长江下游支流水体中多环芳烃的分布及生态风险评估

长江下游地区是我国一个典型的化学工业园区聚集地,化工园区企业生产过程中产生和排放的多环芳烃通过大气沉降、地表径流等方式进入支流水体,并最终汇入长江.本研究选择了典型的支流水体,开展了多环芳烃的分布特征、源解析和生态风险评估研究.结果表明多环芳烃单体以低环为主,总浓度为37.27～285.88 ng·L~(-1),平均值为78.31 ng·L~(-1).PAHs单体浓度范围0～61.35 ng·L~(-1),检出率最低单体为苯并[k]荧蒽和苯并[a]芘,其检出率均为75%.苯并[a]芘是毒性当量因子最大的PAHs,其浓度范围为0～11.08 ng·L~(-1).根据我国《生活饮用水水源水质标准》(CJ 3020-1993)规定,饮用水中苯并[a]芘的限值为10 ng·L~(-1),其中研究区域内无锡市的一个水样(S12)中浓度超出了标准限值,长江下游支流水体的PAHs浓度总体处于低至中等的污染水平.根据比值法和主成分分析的源解析结果,水体中多环芳烃主要受化工排放、汽车尾气的影响,还有部分来自燃煤.生态风险评估结果显示,水体的生态风险处于中等水平,从长期的环境暴露角度出发,应当考虑采取相应地控制措施,防止进一步污染.研究结果可为长江下游支流水环境中多环芳烃风险评估以及化工园区的污染控制提供参考.     

Influence of aeration intensity on the performance of A/O-type sequencing batch MBR system treating azo dye wastewater

Among the numerous parameters affecting the membrane bioreactor (MBR) performance, the aeration intensity is one of the most important factors. In the present investigation, an anoxic/aerobic-type (A/O-type) sequencing batch MBR system, added anoxic process as a pretreatment to improve the biodegradability of azo dye wastewater, was investigated under different aeration intensities and the impact of the aeration intensity on effluent quantity, sludge properties, extracellular polymeric substances (EPS) amount generated as well as the change of permeation flux were examined. Neither lower nor higher aeration intensities could improve A/O-type sequencing batch MBR performances. The results showed 0.15 m³·h⁻¹ aeration intensity was promising for treatment of azo dye wastewater under the conditions examined. Under this aeration intensity, chemical oxygen demand (COD), ammonium nitrogen and color removal as well as membrane flux amounted to 97.8%, 96.5%, 98.7% and 6.21 L·m⁻²·h⁻¹, respectively. The effluent quality, with 25.0 mg·L⁻¹COD, 0.84 mg·L⁻¹ ammonium nitrogen and 8 chroma, could directly meet the reuse standard in China. In the meantime, the sludge relative hydrophobicity, the bound EPS, soluble EPS and EPS amounts contained in the membrane fouling layer were 70.3%, 52.0 mg·g⁻¹VSS, 38.8 mg·g⁻¹VSS and 90.8 mg·g⁻¹VSS, respectively, which showed close relationships to both pollutant removals and membrane flux.     

Uptake and accumulation of phenanthrene and pyrene in spiked soils by Ryegrass(Lolium perenne L.)

Phytoremediation has long been recognized as a cost-effective method for the removal of polycyclic aromatic hydrocarbons （PAHs） from soil. A study was conducted to investigate the uptake and accumulation of PAHs in root and shoot of Lolium perenne L. Pot experiments were conducted with series of concentrations of 3.31-378.37 mg/kg for phenanthrene and those of 4.22-365.38 mg/kg for pyrene in a greenhouse. The results showed that both ryegrass roots and shoots did take up PAHs from spiked soils, and generally increased with increasing concentrations of PAH in soil. Bioconcentration factors（BCFs） of phenanthrene by shoots and roots were 0.24- 4.25 and 0.17-2.12 for the same treatment. BCFs of pyrene by shoots were 0.20-1.5, except for 4.06 in 4.32 mg/kg treatment, much lower than BCFs of pyrene by roots （0.58-2.28）. BCFs of phenanthrene and pyrene tended to decrease with increasing concentrations of phenanthrene and pyrene in soil. Direct uptake and accumulation of these compounds by Lolium perenne L. was very low compared with the other loss pathways, which meant that plant-promoted microbial biodegradation might be the main contribution to plant-enhanced removal of phenanthrene and pyrene in soil. However, the presence of Lolium perenne L. significantly enhanced the removal of phenanthrene and pyrene in spiked soil. At the end of 60 d experiment, the extractable concentrations of phenanthrene and pyrene were lower in planted soil than in non-planted soil, about 83.24%-91.98% of phenanthrene and 68.53%-84.10% of pyrene were removed from soils, respectively. The results indicated that the removal of PAHs in contaminated soils was a feasible approach by using Lolium perenne L.     

基于GIS和PMF模型的石嘴山市土壤多环芳烃空间分布及来源解析

随着城市化和工业化进程加速,城市土壤多环芳烃（PAHs）含量及污染状况受到广泛关注.以石嘴山市为例,分析8个城市功能区156个表层土壤（0~20 cm）样品PAHs含量的空间分布特征,运用单因子指数、内梅罗综合指数和终生癌症风险增量模型评价土壤PAHs污染状况,利用正定矩阵因子分解模型（PMF）对PAHs来源进行解析.结果表明,石嘴山市表层土壤PAHs总含量均值为489.82 ng·g^-1,除芘（Pyr）外的15种PAH单体变异系数均大于100%,属强变异;不同功能区土壤PAHs含量呈现出：交通区（1217.61 ng·g^-1） > 工业区（809.58 ng·g^-1） > 公园（273.66 ng·g^-1） > 文教区（268.18 ng·g^-1） > 商业区（240.05 ng·g^-1） > 农业区（226.81 ng·g^-1） > 医疗区（211.90 ng·g^-1） > 居民区（183.49 ng·g^-1）;内梅罗综合指数显示82.58%的样点不存在污染,轻微、轻度和中度污染占比分别为6.45%、4.52%和0.65%,5.8%的样点存在重度污染;健康风险评价结果表明,皮肤接触和误食是最主要的土壤PAHs暴露途径,其健康风险处于可接受水平;源解析表明石嘴山市土壤PAHs的主要来源为交通排放源、煤炭燃烧源、生物质/重油燃烧的混合源以及石油源,其贡献率分别为10.5%、36.6%、50.3%和2.6%,且高值大多分布在工业或煤炭生产区域.研究结果可为工业城市土壤污染研究提供参考,并对预防土壤污染、保障土壤环境质量及人体健康安全有积极作用.     

Impact of solids on biphasic biodegradation of phenanthrene in the presence of hydroxypropyl-β-cyclodextrin (HPCD)

The consequence of polycyclic aromatic hydrocarbons (PAHs) in the environment is of great concern. The hydrophobic properties of PAHs significantly impact phase distribution causing limited bioavailability. Enhanced biodegradation has been extensively carried out by surfactants and the redeployment effect was recognized. However, the quantitative relationship concerning the impact of solids was rarely reported. A batch of biphasic tests were carried out by introducing Mycobacterium vanbaalenii PYR-1 and hydroxypropyl-β-cyclodextrin (HPCD) into a mixture of phenanthrene solution and various glass beads (GB37-63, GB105-125, and GB350-500). The comparative results demonstrated that HPCD had little effect on microbial growth and was not degradable by bacterium. A model was proposed to describe the biodegradation process. The regression results indicated that the partition coefficient k _d (1.234, 0.726 and 0.448 L·g⁻¹) and the degradation rate k (0 mmol·L⁻¹: 0.055, 0.094, and 0.112; 20 mmol·L⁻¹: 0.126, 0.141, and 0.156; 40 mmol·L⁻¹: 0.141, 0.156 and 0.184 d⁻¹) were positively and negatively correlated with the calculated total surface area (TSA) of solids, respectively. Degradation enhanced in the presence of HPCD, and the enhancing factor f was calculated (20 mmol·L⁻¹: 15.16, 40.01, and 145.5; 40 mmol·L⁻¹: 13.29, 37.97, and 138.4), indicating that the impact of solids was significant for the enhancement of biodegradation.     

废旧汽车拆解区土壤中多环芳烃垂向分布特性

研究分析了废旧汽车拆解区土壤剖面的美国EPA优控的16种多环芳烃的纵向分布.结果表明,表层土壤中16种多环芳烃总含量达到了17 323 ng·g-1,其中芘(Pyr)、苯并[a]蒽(BaA)、芴(Flu)含量最高,分别达到11 820、1 234和1 083 ng·g-1.汽车拆解区表面和土壤深度为10 cm的土壤均达到了重度污染级别;深度在50~350 cm之间的土壤为轻度至中度污染,当土壤深度超过400 cm,土壤基本未受到污染.但是,7种致癌性PAHs(Chr、BaA、BbF、BkF、BaP、DahA、IcdP)总量在土壤深度达到850 cm时仍有34.15 ng·g-1.随着土壤深度的增大,多环芳烃含量急剧降低,当土壤深度超过300 cm,三环的菲(Phe)、荧蒽(Fl)和二氢苊(Ace)成为优势组分.土壤剖面菲(Phe)/蒽(Ant)比值和荧蒽(Fla)/芘(Pyr)、Fluo/Pyr、BaA/(BaA+Chr)等参数表明,土壤表面的多环芳烃主要来源于石油污染.     

表面活性剂Burkholderia xenovorans LB400体系对低氯代PCBs的好氧强化降解

增强多氯联苯(PCBs)的水溶性是强化PCBs微生物降解的主要控制因素之一,本研究选取了PCB5(2,3-CB)和PCB31(2,4’,5-CB)作为低氯代PCBs的典型代表,以曲拉通100(TX-100)、吐温80(Tween 80)、鼠李糖脂粗提物(RL crude)3种表面活性剂和β-环糊精(HPCD)联合Burkholderia xenovorans LB400构建PCBs好氧降解体系,测试了它们对PCB5和PCB31的溶出率及微生物生长的影响.结果表明,TX-100(CMC=194 mg·L-1)、Tween 80(CMC=13.1 mg·L-1)、RL crude(CMC=50mg·L-1)浓度在1~7 CMC时和HPCD浓度在500~1500 mg·L-1时对PCB5和PCB31溶出率分别达到54.7%~100%、59.8%~100%;10.5%~40.8%、6.8%~31.6%;10.3%~19.9%、3.3%~11.6%和19.5%~34.2%、4.2%~10.7%.TX-100浓度在1~7 CMC时对B.xenovorans LB400生长的抑制率达到30.3%~45.8%,而Tween 80浓度在0.1~1 CMC时对其生长的抑制率为10.0%~15.4%;RL crude本身能作为底物促进LB400的生长,而HPCD对其生长无明显影响.B.xenovorans LB400对PCB31(5 mg·L-1)的降解效率在添加表面活性剂后有不同程度的提高:TX-100,23.7%~65.5%;Tween80,14.6%~44.3%;RL crude,9.6%~27.2%;HPCD,15.3%~20.7%;而表面活性剂对PCB5(10 mg·L-1)的降解效率则无明显影响.表面活性剂主要通过增大溶液中PCBs-表面活性剂的胶束浓度来提高LB400对PCBs的降解效率,在水溶液培养体系中当设置TX-100和Tween 80浓度分别在1和7 CMC时,PCB31的降解效率达到100%和81.7%,而此时B.xenovorans LB400生长的抑制率为30.3%和5.4%.     

降雨期间岩溶地下河溶解态多环芳烃变化特征及来源解析

2014年6月降雨期间在重庆南山老龙洞地下河出口处进行连续采样监测,利用GC-MS定量分析地下河溶解态中16种优控多环芳烃(PAHs)的含量,研究了降雨期间地下河溶解态PAHs变化特征及来源.结果表明,地下河溶解态PAHs对降雨反应迅速,ΣPAHs出现4个峰值,有2个出现在流量上升阶段,另外两个分别出现在流量最大值处和流量下降阶段.ΣPAHs范围为101~3 624 ng·L-1,平均值578 ng·L-1,7种致癌性PAHs变化较大,含量变化为ND~336 ng·L-1,平均值31.1 ng·L-1,PAHs的组成以低环(2、3环)为主,占水体ΣPAHs的86.17%;降雨对ΣPAHs影响较大,主要表现为雨水对大气污染物的清除及地表径流对地表污染物的冲刷.降雨期间水体中PAHs主要来源于石油类产品、煤炭等化石燃料的不完全燃烧、天然成岩过程,降雨期间老龙洞地下河水体中PAHs污染大部分为中等到重污染水平.     

富里酸在水体多环芳烃光化学降解中的作用

以氙灯作为模拟光源,对水相中5种不同来源、不同浓度富里酸(FA)在5种PAHs光解中的作用进行了比较分析;并通过活性氧的捕获探讨了FA在PAHs光解中的作用.结果表明,不同来源FA的结构及其对PAHs光解的影响具有较高的一致性.在低浓度(1.25 mg·L-1)体系中FA对二氢苊、芴、菲的光解表现出不同程度的抑制作用,而对荧蒽和芘的光解则表现出一定的促进作用;随着体系中FA浓度的升高,其对PAHs的光解总体上呈抑制趋势.FA的存在一方面促进了单线态氧和羟基自由基的生成,强化了PAHs的活性氧光解进程;另一方面FA也可以参与PAHs分子的能量竞争.     

岩溶地下河流域水中多环芳烃污染特征及生态风险评价

利用气相色谱-质谱联用仪(GC/MS)测定了老龙洞地下河流域水中16种优控多环芳烃(polycyclic aromatic hydrocarbons,PAHs)含量,研究了流域内PAHs组成、污染水平,并对其进行了生态风险评价.结果表明,老龙洞地下河水中ΣPAHs含量变化范围为81.5~8 019 ng·L-1,表层岩溶泉ΣPAHs含量为288.7~15200 ng·L-1,地表水ΣPAHs含量为128.4~2 442 ng·L-1;受黄桷垭镇污水的影响,地下河水相对于地下水补给来源的落水洞和地表水含量较高.流域内水中PAHs均以低环为主,尤其是3环占主导.受污水、季节的影响及PAHs物理化学性质的差异,水中PAHs月变化呈现不同的变化特征.地表水、落水洞污水排放对地下河PAHs来源起重要作用.流域内水中PAHs以低环污染为特征,所有检测到的PAH化合物处于中等污染和重污染风险.