中国長江下流域の支流域における多環芳香族炭化水素（PAH）の分布・発生源・リスク評価

[Distribution, Sources, and Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Tributary Waters of the Lower Reaches of the Yangtze River, China].

• Tian-Qi Jia
• Rong-Rong Lei
• Xiao-Lin Wu
• Tao-Tao Ni
• Shu-Rui Sun
• Wei Guo
• Wen-Bin Liu

抄録

揚子江下流域は中国の化学工業団地の典型的な集積地である。化学企業の生産過程で排出される多環芳香族炭化水素（PAH）は、大気沈着や表層流出を経て支流水域に流入し、最終的に長江に合流する。本研究では、長江の支流水域で採取した一連の代表的な水試料中のPAHの分布特性、発生源分析、生態学的リスク評価について検討した。サンプル中のPAHモノマーは主に低環状のものであった。その結果、PAHの総濃度は37.27～285.88ng-L、平均値は78.31ng-Lであり、PAHのモノマー濃度は0～61.35ng-Lであった。検出率が最も低かったのはベンゾ[k]フルオランテンとベンゾ[a]ピレンで、検出率は75%であった。有害なPAHモノマーとしては、ベンゾ[a]ピレンの濃度は0～11.08ng-Lであった。中国の「飲料水源水質基準（CJ 3020-1993）」によると、無錫市近郊の水試料（S12）中のベンゾ[a]ピレン濃度は飲料水基準の限界値（10 ng-L）を超えていた。世界のいくつかの典型的な地域の河川におけるPAHの総濃度と比較して、本研究では、PAHの濃度は総じて低～中程度のレベルであった。比例法および主成分分析の発生源分析結果によると、水中のPAHs濃度は主に化石燃焼、自動車の排気ガス、化学物質の排出の影響を受けていることがわかった。調査地域におけるPAH類の潜在的な生態系リスクを評価するために、リスク商（RQ）を用いた。その結果、DBAモノマーのほか、残りのモノマーの相対量（RQ）（複製）値が1以上、すべてのモノマーのRQ（MPCs）値が1未満であり、水試料の生態系リスクは中程度のレベルにあることがわかった。長期的な環境曝露の観点から、これ以上の汚染を防ぐために適切な管理策を検討する必要がある。この結果は、長江下流域の化学工業団地のPAHリスク評価や汚染対策の参考となる。

The lower reaches of the Yangtze River are a typical gathering place of chemical industrial parks in China. Polycyclic aromatic hydrocarbons (PAHs) emitted in the production process of chemical enterprises enter the tributary water body through atmospheric deposition and surface runoff, and finally merge into the Yangtze River. In this study, the distribution characteristics, source analysis, and ecological risk assessment of PAHs in a series of typical water samples collected in the tributary waters of the Yangtze River were studied. PAH monomers in the samples were mainly low-ring. The total concentration of PAHs was in the range of 37.27 to 285.88 ng·L with a mean value of 78.31 ng·L, while the monomer concentration of PAHs ranged from 0 to 61.35 ng·L. The lowest detection rate was benzo[k] fluoranthene and benzo[a] pyrene at 75%. As a toxic PAH monomer, the concentration of benzo[a] pyrene ranged from 0 to 11.08 ng·L. According to "Water Quality Standards for Drinking Water Sources (CJ 3020-1993)" of China, the concentration of benzo[a] pyrene in a water sample (S12) located near Wuxi City exceeded the limit of drinking water standards (10 ng·L). Compared with the total concentration of PAHs in rivers in some typical regions of the world, the concentration of PAHs in this study was generally at low to moderate levels. According to the source analysis results of the ratio method and principal component analysis, the concentration of PAHs in water was mainly affected by fossil combustion, automobile exhaust, and chemical emissions. To assess the potential ecosystem risk of PAHs in the investigated area, the risk quotient (RQ) was used. In addition to the DBA monomer, the relative quantities (RQs) (replication) of the remaining monomers were greater than 1, and the RQ (MPCs) values in all the monomers were less than 1, indicating that the ecological risk of water samples was at a medium level. From the perspective of long-term environmental exposure, appropriate control measures should be considered to prevent further pollution. The results can provide reference for PAH risk assessment and pollution control of chemical industrial parks in the lower reaches of the Yangtze River.