Petroleum exploitation enriches the sulfonamide resistance gene sul2 in off shore sediments

Antibiotic resistance genes(ARGs)have been considered as emerging contaminants in nature owing to their wide distribution and human health risk.Anthropogenic activities can increase the diversity and abundance of ARGs and promote their spread in environment.Offshore environment is affected by multiple types of anthropogenic activities,of which excessive accumulation of petroleum substances poses a serious threat.Our previous experimental study has demonstrated that petroleum can increase the abundance of sulfonamide resistance genes(SRGs)in the seawater through horizontal gene transfer.However,the influence of petroleum substances on SRGs in offshore environment,especially adjacent the petroleum exploitation platform,is still unclear.Therefore,the effect of offshore oil exploitation on SRGs was investigated in the surface sediments collected from the Liaodong Bay,north China.The genes of sul1 and sul2 were present in all of the collected samples,while the sul3 gene was not detected in any sediments.The absolute abundance of sul2 gene in each sample was higher than sul1 gene.Class 1 integrons enhanced the maintenance and propagation of sul1 gene but not sul2 gene.More importantly,the results indicate that the absolute abundance of sul2 gene present in the offshore sediments that affected by petroleum exploitation was significantly higher than those in control.These findings provided direct evidence that offshore oil exploitation can influence the propagation of SRGs and implied that a more comprehensive risk assessment of petroleum substances to public health risks should be conducted.

Quantification,morphology and source of humic acid,kerogen and black carbon in offshore marine sediments from Xiamen Gulf,China

Three types of macromolecular organic matters （MOMs）, i.e. humic acid （HA）, kerogen＋black carbon （KB）, and black carbon （BC） were extracted from marine sediments of Xiamen Gulf, southeast of China. The chemical composition, morphological property and source of the three extractions were characterized by elemental analyzer/isotope ratio mass spectrometry （EA/IRMS） and scanning electron microscope （SEM）. The results showed that KB was the predominant fraction in MOMs, which accounted for 61.79%-89.15% of the total organic content （TOC）, while HA consisted less than 5%. The relative high contents of kerogen and BC, and low contents of HA in the samples indicated that anthropogenic input might be the major source of organic matter in marine sediments near the industrial regions. The characterization of SEM, not only revealed morphological properties of the three fractions, but also allowed a better understanding of the source of MOMs. The δ 13 C values of the three fractions suggested that materials from terrestrial C 3 plants were predominant. Furthermore, the anthropogenic activities, such as the discharge of sewage, coal and biomass combustion from industry nearby and agricultural practices within drainage basin of the Jiulong River, were remarkably contributed to the variations in δ 13 C values of MOMs in the offshore marine sediments.

Scour depth beneath a pipeline undergoing forced vibration

This paper studies the coupling effect of the pipeline vibration on the seabed scour. A vertical two- dimensional model is applied to numerically investigate the local scour below a vibrating pipeline with different amplitudes and periods. Using the scour underneath a fixed pipeline as a reference, this paper focuses on the impact of the pipeline vibration on the equilibrium scour depth. Generic relationships are established between the non-dimensional scour depth and the non-dimensional vibrating parameters, i.e., amplitude and frequency. The normalization process takes into account the influences of such parameters as the incoming flow velocity, pipe diameter, and Shields parameter. An empirical formula is proposed to quantify these relationships.