Study On The Risk Of Heavy Metal Pollution In Ore At The Port Stockyard

In China，stockpiling, loading and unloading of ore at port are still openextensive management. During stacking process, rain leaching will cause thedissolution of heavy metals in the ore, which is a potential pollution source of coastalwaters. The dissolution characteristics and leaching behaviors of typical ore at TianjinPort stockyard were investigated by static soaking and dynamic leaching experiments.The relationship of speciation of heavy metals with rain leaching behaviors of heavymetals in typical ores at port stockyard was also investigated by speciation analysis.The achievements are as follows:（1）Static dissolution experiments with ores of different types and differentcountries were carried out. According to the concentrations of heavy metals dissolvedfrom the ores and sewage discharge standards, lead ore and copper ore were selectedas the typical ores, and Zn, Pb and Cd in the lead ore and Ni in the copper ore wereselected as the typical heavy metals. Influences of time, pH and temperature onrelease of heavy metals in typical ores were investigated by static soakingexperiments. The results showed that the concentrations of Zn and Pb, Cd releasedfrom the lead ore increased with time and temperature, while the concentrations of Nibegan to decline after10d. The concentrations of Zn, Pb and Cd released from thelead ore as well as Ni from the copper ore did not vary significantly with pH (3.5to7.5).（2）Based on the results of static soaking experiments, two significant factors(temperature and time) were investigated by dynamic leaching of lead ore and copperore at20℃,25℃and35℃. The results showed that the concentrations of Zn andPb released from the lead ore fluctuated within a certain range and the cumulativerelease increased linearly with time during the leaching period. The dissolution curveof Zn and Cd in the copper ore was basically the same. At the beginning of leaching,the concentrations of Zn and Cd were very high, and then rapidly decreased to lowlevels within1d, thereafter, fluctuated within this range. The cumulative amounts ofZn and Cd released could be divided into two stages, namely a rapid leaching stage(within1d) and a slow leaching stage (after1d). The impact of time on concentrationof Pb in copper ore was more complicated; the release of Zn and Pb in the lead oreincreased with temperature. The release of Zn in copper ore showed a negative correlation (20℃>25℃>35℃) with temperature after2-day leaching. Theimpact of temperature on concentration of Pb and Cd in copper ore was morecomplicated.（3）In order to better understand the release of heavy metals from the ores,speciation analysis of heavy metals in the ore (sequential extraction) was carried out.Water soluble fraction of Zn and Cd in copper ore both accounted for large proportion.The water soluble fraction of heavy metal has a high mobility. The amount of copperore was great, so the risk of Zn and Cd leaching from the ore was really high. Theproportions of water soluble fraction of Zn and Pb in lead ore as well as their rainleaching amounts were small. In particular, Pb and SO42-could form precipitate,leading to a lower environment risk. Therefore, speciation characteristics of heavymetals in ore at the port stockyard can be used to analyze and predict the potential riskfrom rain leaching of heavy metals, which could provide regulatory advice in practice.