深圳土壤稀土元素的背景含量和影响因素研究

为研究深圳市土壤稀土元素的环境背景含量和空间分布特征，以不受或很少受人类活动影响的基本生态控制线区域作为调查范围，在深圳布设450个土壤表层点位、50个典型剖面点位，应用决策单元－多点增量采样方法采集土壤表层样品500个、土壤剖面样品100个.研究结果表明，深圳市表层土壤稀土元素的环境背景含量范围为23.66~1246.26mg/kg，算术平均值285.99mg/kg，高于中国土壤和广东省土壤；轻稀土元素相对于重稀土元素富集，稀土元素的环境背景含量在空间分布上呈现西高东低的特征.深圳市不同土类中稀土元素环境背景含量的95%分位值高低依次为赤红壤 > 红壤 > 黄壤.不同成土母质发育的土壤稀土元素环境背景含量95%分位值大小顺序为变质岩 > 花岗岩 > 片麻岩 > 凝灰熔岩 > 砂砾页岩 > 灰色灰岩.不同剖面层次的土壤稀土元素环境背景含量的95%分位值大小顺序为底层 > 中层 > 表层；随着深度的增加，深圳市土壤稀土元素的环境背景含量也逐渐增加，呈现底聚型特征.成土母质是影响土壤稀土元素环境背景含量的首要因素，花岗岩发育的土壤稀土元素环境背景含量要明显高于砂砾页岩；不同土类也会影响土壤稀土元素的环境背景含量分布，同一成土母质发育的赤红壤稀土元素环境背景含量要高于红壤.典型相关性分析表明，土壤铁、铝等元素与轻稀土元素，以及锰与重稀土元素的背景含量均呈现较强的正相关关系，土壤pH值、黏粒与稀土元素背景含量存在弱正相关，这也侧面反映了土壤稀土元素对成土母质的继承性.

The background concentration of rare earth element and its impact factor in soil of Shenzhen City

For the purpose of studying the environmental background concentration and spatial distribution characteristics of rare earth element in soil of Shenzhen, 450 soil surface sample sites and 50 typical soil depth profile sample sites were selected in the scope of basic ecological control line which was not or little affects by the human being. 500 top soil samples and 100 sectional samples were collected by unit-multi increment sampling method. The results showed that the range of the environmental background concentrations of REE in topsoil of Shenzhen was 23.66~1246.26mg/kg, the arithmetic average value was 285.99mg/kg, which was higher than that in soil of China and Guangdong province. The top soil of Shenzhen was enriched-type of light rare earth element, and the spatial distribution patterns of concentration of REE was high the west and low in the east. The sequence of 95% fraction value of REE concentration in different soil types was lateritic red soil > red soil > yellow soil. The order of 95% fraction value of REE concentration in different parent rocks was metamorphic rock > granite > gneiss > tuff lava > gravel shale > grey limestone. The order of 95% fraction value of REE concentration in different levels of soil profiles was under layer > middle layer > surface layer. The REE background concentration raised with the increase of soil depth, which showed a characteristic of accumulation on the bottom. The parent rocks was probably the first influential factor of REE background concentrations in soil, as which was remarkable higher in soil developed by granite than that by gravel shale. Different soil types also might affect the soil REE background concentration. The REE background concentration was higher in lateritic red soil than in red soil, which were derived from the identical parent rock. Canonical correlation analysis showed a significantly positive correlativity was found between Fe, Al and light rare earth element as well as between Mn and heavy rare earth element, while the correlativity between soil pH as well as clay particle and soil REE background concentration was weak. The result was also indicated the inheritance of soil REE from parent rock.