Remediation actions by a risk assessment approach : A case study of mercury contamination

• Published in: Water, air, and soil pollution air, and soil pollution, 2005-11, Vol.168 (1-4), p.187-212
• Main Authors: SAPONARO, Sabrina, SEZENNA, Elena, BONOMO, Luca
• Format: Article
• Language: English
• Subjects: Applied sciences; Contaminants; Contamination; Decontamination. Miscellaneous; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Environmental conditions; Environmental monitoring; Exact sciences and technology; Geographical distribution; Groundwater; Groundwater management; Groundwater pollution; Inhalation; Leaching; Mercury; Pollution; Pollution, environment geology; Public health; Remediation; Risk assessment; Soil and sediments pollution; Soil pollution; Soil remediation; Speciation; Subsoils; Vapors; Water protection
• ISSN: 0049-6979; 1573-2932
• DOI: 10.1007/s11270-005-1248-z

The risk assessment procedure for identifying the remediation actions which may be adopted at a mercury contaminated site, when the plants are upgraded in the future, is proposed. The potentially active exposure/migration pathways in the future arrangement of the area will be due to Hg contaminated subsoil as a primary source (vapor inhalation and groundwater leaching) and to groundwater as a possible secondary source (transport to the point of compliance). The data of mercury concentration in the soil were acquired through environmental monitoring campaigns, and were processed to establish the three-dimensional distribution of contamination in subsoil, to locate sources and to define their geometrical and chemical characteristics. Speciation tests of mercury in the soil indicated that the most abundant species present were poorly leachable under the site-specific environmental conditions, confirming the coefficient distribution value obtained by the leaching tests. Analytical and numerical fate and transport modeling tools were used to locate digging zones in the contaminated subsoil, so as to reduce the possible groundwater contaminant loading and to avoid the down-gradient exceeding the concentration limit according to regulations. Remediation actions additional to civil works were required, which consists of soil digging within one contamination source, for about 22,200 m^sup 3^ of soil. In order to evaluate the Hazard Index (HI) for human receptors due to Hg vapor inhalation, the air concentration of volatile mercury at the exposure point was estimated, based on direct measurements carried out at the site. Simulation gave HI values below 1 for all tested scenarios, suggesting that public health is protected without any additional actions to the already scheduled plant upgrading and digging for groundwater protection.[PUBLICATION ABSTRACT]