珠三角是我国华南地区经济最活跃和人口最密集的地区，As 及其化合物普遍存在于环境中，被列为环境保护的重点监测物质。As在水域环境中不能被降解而消除，只能以不同的形态，在水、沉积物和生物体之间迁移转化。于2012年3月、5月、8月和12月分别对珠江三角洲河网水域13个站位水、沉积物中通过使用原子荧光光度法对As含量进行检测分析，探讨其时空分布特征，并对其污染状况进行初步评价，为该水域的生态环境保护提供基础依据。结果显示，水体As含量范围为0.43~7.27µg·L-1。水体中As含量存在明显的时空差异分布特征。时间上，5月略高于3月、8月和12月，其平均值分别为4.21、3.73、2.06和1.14µg·L-1；空间上，青岐（W1）等5个站位聚为一类，除横沥外，其余站位大多分布在西江干流上，具有相似的分布特征，可能主要受西江径流的面源污染影响而具有相似的砷污染来源；其余8个站位聚为一类，包括城镇化及城市化高度发达，人口密度大的河网分叉水域站位，所在区域城镇化主导行业差异较大，受居民生活污水和工业废水排入的影响大，主要为点源污染，受径流影响较小。珠江河网表层沉积物，As 含量范围为2.72~71.5 mg·kg-1，最大超标倍数为3.57，平均值为20.3 mg·kg-1。地质累积指数评价与潜在生态风险系数评价法分别考虑到重金属在土壤中的地球化学行为及环境毒性差异等因素，这两种方法结果一致表明研究区域为低污染水平。结合应用这两种评价方法，可更全面地对珠三角河网沉积物As污染状况进行系统评价。对河网各月份水和沉积物中As含量进行线性回归分析,发现两者存在显著意义的负相关关系r=0.356>r0.05(1,50)=0.273，可能是含As污染物进入水体后，在水体不断的稀释、沉降、生化等作用的综合影响，呈现空间延伸性变化的特点。%The Pearl River Delta (PRD) is the most developed and densely populated area in south China. With the rapid development of economy, the concentration of arsenic in the environment, especially in aquatic ecosystems, has been widely monitored. As one of the hazardous metalloid toxicant, arsenic can’t be eliminated by degradation, but be migrated and transformed among water, sediment and biota in different forms, which may threaten the ecological health. To investigate the distribution and pollution levels of arsenic in the PRD, water and sediment samples were collected in 13 sampling sites during March, May, August and December of 2012. Arsenic contents were determined by atomic fluorescence spectrophotometry. The concentration of dissolved arsenic ranged from 0.43 to 7.27 µg·L-1 during the whole investigation, showing obvious temporal and spatial variation. Temporally, the average arsenic concentration in water was slightly higher in May than that in March, August and December, with the average concentration of 4.21, 3.73, 2.06 and 1.14 µg·L-1, respectively. In terms of the spatial distribution, arsenic concentrations in five sampling sites including Qingqi, Zuotan, Waihai, Xiaolan and Hengli were defined as one cluster. These sites principally located in the West River, showed similar distribution characteristics. The similar source of arsenic in these areas might be mainly affected by non-point source pollution in the runoff of West River. The remaining eight sites, with highly developed urbanization and high population density, were regarded as the other cluster. These sites were mainly affected by point source pollution of arsenic, which were derived from sewage and industrial waste water. While the influence of run off was not significant. The content of arsenic ranged from 2.72 to 71.5 mg·kg-1 in the surface sediment of the PRD, with the highest overweight multiples of 3.57, and the average concentration of 20.3 mg·kg-1. The potential ecological risk assessment results indicated that the concentration of arsenic in the surface sediment of the PRD were at low contamination levels, which were consistent with the geological accumulation index evaluation results. Combining these two methods can comprehensively evaluate arsenic biogeochemical behavior and its toxic effects to biota. Significant negative correlation was found between arsenic concentration inwater and that in sediments (r=0.356>r0.05 (1, 50)=0.273), which might due to the dilution, sedimentation and biochemical effects in the water systems.
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