State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
Environ Sci Pollut Res Int. 2011 Mar;18(3):346-54. doi: 10.1007/s11356-010-0379-y. Epub 2010 Aug 2.
Many rivers have to receive treated or untreated wastewater as the main water sources in the world, especially in the countries facing with water shortage. For instance, the Haihe and Huaihe River Basin, which are among areas facing crises for water resources in China, receive 33,400 million tons of wastewater per year. As the sediment has large capacity for sorbing hydrophobic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs), it can act as a natural repository for the contaminants. This means pollutants can release into water phase again under some conditions, such as resuspension, sediment dredging, etc. The objective of this research was to study the trends of PAH release from sediments in rivers receiving much wastewater, such as Yongding New River (YD), Northsewer (NS), and Southsewer (SS) from Haihe River Basin. These rivers received most of the wastewater from Tianjin, China and merge into Bohai Bay finally.
Sediments (namely YD, NS, and SS) were collected from Yongding New River, Northsewer, and Southsewer, respectively. The physical and chemical properties of the sediments, including particle size distribution, total organic carbon (TOC) and black carbon (BC) contents, elemental compositions, organic functional groups analyzed from Fourier transformed infrared (FTIR), and nuclear magnetic resonance (NMR) spectra, were characterized. PAH desorption from the sediments was measured with the Tenax shaken slurry desorption method.
The NS sediment had a greatly higher TOC and BC contents, while lower BC-to-TOC ratio than YD and SS sediments. NMR and FTIR analysis showed that aliphatic carbons were more abundant in NS sediment than SS sediment. The desorption experiments showed that PAHs desorbed more rapidly from YD and NS sediments than from SS sediment. PAH fraction desorbed after each interval during the experiment except 0.8 day was significantly correlated with PAH properties among all the three sediments.
The higher BC-to-TOC ratio in SS sediment corresponded to slower desorption rate and less desorption extent of PAHs from SS sediment among the three sediments. This probably could be explained by the extremely strong sorption ability of BC. It also proved that the sequestration of PAHs in sediment was not simply the result of higher organic carbon content.
Considering the physical and chemical characterization of the sediments and PAH desorption properties comprehensively, BC-to-TOC ratio was a more important factor controlling the behavior of PAHs in sediments than absolute TOC or BC content.
许多河流都将处理或未处理的废水作为主要水源，尤其是在水资源短缺的国家。例如，中国面临水资源危机的海河流域和淮河流域，每年接收 334 亿吨废水。由于沉积物对多环芳烃（PAHs）等疏水性有机污染物具有较大的吸附能力，因此可以作为污染物的天然储存库。这意味着在某些条件下，例如再悬浮、沉积物疏浚等，污染物可以再次释放到水相中。本研究的目的是研究接收大量废水的河流（如永定新河、北运河和南运河）中沉积物中 PAH 释放的趋势。这些河流接收了中国天津的大部分废水，最终汇入渤海湾。
分别从永定新河、北运河和南运河采集沉积物（分别称为 YD、NS 和 SS）。对沉积物的物理化学性质进行了表征，包括粒径分布、总有机碳（TOC）和黑碳（BC）含量、元素组成、傅里叶变换红外（FTIR）和核磁共振（NMR）谱分析的有机官能团。采用 Tenax 搅拌浆法测定了 PAH 从沉积物中的解吸。
NS 沉积物的 TOC 和 BC 含量较高，而 BC 与 TOC 之比低于 YD 和 SS 沉积物。NMR 和 FTIR 分析表明，NS 沉积物中脂肪族碳比 SS 沉积物中更丰富。解吸实验表明，YD 和 NS 沉积物中 PAHs 的解吸速度快于 SS 沉积物。实验过程中，每个间隔后的 PAH 馏分除 0.8 天外均与所有三种沉积物中的 PAH 性质显著相关。
SS 沉积物中较高的 BC/TOC 比值对应于 SS 沉积物中 PAHs 解吸速率较慢和解吸程度较低。这可能可以解释为 BC 具有极强的吸附能力。这也证明了 PAHs 在沉积物中的固定化不仅仅是由于较高的有机碳含量。
综合考虑沉积物的物理化学特性和 PAH 解吸特性，BC/TOC 比值是控制沉积物中 PAH 行为的比绝对 TOC 或 BC 含量更重要的因素。
