Distribution and bioavailability of nitrogen and phosphorus species in the urban dusts from Hefei City

To find out the distribution and bioavailability of nitrogen(N) and phosphorus(P) species in the urban dusts of Hefei City,52 samples were collected from impervious areas with six different urban land-use types.The contents of ammonia nitrogen(NH+4-N),nitrate nitrogen(NO-3-N),exchangeable P(Ex-P),Al-bound P(Al-P),Fe-bound P(Fe-P),occluded P(Oc-P),Ca-bound P(Ca-P),detrital apatite P(De-P),organic P(Or-P) as well as total nitrogen(TN) and total phosphorus(TP) were measured by sequential extraction methods.The studies on spatial distribution,correlation and bioavailability of nitrogen and phosphorus species were made according to the analyzed data.The results show that the TN is composed mainly of organic nitrogen(Or-N) while the TP consists chiefly of inorganic phosphorus(IP) in the urban dusts of Hefei City,and the spatial variability of nitrogen and phosphorus species contents are greatly affected by the mode of urban land-use type.In addition,there are significant correlations among partial nitrogen and phosphorus forms in dusts.Corresponding to different urban land-use types such as industrial area,commercial area,residential area,educational area,traffic area and public landscapes and city squares,the average ratios of bioavailable nitrogen content(the sum of NH+4-N and NO-3-N) to TN are 8.87%,9.60%,6.68%,9.37%,8.20% and 8.17%,respectively,while the mean ratios of bioavailable phosphorus content(the sum of Ex-P,Al-P and Fe-P) to TP,are equal to 6.70%,18.19%,10.10%,9.69%,10.64% and 14.03%,respectively.