【作者】 王凌青；

【导师】 卢新卫；

【作者基本信息】 陕西师范大学 ， 环境科学， 2007， 硕士

【摘要】 土壤重金属污染因其隐蔽性、不可逆性、后果严重性等特点越来越受到重视。本文经过野外调查和资料收集，在西安市周边农田分东郊、南郊、西郊和北郊共69个采样点采集土壤样品，每个采样点分0～10cm、10～20cm和20～30cm3层共采集207个土壤样品。测定了土壤理化性质（土壤粒径、有机质含量、pH值、磁化率），用原子荧光光度计测量了土壤中As和Hg元素的含量，用原子吸收分光光度计火焰法测定土壤样品中Cu、Cr、Pb、Zn、Mn和Ni含量，用连续萃取法分析测定了土壤中重金属Cu、Cr、Zn、Mn和Ni的赋存形态，讨论了影响土壤重金属含量及形态的因素，以期为农业生产和防治重金属污染提供参考依据。本文主要结论如下：1．西安市郊农田土壤粒径组成平均是黏粒为11.16％，粉沙粒为63.44％，沙粒为25.41％，土壤质地类型为粉沙质壤土。土壤pH值平均为8.6，为碱性土壤；土壤中有机质的含量平均为2.69％，属于Ⅲ级，尤其南郊和西郊土壤中有机质含量比较高；土壤低频磁化率、高频磁化率和频率磁化率平均值分别为126.45(10^-8m³／kg)、118.49(10^-8m³／kg)和6.04（％）。2．西安市郊农田土壤中重金属元素平均含量Cu为34.02 mg／kg（10.56～115.30mg／kg），Zn为157.03 mg／kg（63.61～382.80 mg／kg），Cr为67.87 mg／kg（26.4～156.3mg／kg），Mn为541.15 mg／kg（341～818.98 mg／kg），Ni为58.67 mg／kg（30.55～113.80mg／kg），Pb为67.41 mg／kg（2.32～182.41 mg／kg），As为7.75 mg／kg（2.08～15.94mg／kg），Hg为1.42 mg／kg（0.01～17.50 mg／kg）。在采集的垂直剖面上，Cu、Zn、Mn、Cr大致表现出随深度的增加而下降的趋势，Pb、As、Hg、Ni则没有明显的随深度变化的规律，重金属元素在垂直方向上的分布除了受人类活动、作物等的影响外，还受水的浸渍、流失和渗透等诸多作用的影响。3．西安市郊农田土壤中重金属元素多种污染评价指标平均为，单因子污染指数除了As（0.66）、Zn（1.04）、Mn（1.0）小于1，表明尚未造成污染，其余Hg（11.26）、Cu（1.51）、Pb（3.51）、Ni（2.32）和Cr（2.4）的单因子指数均超过1，其中Hg（11.26）和Pb（3.51）比较突出；综合污染指数为8.85，说明重金属污染已经相当严重；以地质累积指数进行评价，Hg（1.37）和Pb（1.23）处于偏中度污染，Ni（0.61）和Cr（0.66）处于轻度污染，而As（-1.21）、Cu（-0.11）、Zn（-0.56）和Mn（-0.59）尚未造成污染；以潜在生态危害系数法进行评价，除了Hg（450.12）污染比较严重，达到极强程度，具有很强的潜在生态危害外，As（6.61）、Cr（4.81）、Cu（7.54）、Pb（17.55）、Mn（1.99）、Ni（11.58）和Zn（1.04）具有轻微的潜在生态危害；综合多种重金属的潜在生态危害指数值为501.25，表明西安市郊农田土壤重金属污染达到强生态危害型，生态风险很高。4．西安市郊农田土壤中重金属元素的赋存形态各异。Cu主要赋存形态是残留态为63.74％（51.98～78.90％），其次是铁锰氧化物结合态为23.53％（7.01～42.59％），碳酸盐结合态为6.16％（0.42～23.75％），有机物结合态为4.62％（0.36～10.55％），可交换态所占百分比最少，平均为1.95％（0.49～3.75％）；Zn主要赋存形态是残留态为65.96％（47.14～80.59％），其次是铁锰氧化物结合态为22.78％（12.25～34.51％），有机物结合态为5.37％（2.03～0.15％），可交换态平均为2.42％（ND～11.89％），碳酸盐结合态为3.48％（0.8～13.40％）；Cr主要赋存形态是残留态为75.35％（60.45～84.13％），其次是铁锰氧化物结合态为15.06％（8.71～21.89％），有机物结合态为4.79％（2.23～10.89％），碳酸盐结合态为2.95％（ND～6.60％），可交换态平均为1.85％（ND～3.37％）；Mn主要赋存形态是残留态为82.57％（78.06～88.37％），其次是铁锰氧化物结合态为14.34％（8.96～18.44％），碳酸盐结合态为2.12％（1.49～2.87％），有机物结合态为0.73％（ND～1.53％），可交换态所占比重最小，平均为0.36％（ND～1.03％）；Ni主要赋存形态是残留态为72.05％（54.72～85.82％），其次是铁锰氧化物结合态为16.36％（8.79～26.28％），可交换态为5.24％（1.97～8.11％），碳酸盐结合态为3.84％（1.02～7.05％），有机物结合态为1.88％（ND～4.66％）。5．统计分析表明，Cu分别和Zn、Cr、Ni、Mn表现出较好的相关性；Zn分别和Cr、Mn、Pb、Ni表现出较好的相关性；Mn分别和Ni、Hg有较好的相关性；Ni和As、Hg，Pb和As，As和Hg等都表现出了较好的相关性；Cu、Zn、Cr、Mn、Ni、Pb等总量与低频磁化率相关性较好；Cu、Cr、Ni、Pb等总量与土壤pH值相关性较好；Cu、Zn、Cr、Mn、Ni、Pb等总量与土壤黏粒所占比重相关性较好；Cu、Zn、Mn、Ni、Pb、Hg等总量与土壤有机质含量相关性较好。6．土壤理化参数也与重金属各形态间有较好的相关性。Cu的可交换态与高频磁化率、黏粒含量有较好的相关性，残留态与土壤黏粒含量有较好的相关性；Zn的可交换态与有机质含量，碳酸盐结合态与土壤黏粒，有机物结合态与有机质含量，残留态与有机质含量有较好的相关性；Cr的铁锰氧化物结合态与高频磁化率有较好的相关性，与土壤pH值、土壤黏粒负相关，有机物结合态与磁化率有较好的相关性，Cr的残留态与高频磁化率、土壤黏粒有较好的相关性；Mn的碳酸盐结合态与低频磁化率、土壤黏粒、有机质含量有较好的相关性，铁锰氧化物结合态与有机质含量有较好的相关性，残留态与磁化率、土壤黏粒有较好的相关性；Ni的可交换态与磁化率有较好的相关性，碳酸盐结合态与磁化率、土壤黏粒有较好的相关性，有机物结合态与磁化率、pH值有一定的相关性，Ni的铁锰氧化物结合态与土壤pH值有一定的负相关性，残留态与磁化率、土壤黏粒、有机质含量有较好的相关性。更多还原

【Abstract】 Based on full field survey and data collection, 207 farmland soil samples were collected from 69 sampling sites. These sampling sites distributed in Eastern suburb, Southern suburb, Western suburb and Northern suburb of Xi’an. At each sampling site, soil samples were collected from three different profiles, named Horizon A （depth from 0 to 10cm）, Horizon B （depth from 10 to 20cm） and Horizon C （depth from 20 to 30cm）. Some soil physical and chemical properties including soil particle-size, organic matter value, pH value and magnetic susceptibility were determined. Arsenic and mercury in the soil samples were determined by atomic fluorescence spectrometry and copper, chromium, lead, zinc, manganese, nickell in the soil samples were determined by flame atomic absorption spectrometry. Chemical speciation of heavy metal elements copper, chromium, zinc, manganese, nickel was studied using sequential extraction method. Factors influencing heavy metal elements concentration and chemical speciation were discussed. These could provide a reference for agriculture production and prevntion and controlling of heavy metal contamination in farmland soil. The main conclusions were listed below:1. The soil texture type of farmland soil in the suburb of Xi’an is silty sand soil and the average clay content was 11.16%, the average silty sand content is 63.44%, and the average Sand Particles content was 25.41%. The average pH value was 8.6, so soil was the alkaline soil. The average organic matter content was 2.69%, especially higher in the Southern suburb and Western suburb. Low-frequency magnetic susceptibility, high-frequency magnetic susceptibility and frequency magnetic susceptibility were 126.45(10^-8m³/kg)、118.49(10^-8m³/kg) and 6.04%, respectively.2. The average content of copper, zinc, chromium, manganese, nickel, lead, arsenic and mercury in the soil samples were 34.02 mg/kg（from10.56 to 115.30 mg/kg）, 157.03mg/kg（from 63.61 to 382.80 mg/kg）, 67.87 mg/kg（from 26.4 to 156.3 mg/kg）, 541.15mg/kg（from 341 to 818.98 mg/kg）, 58.67 mg/kg（from 30.55 to 113.80 mg/kg）, 67.41mg/kg（from 2.32 to 182.41 mg/kg）, 7.75 mg/kg（from 2.08 to 15.94 mg/kg） and 1.42mg/kg（from 0.01 to 17.50 mg/kg）. Content of mercury, lead, zinc and copper in farmland soil in the suburb of Xi’ an is higher. Content of copper, zinc, manganese and chromium declined with the increasing depth in the soil profile. Other heavy metal elements didn’t present this regular pattern: The heavy metal elements content change in the soil profile was influnced by many factors such as human activities, plant uptake, and immersion, impenetrate and loss of water.3. Several pollution evaluate indices of heavy metals in cropland soil samples around Xi’ an city were calculated. Single Factor Contaminant Index of arsenic, zinc, manganese, mercury, copper, lead, nickel, and chromium was 0.66, 1.04, 1.0, 11.26, 1.51, 3.51, 2.32 and 2.4, respectively. Synthetical Pollution Index was 8.85 and it indicated that the heavy metal contamination was serious. Geoaccumulation index of arsenic, zinc, manganese, mercury, copper, lead, nickel, and chromium was -1.21, -0.56, -0.59, 1.37, -0.11, 1.23, 0.61 and 0.66, respectively. The potential ecological risk factor of mercury was 450 and the potential ecological was strong, and that of arsenic, chromium, copper, lead, manganese, nickel and zinc was 6.61, 4.81, 7.54, 17.55, 1.99, 11.58 and 1.04, respectively. Potential Ecological Risk Index was 501.25 and it indicated that heavy metal contamination was serious and the ecological risk was high.4. Chemical speciation of different heavy metal elements in Farmland Soil in the Suburb of Xi’ an was different. The main speciation of copper was residual form and its average percent was 63.74% （from 51.98 to 78.90%）, and the second was Fe-Mn oxide combined form and its average percent was 23.53%（from 7.01 to 42.59%）. The average percent of the carbonate combined form, the organic combined form and the exchangeable form was 6.16%（from 0.42 to 23.75%）, 4.62%（from 0.36 to 10.55%） and 1.95 %（from 0.49 to 3.75%）. The main speciation of zinc was residual form and its average percent was 65.96% （from 47.14 to 80.59%）, and the second was Fe-Mn oxide combined form and its average percent was 22.78%（from 12.25 to 34.51%）. The average percent of the organic combined form, the exchangeable form and the carbonate combined form was 5.37%（from 2.03 to 20.15%）, 2.42 %（from Non-deteced to 11.89%） and 3.48 %（from 0.89 to 13.4%）. The main speciation of chromium was residual form and its average percent was 75.35% （from 60.45 to 84.13%）, and the second was Fe-Mn oxide combined form and its average percent was 15.06 %（from 8.71 to 21.89%）. The average percent of the organic combined form, the carbonate combined form and the exchangeable form was 4.79 %（from 2.23 to 10.89%）, 2.95%（from Non-deteced to 6.60%） and 1.85 %（from Non-deteced to 3.37%）. The main speciation of manganese was residual form and its average percent was 82.57% （from 78.06 to 88.37%）, and the second was Fe-Mn oxide combined form and its average percent was 14.34 %（from 8.96 to 18.44%）. The average percent of the carbonate combined forms the organic combined form and the exchangeable form was 2.12 %（from 1.49 to 2.87%）, 0.73 %（from Non-deteced to 1.53%） and 0.36 %（from Non-deteced to 1.03%）. The main speciation of nickel was residual form and its average percent was 72.05% （from 54.72 to 85.82%）, and the second was Fe-Mn oxide combined form and its average percent was 16.36 %（from 8.79 to 26.28%）. The average percent of the exchangeable form, the carbonate combined form and the organic combined form was 5.24 %（from 1.97 to 8.11%）, 3.84 %（from 1.02 to 7.05%） and 1.88 %（from Non-deteced to 4.66%）.5. The statistical data showed that there was a close correlation between copper and zinc, chromium, nickel, manganese, respectively. A close correlation also existed between zinc and chromium, manganese, lead, nickel, respectively. There was also a close correlation between manganese and nickel, mercury, respectively. A close correlation also existed between nickel and arsenic, lead and arsenic, arsenic and mercury, respectively. Low-frequency susceptibility had a close correlation with the content of copper, zinc, chromium, manganese, nickel, and lead, respectively. Soil pH value also had aclose correlation with copper, chromium, nickel, and lead, respectively. Soil clay had a close correlation with the content of copper, zinc, chromium, manganese, nickel, and lead, respectively. Soil organic matter had a close correlation with the content of copper, zinc, manganese, nickel, mercury and lead, respectively.6. The statistical data showed that there was a close correlation between soil physical and chemical properties and different chemical speciation. For copper, there was a close correlation between the exchangeable form and high-frequency susceptibility, soil clay, respectively, and between the residual form and soil clay. For zinc, a close correlation existed between the exchangeable form and soil organic matter, carbonate combined form and soil clay, organic combined form and soil organic matter, residual forms and soil organic matter, respectively. For chromium, a close correlation existed between Fe-Mn oxide combined form and high-frequency susceptibility, organic combined form and susceptibility, respectively. And a negative correlation was found between Fe-Mn oxide combined form and pH value, soil clay, respectively. For manganese, there was a close correlation between carbonate combined form and susceptibility, soil clay, soil organic matter, respectively, and between Fe-Mn oxide combined form and soil organic matter. A close correlation also existed between the residual form and susceptibility, soil clay. For nickel, there was a close correlation between the exchangeable form and susceptibility, arbonate combined form and susceptibility, soil clay, respectively. A close correlation existed between organic combined form and susceptibility, pH value, respectively. A negative correlation was found between Fe-Mn oxide combined form and pH value. There was a close correlation between the residual form and susceptibility, soil clay, soil organic matter, respectively.更多还原