典型城区大气干湿沉降重金属对地表径流的污染机理

The dry and wet settlement of the atmosphere is the most widely distributed and important carrier of the urban non-point source pollution. Studying the contribution of two settlement modes to the heavy metal pollution of surface runoff and the morphological characteristics of heavy metal pollutants in surface runoff are of great significance for effective control of urban surface runoff pollution. The construction of the central city of the state has formed a new urban functional pattern, which has a significant impact on the air dry wet settlement flux and its rainfall runoff pollution.Using Zhengzhou city as an example,the purpose of this paper is to study the heavy metal flux and its influencing factors in the dry and wet atmosphere of different urban functional areas.Secondly, combined with artificial rainfall control experiments, we simulated the heavy metal behavior of atmospheric dry and wet deposition under multiple factors. And then,this article also explained the contribution of heavy metals in dry and wet deposition to runoff pollutants. What’s more,the distribution characteristics of particulate and dissolved heavy metals in surface runoff was analyzed, and the contribution model of dry and wet settlement of different forms of heavy metal pollutants was also constructed. In this way,this research found the quantitative connection between the two atmospheric settlement models and the occurrence states of two heavy metal pollutants. Besides,the paper can also reveal the mechanism of heavy metal pollution to the urban surface runoff and enrich the research connotation of surface runoff pollution. This results provide a scientific basis for the source control and terminal treatment of heavy metals in urban waters.

大气干湿沉降是引起城市面源污染的分布最为广泛、最重要的载体，研究两种沉降模式对地表径流重金属污染的贡献以及形成地表径流中重金属污染物的形态特征，对有效控制城市地表径流污染有着重要的意义。国家中心城市建设形成新的城市功能格局，对大气干湿沉降通量及其降雨径流污染产生重大影响。以郑州市为例，研究不同城市功能区大气干湿沉降重金属通量及其影响因素，结合人工降雨控制实验模拟多因素影响下大气干湿沉降重金属行为，阐明大气干、湿沉降重金属对地表径流污染物的贡献比重，分析地表径流中颗粒态与溶解态重金属污染物赋存特征，构建不同形态重金属污染物的干湿沉降贡献模型，以期实现大气两种沉降模式与两种重金属污染物赋存状态的定量联系，揭示大气干湿沉降重金属对城市地表径流的污染机理，丰富地表径流污染研究内涵。研究结果为城市水体重金属的源头控制和末端治理提供科学依据。

以郑州市为研究区域，对城市不同功能区内道路及高层灰尘样本进行收集，分析重金属污染特征并评估污染水平及潜在的生态风险，探究城市灰尘金属元素的来源及贡献；同时以径流小区试验和人工控制试验为基础，分析了大气干湿沉降重金属在降雨冲刷过程中的迁移转化特征；在此基础上，分析了大气干湿沉降中颗粒态重金属和溶解态重金属对地表径流的污染贡献以及大气干、湿沉降重金属对地表径流的污染贡献，揭示了典型城区大气干湿沉降重金属对地表径流的污染机理。结果显示：郑州市地表街尘重金属中，颗粒态重金属和溶解态重金属的污染特征具有显著差别。针对颗粒态重金属，除 Ni 和 Cr 外，其他重金属的平均浓度均高于背景值；针对溶解态重金属，Hg、Cd 和 Pb 处于金属中最低浓度范围内，而Cu 和 Zn 是浓度最高的金属。对地表径流的贡献中，在5种重金属(Cr、Cu、Ni、Pb、Zn)中，颗粒态重金属污染分别是溶解态重金属污染的83.79、14.98、11.25、6.84、71.84倍，颗粒态重金属仍然是径流污染的主要来源。大气湿沉降虽然随着对地表径流污染产生污染，但是其污染较大气干沉降随降雨冲刷的重金属污染程度要小。研究结果丰富了地表径流污染的研究内容，为城市水体重金属的源头控制和末端治理提供科学依据。