Biological conversion pathways of sulfate reduction ammonium oxidation in anammox consortia

• The SRAO phenomena tended to occur only under certain conditions. • High amount of biomass and non-anaerobic condition is requirement for SRAO. • Anammox bacteria cannot oxidize ammonium with sulfate as electron acceptor. • AOB and AnAOB are mainly responsible for ammonium conversion. • Heterotrophic sulfate reduction mainly contributed to sulfate conversion. For over two decades, sulfate reduction with ammonium oxidation (SRAO) had been reported from laboratory experiments. SRAO was considered an autotrophic process mediated by anammox bacteria, in which ammonium as electron donor was oxidized by the electron acceptor sulfate. This process had been attributed to observed transformations of nitrogenous and sulfurous compounds in natural environments. Results obtained differed largely for the conversion mole ratios (ammonium/sulfate), and even the intermediate and final products of sulfate reduction. Thus, the hypothesis of biological conversion pathways of ammonium and sulfate in anammox consortia is implausible. In this study, continuous reactor experiments (with working volume of 3.8L) and batch tests were conducted under normal anaerobic (0.2≤DO<0.5 mg/L) / strict anaerobic (DO<0.2 mg/L) conditions with different biomass proportions to verify the SRAO phenomena and identify possible pathways behind substrate conversion. Key findings were that SRAO occurred only in cases of high amounts of inoculant biomass under normal anaerobic condition, while absent under strict anaerobic conditions for same anammox consortia. Mass balance and stoichiometry were checked based on experimental results and the thermodynamics proposed by previous studies were critically discussed. Thus anammox bacteria do not possess the ability to oxidize ammonium with sulfate as electron acceptor and the assumed SRAO could, in fact, be a combination of aerobic ammonium oxidation, anammox and heterotrophic sulfate reduction processes.     

不同喷雾方式下低阻文丘里振弦栅除尘配置优化实验研究

为了对比径向外喷和轴向喷雾下的低阻文丘里振弦栅耦合除尘效果，以除尘效率和系统阻力为参照，选定喉管气速、振弦栅数、纤维丝间隙和喉管液气比进行单因素实验。结果表明2种喷雾方式的除尘效率和系统阻力的变化趋势相同。利用SPSS软件进行4因素3水平正交实验设计，在特定参数条件下，2种喷雾方式的因素影响排序相同，除尘效率为纤维栅数＞纤维丝间隙＞喉管气速＞喷雾量；系统阻力为喉管气速＞纤维栅数＞纤维丝间隙＞喷雾量；径向外喷最佳配置为喉管气速24 m/s、喷雾量2.3 L/min、2块间隙为0.8 mm纤维栅板；轴向喷雾为喉管气速28 m/s、喷雾量2.4 L/min、2块间隙为0.8 mm纤维栅板；在最优配置下的除尘性能为径向外喷＞轴向喷雾。     

液氮泡沫发生器内流动特性研究

低温液氮与泡沫混合液直接接触产生氮气泡沫是一种新型的掺混形式,利用液氮高汽化比的特点,搭建液氮泡沫可视化实验装置,进行氮气-水两相流及液氮泡沫流动特性的研究。结果表明,液氮相变产生大量氮气,其与泡沫液混合产生泡沫,温度有所回升,最终趋于泡沫混合液温度;管路沿程压降较小;液氮射流破碎及流动过程可分为6个区域:低温液氮区、向上循环翻滚区、滞留区、泡沫与泡沫混合液混合区、致密泡沫区、泡沫混合液区。流体向下游流动过程中持续发泡;为防止管路结冰,需合理控制泡沫混合液与液氮流量。     

Nitrogen budget and its environmental loading in an urban ecosystem with the rapid urbanisation of China

A detailed nitrogen (N) budget has been developed for an urban ecosystem based on the method of material flow analysis. How increased human activity and urbanisation influences N cycling have also been analysed. Total N input and output in the urban ecosystem of Zhengzhou City (ZUE) was calculated at 304.8?Gg was 275.3?Gg year^?1, resulting in an N accumulation of 29.5?Gg year^?1. Industry and human life activities, which respectively accounted for 43.8% and 34.2% of total N inputs and 52.6% and 29.1% of total N outputs, were the core of N flow in the urban ecosystem. Humans activities mediated more than 98% N inputs into the ZUE, 73.2% of N was released into the atmosphere and 11.7% into hydrosphere. This very large volume of released N could contribute to regional problems. High energy consumption, insufficient wastewater treatment facility practices, and low N use efficiency are the primary causes of pollution. The major challenge ahead for the urban ecosystem is how to manage high-intensity N pollutant inputs to the urban ecosystems coupled with incomplete N cycling and removal. Based on the analysis of the N budget and loading, this study also proposes an N management strategy for the ZUE.     

北京城区降水对PM2.5和PM10清除作用分析

基于北京市PM_2.5和PM₁₀质量浓度、组分浓度以及降水数据，利用数理统计、相关性分析等方法分别从降水总量、降水时长和降水前颗粒物浓度3个角度研究降水对PM_2.5、PM₁₀的清除作用，同时以一次典型降水过程为例，具体分析降水对颗粒物的影响。结果表明：降水总量的增加有助于促进PM_2.5、PM₁₀的清除，随着降水总量增加，PM_2.5、PM₁₀的平均清除率提高，有效清除的比例增加；连续降水可增强对大气颗粒物的湿清除作用，连续降水达3d可有效降低PM_2.5、PM₁₀浓度；降水对PM_2.5、PM₁₀浓度的清除率和大气颗粒物前一日的平均浓度有较好的正相关性。降水对大气颗粒物的清除可分为清除、回升和平稳3个阶段，各个阶段大气颗粒物的变化趋势不同。降水对于大气气溶胶化学组分和酸碱性的改变具有明显作用，对于大气颗粒物各种组分的清除效果不完全相同。对于大气中OC、NO₃^-、SO₄^2-和NH₄⁺去除率较高，且这4种组分主要以颗粒态形式被冲刷进入降水中，加剧了北京市降水酸化程度。     

The size distribution of airborne bacteria and human pathogenic bacteria in a commercial composting plant

•Bacterial concentrations from eight stages were 10⁴–10⁵copies/m³. •Diameter influenced clustering of bacterial and HPB lineages. •Dg of 8 HPB ranged from 2.42 to 5.09 μm in composting areas. •Dg of 8 HPB ranged from 3.70 to 8.96 μm in packaging areas. •HPB had high concentrations and small sizes in composting areas. Composting plants are regarded as one of the important sources of environmental bioaerosols. However, limitations in the size distribution of airborne bacteria have prevented our comprehensive understanding of their risk to human health and their dispersal behavior. In this study, different sizes of airborne bacteria were collected using an eight-stage impactor from a full-scale composting facility. Size-related abundance and communities of airborne bacteria as well as human pathogenic bacteria (HPB) were investigated using 16S rRNA gene sequencing coupled with droplet digital PCR. Our results indicate that the bacterial concentrations from the eight stages were approximately 10⁴–10⁵copies/m³. Although no statistical correlation was detected between the particle size and the Shannon index, the influence of size on bacterial lineages was observed in both composting and packaging areas. For airborne bacteria from different stages, the dominant phyla were Firmicutes, Proteobacteria, and Actinobacteria, and the dominant genera was Bacillus. Seven out of eight HPB with a small geometric mean aerodynamic diameter had a high concentration in composting areas. Based on diameters of 2.42 to 5.09 μm, most HPB in the composting areas were expected to be deposited on the bronchus and secondary bronchus. However, in the packaging areas, the deposition of HPB (diameters 3.70 to 8.96 μm) occurred in the upper part of the respiratory tract. Our results on the size distribution, abundance, and diversity of these bacteria offer important information for the systematic evaluation of bacterial pathogenicity and the potential health impacts on workers in composting plants and the surrounding residents.     

Wetland Flowpaths Mediate Nitrogen and Phosphorus Concentrations across the Upper Mississippi River Basin

Eutrophication, harmful algal blooms, and human health impacts are critical environmental challenges resulting from excess nitrogen and phosphorus in surface waters. Yet we have limited information regarding how wetland characteristics mediate water quality across watershed scales. We developed a large, novel set of spatial variables characterizing hydrological flowpaths from wetlands to streams, that is, “wetland hydrological transport variables,” to explore how wetlands statistically explain the variability in total nitrogen (TN) and total phosphorus (TP) concentrations across the Upper Mississippi River Basin (UMRB) in the United States. We found that wetland flowpath variables improved landscape-to-aquatic nutrient multilinear regression models (from R² = 0.89 to 0.91 for TN; R² = 0.53 to 0.84 for TP) and provided insights into potential processes governing how wetlands influence watershed-scale TN and TP concentrations. Specifically, flowpath variables describing flow-attenuating environments, for example, subsurface transport compared to overland flowpaths, were related to lower TN and TP concentrations. Frequent hydrological connections from wetlands to streams were also linked to low TP concentrations, which likely suggests a nutrient source limitation in some areas of the UMRB. Consideration of wetland flowpaths could inform management and conservation activities designed to reduce nutrient export to downstream waters.     

A strategy for the next decade to address data deficiency in neglected biodiversity

Measuring progress toward international biodiversity targets requires robust information on the conservation status of species, which the International Union for Conservation of Nature (IUCN) Red List of Threatened Species provides. However, data and capacity are lacking for most hyperdiverse groups, such as invertebrates, plants, and fungi, particularly in megadiverse or high-endemism regions. Conservation policies and biodiversity strategies aimed at halting biodiversity loss by 2020 need to be adapted to tackle these information shortfalls after 2020. We devised an 8-point strategy to close existing data gaps by reviving explorative field research on the distribution, abundance, and ecology of species; linking taxonomic research more closely with conservation; improving global biodiversity databases by making the submission of spatially explicit data mandatory for scientific publications; developing a global spatial database on threats to biodiversity to facilitate IUCN Red List assessments; automating preassessments by integrating distribution data and spatial threat data; building capacity in taxonomy, ecology, and biodiversity monitoring in countries with high species richness or endemism; creating species monitoring programs for lesser-known taxa; and developing sufficient funding mechanisms to reduce reliance on voluntary efforts. Implementing these strategies in the post-2020 biodiversity framework will help to overcome the lack of capacity and data regarding the conservation status of biodiversity. This will require a collaborative effort among scientists, policy makers, and conservation practitioners.     

氨气敏电极法和纳氏试剂分光光度法对地表水中氨氮的比对测试

采用不同质量浓度的氨氮标准样品和实际样品,用氨气敏电极法和纳氏试剂分光光度法进行同步测试。结果表明,2种分析方法在水样氨氮质量浓度在0. 159～2. 81 mg/L范围内具有良好的可比性、精密性和准确性。氨气敏电极法的检出限为0. 03 mg/L,平行6次测定样品的相对标准偏差为0. 4%～4. 2%,加标回收率为85. 0%～110%;纳氏试剂分光光度法的检出限为0. 025 mg/L,平行6次测定样品的相对标准偏差为0. 5%～6. 4%,加标回收率为93. 0%～99. 8%。同时氨气敏电极法在样品预处理、试剂配制和分析时间上要优于纳氏试剂分光光度法。氨气敏电极法能够满足地表水自动监测在线比对实际工作的需求,该方法具有良好的适用性。     

Abundance and removal of antibiotic resistance genes (ARGs) in the rearing environments of intensive shrimp aquaculture in South China

Although research regarding antibiotic resistance genes (ARGs) in aquaculture environments has gained increasing scientific interest, further studies are required to understand the abundances and removal mechanisms of ARGs during the entire rearing period of shrimp aquaculture. Thus, in this study, abundances, distributions and removal rates of ARGs in different environmental compartments of intensive shrimp farms in South China were investigated during the entire rearing period. The results indicated that sul1 and cmlA were the predominant ARGs in the water and sediment samples. Additionally, the total abundance of ARGs was higher in shrimp pond water than in the source water and farm effluent. Moreover, sediment samples indicated significantly higher ARG abundances than water samples from the shrimp ponds (P?<?0.05). Environmental factors were found to significantly affect the distribution of ARGs in shrimp rearing environments. Furthermore, stable ponds aided the removal of ARGs from shrimp pond water. This study accounted for temporal variations in ARG abundances as well as removal of ARGs in different environmental compartments during the entire shrimp rearing period. However, additional research is required to optimize the water treatment process for removal of ARGs from the aquaculture.