Department of Soil Science Erosion and Land Protection, Institute of Soil Science and Plant Cultivation-State Research Institute, Czartoryskich 8, 24-100 Puławy, Poland.
Molecules. 2020 May 26;25(11):2470. doi: 10.3390/molecules25112470.
Polycyclic aromatic hydrocarbons (PAHs) exhibit persistence in soils, and most of them are potentially mutagenic/carcinogenic and teratogenic for human beings but also influence the growth and development of soil organisms. The PAHs emitted into the atmosphere are ultimately deposited (by dry or wet deposition processes) onto the soil surface where they tend to accumulate. Soil organic matter (SOM) plays an important role in the fate and transformation processes of PAHs, affecting their mobility, availability, and persistence. Therefore, the aim of this research was to investigate the influence of SOM fractional diversification (fulvic acids-FA, humic acids-HA, and humins-HN) on PAH availability and persistence in soils. Twenty soil samples ( = 20) were collected from upper horizons (0-30 cm) of agricultural soils exposed to anthropogenic emissions from industrial and domestic sources. The assessment of PAH concentrations included the determination of medium-molecular-weight compounds from the US EPA list: fluoranthene-FLA, pyrene-PYR, benz(a)anthracene-BaA, and chrysene-CHR. The assessment was conducted using the GC-MS/MS technique. Three operationally defined fractions were investigated: total extractable PAHs (TE-PAHs) fraction, available/bioavailable PAHs (PB-PAHs) fraction, and nonavailable/residual PAHs (RE-PAHs) fraction, which was calculated as the difference between total and available PAHs. TE-PAHs were analyzed by dichloromethane extraction, while PB-PAHs were analyzed with a hydrophobic β-cyclodextrin solution. SOM was characterized by total organic carbon content (Turin method) and organic carbon of humic substances including FA, HA, HN (IHSS method). Concentrations of PAHs differed between soils from 193.5 to 3169.5 µg kg, 4.3 to 226.4 µg kg, and 148.6 to 3164.7 µg kg for ∑4 TE-PAHs, ∑4 PB-PAHs, and ∑4 RE-PAHs, respectively. The ∑4 PB-PAHs fraction did not exceed 30% of ∑4 TE-PAHs. FLA was the most strongly bound in soil (highest content of RE-FLA), whereas PYR was the most available (highest content of PB-PYR). The soils were characterized by diversified total organic carbon (TOC) concentration (8.0-130.0 g kg) and individual SOM fractions (FA = 0.4-7.5 g kg, HA = 0.6-13.0 g kg, HN = 0.9-122.9 g kg). FA and HA as the labile fraction of SOM with short turnover time strongly positively influenced the potential ∑4 PAH availability (r = 0.56 and r = 0.52 for FA and HA, respectively). HN, which constitutes a stable fraction of organic matter with high hydrophobicity and poor degradability, was strongly correlated with ∑4 RE-PAHs (r = 0.75), affecting their persistence in soil.
多环芳烃（PAHs）在土壤中具有持久性，其中大多数对人类具有潜在的致突变性/致癌性和致畸性，但也会影响土壤生物的生长和发育。排放到大气中的 PAHs 最终通过（干或湿沉降过程）沉积到土壤表面，在那里它们倾向于积累。土壤有机质（SOM）在 PAHs 的归趋和转化过程中起着重要作用，影响其迁移性、可用性和持久性。因此，本研究的目的是研究 SOM 分馏（富里酸-FA、腐殖酸-HA 和胡敏素-HN）对土壤中 PAH 可用性和持久性的影响。从暴露于工业和家庭源人为排放的农业土壤上层（0-30 cm）采集了 20 个土壤样本（= 20）。PAH 浓度的评估包括测定美国环保署清单中的中分子量化合物：荧蒽-FLA、芘-PYR、苯并（a）蒽-BaA 和屈-CHR。评估使用 GC-MS/MS 技术进行。研究了三个操作定义的分数：总可提取 PAHs（TE-PAHs）分数、可利用/生物可利用 PAHs（PB-PAHs）分数和不可用/残留 PAHs（RE-PAHs）分数，其计算方法是总 PAHs 与可利用 PAHs 的差值。TE-PAHs 通过二氯甲烷萃取进行分析，而 PB-PAHs 则通过疏水性 β-环糊精溶液进行分析。SOM 通过总有机碳含量（都灵法）和包括 FA、HA、HN 在内的腐殖质有机碳（IHSS 法）进行表征。PAHs 浓度在土壤中差异很大，∑4 TE-PAHs、∑4 PB-PAHs 和∑4 RE-PAHs 分别为 193.5 至 3169.5 µg kg、4.3 至 226.4 µg kg 和 148.6 至 3164.7 µg kg。∑4 PB-PAHs 分数不超过∑4 TE-PAHs 的 30%。FLA 在土壤中结合最强（RE-FLA 含量最高），而 PYR 最具可用性（PB-PYR 含量最高）。土壤的总有机碳（TOC）浓度（8.0-130.0 g kg）和单个 SOM 分数（FA=0.4-7.5 g kg、HA=0.6-13.0 g kg、HN=0.9-122.9 g kg）差异很大。FA 和 HA 作为具有短周转时间的 SOM 易变部分，强烈地正向影响潜在的∑4 PAH 可用性（FA 和 HA 分别为 r=0.56 和 r=0.52）。HN 是一种具有高疏水性和低降解性的稳定有机物质组成部分，与∑4 RE-PAHs 强烈相关（r=0.75），影响其在土壤中的持久性。
