Bioconcentration of superlipophilic persistent chemicals

According to present understanding, persistent superlipophilic chemicals — such as octachlorodibenzo-p-dioxin, octachlorodibenzofuran, Mirex etc — with log K_ow > 6 and cross sections > 9.5 Å, bioconcentrate in aquatic organisms only little from ambient water. The most convincing argument against it is that in bioconcentration experiments with superlipophilic chemicals amounts applied exceeded water solubility by several orders of magnitude. This paper describes various methods for determining bioconcentration factors (BCF) of superlipophilic compounds. As exemplified with octachlorodibenzo-p-dioxin, BCF values evaluated by these methods match well with those calculated by QSARs for fish and mussels based on log K_ow and water solubility. As expected, these BCF values exceed previous values by several orders of magnitude. For BCF evaluation of superlipophilic chemicals in aquatic organisms we recommend:

1. flow-through systems, kinetic method (OECD guideline No. 305 E)
2. ambient concentrations < water solubility
3. during the uptake and especially during the elimination phase no toxic effects of the test organisms should occur.

     

Prediction of bioconcentration factors under non-equilibrium conditions

With the bioconcentration of lipophilic compounds by aquatic organisms when equilibrium between water and biota is attained, the logarithm of the bioconcentration factor has a direct linear relationship with the logarithm of the octanol/water partition coefficient. In practice, however, equilibrium may not be reached, particularly for more lipophilic compounds. It is shown theoretically, and confirmed by use of published experimental results on fish, that a different direct linear relationship also exists between the logarithms of the bioconcentration factor and the partition coefficient for compounds not achieving equilibrium after a specific exposure time. Thus, non-equilibrium bioconcentration factors can be predicted from their partition coefficients. The constants in the non-equilibrium linear equation are related to those from the relationships between equilibrium bioconcentration factors and the partition coefficients, and between the first-order clearance rate constants and the partition coefficients.     

Bioaccumulation and uptake routes of perfluoroalkyl acids in Daphnia magna

Perfluoroalkyl acids (PFAs), one kind of emerging contaminants, have attracted great attentions in recent years. However, the study about their bioaccumulation mechanism remains scarce. In this research, the bioaccumulation of six kinds of PFAs in water flea Daphnia magna was studied. The uptake rates of PFAs in D. magna ranged from 178 to 1338 L kg^?1 d^?1, and they increased with increasing perfluoroalkyl chain length; the elimination rates ranged from 0.98 to 2.82 d^?1. The bioaccumulation factors (BAFs) of PFAs ranged from 91 to 380 L kg^?1 in wet weight after 25 d exposure; they increased with increasing perfluoroalkyl chain length and had a significant positive correlation with the n-octanol/water partition coefficients (log K_ow) of PFAs (p < 0.05). This indicated that the hydrophobicity of PFAs plays an important role in their bioaccumulation. The BAFs almost kept constant when the PFA concentrations in aqueous phase increased from 1 to 10 μg L^?1. Scenedesmus subspicatus, as the food of D. magna, did not significantly affect the bioaccumulation of PFAs by D. magna. Furthermore, the body burden of PFAs in the dead D. magna was 1.08–2.52 times higher than that in the living ones, inferring that the body surface sorption is a main uptake route of PFAs in D. magna. This study suggested that the bioaccumulation of PFAs in D. magna is mainly controlled by their partition between organisms and water; further research should be conducted to study the intrinsic mechanisms, especially the roles of protein and lipid in organisms.     

Partitioning behaviour of perfluorinated alkyl contaminants between water, sediment and fish in the Orge River (nearby Paris, France)

This paper reports on the partitioning behaviour of 15 perfluorinated compounds (PFCs), including C₄-C₁₀ sulfonates and C₅-C₁₄ carboxylic acids, between water, sediment and fish (European chub, Leuciscus cephalus) in the Orge River (nearby Paris). Total PFC levels were 73.0 ± 3.0 ng L⁻¹ in water and 8.4 ± 0.5 ng g⁻¹ in sediment. They were in the range 43.1-4997.2 ng g⁻¹ in fish, in which PFC tissue distribution followed the order plasma > liver > gills > gonads > muscle. Sediment-water distribution coefficients (log K_d) and bioaccumulation factors (log BAF) were in the range 0.8-4.3 and 0.9-6.7, respectively. Both distribution coefficients positively correlated with perfluoroalkyl chain length. Field-based biota-sediment accumulation factors (BSAFs) are also reported, for the first time for PFCs other than perfluorooctane sulfonate. log BSAF ranged between −1.3 and 1.5 and was negatively correlated with the perfluoroalkyl chain length in the case of carboxylic acids.     

Prediction of ecotoxicological behaviour of chemicals: Relationship between n-octanol/water partition coefficient and bioaccumulation of organic chemicals by alga Chlorella

The bioaccumulation potential of organic chemicals by the green alga $\text{Chlorella fusca}$ was determined. A quantitative relationship was found to exist between the lipophilicity (n-octanol/water partition coefficient) of the chemicals and the bioaccumulation factor.     

Partitioning of perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (PFOSA) between water and sediment

Laboratory partitioning experiments were conducted to elucidate the sorption behaviour and partitioning of perfluoroalkyl compounds (PFCs). Three different sediment types were used and separately spiked with perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS) and perfluorooctane sulfonamide (PFOSA) at low environmentally realistic concentrations. PFOA, PFOS and PFOSA were mainly distributed in the dissolved phase at low suspended solid concentrations, indicating their long-range transport potential in the marine environment. In all cases, the equilibrium isotherms were linear and the organic carbon normalised partition coefficients (K_OC) decreased in the following order: PFOSA (log K_OC = 4.1 ± 0.35 cm³ g⁻¹) > PFOS (3.7 ± 0.56 cm³ g⁻¹) > PFOA (2.4 ± 0.12 cm³ g⁻¹). The level of organic content had a significant influence on the partitioning. For the sediment with negligible organic content the density of the sediment became the most important factor influencing the partitioning. Ultimately, data on the partitioning of PFCs between aqueous media and suspended solids are essential for modelling their transport and environmental fate.     

Biosorption of hydrophobic organic pollutants by mixed microbial populations

In recognition of the need to estimate biosorption for natural microbial populations, the variability of partition coefficients for two hydrophobic pollutants to natural populations from a variety of aquatic systems was investigated. Biosorption partition coefficents for pyrene [2.46(±0.6) × 10⁴] and phenanthrene [6.34(±1) × 10³] were nearly constant over 14 different microbial sources, consisting of sediments and soils from eight states. For these condensed ring aromatics, semi-empirical equations were developed relating biosorption partition coefficients to octanol/water partition coefficients and to water solubility and melting point. Concepts and relationships developed for these materials should extend to other families of hydrophobic compounds.     

Influence of temperature on formaldehyde emission parameters of dry building materials

The diffusion coefficient, D, partition coefficient, K, and the initial volatile organic compounds (VOCs) in dry building materials, are the three key parameters used to predict the VOC emissions. D and K may be strongly affected by temperature. We have developed a new and simple method, the C-history method, to measure the diffusion coefficient, D and the partition coefficient, K of formaldehyde in dry building materials at temperatures of 18, 30, 40 and 50 °C. The measured variations of the diffusion coefficients and the partition coefficients with temperature for particle board, vinyl floor, medium- and high-density board are presented. A formula relating the partition coefficient and related factors is obtained through analysis. This formula can predict the partition coefficient in principle and provide an insight for fitting experimental data, and it agrees well with the experimental results.     

Adsorption,desorption, soil mobility,aqueous persistence and octanol‐water partitioning coefficients of terbufos,terbufos sulfoxide and terbufos sulfone

Abstract

Terbufos, t. sulfoxide and t. sulfone (5 μg ml^‐1) were incubated in natural, sterilized natural and distilled water, with initial pH values of 8.8, 8.8 and 6.0, respectively, at 20°C. First‐order disappearance was observed for the three compounds. Rates in natural and sterilized water were similar indicating chemical degradation predominated. Terbufos disappeared rapidly (t½>=3 days) in all systems. T. sulfoxide and t. sulfone were more persistent in the natural (t½>=18–40 days) and distilled water (t½>=280–350 days). Adsorption data for the three compounds in four soil‐water systems showed the decreasing order of adsorption to be terbufos>>t. sulfoxide=t. sulfone. Desorption from soils fortified at 5 μg g^‐1 with water was examined for 4 successive 18‐hr cycles. T. sulfoxide and t. sulfone were totally desorbed; terbufos was too unstable to study. The mobility of the compound in soil eluted with water was in the order, t. sulfoxide=t. sulfone>> terbufos, in agreement with adsorption‐desorption results. The octanol‐water partitioning coefficients for terbufos, t. sulfoxide and t. sulfone, at 23°C, were 3:30 x 10 , 164, and 302, respectively.     

Copper kinetics and internal distribution in the marbled crayfish (Procambarus sp.)

Metal pollution e.g. copper, in water bodies occurs worldwide. Although copper is an essential trace metal, at certain levels it is still considered as pollutant. The aim of this study was to investigate the effect of exposure concentration on copper bioaccumulation in marbled crayfish (Procambarus sp.) by determining uptake and elimination kinetics. Crayfish were exposed to sub-lethal copper concentrations (average measured concentrations of 0.031 and 0.38 mg Cu L⁻¹) for 14 d and transferred to copper-free water for another 14 d. At different time points during the uptake and elimination phases copper concentrations were measured in five organs (exoskeleton, gills, muscle, ovaries and hepatopancreas). At 0.031 mg Cu L⁻¹, copper levels in the crayfish organs were not significantly increased compared to the control animals, suggesting effective regulation. Exposure to 0.38 mg Cu L⁻¹ did lead to not significantly increased copper levels in muscles and ovaries, while the gills and exoskeleton, which are in direct contact with the water, showed significantly higher copper concentrations. In these four organs, copper showed fast uptake kinetics with equilibrium reached within 10 d of exposure. Copper accumulation was highest in the hepatopancreas; uptake in this storage organ steadily increased with time and did not reach equilibrium within the 14-d exposure period. Copper accumulation levels in the marbled crayfish found in this study were hepatopancreas > gills > exoskeleton > muscle.     

The rate and mechanism of the gas-phase oxidation of hydroxyacetone

The rate and mechanism for gas-phase destruction of hydroxyacetone, CH₃C(O)CH₂OH, by reaction with OH, Cl-atoms, and by photolysis have been determined. The first quantitative UV absorption spectrum of hydroxyacetone is reported over the wavelength range 235 to 340 nm; the spectrum is blue-shifted by about 15 nm relative to that of acetone and peaks at 266 nm, with a maximum absorption cross section of (6.7±0.6) ×10^-20 cm² molecule^-1. Measurable absorption extends out to about 330 nm. The quantum yield for photolysis of hydroxyacetone in the region relevant to the troposphere (λ>290 nm) was found to be significantly less than unity. Rate coefficients for the reaction of hydroxyacetone with OH radicals and Cl-atoms were determined at 298 K using the relative rate technique. The rate coefficient for reaction with OH was found to be (3.0±0.7)×10^-12 cm³ molecule^-1 s^-1, while the rate coefficient for reaction with Cl-atoms was found to be (5.6±0.7)×10^-11 cm³ molecule^-1 s^-1. Both values agree well with previous studies. The data were used to determine the lifetime of hydroxyacetone in the troposphere. Reaction with OH is the major gas-phase destruction mechanism for this compound, limiting its lifetime to about 4 days, while photolysis is found to be only of minor importance.     

A rapidly equilibrating, thin film, passive water sampler for organic contaminants; characterization and field testing

Improving methods for assessing the spatial and temporal resolution of organic compound concentrations in marine environments is important to the sustainable management of our coastal systems. Here we evaluate the use of ethylene vinyl acetate (EVA) as a candidate polymer for thin-film passive sampling in waters of marine environments. Log K_EVA−W partition coefficients correlate well (r² = 0.87) with Log K_OW values for selected pesticides and polychlorinated biphenyls (PCBs) where Log K_EVA−W = 1.04 Log K_OW + 0.22. EVA is a suitable polymer for passive sampling due to both its high affinity for organic compounds and its ease of coating at sub-micron film thicknesses on various substrates. Twelve-day field deployments were effective in detecting target compounds with good precision making EVA a potential multi-media fugacity meter.     

Distribution, speciation and availability of antimony (Sb) in soils and terrestrial plants from an active Sb mining area

Here, we present one of the first studies investigating the mobility, solubility and the speciation-dependent in-situ bioaccumulation of antimony (Sb) in an active Sb mining area (Xikuangshan, China). Total Sb concentrations in soils are high (527-11,798 mg kg⁻¹), and all soils, including those taken from a paddy field and a vegetable garden, show a high bioavailable Sb fraction (6.3-748 mg kg⁻¹), dominated by Sb(V). Elevated concentrations in native plant species (109-4029 mg kg⁻¹) underpin this. Both chemical equilibrium studies and XANES data suggest the presence of Ca[Sb(OH)₆]₂, controlling Sb solubility. A very close relationship was found between the citric acid extractable Sb in plants and water or sulfate extractable Sb in soil, indicating that citric acid extractable Sb content in plants may be a better predictor for bioavailable Sb in soil than total acid digestible Sb plant content.     

SVOC partitioning between the gas phase and settled dust indoors

Semivolatile organic compounds (SVOCs) are a major class of indoor pollutants. Understanding SVOC partitioning between the gas phase and settled dust is important for characterizing the fate of these species indoors and the pathways by which humans are exposed to them. Such knowledge also helps in crafting measurement programs for epidemiological studies designed to probe potential associations between exposure to these compounds and adverse health effects. In this paper, we analyze published data from nineteen studies that cumulatively report measurements of dustborne and airborne SVOCs in more than a thousand buildings, mostly residences, in seven countries. In aggregate, measured median data are reported in these studies for 66 different SVOCs whose octanol-air partition coefficients (K_oa) span more than five orders of magnitude. We use these data to test a simple equilibrium model for estimating the partitioning of an SVOC between the gas phase and settled dust indoors. The results demonstrate, in central tendency, that a compound’s octanol-air partition coefficient is a strong predictor of its abundance in settled dust relative to its gas phase concentration. Using median measured results for each SVOC in each study, dustborne mass fractions predicted using K_oa and gas-phase concentrations correlate reasonably well with measured dustborne mass fractions (R² = 0.76). Combined with theoretical understanding of SVOC partitioning kinetics, the empirical evidence also suggests that for SVOCs with high K_oa values, the mass fraction in settled dust may not have sufficient time to equilibrate with the gas phase concentration.     

Combined effects of titanium dioxide and humic acid on the bioaccumulation of cadmium in Zebrafish

The combined effects of titanium dioxide (TiO₂) nanoparticles and humic acid (HA) on the bioaccumulation of cadmium (Cd) in Zebrafish were investigated. Experimental data on the equilibrium Cd bioaccumulation suggest that only the dissolved Cd effectively contributed to Cd bioaccumulation in HA solutions whereas both the dissolved and TiO₂ associated Cd were accumulated in TiO₂ or the mixture of HA and TiO₂ solutions, due likely to the additional intestine uptake of the TiO₂-bound Cd. The equilibrium Cd bioaccumulation in the mixed system was comparable to that in the corresponding HA solutions, and significantly lower than that in the corresponding TiO₂ solutions (n = 3, p < 0.05). The presence of either HA or TiO₂ (5-20 mg L⁻¹) in water slightly increased the uptake rate constants of Cd bioaccumulation whereas combining HA and TiO₂ reduced the uptake rate constants.     

FT-IR kinetic and product study of the Br-radical initiated oxidation of α, β-unsaturated organic carbonyl compounds

Using the relative kinetic technique the kinetics of the gas-phase reactions of Br radicals with acrolein, methacrolein and methylvinyl ketone have been investigated at (301±3) K in 1013 mbar of (N₂+O₂) bath gas at varying proportions. In 1013 mbar of synthetic air the following rate coefficients have been obtained (in units of cm³ molecule⁻¹ s⁻¹): acrolein (3.21±0.11)×10⁻¹²; methacrolein (2.33±0.08)×10⁻¹¹; methyl vinyl ketone (1.87±0.06)×10⁻¹¹. This study represents the first determination of the rate coefficients for these compounds. As for other unsaturated hydrocarbons the rate coefficient with Br was found to increase with increasing partial pressure of O₂. From the product studies of the reactions it has been established that addition of Br radicals to the terminal C-atom is the major pathway in all three cases. However, for acrolein H atom abstraction from the -CO–H group is also significant. Mechanisms are proposed to explain the observed products, mainly β-brominated carbonyl compounds.     

Source profile and health risk assessment of PM2.5 from coal-fired power plants in Fuxin,China

In order to improve and establish the localized source profile of PM_2.5 in Fuxin, the ashes under dust catcher were collected from four typical coal-fired power plants in Fuxin and twenty-eight components were measured. The source profile of PM_2.5 in the soot of the four coal-fired power plants was established. SO₄^2? was the most abundant component in the PM_2.5 of the soot of the four coal-fired power plants, followed by Ca²⁺ and organic carbon (OC). The content of element components in PM_2.5 smoke ranges from 5.06 to 10.97%, the content of ionic components ranges from 36.53 to 48.59%, and the total carbon content ranges from 9.43 to 11.36%. The divergence coefficient of PM_2.5 source profile in Fuxin coal burning smoke is mostly similar to that of Fushun, whereas the divergence coefficient of Colorado reaches 0.65, indicating that Fuxin coal burning power plant smoke has no similarity to Colorado. The order of the geological accumulation index of Ni, Cu, V, Mn, and Cr was Cr (4.58) > Mn (4.42) > V (4.38) > Cu (4.09) > Ni (4.06), showing a heavy pollution level. The health risk assessment model recommended by the USEPA was used to assess the health risk of heavy metals in soot of coal-fired power plants, and the non-carcinogenic risk values of As for children and adults were 45.7 and 4.90, respectively. The carcinogenic risk values of Cr for adults and children were the highest, with values of 3.66 × 10^?5 and 2.06 × 10^?5, respectively, followed by As.

     

Polybrominated diphenyl ethers and organochlorine compound levels in brown trout (Salmo trutta) from Andean Patagonia, Argentina

Polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), DDTs and endosulfan residues were analyzed in muscle, liver, gonads, gills and stomach content of brown trout (Salmo trutta) from the Andean Patagonia. PBDEs, PCBs and DDTs levels were positively correlated with lipid content, while less hydrophobic endosulfans showed a poor correlation. Endosulfan levels were about 99.9% of total contaminant (highest levels in liver 500 × 10³ ng g⁻¹ lipid weight), with α-/β-isomers ratio >1 in all organs. These results are in agreement to the current-use of the technical endosulfan and also suggest acute exposure to this insecticide. Conversely, DDT/DDE ratio reflects fish exposure to old DDT sources, showing a DDE predominance. Gills had the highest levels of DDTs, PCBs and PBDEs, indicating they represent the main uptake pathway for such hydrophobic compounds from water column. PCBs showed the lowest levels in all organs and the PBDEs/PCBs ratios >1 agree with worldwide trends. PBDEs levels in gonads, gills, liver and muscle exceeded 80 ng g⁻¹ (lipid weight) and were higher than other values reported in the Southern Hemisphere. BDE-47 was the predominant congener, suggesting higher bioaccumulation potential and possible brown trout metabolism of higher congeners. Since there is no point source of PBDEs in the region and residues were dominated by lower brominated congeners, atmospheric transport could be the main source of these compounds. This first report of PBDEs levels in fish from Argentina contributes to the knowledge about environmental trends of these persistent organic pollutants (POPs) in remote areas such as the Andean Patagonia.     

Persistent organochlorine contaminants in hair samples of Northern Poland population, 1968-2009

The European regulation on chemicals, REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), came into force on 1 June 2007. With pre-registration complete in 2008, data for these substances may provide an overview of the expected chemical space and its characteristics. In this paper, using various in silico computation tools, we evaluate 48 782 neutral organic compounds from the list to identify hazardous and safe compounds. Two different classification schemes (modified Verhaar and ECOSAR) identified between 17% and 25% of the compounds as expressing only baseline toxicity (narcosis). A smaller portion could be identified as reactive (19%) or specifically acting (2.7%), while the majority were non-assigned (61%). Overall environmental persistence, bioaccumulation and long-range transport potential were evaluated using structure-activity relationships and a multimedia fugacity-based model. A surprisingly high proportion of compounds (20%), mainly aromatic and halogenated, had a very high estimated persistence (>195 d). The proportion of compounds with a very high estimated bioconcentration or bioaccumulation factor (>5000) was substantially less (6.9%). Finally, a list was compiled of those compounds within the applicability domain of the models used, meeting both persistence and bioaccumulation criteria, and with a long-range transport potential comparable to PCB. This list of 68 potential persistent organic pollutants contained many well-known compounds (all halogenated), but notably also five fluorinated compounds that were not included in the EINECS inventory. This study demonstrates the usability of in silico tools for identification of potentially environmentally hazardous chemicals.     

Gas/particle partitioning of polycyclic aromatic hydrocarbons in coastal atmosphere of the north Yellow Sea, China

Samples of gas- and particle-phase polycyclic aromatic hydrocarbons (PAHs) were collected at three sampling stations (Xiaomai Island, Laohutan, and Zhangzi Island) in the north Yellow Sea, China during November 2008 and September 2009 to study their atmospheric transport potential and the gas/particle distributions. The composition of PAHs was dominated by gaseous compounds. The percentages of the particle-phase PAHs to the total concentrations were found to be higher during the heating period than the non-heating period. The ratios of naphthalene and acenaphthene to phenanthrene, chrysene and dibenzo(a,h)anthracene showed an increasing trend from Xiaomai Island to Zhangzi Island, which can be called as the local atmospheric distillation of PAHs. Gas/particle partitioning coefficients (K _p) and their relationship with the sub-cooled liquid vapor pressures (pº_L) of PAHs were investigated. The regressions of logK _p versus logpº_L gave significant correlations for all samples of the three sites with r ² values in the range 0.56–0.66 (p?<?0.01). Both Junge–Pankow adsorption model and octanol–air partition coefficient absorption model tended to underestimate the sorption for most PAHs, but the absorption model appeared to be more suitable for predicting the particle fraction of PAHs than the Junge–Pankow model.