Assessing the potential for rhizoremediation of PCB contaminated soils in northern regions using native tree species

Rhizosphere bioremediation of polychlorinated biphenyls (PCBs) offers a potentially inexpensive approach to remediating contaminated soils that is particularly attractive in remote regions including the Arctic. We assessed the abilities of two tree species native to Alaska, Salix alaxensis (felt-leaf willow) and Picea glauca (white spruce), to promote microbial biodegradation of PCBs via the release of phytochemicals upon fine root death. Crushed fine roots, biphenyl (PCB analogue) or salicylate (willow secondary compound) were added to microcosms containing soil spiked with PCBs and resultant PCB disappearance, soil toxicity and microbial community changes were examined. After 180 d, soil treated with willow root crushates showed a significantly greater PCB loss than untreated soils for some PCB congeners, including the toxic congeners, PCB 77, 105 and 169, and showed a similar PCB loss pattern (in both extent of degradation and congeners degraded) to biphenyl-treated microcosms. Neither P. glauca (white spruce) roots nor salicylate enhanced PCB loss, indicating that biostimulation is plant species specific and was not mediated by salicylate. Soil toxicity assessed using the Microtox bioassay indicated that the willow treatment resulted in a less toxic soil environment. Molecular microbial community analyses indicated that biphenyl and salicylate promoted shifts in microbial community structure and composition that differed distinctly from each other and from the crushed root treatments. The biphenyl utilizing bacterium, Cupriavidus spp. was isolated from the soil. The findings suggest that S. alaxensis may be an effective plant for rhizoremediation by altering microbial community structure, enhancing the loss of some PCB congeners and reducing the toxicity of the soil environment.     

Estimating the Microbial Risk of E. coli in Reclaimed Wastewater Irrigation on Paddy Field

Microbial risk was quantified to assess human health risk as a result of exposure to E. coli in reclaimed wastewater irrigation. Monitoring data on E. coli were collected from pond water in paddy rice plots during the growing season. Five treatments were used and each was triplicated to evaluate the changes in E. coli concentrations in experiments performed in 2003 and 2004. The Beta-Poisson model was used to estimate the microbial risk of pathogen ingestion among farmers and neighboring children. A Monte Carlo simulation (10,000 trials) was conducted to estimate the risk associated with uncertainty. In this study, risk values ranged from 10⁻⁴ to 10⁻⁸. UV-disinfected irrigation water showed a lower risk value than others, and its level was within the range of the actual paddy rice field with surface water. Agricultural activity was thought to be safer after 1–2 days, when the paddy field was irrigated with reclaimed wastewater. Also, children were found to have a greater risk of infection with E. coli. This paper should be viewed as a first step in the application of quantitative microbial risk assessment of wastewater reuse in paddy rice culture.     

Multiple effects of nitrate amendment on the transport, transformation and bioavailability of antimony in a paddy soil-rice plant system

Nitrate (NO₃^?) is known to be actively involved in the processes of mineralization and heavy metal transformation; however, it is unclear whether and how it affects the bioavailability of antimony (Sb) in paddy soils and subsequent Sb accumulation in rice. Here, the effects of NO₃^? on Sb transformation in soil-rice system were investigated with pot experiments over the entire growth period. Results demonstrated that NO₃^? reduced Sb accumulation in brown rice by 15.6% compared to that in the control. After amendment with NO₃^?, the Sb content in rice plants increased initially and then gradually decreased (in roots by 46.1%). During the first 15 days, the soil pH increased, the oxidation of Sb(III) and sulfides was promoted, but the reduction of iron oxide minerals was inhibited, resulting in the release of adsorbed and organic-bound Sb from soil. The microbial arsenite-oxidizing marker gene aoxB played an important role in Sb(III) oxidation. From days 15 to 45, after NO₃^? was partially consumed, the soil pH decreased, and the reductive dissolution of Fe(III)-bearing minerals was enhanced; consequently, iron oxide-bound Sb was transformed into adsorbed and dissolved Sb species. After day 45, NO₃^? was completely reduced, Sb(V) was evidently reduced to Sb(III), and green rust was generated gradually. Thus, the available Sb decreased due to its enhanced affinity for iron oxides. Moreover, NO₃^? inhibited the reductive dissolution of iron minerals, which ultimately caused low Sb availability. Therefore, NO₃^? can chemically and biologically reduce the Sb availability in paddy soils and alleviate Sb accumulation in rice. This study provides a potential strategy for decreasing Sb accumulation in rice in the Sb-contaminated sites.     

Comparison of the food waste degradation rate and microbial community in the matrix between two biodegradation agents in a food waste disposer

To reduce the proportion of food waste in municipal solid waste, a food waste biodegradation experiment with two biodegradation agents was conducted for seven weeks with 500 g of food waste added every day into each disposer. The agent containing four biodegradation bacterial strains showed higher degradation rates and matrix temperatures than that containing two. Furthermore, significant differences in the microbiological community structures of the matrixes were found not only between the two biodegradation systems but also among different stages in the same degradation system based on DGGE profiles. The F2 strain exhibited the highest DGGE optical density (OD) value among biodegradation systems and at all experimental stages, suggesting it was a dominant strain during food waste degradation.     

Integrated Waste Management in a Zone of Northern Italy: Compost Production and Use,and Analytical Control of Compost,Soil, and Crop

Agricultural soils of two Italian maize farms were treated for five years with an industrially produced high-quality compost. Cattle manure and the usual mineral fertilizer were used for comparison purposes. The effects of the organic and mineral fertilizer treatments were studied by analyzing the compost and manure, cultured soils, and harvested material. The grain yield was also determined. Organic fertilization improved soil pH, CEC, content of organic matter and NPK. Soil respiration and N mineralization were found to be higher than in the purely mineral-treated soil. Plant K take-up was improved, whereas grain yield was not affected. It was confirmed that organic fertilization, particularly compost use, maintained and increased soil fertility. The study demonstrated the feasibility of using in loco analytical facilities to follow the entire recycling process—from waste to compost production—and the use of the final product in the field.     

Comparing the removal of polycyclic aromatic hydrocarbons in soil after different bioremediation approaches in relationto the extracellular enzyme activities

A 120-day experiment was conducted to compare the removal of polycyclic aromatic hydrocarbons(PAHs) from agricultural soil after natural attenuation(NA), phytoremediation(P), mycoremediation(M), and plant-assisted mycoremediation(PAM) approaches in relation to the extracellular enzyme activities in soil. The NA treatment removed the total soil PAH content negligibly. The P treatment using maize(Zea mays) enhanced only the removal of low and medium molecular PAHs. The Pleurotus ostreatus cultivated on 30–50 mm wood chip substrate used in M treatment was the most successful in the removal of majority PAHs. Therefore,significantly(p 0.05) highest total PAH removal by 541.4 μg/kg dw(dry weight)(36%) from all tested M treatments was observed. When using the same fungal substrate together with maize in PAM treatment, the total PAH removal was not statistically different from the previous M treatment. However, the maize-assisted mycoremediation treatment significantly boosted fungal biomass, microbial and manganese peroxidase activity in soil which strongly correlated with the removal of total PAHs. The higher PAH removal in that PAM treatment could be reflected in the following post-harvest time. Our suggested M and PAM approaches could be promising in situ bioremediation strategies for PAH-contaminated soils.     

Rapid aerobic granulation in an SBR treating piggery wastewater by seeding sludge from a municipal WWTP

Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor (SBR) using piggery wastewater. Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2 mm and SVI₃₀ of 20.3 mL/g formed in SBR on day 18. High concentrations of Ca and Fe in the raw piggery wastewater and operating mode accelerated aerobic granulation, even though the seed sludge was from a municipal wastewater treatment plant (WWTP). Alpha diversity analysis revealed Operational Taxonomic Units, Shannon, ACE and Chao 1 indexes in aerobic granules were 2013, 5.51, 4665.5 and 3734.5, which were obviously lower compared to seed sludge. The percentages of major microbial communities, such as Proteobacteria, Bacteroidetes and Firmicutes were obviously higher in aerobic granules than seed sludge. Chloroflexi, Planctomycetes, Actinobacteria, TM7 and Acidobacteria showed much higher abundances in the inoculum. The main reasons might be the characteristics of raw piggery wastewater and granule structure.     

微生物絮凝剂TH6的絮凝特性研究

从活性污泥中分离出一株絮凝活性较高的絮凝剂产生菌TH6，采用由其产生的絮凝剂对高岭土悬浊液和多种实际废水进行了絮凝净化实验，结果表明，TH6絮凝剂固液分离效果良好，CODCr去除率51．0％－71．5％，SS去除率88．5％－94．3％。     

微生物群落多样性分析方法的进展

微生物群落多样性由3个组成要素形成；物种多样性，遗传多样性，功能多样性，从这3方面系统地概述了细胞结构分析方法。分析生物学方法，功能多样性方法等技术在国内外的研究进展，并综合分析及探讨了这些技术的优点和不足。微生物群落多样性分析，对环境资源调查，环境变化监控，环境治理及环境压力等研究。具有深远的意义。具有深远的意义。而其分析方法的发展趋势，则是原位快速，高通量的检测。     

Pronounced temporal changes in soil microbial community and nitrogen transformation caused by benzalkonium chloride

As one typical cationic disinfectant, quaternary ammonium compounds (QACs) were approved for surface disinfection in the coronavirus disease 2019 pandemic and then unintentionally or intentionally released into the surrounding environment. Concerningly, it is still unclear how the soil microbial community succession happens and the nitrogen (N) cycling processes alter when exposed to QACs. In this study, one common QAC (benzalkonium chloride (BAC) was selected as the target contaminant, and its effects on the temporal changes in soil microbial community structure and nitrogen transformation processes were determined by qPCR and 16S rRNA sequencing-based methods. The results showed that the aerobic microbial degradation of BAC in the two different soils followed first-order kinetics with a half-life (4.92 vs. 17.33 days) highly dependent on the properties of the soil. BAC activated the abundance of N fixation gene (nifH) and nitrification genes (AOA and AOB) in the soil and inhibited that of denitrification gene (narG). BAC exposure resulted in the decrease of the alpha diversity of soil microbial community and the enrichment of Crenarchaeota and Proteobacteria. This study demonstrates that BAC degradation is accompanied by changes in soil microbial community structure and N transformation capacity.