| The city-cluster along the Yangtze River in Anhui Province (as city-cluster) is one ofthe most important economic development zones in this province, and is an important partof Yangtze River delta industry. In this study,32sampling points were laid in thecity-cluster, and the soil samples were collected at A and C layer of each sampling points.The physical and chemical properties, and the content of Cu, Cd, Pb, Zn, As, Cr, Hg andNi of soil samples in A layer were analyzed. Also, the content of soil heavy metals in Clayer was determined. The content characteristics, vertical distributions and differences inregional distribution of soil heavy metals were studied, and the tendency of the content inthe past20years was analyzed. Furthermore, the soil environmental capacity of heavymetals was calculated. This research worked as a scientific basis for soil environmentalquality evaluation, heavy metals total amount control and industry decision of government.The main contents and results of this research were as follows:1. The pH, organic matter and cation exchange capacity (CEC) in A layer of soilswere determined. The results showed that the range of pH was4.33～7.64, organic matterwas0.19%～4.59%and CEC was6.63～24.75cmol/kg.2. The content characteristics of heavy metals in the soil were studied. The resultssuggested that the contents of heavy metals except Cu, Cd and Ni in each sampling pointswere lower than the National Secondary Standards of soil. The Cu content of two samplingpoints over the National Secondary Standards, the biggest content was2.8times than theNational Secondary Standards, appeared in Zongyang of Anqing, and the content was137.50mg/kg. The Cd content of two sampling points over the National SecondaryStandards, the biggest content was1.3times than the National Secondary Standards,appeared in Eqiao of Wuhu, and the content was0.38mg/kg. The Ni content of threesampling points over the National Secondary Standards, the biggest content was1.8timesthan the National Secondary Standards, appeared in Taihu of Anqing, and the content was70.30mg/kg.3. The vertical distributions of soil heavy metals were studied. The results showedthat the ratio value on the contents of heavy metals except Cd, Hg and Ni in Aand C layerof soil were closed to1, the distributions of these elements in the soil were evener, theinput and output were almost in balance.4. The differences in regional distribution of soil heavy metals were assessed. The results suggested that compared with the mean of A layer soil heavy metals in city-cluster,the contents of Pb, Zn, As, Cr, Hg and Ni were high in Wuhu, Cd, Cr and Ni were high inMaanshan, As and Cr were high in Tongling, Zn were high in Chizhou, Hg were high inChaohu and Xuancheng, Cu, Zn and Ni were high in Shucheng, and the contents of soilheavy metals in the other cities were closed to the mean.5. The tendency of soil heavy metals in the past20years was analyzed. The resultsshowed that compared with the mean of soil heavy metals in Anhui Province in seventhfive-year plan period, a few heavy metals content in city-cluster declined, such as Pb, Znand As; the rest rised, and the content of Hg increased87.5%. Compared with thebackground value of soil heavy metals in seventh five-year plan period of each city, thecontent of Cu in the soil of Chuzhou varied significantly, was2.58times as20years ago,Cd content in Xuancheng was2.52times, Pb content in Xuancheng was1.39times and inTongling was only0.49times, Zn content in Hefei was0.44times and in Chuzhou was2.12times, As content in Tongling was2.05times, but in Anqing and Chuzhou were only0.55times and0.40times respectively, Cr content in Hefei, Tongling, Chuzhou andShucheng declined, but in other cities had a certain rise, Hg content in Chaohu andShucheng were2.50times and2.60times respectively, but in Maanshan was only0.59times, Ni content in the cities except Shucheng had a certain rise.6. The environmental capacity of soil heavy metals in each city was calculated. Theresults suggested that in the soil of city-cluster, the average of dynamic capacity were6.6～131times of the static capacity. The sequence of the dynamic capacity was Pb＞Cr＞Zn＞Cu＞Ni＞As＞Hg＞Cd. The environmental capacity of Pb was62.79852kg/hm~2·a,which was the largest. However, the dynamic capacity of Hg and Cd were only0.075kg/hm~2·a. In fact, we choosed the minimum of dynamic capacity as the maximum input ofheavy metals in per hectare land of city-cluster every year, which was Pb：62.5kg/hm~2·a，Cr：62.5kg/hm~2·a，Zn：50kg/hm~2·a，Cu：12.5kg/hm~2·a，Ni：10kg/hm~2·a，As：7.5kg/hm~2·a，Hg：0.075kg/hm~2·a，Cd：0.075kg/hm~2·a.7. The reasons for the variation of soil heavy metals and the control measures wereanalyzed. The main reasons for the increase of soil heavy metals were the expansion ofindustry and the frequency of mining. For the standpoint of government, the industry of Hgand Cd in the cities along the Yangtze River should be limited, but the industry of Pb, Cr,Zn and Cu in the south of Anhui Province still have some development space. |
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