Yunping Xu

Sea surface temperature variability in southern Okinawa Trough during last 2700 years

[1]xa0Most of the temperature reconstructions for the past two millennia are based on proxy data from various sites on land. Here we present a bidecadal resolution record of sea surface temperature (SST) in Southern Okinawa Trough for the past ca. 2700xa0years by analyzing tetraether lipids of planktonic archaea in the ODP Hole 1202B, a site under the strong influence of Kuroshio Current and East Asian monsoon. The reconstructed SST anomalies generally coincided with previously reported late Holocene climate events, including the Roman Warm Period, Sui-Tang dynasty Warm Period, Medieval Warm Period, Current Warm Period, Dark Age Cold Period and Little Ice Age. However, the Medieval Warm Period usually thought to be a historical analogue for the Current Warm Period has a mean SST of 0.6–0.8°C lower than that of the Roman Warm Period and Sui-Tang dynasty Warm Period. Despite an increase since 1850xa0AD, the mean SST in the 20th century is still within the range of natural variability during the past 2700xa0years. A close correlation of SST in Southern Okinawa Trough with air temperature in East China, intensity of East Asian monsoon and the El-Nino Southern Oscillation index has been attributed to the fluctuations in solar output and oceanic-atmospheric circulation.

Spatial and temporal variability of polycyclic aromatic hydrocarbons in sediments from yellow river-dominated margin.

Polycyclic aromatic hydrocarbons (PAHs) were analyzed for surface sediments and a sediment core from the Yellow River-dominated margin. The concentration of 16 USEPA priority PAHs in surface sediments ranged from 5.6 to 175.4u2009ngu2009g−1 dry weight sediment (dws) with a mean of 49.1u2009ngu2009g−1u2009dws. From 1930 to 2011, the distribution of PAHs (37.2 to 210.6u2009ngu2009g−1u2009dws) was consistent with the socioeconomic development of China. The PAHs concentration peaked in 1964 and 1986, corresponding to the rapid economic growth in China (1958–1965) and the initiation of the “Reform and Open” policy in 1978, respectively. The applications of molecular diagnostic ratios and principal component analysis suggest that PAHs are predominantly produced by the coal and biomass combustion, whereas the contribution of petroleum combustions slightly increased after the 1970s, synchronous with an increasing usage of oil and gas in China.

Optimization of programmed‐temperature vaporization injection preparative capillary GC for compound specific radiocarbon analysis

Preparative capillary GC (PCGC) is a powerful tool for the separation and purification of compounds from any complex matrix, which can be used for compound-specific radiocarbon analysis. However, the effect of PCGC parameters on the trapping efficiency is not well understood. Here, we present a comprehensive study on the optimization of parameters based on 11 reference compounds with different physicochemical properties. Under the optimum conditions, the trapping efficiencies of these 11 compounds (including high-boiling-point n-hentriacontane and methyl lignocerate) are about 80% (60-89%). The isolation of target compounds from standard solutions, plant and soil samples demonstrates that our optimized method is applicable for different classes of compounds including n-alkanes, fatty acid esters, long-chain fatty alcohol esters, polycyclic aromatic hydrocarbons (PAHs) and steranes. By injecting 25 μL in large volume injection mode, over 100 μg, high purity (>90%) target compounds are harvested within 24 h. The recovery ranges of two real samples are about 70% (59.9-83.8%) and about 83% (77.2-88.5%), respectively. Compared to previous studies, our study makes significant improvement in the recovery of PCGC, which is important for its wide application in biogeochemistry, environmental sciences, and archaeology.