Abstract:

In this paper, environmental data of heavy metals in the surface soil (0-20 cm) of 440 forest land in the Pearl River Delta were collected, and the soil ecological risk, spatial pattern, and formation of forestland in the Pearl River Delta were studied and analyzed by screening values and Hakanson potential ecological risk values. The study provided scientific support for maintaining the integrity and health level of natural ecosystems and constructing an integrated system of ecological security in the Guangdong-Hong Kong-Macao Greater Bay Area. The results showed that: (1) The contents of Cd, Hg, As, Pb, Cr, Cu, Ni and Zn in the forest land of the Pearl River Delta were 0.001-1.03, 0.01-0.92, 0.71-580, 4.79-520, 0.01-131, 0.02-192, 1.73-78.1 and 0.01-227 mg∙kg^-1, respectively. The average content was relatively low and the distribution was uneven; the coefficients of variation of As, Cd and Cu were higher; and the content was higher in some parts of areas. (2) The risk value assessment showed that the soil of forest land in the Pearl River Delta was at a low potential ecological risk level with no less than 73.43%. There was moderate potential ecological risk and strength potential ecological risk in some parts of the areas, mainly due to Hg and Cd. The screening value assessment indicated that most forest land soil in the Pearl River Delta might be affected by heavy metals (Mainly Cr and Hg). (3) The pattern analysis showed that the potential ecological risk of Cd in the central region of Pearl River Delta was higher; and the potential ecological risks of Hg in central and eastern woodland soil were higher. The pattern formation analysis showed that there might be different formation mechanisms for different heavy metals and different ecological risks; Cd was mainly affected by the migration of the Xijiang and Beijiang rivers, followed by dry and wet sedimentation; Hg was mainly affected by economic development and dry and wet sedimentation; and Cr was mainly affected by the high natural background value. (4) Hg and Cd were the key factors for soil ecological risk management in the Pearl River Delta region, followed by Cr and As. This study provided valuable information for the ecological control of soil pollution in the Pearl River Delta and the integrated layout of ecological security in the Guangdong-Hong Kong-Macao Greater Bay Area.

Key words: pearl river delta, forest soil, heavy metals, ecological risk assessment, regional ecology, distribution pattern, ecological reference value of soil

摘要：

收集珠江三角洲440个林地表层（0—20 cm）土壤重金属环境数据,通过筛选值和Hakanson潜在生态风险值对珠江三角洲林地土壤生态风险空间格局及形成进行研究分析,以期对统筹珠江三角洲生态土地利用及环境管控,维护自然生态系统的完整性和健康水平提供理论依据。研究结果表明,（1）珠江三角洲林地土壤重金属Cd、Hg、As、Pb、Cr、Cu、Ni、Zn质量分数范围分别为0.001—1.03、0.01—0.92、0.71—580、4.79—520、0.01—131、0.02—192、1.73—78.1、0.01—227 mg∙kg^-1,平均含量较低但分布不均匀,变异系数较大的为As、Cd、Cu,局部区域含量较高。（2）风险值评估显示,珠江三角洲林地土壤不少于73.43%处于低潜在生态风险水平,但局部土壤存在中度潜在生态风险至强度潜在生态风险,以Hg和Cd为主;筛选值评估显示,珠江三角洲大部分林地土壤可能受到重金属（以Cr、Hg为主）生态影响。（3）格局分析表明,珠江三角洲中部林地土壤Cd潜在生态风险较高,中部和东部林地土壤Hg潜在生态风险较高;格局形成分析显示,不同重金属及不同生态风险重金属的来源可能存在不同的形成机制,Cd主要受北江和西江水流迁移的影响,其次为干湿沉降,而Hg主要受经济开发及干湿沉降的影响,Cr则是由于自然本底值较高。（4）Hg和Cd元素是珠江三角洲区域土壤生态风险管控的关键因子,其次为Cr和As。该研究对珠江三角洲土壤污染生态管控与粤港澳大湾区生态安全一体化布局有较高的参考价值。

关键词: 珠江三角洲, 林地土壤, 重金属, 生态风险评估, 区域生态, 分布格局, 土壤生态基准值