Environmental Impact Assessment During Steel Slag Paving And Rapid Detection Of Heavy Metals In Wate

With the rapid development of highway construction in China,the demand for basalt materials is growing.Due to the limited reserves of basalt,a large number of exploitation will also cause certain environmental problems.so it is essential to find its alternatives.Steel slag is a solid waste,the strength,stability,durability and other physical and chemical properties of steel slag used in asphalt concrete have been confirmed in the early experimental section.However,the environmental hazard of steel slag in the paving process is worth evaluating.Steel slag asphalt concrete contains a small amount of heavy metals that may be released to the surrounding soil environment and water environment,causing harm.It is necessary to detect the content of heavy metals to evaluate its impact on the surrounding environment.The portable X-ray fluorescence spectrometer can be used to rapidly detect the heavy metal content in the soil at the pavement site,so that we can roughly understand the heavy metal content in the soil.The heavy metal content in water is at the micro gram level,which requires large-scale instrument detection.time-consuming and labor-intensive.In view of the test requirements of trace heavy metals in water of steel slag paving site,the heavy metal ions in water are adsorbed and transferred to the functional heavy metal enrichment membrane,and then the portable X-ray fluorescence spectrometer is used to detect,and a rapid detection method of trace heavy metal ions in water is explored.The main research content of this paper is divided into two parts.The first part is about the environmental impact assessment of steel slag in the process of road construction.The influence of laying steel slag asphalt concrete and basalt asphalt concrete on the content of heavy metals in the surrounding soil is compared.Through the evaluation,it is concluded that the main heavy metal pollution in the soil of steel slag asphalt concrete pavement is Zn,Pb and Cd,and the main heavy metal pollution in the soil of basalt asphalt concrete pavement is Zn and Cu.The content of heavy metals in plants at the soil sampling points is compared,and it is found that the main heavy metal pollution in plants around the steel slag asphalt pavement is Ni.The plants around basalt asphalt have different sources of heavy metal pollution with different parts of plants.Through the leaching experiments of basalt,steel slag and asphalt,we found that the heavy metal content of steel slag leaching solution was higher than that of basalt.At the same time,due to the coating effect of asphalt,the heavy metal leaching value of steel slag asphalt concrete was lower than that of pure steel slag.In the second part,aiming at the rapid detection of trace heavy metals in water around the steel slag paving site,a rapid detection method of trace heavy metals in water based on heavy metal enrichment membrane-portable X-ray fluorescence spectrometer was developed.Firstly,caffeic acid was introduced into polypropylene nonwovens by surface co-deposition method to prepare heavy metal ion enrichment membrane.Then the adsorption properties of the enrichment membrane for Cu²⁺,Pb²⁺,Co²⁺,Ni²⁺,Zn²⁺,Cd²⁺were investigated.It was found that more than 90%of the metal ions in water could be transferred to the heavy metal enrichment membrane when the number of enrichment membrane layers was more than four layers,the filtration flow rate was 1ml/min and the pH was 6.Finally,the content of heavy metal ions on the enrichment membrane was detected by a portable X-ray fluorescence spectrometer.The results showed that the heavy metal content on the enrichment membrane had a good linear relationship with the signal value of the portable X-ray fluorescence spectrometer.Therefore,the concentration of heavy metal ions in water could be deduced.It was found that the measurement error of six metal ions such as Cu²⁺and Pb²⁺in the range of ppb in water was within 20%in the presence of interference ions such as K⁺（10mg/L）Na⁺（100mg/L）and Mg²⁺（1mg/L）,which was basically the same as error of the portable X-ray fluorescence spectrometer itself...