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作为一种典型的全氟化合物,全氟辛烷磺酸(PFOS)已被归类为一种新的持久性有机污染物[1-2]. PFOS具有很高的化学稳定性,不能被微生物和植物降解,因此对环境造成严重污染[3-5]. 到目前为止,已在水中检测到PFOS. 例如,从城市工厂和机场工业处理厂排放到美国旧金山湾的废水分别平均含有420 ng·L−1和560 ng·L−1 PFOS[6]. 在中国一家工厂的废水中发现了高浓度的PFOS[7],平均值达到1021 mg·L−1. 因此,去除PFOS并降低对水生环境的相关风险是一个重要的新兴话题.
人工湿地因其经济和能源成本低而被广泛用于废水处理. 人工湿地系统中污染物的去除主要基于基质吸附、拦截、植物吸收、富集和微生物降解. 人工湿地不仅可以去除重金属离子,还可以去除新出现的污染物[8-10]. 然而,人工湿地中全氟化合物(PFCs)的去除研究却很少. CHEN等[2]研究发现,中等规模的人工湿地对水体中全氟辛酸(PFOA)和PFOS的去除效率分别为77%—82%和90%—95%,其中植物萃取和土壤吸附是最重要的去除机制. YIN等[9]报告称,在芦苇床实验中,全氟烷基酸(PFAAs)的去除率最高可达42%—49%,这可能是由土壤和沉积物的吸附以及植物的吸收作用导致.
已有研究表明,人工湿地对单一的营养盐或PFOS污染的水体具有一定的修复效果[11-12],但关于其对于含有这些污染物复合污染水体的研究较少. 基于此,本研究以表面流人工湿地为对照,构建多级垂直流人工湿地,评估人工湿地对营养盐和PFOS复合污染水体的处理情况,并进一步探索两者在湿地水、土壤和植物中的分布和迁移,同时重点研究了PFOS对水体中总氮(TN)、氨氮(NH3-N)、总磷(TP)和化学需氧量(COD)的影响,以期为人工湿地在水体治理修复工程中的应用提供参考.
多级人工湿地对复合污染水体中营养盐和PFOS的去除
Removal effect of nutrient salts and perfluoroalkyl acids in compound contaminated water by multi-stage constructed wetland
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摘要: 选取表面流人工湿地和垂直潜流人工湿地为研究对象,通过露天实验研究了不同湿地类型对复合污染水体中营养盐和PFOS的去除效果. 结果表明,3种湿地对复合污染水体中营养盐和PFOS均具有较好的去除能力,且不同湿地类型对各污染物的去除效果有所差异. 高浓度(100 μg·L−1)PFOS抑制风车草生长,SFCW植物PFOS含量达到的实验最高值,为(181.93±8.28) μg·g−1;低浓度(1 μg·L−1)PFOS促进了风车草的生长,VFCW2植物总生物量达到的实验最高值,为(1130.33±36.98) g;VFCW2对营养盐和PFOS的去除表现最优,在高浓度(100 μg·L−1)PFOS下,PFOS去除率仍然可达95.87%—99.86%;低浓度(1 μg·L−1)PFOS强化了VFCW1和VFCW2对NH3-N的去除,去除率分别为60%—65%和68%—72%. PFOS的去除主要取决于人工湿地的土壤吸附和植物吸收,SFCW、VFCW1和VFCW2土壤PFOS吸附占比分别为(50.86±1.23)%—(56.32±2.35)%、(62.13±2.23)%—(75.28±3.01)%和(64.71±3.56)%—(76.96±1.98)%,均高于植物PFOS吸收占比(7.51±0.66)%—(35.84±2.36)%.Abstract: The study selected the surface flow constructed wetland and vertical subsurface flow constructed wetland as research object. Removal effects of different wetland types on nutrients and PFOS in compound polluted water were studied through open-air experiments. The results show that the three wetlands have good removal capacity of nutrients and PFOS in compound polluted water, and the removal effects of different wetland types were different. High concentration (100 μg·L−1) PFOS inhibited the growth of windmill grass, and the PFOS content of SFCW plants reached the highest in the experiment, which was (181.93±8.28) μg·g−1. Low concentration (1 μg·L−1) PFOS promoted the growth of windmill grass, and the total biomass of VFCW2 reached the highest in the experiment, which was (1130.33±36.98) g. VFCW2 was the best in the removal of nutrients and PFOS. Under high concentration (100 μg·L−1) PFOS, the removal rate of PFOS could still reach 95.87%—99.86%. Low concentration (1 μg·L−1) PFOS enhanced the removal of NH3-N by VFCW1 and VFCW2, with removal rates of 60%—65% and 68%—72% respectively. The removal of PFOS mainly depended on the soil adsorption and plant absorption of constructed wetland. The proportion of soil PFOS adsorption of SFCW, VFCW1 and VFCW2 was (50.86±1.23)%—(56.32±2.35)%, (62.13±2.23)%—(75.28±3.01)% and (64.71±3.56)%—(76.96±1.98)%, which were higher than that of plant PFOS absorption (7.51±0.66)%—(35.84±2.36)%.
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Key words:
- constructed wetland /
- compound contaminated water /
- nutrients salts /
- PFOS
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表 1 模拟生活污水特性
Table 1. Characteristics of simulated domestic sewage
pH COD/(mg·L−1) TN/(mg·L−1) TP/(mg·L−1) NH3-N/(mg·L−1) 浓度
Concentration6.88±0.31 175.22±10.68 36.42±1.68 9.31±0.56 20.41±1.79 表 2 不同PFOS浓度下湿地植物的总生物量
Table 2. Total biomass of wetland plants under different PFOS concentrations
PFOS /(µg·L−1) SFCW/g VFCW1/g VFCW2/g 0 734.90±23.64 772.81±15.47 891.41±32.43 1 864.51±30.98 1022.76±31.84 1130.33±36.98 100 597.25±18.56 630.63±25.43 766.04±25.11 表 3 不同湿地处理组出水稳定后营养盐的去除率
Table 3. Removal rate of nutrients concentration in different wetland treatment groups
PFOS /(µg·L−1) COD/% NH3-N/% TN/% TP/% SFCW 0 37—41 41—45 51—56 34—38 1 36—40 37—42 48—53 32—35 100 33—37 33—36 43—47 30—34 VFCW1 0 58—64 50—54 68—72 58—62 1 56—60 60—65 51—55 57—61 100 48—53 53—58 49—53 56—60 VFCW2 0 62—68 58—64 70—76 61—65 1 59—64 68—72 55—59 58—62 100 55—60 55—60 54—57 57—63 表 4 实验运行结束后土壤和植物中的PFOS平均含量
Table 4. Average content and of PFOS in soil and plants after the experiment
处理组
Processing groupPFOS浓度/(µg·L−1)
PFOS concentration土壤含量/(µg·g−1)
Content in soil植物含量/(µg·g−1)
Content in plantSFCW 1 0.017±0.003 2.09±0.06 100 1.85±0.07 181.93±8.28 VFCW1 1 0.021±0.002 1.49±0.04 100 2.47±0.10 60.02±1.25 VFCW2 1 0.022±0.001 1.40±0.05 100 2.53±0.11 76.06±2.36 -
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