叶菜类蔬菜对海藻碘的吸收与积累特征

以叶菜类蔬菜菠菜、大白菜、生菜、香菜、芥菜和雪菜为研究对象,利用海藻固体碘肥和海藻液体碘肥作为外源碘,在露天和大棚栽培条件下进行蔬菜植物碘强化的田间试验,通过分析蔬菜对碘吸收量的动态变化和碘在蔬菜各器官的分布和分配状况,研究了叶菜类蔬菜对外源碘的吸收与积累特征.结果表明,供试叶菜可食部分中碘的含量随着外源碘添加量的增加而增加;随着取样时间的延后,叶菜可食部分中碘的含量呈现出下降的趋势;喷施液体碘肥比土施固体碘肥更有利于叶菜对碘的吸收和积累,前者使吸收的碘大部分积累在叶面,后者则大部分积累在根部.     

Phosphorus accumulation by bacteria isolated from a ontinuous-flow two-sludge system

In this article, polyphosphate-accumulating organisms （PAOs） from a lab-scale continuous-flow two-sludge system was isolated and identified, the different phosphorus accumulation characteristics of the isolates under anoxic and aerobic conditions were investigated. Two kinds of PAOs were both found in the anoxic zones of the two-sludge system, one of them utilized only oxygen as electron aeceptor, and the other one utilized either nitrate or oxygen as electron aeceptor. Of the total eight isolates, five isolates were capable of utilizing both nitrate and oxygen as electron acceptors to uptake phosphorus to some extent. And three of the five isolates showed good phosphorus accumulative capacities both under anoxic or aerobic conditions, two identified as Alcaligenes and one identified as Pseudomonas. Streptococcus was observed weak anoxic phosphorus accumulation because of its weak denitrification capacity, but it showed good phosphorus accumulation capacity under aerobic conditions. One isolates identified as Enterobacteriaceae was proved to be a special species of PAOs, which could only uptake small amounts of phosphorus under anoxic conditions, although its denitrification capacity and aerobic phosphorus accumulation capacity were excellent.     

Meter-scale variation within a single transect demands attention to taxon accumulation curves in riverine microbiome studies

● Riverine microbiomes exhibited hyperlocal variation within a single transect. ● Certain family-level taxa directionally associated with river center and bank. ● Taxon accumulation curves within a transect urges more nuanced sampling design. Microbial communities inhabiting river ecosystems play crucial roles in global biogeochemical cycling and pollution attenuation. Spatial variations in local microbial assemblages are important for detailed understanding of community assembly and developing robust biodiversity sampling strategies. Here, we intensely analyzed twenty water samples collected from a one-meter spaced transect from the near-shore to the near-center in the Meramec River in eastern Missouri, USA and examined the microbial community composition with 16S rRNA gene amplicon sequencing. Riverine microbiomes across the transect exhibited extremely high similarity, with Pearson’s correlation coefficients above 0.9 for all pairwise community composition comparisons. However, despite the high similarity, PERMANOVA revealed significant spatial differences between near-shore and near-center communities (p = 0.001). Sloan’s neutral model simulations revealed that within-transect community composition variation was largely explained by demographic stochasticity (R² = 0.89). Despite being primarily explained by neutral processes, LefSe analyses also revealed taxa from ten families of which relative abundances differed directionally from the bank to the river center, indicating an additional role of environmental filtering. Notably, the local variations within a river transect can have profound impacts on the documentation of alpha diversity. Taxon-accumulation curves indicated that even twenty samples did not fully saturate the sampling effort at the genus level, yet four, six and seven samples were able to capture 80% of the phylum-level, family-level, and genus-level diversity, respectively. This study for the first time reveals hyperlocal variations in riverine microbiomes and their assembly mechanisms, demanding attention to more robust sampling strategies for documenting microbial diversity in riverine systems.     

基于颗粒污泥的短程反硝化USB反应器启动和运行研究

在2个相同的USB反应器(R1无载体,R2采用多孔生物填料为载体)中构建了短程反硝化工艺,对R1和R2NO₃^--N→NO₂^--N转化性能、短程反硝化颗粒污泥物化特性、胞外聚合物(EPS)产生特性以及微生物功能菌群主要特征进行差异分析.结果表明,反应器运行81d,氮负荷(NLR)为1.2kg/(m³·d)时,NO₃^--N→NO₂^--N转化率(NTR) R2(85%)高于R1(80%);载体颗粒污泥(R2)沉降性能优于自固定化颗粒污泥(R1)且载体颗粒污泥(R2)更容易截留EPS,PN/PS值R1(1.29)>R2(1.15),污泥体积指数(SVI) R1(27.07mL/g MLSS)>R2(19.36mL/g MLSS);扫描电镜发现R1污泥表面聚集长杆菌,R2污泥表面聚集短杆菌和球菌,与R1相比R2颗粒污泥结构更加规则密实.微生物高通量测序结果表明,R2物种丰富度和多样性高于R1,变形菌门、拟杆菌门和绿弯菌门在短程反硝化系统中占主导地位,R1和R2主要NO₂^--N积累功能菌属均为Acinetobacter属(R1-59.18%、R2-46.04%)和Thauera属(R1-6.81%、R2-5.99%).     

黑色岩系地质高背景区土壤锌富集特征与环境活性

锌（Zn）既是生物体必需元素又是有害元素，在复合污染的情况下，Zn在植物吸收、转运和富集镉的过程中发挥着重要作用。以往研究主要关注镉的活性，忽略了Zn的环境活性。基于此，本研究以黑色岩系地质高背景区自然富Zn土壤为对象，重点研究了土壤Zn的活性态和潜在活性态，讨论了Zn活性的影响因素和环境意义。结果表明，研究区土壤Zn富集，平均含量可达457 mg/kg，80%的土壤样品超过我国农用地土壤污染风险筛选值。CaCl₂提取态Zn含量平均值为0.92 mg/kg，平均提取率仅为0.26%，说明研究区土壤Zn的生物活性低，且随着pH升高而降低。EDTA提取态Zn的平均含量为12.7 mg/kg，平均提取率为2.74%，潜在有效态比例也较低。活性态在潜在活性态中占比为7.63%，活化潜力较大，且随着土壤pH的升高而降低。研究区土壤溶液中Zn∶Cd比较低，可能有利于植物对镉的吸收。开展土壤Zn活性的研究，对理解复合污染区土壤镉的活性变化及调控具有重要意义。