Abstract
Atmospheric emission of heavy metals from different anthropogenic sources is a great concern to human beings due to their toxicities. In order to disclose the emission levels and the distribution patterns of zinc (Zn) in the modern cement industry with respect to its low boiling point (~900 °C) comparing to the high-temperature (1450 °C) clinker production process, solid samples representing the input and output flow of Zn during the entire production process in two preheater–precalciner cement plants (CPs) were collected and analyzed. For the first time, it was found that the behaviour of Zn inside different precalciner CPs was similar despite a huge difference in the Zn inputs to the CPs; namely, almost all the Zn input was output in clinker, which was then mixed with different additives and retarder to make cement products. The high-temperature clinkerisation process would incorporate Zn into the aluminosilicate of clinker. As a result, there was no enrichment of Zn during clinker production and the atmospheric emission factor was relatively low at 0.002%, or 1.28–9.39 mg Zn·t−1 clinker. Our result for the atmospheric Zn emissions from CPs was much lower than most previous reports, implying the CPs were not a crucial Zn emission source. However, the higher load of Zn in some raw/alternative materials—like nonferrous smelting slag with a Zn content of ~2%—could greatly increase the content of Zn in clinker and cement products. Therefore, further investigation on the environmental stability of Zn in such Zn-laden cement and concrete should be carried out.
Highlights
Trace elements in the Earth’s surface system are critical to livestock wellbeing due to their biological functions or toxicities [1]
Atmospheric emissions of Zn from anthropogenic sources are an important source of Zn, which can enter the human body by dispersion, deposition, assimilation by plants and transferral through the food chain [9,10]
The fate of Zn during the whole production process inside these two cement plants (CPs) was analyzed according to the research framework shown in Figure A2, and will be discussed in turn in the following subsections
Summary
Trace elements in the Earth’s surface system are critical to livestock wellbeing due to their biological functions or toxicities [1]. The abundance of trace elements in the ambient environment is affected by both natural and anthropogenic sources [2,3]. When the environmental levels of Zn exceed those required by the plant or microorganism, toxic effects can result [8]. Atmospheric emissions of Zn from anthropogenic sources are an important source of Zn, which can enter the human body by dispersion, deposition, assimilation by plants and transferral through the food chain [9,10]. This can result in adverse human health effects [11,12].
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