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Costa Mesa, CA, United States

Lao W.,Southern California Coast Water Research Project
Se pu = Chinese journal of chromatography / Zhongguo hua xue hui | Year: 2013

Toxaphene quantification incorporating gas chromatography/negative chemical ionization mass spectrometry (GC/NCI-MS) offers improved sensitivity and specificity. The U. S. Environmental Protection Agency (USEPA) recently released a GC/NCI-MS method (Method 8276) for the measurement of technical toxaphene and eight specific congeners (Hx-Sed, Hp-Sed, P26, P41, P40, P44, P50 and P62). However, there is still lack of a practical and complete analytical method including sample extraction, clean up, instrumental analysis, and data analysis. The goal of this work was to develop a ready-to-use method for the quantification of total toxaphene and the eight congeners. Sediment and salmon fish tissue were selected as sample matrices and extracted with methylene chloride using an accelerated solvent extraction system. The sample extracts were cleaned up with active copper powder or gel permeation chromatography, and finally silica/alumina combination column. Separation was performed on a DB-XLB column. GC/NCI-MS was operated under selected ion monitoring mode with an identical set of confirmation and quantitation ions for total toxaphene and the eight congeners. Oxygen reaction of polychlorinated biphenyls (PCB) was monitored by PCB204, an internal calibration standard, and the reaction level was kept below 1%. Average relative response factors were used in quantitation. Quantitation of total toxaphene employed the sum of all detectable (S/N > or = 3) 6-C1 to 10-Cl homolog peak areas, while the individual congeners were quantified followed the standard procedures for single analytes. Multi-point calibration solutions ranged from 0. 5 (5 for P62) to 500 microg/L for the individual congeners, and 50 to 500 microg/L for technical toxaphene, with the lowest calibration levels as lower limits of quantitation. Average congener recovery was (90.8 +/- 17.4)% (n =10) in spiked sediment with relative standard deviations of 5.4% - 12.8% (n =10), underscoring an excellently accurate and precise method. The method was applied to analyze sediment and fish tissue sample. Source

Su J.,Chinese Institute of Urban Environment | Ouyang W.,Chinese Institute of Urban Environment | Ouyang W.,University of Chinese Academy of Sciences | Hong Y.,Chinese Institute of Urban Environment | And 6 more authors.
Journal of Soils and Sediments | Year: 2015

Purpose: Plants and their root-associated microbes play important roles in the remediation of polycyclic aromatic hydrocarbons (PAHs) present in the sediments of contaminated coastal wetlands. The detailed information about the effects of PAHs on root-associated bacterial communities could help to isolate PAH-degrading bacteria and optimize the process of phytoremediation. Materials and methods: The community structures of rhizospheric (RB) and endophytic bacteria (EB) of salt marsh plant (Spartina alterniflora) grown in phenanthrene (PHE)- and pyrene (PYR)-contaminated sediments (for 70 days) were investigated using the barcoded Illumina paired-end sequencing technique. Results and discussion: The diversity and community structure of EB and RB were more sensitive to PHE and PYR contamination as compared to those in the sediments. All samples were strongly clustered according to EB, RB, and sediments, suggesting the niche-specific influence of PAHs on bacterial communities. Potential PAH-degrading bacteria (Pseudomonas sp., Paenibacillus sp., and Flavobacterium sp.) in EB and RB were stimulated by PAH contamination. The results revealed an increase prevalence of specific bacteria which may be responsible for PAH degradation. PHE contamination increased the abundance of Proteobacteria in EB but decreased the number of Firmicutes, Bacteroidetes, and Chloroflexi. The numbers of Proteobacteria and Firmicutes in EB were enhanced by PYR treatment. However, both PHE and PYR treatment showed similar effects on the bacterial communities in RB. Conclusions: The results suggested that PAH pollution could alter root-associated bacterial communities of S. alterniflora, whose EB might play an important role in the phytoremediation of PAH-contaminated sediments. © 2015 Springer-Verlag Berlin Heidelberg Source

Lao W.,Southern California Coast Water Research Project | Maruya K.A.,Southern California Coast Water Research Project | Tsukada D.,Southern California Coast Water Research Project
Analytical Chemistry | Year: 2012

Determination of the analyte-specific distribution coefficient between the aqueous and sorbing phases is required for estimation of the aqueous-phase concentration of the analyte of interest using polymeric materials. Poly(dimethylsiloxane)-coated solid-phase microextration (PDMS-SPME) fiber-water partition coefficient (Kf) values for eight common-use pyrethroids were determined using a two-compartment mass balance model and parameters determined in experimental seawater microcosms. Mass balance, epimerization, and aqueous-phase degradation (i.e., hydrolysis) were characterized using gas chromatography-negative chemical ionization mass spectrometry to facilitate Kf estimation. Of the eight pyrethroids, only bifenthrin exhibited increasing sorption on the SPME fiber over the entire time-series exposure, indicating that its Kf value could be estimated through a stable-compound model. The remaining pyrethroids were found to be unstable (half-life of <22 days), underscoring the importance of accounting for degradation in estimating Kf. The two-compartment model explained the experimental time-series data for bifenthrin (R2 > 0.98) and the remaining unstable pyrethroids (R2 > 0.7), leading to estimated values of log Kf between 5.7 and 6.4, after correcting for residual dissolved organic carbon (DOC) in the experimental seawater. These Kf values can be used to determine freely dissolved pyrethroid concentrations in the pg/L range using PDMS-SPME in fresh or seawater matrices under equilibrium conditions in laboratory or field applications. © 2012 American Chemical Society. Source

Lao W.,Southern California Coast Water Research Project | Tiefenthaler L.,Southern California Coast Water Research Project | Greenstein D.J.,Southern California Coast Water Research Project | Maruya K.A.,Southern California Coast Water Research Project | And 3 more authors.
Environmental Toxicology and Chemistry | Year: 2012

Little is known about pyrethroid fate and effects in estuarine and marine environments. In the present study, the extent and magnitude of pyrethroids in coastal embayments of the Southern California Bight (SCB), USA, were assessed. Using a stratified probabilistic design, 155 sediment samples were collected from four embayment habitats (estuaries, marinas, open bays, and ports) and analyzed for eight common-use pyrethroids. Total pyrethroid concentrations ranged from less than 0.5 to 230μg/kg dry weight (area-weighted mean concentration=5.1±3.1μg/kg) and were detected in 35% of the total SCB embayment area. Estuaries and marinas had the greatest areal extent of detectable concentrations (up to 65%) and the greatest area-weighted mean concentrations (22.1±26.5μg/kg). Sites with the greatest pyrethroid concentrations were located near sources of runoff from urban watersheds. Bifenthrin and cyfluthrin were detected in 32 and 15% of all samples, respectively, whereas the other six pyrethroids were detected in ≤5% of samples. Permethrin and bifenthrin had the highest concentrations at 132 and 65μg/kg. Toxic units estimated for the marine amphipod Eohaustorius estuarius ranged from 0 to 5.8, exceeding unity in 9 and 32% of the total and estuary habitat areas, respectively, and were not correlated with mortality, suggesting that other factors (e.g., co-occurring contaminants, reduced bioavailability) may affect the predictive capability using a single test species. © 2012 SETAC. Source

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