Chemical Forms And Pollution Characteristics Of Nitrogen And Phosphorus In The Urban Dusts Of Hefei City

Nitrogen and phosphorus in the urban dusts of Hefei City was studied in this paper,what were collected from52sampling points in6types of land. Four aspects werediscussed based on the experimental test of different forms of nitrogen andphosphorus, including spatial distribution characteristics, correlation analysis,bioavailability content and sorption/desorption characteristics. The main researchcontents and results were summed up as follows:(1) Total nitrogen and total phosphorus were mainly existed in the forms oforganic nitrogen and inorganic phosphorus in the urban dust. Ammonia nitrogenwas the dominant forms among inorganic nitrogen, while inorganic phosphorus waschiefly consisted of calcium-phosphorus. To predict the spatial distributioncharacteristics of nitrogen, phosphorus and total organic carbon by means ofkriging spatial interpolation technique based on the ArcGIS software. The resultsshowed that the contents of TN decreased gradually from the north to the south,while the high contents of TP and TOC were mainly concentrated in thenortheastern and the north of Hefei city. The distribution characteristics analysis ofdifferent functional areas indicated that the highest contents of the nitrogennutrients located in the commercial area, followed by green parks, and the lowestcontent was in the industrial area; the highest content of TOC located in the culturaldistrict; but the functional distribution characteristics of different forms ofphosphorus were relatively complex.(2) Multivariate statistical analysis indicated that the nitrogen nutrients andphosphorus nutrients were mainly contributed by organic nitrogen andcalcium-phosphorus, followed by ammonium nitrogen and detritus-phosphorus, andthese indexes related significantly. Moreover, the entering of TOC could influencethe loading distribution of nitrogen and phosphorus in the urban dust. TheClustering results of all the indexes were consistent with the spatial interpolationdistribution consequence. Comprehensive analysis can be inferred that nitrogenpollutions mainly came from life pollutions and the fertilization of green parks;phosphorus pollutions mainly came from the building materials of urbanconstruction. (3) In the urban dust of Hefei city, bioavailability nitrogen and phosphoruswhat were chiefly consisted of ammonium nitrogen and exchanged-phosphorusrespectively occupied8.19%and11.90%of the total nitrogen and phosphorus pool.The content of potential bioavailability phosphorus dominated bycalcium-phosphorus was5.7times to the bioavailability phosphorus. Thedistribution characteristics analysis of different functional areas indicated that themaximum mass fraction of bioavailability nitrogen and phosphorus were both in thecommercial area, while the minimum were respectively in the residential areas andindustrial areas.(4) Sorption kinetics studies of ammonium nitrogen in the urban dust hadshown that the progress was characterized by desorption first what was the mainfeature, then changed to sorption, and almost achieved the balance after24hours.Between different particle sizes of urban dust, the maximum desorption amount ofphosphorus appeared in the first4hours, but the maximum sorption amount ofphosphorus appeared after48hours. The sorption capacity of phosphorus presenteda fluctuated improving trend except commercial area. Adsorption thermodynamicsstudies of ammonium nitrogen and phosphorus had shown that linear isothermfitted the sorption progress well. The sorption capacity increases with solutionconcentration in a same trend. Generally, the greater the particle sizes of urban dust,the balance time longer, and the linear fitting effect poorer.