Habitat function of agricultural soils as affected by heavy metals and polycyclic aromatic hydrocarbons contamination

Ecotoxic activity of soils polluted with polycyclic aromatic hydrocarbon (PAH) and heavy metals (HM) was evaluated in pot and laboratory experiments. Plants and soil microorganisms were chosen as test organisms and six different soil materials were used in the study. The applied levels of HM and PAH were aimed to reflect environmental conditions in the "worst case" situation. Zn(2+), Pb(2+) and Cd(2+) were introduced to the soils as an aqueous solution of the mixture of salts at the concentrations corresponding to 1000, 500 and 3 mg kg(-1), respectively. Mixture of four PAH compounds (flourene, anthracene, pyrene and chrysene) as a CH(2)Cl(2) solution was applied at levels of 10-100 mg summation operator 4PAH kg(-1). Population and activity of soil microflora was evaluated as measured of total bacteria counts, intensity of respiration and enzyme activity (dehydrogenases and phosphatases). Effect on plants was evaluated on the base of the growth (plant at an early stage of their development) and yield (mature plant) measurements. The results indicate that combined effect of PAH and heavy metals on soil microorganisms activity and on some plants at an early stage of their development can be stronger than in soils amended with HM or PAH separately. Reaction of tested organisms was related to soil properties, PAH concentration, time and plant species. Mature plants (maize) were insensitive to the applied levels of both group of contaminants.     

Occurrence of coal and coal-derived particle-bound polycyclic aromatic hydrocarbons (PAHs) in a river floodplain soil

A PAH contaminated river floodplain soil was separated according to grain size and density. Coal and coal-derived particles from coal mining, coal industry and coal transportation activities were identified by organic petrographic analysis in our samples. Distinct concentrations of PAHs were found in different grain size and density fractions, however, similar distribution patterns of PAHs indicated similar sources. In addition, although light fractions had the mass fraction by weight of less than 5%, they contributed almost 75% of the total PAHs in the soil. PAH concentrations of all sub fractions showed positive correlation with their TOC contents. Altogether, coal and coal-derived particles that were abundant in light fractions could be the dominant geosorbents for PAHs in our samples.     

A Pilot Study on Using Urinary 1-Hydroxypyrene Biomarker for Exposure to PAHs in Beijing

To study whether the urinary 1-hydroxypyrene (1-OHP) could be the biomarker of atmospheric PAHs, a small-scale pilot study was carried out on the relation of 1-OHP vs PAHs with the traffic policemen in Beijing of smokers and nonsmokers to be subgroups in both the exposure and control groups. Both the PAHs and 1-OHP were analyzed with high performance liquid chromatography (HPLC). The ambient concentrations of PAHs were different at the different sites (the average sum of PAHs (TPAH) were 12.36, 16.27, 18.37 ng/m³ at the suburban residential, police station and high traffic area, respectively.), but considerably lower than the personal-exposure concentrations (the average TPAH were 65.84 and 47.28 ng/m³ for patrol cars and inspection station, respectively). Pyrene was correlated well with BaP and the summed PAHs (TPAH), with the correlation coefficients (R) of 0.79, 0.87 for ambient level and 0.92, 0.96 for personal exposure, respectively. The average of 1-hydroxypyrene of smokers and nonsmokers were 0.39, 0.15 μmol/mol creatinine in control group and 0.57, 0.33 μmol/mol creatinine in exposure group, respectively. The better correlation of pyrene to BaP and TPAH especially for personal exposure samples indicated that the probability of urinary 1-hydroxypyrene, the metabolite of pyrene, to be the biomarker of total PAH. Nonsmokers in the exposure and control groups had indistinguishable levels of 1-OHP, presumably because the ambient levels of pyrene were so similar (the average were 3.25, 3.20 ng/m³ at the police station and high traffic area, respectively.). Smokers in the control group had significantly higher 1-OHP than that of the nonsmokers, but showed indistinguishable differences in the exposure group. These results suggested that urinary 1-OHP could be a biomarker of PAHs only when the level of PAHs was at a relatively higher level. Smoking as an important influencing factor need to be controlled carefully.     

Root Exudates Impact on Phenanthrene Availability

In order to improve and optimize phytoremediation of PAH we propose to focus on the rhizospheric processes controlling PAH degradation. In this paper the effect of root exudates on PAH availability is studied. Model organic compounds (malic acid, malonic acid and EDTA) representing root exudates have been tested for their effect on phenanthrene sorption on a reference non polluted agricultural soil material. Phenanthrene adsorption isotherms were first obtained with batch experiments. Results showed linear isotherms and phenanthrene sorption was enhanced as the concentration of organic compounds in the solution increased. Column leaching experiments were then used to simulate the effect of root exudation following the soil pollution. Inlet solutions containing the different organic acids used were flowed through the column containing the artificially polluted soil material. Elution curves showed that the phenanthrene was less easily eluted when the solution injected contained the organic acids. However, magnitude of the phenomena did not fit with adsorption constants obtained in batch experiments. Phenanthrene desorption appeared limited by sequestration but organic acids seemed able to partially disturb the soil material structure to limit the sequestration effect.     

Dual <Superscript>14</Superscript>C/residue analysis method to assess the microbial accessibility of native phenanthrene in environmental samples

The aim of this work was to develop a method to assess the microbial accessibility of native phenanthrene present in soils and sediments. We developed an accelerated biodegradation assay, characterized by (a) inoculation with a sufficient number of phenanthrene-degrading microorganisms, (b) monitoring of the biodegradation activity through ¹⁴C-mineralization measurements, and (c) single-step chemical analysis of the native compound in the residue. The use of ¹⁴C-labeling allowed the determination of the time period needed for biodegradation of the bioaccessible fraction of the native chemical. The method was tested with environmental samples having a wide range of phenanthrene concentrations, i.e., from background levels (μg kg^-1) originating in soil from atmospheric deposition, to acute concentrations (g kg^-1) corresponding to industrial pollution of soils and sediments. The results showed a wide range of bioaccessibility (15–95% of the initial amount). The method can be used for the assessment of bioaccessibility involved in the management of polycyclic aromatic hydrocarbon (PAH) pollution.     

Combined effects of cadmium and fluoranthene on germination, growth and photosynthesis of soybean seedlings

The single and combinational effects of cadmium (Cd) and fluoranthene (FLT) on germination, growth and photosynthesis of soybean seedlings were investigated. Exposure to 5, 10, or 15 mg Cd/L or 1, 5, or 10 mg FLT/L individually or in combination significantly decreased germination vigor (3 days) and final germination rate of soybean seeds, except at 1 and 5 mg FLT/L. The results of two-way ANOVA analysis and the Bliss independence model showed that at lower concentrations of FLT (1 mg/L), the interaction between Cd and FLT on germination was antagonistic, whereas the interaction was synergistic when the concentration of FLT was 5 or 10 mg/L and the concentration of Cd was 15 mg/L. Growth, expressed as dry weight, length of shoot and root, leaf area, and photosynthesis, expressed as net photosynthetic rate, intercellular CO2 concentration, chlorophyll contents and fluorescence of soybean seedlings were also reduced by exposure to 5 or 10 mg Cd/L or 1 or 5 mg FLT/L, singly or jointly. Significant antagonistic effects of exposure to 5 or 10 mg Cd/L or 1 or 5 mg FLT/L on shoot growth and photosynthesis were observed, whereas synergy and antagonism of Cd and FLT were both observed for root growth.     

生物堆修复城市多环芳烃污染土壤的调控研究

土壤多环芳烃(PAHs)污染已成为一种严重的全球性城市环境问题。以通风时间、绿肥、无机营养剂和疏松剂含量为调控因素,利用现场规模的正交试验进行了生物堆修复城市多环芳烃污染土壤的调控研究。结果表明,所有生物堆处理对土壤PAHs的去除均有一定促进作用,75 d时平均降解率为30.63%~80.41%,且深层土壤降解率比表层土壤高8.55%;运行期间各调控因素对不同深度土壤PAHs降解的影响程度和作用规律各不相同,其中通风时间始终是主导因素,且通风时间越长,降解效果越好;生物堆的最佳运行条件总体上为通风时间3 h、绿肥3.5%、营养剂0.2%、疏松剂18%(表层土壤)或14%(深层土壤)。因此,利用生物堆修复城市PAHs污染土壤是有效的,且增加通风时间是提高其修复效率的优先调控方式。     

Variation in PAH inputs and microbial community in surface sediments of Hamilton Harbour: implications to remediation and monitoring

Variations in concentrations of polycyclic aromatic hydrocarbons (PAHs) and microbial community indicators were investigated in representative highly contaminated and less contaminated surface sediment sites of Hamilton Harbour. Inputs of PAH to the upper 3cm of sediments up to four times the average upper sediment concentrations were observed. Associated PAH fingerprint profiles indicated that the source was consistent with the PAH source to the industrial region of the harbour. Increased PAH loadings were associated with decreased bacterial populations as indicated by phospholipid fatty acid (PLFA) concentrations. However, relatively minor impacts on overall community composition were indicated. Porewater methane concentrations and isotopic data indicated a difference in the occurrence of methane oxidation between the two sites. This study confirms temporally limited transport of contaminants from highly impacted regions as a vector for contaminants within the harbour and the impact on microbial carbon cycling and bed stability.     

Distribution of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, dioxin-like polychlorinated biphenyl and polycyclic aromatic hydrocarbons in the sediment of Temsah lake, Suez Canal, Egypt

Lake Temsah is one of the main wetlands in the Suez Canal region, and the main source for fish for the area. The lake is the end-point of several wastewater effluents. In the present study, residues of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyl (PCB) and polycyclic aromatic hydrocarbons (PAH) were monitored in the sediment of the lake. Samples were collected from six different sampling stations around the lake using a box-corer sampler, then kept frozen. Samples were extracted and cleaned up before residue determination was conducted using an HRGC/HRMS. An HP 6890 plus gas chromatograph was coupled to a Micromass Autospec Ultima mass spectrometer operating in EI mode at 35 eV and with a resolution of 10.000 (5% valley). PCDDs and PCDFs were detected in all sediment samples collected from various sampling stations. Results showed some progressive increase in PCDDs concentrations relevant to increase in chlorination. In the PCDD group of congeners, 1, 2, 3, 4, 6, 7, 8, 9 octa-CDD had the highest detected concentrations in all samples, while 2, 3, 7, 8 tetra-CDD showed the lowest concentrations. The World Health Organization toxicity equivalents ranged from 0.387 to 11.20 ng kg^-1 d.w. For PCDD homologues, hexa-CDD was the most dominant homologue in all sediment samples analysed. Regarding dioxin-like PCBs, results showed that IUPAC No. 118 congener, 2, 3, 4, 4, 5, pentachlorobiphenyl was the most concentrated of all detected congeners, with concentrations ranging between 0.039 and 43.201 µg kg^-1. For polycyclic aromatic hydrocarbons, benzo(b+k+j)fluoranthene had the highest concentrations in almost all sampling stations. However, fluorene was the smallest detected concentration in almost all stations. This result would indicate that PAH contamination of the lake seems to be coming from one main source in all sampling stations. The present work is the first record of PCCDs, PCCFs, and dioxin-like PCBs in the Temsah lake. The concentrations of the contaminants monitored in this study, especially those of PAHs, are rather alarming. Efforts should be made to stop point sources that contaminate the lake.     

某污灌区污水-土壤-地下水污染物分布特征

通过对某污灌区灌溉水、土壤及地下水的取样分析,研究了灌区污染物的分布特征。结果表明:灌区主要污染物为重金属Zn、多环芳烃和农残六六六。不同污染物分布特征不同。重金属主要富集于土壤表层,如Zn大部分富集于耕植层中(0～30cm),但浓度过高,其可向深部迁移。多环芳烃按分子量可分为三类,小分子量芳烃迁移过程中降解转化显著;中分子量芳烃迁移至深部土壤和地下水,土壤各深度吸附量几乎相同;大分子量芳烃化学性质稳定,易吸附沉积于表层土壤和底泥中。农残六六六迁移深度至少可达50m。