净化液处理对豇豆采后多环芳烃(PAHs)的净化效果研究

为降低蔬菜采后体内多环芳烃(PAHs)对人体的危害风险,以豇豆为材料,利用不同浓度洗洁精、食盐、米酒、米醋、植物油及清水分别对豇豆豆荚进行浸洗,通过高效液相色谱-质谱联用法检测豇豆采后体内PAHs的含量,并筛选出豇豆体内PAHs的最佳净化方法。结果表明,米酒和米醋处理对豇豆体内PAHs的去除效果基本一致,其中米酒处理组的∑PAHs（美国环保局公布的优先监测的16种多环芳烃的含量总和）降低68.92%,米醋处理组的∑PAHs降低73.88%,且对萘、二苯并(a,h)蒽和茚并(1,2,3-c,d)芘等均有明显的去除效果;清水浸洗可有效降低豇豆体内的茚并(1,2,3-c,d)芘含量,但会使菲的含量增加;食盐处理使∑PAHs增加了77.15%,主要表现在增加了2、3环PAHs在豇豆体内的积累;植物油处理可降低个别PAHs单体含量,但会引入其他PAHs单体,同时增加∑PAHs含量。毒性当量计算结果表明,米酒能有效降低豇豆体内的PAHs毒性,同时食盐处理也使豇豆体内的PAHs毒性当量降低。米酒和米醋能有效降低豇豆体内∑PAHs和二苯并(a,h)蒽的含量及其毒性当量。     

樟树林地土壤多环芳烃的含量及其分布特征

研究樟树林地和无林地土壤中PAHs的含量和分布特征,并对两种土地类型土壤中的PAHs含量水平进行评价.结果表明:两种土地类型土壤中PAHs主要积累在0～30 cm的表土层,并随土层加深而明显减少,各土层中以高环的PAHs组分为主,PAHs主要源于燃烧源;樟树林地土壤中PAHs含量明显低于无林地,无林地表土层中PAHs含量是樟树林地表土层的1.1倍;对两种土壤中的PAHs含量水平进行评价,得知樟树林地土壤PAHs超标5种,无林地土壤不仅超标8种,且超标倍数明显大于樟树林地,樟树林地土壤的PAHs污染程度小于无林地.     

樟树林生态系统中多环芳烃含量和分布特征

利用气相色谱仪 (GC)对樟树林生态系统中植物体各器官和林地土壤的多环芳烃 (PAHs)进行定性和定量测定。结果表明 :乔木层樟树各器官中树皮的PAHs含量最高 ,为 86 4 1μg·kg- 1 ;树干最低 ,为 2 84 3μg·kg- 1 ;其他依次为籽实 (75 2 0 μg·kg- 1 ) >树根 (7115 μg·kg- 1 ) >树枝 (5 35 2 μg·kg- 1 ) >树叶 (4 4 81μg·kg- 1 )。樟树林生态系统中PAHs含量空间分布为 :枯枝落叶层 (92 35 μg·kg- 1 ) >乔木层 (5 995 μg·kg- 1 ) >草本层 (36 31μg·kg- 1 ) >土壤层(14 6 6 μg·kg- 1 ) >灌木层 (2 4 5 μg·kg- 1 )。与无林地土壤的PAHs含量 (3470 μg·kg- 1 )相比 ,樟树林土壤的PAHs含量低 5 0 %以上。同时 ,随大气降水进入樟树林的PAHs,经过林木的吸附和降解后 ,林内降水和地表径流的PAHs种类和含量明显减少 ,说明樟树林生态系统对PAHs具有吸附和降解作用。     

黄河兰州段多环芳烃生态风险的初步评价

以黄河兰州段11个不同采样点3种多环芳烃的临测浓度及其对6～38种水生生物的LC50为基础资料,分别应用商值法、概率密度函数重叠面积和联合概率曲线3种风险浮价方法对黄河兰州段苯并(a)芘、荧蒽、芘的生态风险进行了评价.结果表明:黄河兰州段3种PAHs残留具有一定的生态风险.其中低暴露风险条件下(受威胁生物不超过1%),...     

土壤中多环芳烃的微生物降解: 降解途径及其影响影子

Adverse effects on the environment and high persistence in the microbial degradation and environmental fate of polycyclic aromatic hydrocarbons (PAHs) are motivating interest. Many soil microorganisms can degrade PAHs and use various metabolic pathways to do so. However, both the physio-chemical characteristics of compounds as well as the physical, chemical, and biological properties of soils can drastically influence the degradation capacity of naturally occurring microorganisms for field bioremediation. Modern biological techniques have been widely used to promote the efficiency of microbial PAH-degradation and make the biodegradation metabolic pathways more clear. In this review microbial degradation of PAHs in soil is discussed, with emphasis placed on the main degradation pathways and the environmental factors affecting biodegradation.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Variability of communities and physiological characteristics between free-living bacteria and attached bacteria during the PAH biodegradation in a soil/water system

The biodegradation of polycyclic aromatic hydrocarbons (PAHs) via free-living and attached micro-organisms in soil/water systems was observed in order to examine the variability in the community dynamics and physiological profiles of the micro-organisms. As determined by fluorescence in situ hybridization (FISH), the Domain Bacteria, consisting of three phyla α-, β- and γ-Proteobacteria, reached 41.27–56.05% of all organisms in the soil/water system for PAH biodegradation. Among the free-living species, Proteobacteria, including Brevundimonas (Pseudomonas) diminuta, Caulobacter spp., Mycoplana bullata, Acidovorax spp. and Pseudomonas aeruginosa were found to be dominant—making up 93.51–99.80% of the population—and therefore seem to be associated with PAH biodegradation. Total plate count numbers and the count of Pseudomonas sp. present in the free-living population increased to between 10³ and 10⁶ CFU ml⁻¹ when clay with very low organic matter content was used as the matrix for PAH degradation. However, total plate count microbial numbers increased to only 10¹–10² CFU ml⁻¹ using natural soil from Taichung containing 1.883% organic matter. The soil organic content (SOM) seemed to affect the mass transfer of PAH in soil, leading to the difference in PAH biodegradation. Two different approaches, which included community-level physiological profiling (CLPP) and ectoenzymatic activities, were used to explain the functional diversity between free-living and attached bacteria. The free-living and attached bacterial communities from the clay system showed proportionately greater differences using CLPP. Relatively high levels of esterases, aminopeptidases and some specific glycolysis-gluconeogenesis enzymes gave an identifiable correlation with PAH biodegradation. The differences in bacterial composition, numbers and physiological characteristics show that free-living and attached micro-organisms may play different biochemical roles in PAH degradation in soil.     

深圳市不同城市密度区中环芳烃的发生、来源及生态风险评估

Urbanization may cause increased exposure levels to polycyclic aromatic hydrocarbons(PAHs) and associated health risks for over half of the world's population living in cities,but little evidence has shown a direct spatial relationship between urbanization and soil PAH pollution.Based on the monitored PAH concentrations in 188 topsoil(0-5 cm) samples in Shenzhen,the most rapidly developing city in China,in recent decades,we applied geographical demarcation to determine the occurrences,source apportionments,and spatial ecological risks of soil PAHs across five zones of varying urban densities.Mean concentrations of the 16 US Environmental Protection Agency(EPA) priority PAHs(Σ_(16)PAHs) and the 7 carcinogenic PAHs(Σ_7CarPAHs) both followed the order:Zone D(60%-80%constructive land density(CLD)) Zone E(80%-100%CLD) Zone C(40%-60%CLD) Zone B(20%-40%CLD) Zone A(0%-20%CLD),suggesting that the highest PAH levels occurred in the suburban-urban center transitional zone(Zone D) rather than the urban center zone(Zone E) in Shenzhen.There were significant correlations of Σ_(16)PAHs to TOC and sampling altitude across all samples but not within highly-urbanized regions(Zones D and E),implying a considerable disturbance of urbanization to the soil PAH pool.Source apportionments suggested that soil PAHs of all zones were mainly derived from fossil fuel combustion,with Zone E showing the highest contribution from oil sources among different zones.Spatial ecological risk analysis showed that the contaminated area(467 km~2;23.9%of total area;toxic equivalency quotients 33 ng g~(-1)) had a higher contribution from the highly-urbanized regions(Zones D and E) than the uncontaminated area(42.3%vs.18.1%).Overall,our study highlighted a strong spatial relationship between urbanization and soil PAH pollution.     

噬氨副球菌HPD-2固体发酵条件优化及其对PAHs污染土壤的修复效果

选用有机肥A、有机肥B和紫花苜蓿粉3种有机物料作为菌剂载体,探讨了固体发酵过程中物料量、接种量、固水比和发酵时间对噬氨副球菌HPD-2生长的影响,以及固体发酵菌剂对PAHs污染土壤的修复效果。结果表明,3种发酵载体中,以有机肥A的效果最好。噬氨副球菌HPD-2以有机肥A为载体的固体发酵最佳条件为物料量20 g、接种量5%、固水比1:1、发酵时间 144 h。菌剂施入土壤28天后,土壤中PAHs总含量由初始的9.96 mg/kg 下降到7.64 mg/kg,其去除率达22.8%。不同环数PAHs的去除率高低顺序为3环＞5环＞6环和4环,分别下降了35.1%、27.0%、20.7%、20.4%。该菌剂对PAHs污染土壤有一定的修复效果。     

香港土壤研究 Ⅲ.土壤中多环芳烃的含量及其来源初探

通过对香港地区53个土壤样品多环芳烃(PAHs)含量的分析,并利用GIS空间数据管理功能,揭示了香港土壤中PAHs的含量和空间分布特征,同时,运用比值法定性地判断了土壤中PAHs的来源。研究结果表明:香港土壤中可以检测出16种美国环保署规定的优控PAHs中的15种(二苯并(a,h)蒽未被检测到),郊野土壤中PAHs的平均含量为34.2±16.0μg kg-1,而城区土壤中PAHs的平均含量为169±123μg kg-1,港岛动植物公园土壤中的苯并(a)芘的含量最高达到了47.2μg kg-1。在PAHs的来源上,前者的PAHs可能主要来自山火焚烧,而后者可能主要与城区的汽车尾气排放有密切的联系。