Accumulation and phytoavailability of hexachlorocyclohexane isomers and cadmium in Allium sativum L. under the stress of hexachlorocyclohexane and cadmium.

The effects of Cd and HCHs with single and combined forms on Cd and HCHs phytoavailability of Allium sativum L. were investigated. The results indicated that the coexistence of Cd and HCHs presented antagonistic interactions mostly, which might be partly due to the formation of Cd-HCHs complex, compared with single stress. The bioaccumulation of Cd and HCHs in plants depended largely on their concentrations applied in pot soils, and the phytoavailability of HCH isomers was in the sequence: δ- > γ- ≥ ß- > α-HCH.

[Research on the isolation of denitrifying bacteria from domestic wastewater and its capability of removing nutrient salt from eutrophic water body].

OBJECTIVE: A kind of bacteria associated with highly denitrifying capability was isolated, and investigated about its growth and degradation characteristics. METHODS: By using an enrichment culture and plate dilution method, one strain of bacteria was isolated from domestic wastewater and their denitrifying capability on the river water received domestic wastewater was determined. RESULTS: The isolated bacteria strain had some nitrogen and phosphorous removal ability, its denitrifying intensity was 63.2%. The efficiencies of removing TN (total nitrogen) and TP (total phosphorus) (76.2% and 93.8%, respectively) were the highest when the consortium was added at the dosing amount of 100 mg/L after treatment for 10 days. CONCLUSIONS: One strain of denitrifying bacteria was successfully isolated from sewage sediments; its removal capacity of nitrogen and phosphorus from eutrophic water was good, which provided a basic biological method for nitrogen and phosphorus removal associated with eutrophic sewage treatment.

[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. In addition, long-term sewage irrigation and other agricultural activities led to local metal contamination in the suburban agricultural soils. (2) Cu, Zn and Pb were predominantly associated with the residual (35%-75%) and organic (23%-53%) fractions, followed by Fe/Mn oxide (1%-19%), and very small proportion of carbonate (n. d.-5%) and exchangeable (n. d.-2%) fraction. Furthermore, compared with the suburban agricultural soils, Pb, Zn and Cu in the urban agricultural soils showed higher mobility, whereas the exurban agricultural soils presented the lowest mobility. For Cd, the order was contrary. Besides, Cd showed the highest bioavailability among the four metals in suburban and exurban arable soils due to its considerable proportion of exchangeable (13% -31%) and carbonate fractions (11%-27%). (3) Cd and Zn contents in wheat grains were largely dependent on the Fe/Mn ox. fractions in the studied soils (P < 0.05, r were 0.43-0.7). (4) Pb and Zn concentrations in wheat grains in some of the urban and suburban agricultural soils were above the standard limit, which might bring potential risk for the health of the local residents.

[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 63.2%. The highest removal of TN (76.2%) and TP (93.8%) were observed in a 10 days period with an addition of F10 at a rate of 100 mg/L.