The non-point source pollution is not easy to be controlled, and it is one of the important environmental problems facing the world. Taking Hohhot, a typical city in the arid semi-arid region in China, as an example, four monitoring sites in the city were selected, water samples from six rainfall events were collected, and pollutants such as heavy metals, ammonia, nitrate nitrogen, phosphorus and suspended matter were examined, and the water quality of the rain runoff was comprehensively evaluated by the principal component analysis and the correlation analysis. The results showed that the total phosphorus contents of monitoring points in the street were the largest and those of monitoring points in gas stations were the smallest in rainfall runoff. Arsenic, cobalt, and chromium were less than the Class I standard for environmental quality standards for surface water according to Chinese standard (GB 3838-2002). Concentrations of cadmium, copper, and iron were greatest in street monitoring sites, while nickel, lead, and zinc were greatest in roof monitoring sites, and manganese was greatest in car park monitoring sites. There was minimal contamination at gas station monitoring sites and the greatest contamination at street monitoring sites. Heavy metals and phosphorus were the main contributing factors to pollution at street monitoring sites, while the main contributing factors at gas station monitoring sites were total suspended substances.
Ammonia nitrogen is one of the important pollutants in urban rainfall. Though iron ions and aluminum ions as a filler for plant retention system have a good effect on the removal of ammonia nitrogen, their adsorption characteristics was rarely studied. This paper uses different media (sand, iron powder, aluminum powder) with different pH values and ionic strengths in the Bioretention system to study the adsorption mechanism of ammonia nitrogen in an artificial rainwater. The result shows that Langmuir isothermal adsorption model is more in line with the ammonia nitrogen adsorption process, and the sand has the best adsorption capacity among three samples. Effect of pH values on adsorption kinetics is also studied.
Bioretentions can remarkably improve the rainwater quality. Though iron and aluminum as fillers in bioretentions can remove nitrate nitrogen, its adsorption mechanism is not clear yet and was rarely studied. This paper takes sand, iron powder and aluminum powder as the research objects to study the adsorption characteristics of nitrate nitrogen in the bioretention with different pH values and different ionic strength. The results show that aluminum powder has the highest the adsorption capacity. Langmuir adsorption isotherm equation and the quasi-secondary kinetic model are adopted to analyze the experimental data.
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