報告書番号

T00018

タイトル（和文）

都市大気中の水銀の発生源と粒子状水銀の生成機構

タイトル（英文）

Emission sources of mercury and formation mechanism of particulate mercury in the urban atmosphere

概要 （図表や脚注は「報告書全文」に掲載しております）

都市大気中の水銀の発生源としてごみ焼却に着目し、当所狛江研究所において大気中の粒子状水銀濃度とごみ焼却粒子の指標となる鉛濃度との関係を調べた。その結果、粒子状水銀濃度の変化は、鉛濃度と気温の両方の変化によって概ね説明できることがわかった。このことは、ごみ焼却によって大気に排出されたガス状水銀の一部が、その直後に温度の急激な低下によってごみ焼却粒子に吸着したためと理解できる。このように、鉛、カドミウム、亜鉛、ヒ素の場合と同様に、都市大気中の水銀は主としてごみ焼却によって排出されており、粒子状水銀の濃度はその排出量に強く関係付けられる。さらに、ガス－粒子間における水銀の分配を熱力学的に解析した結果、粒子状水銀の生成はごみ焼却粒子へのガス状金属水銀の物理吸着によるものであり、両者は吸着平衡の状態にあると推定される。

概要 （英文）

In this study, we focused on the mercury emissions from municipal solid waste (MSW) incineration in urban areas and the formation mechanism for particulate mercury in the atmosphere. In order to evaluate the contribution from MSW incineration for mercury, first we investigated the relationship between the particulate mercury concentration and the concentration of lead, a marker element for particles from MSW incineration, in the atmosphere at the western Tokyo metropolitan area (Komae Research laboratory, CRIEPI). The results showed that changes in particulate mercury concentration were correlated with changes in lead concentration and air temperature. This supports the hypothesis that some of the gaseous mercury from MSW incinerators was adsorbed onto incinerator particles in the atmosphere due to an abrupt decrease in temperature immediately after the emission. Similar to the cases for lead, cadmium, zinc and arsenic which have been previously investigated, emissions from MSW incineration can account for the major portion of the mercury in the urban atmosphere. Also, it is likely that the particulate mercury concentration in the urban atmosphere is closely related to the mercury emission from MSW incinerators. Next, we analyzed thermodynamically the distribution of mercury between gas and solid phases in order to obtain more knowledge on the formation mechanism of particulate mercury in the atmosphere. The particulate mercury may often be the major form of the mercury deposited from the atmosphere because of its short atmospheric lifetime. From the thermodynamic analysis, it was inferred that the formation of particulate mercury is governed by physical adsorption of gaseous metallic mercury onto incinerator particles, and that the adsorption equilibrium for gaseous and particulate mercury has been established in the atmosphere.

報告者

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