Source apportionment of polycyclic aromatic hydrocarbons (PAHs) into Central Park Lake, New York City, over a century of deposition.

Relative contributions of polycyclic aromatic hydrocarbons (PAHs) from combustion sources of wood, petroleum, and coal were computed in sediments from Central Park Lake in New York City (NY, USA) by chemical mass balance based on several reliable source indicators. These indicators are the ratio of retene to the sum of retene and chrysene, the ratio of 1,7-dimethylphenanthrene (DMP) to 1,7-DMP and 2,6-DMP, and the ratio of fluroanthene to fluroanthene and pyrene. The authors found that petroleum combustion-derived PAH fluxes generally followed the historical consumption data of New York State. Coal combustion-derived PAH flux peaked approximately in the late 1910s, remained at a relatively high level over the next 3 decades, then rapidly declined from the 1950s to the 1960s; according to historical New York State coal consumption data, however, there was a 2-peak trend, with peaks around the early 1920s and the mid-1940s. The 1940s peak was not observed in Central Park Lake, most likely because of the well-documented shift from coal to oil as the major residential heating fuel in New York City during the late 1930s. It was widely believed that the decreased PAH concentrations and fluxes in global sediments during the last century resulted from a major energy shift from coal to petroleum. The data, however, show that this shift occurred from 1945 through the 1960s and did not result in an obvious decline. The sharpest decrease, which occurred in the 1970s was not predominantly related to coal usage but rather was the result of multiple factors, including a decline in petroleum usage largely, the introduction of low sulfur-content fuel in New York City, and the introduction of emission-control technologies.

Archaeal and bacterial diversity in acidic to circumneutral hot springs in the Philippines.

The microbial diversity was investigated in sediments of six acidic to circumneutral hot springs (Temperature: 60-92 °C, pH 3.72-6.58) in the Philippines using an integrated approach that included geochemistry and 16S rRNA gene pyrosequencing. Both bacterial and archaeal abundances were lower in high-temperature springs than in moderate-temperature ones. Overall, the archaeal community consisted of sequence reads that exhibited a high similarity (nucleotide identity > 92%) to phyla Crenarchaeota, Euryarchaeota, and unclassified Archaea. The bacterial community was composed of sequence reads moderately related (nucleotide identity > 90%) to 17 phyla, with Aquificae and Firmicutes being dominant. These phylogenetic groups were correlated with environmental conditions such as temperature, dissolved sulfate and calcium concentrations in spring water, and sediment properties including total nitrogen, pyrite, and elemental sulfur. Based on the phylogenetic inference, sulfur metabolisms appear to be key physiological functions in these hot springs. Sulfobacillus (within phylum Firmicutes) along with members within Sulfolobales were abundant in two high-temperature springs (> 76 °C), and they were hypothesized to play an important role in regulating the sulfur cycling under high-temperature conditions. The results of this study improve our understanding of microbial diversity and community composition in acidic to circumneutral terrestrial hot springs and their relationships with geochemical conditions.

Development of a surface-enhanced Raman technique for biomarker studies on Mars.

Raman spectroscopy has been identified as a potentially useful tool to collect evidence of past or present life on extraterrestrial bodies. However, it is limited by its inherently low signal strength. In this investigation, laboratory tests were conducted using surface-enhanced Raman spectroscopy (SERS) in an "inverted" mode to detect the presence of organic compounds that may be similar to possible biomarkers present on Mars. SERS was used to overcome the inherently low signal intensity of Raman spectroscopy and was an effective method for detecting small concentrations of organic compounds on a number of surfaces. For small organic molecules, dissolution of the molecule to be analyzed in a suitable solvent and depositing it on a prepared SERS substrate for analysis is possible. However, for larger molecules, an "inverted" SERS (iSERS) technique was shown to be effective. In iSERS, nanoparticles of silver or gold were deposited on the mineral substrate/organic compound to be analyzed. Benzotriazole, benzoic acid, and phthalic acid were used as test organic analogs and the iSERS technique was able to detect femtomole levels of the analytes. The interference from various mineral substrates was also examined. Different methods of depositing silver particles were evaluated, including ion beam-assisted vapor deposition and deposition from aqueous colloidal suspensions.

Molecular tracers of saturated and polycyclic aromatic hydrocarbon inputs into Central Park Lake, New York City.

Saturated hydrocarbons (SH) and polycyclic aromatic hydrocarbons (PAHs) have been quantified in a sediment core obtained from Central Park Lake, New York City. Radionuclides 210Pb and 137Cs were used to assign approximate dates to each individual section in the core. The dating profile based on 210Pb matches very well with the time constraints provided by 137Cs. Radionuclide-derived depositional dates are consistent with temporal information from the petroleum-indicator ratio U/R [the ratio of unresolved complex mixture (UCM)to saturated hydrocarbons in the aliphatic fraction] and the history of fuel use in the NYC area. Ratios of 1,7-dimethylphenanthrane (DMP) to 1,7-DMP plus 2,6-DMP [1,7/(1,7 + 2,6)-DMP], retene to retene plus chrysene [Ret/(Ret + Chy)], and fluoranthene to fluoranthene plus pyrene [FI/(FI + Py)] provide additional source discrimination throughoutthe core. Results show that the ratio U/R is sensitive to petroleum inputs and Ret/(Ret + Chy) is responsive to contributions from softwood combustion, whereas both FI/(FI + Py) and 1,7/ (1,7 + 2,6)-DMP can be used to discriminate among wood, coal, and petroleum combustion sources. Combined use of these ratios suggests that in New York City, wood combustion dominated 100 years ago, with a shift to coal combustion occurring from the 1900s to the 1950s. Petroleum use began around the 1920s and has dominated since the 1940s.