[Sedimentary Characteristics and Sources of Organic Matter in Sediments of Dianchi Lake].

Sediment columns in the southeast and east of Dianchi Lake were taken as the object of the study to determine ages by 210 Pb dating method.The contents and sediment fluxes of total organic carbon (TOC) and n-alkanes of the sediments were investigated,and organic sources were tracked according to the relevant indexes of n-alkanes.The results indicated that TOC contents and sediment fluxes of two sampling sediments both presented an increasing trend on the whole;Sediment fluxes of n-alkanes varied as three stages:increasing period,decreasing period and re-increasing period.When the sediment fluxes of n-alkanes and TOC both went up,it showed that they had the same sources:sediments in the lake and carried by the rivers;From 1980s to the end of 20th century,sediment fluxes of n-alkanes were going down while those of TOC were going up.This result means there was a big difference in the sources of n-alkanes and TOC.The bacteria and algae in the lake made a great contribution to n-alkanes while TOC was mainly influenced by sediments in the lake and carried by the rivers.n-alkanes of the two sampling sites both ranged from C12 to C35.Based on the basic features and relevant indexes of n-alkanes,we proposed that emergent plants made big contributions to the sources of organic matter in the sediments of Dianchi Lake,simultaneously,bacteria and algae had significant contributions to the sources of organic matter in shallow depth of Dianchi Lake.

[Distribution Characteristics of n-alkanes in Sediment Core and Implication of Environment in Different Lakes of Dianchi].

In order to study the composition and environment significance of the organic matter in Lake Dianchi, samples from two sediment cores from the northern and southern parts of the lake were collected in July, 2014. Meanwhile, the vertical distributions of total organiccarbon (TOC), total nitrogen (TN), n-alkanes fractions were investigated. The results showed that ① the concentrations of TOC and TN had been clearly increasing since the 1970s, which implied that the primary productivity of Lake Dianchi was continuously enhanced; ② The values of the parameter n-C27/n-C31, Paqand CPI indicated the alternation between herbs and woody plants from the bottom up in Lake Dianchi sediments. Besides, the high carbon number of organic matter in sediments mainly originated from endogenous submerged floating and large plants; ③ The index of C/N and distribution characteristics of n-alkanes suggested differences in the various sources of organic matter in different lakes. In detail, organic matter came from terrigenous organic matter of anthropogenic sources and endogenous bacteria in the sediments of northern Dianchi, while organic matter was derived from endogenous aquatic and terrestrial higher plants mixed source in the sediments of southern Dianchi. Finally, it is worthwhile to emphasize further research on organic matter in different lakes of Lake Dianchi.

Origin and Quenching of Novel ultraviolet and blue emission in NdGaO3: Concept of Super-Hydrogenic Dopants.

In this study we report the existence of novel ultraviolet (UV) and blue emission in rare-earth based perovskite NdGaO3 (NGO) and the systematic quench of the NGO photoluminescence (PL) by Ce doping. Study of room temperature PL was performed in both single-crystal and polycrystalline NGO (substrates and pellets) respectively. Several NGO pellets were prepared with varying Ce concentration and their room temperature PL was studied using 325 nm laser. It was found that the PL intensity shows a systematic quench with increasing Ce concentration. XPS measurements indicated that nearly 50% of Ce atoms are in the 4+ state. The PL quench was attributed to the novel concept of super hydrogenic dopant (SHD)", where each Ce4+ ion contributes an electron which forms a super hydrogenic atom with an enhanced Bohr radius, due to the large dielectric constant of the host. Based on the critical Ce concentration for complete quenching this SHD radius was estimated to be within a range of 0.85 nm and 1.15 nm whereas the predicted theoretical value of SHD radius for NdGaO3 is ~1.01 nm.