Phenanthrene sorption by aliphatic-rich natural organic matter

Contaminant sorption, an important process that may limit bioavailability, hinder remediation, encourage environmental persistence, and control mobility in the environment, has been the focus of numerous studies. Despite these efforts, the fundamental understanding of sorptive processes in soil and sedimentary environments has not been resolved. For instance, many have suggested that contaminants, such as polycyclic aromatic hydrocarbons (PAHs), solely interact with aromatic domains of organic matter. Until now, studies have neglected the aliphatic components that are known to be a recalcitrant and significant part of soil and sedimentary organic matter (SOM). In this investigation, the sorption of phenanthrene to several aliphatic-rich SOM samples was measured. The samples included the following: SOM precursors (algae, degraded algae, cellulose, collagen, cuticle, and lignin), two kerogen samples, and a highly aromatic humic acid. All samples were characterized by cross polarization magic angle spinning carbon-13 (CPMAS 13C) NMR and carbon, hydrogen, and nitrogen analysis. Batch experiments demonstrated that the highest organic carbon normalized sorption coefficients (Koc values) were obtained with the Pula kerogen sample (log Koc = 4.88) that only contains 6.5% aromatic carbon. Other aliphatic-rich samples, namely the Green River kerogen, degraded algae, and collagen samples produced comparable log Koc values (4.64, 4.66, and 4.72, respectively) to that of the highly aromatic humic acid (log Koc = 4.67). Phenanthrene uptake was the least for cellulose and lignin, two major soil components. A comparison of phenanthrene Koc values and paraffinic carbon content revealed a positive correlation (Koc = 798 +/- 96.1 * paraffinic carbon (%), r2 = 0.56) and indicates that amorphous polymethylene carbon is an important consideration in phenanthrene sorption. This study establishes that aliphatic SOM domains have a strong affinity for phenanthrene and likely, other PAHs. Therefore, aliphatic structures, that are an important component of SOM, require more attention in the examination of sorption processes in terrestrial and sedimentary environments.     

Identification and characterization of sorption domains in soil organic matter using strucuturally modified humic acids

The sorption of phenanthrene was examined in humic acids (HAs) from different sources: a compost, a peat soil, and a mineral soil. Sub-samples of each HA were subjected to bleaching or hydrolysis to remove predetermined chemical groups from their structures. Bleaching successfully removed a large percentage of rigid, aromatic moieties, whereas hydrolysis removed the mobile, carbohydrate components. Phenanthrene sorption by all HAs was nonlinear (N < 1). However, the phenanthrene isotherms of the bleached HAs were more linear than those of the untreated HAs, whereas the removal of the carbohydrate components by hydrolysis produced more nonlinear isotherms. The introduction of pyrene to the phenanthrene sorption system yielded more linear isotherms for all the HAs, indicative of competitive sorption. Proton spin-spin (1H T2) relaxation determined by nuclear magnetic resonance (NMR) was used to identify separate rigid (condensed) and flexible (expanded) 1H populations and to determine their distribution. These 1H domains were highly sensitive to temperature and correlated well with reported glass transition temperatures for HAs. In combination with the chemical treatments, sorption, and spectroscopic data, we were able to observe some significant relationships among chemical groups, sorption behavior, and structural characteristics.     

Insights into the sorption properties of cutin and cutan biopolymers

Plant cuticles have been reported as highly efficient sorbents for organic compounds. The objective of this study was to elucidate the sorption and desorption behavior of polar and nonpolar organic compounds with the major structural components of the plant cuticle: the biopolymers cutin and cutan. The sorption affinity values of the studied compounds followed the order: phenanthrene > atrazine > chlorotoluron > carbamazepine. A higher sorption affinity of phenanthrene and atrazine to cutin was probably due to the higher level of amorphous paraffinic carbon in this biopolymer. Phenanthrene exhibited reversible sorption behavior and a high ratio of organic-carbon-normalized distribution coefficient (Koc) to carbon-normalized octanol-water partitioning coefficients (Kowc) with both biopolymers. This suggests that both biopolymers provide phenanthrene with a partition medium for hydrophobic interactions with the flexible long alkyl-chain moieties of the biopolymers. The low Koc/Kowc ratios obtained for the polar sorbates suggest that the polar sites in the biopolymers are not accessible for sorption interactions. Atrazine and carbamazepine exhibited sorption-desorption hysteresis with both sorbents, indicating that both sorbates interact with cutin and cutan via both hydrophobic and specific interactions. In general, the sorptive properties of the studied biopolymers were similar, signifying that the active sorption sites are similar even though the biopolymers exhibit different properties.     

Sorption and conformational characteristics of reconstituted plant cuticular waxes on montmorillonite

Plant cuticular waxes are essential barriers that regulate the transport of water and organic molecules to intact cuticular membranes. They also compose a significant fraction ofthe recalcitrant aliphatic components of soil organic matter (SOM). In this study, we examined the sorption and desorption of three polycyclic aromatic hydrocarbons (PAHs), naphthalene (NAPH), phenanthrene (PHEN), and pyrene (PYR), by cuticular waxes of green pepper (Capsicum annuum) that had been reconstituted by loading them onto montmorillonite (at four different loadings). The reconstituted wax samples, with and without sorbed PAHs, were characterized by solid-state 13C NMR to supply the evidence of melting transition. The sorption isotherms fit well to a Freundlich equation. Sorption isotherms were practically linear except for that of PYR sorption to the low-load wax-montmorillonite sample. The organic-carbon-normalized sorption coefficients (Koc) depended on PAH's lipophilicity (e.g., octanol-water partition coefficient) and increased with increasing wax-load on clay. Desorption was dependent on PAH's molecular sizes and sorbed amounts and on the wax load of the clay. Desorption hysteresis was observed only at high loads of NAPH and PHEN, and it decreased with both increasing wax load and molecular size (i.e. NAPH > PHEN > PYR). Contributing to hysteresis, the melting transition of the reconstituted waxes after sorbing the PAHs was confirmed by solid-state 13C NMR data. Upon adsorption, the intensity of the NMR peak at 29 ppm (attributed to mobile amorphous paraffinic domains) increased, and a peak at 167 ppm (-COOH) appeared, reflecting the transition of solid amorphous to mobile amorphous domains in the reconstituted waxes. The intensity of melting induced by PAH adsorption decreased with increasing PAH molecular size.     

Importance of black carbon to sorption of native PAHs, PCBs, and PCDDs in Boston and New York harbor sediments

The solid-water distribution ratios (Kd values) of "native" PAHs, PCBs, and PCDDs in Boston and New York Harbor sediments were determined using small passive polyethylene samplers incubated for extended times in sediment-water suspensions. Observed solid-water distribution coefficients exceeded the corresponding f(oc)Koc products by 1-2 orders of magnitude. It was hypothesized that black carbon (fBC), measured in the Boston harbor sediment at about 0.6% and in the New York harbor sediment at about 0.3%, was responsible for the additional sorption. The overall partitioning was then attributed to absorption into the organic carbon and to adsorption onto the black carbon via Kd = f(oc)Koc + f(BC)K(BC)C(w)n-1 with Cw in microg/L. Predictions based on published Koc, K(BC), and n values for phenanthrene and pyrene showed good agreement with observed Kd,obs values. Thus, assuming this dual sorption model applied to the other native PAHs, PCBs, and PCDDs, black carbon-normalized adsorption coefficients, K(BC)S, were deduced forthese contaminants. Log K(BC) values correlated with sorbate hydrophobicity for PAHs in Boston harbor (log K(BC) approximately 0.83 log gamma w(sat) - 1.6; R2 = 0.99, N= 8). The inferred sorption to the sedimentary BC phase dominated the solid-water partitioning of these compound classes, and its inclusion in these sediments is necessary to make accurate estimates of the mobility and bioavailability of PAHs, PCBs, and PCDDs.     

The partitioning of PAHs to egg phospholipids facilitated by copper and proton binding via cation-pi interactions

The partitioning to lipid-containing solids (cell membranes, natural organic matters) plays an important role in the fate of organic pollutants. We herein studied sorption of a series of aromatic compounds from aqueous solution to gel-phase egg phospholipids. The regression line describing the free-energy relationship between lipid-water distribution coefficient (Kd) and n-octanol-water partition coefficient (K(OW)) for the high-polar compounds (phenolics, dinitrobenzene, trinitrobenzene) is displaced upward relative to the low-polar compounds (chlorobenzenes, polycyclic aromatic hydrocarbons (PAHs), nitrobenzene, dichlorobenzonitrile), suggesting additive polar extra-interactions besides hydrophobic effects in sorption. Binding of Cu2+ or decreasing pH increases sorption of the three and four-ring PAHs but not the rest compounds. These results led us to propose a specific sorption mechanism, cation-pi bonding between PAHs and complexed metal ions or protonated amine groups of phospholipids. The Cu(2+)-PAH complexation in solution was supported by the observation that PAHs enhance the saturated solubility of CuSO4 in chloroform, and the enhancement correlates with pi-donor strength of PAH (pyrene > phenanthrene > naphthalene). The electron coupling between the protonated amine groups of phospholipids and PAHs in chloroform was verified by the electronic deshielding-induced downfield chemical shifts of phenanthrene at low pH in the 1H NMR spectrum.     

Sorption mechanisms of phenanthrene, lindane, and atrazine with various humic acid fractions from a single soil sample

The sorption behavior of organic compounds (phenanthrene, lindane, and atrazine) to sequentially extracted humic acids and humin from a peat soil was examined. The elemental composition, XPS and (13)C NMR data of sorbents combined with sorption isotherm data of the tested compounds show that nonspecific interactions govern sorption of phenanthrene and lindane by humic substances. Their sorption is dependent on surface and bulk alkyl carbon contents of the sorbents, rather than aromatic carbon. Sorption of atrazine by these sorbents, however, is regulated by polar interactions (e.g., hydrogen bonding). Carboxylic and phenolic moieties are key components for H-bonding formation. Thermal analysis reveals that sorption of apolar (i.e., phenanthrene and lindane) and polar (i.e., atrazine) compounds by humic substances exhibit dissimilar relationships with condensation and thermal stability of sorption domains, emphasizing the major influence of domain spatial arrangement on sorption of organic compounds with distinct polarity. Results of pH-dependent sorption indicate that reduction in sorption of atrazine by the tested sorbents is more evident than phenanthrene with increasing pH, supporting the dependence of organic compound sorption on its polarity and structure. This study highlights the different interaction mechanisms of apolar and polar organic compounds with humic substances.     

Importance of structural makeup of biopolymers for organic contaminant sorption

Sorption of pyrene, phenanthrene, naphthalene, and 1-naphthol by original (lignin, chitin, and cellulose) and coated biopolymers was examined. Organic carbon normalized distribution coefficients (Koc) of all compounds by the original biopolymers followed the order lignin > chitin > cellulose, in line with the order of their hydrophobicity. Hydrophobicity of structurally similar organic compounds is the main factor determining their ability to occupy sorption sites in biopolymers. Specific interactions (e.g., H-bonding) between 1-naphthol and chitin or cellulose increased its ability to occupy sorption sites. Lignin coating resulted in an increased Koc for phenanthrene (13.6 times for chitin and 6.9 times for cellulose) and 1-naphthol (6.0 times for chitin and 3.7 times for cellulose) relative to the acetone-treated chitin and cellulose. Also, these coated biopolymers had increased isotherm nonlinearity, due to the newly formed condensed domains. An increase in phenanthrene and 1-naphthol sorption by lignin-coated biopolymers as compared to chitin and cellulose was contributed by the newly created high-energy sites in condensed domains and coated lignin. Results of this study highlight the importance of the structural makeup of biopolymers in controlling the sorption of hydrophobic organic compounds.     

GC-MS测定4类食品接触材料中多环芳烃类化合物的溶出暴露水平

建立了食品接触材料中16种多环芳烃类化合物溶出暴露的气相色谱质谱联用(GC-MS)分析方法。样品以异辛烷为模拟物,按实际使用情况进行模拟浸泡实验,所得浸泡液用GC-MS进行分析。结果表明,食品接触材料中4种多环芳烃类化合物(萘、菲、荧蒽和芘)存在一定程度的溶出暴露水平,检出率分别为萘24.3%、菲77.1%、荧蒽48.6%、芘44.3%。其中部分食品用容器多环芳烃的溶出水平最高达33545 ng/kg(萘)、46296 ng/kg(菲)、17739 ng/kg(荧蒽)、15594 ng/kg(芘),并发现常规项目蒸发残渣(正己烷)的溶出与多环芳烃的溶出存在一定的正相关关系。萘、菲、荧蒽、芘等四项多环芳烃的方法平均回收率为76.5%~100.7%,相对标准偏差为1.0%~3.5%,本研究方法具有较好的准确度和精密度。     

Sorption of phenanthrene by nonhydrolyzable organic matter from different size sediments

Nonhydrolyzable organic carbon (NHC) and sorption isotherms of phenanthrene (Phen) on six size-fractionated NHC fractions in two sediments from the Pearl River and Estuary, South China, were investigated. It was found that NHC including ancient organic carbon, black carbon, resistant aquatic organic carbon, and aged soil organic carbon consists mainly of aliphatic and aromatic carbon using 13C nuclear magnetic resonance spectroscopy. The sorption isotherms of Phen by the size-fractionated NHC fractions are nonlinear and are well-fitted to the Freundlich model. For the estuary sediment, the NHC contents and the organic carbon-normalized distribution coefficients (Koc) in the size fractions increase with decreasing particle size. The clay NHC fraction contributes to 70% of the Phen sorption by the bulk NHC isolate. However, for the contaminated river sediment, the NHC contents and the Koc values exhibit no regular variations among the size fractions. The Phen sorption capacities on the size-fractionated NHC fractions of the two sediments are significantly related to their H/C ratios and aliphatic carbon, but negatively to aromatic carbon. The fine-particle NHC fractions with high aliphatic carbon and H/C ratio play a very important role in the sorption, transport, and fate of Phen by the investigated sediments.     

Sorption of organic contaminants by biopolymer-derived chars

Sorption of phenanthrene and naphthalene by chitin and cellulose, as well as these biopolymer-derived chars, was examined. Carbon contents were much higher in the chars than their respective biopolymers, and nitrogen was dramatically accumulated in the chitin-derived chars. After charring, sorption of these two compounds was greatly increased, which was attributed to the newly created surface area, porosity, and aromatic components. The aromatic carbon content of the biopolymer chars increased with an increase in the charring temperature. Sorption of phenanthrene and naphthalene to chitin and cellulose was dominated by partitioning. However, after charring, sorption of these two compounds became much more of an adsorption process, because of the newly created surfaces and micropores. The maximum mass sorption capacity of phenanthrene and naphthalene by the original biopolymers and their chars was positively correlated with their surface areas, suggesting that active sorption sites were largely on the surfaces of chars. At low solute concentrations, sorption of phenanthrene and naphthalene by biopolymer chars was dominated by the micropore-filling mechanism; with an increase in the solute concentration, sorption of these two compounds by biopolymer chars shifted to a surface-sorption-dominant process.The maximum mass sorption capacity and K(ow)-normalized sorption amount of phenanthrene were lower than those of naphthalene by the biopolymers and their chars, showing the influence of molecular dimension on sorption. This study demonstrates the significantly enhanced sorption of hydrophobic organic compounds by highly polar biopolymers through charring and the joint roles of surface area, porosity, and surface functionalities of biopolymer-derived chars in governing sorption.     

Assessing sequestration of selected polycyclic aromatic hydrocarbons by use of adsorption modeling and temperature-programmed desorption

Sequestration of phenanthrene and pyrene was investigated in two soils--a sandy soil designated SBS and a silt-loam designated LHS--by combining long-term batch sorption studies with thermal desorption and pyrolysis of amended soil samples. The Polanyi-based adsorption volume and the adsorbed solute mass increased with aging for both soils, thus demonstrating the mechanism for observed sequestration. Despite rigorous thermal analysis, 30-62% (SBS sand) and 8-30% (LHS silt-loam) of phenanthrene could not be recovered after 30-270 days of sorption, with the increase in desorption resistance showing greater significance in SBS sand. For both soils, these values were 20-65% of adsorbed phenanthrene mass. Activation energies estimated from the temperature-programmed desorption (TPD) of sorbed phenanthrene at < or = 375 degrees C were 51-53 kJ/mol, consistent with values derived for desorption of organic compounds from humic materials. The activated first-order model fitting of observed TPD data supports the conclusion that the desorption-resistant fraction of phenanthrene has become sequestered onto condensed organic domains and requires temperatures exceeding 600 degrees C to be released. The work demonstrates the use of thermal analysis in complementing the Polanyi-based adsorption modeling approach for assessing the mechanistic basis for sequestration of organic contaminants in soils.     

Inhibition of free DNA degradation by the deformation of DNA exposed to trace polycyclic aromatic hydrocarbon contaminants

A rapid inhibitory effect of polycyclic aromatic hydrocarbons (PAHs) on DNA degradation was examined by conventional spectral analysis and microtitration. The purpose was to determine whether PAHs inhibited free DNA degradation by the enzyme DNase I. The results showed that model PAHs phenanthrene and pyrene combined with free DNA to decelerate DNA degradation by DNase I. Phenanthrene-induced inhibition was stronger than that of pyrene. Trace level of PAHs did not induce DNase I deactivation. The DNase I enzyme exhibited only slight shifts in IR absorption bands related to amide II and III upon PAH exposure, and no change was observed with other bands. The decelerating degradation of DNA is attributed to the changes in structure, backbone composition, and guanine constituents of DNA induced by PAHs inserted into double strands, and to the imidazole-like derivates from the combination of imidazole rings with pyrene.     

Indoor levels of polycyclic aromatic hydrocarbons in homes with or without wood burning for heating

The aim of this study was to investigate the impact of domestic wood burning on indoor levels of polycyclic aromatic hydrocarbons (PAHs). Indoor and outdoor concentrations of 27 PAHs were measured during wintertime in homes with (n= 13) or without (n 0) wood-burning appliances and at an ambient site in a Swedish residential area where wood burning for space heating is common. Twenty-four hour indoor levels of anthracene, benzo(ghi)fluoranthene, cyclopenta(cd)pyrene, benz(a)anthracene, chrysene/triphenylene, benzo(a)pyrene (BaP), indeno(1,2,3-cd)pyrene, benzo(ghi)perylene, and coronene were significantly (about 3- to 5-fold) higher in homes with, compared with homes without, wood-burning appliances. The outdoor levels of PAHs were generally higher than the indoor levelsfor all PAHs exceptforthe methylated phenanthrenes. The total PAH cancer potency (sum of BaP equivalents) was significantly higher (about 4 times) in the wood-burning homes compared with the reference homes, with BaP being the largest contributor, while phenanthrene made the largest contribution to the total PAH concentration in indoor and outdoor air. The median indoor BaP level in the wood-burning homes (0.52 ng/m3) was 5 times higher than the Swedish health-based guideline of 0.1 ng/m3, which was also exceeded outdoors on all days (median 0.37 ng/m3).     

Sorption of polar and nonpolar aromatic organic contaminants by plant cuticular materials: role of polarity and accessibility

In both forest and agricultural soils, plant derived cuticular materials can constitute a significant part of soil organic matter. In this study, the sorption of nonpolar (naphthalene and phenanthrene) and polar (phenol and 1-naphthol) aromatic organic pollutants to aliphatic-rich cuticularfractions of green pepper (Capsicum annuum) (i.e., bulk (PC1), dewaxed (PC2), nonsaponifiable (PC3), nonsaponifiable-nonhydrolyzable (PC4), and dewaxed-hydrolyzed residue (PC5)) were examined to better understand the influence of polarity and accessibility on their sorption behavior. The polarity and structures of cuticular fractions were characterized by elemental analysis, Fourier transform infrared spectroscopy, and solid-state 13C NMR. The sorption isotherms fit well to the Freundlich equation. Sorption of the tested organic compounds to PC4, which had more condensed domains, was nonlinear (Freundlich N(s) values of 0.766-0.966). For naphthalene and phenanthrene, the largest sorption capacity (K(oc)) occurred in PC5, which contained the highest paraffinic carbons (63%) and the lowest polarity: approximately 2 and aproximately 3 times higher than the respective carbon-normalized octanol-water partition coefficient (K(owc)), indicating that PC5 was a powerful sorption medium. For phenol and 1-naphthol, the largest K(oc) values occurred in PC4 with polar aromatic cores: approximattely 17 and approximately 7 times higher than the respective K(owc), suggesting that PC4 was much more accessible and compatible to polar aromatic pollutants than nonpolar aromatic pollutants. There was little or no correlation of K(oc) with either aliphatic or aromatic components of the tested aliphatic-rich sorbents because the polarity and accessibility apparently played a regulating role in the sorption of organic contaminants.     

Measuring and modeling adsorption of PAHs to carbon nanotubes over a six order of magnitude wide concentration range

Understanding the interactions between organic contaminants and carbon nanomaterials is essential for evaluating the materials' potential environmental impact and their application as sorbent. Although a great deal of work has been published in the past years, data are still limited in terms of compounds, concentrations, and conditions investigated. We applied a passive sampling method employing polyoxymethylene (POM-SPE) to gain a better understanding of the interactions between polycyclic aromatic hydrocarbons (PAHs) and multiwalled carbon nanotubes (CNTs) over a 6 orders of magnitude wide concentration range. In the low-concentration range (pg-ng L(-1)), sorption of phenanthrene and pyrene was linear on a nonlogarithmic scale. Here, sorption could thus be described using a single sorption coefficient. Isotherm fits over the entire concentration range showed that (i) monolayer sorption models described the data very well, and (ii) the CNTs sorption capacity was directly related to their surface area. Sorption coefficients for 13 PAHs (11 of which have not been reported to date) were also measured at environmentally relevant low concentrations. No competition seemed to occur in the low-concentration range and sorption affinity was directly related to the solubility of the subcooled liquid of the compounds.     

Enhanced sorption of polycyclic aromatic hydrocarbons to tetra-alkyl ammonium modified smectites via cation-pi interactions

The objective of this study was to characterize molecular sorptive interactions of polycyclic aromatic hydrocarbons (PAHs) by organoclays modified with quaternary ammonium cations. Three PAHs, naphthalene (NAPH), phenanthrene (PHEN), and pyrene (PYR), and three chlorobenzenes, 1,2-dichlorobenzene (DCB), 1,2,4,5-tetrachlorobenzene (TeCB), and pentachlorobenzene (PtCB), were sorbed from aqueous solution to reference montmorillonite clays (SWy-2) exchanged respectively with tetramethyl ammonium (TMA), tetraethyl ammonium (TEA), tetra-n-butyl ammonium (TBA), and hexadecyltrimethyl ammonium (HDTMA) cations. Solute hydrophobicities are compared between PAHs and chlorobenzenes using the solute n-octanol-water partition coefficient, n-hexadecane-water partition coefficient, and polyethylene-water distribution coefficient. The PAHs show several- to more than 10-fold greater sorption than the chlorobenzenes having close hydrophobicities but fewer delocalized pi electrons (NAPH/DCB, PHEN/TeCB, and PYR/ PtCB) by TEA-, TBA-, and HDTMA-clays. Furthermore, the PAHs show greater trends of solubility enhancement than the compared chlorobenzenes by TMA, TEA, and TBA in aqueous solution. The enhanced sorption and aqueous solubility of PAHs are best described by cation-pi interactions between ammonium cations and PAHs relative to chlorobenzenes that are incapable of such interactions. Cation-pi complexation between PAHs and tetra-alkyl ammonium cations in chloroform was verified by ring-current-induced upfield chemical shifts of the alkyl groups of cations in the 1H NMR spectrum.     

Inclusion of persistent organic pollutants in humification processes: direct chemical incorporation of phenanthrene via oxidative coupling

The participation of phenanthrene in phenol-coupling reactions mediated by horseradish peroxidase was investigated. Aqueous-phase concentrations of phenanthrene were observed to decrease dramatically with phenol as a result of the formation of precipitated products, suggesting a potential means for simultaneous treatment of phenolic contaminants and polycyclic aromatic hydrocarbons (PAHs) using peroxidase-mediated oxidative coupling processes. The studies reveal that phenanthrene removal from the aqueous phase occurs by a combination of sorption by and chemical bonding to precipitated reaction products. In that the oxidative coupling reactions of phenolics comprise an important step in the initiation of humification processes, the results obtained provide insights to potential roles that natural humification may play in the sorption, sequestration, and environmental fate of PAHs and other organic xenobiotics of similar nature.     

Sources, vertical fluxes, and equivalent toxicity of aromatic hydrocarbons in coastal sediments of the Río de la Plata Estuary, Argentina

Settling particles and bottom sediments collected at 1, 2.5, and 4 km off the metropolitan Buenos Aires coast in the Río de la Plata were analyzed to evaluate the sources and toxicity of resolved (PAHs) and unresolved (AROUCM) aromatic hydrocarbons. PAHs (0003-2.1 microg g(-1)) and AROUCM (0.01-78 microg g(-1)) presented the highest concentrations nearthe Buenos Aires port and sewer and decreasing values up- and downstream and along on- and offshore gradients. Sediment traps deployed in the Central area revealed large aromatic fluxes (1.3 +/- 1.5 and 31 +/- 47 mg m(-2) day(-1) for PAHs and AROUCM). The composition of sedimentary PAHs was dominated by uniformly distributed high molecular weight pyrogenic PAHs (53 +/- 11% fluoranthene, pyrene, and heavier PAHs), followed by diagenetically derived perylene more abundant in less polluted sites (29 +/- 15%) and lower molecular weight petrogenic PAHs (18 +/- 7.1% phenanthrene, anthracene, and methylated compounds), which covaried inversely with perylene. PAH diagnostic ratios indicated a stronger influence of petrogenic discharges close to the shore and the prevalence of combustion of fossil fuels and vehicle emissions over wood in offshore sediments. Sediment cores showed sustained hydrocarbon levels with decreasing proportion of petrogenic PAHs and relative enrichment of pyrogenic components and perylene down to 20-cm depth. PAH toxicity assessment by sediment quality guidelines (SQG) and dioxin-equivalent factors (PAH TEQ: 0.08-395 pg g(-1) dw) identified 1-2.5 km sediments close to the port and sewer as the most affected area. According to SQG, dibenz[a,h]anthracene and pyrene were the most critical PAHs, followed by benzo[a]pyrene, benz[a]anthracene, and chrysene. In contrast, PAH TEQs were dominated by indeno[1,2,3-cd]pyrene, benzo[k]fluoranthene, benzo[a]pyrene, perylene, and benz[a]anthracene which accounted for an average 86 +/- 5.7% of total TEQs.