Principal component analysis application in polycyclic aromatic hydrocarbons “mussel watch” analyses for source identification

Monitoring chemical contaminants in the Gulf of Maine, using sediments and mussels (Mytilus edulis): An evaluation

The objective of this paper is to determine whether contaminant data on mussels and sediments can be used interchangeably, or not, when assessing the degree of anthropogenic contamination of a water body. To obtain adequate coverage of the entire Gulf of Maine, Bay of Fundy sediment samples were collected, analyzed and combined with similar data from four coastal monitoring programs. This required careful interpretation but provided robust results consistent with published literature. A strong correspondence was found between sediment and mussel concentrations for polycyclic aromatic hydrocarbons, moderate to weak correspondence for polychlorinated biphenyls, and except for mercury and zinc, little to no correspondence was found for metals. We conclude that mussel contaminant data are likely sufficient for providing information on the spatial and temporal distribution of chemical contaminants, in coastal waters, under a broad range of environmental conditions and contaminant levels, and unlike sediments, provide direct information on contaminant bioavailability.

Characterization and ecological risk of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes in sediments of Shadegan international wetland, the Persian Gulf

The distribution and sources of PAHs and n-alkanes were determined in the surface sediments from 202 locations in Shadegan international wetland with 537,700ha. The concentrations of total n-alkanes and PAHs ranged from 395.3 to 14933.46μgg^-1dw and 593.74 to 53393.86ngg^-1dw, respectively. Compared with other worldwide surveys, the concentration and contamination of sedimentary hydrocarbons were classified very high. A common petrogenic hydrocarbon source was strongly suggested in all sites by n-alkanes' profile with a Cmax at n-C₂₀, Pr/Ph and CPI ratios<1 in all sites, and high percentage of UCM. Typical profile of petrogenic PAHs with alkyl-substituted naphthalenes and phenanthrenes predominance, various PAH ratios and multivariate analysis indicated that PAHs were mainly derived from petrogenic source. Naphthalene-derived compounds in all sites were significantly above their ERL, and adversely affected benthic biota. 92% of the sites had mean ERM values<0.1, indicating high ecological risk on the wildlife of the wetland.

Presence, distribution and risk assessment of polycyclic aromatic hydrocarbons in rice-wheat continuous cropping soils close to five industrial parks of Suzhou, China

Polycyclic aromatic hydrocarbons (PAHs) accumulated in agricultural soils are likely to threaten human health and ecosystem though the food chain, therefore, it is worth to pay more attention to soil contamination by PAHs. In this study, the presence, distribution and risk assessment of 16 priority PAHs in rice-wheat continuous cropping soils close to industrial parks of Suzhou were firstly investigated. The concentrations of the total PAHs ranged from 125.99 ng/g to 796.65 ng/g with an average of 352.94 ng/g. Phenanthrene (PHE), fluoranthene (FLT), benzo [a] anthracene (BaA) and pyrene (PYR) were the major PAHs in those soil samples. The highest level of PAHs was detected in the soils around Chemical plant and Steelworks, followed by Printed wire board, Electroplate Factory and Paper mill. The composition of PAHs in the soils around Chemical plant was dominated by 3-ring PAHs, however, the predominant compounds were 4, 5-ring PAHs in the soils around other four factories. Meanwhile, the concentration of the total PAHs in the soils close to the factories showed a higher level of PAHs in November (during rice harvest) than that in June (during wheat harvest). Different with other rings of PAHs, 3-ring PAHs in the soils around Chemical plant and Steelworks had a higher concentration in June. The results of principal component analysis and isomeric ratio analysis suggested that PAHs in the studied areas mainly originated from biomass, coal and petroleum combustion. The risk assessment indicated that higher carcinogenic risk was found in those sites closer to the industrial park.

Distribution and enrichment of trace metals in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana in the Gulf of Guinea

We present results of a preliminary geochemical assessment of Cd, Pb, V, As, Ni, Cu, Zn, Mg, Al, K, Ca, and Fe in marine sediments from the Eastern Equatorial Atlantic, off the Coast of Ghana. Samples were taken along 4 regions G1, G2, G3 and G4 at approximately 25m, 100m, and 250m, 500m and 1000m depths. Elemental compositions were assessed through the estimation of Al-normalized enrichment factors and geochemical accumulation indices, and the concentrations determined to produce any potential toxic effects to biota. Significant enrichment of the bottom sediments with Cd, Ni and As were observed at some locations with sediments showing signs of heavy pollution with As at region G4. Apart from Ni, V and As which were beyond threshold effects levels at most regions, all other metals were below probable effect levels. Both natural and anthropogenic processes controlled trace metal accumulation and distribution in the Ghanaian coastal environment.

Polycyclic aromatic hydrocarbons (PAHs) in starfish body and bottom sediments in Mohang Harbor (Taean), South Korea

The concentrations of 27 polycyclic aromatic hydrocarbons (PAHs) were determined in bottom sediments and starfish from Mohang Harbor (MH) in Taean peninsula, South Korea. In December 2007, crude oil washed ashore from the M/V Hebei Spirit and was subsequently cleaned up within a few months of the incident. The ecological risk, bioaccumulation factor (BAF), and composition of the 27 PAHs were examined. The PAH concentrations in the bottom sediment ranged from 24 to 366 μg/kg dried weight, and the ecological risk was determined as minimal (mERL-Q < 1). Total PAH concentrations in Asterina pectinifera (inside seawall) and Asterias amurensis (outside seawall) were 1,226 and 1,477 μg/kg dry weight (d.w.), respectively. The total BAFs (∑BAF) for A. amurensis was 3.8 times higher than that of A. pectinifera, and the PAH concentrations of 5-6 log K OW were highest in the two starfish species. Further, PAH fingerprint analysis (nine alkyl-substituted PAHs fraction, low molecular weight (LMW)/high molecular weight (HMW), Phe/Ant, and Flu/Pyr), and principal component analysis (PCA) based on three crude oil samples from the M/V Hebei Spirit showed no remaining influence of crude oil.

Evaluation of the potential bioaccumulation ability of the blood cockle (Anadara granosa L.) for assessment of environmental matrices of mudflats

The spatial distribution of 19 polycyclic aromatic hydrocarbons (tPAHs) was quantified in aquacultures located in intertidal mudflats of the west coast of Peninsular Malaysia in order to investigate bioaccumulation of PAH in blood cockles, Anadara granosa (A. granosa). Fifty-four samples from environmental matrices and A. granosa were collected. The sampling locations were representative of a remote area as well as PAH-polluted areas. The relationship of increased background levels of PAH to anthropogenic PAH sources in the environment and their effects on bioaccumulation levels of A. granosa are investigated in this study. The levels of PAH in the most polluted station were found to be up to ten-fold higher than in remote areas in blood cockle. These high concentrations of PAHs reflected background contamination, which originates from distant airborne and waterborne transportation of contaminated particles. The fraction and source identification of PAHs, based on fate and transport considerations, showed a mix of petrogenic and pyrogenic sources. The relative biota-sediment accumulation factors (RBSAF), relative bioaccumulation factors from filtered water (RBAFw), and from suspended particulate matter (SPM) (RBAFSP) showed higher bioaccumulations of the lower molecular weight of PAHs (LMWs) in all stations, except Kuala Juru, which showed higher bioaccumulation of the higher molecular weight of PAHs (HMWs). Calculations of bioaccumulation factors showed that blood cockle can accumulate PAHs from sediment as well as water samples, based on the physico-chemical characteristics of habitat and behaviour of blood cockles. Correlations among concentrations of PAHs in water, SPM, sediment and A. granosa at the same sites were also found. Identification of PAH levels in different matrices showed that A. granosa can be used as a good biomonitor for LMW of PAHs and tPAHs in mudflats. Considering the toxicity and carcinogenicity of PAHs, the bioaccumulation by blood cockles are a potential hazard for both blood cockles and their consumers.

ESTIMATION OF SOIL SORPTION COEFFICIENTS OF POLYCYCLIC AROMATIC HYDROCARBONS BY QUANTUM CHEMICAL DESCRIPTORS

Quantitative structure–property relationship (QSPR) modeling is a powerful approach for predicting environmental behavior of organic pollutants with their structure descriptors. This study reports an optimal QSPR model for estimating logarithmic soil sorption coefficients (log K OC ) of polycyclic aromatic hydrocarbons (PAHs). Quantum chemical descriptors computed using density functional theory at the B3LYP/6-31G(d) level and partial least squares (PLS) analysis with an optimizing procedure were used to generate QSPR models for log K OC of PAHs. The correlation coefficient of the optimal model was 0.993, and the results of a cross-validation test ([Formula: see text]) showed this optimal model had high fitting precision and good predicting ability. The log K OC values predicted by the optimal model are very close to those observed. The PLS analysis indicated that PAHs with larger electronic spatial extent tend to more easily adsorb and accumulate in soils and sediments, whereas those with higher molecular total energy and larger energy gap between the lowest unoccupied and the highest occupied molecular orbital adsorb and accumulate in soils and sediments less readily.

Identification of source of a marine oil-spill using geochemical and chemometric techniques

The current work aimed to identify the source of an oil spill off the coast of Maranhão, Brazil, in September 2005 and effect a preliminary geochemical survey of this environment. A combination of bulk analytical parameters, such as carbon isotope (δ(13)C) and Ni/V ratios, and conventional fingerprinting methods (High Resolution Gas Chromatography and Mass Spectrometry) were used. The use of bulk methods greatly speeded source identification for this relatively unaltered spill: identification of the likely source was possible at this stage. Subsequent fingerprinting of biomarker distributions supported source assignment, pointing to a non-Brazilian oil. Steranes proved the most useful biomarkers for sample correlation in this work. Distribution patterns of environmentally more resilient compound types, such as certain aromatic structures, proved inconclusive for correlation, probably in view of their presence in the background.

A novel approach for characterization of polycyclic aromatic hydrocarbon (PAH) pollution patterns in sediments from Guanabara Bay, Rio de Janeiro, Brazil

A novel multivariate method based on principal component analysis of pre-processed sections of chromatograms is used to characterize the complex PAH pollution patterns in sediments from Guanabara Bay, Brazil. Five distinct sources of 3- to 6-ring PAHs could be revealed. The harbour is the most contaminated site in the bay, its plume stretches in a South West to North East direction and the chemical profile indicates mainly pyrogenic sources mixed with a fraction of high-molecular-weight petrogenic PAHs. Rio São João de Meriti is the second largest source of PAHs, and introduces mainly a fraction of low-molecular-weight petrogenic PAHs from the western region of Rio de Janeiro. The sites close to the ruptured pipeline at the Duque de Caxias Refinery show a distinctive pollution pattern indicating a heavy petroleum fraction. The method also led to the identification of new potential indicator ratios also involving coeluting peaks (e.g., triphenylene and chrysene).

Estimation of n-octanol/water partition coefficients of polycyclic aromatic hydrocarbons by quantum chemical descriptors

Quantitative structure-property relationship (QSPR) modeling is a powerful approach for predicting environmental behavior of organic pollutants with their structure descriptors. This study reports an optimal QSPR model for estimating logarithmic n-octanol/water partition coefficients (log K OW) of polycyclic aromatic hydrocarbons (PAHs). Quantum chemical descriptors computed with density functional theory at B3LYP/6-31G(d) level and partial least squares (PLS) analysis with optimizing procedure were used for generating QSPR models for log K OW of PAHs. The squared correlation coefficient (R 2) of the optimal model was 0.990, and the results of crossvalidation test (Q 2cum=0.976) showed this optimal model had high fitting precision and good predictability. The log K OW values predicted by the optimal model are very close to those observed. The PLS analysis indicated that PAHs with larger electronic spatial extent and lower total energy values tend to be more hydrophobic and lipophilic.

Protective effects of selenium on mercury-induced DNA damage in mussel haemocytes

Little is known of the antioxidant role of selenium (Se) in aquatic invertebrates. We investigated the effects of Se on mercury-induced DNA damage in haemocytes from Mytilus edulis using alkaline single cell gel electrophoresis, that is, the Comet assay. The basal percentage tail DNA value for mussel haemocytes was 9.8+/-0.2% (mean+/-S.E.M., n=70). Exposing mussels to Hg(2+) (nominal concentration 20 microgL(-1)) for three days led to an increase in tail DNA to 61.1+/-1.8% (n=10). With added Se (as selenite, nominal concentration 4 microgL(-1)), Hg-induced DNA damage was reduced to 39.5+/-3.1% (n=10). Se pre-exposure also provided some protection against Hg-induced DNA damage (% tail DNA=51.0+/-2.9%, n=10). Basal glutathione peroxidase (GPx) activity in cell-free haemolymph was 93.7+/-3.5 nmol min(-1)mg(-1) (mean+/-S.E.M., n=70). Increases in GPx activity were seen when Se was added during and/or after exposure to Hg. For example, a 3-4-fold increase was seen after three days exposure to Hg in the presence of added Se. Interestingly GPx activity doubled after three days in the presence of added Se alone, but was unchanged after exposure to HgCl(2) alone. These results suggest that the availability of Se in the natural environment could affect the antioxidant status of mussels, and consequently could affect levels of DNA damage.

Modeling and prediction of photolysis half-lives of polycyclic aromatic hydrocarbons in aerosols by quantum chemical descriptors

Quantitative structure-property relationship (QSPR) modeling is a powerful approach for predicting environmental fate parameters of organic pollutants with their structure descriptors. This study reports QSPR models for photolysis half-lives of polycyclic aromatic hydrocarbons (PAHs) in aerosols. Quantum chemical descriptors computed with density functional theory at B3LYP/6-31G(d) level and partial least squares (PLS) analysis with optimizing procedure were used for generating QSPR models. The correlation coefficient of the optimal model was 0.993, and the fitting results showed this optimal model had high fitting precision and good predictability. The predicted photolysis half-lives by the optimal model are very close to those observed. The PLS assistant analysis indicated that PAHs with large electronic spatial extent tend to be photolyzed faster, while PAHs with high molecular total energy and small Mulliken atomic charges on the most negative carbon atom tend to be photolyzed slower in aerosols.

Long-term change of polycyclic aromatic hydrocarbon deposition to peatlands of eastern Canada

To date, studies about historic PAH (polycyclic aromatic hydrocarbons) deposition at a regional scale have rarely been published. To address this research gap, we sampled 17 ombrotrophic peatlands across eastern Canada. The peat cores from hollows were dated with 210Pb for the period of about 1850-2000 and analyzed fortheir PAH concentration, so PAH deposition could be reconstructed. Peat samples were extracted by accelerated solvent extraction (ASE). The extracts were purified by column chromatography with aluminum oxide and silica gel. PAH were measured by gas chromatography-tandem mass spectrometry (GC-MS/MS). Overall reconstructed deposition rates of sigma-11 PAH ranged from 4 to 1432 microg m(-2) year(-1). Three different long-term trends in PAH deposition could be distinguished: sites with two separated periods of maximum PAH deposition, sites with one period of maximum PAH deposition, and sites with no clearly separated period of maximum PAH deposition. Increasing PAH depositions were caused by rapid industrialization accompanied by extensive use of fossil fuels; decreasing PAH depositions were caused by substitution of these fuels and movements of PAH emitting industry to different regions. At all sites either phenanthrene (20-60%) or benzo[b+k]fluoranthene (10-40%) was the predominant PAH. Detailed analysis of three bogs suggested that combustion of coal and vehicle exhausts mainly contributed to the peat PAH burden. The temporal trends of PAH deposition indicated that increases in the PAH deposition rates followed the industrial development in Canada, particularly in the periods 1880-1910 and 1940-1960. Recent abatement efforts were reflected in decreased PAH deposition rates to about 15% of the maximum.

Chromatographic preprocessing of GC–MS data for analysis of complex chemical mixtures

Hyphenated analytical techniques such as gas chromatography-mass spectrometry (GC-MS) can provide extensive amounts of analytical data when applied to environmental samples. Quantitative analyses of complex contaminant mixtures by commercial preprocessing software are time-consuming, and baseline distortion and incomplete peak resolution increase the uncertainty and subjectivity of peak quantification. Here, we present a semi-automatic method developed specific for processing complex first-order chromatographic data (e.g. selected ion monitoring in GC-MS) prior to chemometric data analysis. Chromatograms are converted into semi-quantitative variables (e.g. diagnostic ratios (DRs)) that can be exported directly to appropriate softwares. The method is based on automatic peak matching, initial parameterization, alternating background noise reduction and peak estimation using mathematical functions (Gaussian and exponential-Gaussian hybrid) with few (i.e. three to four) parameters. It is capable of resolving convoluted peaks, and the exponential-Gaussian hybrid improves the description of asymmetric peaks (i.e. fronting and tailing). The optimal data preprocessing suggested in this article consists of estimation of Gaussian peak parameters and subsequent calculation of diagnostic ratios from peak heights. We tested the method on chromatographic data from 20 replicate oil samples and found it to be less time-consuming and subjective than commercial software, and with comparable data quality.

Heavy metal distribution in marine sediments from the southwest coast of Spain

The latest version (1999) of the BCR-sequential extraction technique was used to determine the distribution of metals (Cu, Zn, Cd, Pb, Fe, Ni, Cr, and Mn) with major sedimentary phases (acid-soluble, reducible, oxidisable and residual) in samples from the southwest coast of Spain. The total metal content was also determined. The results showed that an extensive area along the coast (35 km long), near the joint mouth of the Tinto and Odiel Rivers, contains sediments with high concentrations of metals, with maximums of 649 mg/kg of Zn, 336 mg/kg of Cu, 197 mg/kg of Pb and 2.5 mg/kg of Cd. The values found for Cr, Ni and Mn are comparable to those in unpolluted areas. Based on the chemical distribution of metals, we found that Zn is the most mobile (i.e., it can pass easily into the water under changing environmental conditions). This metal showed the highest percentages in the acid-soluble fraction (the most labile), especially in the central coastal area, where the samples contained over 50% of this element associated with this fraction. This area close to the Tinto and Odiel river mouths also shows a significant increase in the mobility of Cd and Cu. In both cases the amount present in the residual fraction is lower, and the acid-soluble fraction is increased for Cd and the oxidisable fraction for Cu. However, the highest percentages of Fe, Cr and Ni are found in the residual fraction (84%, 89% and 75%, respectively), which implies that these metals are strongly bound to the sediments.