Abstract
In order to improve the utilization efficiency of road runoff and the remove effects of heavy metals, porous asphalt pavements have been used as an effective measure to deal with heavy metals in road runoff. However, the removal effect on dissolved heavy metal is weak. In this paper, basic oxygen furnace (BOF) slag was used as aggregate in porous asphalt concrete to improve the removal capacity of heavy metal. Road runoff solution with a copper concentration of 0.533 mg/L and a zinc concentration of 0.865 mg/L was artificially synthesized. The removal effect of BOF slag porous asphalt concrete on cooper and zinc in runoff was evaluated by removal tests. The influence of rainfall intensity and time on the removal effect was discussed. The results obtained indicated that BOF slag porous asphalt concrete has a better removal effect on copper. The removal rate of copper is 57–79% at the rainfall intensity of 5–40 mm/h. The removal rate of zinc is more susceptible to the changes of rainfall intensity than copper. The removal rate of zinc in heavy rain conditions (40 mm/h) is only 25%. But in light rain conditions (5 mm/h), BOF slag porous asphalt concrete maintains favorable removal rates of both copper and zinc, which are more than 60%. The heavy metal content of runoff infiltrating through the BOF slag porous asphalt concrete meets the requirements for irrigation water and wastewater discharge. The results of this study provide evidence for the environmentally friendly reuse of BOF slag as a road material and the improvement of the removal of heavy metal by porous asphalt concrete.
Highlights
With the rapid development of urbanization and the continuous increase of highway mileage and traffic volume, soil pollution and water pollution caused by highways have gradually attracted attention
The results of this study provide evidence for the environmentally friendly reuse of basic oxygen furnace (BOF) slag as a road material and the improvement of the removal of heavy metal by porous asphalt concrete
When the solution infiltrates through the BOF slag porous asphalt concrete, the free calcium oxide (f-CaO) in the BOF slag hydrates and the solution becomes alkaline
Summary
With the rapid development of urbanization and the continuous increase of highway mileage and traffic volume, soil pollution and water pollution caused by highways have gradually attracted attention. Various pollutants from vehicles or the atmosphere accumulate on the road during non-rainfall periods, and when it rains, the accumulated road pollutants are washed by rainfall runoff and carried into the groundwater or soil, causing potential harm to the surrounding environment [1,2]. In addition to conventional pollutants such as suspended solids and organic pollutants, road runoff contains a variety of heavy metals, which are difficult to degrade in the environment, and the harm to organisms is generally irreversible for life [3,4]. Of pavement pollutants can be removed by conventional cleaning measures [5]. In order to remove road runoff pollutants more efficiently, advanced measures have been applied to road engineering such as vegetation control, wet retention ponds, and infiltration systems [7]. Wet retention ponds can reduce the dissolved nitrogen species, total and dissolved phosphorus, and total suspended solids concentrations for more than
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