[Total contents of heavy metals and their chemical fractionation in agricultural soils at different locations of Beijing City].

In this study, 23 groups of suited typical soil-wheat grain samples were collected from different locations of Beijing city (central city, suburban plain and exurban plain), the accumulation, chemical forms and bioavailability of heavy metals in arable soils under different human activity intensity were analyzed, and their source identifications and health risk were discussed. The results showed that (1) Urban soils exhibited Pb contamination with an average concentration (35.59 mg x kg(-1)) above the WHO limit, probably due to the emission of traffic activities and industrial processes.

[Denitrifying bacteria isolated from river sediment and its nitrogen and phosphorus removal capacity from river water].

20 strains of bacteria were isolated from river sediment using enrichment culture medium for denitrification, and the denitrification intensity was determined. F10, one of bacteria strain, was identified having the highest denitrifying intensity, and further used to test its role in the removing of nitrogen and phosphorus from wastewater in laboratory. By checking the individual morphology, colony culture characteristics, DNA sequencing and 16S rDNA gene bank, F10 was identified as Alcaligenes faecalis, and its denitrifying intensity was 63.