北部湾防城港沿岸土壤^（137）Cs背景值及表层分布特征

^（137）Cs reference inventory and its distribution in surface soil along the Fangchenggang coastal zone of Beibu Gulf

在北部湾防城港沿岸采集土壤样品,通过测量样品137Cs比活度及有机质含量,确定了137Cs背景值,分析表层土壤中137Cs分布特征,并探讨样品中137Cs活度与有机质含量的关系。结果表明:研究区土壤中137Cs背景值为626±15 Bq/m2,自然因素和人为活动对137Cs在海岸带表层土壤中的再分配起到重要作用,不同表层样中137Cs比活度高低表现为:自然林地>水稻田>旱田>草地>河口海湾。把研究区土壤表层样及P01剖面样中137Cs含量与有机质含量进行相关性分析,结果表明:两者相关性显著,相关系数分别为0.414和0.732。通过探讨研究区137Cs背景值及沿岸表层土壤137Cs分布特征,可为进一步定量研究北部湾沿岸土壤侵蚀和堆积状况以及评价防城港红沙核电站运行后对环境的影响提供科学依据。

The background values of137 Cs along the coast of the Beibu Gulf have not been sufficiently presented in China so far. This thesis collected 55 surface samples and 1 profile sample in the Beibu Gulf. The specific activity of137 Cs and organic contents of individual sample were tested and the accumulation amount of137 Cs in the section sample was calculated.The background value of137 Cs in the research area was finally determined. The thesis also analyzed the distribution features of137 Cs in surface soil along the Fangchenggang coastal zone of the Beibu Gulf. The relationship between the specific activity of137 Cs and organic contents in the sample soil was discussed as well. The findings showed that the background value of137 Cs in the soil of the research area was 626 ± 15 Bq/m2, and the atmospheric precipitation of137 Cs accorded with the precipitation condition of137 Cs in the northern hemisphere. By comparing the background values of137 Cs in multiple places within China, it is suggested that the variance among the background values of137 Cs in regions at the same latitude can mainly be attributed to rainfall. Moreover, the spacial distribution variance of latitude zone, climate factors like typhoon and the particularity of geographic position also have great potential to influence the precipitation of137 Cs. The research on the specific activity of the surface samples and the distribution of sampling sites suggested that natural factors and human activities played an important role in the redistribution of137 Cs in soil. The specific activity of137 Cs in different surface samples exhibited the following order from high to low: natural forest land, paddy field, dry land, grassland, and estuary and gulf. A Pearson's correlation analysis was conducted and significant corelation was found between the values of137 Cs content and organic contents in the surface samples and P01 sediment core, with the corelation coefficients being respectively0.414 and 0.732.Discussing the background value of137 Cs in the Fangchenggang coastal zone of the Beibu Gulf and the distribution features of137 Cs in surface soil along the coast can promote further quantitative research on soil erosion and accumulation along the coast of the Beibu Gulf as well as provide scientific evidence for the evaluation of the environmental impact of the Red Sand Plant.