium and intra-particle diffusion of stabilized landfill leachate onto micro- and meso-porous activated carbon

Stabilized landfill leachate has previously been treated with activated carbon (AC); however, information on the selectivity of AC depending upon the pore size is minimal. Isotherm and kinetic experiments were conducted using three commercially available AC products, one micro-porous and two meso-porous. Equilibrium adsorption and intra-particle diffusion of organic matter from stabilized leachate was studied. Isotherm experimental data were fitted to Langmuir, Freundlich, and Redlich-Peterson isotherm models in non-linear forms. Of the three isotherm models, the Redlich-Peterson model provided the best fit to the experimental data and showed a similar organic matter adsorption capacity (approximately 0.2 g total organic carbon (TOC) g⁻¹ AC) for both micro-porous and meso-porous AC. The organic matter effective intra-particle diffusion coefficients (D_e) in both AC types were on the order of 10⁻¹⁰ m² s⁻¹ for AC particle sizes greater than 0.5 mm. Meso-porous ACs showed slightly higher D_e compared to micro-porous AC. Rapid small-scale tests showed a maximum of 80% TOC removal from leachate by each AC investigated. Fluorescence spectroscopy showed a preferential adsorption of fulvic-type organic matter with an increase in empty bed contact time by each AC.     

A Study of Human Reactions to Emissions from Building Materials in Climate Chambers. Part II: VOC Measurements,Mouse Bioassay,and Decipol Evaluation in the 1–2 mg/m3 TVOC Range

Monitoring of human reactions to the emission of formaldehyde and volatile organic compounds (VOC) from four commonly used building materials was carried out. The building materials were: a painted gypsum board, a rubber floor, a nylon carpet, and a particle board with an acid-curing paint. The exposures were performed in climate chambers. The air quality was quantified on the decipol scale by a trained panel, measurements of formaldehyde and VOC being performed simultaneously. The irritating potency of the materials was measured by a mouse bioassay. The VOC measurements showed several malodorants and irritants. Some abundant VOC identified in the head-space analyses were absent in the climate chamber air. The rubber floor and the nylon carpet exhibited a marked increase in decipols compatible with a number of odorous VOC identified in the air. A high formaldehyde concentration (minimum 743μg/m³) was measured for the particle board coated with an acid-curing paint. This was not reflected by a corresponding relatively high decipol value but a long-lasting irritating potency was observed in the mouse bioassay. TVOC sampled on Tenax and expressed in mass per volume as well as in molar concentration, and decipol evaluation both have limitations and should be used with caution as indicators of (perceived) indoor air quality. Eye irritation expressed by means of the eye index reflecting the tear film quality index (comprised of break-up time, foam formation, thickness of the precorneal lipid layer of the tear film, and epithelial damage) was found to be insensitive to formaldehyde and a VOC mixture but sensitive to TVOC concentrations of 1–2 mg/m³. Lipophilic VOC may be the cause of reduced tear film quality by destabilization of the lipid multilayer of the tear film.     

Croissance bacterienne sur charbon actif granule. Investigation au microscope electronique a balayage

Recent work characterising biological development in granular activated carbon filters (GAC) has contributed to a better understanding of the role of bacterial growth in the efficiency of adsorption processes in water treatment. Among the techniques involved in biological GAC studies, scanning electron microscopy (SEM) can be used to describe the physical relations between bacterial populations and activated carbon surface. In this study, an effective technique is presented for two-phased fixation (2% paraformaldehyde-2.5% glutaraldehyde and 1% osmium tetroxyde), dehydration and critical point drying of “biological” activated carbon particles. Microscopic examination of GAC after 5 days of filtration (drinking water artificially contaminated with 1,0 mg l⁻¹ of an anionic surfactant) showed the nature of the fixation sites of organic matter and the initially scattered bacterial growth sites. The microbiological colonization appears then along surface crevices and holes (Fig. 1) where substrate concentration occurs and where organisms are shielded from fluid shear forces. Bacteria attach to the carbon surface by secreting a network-like polysaccharide matrix (Fig. 2). After 15 days of filtration (Fig. 3), biological maturation of the carbon induces the progressive formation of a membranous organic film (surfactant precipitation and bioflocculation) making it difficult to observe bacterial development on the carbon surface (Fig. 4). However, there is no evidence that a continuous biofilm (uniform layer of bacteria in a slimy shell) develops around the carbon granules. The observations support the assumption that structural relationships between microorganisms and carbon surface are modified considerably during the accumulation of organic floc and cellular debris. This organic support medium enhances the biodegradation of substrates that would obtained from the carbon surface alone. Therefore, it appears that the effective metabolization of organic adsorbates in GAC filtration units is only slightly connected with the efficiency of physico-chemical adsorption processes.     

Effects of hardness and alkalinity on the removal of arsenic(V) from humic acid-deficient and humic acid-rich groundwater by zero-valent iron

The effects of hardness (Ca²⁺) and alkalinity (HCO₃⁻) on arsenic(V) removal from humic acid (HA)-deficient and HA-rich groundwater by zero-valent iron (Fe⁰) were investigated using batch experiments. Arsenic, in general, is removed from groundwater possibly by adsorption and co-precipitation with the iron corrosion products. However, in the co-presence of HCO₃⁻ and Ca²⁺, the removal rate of arsenic increased with increasing concentrations of either Ca²⁺ or HCO₃⁻. It was observed that the removal of arsenic was significantly enhanced by the formation of CaCO₃ as a nucleation seed for the growth of large iron (hydr)oxide particles. In the co-existence of Ca²⁺, HCO₃⁻ and HA, the presence of HA diminished the positive role of Ca²⁺ due to the formation of Fe-humate complexes in solution and delaying of the formation of CaCO₃. As a result, the formation of the large iron (hydr)oxide particles was inhibited in the earlier stage which, in turn, affected the removal of arsenic. However, after the formation of CaCO₃ and the subsequent growth of such particles, the presence of large iron (hydr)oxide particles resulted in the rapid removing of arsenic and Fe-humate by adsorption and/or co-precipitation.     

Seasonal,behavioral and growth changes of juvenile Corbicula fluminea exposed to chrysotile asbestos

Juvenile Corbicula fluminea (5.2–8.6 mm shell length) were collected in winter (8–12°C) and summer (17–23°C) conditions and tested for responses to chrysotile asbestos at concentrations of 0–10⁸ fibers l⁻¹ for 30 days. Growth, siphoning activity, fiber uptake and gill tissue ultrastructure were evaluated. Siphoning activity was significantly reduced by 30 days of exposure at 10²–10⁸ fibers l⁻¹ in summer and winter compared to controls and was paralleled by significant reductions in shell growth at 10⁴–10⁸ fibers l⁻¹ in summer and 10⁵–10⁸ fibers l⁻¹ in winter. Differences in shell:tissue growth were apparent with lower values in all groups in the winter compared to their counterparts in the summer due to energy allocations to tissue growth in the winter. Therefore, Corbicula were more susceptible to asbestos in winter conditions due to differences between robust, summer vs inherently weakened winter collected clams. Clams exposed to 10⁸ fibers l⁻¹ accumulated ∼150 fibers mg⁻¹ in gill and 110 fibers mg⁻¹ in viscera after 30 days in both seasons. The presence of asbestos in tissue was consistent with significantly greater water content and total gill locule surface area in 10⁸ fibers l⁻¹ exposed clams relative to controls. Small asbestos fibers were preferentially accumulated in gill and visceral tissues. Corbicula may become a useful biomonitor for asbestos contamination in the United States and abroad due to its ability to accumulate asbestos fibers efficiently.