Spatiotemporal variations of nitrate sources and dynamics in a typical agricultural riverine system under monsoon climate

Nitrogen pollution is a serious environmental issue in the Danjiangkou Reservoir region (DRR), the water source of the South-to-North Water Diversion Project of China. In this research, seasonal surveys and a bi-weekly time series survey were conducted in the Qihe River Basin, one of the most densely populated agricultural basins in the DRR. Hydrochemical compositions (NO₃^? and Cl^?), dual isotopes (δD-H₂O, δ¹⁸O-H₂O, δ¹⁵N-NO₃^?, and δ¹⁸O-NO₃^?), and a Markov Chain Monte Carlo isotope mixing model were jointly applied to unravel the sources, migrations, and transformations of the nitrate (NO₃^?) in the basin. It was revealed that the mixing between different sources was the main process controlling the isotopic compositions of the riverine NO₃^? in the upper-middle reaches. In contrast, denitrification occurred in the lower reaches. For the first time, the sources of NO₃^? were quantified at a basin scale in the DRR. Overall, the river transported 484.2 tons/year of NO₃-N to the reservoir, of which 32.6%, 36.4%, 28.0%, and 3.0% was from soil organic nitrogen, chemical fertilizer, residential sewage and atmospheric precipitation, respectively. The NO₃-N fluxes of the different sources were regulated by the monsoon climate and anthropogenic activities. For example, high precipitation and intense fertilization resulted in severe nonpoint source pollution. Denitrification thrived in soils and reservoirs in wet seasons. Temperature could regulate the migration, nitrification and denitrification processes. Based on the results, we suggest that the management strategies dealing with nitrogen pollution issue in the DRR should follow the specific spatiotemporal characteristics of NO₃^? sources, migration and transformation mechanisms.     

锑矿冶炼区周边土壤吸附Sb (V)的行为研究

本文通过吸附平衡和动力学实验方法对Sb（V）在锑矿冶炼区周边土壤表面开展吸附行为研究,用常用的等温吸附模型和动力学吸附模型分别对等温吸附曲线和动力学吸附曲线进行拟合。结果表明：Langmuir与Freundlich模型对荒地土和林地土吸附Sb（Ⅴ）的等温吸附曲线均有较好的拟合效果,拟合系数R²0.988。荒地土对Sb（Ⅴ）的吸附能力大于林地土,其吸附量是林地土的2.9±0.2倍,这与Langmuir模型预测的该两种土壤的吸附倍数相当,荒地土表现出强烈吸附Sb（Ⅴ）的能力,尤其在锑浓度较高的体系中更为明显。结合土壤基本理化性质及矿物学特征,认为土壤秥粒、铁矿物和碳酸钙是影响土壤吸附Sb（V）的主要因素。有机质对土壤吸附Sb（Ⅴ）有一定促进作用,但这种影响只表现在Sb（Ⅴ）初始浓度低的条件下;而在Sb（Ⅴ）初始浓度高的条件下,有机质对土壤吸附Sb（Ⅴ）的影响不明显。土壤吸附Sb（Ⅴ）的过程分为快速吸附和慢速吸附两个阶段,快速反应发生在70 min以内。初始浓度低（0.01 mmol/L）的条件下,Elovich方程能够很好地拟合荒地土和林地土吸附Sb（V）的动态曲线;初始浓度高（2 mmol/L）的条件下,双常数方程对荒地土吸附Sb（V）的拟合效果较好,拟一级动力学方程和拟二级动力学方程则适用于拟合林地土吸附Sb（V）的过程。     

Inhibition of thrombin by functionalized C60 nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles (NPs) are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs (C₆₀ NPs) have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C₆₀ NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C₆₀ NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C₆₀ NPs, of greater hydrophobicity and hydrogen bond (HB) donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors. Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C₆₀ NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C₆₀ NPs relevant to their anticoagulation effect.     

气象舒适条件对呼吸系统疾病的影响

采用广义相加模型和分布滞后非线性模型,研究单个气象要素和以"通用的热气候指数"表征的多要素综合效应与北京市2009~2012年呼吸系统疾病急诊人数的暴露-响应关系,并按年龄、性别分层.结果表明,对全人群而言,高温效应即时,低温作用滞后;湿度<30%能显著增加发病风险,且效应持久;3m/s风速对应发病风险最低.少儿（≤ 14岁）受热胁迫影响最强,尤其突出高温高湿作用;成人（15~59岁）受冷胁迫影响强且滞后性;老年患者（>60岁）对冷胁迫敏感,着重防范低温低湿.采用舒适指数探讨环境对呼吸系统疾病的影响优于单要素表征,可加深对发病气象成因的理解,为科学预防、预测预警提供新思路.     

石化企业硫化氢中毒事故分析与防治

介绍了硫化氢的理化性质、危害,分析了如何从硫化氢中毒的预防、检测、作业等环节加强科学化、标准化管理,提出了预防硫化氢中毒的安全管理方法,总结了一些切实可行的做法。     

阿哈水库DOM的分离及其对消毒副产物的贡献

为研究高原喀斯特湖库DOM（dissolved organic matter,溶解性有机质）的组成及其化学特征对DBPs（disinfection by-products,消毒副产物）生成路径的影响,以西南喀斯特地区贵阳市阿哈水库的DOM为研究对象,结合XAD大孔树脂分离技术,通过化学表征〔包括UV-Vis（紫外-可见光光谱）、FTIR（红外光谱）和3D-EEM（三维荧光光谱）〕手段来研究各组分对C-DBPs（含碳消毒副产物）和N-DBPs（含氮消毒副产物）的生成贡献.不同组分芳香性的大小依次为HON（憎水中性物）> HIB（亲水碱）> HOA（憎水酸）> HIN（亲水中性物）≈HIA（亲水酸）> HOB（憎水碱）.憎水与亲水DOM的DBPs生成潜能相近.其中,HON最高,其次为HIB和HOA.HIB和HOA的主要卤代反应位分别来源于藻类有机物的蛋白质和富里酸,而HON的DBPs生成潜能的贡献主要为分子中的芳香和共轭不饱和结构.HIA和HIN的构成主要为脂肪烃,贡献较低的DBPs的生成潜能.对于C-DBPs,THMs和HAAs的生成潜能总体相近,不同组分的差异明显.对于N-DBPs,卤乙腈的生成潜能占80%以上,憎水DOM的贡献较高.DBPs的生成路径从UV-Vis、FTIR和3D-EEM的官能团和特征峰解析结果中均得到了较好的响应.      

GIS在震后应急反应中的应用

震后应急反应是减轻震害的关键措施之一。震后应急的基础在于信息的收集和处理。ＧＩＳ（地理信息系统）具有很强的信息管理能力和空间数据处理、分析能力。借助于这个系统,可以解决以往应急反应中存在的资料分散、资料更新慢、管理费用大以及大量信息难以提取、查询和使用等问题。ＧＩＳ与震后应急反应的结合可以大大提高应急反应的速度和准确性。     

三江源国家公园不同草地土壤微生物功能基因的差异性分析

土壤微生物在陆地生物地球化学循环过程中起着非常重要的作用。为了探索青藏高原高寒草地类型地上植被特性和地下土壤环境与土壤微生物功能基因之间关系,以三江源国家公园高寒草原、高寒沼泽化草甸及高寒草甸3种典型草地类型为研究对象,利用基因芯片(GeoChip 5.0)技术测定其微生物功能基因丰度,并分析它们之间的差异及影响因素。结果表明:(1)3种草地类型地上群落结构和地下土壤环境存在差异性,其中高寒草原物种多样性指数、pH值较高,沼泽化草甸中土壤含水量、微生物量碳、地上生物量、土壤速效氮含量较高,高寒草甸中则是土壤微生物量氮含量较高;(2)3种高寒草地类型的碳循环、氮循环、磷循环、有机修复的土壤微生物功能基因丰度存在显著差异,其中这些功能基因的丰度在高寒沼泽化草甸最高,高寒草甸、高寒草原次之;(3)地上植物物种多样性虽对功能基因丰度变化的解释率(r2)在57.1%-61.2%之间,但统计学上不显著(P>0.05),而微生物基因丰度随地上生物量的增加而增加,且解释率(r2)为77.5%-80.0%(P<0.05)。在pH、土壤含水量、土壤微生物量等地下土壤环境因子中,pH对功能基因丰度存在显著影响(P<0.01)解释率在83.4%-87.5%间,且土壤微生物功能基因丰度随土壤pH的增加而降低;土壤含水量、土壤微生物量对土壤微生物功能基因丰度的解释率分别为81.9%-83.1%(P<0.05)和76.8%-86.2%(P<0.05),微生物功能基因丰度随这两者含量的增加呈上升趋势。进一步运用RDA分析发现,pH、土壤微生物量、地上生物量是影响微生物功能基因丰度的主要因子,其中土壤微生物量是土壤有机质的重要组成部分,土壤有机质又是通过地上植被凋落物沉积所得到的。因此,地上植被特性的自上而下控制因子影响了土壤环境中自下而上的控制因子,间接的影响了微生物功能基因丰度。由此得出,地上植被特性和地下土壤环境因子共同作用控制了微生物功能基因丰度使其出现差异性。     

暗管排水治理渍害田初探

暗管排渍改良低产稻田的试验结果表明,暗管排水显著降低地下水埋探,提高了土壤通透性,减少了土壤中的有毒物质,改善了水稻生长的土壤环境。在宾阳试区和环江试区采用不同水稻品种试验结果表明。与改良前的1989年相比,分别增产53.8％和36.5和36.5％;比同年农艺措施相同的明沟排水田分别增产11.15％和19.93％。     

亚热带森林凋落物层土壤酶活性的季节动态

凋落物分解是森林生态系统养分循环中至关重要的过程。凋落物的分解与凋落物中的分解酶的活性直接相关。本研究调查了亚热带常绿阔叶林与针叶林中与土壤碳氮元素循环有关的β-糖苷酶(β-glucosidase)、内切纤维素酶(endocellulase)和几丁质酶(chitobiase)活性的季节变化规律。结果表明:在两个群落中,3种土壤酶活性与温度之间都有一定相关性,最高值均出现在温度较高的七月份;阔叶林中三种酶的活性在各个季节中大小顺序都为未分解凋落物层(L)>半分解层(F)>腐殖质层(H),而针叶林中则是半分解层(F)>未分解凋落物层(L)>腐殖质层(H);在每个取样时间点β-糖苷酶和几丁质酶的活性最高值都在阔叶林L层,显著高于针叶林L层,而内切纤维素酶的活性最高值是在针叶林H层。两林型下酶活性动态的差异,可能是导致两林型下凋落物层残存量差别的一个重要原因。