Air Quality Research Division, Environment and Climate Change Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada.
Air Quality Research Division, Environment and Climate Change Canada, 4905 Dufferin Street, Toronto, Ontario, M3H 5T4, Canada.
Environ Pollut. 2021 Feb 15;271:116232. doi: 10.1016/j.envpol.2020.116232. Epub 2020 Dec 13.
Polycyclic aromatic compounds (PACs) in Canadian air and deposition were examined at the national scale for the first time in over twenty-five years. Air concentrations spanned four orders of magnitude, and were highest near industrial emitters and lowest in the Arctic. Declines in unsubstituted PAHs were observed at locations close to industrial facilities that had reduced emissions, but trends elsewhere were modest or negligible. Retene concentrations are increasing at several locations. Ambient concentrations of benzo[a]pyrene exceeded Ontario's health-based guideline in many urban/industrial areas. The estimated toxicity of the ambient PAC mixture increased by up to a factor of six when including compounds beyond the US EPA PAHs. Knowledge of PAC deposition is limited to the Laurentian Great Lakes and Athabasca Oil Sands regions. The atmosphere remained a net source of PAHs to the Great Lakes, though atmospheric inputs were decreasing with halving times of 26-30 years. Chemical transport modelling substantially overestimated wet deposition, but model performance is unknown for dry deposition. Sources from Asia, Europe and North America contributed to Arctic and Sub-Arctic concentrations, whereas transboundary or long-range transport have not been assessed outside Canada's north. Climate-related impacts from re-emission and forest fires were implicated in maintaining air concentrations in the high Arctic that were not consistent with global emissions reductions. Industrial emission decreases were substantial at the national scale, but their influence on the environment was limited to areas near relevant facilities. When examined through the lens of ambient levels at the local scale, evidence suggested that contributions from residential wood combustion and motor vehicles were smaller and larger, respectively, than those reported in national inventories. Future work aimed at characterizing PACs beyond the EPA PAHs, improving measurement coverage, elucidating deposition phenomena, and refining estimates of source contributions would assist in reducing remaining knowledge gaps about PACs in Canada.
多环芳烃（PACs）在加拿大空气和沉降物中的研究在 25 年多以来首次在全国范围内进行。空气浓度跨越了四个数量级，在工业排放源附近最高，在北极地区最低。在靠近工业设施的地方，观察到未取代的多环芳烃排放量下降，但其他地方的趋势则较为温和或可以忽略不计。几种地点的 Retene 浓度正在增加。在许多城市/工业区，环境中苯并[a]芘的浓度超过了安大略省的基于健康的指导方针。当包括美国环保署多环芳烃以外的化合物时，环境中多环芳烃混合物的估计毒性增加了多达六倍。PAC 沉降的知识仅限于 Laurentian 大湖和 Athabasca 油砂地区。尽管大气输入量随着半衰期为 26-30 年而减少，但大气仍然是大湖地区多环芳烃的净来源。化学输送模型大大高估了湿沉降，但对干沉降的模型性能尚不清楚。来自亚洲、欧洲和北美的来源对北极和亚北极地区的浓度有贡献，而跨境或长程传输在加拿大北部以外地区尚未进行评估。再排放和森林火灾的气候相关影响被认为是维持高北极地区空气浓度的原因，这些浓度与全球排放量减少不一致。在全国范围内，工业排放量大幅下降，但它们对环境的影响仅限于与相关设施相关的地区。从当地尺度上的环境水平来看，有证据表明，住宅木材燃烧和机动车的贡献分别小于和大于国家清单中报告的贡献。未来的工作旨在描述美国环保署多环芳烃以外的多环芳烃，提高测量覆盖率，阐明沉降现象，并改进源贡献的估计，这将有助于减少加拿大多环芳烃方面的知识空白。
