[Roles of moisture in constructing man-made algal crust with Micocoleus vaginatus].

To explore the roles of moisture in the construction of man-made algal crust with inoculated Micocoleus vaginatus, a laboratory experiment was conducted to study the variations of the microalgal biomass, algal crust thickness, crust compressive strength, and crust microstructure under six moisture doses and four moisture treatment intervals. When M. vaginatus was inoculated to the naked sands without moisture addition, the microalgal biomass was very low, and no algal crust was formed. With increasing dose of moisture, the microalgal biomass, algal crust thickness, and crust compressive strength increased significantly, and the algal filaments and extracellulhr polysaccharides (EPS) had a gradual increase, wrapped around the sands and formed a complex network. After 15 days moisture treatment, stable algal crust was formed, which had the highest microalgal biomass, crust thickness, and crust compressive strength. The optimal moisture dose for M. vaginatus to form man-made algal crust was 3-4 L.m-2.d-1, and the addition of moisture should be continued for 15 d. The availability of the moisture promoted the metabolic processes of M. vaginatus and the synthesis of the algal EPS, which increased the microalgal biomass and its ability to resist desiccation. The moisture availability at early stage was the key factor for M. vaginatus to successfully form algal crust. This study could offer some guidance for the recovery of biological soil crusts in the field.

[Detection of the metabolites of dehydroepiandrosterone in urine with gas chromatography-combustion-isotope ratio mass spectrometry].

AIM: To establish a method to determine the isotope ratios of 13C to 12C of dehydroepiandrosterone and its metabolites in urine, for detecting the source of dehydroepiandrosterone or its metabolites. METHODS: Preliminary separation of endogenous anabolic androgenic steroids could be achieved using solid phase extraction, enzymolysis and thin layer chromatography. The source of dehydroepiandrosterone and other endogenous anabolic androgenic steroids could be detected by their delta values with gas chromat ography-combustion-isotope ratio mass spectrometry. RESULTS: The 5 values of some metabolites of dehydroepiandrosterone reduced after the administration of dehydroepiandrosterone preparation. In these cases the data indicated that exogenous anabolic androgenic steroids were administrated. CONCLUSION: The source of dehydroepiandrosterone or its metabolites in urine could be detected by measuring their delta values with this method.