RESUMEN
In order to explore the characteristics and sources of heavy metal pollution in cultivated soil around a red mud yard in Chongqingï¼ the content and spatial distribution characteristics of eight heavy metal elements ï¼Cdï¼ Crï¼ Hgï¼ Niï¼ Pbï¼ Asï¼ Cuï¼ and Znï¼ in the soil were analyzedï¼ and the single factor pollution index method and Nemerow comprehensive pollution index method were used to evaluate the characteristics of heavy metal pollution in soil. On the basis of correlation analysisï¼ the APCS-MLR and PMF models were used to quantitatively analyze the sources of heavy metals. The results showed that the average contents of the other seven heavy metal elements were higher than the background values of Chongqing soilï¼ except for that of Cr. The heavy metals Cdï¼ Hgï¼ and As were moderately pollutedï¼ and Pbï¼ Cuï¼ Niï¼ and Zn were mildly polluted. The spatial distribution pattern of Crï¼ Niï¼ Pbï¼ Cuï¼ and Zn in the soil was similarï¼ and there was a very significant positive correlation between them ï¼P < 0.01ï¼. The spatial distribution characteristics of Cdï¼ Hgï¼ and As were significantly differentï¼ and there was no significant correlation between them ï¼P > 0.05ï¼. The source apportionment showed that the sources of heavy metals in the soil in the study area were relatively complexï¼ and the APCS-MLR and PMF models could identify the same four pollution sourcesï¼ namely red mud yard percolation emission and natural sourcesï¼ thermal power generation emission sourcesï¼ agricultural activities and natural sourcesï¼ and non-ferrous metal smelting emission sources. There was little difference in the results of source apportionment between the two models. The contribution rates of the four pollution sources in the APCS-MLR model were 51.8%ï¼ 18.0%ï¼ 15.9%ï¼ and 14.3%ï¼ respectivelyï¼ whereas those in the PMF model were 45.9%ï¼ 12.8%ï¼ 21.5%ï¼ and 19.8%ï¼ respectively.
RESUMEN
Three typical modern dry processing cement plants in Chongqing were chosen to investigate mercury emission characteristics and its source and fate through a mercury mass balance method by analyzing mercury contents in all input and output materials. The results showed that limestone was the main source of mercury in three cement plants followed by coal, and their mercury concentrations were (0.025±0.001)-(0.032±0.002) mg·kg-1and (0.080±0.002)-(0.110±0.012) mg·kg-1, respectively. The highest mercury level in all required input materials was (0.447±0.007)-(0.525±0.009) mg·kg-1 for gypsum, while the mercury content of other raw materials were very low. Most of the mercury released from these cement plants entered into flue gas, and the mercury of gypsum entered into cement. The mercury emission fluxes were calculated to be (73.42±8.10)-(215.18±10.75) g·d-1 in these three selected plants. The mercury emission factors for clinke and cement (EFclinker and EFcement) were (0.016±0.001)-(0.049±0.001) g·t-1 and (0.011±0.000)-(0.036±0.001) g·t-1, respectively, which were significantly lower than that employed in cement industry according to the foreign mercury emission factors in the past.
RESUMEN
To preliminarily discuss the mercury emission characteristics and its mass balance in each process of the iron and steel production, a typical iron and steel enterprise was chosen to study the total mercury in all employed materials and estimate the input and output of mercury during the steel production process. The results showed that the mercury concentrations of input materials in each technology ranged 2.93-159.11 µg · kg⻹ with the highest level observed in ore used in blast furnace, followed by coal of sintering and blast furnace. The mercury concentrations of output materials ranged 3.09-18.13 µg · kg⻹ and the mercury concentration of dust was the highest, followed by converter slag. The mercury input and the output in the coking plant were 1346.74 g · d⻹ ± 36.95 g · d⻹ and 177.42 g · d⻹ ± 13.73 g · d⻹, respectively. In coking process, mercury mainly came from the burning of coking coal. The sintering process was the biggest contributor for mercury input during the iron and steel production with the mercury input of 1075. 27 g · d⻹ ± 60.89 g · d⻹ accounting for 68.06% of the total mercury input during this production process, and the ore powder was considered as the main mercury source. For the solid output material, the output in the sintering process was 14.15 g · d⻹ ± 0.38 g · d⻹, accounting for 22.61% of the total solid output. The mercury emission amount from this studied iron and steel enterprise was estimated to be 553.83 kg in 2013 with the emission factor of 0.092 g · t⻹ steel production. Thus, to control the mercury emissions, iron and steel enterprises should combine with production practice, further reduce energy consumption of coking and sintering, or improve the quality of raw materials and reduce the input of mercury.