Occurrence and release of cadmium, chromium, and lead from stone coal combustion

Stone coal,which has high ash yield,low carbon content,and low calorific value,releases toxic elements during the combustion process.In this study,samples were collected from an open-pit stone coal mine in the southern Shaanxi province,China.A simulated combustion experiment and sequential chemical extraction were applied to investigate the enrichment,occurrence,and release of Cr,Cd,and Pb in raw stone coal and ash.The contents of Cr,Cd,and Pb in raw stone coal were larger than those reported for other coals in China and worldwide.The enrichment factors of Cr,Cd,and Pb in ash at different temperatures exceeded 0.7,with the exception of Cd at 1000 ℃.This indicates that Cr,Cd,and Pb were first enriched at low temperature (below 600 ℃) and then volatilized at high temperature due to the decomposition of clay minerals.The dominant forms of toxic elements in raw stone coal were Fe-Mn-bound Cr and Cd and carbonates of Pb.As the temperature increased,the organic forms decreased obviously,and the residual forms increased;however,the Fe-Mn-bound forms remained the dominant forms of Cr,Cd,and Pb.

Distribution and modes of occurrence of uranium in coals of Eastern Yunnan,China

Uranium is an environmentally hazardous element,and is commonly present at trace levels(2.4 μg/g for world coals)in coal deposits.However,selected coal deposits could be highly enriched in uranium.In this study,15 coal samples were collected from Eastern Yunnan coal deposits,China,aiming to characterize the distribution and the occurrence of uranium in those coals.In studied samples,uranium content varied from 0.36 to 8.28 μg/g,with an average value of 3.76 lg/g.Generally,uranium content in coals from northern coal mines(3.02±2.44 μg/g,n=5)were lower than it in southern coal mines(4.13±2.30 μg/g,n=10).Uranium in coal samples showed no obvious correlation with total sulfur,whereas was positively correlated with ash yield.The results of sequential chemical extraction procedure confirm that organic-bound is the dominant occurrence of uranium.The slight enrichment of uranium in studied coals was probably attributed to sedimentation processes,hydrological conditions and tectonic structure of the coal deposits.

Source parameter and rupture process of the M_W6.3 early strong aftershock immediately following the 2016 M_W7.8 Kaikoura earthquake(New Zealand)

The 2016 A/w7.8 Kaikoura(New Zealand)earthquake was the most complex event ever instrumentally recorded and geologically investigated,as it ruptured on more than 12 fault segments of various geometries.To study the mainshock rupture characteristics,geodetic methods like InSAR and GPS play an essential role in providing satisfactory spatial resolution.However,early strong aftershocks may cause extra ground deformation which bias the mainshock rupture inversion result.In this paper,we will focus on studying the Mw 6.3 aftershock,which is the only A/6+thrust slip aftershock that occurred only 30 minutes after the Kaikoura mainshock.We will relocate the hypocenter of this event using the hypo 2000 method,make the finite fault model(FFM)inversion for the detailed rupture processes and calculate the synthetic surface displacement to compare with the observed GPS data and figure out its influence on the mainshock study.Although we are not able to resolve the real ruptured fault of this event because of limited observation data,we infer that it is a west-ward dipping event of oblique slip mechanism,consistent with the subfault geometries of the Kaikoura mainshock.According to the inverted FFM,this event can generate 10-20 cm ground surface displacement and affect the ground displacement observation at nearby GPS stations.