Characteristics And Loading Estimates Of Heavy Metals In Urban Rainfall Runoff

Heavy metal pollution of urban rainfall runoff was the water pollution which formed by washing urban surface pollutants, Atmospheric particulates, surface dusts etc. and informed receiving waterbodies. Since quick urbanization in recent years, the areas of impermeable surface had increased leading to serious heavy metals pollution of urban rainfall runoff. With the support of Major Science and Technology Program for Water Pollution Control and Treatment (No.2009ZX07317-006), NNSF of China (No.40971259), and Shanghai excellent entancement plan (No.10XD1401600), the pollution characters and spatio-temporal changes were studied. Besides, first flush effects of rainfall runoff were also studied to proclaim the relationship between rainfall character and heavy metal EMCs. And the resouces of heavy metal in PM10S, surface dusts and catch-basin sediments were analyzed. Using EMCs of heavy metals(Cr, Cu, Fe, Mn, Ni, Zn, Hg and As) estimated urban heavy metal load in summer in Wenzhou City to supply stable datas to management of uraban non-point source pollution.The main conclusions can be summed up as follows.1. The study monitored 7 summer rainfall events in Shanghai and Wenzhou City, the results showed that contents of heavy metals in traffic artery, parking lot and community road were higher than other underlying surface. The contents of Fe, Mn, Ni, Zn, Hg (dissolved form) were related to pH and Cu, Fe and Mn (dissolved form) related to TSS. Dynamic changes of pH were not related to rainfall charaters, the opponent to heavy metals, and the TSS one showed indexmovement when the max value appeared the beginning of rainfall runoff.2. TSS EMC of the traffic artery runoff was the highest of all the underlying surfaces and exceeded Integrated Wastewater Discharge 2 Standard easily. Heavy metal EMCs except Hg were below to Surface Water III and V Standard, which EMCs of Cu, Mn and Zn got apparent spatial variability, but Hg EMC was not related to underlying surface types. Correlation coefficient was higher among ADWP, precipitation, rainfall intensity and EMCs of heavy metals.3. It was analyzed about first flush effects of urban rainfall runoff by using dimensionless cumulative curve. The main results determined that TSS gained first flush effect easier than heavy metals. It is efficient to control water pollution by remove the first 40% runoff. Except Fe, Mn and Ni, heavy metals appeared the first flush effects hard. FF30 of Mn was 51.12% and Cr was 31.84% which was the max value and min value of FF30. The result showed the effect of first flush mainly depended on the time of max rainfall intensity.4. The study research heavy metals in other environmental mediums affecting to the on in rainfall runoff including atmospheric deposition (dry and wet), surface dust etc. Heavy metal contents of PM10 in Shanghai and Wenzhou were higher than their background value of soil environment. EF of Mn and Ni were less than 1, meaned natural resource; EF of Zn was greater than 10, meaned human interference. Compared with heavy metal contents in urban rainwater, it had relationship with the contents in rainfall runoff and contributed a lot to heavy metal contents of rainfall runoff. The contents of heavy metals in surface dusts were higher in traffic artery and parking lot. The heavy metal pollution degree of surface dust was similar in both Shanghai City and Wenzhou City.5. The trend of Cr, Cr, Fe, Mn, Ni and Pb contents decreased progressively in the system of surface dust—catch-basin sediment—rainfall runoff, especially Mn. It indicated that on one hand resource of these heavy metals were similar; on the other hand heavy metal pollutants in surface dusts contributed more. The affection machining was affected by lots of facts, presented complexity and randomness and hard to centralize.6. By means of monitoring 5 rainfall events in summer in Wenzhou City(SX catchment and JS catchment), the EMCs of Cr, Cu, Fe, Mn, Ni, Zn, Hg and As were analyzed. After correcting CN value of SCS modeling and quantifying, summer heavy metal pollution loads were estimated. The results showed that the loads of Cr, Cu, Fe, Mn, Ni, Pb, Zn, Hg and As were 0.16kg, 0.40 kg, 2.06 kg, 0.69 kg, 0.23 kg, 1.85 kg, 0.04 kg and 0.35kg in SX catchment when the JS catchment were 0.05 kg,0.43 kg, 3.33kg, 3.35kg, 0.24kg,4.10 kg,0.08 kg and 0.22kg, which means JS catchment was affected critically by rainfall runoff pollution. Contribution rate of unerlying surface in SX catchment was roof>traffic artery>community road>grassland> parking lot, and JS catchment was community road>roof>grassland>traffic artery >parking lot.