广西贺州市典型矿区周边耕层土壤Cd通量特征

广西是我国西南部典型的地质高背景区，碳酸盐岩、黑色岩系、基性-超基性岩体与金属矿床（矿化体）强烈的风化成壤作用，使土壤重金属镉（Cd）含量高于全国其他地区.为了查明在地质高背景区矿业活动对耕层土壤环境质量的影响程度，在广西贺州市选取矿业活动影响区和对照区为研究区，系统开展了耕层土壤Cd输送途径及输送通量密度的对比研究.结果表明，在矿区和对照区耕层土壤中，Cd大气干湿沉降通量密度平均值分别为1.87 g·（hm²·a）^-1和1.52 g·（hm²·a）^-1，分别占总输入通量密度的61.5%和60.3%，施肥和灌溉输入土壤Cd通量密度较低；Cd的输出途径均以地表水下渗为主，分别占总输出通量密度的75.4%和86.6%，农作物收割输出通量密度矿区高于对照区，且矿区内种植的水稻籽实Cd含量超标率更高，玉米籽实则未超标.整体上，矿区与对照区土壤Cd净输送通量密度分别为-3.05 g·（hm²·a）^-1和-4.05 g·（hm²·a）^-1，表现为土壤Cd淋失状态，但大气干湿沉降输入通量密度高值点和水稻籽实Cd含量超标点均主要分布在矿区周围，有可能对当地居民健康造成潜在威胁，因此建议通过监控和种植结构调整对该区域Cd污染土壤进行治理.

Characteristics of Cd Fluxe in Topsoil Around Typical Mining Area in Hezhou, Guangxi

Guangxi is a typical geological high background area in southwest China, where carbonates, black rock series, basic-ultrabasic rock mass, and metal deposits (mineralized bodies) exhibit strong weathering into loam, resulting in higher cadmium (Cd) content in the soil than that in other areas of China. In order to investigate the degree of influence of mining activities on topsoil environmental quality in the area with high geological background, we chose a mining area and control area in Hezhou for this research and systematically carried out a comparative study on Cd transport routes and transport flux density in topsoil. The results showed that the average atmospheric dry and wet deposition flux densities of Cd in the soil of the mining area and control area were 1.87 g·(hm²·a)^-1 and 1.52 g·(hm²·a)^-1, accounting for 61.5% and 60.3% of the total input flux density, respectively. The flux density of Cd in the soil by fertilization and irrigation was lower. Surface water infiltration was the main avenue of soil Cd output in both the mining area and control area, accounting for 75.4% and 86.6% of the total output flux density, respectively. The harvest output flux density in the mining area was higher than that in the control area, and the Cd content of rice planted in the mining area was higher than the standard, whereas that of maize was safe. On the whole, the net transport flux densities of soil Cd in the mining area and control area were -3.05 g·(hm²·a)^-1 and -4.05 g·(hm²·a)^-1, both of which showed Cd leaching in the soil. However, the points of high atmospheric deposition flux density and exceeding Cd content in rice were mainly distributed around the mining area, which may have posed a potential threat to the health of local residents. Therefore, it is suggested to control the soil Cd pollution through monitoring and planting structure adjustment.