【作者】 陈华林；

【导师】 陈英旭；

【作者基本信息】 浙江大学 ， 环境工程， 2003， 博士

【摘要】 沉积物对有机污染物的不可逆吸附行为对有机污染物在水环境中的迁移、转化、归宿及毒性有着重要的影响。不可逆吸附是指污染物被吸附到沉积物或土壤固体颗粒后，按通常的方法，如溶剂浸提，不能将其提取出来的现象。不可逆吸附现象影响到环境质量标准的制定，污染修复效果以及污染物的潜在危害大小，是目前环境化学学科十分关注的一个研究领域。本研究针对这种不可逆吸附现象，用来源和性质不同的8种沉积物作为吸附剂，用菲和五氯酚（PCP）作为目标污染物，通过静态吸附实验和吸附动力学实验，定性定量地探讨了不同沉积物对有机污染物的吸附性能，并运用区室模型将吸附过程中不可逆和可逆吸附量的动态变化进行量化。通过对沉积物有机质组分含量和性质的测定，探讨了影响沉积物吸附性能的主要因素及作用机制。结论如下： 沉积物有机质含量是控制其吸附有机污染物能力的主要因素。菲和PCP在低浓度范围的吸附等温线成线性，在高浓度范围呈现一定程度的非线性，非线性吸附等温线可以用Freundlich方程进行拟合。菲的logK_oc为4.18±2.98，PCP的logK_oc为2.87±1.50，PCP的K_oc值还跟沉积物pH有关，关系式为logK_oc=-0.2129pH+4.431，r²=0.9049，这跟PCP在水中的离解有关。甲醇对菲和PCP没有明显的竞争吸附作用，结合线性吸附等温线的结果表明，沉积物吸附菲和PCP主要是以分配作用为主，表面吸附作用很弱，其中PCP由于有离子化的趋势，表面吸附作用比菲强。 菲和PCP吸附作用存在两段行为。吸附动力学实验结果表明，菲和PCP在吸附过程中分为两段，即一个快速吸附阶段之后接着是一个慢速吸附阶段。快速吸附阶段能在8h内达到吸附平衡，而慢速吸附阶段则一般在长达20d后才能达到平衡。解吸基本是快速过程，能在8h内达到平衡，长期的慢速解吸释放出来的量并不明显，大部分仍残留于固相。这表明解吸并不完全是吸附的可逆过程，这二者存在着不同的机制。 菲和PCP均存在着不可逆吸附现象。循环吸附解吸试验结果表明，吸附到固相的菲和PCP有相当一部分难以再解吸进入液相，即存在着不可逆吸附行为。其中，菲的不可逆吸附量明显比PCP大。菲的不可逆吸附量跟沉积物中富里酸的含量成正相关，可能是由于菲进入了山富里酸形成的分子孔洞中造成的。而解吸迟滞系数则表明脂蜡可能是引起PCP吸附迟滞效应的主要因素。当脂蜡占总有机质的比例越高，迟滞系数越大，即不可逆程度越大。慢速吸附过程可以用区室模型进行模拟，结果表明，在液相与团相达吸附平衡后，吸附的污染物仍然在进行着从可逆吸附相向不可逆吸附相转化。大多数沉积物表现出随吸附时间的延长，可逆吸附相的量降低，不可逆吸附相的量持续升高，但固相和液相总量的比例在吸附后期基本保持不变。通过实验验证，区室模型能较好地与实验结果保持一致，表明运用区室模型来模拟慢速吸附过程是可行的。 沉积物性质对其吸附菲和 PCP的性能有一定影响。沉积物各有机组分含量与快速吸附速率常数成显著正相关，与快速解吸速率常数成负相关。对菲和PCP快速吸附速率常数影响最大的是酸溶态和氧化物结合态HA的含量；酸溶态组分和脂蜡的含量对菲的快速解吸速率常数影响最大，胡敏素、氧化物结合态HA、钙结合FA对PCP的快速解吸速率常数影响最大。对菲慢速吸附速率常数的影响因素主要是酸溶态、胡敏素和脂蜡含量，成显著负相关；对PCP的慢速吸附常数，仅酸溶态组分含量与其成显著正相关，其他组分影响均不显著。 沉积物对菲和 PCP的吸附能力与各有机组分含量成显著的正相关。对菲Kd（分配系数）值影响最大的是胡敏素、氧化物结合态HA和氧化物结合态FA，对PCPKd影响最大的是CEC、钙结合态FA与钙结合态HA。这主要是由于沉积物对菲和PCP的吸附机理不同造成的，菲主要以分配作用进入胡敏素、与沉积物颗粒结合紧密的氧化物结合态组分，而PCP则在沉积物表面存在着大量的吸附行为，如与钙结合组分结合，与颗粒表面发生静电吸附作用等。对菲和PCP最大不可逆吸附量的影响均是氧化物结合态HA和胡敏素，与氧化物结合态HA和胡敏索有着更紧实的结构有关。 各有机组分能引起不同程度的不可逆吸附。与腐殖酸相比，脂蜡能引起更大程度的不可逆吸附。脂蜡具有类似玻璃质的结构，空间结构致密，疏水性强，不易变形，有机物在其内难以扩散，因而进入脂蜡的有机质不可逆程度大，是引起吸附迟滞效应的主要因素。FA比HA更易引起不可逆吸附。3种沉积物腐殖酸元素分析和红外光谱分析结果表明，FA比HA含有更多的含氧官能团和碳水化 n了／ 合物，主要为含一COOH的脂肪族物质。FA的一COOH和oH能通过氢键的形式 形成大小不一的孔洞，这些孔洞能容许象菲和 PCP这样的有机小分子进入，从 而将其封闭，形成不可逆吸附。 上覆水的性质对沉积物吸附菲和PCP也有一定影响。温度、pH、离子强度、 DOC四因素及其交互作用对沉积物吸附菲和PCP更多还原

【Abstract】 Sorption to natural solid is an underlying process affecting the transport, degradation, and biological activity of organic pollutants in the environment. Desorption of many organic pollutants from natural sediments has been observed to be biphasic, containing reversible and irreversible compartments. A fraction of the adsorbed contaminants desorbs reversibly, as expected, but there exists a second and distinct fraction that is resistant to desorption. Irreversible sorption of organic pollutants has attracted more attention in the past years because the irreversible behavior affected the sediment quality criteria, remediation efficiency and the potential danger of pollutants in natural water body.The overall objective of this research has been to explain what causes the desorption of chemicals in the sediments to be resistant and to understand the consequences with respect to sediment clean-up and how-clean-is-clean. In this research, eight sediments covering a wide range of organic carbon content from 0.54 to 36% were selected as sorbents, while phenanthrene and pentachlorophenol (PCP) were selected as model contaminants. Equilibrium sorption experiments and kinetics sorption process were carried out to invest the sorption properties of phenanthrene and PCP in sediments. For modeling the dynamic sorption process, compartment model was applied. Based on the conclusions of modeling for dynamic sorption experiments, correlation analysis between the sorption parameters and the sediment properties was carried out to find out the main fractions affected the irreversible sorption behaviors. The followings were the main results.The sorption capacity of sediment was determined by the organic carbon content of sediment. In relatively low concentration range, the isotherms of phenanthrene and PCP were linear, while in relatively high concentration range, the isotherms were nonlinear, which can be described with Freundlich equation. The partition coefficient (normalized to organic carbon) logKoc for phenanthrene was 4.18+2.98, and for PCP was 2.87+1.50. However, pH values of sediments can inflect the logKoc of PCP. The relation of logKoc and pH was logAToc=-0.2129pH+4.431, r2=0.9049, While thelogKoc of phenanthrene wasn’t inflected by pH. That was caused by the PCP slightly ionization in water. The ratio of ionized PCP in total amount was high at high pH, which decreased the sediment sorption capacity. When methanol and model contaminants were coexistent, no competitive sorption was observed, that suggested the partition process in sorption course.Sorption of model pollutants into sediments were biphasic, a fast sorption phase followed by a slow sorption phase. The equilibrium in fast phase reached in 8hrs, while equilibrium in slow phase would cost more than 20d. Likewise, desorption were biphasic, too, containing a fast phase no more than 8hrs, in which a small portion model pollutants adsorbed in sediment desorbed into aqueous phase quickly, however, the other portion seemed to be resistant to desorption. The results of multi-cycle sorption/desorption experiments showed that the irreversible sorption amount of phenanthrene for all sediments were larger than that of PCP. Hypothesis was presented that phenanthrene and PCP molecules sorbed into solid phase were captured by fulvic acid of sediment, which induced irreversible sorption. Therefore, conclusion was drawn that lipid fraction maybe was the main fraction to affect the hysteresis phenomenon, i.e., the higher the lipid percentage, the greater the HI value.From the results of modeling based on the compartment model, the amount of irreversible phase increased with the sorption time, while the reversible phase decreased, at the premise of equilibrium of aqueous phase concentration with total solid phase adsorbed amount. The modeling data was agreement to the experimental data in a rational range, which suggested the feasibility of compartment model for slow sorption process. But the hypothesis that the increased amount in irreversible phase comes from更多还原