Concentrations and sources of polycyclic aromatic hydrocarbons in surface coastal sediments of the northern Gulf of Mexico

Zucheng Wang is with the Department of Geography, Northeast Normal University, Changchun, China. -- Zucheng Wang and Zhanfei Liu are with the Marine Science Institute, The University of Texas at Austin, Port Aransas, TX, USA. -- Kehui Xu is with the Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, LA, USA – and – the Coastal Studies Institute, Louisiana State University, Baton Rouge, LA, USA. -- Lawrence M Mayer is with the School of Marine Sciences, University of Maine, Walpole, ME, USA. -- Zulin Zhang is with The James Hutton Institute, Aberdeen, UK. -- Alexander S. Kolker is with Louisiana Universities Marine Consortium, Chauvin, LA, USA. -- Wei Wu is with the Department of Coastal Sciences, Gulf Coast Research Laboratory, The University of Southern Mississippi, Ocean Springs, MS, USA.Background: Coastal sediments in the northern Gulf of Mexico have a high potential of being contaminated by petroleum hydrocarbons, such as polycyclic aromatic hydrocarbons (PAHs), due to extensive petroleum exploration and transportation activities. In this study we evaluated the spatial distribution and contamination sources of PAHs, as well as the bioavailable fraction in the bulk PAH pool, in surface marsh and shelf sediments (top 5 cm) of the northern Gulf of Mexico. Results: PAH concentrations in this region ranged from 100 to 856 ng g−1, with the highest concentrations in Mississippi River mouth sediments followed by marsh sediments and then the lowest concentrations in shelf sediments. The PAH concentrations correlated positively with atomic C/N ratios of sedimentary organic matter (OM), suggesting that terrestrial OM preferentially sorbs PAHs relative to marine OM. PAHs with 2 rings were more abundant than those with 5–6 rings in continental shelf sediments, while the opposite was found in marsh sediments. This distribution pattern suggests different contamination sources between shelf and marsh sediments. Based on diagnostic ratios of PAH isomers and principal component analysis, shelf sediment PAHs were petrogenic and those from marsh sediments were pyrogenic. The proportions of bioavailable PAHs in total PAHs were low, ranging from 0.02% to 0.06%, with higher fractions found in marsh than shelf sediments. Conclusion: PAH distribution and composition differences between marsh and shelf sediments were influenced by grain size, contamination sources, and the types of organic matter associated with PAHs. Concentrations of PAHs in the study area were below effects low-range, suggesting a low risk to organisms and limited transfer of PAHs into food web. From the source analysis, PAHs in shelf sediments mainly originated from direct petroleum contamination, while those in marsh sediments were from combustion of fossil fuels.Marine [email protected]

Investigation of Electron-Phonon Coupling in Epitaxial Silicene by In-situ Raman Spectroscopy

In this letter, we report that the special coupling between Dirac fermion and lattice vibrations, in other words, electron-phonon coupling (EPC), in silicene layers on Ag(111) surface was probed by an in-situ Raman spectroscopy. We find the EPC is significantly modulated due to tensile strain, which results from the lattice mismatch between silicene and the substrate, and the charge doping from the substrate. The special phonon modes corresponding to two-dimensional electron gas scattering at edge sites in the silicene were identified. Detecting relationship between EPC and Dirac fermion through the Raman scattering will provide a direct route to investigate the exotic property in buckled two-dimensional honeycomb materials.Comment: 15 pages, 4 figure

Exploring the Balance Between Urban and Ecology Based on Fractal City Theory——Taking the Northern Metropolis of Hong Kong as an Example

As the times progressed, the large countryside-dominated area to the north of Hong Kong, adjacent to Shenzhen, needed further development. This research is based on fractal urbanism and horizontal urbanism and attempts to explore a new urban development model from the perspective of balancing urban and countryside areas. At present, there is a contradiction between ecological conservation and urban development in the area. Recent urbanization has resulted in habitat fragmentation, which has led to a significant decline in biodiversity, a lack of natural green space within the city, and low environmental quality, etc. To improve the above urban problems, we propose an evaluation method that divides the greening rate within the scope of human activities into five grades. And put forward a greening promotion method. Taking the Deep bay area in North New Territories of Hong Kong as an example, an ideal solution is proposed

An alternative flow cytometry strategy for peripheral blood dendritic cell enumeration in the setting of repetitive GM-CSF dosing

BACKGROUND: Enumeration of circulating peripheral blood dendritic cells (DCs) is complicated by the absence of a unique cell surface marker expressed on all DC subsets and by the use of various biological adjuvants to modulate the DC compartment, including granulocyte macrophage colony stimulating factor (GM-CSF). Common methods employ a cocktail of antibodies, typically including anti-CD14, to define a lineage negative, MHC class II positive, putative DC population. Reported flow cytometry protocols include highly variable gating strategies and DC identification criteria. Increasing appreciation of DC pleiomorphism, GM-CSF biology, and recognition of CD14 expression in some DC subsets led us to consider an alternative lineage cocktail to improve identification of the circulating DC pool. METHODS: Standard whole blood staining with appropriate fluorochrome conjugated antibodies to MHC class II and either standard CD14 containing, or an alternate CD66acde containing, lineage cocktail was performed on samples obtained from normal donors and breast cancer patients before and after administration of dose-dense, cytotoxic chemotherapy with daily GM-CSF hematopoetic growth factor support. Putative DCs were enumerated by standard flow cytometry. Data set differences were evaluated using two tailed Mann-Whitney or Wilcoxon signed rank tests. Cellular morphology was examined in cell-sorted populations from post GM-CSF samples. RESULTS: Use of either antibody cocktail defined comparably sized lineage negative, MHC class II positive populations in normal donors and at baseline in cancer patients. However, selection of lineage negative subsets with increasing MHC class II expression levels yielded larger putative DC populations identified with the alternate cocktail. Both cocktails yielded highly reproducible data. Use of the alternate cocktail: 1) yielded a putative DC population, post GM-CSF that was more homogenous and consistent with DCs, 2) resulted in less data variation across gating strategies, and 3) resulted in more uniform and concordant longitudinal data, consistent with established GM-CSF biological activity. CONCLUSION: An alternative lineage negative cocktail substituting anti-CD66 antibody for anti-CD14 is a viable option for enumerating the circulating DC population, potentially more accurately defining the circulating DC pool by including CD14 positive immature DCs, and thus, may give more reliable data, particularly in the setting of sustained GM-CSF administration

Variability of Gene Expression After Polyhaploidization in Wheat (Triticum aestivum L.)

Interspecific hybridization has a much greater effect than chromosome doubling on gene expression; however, the associations between homeologous gene expression changes and polyhaploidization had rarely been addressed. In this study, cDNA–single strand conformation polymorphism analysis was applied to measure the expression of 30 homeologous transcripts in naturally occurring haploid (ABD, 2n = 21) and its polyploid maternal parent Yumai 21A (AABBDD, 2n = 42) in wheat. Only one gene (TC251989) showed preferentially silenced homoeoalleles in haploids. Further analyses of 24 single-copy genes known to be silenced in the root and/or leaf also found no evidence of homeologous silencing in 1-month-old haploids and two ESTs (BF484100 and BF473379) exhibit different expression patterns between 4-month-old haploids and hexaploids. Global analysis of the gene expression patterns using the Affymetrix GeneChip showed that of the 55,052 genes probed, only about 0.11% in the shoots and 0.25% in the roots were activated by polyhaploidization. The results demonstrate that activation and silencing of homoeoalleles were not widespread in haploid seedlings