Poly- and Perfluorinated Alkyl Substances in Air and Water from Dhaka, Bangladesh.

Bangladesh hosts extensive textile manufacturing, for some of which per- and polyfluorinated alkyl substances (PFAS) have been used to impart water and dirt repellency, among other things. Textile waste emissions to the atmosphere and discharge into rivers and other bodies of water could present a significant concern for human and ecosystem health, but there is little information on PFAS in Bangladesh. To assess the presence of ionic PFAS and their precursors in air and water from Dhaka, Bangladesh, polyethylene sheets were deployed for 28 days as passive samplers for neutral PFAS in outdoor air and water, while ionic PFAS were measured from discrete water grabs. Fluorotelomer alcohols (FTOHs) were detected at almost all sites in air and water; the most frequently detected compound was 6:2 FTOH, ranging from below instrumental detection limits (

The Air that we Breathe: Neutral and volatile PFAS in Indoor Air.

Sources of exposure to per- and polyfluorinated alkyl substances (PFAS) include food, water, and given that humans spend typically 90% of our time indoors, air and dust. Quantifying PFAS prevalent indoors, such as neutral, volatile PFAS, and estimating their exposure risk to humans is thus important. To accurately measure these compounds indoors, polyethylene (PE) sheets were employed and validated as passive detection tools, and analyzed by gas chromatography-mass spectrometry. Air concentrations were compared to dust and carpet concentrations reported elsewhere. Partitioning between PE sheets of different thicknesses suggested that interactions of the PEs with the compounds are occurring by absorption. Volatile PFAS, specifically fluorotelomer alcohols (FTOHs), were ubiquitous in indoor environments. For example, in carpeted Californian kindergarten classrooms, 6:2 FTOH dominated with concentrations ranging from 9-600 ng m-3, followed by 8:2 FTOH. Concentrations of volatile PFAS from air, carpet and dust were closely related to each other, indicating that carpets and dust are major sources of FTOHs in air. Nonetheless, air posed the largest exposure risk of FTOHs and biotransformed perfluorinated alkyl acids (PFAA) in young children. This research highlights inhalation of indoor air as an important exposure pathway and the need for further reduction of precursors to PFAA.

Niche Partitioning between Coastal and Offshore Shelf Waters Results in Differential Expression of Alkane and Polycyclic Aromatic Hydrocarbon Catabolic Pathways.

Marine oil spills can impact both coastal and offshore marine environments, but little information is available on how the microbial response to oil and dispersants might differ between these biomes. Here, we describe the compositional and functional response of microbial communities to different concentrations of oil and chemically dispersed oil in coastal and offshore surface waters from the Texas-Louisiana continental shelf. Using a combination of analytical chemistry and 16S rRNA amplicon and metatranscriptomic sequencing, we provide a broad, comparative overview of the ecological response of hydrocarbon-degrading bacteria and their expression of hydrocarbon-degrading genes in marine surface waters over time between two oceanic biomes. We found evidence for the existence of different ecotypes of several commonly described hydrocarbon-degrading bacterial taxa which behaved differentially in coastal and offshore shelf waters despite being exposed to similar concentrations of oil, dispersants, and nutrients. This resulted in the differential expression of catabolic pathways for n-alkanes and polycyclic aromatic hydrocarbons (PAHs)-the two major categories of compounds found in crude oil-with preferential expression of n-alkane degradation genes in coastal waters while offshore microbial communities trended more toward the expression of PAH degradation genes. This was unexpected as it contrasts with the generally held view that n-alkanes, being more labile, are attacked before the more refractory PAHs. Collectively, our results provide new insights into the existence and potential consequences of niche partitioning of hydrocarbon-degrading taxa between neighboring marine environments.IMPORTANCE In the wake of the Deepwater Horizon oil spill, the taxonomic response of marine microbial communities to oil and dispersants has been extensively studied. However, relatively few studies on the functional response of these microbial communities have been reported, especially in a longitudinal fashion. Moreover, despite the fact that marine oil spills typically impact thousands of square kilometers of both coastal and offshore marine environments, little information is available on how the microbial response to oil and dispersants might differ between these biomes. The results of this study help fill this critical knowledge gap and provide valuable insight into how oil spill response efforts, such as chemically dispersing oil, may have differing effects in neighboring coastal and offshore marine environments.

Mesocosm experiments to better understand hydrocarbon half-lives for oil and oil dispersant mixtures.

Concerns on the timing and processes associated with petroleum degradation were raised after the use of Corexit during the Deepwater Horizon oil spill. There is a lack of understanding of the removal of oil associated with flocculate materials to the sediment. Mesocosm studies employing coastal and open-ocean seawater from the Gulf of Mexico were undertaken to examine changes in oil concentration and composition with time. The water accommodated fractions (WAF) and chemically enhanced WAF (CEWAF) produced using Macondo surrogate oil and Corexit were followed over 3-4 days in controlled environmental conditions. Environmental half-lives of estimated oil equivalents (EOE), polycyclic aromatic hydrocarbons (PAH), n-alkanes (C10-C35), isoprenoids pristane and phytane, and total petroleum hydrocarbons (TPH) were determined. EOE and PAH concentrations decreased exponentially following first-order decay rate kinetics. WAF, CEWAF and DCEWAF (a 10X CEWAF dilution) treatments half-lives ranged from 0.9 to 3.2 days for EOE and 0.5 to 3.3 days for PAH, agreeing with estimates from previous mesocosm and field studies. The aliphatic half-lives for CEWAF and DECWAF treatments ranged from 0.8 to 2.0 days, but no half-life for WAF could be calculated as concentrations were below the detection limits. Biodegradation occurred in all treatments based on the temporal decrease of the nC17/pristane and nC18/phytane ratios. The heterogeneity observed in all treatments was likely due to the hydrophobicity of oil and weathering processes occurring at different rates and times. The presence of dispersant did not dramatically change the half-lives of oil. Comparing degradation of oil alone as well as with dispersant present is critical to determine the fate and transport of these materials in the ocean.

Inter-laboratory calibration of estimated oil equivalent (EOE) concentrations of a water accommodated fraction (WAF) of oil and a chemically enhanced WAF (CEWAF).

Chemical characterization of the presence of oil in environmental samples are performed using methods of varying complexity. Extraction of samples with an organic solvent and analysis by fluorescence spectrometry has been shown to be a rapid and effective screening technique for petroleum in the environment. During experiments, rapid analysis of oil by fluorescence provides the opportunity for researchers to modify the experimental conditions in real time. Estimated Oil Equivalents (EOE) relies on the fluorescence measurement of the aromatic compounds to estimate the oil concentration. The present intercalibration study was designed to investigate whether different fluorometer instruments can reliably measure EOE and whether the results are intercomparable. Additionally, the need for extraction of oil compounds into an organic solvent was investigated. Three different fluorometers were used in three different laboratories: a Horiba Aqualog, a Turner Trilogy and a Shimadzu Spectrofluorophotometer RF-1501. Results from these different instruments showed excellent agreement for EOE determinations. A very high correlation was found between the EOE results obtained with Aqualog Horiba and Turner Trilogy (r2 = 0.9999), with no significant differences between the mean EOE results (t-test, p = 0.30), and the Aqualog Horiba and Shimadzu (r2 = 0.995) fluorometers, with no statistically difference between the EOE results obtained by the two instruments (p = 0.40).

A method for the production of large volumes of WAF and CEWAF for dosing mesocosms to understand marine oil snow formation.

Marine oil snow (MOS) formation is a mechanism to transport oil from the ocean surface to sediments. We describe here the use of 110L mesocosms designed to mimic oceanic parameters during an oil spill including the use of chemical dispersants in order to understand the processes controlling MOS formation. These experiments were not designed to be toxicity tests but rather to illustrate mechanisms. This paper focuses on the development of protocols needed to conduct experiments under environmentally relevant conditions to examine marine snow and MOS. The experiments required the production of over 500 liters of water accommodated fraction (WAF), chemically enhanced water accommodated fraction of oil (CEWAF) as well as diluted CEWAF (DCEWAF). A redesigned baffled (170 L) recirculating tank (BRT) system was used. Two mesocosm experiments (M1 and M2) were run for several days each. In both M1 and M2, marine snow and MOS was formed in controls and all treatments respectively. Estimated oil equivalent (EOE) concentrations of CEWAF were in the high range of concentrations reported during spills and field tests, while WAF and DCEWAF concentrations were within the range of concentrations reported during oil spills. EOE decreased rapidly within days in agreement with historic data and experiments.