Xiao Huayun

Vertical variation of phosphorus forms in surface sediments from Wuli Bay,Taihu Lake,China

In order to investigate the cycling of phosphorus in the Taihu Lake, a sequential extraction technique was used to separate different phosphorus forms in surficial sediments from the Wuli Bay of the Taihu Lake. The concentrations of total P are high in the sediments, with an average of 2. 80 mg g-1, and a variation range between 4. 02 and 2. 05 mg g-1. Total P is composed mainly of inorganic P (70%–90%), a large portion (75%–85% ) of which lies in the CDB-extractable iron oxide phase. The low Fe/P atomic ratios (2.0–5.3) indicate that the Fe compounds extracted with CDB have a lower proportion of relatively crystalline phases in all samples, and that the absorption between iron and phosphorus has probably reached certain equilibrium. Organic C/N atomic ratios (8.8–10. 6) for most of the samples are lower, which suggests a lacustrine authigenic source of organic matter in the sediments. Moreover, organic C/P atomic ratios (135–320) are usually higher than the Redfield ratio (106 : 1), showing that the organic phosphorus had been preferentially released via organic matter degradation during the early diagenesis process.

Situation of sewage input reflected by nitrogen isotopic composition in a sediment core of Hongfeng Lake

Nitrogen in Hongfeng South Lake water mainly comes from sewage with high N concentrations from Pingba Chemical Fertilizer Plant (PCFP). Studies on the sediment core HF010427 sampled in the lake showed that the upward increase of nitrogen isotopic composition of sedimentary organic nitrogen (δ15Norg) accorded with the trend of industrial total production (TP) of PCFC. On the contrary, diagenesis will theoretically cause an upward decrease of δ15Norg. Because no treatment of sewage water was carried out, TP corresponds with sewage emission, indicating that sedimentary δ15Norg can reflect well the total trend of sewage input. The very similar profile shape between nitrogen isotopic composition of sedimentary absorbed ammonium (δ15NH4 absorbed+) and TP of PCFP suggests that δ15NH4 absorbed+ can be used to reconstruct more detailed situation of sewage input. The study has a reference to history investigation of sewage input.

Geochemistry of main types of gold deposits in shear zones, China

Shear zone-hosted gold deposits in China can be divided into four types: ductile, brittle-ductile, ductile-brittle and brittle, of which the ductile and brittle types are the basic ones. All these types of gold deposits have their own geochemical characteristics. The Hetai gold deposit in Guangdong Province, for example, is a mylonite-type gold deposit in a ductile shear zone. With increasing mylonitization, obvious changes took place in trace elements in minerals and rocks, enriching gold and mineralizing elements. The S and Pb isotope data indicated that the ore-forming materials were derived from the strata. Hydrogen and oxygen isotopic and fluid inclusion studies also implied that the ore-forming fluid was much closer to meteoric water from the early to the late ore-forming stage. The Linglong gold deposit, Shangdong Province, is a quartz-type gold deposit in a brittle shear zone. Changes in rocks, minerals and trace elements occurred in the process of formation of gold quartz veins, and the analytical results of S, Pb, H and O isotopes showed that ore deposition is connected not only with the Jiaodong Group, but also with anatexic granites.