2000-2015年中国PM2.5浓度时空分布特征及其城乡差异

近40年来,中国快速经济发展引发较为严重的大气污染,PM_2.5是一种重要的空气污染物,掌握其时空分布规律是对其进行防治的重要前提。基于遥感反演出的PM_2.5浓度数据集,研究了中国2000-2015年PM_2.5浓度的时空分布特征,并基于界定的1376个城镇城区及对应乡村的边界分析了每年PM_2.5浓度值的城乡差异,用线性趋势分析法计算城镇PM_2.5浓度的年际变化速率及显著性。结果表明,研究期内,PM_2.5浓度高于35 μg/m³的面积比例由18.58%增加至32.03%,低于15 μg/m³的面积从43.92%减少到25.12%。PM_2.5污染最严重的地区分布在塔里木盆地、河北南部、河南北部和山东西部。从2000年到2015年,中国绝大多数城镇PM_2.5浓度显著增加,尤其是在东北平原、太行山以东的河北省西南部、燕山以南的北京天津及河北唐山、鲁中南山地丘陵及周围平原地区、华北平原江苏省北部。PM_2.5城乡差异在河北省、山西省两条东北-西南向S形条带区域、浙江省-福建省条带及天山北部绿洲区域较大。研究对PM_2.5高浓度区域、PM_2.5浓度增长较快区域以及城区PM_2.5浓度对乡村影响较大区域进行图示,为中国进一步控制雾霾污染提供一定科学依据。     

广州大夫山雨季林内外空气TSP和PM2.5浓度及水溶性离子特征

采用平行同步采样法,于2012年雨季,对广州市大夫山森林公园林内外空气的总悬浮颗粒物(TSP)和细颗粒物(PM_2.5)样品进行了24 h收集,测定了TSP和PM_2.5的质量浓度并分析了样品中水溶性无机离子成分。结果表明:林内外PM_2.5的质量浓度平均值分别为(40.18±10.47)和(55.79±13.01) g/cm³;林内外TSP的质量浓度分别为(101.32 ± 33.19)和(116.61±35.36) g/cm³。林内与林外比,PM_2.5和TSP平均质量浓度都显著减少(P < 0.05),表明森林能显著改善空气环境质量。TSP和PM_2.5中SO₄^2-、Na⁺、NH₄⁺和NO₃^-为水溶性无机离子主要成分,占总离子质量的80%以上,林外这些离子的浓度高于林内(NH₄⁺除外)。这4种离子雨季在空气中的主要存在方式为NaCl、Na₂SO₄、NH₄HSO₄和NH₄NO₃。计算表明,采样期间海盐对大夫山空气TSP和PM_2.5的水溶性组分中Na⁺和Cl^-贡献最大,其它元素主要源自陆地源。林内外TSP和PM_2.5的c(NO₃^-)/c(SO₄^2-)比值在0.3以下,表明固定源是大夫山森林公园空气主要污染贡献者,TSP中c(NO₃^-)/c(SO₄^2-)的比值大于PM_2.5的比值,说明移动源对TSP的贡献大于PM_2.5。     

深圳市大气污染时空分布及其与景观格局的关系

气溶胶和臭氧是我国大部分地区的两种主要大气污染物,对城市生态环境和人类身体健康影响严重。以深圳市为研究区,利用大气监测站点提供的监测数据和普通kriging空间插值法,从年、季、月尺度上开展近5年（2015-2019）深圳全市PM_2.5和臭氧的时空分布研究,通过皮尔逊分析和显著性检验从月尺度上分析土地覆盖类型及其景观格局对大气污染的影响。结果表明：（1）近5年内深圳市PM_2.5浓度总体呈现下降趋势,臭氧浓度则先降后升,二者季节性和月度差异显著。（2）PM_2.5和臭氧在年、季、月尺度上空间差异明显,全市PM_2.5浓度整体为西北高、东南低;臭氧浓度西北、东南较高,其余区域相对较低。（3）植被占比的增多对PM_2.5浓度有明显的抑制和调控作用,植被斑块间距离越近,对PM_2.5浓度的调控作用越明显;水体占比的增高会导致臭氧浓度增高和变化幅度增大。研究结果可为城市大气污染防治和景观格局规划管理提供参考。     

寒地校园植物群落对大气细颗粒物浓度的消减作用

近年来随着我国城市的快速发展,空气污染作为城市生态环境破坏的首要问题日益严重。因此探究城市绿地中的植物群落是否能够消减大气细颗粒物浓度及其变化特征成为公众和学者广泛关注的焦点。选取位于寒地城市哈尔滨的东北林业大学作为研究对象,通过对校园PM_2.5浓度进行测定和校园植物群落进行调查,定量地分析不同植物群落对PM_2.5浓度的消减作用、PM_2.5浓度的时间变化规律、PM_2.5浓度与温度和空气相对湿度之间的关系。结果显示：（1）PM_2.5浓度日变化呈"双峰单谷"型,早晚偏高;季节变化是夏季PM_2.5浓度最低,秋季PM_2.5浓度最高。（2）不同结构的植物群落对大气细颗粒物的削减效果略有差异,乔灌草配置型绿地的PM_2.5消减率为30.30%,消减效果最佳;乔草和灌草的PM_2.5消减率分别为14.30%和7.77%,消减效果较差。（3）PM_2.5浓度与温度呈负相关关系,与空气相对湿度呈正相关关系。     

北京湿地削减大气PM2.5的生态系统服务流研究

湿地对大气颗粒物的沉降和运移有一定的影响。目前,相关研究多集中在小尺度定量湿地下垫面的颗粒物沉降速度与沉降量以及湿地植物对颗粒物的吸附或阻滞作用。但由于方法的缺失,研究无法在大尺度上定量解释有关湿地对颗粒物的产生、转移、转化和传递过程,这也导致研究结果对政策制定和城市空间规划缺少指导作用。因此,本研究引入了生态系统服务流模型的理论框架,结合颗粒物干沉降与HYSPLIT模型,量化北京市湿地削减PM_2.5服务的物理流量、流动路径以及受益地区。研究结果表明：（1）北京市湿地2015年PM_2.5沉降总量为4240 t,单位面积的平均沉降量为8.27×10^-3 kg/m²;2018年为2610 t,单位面积的平均沉降量为4.46×10^-3 kg/m²;（2）2015年和2018年北京市湿地削减PM_2.5生态系统服务物理流量最高值均出现在冬季,最低值出现在夏季,总体呈现出冬季 > 春季 > 秋季 > 夏季的趋势;（3）2015年和2018年向华北地区迁移的气流轨迹占当季气流轨迹总数的比例最大,京津冀地区与山东省为主要受益区。研究结果既为科学管理湿地资源和实现区域可持续发展提供客观准确的依据,也可为开展湿地生态系统服务流的相关研究奠定一定的基础。     

粤港澳大湾区PM2.5时空分布特征及其与气象要素的关系

细颗粒物（PM_2.5）污染不仅是现代社会城市化进程中的痛点,也是城市大气环境研究不可忽略的重要焦点。粤港澳大湾区作为世界级城市群,既是城市区域经济社会文化发展的重要体现,更是国家区域发展战略的重要构成与政策实施落脚点,其生态环境的优劣尤其受瞩目。对1999-2016年大湾区地表PM_2.5浓度栅格数据集进行了时空分布特征分析,其中空间自相关分析选取莫兰指数（Moran''I指数）作为度量;并利用多元线性回归模型探讨研究区内PM_2.5与气象要素之间关系。结果表明：粤港澳大湾区1999-2016年历年PM_2.5浓度呈先增加后减小的趋势,2008年为时间拐点,该时间节点之后空气质量显著提高,且1999、2009、2016三年,年平均PM_2.5浓度相似值趋于聚集分布。冷热点分析结果表明：热点区域集中于湾区行政核心区域范围内;冷点集中于核心边缘区域,空气质量较优。利用皮尔森相关分析最终筛选出实际蒸散量（aet）、太阳辐射（srad）、最低温度（tmmn）、蒸汽压（vap）、饱和水汽压差（vpd）、风速（ws）等6个气象因子,利用回归分析判断影响PM_2.5浓度时空分布的显著因子。结果表明：本研究区太阳辐射与PM_2.5浓度关系呈负相关,该结果与其他城市相关研究有较大差异,最小温度与PM_2.5浓度呈正相关,风速与PM_2.5浓度呈负相关,饱和水气压差与PM_2.5浓度呈正相关。     

地表植被景观对PM2.5浓度空间分布的影响研究

我国当前城市日益频发的雾霾问题引发公众广泛关注,PM_2.5被认为是雾霾的主要成因。研究认为,在某一区域短时间尺度上（如日）,PM_2.5浓度主要受气象条件影响。但在较长时间尺度上（如季,年）,由于气象条件基本相似,则PM_2.5浓度主要受土地利用特别是地表植被景观的影响。如何耦合地表植被景观格局与PM_2.5浓度信息,定量分析其影响是当前相关科学研究的一个难点,需要引入新思路。首先基于季节气象条件基本相似的科学假设,采用土地利用回归模型分四季高精度模拟PM_2.5浓度空间分布。其次,采用像元二分模型分四季估算研究区植被覆盖度。在此基础上采用随机抽样法通过统计回归模型耦合植被覆盖度与PM_2.5空间分布,定量研究植被覆盖度对PM_2.5分布影响及其尺度效应。研究结果表明：1）植被覆盖度与PM_2.5浓度在本研究选择的空间尺度上,都显著负相关,说明植被覆盖度对PM_2.5具有显著影响;同一个季节不同尺度上,以及不同季节同一尺度上的植被覆盖度对PM_2.5浓度的影响存在一定差异。2）植被覆盖度对PM_2.5浓度的影响方式比较复杂,不同的季节的表现方式不同,总体来说PM_2.5浓度与植被覆盖度曲线回归模型的拟合度高于线性回归模型,说明植被覆盖度对PM_2.5的影响具有非线性特征。3）不同的PM_2.5浓度水平下,植被覆盖度对PM_2.5浓度的影响程度存在差异。PM_2.5浓度越高,植被覆盖度对其浓度的影响越明显。本研究提出的区域尺度耦合地表植被覆盖与PM_2.5浓度的思路与方法,有效的揭示了植被覆盖度对PM_2.5浓度分布的影响方式与尺度效应,为通过优化城市植被缓解大气污染提供一定参考。     

PM2.5对呼吸系统的影响及其作用机制的研究

现如今PM_2.5已成为我国主要的大气污染物,它会导致各种呼吸系统疾病的发生。PM_2.5是粒径小于2.5 μm的细颗粒物,可以携带多种有毒物质。PM_2.5与其他颗粒物相比,体积较小,表面积较大,更容易进入人体,对人体健康造成危害,其中呼吸系统首当其冲。许多流行病学证据表明PM_2.5与呼吸系统疾病密切相关,在体内和体外均证实了细颗粒物对呼吸系统的损伤。而PM_2.5对呼吸系统的毒性机制是国内外专家和学者研究的重点,主要包括氧化应激、炎性损伤、细胞内钙稳态失衡、免疫细胞功能不全和功能障碍、致突变性、微生态学改变、气道上皮防御功能缺陷等。本文综述了PM_2.5的定义、特征和对呼吸系统的影响及毒性机制。     

典型岩溶槽谷区土壤CO2浓度变化对隧道建设的响应——以重庆市中梁山岩溶槽谷为例

为了解重庆市中梁山岩溶槽谷区隧道建设对土壤CO₂浓度变化特征的影响,于2017年12月1日至2018年11月25日对中梁山岩溶槽谷区的隧道影响区和非隧道影响区典型的白蜡树林（FC）和于2017年3月22日-2018年1月18日对耕地（CU）、灌丛（SH）、竹林（BA）下土壤CO₂浓度及其相关的环境因子进行研究,探讨了隧道影响和非隧道影响的岩溶区土壤CO₂浓度变化规律及其影响因子。研究表明：隧道影响区（A区）土壤CO₂浓度低于非隧道影响区（B区）,A区A-CU、A-SH、A-BA和A-FC土壤CO₂浓度的平均值分别为4479.26、6053.10、8152.70 mg/m³和17162.47 mg/m³,B区B-CU、B-SH、B-BA和B-FC分别为6244.67、6647.01、9422.94 mg/m³和18396.09 mg/m³。但隧道影响区和非隧道影响区的土壤CO₂浓度具有相同的垂直和季节变化趋势,在垂直方向上,土壤CO₂浓度随土壤深度的增加而增加,在季节变化上,雨季（夏季和秋季）土壤CO₂浓度大于旱季（冬季和春季）。经相关分析发现土壤温度是影响土壤CO₂浓度变化的主控因子,土壤CO₂浓度随土壤温度的升高而升高,降水较多时土壤含水率过高,会抑制土壤CO₂的生产,同时,土壤理化性质也对土壤CO₂浓度具有一定的影响。隧道影响区土壤CO₂浓度的变化受外界环境变化的影响大。     

基于环境库兹涅茨曲线的我国大气污染防治重点区域环境空气质量与经济增长关系研究

改革开放以来,中国经济迅猛发展,但大气污染等环境问题日益突出。进入21世纪,我国通过颁布实施多项大气污染防治政策,将京津冀及周边地区、长三角地区、珠三角地区等大气污染较严重的区域划定为重点区域,针对性制定治污措施和实施减排工程,努力推动区域环境空气质量改善。基于2000-2019年我国31个省（自治区、直辖市）（以下简称31个省份）GDP,以及SO₂、PM₁₀、NO₂三项大气污染物浓度数据,利用环境库兹涅茨曲线（EKC,Environmental Kuznets Curve）模型,对31个省份和京津冀及周边地区、长三角地区、珠三角地区的经济增长情况、大气污染物浓度演变以及二者之间的关系进行了系统全面的分析评估。研究结果显示：（1）近年来实施的各项大气污染防治政策,特别是2013年以来颁布实施的《大气污染防治行动计划》《打赢蓝天保卫战三年行动计划》,推动环境空气质量改善的同时,促进了经济发展与环境保护长期关系协调性逐步增强,除NO₂浓度呈U型外,31个省份SO₂浓度、PM₁₀浓度与人均GDP的EKC曲线呈倒U型和倒N型,并处于快速下降阶段。（2）京津冀及周边地区SO₂浓度与人均GDP呈倒U型,且处于快速下降阶段;PM₁₀和NO₂浓度均呈现U型关系,且均处于上升期。（3）长三角地区SO₂、PM₁₀浓度与人均GDP呈现倒U型和U型,但均处于下降阶段;NO₂浓度与人均GDP无相关关系。（4）珠三角地区SO₂、PM₁₀和NO₂浓度与人均GDP均呈现倒U型关系,且均处于下降阶段。为此,建议"十四五"期间我国政府要继续实施新一轮的大气污染防治行动计划,聚焦机动车NO_x污染管控,大力推动NO₂浓度稳步下降,以实现我国环境空气质量持续改善,为统筹经济高质量发展和生态环境高水平保护奠定坚实基础。     

Unambiguous through-bond sugar-to-base correlations for purines in 13C, 15N-labeled nucleic acids: The HsCsNb,HsCs(N)bCb,and HbNbCb experiments

Summary A set of three 3D (¹H, ¹³C, ¹⁵N) triple-resonance correlation experiments has been designed to provide H1-H8 intraresidue sugar-to-base correlations in purines in an unambiguous and efficient manner. Together, the H_sC_sN_b, H_sC_s(N)_bC_b, and H_bN_bC_b experiments correlate the H1 sugar proton to the H8 proton of the attached base by means of the {H1, C1, N9, C8, H8} heteronuclear scalar coupling network. The assignment strategy presented here allows for unambiguous H1-H8 intraresidue correlations, provided that no two purines have both the same H1 and C1 chemical shifts and the same C8 and N9 chemical shifts. These experiments have yielded H1-H8 intraresidue sugar-to-base correlations for all five guanosines in the [¹³C, ¹⁵N] isotopically labeled RNA duplex r(GGCGCUUGCGUC)₂.     

Crystal structure of the ternary FimC-FimF(t)-FimD(N) complex indicates conserved pilus chaperone-subunit complex recognition by the usher FimD

Type 1 pili, anchored to the outer membrane protein FimD, enable uropathogenic Escherichia coli to attach to host cells. During pilus biogenesis, the N-terminal periplasmic domain of FimD (FimD(N)) binds complexes between the chaperone FimC and pilus subunits via its partly disordered N-terminal segment, as recently shown for the FimC-FimH(P)-FimD(N) ternary complex. We report the structure of a new ternary complex (FimC-FimF(t)-FimD(N)) with the subunit FimF(t) instead of FimH(p). FimD(N) recognizes FimC-FimF(t) and FimC-FimH(P) very similarly, predominantly through hydrophobic interactions. The conserved binding mode at a "hot spot" on the chaperone surface could guide the design of pilus assembly inhibitors.     

μ- and μ4-η coordination of A2H2 (A = C, Si, Ge, Sn and Pb) ligands with transition metals

The heavier analogs of C₂H₂ have been studied at the B3LYP level for their μ and μ₄-η² coordination properties with the transition metals. Based on known alkyne compounds, transition metal fragments [W₂(μ-NH)(Cp)₂(Cl)₂] and [Fe₄(CO)₁₂] have been chosen. The SBKJC relativistic effective core potentials and their associated basis sets were used on W, Fe, Sn and Pb, and the 6-31G(d) basis set was used on all other elements. All the complexes of Si₂H₂, Ge₂H₂, Sn₂H₂ and Pb₂H₂ are found to be local minima. The trans-twist nature of the ligand A₂H₂ (A = Si-Pb) is large in μ-coordinated complexes of W, and it is very small in μ₄-η² coordinated complexes of Fe. The electronic structure of these complexes was investigated using fragment molecular orbital method (FMO).     

Acetylcholinesterase/Butyrylcholinesterase inhibition activity of some new carbacylamidophosphate deriviatives

Eight newly synthesized carbacylamidophosphates with the general formula RC(O)NHP(O)Cl₂ with R = pCl–C₆H₄ 1a, pBr–C₆H₄ 2a, C₆H₅ 3a, and pMe–C₆H₄ 4a and RC(O)NHP(O)(NC₄H₈O)₂ R = pCl–C₆H₄ 1b, pBr–C₆H₄ 2b, C₆H₅ 3b, pMe–C₆H₄ 4b, were selected to compare the inhibition kinetic parameters, IC₅₀, K_i, k_p and K_D, on human erythrocyte acetylcholinesterase (hAChE) and bovine serum butyrylcholinesterase (BuChE), Also, the in vivo inhibition potency of compound 2a, 2b and 3a, were studied. The data demonstrates that compound 2a and compound 2b are the potent sensitive as AChE and BuChE inhibitors respectively, and the inhibition of hAChE is about 10-fold greater than that of BuChE.     

Antibacterial properties of recombinant human non-pancreatic secretory phospholipase A2

Human non-pancreatic secretory phospholipase A₂ (hnpsPLA₂) is a group IIA phospholipase A₂ which plays an important role in the innate immune response. This enzyme was found to exhibit bactericidal activity toward Gram-positive bacteria, but not Gram-negative ones. Though native hnpsPLA₂ is active over a broad pH range, it is only highly active at alkaline conditions with the optimum activity pH of about 8.5. In order to make it highly active at neutral pH, we have obtained two hnpsPLA₂ mutants, Glu89Lys and Arg100Glu that work better at neutral pH in a previous study. In the present study, we tested the bactericidal effects of the native hnpsPLA₂ and the two mutants. Both native hnpsPLA₂ and the two mutants exhibit bactericidal activity toward Gram-positive bacteria. Furthermore, they can also kill Escherichia coli, a Gram-negative bacterium. The two mutants showed better bactericidal activity for E. coli at neutral pH than the native enzyme, which is consistent with the enzyme activities. As hnpsPLA₂ is highly stable and biocompatible, it may provide a promising therapy for bacteria infection treatment or other bactericidal applications.     

Introduction: A Close Look at the Vacuolar ATPase

The vacuolar ATPases (V-type ATPases) are a family of ATP-dependent ion pumps and found in two principal locations, in endomembranes and in plasma membranes. This family of ATPases is responsible for acidification of intracellulare compartments and, in certain cases, ion transport across the plasma membrane of eucaryotic cells. V-ATPases are composed of two distinct domains: a catalytic V₁ sector, in which ATP hydrolysis takes place, and the membrane-embedded sector, V₀, which functions in ion conduction. In the past decade impressive progress has been made in elucidating the properties structure, function and moleculare biology. These knowledge sheds light also on the evolution of V-ATPases and their related families of A-(A₁A₀-ATPase) and F-type (F₁F₀-ATPases)ATPases.     

Earthworm effects on gaseous emissions during vermifiltration of pig fresh slurry

Treatment of liquid manure can result in the production of ammonia, nitrous oxide and methane. Earthworms mix and transform nitrogen and carbon without consuming additional energy. The objective of this paper is to analyse whether earthworms modify the emissions of NH₃, N₂O, CH₄ and CO₂ during vermifiltration of pig slurry.The experiment used mesocosms of around 50 L, made from a vermifilter treating the diluted manure of a swine house. Three levels of slurry were added to the mesocosms, with or without earthworms, during one month, in triplicate. Earthworm abundance and gas emissions were measured three and five times, respectively.There was a decrease in emissions of ammonia and nitrous oxide and a sink of methane in treatments with earthworms. We suggest that earthworm abundance can be used as a bioindicator of low energy input, and low greenhouse gas and ammonia output in systems using fresh slurry with water recycling.     

Assessing the Impact of Advected African Dust on Air Quality and Health in the Eastern United States

Large quantities of African dust are carried into the southeastern United States each summer with concentrations typically in the range of 10 to 100?µg m^?3. Because approximately one-third to one-half of the dust mass is in the size range under 2.5?µm diameter, the advection of African dust has implications for the EPA's newly implemented standard for PM_2.5 particulate matter and for the assessment of human health effects. It will be difficult to assess the impact of African dust events on air quality because they occur during the summer (maximum in July) when photochemical pollution events are frequent and intense in the eastern United States. Indeed, the presence of dust could affect the evolution of photochemical dust events. In order to assess the role of African dust in air quality in the United States, it will be necessary to develop a set of diagnostic indicators; it appears that dust mineralogy and elemental composition might be useful for this purpose. Various satellite products can be used to characterize the spatial coverage of dust events and, when coupled with meteorological tools, to predict impact regions.     

Crystal structure of the archaeal A1Ao ATP synthase subunit B from Methanosarcina mazei Gö1: Implications of nucleotide-binding differences in the major A1Ao subunits A and B

The A1Ao ATP synthase from archaea represents a class of chimeric ATPases/synthases, whose function and general structural design share characteristics both with vacuolar V1Vo ATPases and with F1Fo ATP synthases. The primary sequences of the two large polypeptides A and B, from the catalytic part, are closely related to the eukaryotic V1Vo ATPases. The chimeric nature of the A1Ao ATP synthase from the archaeon Methanosarcina mazei G?1 was investigated in terms of nucleotide interaction. Here, we demonstrate the ability of the overexpressed A and B subunits to bind ADP and ATP by photoaffinity labeling. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to map the peptide of subunit B involved in nucleotide interaction. Nucleotide affinities in both subunits were determined by fluorescence correlation spectroscopy, indicating a weaker binding of nucleotide analogues to subunit B than to A. In addition, the nucleotide-free crystal structure of subunit B is presented at 1.5 A resolution, providing the first view of the so-called non-catalytic subunit of the A1Ao ATP synthase. Superposition of the A-ATP synthase non-catalytic B subunit and the F-ATP synthase non-catalytic alpha subunit provides new insights into the similarities and differences of these nucleotide-binding ATPase subunits in particular, and into nucleotide binding in general. The arrangement of subunit B within the intact A1Ao ATP synthase is presented.