Influence of solar UV radiation on the nitrogen metabolism in needles of Scots pine (Pinus sylvestris L.)

Needles of 20-year-old Scots pine (Pinus sylvestris L.) saplings were studied in an ultraviolet (UV) exclusion field experiment (from 2000 to 2002) in northern Finland (67 °N). The chambers held filters that excluded both UV-B and UV-A, excluded UV-B only, transmitted all UV (control), or lacked filters (ambient). UV-B/UV-A exclusion decreased nitrate reductase (NR) activity of 1-year-old needles of Scots pines compared to the controls. The proportion of free amino acids varied in the range 1.08-1.94% of total proteins, and was significantly higher in needles of saplings grown under UV-B/UV-A exclusion compared to the controls or UV-B exclusion. NR activity correlated with air temperature, indicating a “chamber effect”. The study showed that both UV irradiance and increasing temperature are significant modulators of nitrogen (N) metabolism in Scots pine needles.     

Microbial community dynamics in uranium contaminated subsurface sediments under biostimulated conditions with high nitrate and nickel pressure

BACKGROUND, AIM, AND SCOPE: The subsurface at the Oak Ridge Field Research Center represents an extreme and diverse geochemical environment that places different stresses on the endogenous microbial communities, including low pH, elevated nitrate concentrations, and the occurrence of heavy metals and radionuclides, including hexavalent uranium [U(VI)]. The in situ immobilization of U(VI) in the aquifer can be achieved through microbial reduction to relatively insoluble U(IV). However, a high redox potential due to the presence of nitrate and the toxicity of heavy metals will impede this process. Our aim is to test biostimulation of the endogenous microbial communities to improve nitrate reduction and subsequent U(VI) reduction under conditions of elevated heavy metals. MATERIALS AND METHODS: Column experiments were used to test the possibility of using biostimulation via the addition of ethanol as a carbon source to improve nitrate reduction in the presence of elevated aqueous nickel. We subsequently analyzed the composition of the microbial communities that became established and their potential for U(VI) reduction and its in situ immobilization. RESULTS: Phylogenetic analysis revealed that the microbial population changed from heavy metal sensitive members of the actinobacteria, alpha- and gamma-proteobacteria to a community dominated by heavy metal resistant (nickel, cadmium, zinc, and cobalt resistant), nitrate reducing beta- and gamma-proteobacteria, and sulfate reducing Clostridiaceae. Coincidentally, synchrotron X-ray absorption spectroscopy analyses indicated that the resulting redox conditions favored U(VI) reduction transformation to insoluble U(IV) species associated with soil minerals and biomass. DISCUSSION: This study shows that the necessary genetic information to adapt to the implemented nickel stress resides in the endogenous microbial population present at the Oak Ridge FRC site, which changed from a community generally found under oligotrophic conditions to a community able to withstand the stress imposed by heavy metals, while efficiently reducing nitrate as electron donor. Once nitrate was reduced efficient reduction and in situ immobilization of uranium was observed. CONCLUSIONS: This study provides evidence that stimulating the metabolism of the endogenous bacterial population at the Oak Ridge FRC site by adding ethanol, a suitable carbon source, results in efficient nitrate reduction under conditions of elevated nickel, and a decrease of the redox potential such that sulfate and iron reducing bacteria are able to thrive and create conditions favorable for the reduction and in situ immobilization of uranium. Since we have found that the remediation potential resides within the endogenous microbial community, we believe it will be feasible to conduct field tests. RECOMMENDATIONS AND PERSPECTIVES: Biostimulation of endogenous bacteria provides an efficient tool for the successful in situ remediation of mixed-waste sites, particularly those co-contaminated with heavy metals, nitrate and radionuclides, as found in the United States and other countries as environmental legacies of the nuclear age.     

硝酸银沉淀－颗粒物返还法去除COD样品中的氯化物

将样品中的颗粒物分离出来后，向样品中加入适量硝酸银，除去生成的氯化银沉淀，再将预先分离的颗粒物合并到水样中，混匀后测定。经过这样处理，既去除了水样中的Ｃｌ－，又保留了水样中原来的组份，保证了ＣＯＤ测定结果的准确性。     

敞开气氛中硝酸铵热分解过程危险特性的实验研究

利用差热分析仪分析和研究了敞开气氛中硝酸铵的热分解过程,通过在硝酸铵样品中加入酸性物质、KCl、有机物等各种杂质,研究硝酸铵热分解过程的影响因素。结果表明,在敞开气氛中,酸性物质和KCl对硝酸铵热分解过程具有催化作用,有机物会降低硝酸铵的热稳定性,研究结论可以为解决硝酸铵的生产、储存和运输过程中的安全问题提供重要参考。     

同分异构体喹啉和异喹啉的缺氧降解性能比较

研究了同分异构体的含氮杂环化合物喹啉和异喹啉在缺氧条件下的降解情况,发现两者表现出不同的缺氧降解特性。喹啉可以在缺氧条件下得到有效降解,其缺氧降解的最佳碳氮比为8。在最佳碳氮比条件下,喹啉的缺氧降解过程符合一级动力学规律,在其降解过程中首先以硝酸盐为电子受体,当硝酸盐氮浓度为零时,亚硝酸盐氮浓度达到最高,此后喹啉的降解主要以亚硝酸盐为电子受体,并和亚硝酸盐氮同时达到最低浓度。异喹啉对硝酸盐的利用甚微,其降解主要表现为厌氧降解特征,降解过程符合零级动力学规律。     

Denitrification and microbial community in MBBR using A. donax as carbon source and biofilm carriers for reverse osmosis concentrate treatment

In this study,raw Arundo donax(A.donax)pieces were applied as carbon source and biofilm carriers for denitrification in a lab-scale moving bed biofilm reactor(MBBR)for the treatment of reverse osmosis concentrate gathered from local wastewater reuse plant.At stable phase(about 60 days),efficient denitrification performance was obtained with73.2%±19.5%NO_(3-)~-N average removal and 8.10±3.45 g N/(m~3·day)NO_(3-)~-N average volumetric removal rate.Mass balance analysis showed that 4.84 g A.donax was required to remove 1 g TN.Quantitative real-time PCR analysis results showed that the copy numbers of 16S r-RNA,narG,nirS,nosZ and anammox gene of carrier biofilm and suspended activated sludge in the declination phase(BF2 and AS2)were lower than those of samples in the stable phase(BF1 and AS1),and relatively higher copy numbers of nirS and nirK genes with lower abundance of narG and nosZ genes were observed.High-throughput sequencing analysis was conducted for BF2 and AS2,and similar dominant phyla and classes with different abundance were obtained.The class Gammaproteobacteria affiliated with the phylum Proteobacteria was the most dominant microbial community in both BF2(52.6%)and AS2(41.7%).The PICRUSt prediction results indicated that 33 predictive specific genes were related to denitrification process,and the relative abundance of 18 predictive specific genes in BF2 were higher than those in AS2.     

A strategy for enhancing anaerobic digestion of waste activated sludge: Driving anodic oxidation by adding nitrate into microbial electrolysis cell

Cathodic reduction of CO₂ and anodic oxidation of organic matters are crucial to methane-producing microbial electrolysis cell (MEC) applied in anaerobic digestion of waste activated sludge. However, cathodic CO₂ reduction is usually restrained by slow metabolism rates of H₂-utilizing methanogens and low electron-capturing capacity of CO₂, which consequently slows down the anodic oxidation that participates to sludge disintegration. Herein, a strategy with adding nitrate as electron acceptor to foster electronic transfer between the anode and cathode was proposed to improve anodic oxidation. Results showed that the average efficiency of anodic oxidation in the nitrate-added MEC increased by 55.9%. Accordingly, volatile suspended solid removal efficiency in the nitrate-added MEC was 21.9% higher than that of control MEC. Although the initial cumulative methane production in the nitrate-added MEC was lower than that of control MEC, the cumulative methane production in 24?days was 8.9% higher. Fourier transform infrared spectroscopy analysis indicated that anodic oxidation of MEC with nitrate accelerated the disintegration of sludge flocs and cell walls. Calculation on current signal further revealed that anodic oxidation driven by cathodic nitrate reduction was the main mechanism responsible for the improved sludge digestion.     

有机复肥对作物品质的影响初报

对小白菜、茶叶和番茄的大田及盆栽试验表明,与无机肥相比,有机复肥对作物的品质有良好的影响。施用有机复肥使小白菜和茶叶的硝酸盐含量下降,番茄的次果率减少而贮藏期延长。推广有机复肥,对于发展高产、优质、高效农业意义重大。     

Nitrate leaching under vegetable field above a shallow aquifer in Slovenia

In the search for new technologies that would ensure optimum yield and environmental sustainability, various irrigation, nitrogen and cropping system management strategies for the production of vegetables with a shorter growing period were assessed at a benchmark site in Slovenia for the years 2006 and 2007. In the studied years four irrigation and fertilization treatments were applied: (1) 50% drip irrigation of plants water requirements ET_crop and the farmer's practice of fertilisation (broadcasting), (2) fertilisation and 100% drip irrigation (fertigation), (3) the farmer's practice of irrigation (sprinkler irrigation using water stored in plastic tanks) and fertilisation, and (4) control (the farmer's practice of irrigation but no fertilisation). An equivalent of 80, 80 and 200 kg ha⁻¹ of nitrogen (N), 50, 50 and 80 kg ha⁻¹ of phosphorous (P) and 120, 120 and 300 kg ha⁻¹ of potassium (K) was added for iceberg lettuce, endive and cabbage, respectively. Nitrogen (N) labelled fertilizer (¹⁵N) was applied to trace the movement of the applied N fertiliser. The tested irrigation and fertilisation techniques for the production of vegetables with a shorter growing period in the Slovenian climate showed that environmentally sustainable practices (split application of nutrients compared to broadcast incorporating fertilisation) should be a practice of choice in water protection zones. The results confirm that fertigation and improved irrigation scheduling can be an effective way of minimizing nitrate leaching, and should be considered for vegetable production in or close to groundwater protection zones.     

白菜腌制中硝酸盐及亚硝酸盐含量的变化研究

硝酸盐及亚硝酸盐都是对人体有害的物质。文章研究了白菜在腌制过程中硝酸盐及亚硝酸盐含量的动态变化,实验表明亚硝酸盐的形成与白菜的腌制时间、温度、腌制液盐浓度、糖浓度等因素有关;硝酸盐的积累是受白菜的品种以及外部因素比如肥料、光、水分、温度等综合影响,在腌制过程中部分硝酸盐与亚硝酸盐相互转化。实验结果:在12℃的温度下腌制30天以后食用白菜比较好,而且腌制白菜的食盐浓度在10%~15%之间,糖浓度在3%左右较佳。