Meierdierks Jana, Zarfl Christiane, Beckingham Barbara, Grathwohl Peter
Center for Applied Geosciences, University of Tübingen, Tübingen 72076, Germany.
Department of Geology and Environmental Geosciences, College of Charleston, Charleston, South Carolina 29424, United States.
ACS Environ Au. 2022 Sep 27;2(6):536-548. doi: 10.1021/acsenvironau.2c00015. eCollection 2022 Nov 16.
Long-term accumulation in the soils of ubiquitous organic pollutants such as many polycyclic aromatic hydrocarbons (PAHs) depends on deposition from the atmosphere, revolatilization, leaching, and degradation processes such as photolysis and biodegradation. Quantifying the phase distribution and fluxes of these compounds across environmental compartments is thus crucial to understand the long-term contaminant fate. The gas-phase exchange between soil and atmosphere follows chemical fugacity gradients that can be approximated by gas-phase concentrations, yet which are difficult to measure directly. Thus, passive sampling, measured sorption isotherms, or empirical relationships to estimate sorption distribution have been combined in this study to determine aqueous (or gas) phase concentrations from measured bulk concentrations in soil solids. All these methods have their strengths and weaknesses but agree within 1 order of magnitude except for passive samplers employed in soil slurries, which estimated much lower concentrations in soil water and gas likely due to experimental artifacts. In field measurements, PAH concentrations determined in the atmosphere show a pronounced seasonality with some revolatilization during summer and gaseous deposition during winter, but overall dry deposition dominates annual mean fluxes. The characteristic patterns of PAHs in the different phases (gas phase, atmospheric passive samplers, bulk deposition, and soil solids) confirm the expected compound-specific distribution pattern and behavior. Since revolatilization fluxes in summer are only minor and wet and dry deposition is ongoing, our results clearly show that the PAH loads in topsoils will continue to increase.
许多多环芳烃（PAHs）等普遍存在的有机污染物在土壤中的长期积累取决于大气沉降、再挥发、淋溶以及光解和生物降解等降解过程。因此，量化这些化合物在不同环境介质间的相分布和通量对于理解污染物的长期归宿至关重要。土壤与大气之间的气相交换遵循化学逸度梯度，该梯度可用气相浓度近似，但难以直接测量。因此，本研究结合了被动采样、测量的吸附等温线或估算吸附分布的经验关系，以便根据土壤固体中测得的总浓度确定水相（或气相）浓度。所有这些方法都各有优缺点，但除了用于土壤泥浆的被动采样器外，其他方法在一个数量级内的结果是一致的，被动采样器估算的土壤水和气体中的浓度可能因实验假象而低得多。在实地测量中，大气中测定的PAH浓度呈现出明显的季节性，夏季有一些再挥发，冬季有气态沉降，但总体而言干沉降主导年平均通量。不同相（气相、大气被动采样器、总沉降和土壤固体）中PAHs的特征模式证实了预期的化合物特定分布模式和行为。由于夏季的再挥发通量较小，且干湿沉降持续存在，我们的结果清楚地表明表层土壤中的PAH负荷将继续增加。
