南海沉积物细菌胞外蛋白酶在家族水平上的多样性

海洋产蛋白酶细菌及其分泌的胞外蛋白酶在降解有机氮以推动海洋氮循环进行方面发挥着重要作用，但目前对这二者多样性的认识非常有限。本研究自南海沉积物中筛选得到90株产蛋白酶细菌，并通过N-端氨基酸序列，分析了其胞外蛋白酶在家族水平上的多样性。16S rRNA基因序列分析的结果表明，筛选的产蛋白酶细菌均属于Gammaproteobacteria纲，且大多数属于Alteromonadales目和Vibrionales目的不同属。对其中14株菌株的14个胞外蛋白酶的N-端氨基酸序列分析表明，所有这些蛋白酶属于金属蛋白酶的M4家族或丝氨酸蛋白酶的S8家族。本研究提供了海洋沉积物产蛋白酶细菌在类群及其胞外蛋白酶在类型上的新细节，这将有助于全面了解微生物酶促降解海洋沉积物有机氮的过程和机理。     

Cu2+对序批式反应器中活性污泥胞外聚合物产量及其组分的影响

研究了长期暴露条件下Cu2+对序批式反应器(SBR)性能及其活性污泥胞外聚合物(EPS)特性的影响。结果表明,进水中加入10 mg·L-1的Cu2+后,在SBR运行的第16~55天,COD和NH+4-N的去除率保持稳定;在第56~75天,COD和NH+4-N的平均去除率与进水Cu2+浓度为0 mg·L-1时相比分别下降了3.88%和6.41%。浓度为10 mg·L-1的Cu2+长期作用下,活性污泥中EPS、松散附着EPS(LB-EPS)和紧密附着EPS(TB-EPS)产量及LB-EPS和TB-EPS中蛋白质(PN)含量增加。傅里叶变换红外光谱分析表明10 mg·L-1 Cu2+的长期暴露导致TB-EPS中PN的C=O键、N-H键和C-O键相对含量降低。X射线光电子能谱(XPS)测试结果显示在10 mg·L-1 Cu2+长期暴露条件下,LB-EPS和TB-EPS中元素Cu和O百分含量增加。     

NaHSO3对两种微藻生长及胞外多糖和藻胆蛋白含量的影响

本文研究了0.25~3 mmol/L浓度的NaHSO3对紫球藻(Porphyridium violaceum)和0.06~0.96 mmol/L浓度的NaHSO3对蓝隐藻(Chroomonas placoidea)的叶绿素荧光参数(PSII最大光能转化效率Fv/Fm、相对电子传递速率rETR、光化学淬灭qP、非光化学淬灭NPQ)、细胞密度、干重、胞外多糖和藻胆蛋白含量的影响。研究表明,较低浓度的NaHSO3对紫球藻和蓝隐藻的生长及活性物质积累有促进作用,2种微藻进行生长和活性物质积累的最适NaHSO3浓度分别为0.5和0.12 mmol/L,此条件下,实验结束时,2种微藻的Fv/Fm、rETR、qP、细胞密度、干重、胞外多糖和藻胆蛋白含量均达到最大值,显著高于对照组。其中,紫球藻的最终细胞密度、干重、胞外多糖和藻胆蛋白含量分别比对照组增加了36.0%、19.1%、71.8%和69.0%。蓝隐藻的上述参数在NaHSO3浓度为0.12 mmol/L时则比对照组增加了60.8%、45.4%、60.0%和53.1%。另一方面,NaHSO3浓度为2~3 mmol/L时显著抑制紫球藻生长及活性物质积累,NaHSO3浓度为0.48~0.96 mmol/L则不利于蓝隐藻生长及活性物质积累。研究结果表明,适合紫球藻和蓝隐藻生长及胞外多糖和藻胆蛋白积累的最佳NaHSO3浓度分别为0.5和0.12 mmol/L,该研究为2种微藻的开发利用提供了理论依据。     

复垦土地样品中石油类物质加速溶剂萃取-荧光分光光度法分析方法研究

作为土地环境质量的一项重要指标,石油类物质含量决定了土地的用途。对于复垦土地样品,在一定程度上反映了污染土地的复垦、治理效果。土壤样中的石油类物质测定方法主要有气相色谱法、红外分光光度法、紫外光谱法等。气相色谱法主要应用于测定样品中的饱和烷烃;红外分光光度法通过测定不同波数下的特征吸收值来表征样品中石油类物质,但采用四氯乙烯为溶剂,试剂环境危害大,前处理效率低,检出限高。本文针对复垦土地样品中石油类物质含量不高,组分多为难挥发且结构复杂、基质干扰大的特点,采用正己烷为溶剂、加速溶剂萃取(ASE)前处理,荧光分光光度计测定样品中的石油类物质。以海洋环境监测石油标准物质为标准样品配制工作曲线,线性相关系数r~2=0.9997;方法检出限为0.40mg/kg,检测下限为1.60mg/kg;实际样品方法精密度为1.10%～8.76%;基质加标回收率为89.0%～95.7%;检测实际样品的结果与现行有效的HJ 1051—2019红外分光光度法基本一致,高含量样品的测定结果高于红外法。本方法所用溶剂正己烷的毒性小于四氯乙烯,前处理方法ASE的自动化程度高,萃取效率高,精密度提高11.5%～67.3%。对于石油类组分结构相对复杂、难提取的样品,本方法检出限低于红外法(4mg/kg)。     

Computational methods for fitting statistical distribution models of multi-site binding equilibria

Statistical distribution models of multi-site binding equilibria have potential applicability in the study of acid-base and metal complexation chemistry of humic substances in soils, sediments, and natural waters. A mathematical derivation is presented for the general continuous model for the case of proton binding; computational methods are described for fitting numerically the parameters in such models. Among models considered are those based on nontruncated, truncated, and bimodal (mixed) distributions. Specific emphasis is placed on Gaussian distribution models.     

Patterns of dissolved organic matter in subarctic peatlands

Samples of water from poor to very rich fens in the Schefferville region of subarctic Quebec revealed strong spatial and temporal variations in dissolved organic carbon (DOC), ranging from 2 to 40 mg 1^?1. Concentrations of DOC tend to increase during the summer and decrease in the autumn, at most sites, which probably reflects increased plant tissue decomposition and higher rates of evapotranspiration. Principal components analysis revealed that DOC is strongly associated with Fe, NO^?₃-N and NO^?₂-N, but essentially independent of other chemical properties of the peat water, such as pH, Ca, Mg, K, P, and NH⁺₄-N. Based on observed concentrations of DOC and estimates of summer runoff (June to September), export of DOC from four peatlands ranges from 1·1 to 4·9 gCm^?2, with the lowest values for peatlands underlain by dolomite. Molecular weight fractionation of four samples revealed significant differences in the dissolved organic matter (DOM), with the largest fractions (GF/C to 10 000 nmw) being dominant in the more acid samples. The ratio of absorbance at 400 and 600 nm wavelengths (E₄:E₆) has been used as a simple indicator of differences in DOM type, ranging from 3 to 15. There is a strong seasonal pattern of increasing E₄:E₆ ratio during the summer at many sites, though this ratio is essentially independent of other chemical properties of peat waters.     

矿物材料应用于香烟过滤嘴降害的研究现状与展望

总结了近几十年来包括活性炭、沸石、蒙脱石、海泡石、麦饭石、凹凸棒石、氧化铝、氢氧化钠、明矾、纳米材料等矿物材料作为卷烟滤嘴添加剂以去除烟气中有毒有害物质的研究和实验应用及效果。实验结果和市场调查表明,活性炭是减少卷烟危害最快、香烟市场应用增长最快的过滤嘴添加剂。从降低卷烟有害成分的比例和成本等综合因素来看,铝硅酸盐类滤嘴和多材料复合滤嘴亦有很好的应用前景和市场需求,应积极进行研制。     

Humic Ion-Binding Model VI: An Improved Description of the Interactions of Protons and Metal Ions with Humic Substances

Humic Ion-Binding Model VI, a discrete site/electrostatic model of the interactions of protons and metals with fulvic and humic acids, is applied to 19 sets of published data for proton binding, and 110 sets for metal binding. Proton binding is described with a site density, two median intrinsic equilibrium constants, two parameters defining the spread of equilibrium constants around the medians, and an electrostatic constant. Intrinsic equilibrium constants for metal binding are defined by two median constants, log K_MA and log K_MB, which refer to carboxyl and weaker-acid sites respectively, together with a parameter, LK₁, defining the spreads of values around the medians. A further parameter, LK₂, takes account of small numbers of strong binding sites. By considering results from many data sets, a universal average value of LK₁ is obtained, and a correlation established between log K_MB and log K_MA. In addition, a relation between LK₂ and the equilibrium constant for metal-NH₃ complexation is tentatively suggested. As a result, metal-binding data can be fitted by the adjustment of a single parameter, log K_MA. Values of log K_MA are derived for 22 metal species. Model VI accounts for competition and ionic strength effects, and for proton-metal exchange.     

A two-dimensional photochemical model of the stratosphere with Rayleigh scattering

Computations of concentrations of minor stratospheric gases using a two-dimensional model of the stratosphere are reported. The model includes Rayleigh scattering. This results in an increase in the photodissociation rate computation time by a factor of 1.5. The effect of ground albedo is assessed by comparing our results with a calculation of photolysis rates for a constant albedo with latitude. Comparison of results with a reference model including only molecular absorption are also made. The largest differences (50%) occur in NO and OH. An approximate expression for including the effects of Rayleigh scattering and surface reflectance in multi-dimensional models is suggested.