基于地统计模型的上海大气污染物多建模方法的比较

地统计模型被广泛应用于环境空气污染物暴露模拟,但不同建模方法及其模拟结果之间的对比研究较少.基于上海2016~2019年55个环境空气监测点位的NO₂和PM_2.5观测数据,以及交通路网、排放源兴趣点和卫星数据等地统计变量,应用偏最小二乘回归（PLS）、监督学习线性回归（SLR）和机器学习随机森林（RF）这3种建模方法创建年暴露模型,并进一步应用普通克里金插值（OK）法分析模型残差,构建复合模型.应用交叉验证对模型的模拟效果进行检验,选取每一种建模方法的最优模型结构（是否应用OK）作为最终模型.结果表明,NO₂模型中表现最好的是RF-OK （R_mse²为0.70~0.82）和PLS-OK模型（R_mse²为0.78~0.84）;PM_2.5模型中PLS模型（R_mse²为0.62~0.71）优于SLR-OK （R_mse²为0.40~0.79）和RF-OK （R_mse²：0.31~0.56）模型.应用3种建模方法对上海1 km网格开展年暴露模拟和对比,NO₂模型间模拟结果的相关性（r为0.82~0.91）高于PM_2.5模拟结果的相关性（r为0.66~0.96）.基于3种模型2019年的模拟结果,评估了上海NO₂和PM_2.5的人群暴露水平.     

Simultaneous monitoring of PCB profiles in the urban air of Dalian, China with active and passive samplings

The concentration of polychlorinated biphenyls (PCBs) in the urban air of Dalian, China was monitored from November 2009 to October 2010 with active high-volume sampler and semipermeable membrane device (SPMD) passive sampler. The concentration of PCBs (particle + gas) ( ∑ PCBs) ranged from 18.6 to 91.0 pg/m 3 , with an average of 50.9 pg/m 3 , and the most abundant dioxin-like PCB (DL-PCBs) was PCB118. The WHO-TEQ values of DL-PCBs were 3.6-22.1 fg/m3 , with an average of 8.5 fg/m 3 , and PCB126 was the maximum contributor to ∑ TEQ. There was a much larger amount of PCBs in the gas phase than in the particulate phase. The dominant PCB components were lower and middle molecular weight PCBs. With increasing chlorination level, the concentration of the PCB congeners in the air decreased. The gas-particulate partitioning of PCBs was different for the four seasons. The gas- particulate partitioning coefficients (logK p ) vs. subcooled liquid vapor pressures (logP L 0 ) of PCBs had reasonable correlations for different sampling sites and seasons. The absorption mechanism contributed more to the gas-particulate partitioning process than adsorption. Correlation analysis of meteorological parameters with the concentration of PCBs was conducted using SPSS packages. The ambient temperature and atmospheric pressure were important factors influencing the concentration of PCBs in the air. The distribution pattern of the congeners of PCBs and the dominant contributors to DL-PCBs and TEQ in active samples and SPMDs passive samples were similar. SPMD mainly sequestrated gas phase PCBs.     

Influence of urban spatial and socioeconomic parameters on PM2.5 at subdistrict level: A land use regression study in Shenzhen, China

The intraurban distribution of PM_2.5 concentration is influenced by various spatial, socioeconomic, and meteorological parameters. This study investigated the influence of 37 parameters on monthly average PM_2.5 concentration at the subdistrict level with Pearson correlation analysis and land-use regression (LUR) using data from a subdistrict-level air pollution monitoring network in Shenzhen, China. Performance of LUR models is evaluated with leave-one-out-cross-validation (LOOCV) and holdout cross-validation (holdout CV). Pearson correlation analysis revealed that Normalized Difference Built-up Index, artificial land fraction, land surface temperature, and point-of-interest (POI) numbers of factories and industrial parks are significantly positively correlated with monthly average PM_2.5 concentrations, while Normalized Difference Vegetation Index and Green View Factor show significant negative correlations. For the sparse national stations, robust LUR modelling may rely on a priori assumptions in direction of influence during the predictor selection process. The month-by-month spatial regression shows that RF models for both national stations and all stations show significantly inflated mean values of R² compared with cross-validation results. For MLR models, inflation of both R² and R²_CV was detected when using only national stations and may indicate the restricted ability to predict spatial distribution of PM_2.5 levels. Inflated within-sample R² also exist in the spatiotemporal LUR models developed with only national stations, although not as significant as spatial LUR models. Our results suggest that a denser subdistrict level air pollutant monitoring network may improve the accuracy and robustness in intraurban spatial/spatiotemporal prediction of PM_2.5 concentrations.     

Variations in stable hydrogen and oxygen isotopes in atmospheric water vapor in the marine boundary layer across a wide latitude range

The newly-developed cavity ring-down laser absorption spectroscopy analyzer with special calibration protocols has enabled the direct measurement of atmospheric vapor isotopes at high spatial and temporal resolution. This paper presents real-time hydrogen and oxygen stable isotope data for atmospheric water vapor above the sea surface, over a wide range of latitudes spanning from 38°N to 69°S. Our results showed relatively higher values of 8180 and 82H in the subtropical regions than those in the tropical and high latitude regions, and also a notable decreasing trend in the Antarctic coastal region. By combining the hydrogen and oxygen isotope data with meteoric water line and backward trajectory model analysis, we explored the kinetic fractionation caused by subsiding air masses and related saturated vapor pressure in the subtropics, and the evaporation-driven kinetic fractionation in the Antarctic region. Simultaneous observations of meteorological and marine variables were used to interpret the isotopic composition characteristics and influential factors, indicating that d-excess is negatively correlated with humidity across a wide range of latitudes and weather conditions worldwide. Coincident with previous studies, d-excess is also positively correlated with sea surface temperature and air temperature （Tair）, with greater sensitivity to Tair. Thus, atmospheric vapor isotopes measured with high accuracy and good spatial- temporal resolution could act as informative tracers for exploring the water cycle at different regional scales. Such monitoring efforts should be undertaken over a longer time period and in different regions of the world.     

被动式采样器与原位鱼体暴露用于监测水体Ah受体效应的比较研究

采用被动式采样器SPMD结合H4ⅡE鼠肝癌细胞离体EROD测试的方法来评价水体中Ah受体效应物质的污染水平.以多环芳烃(PAHs)为目标化合物,在太湖梅梁湾地区选取了5个站点,同时放置SPMD采样器和笼养鲫鱼进行32 d的现场原位暴露实验,然后对SPMD样品提取液进行化学分析和离体EROD测试,对鱼肌肉样进行化学分析和对肝胰脏样进行活体EROD测试.结果表明,随着暴露时间的延长,SPMD样品提取液诱导EROD酶的能力逐渐增强,经过32 d暴露的SPMD样品的提取液其诱导的EROD酶活相当于TCDD的毒性当量值为3.8～6.2 pg/g,而且根据化学分析结果计算的PAHs相当于TCDD的毒性当量值与离体生物测试结果之间相关性很好(R²=0.88),说明PAHs是引起该地区水体EROD效应的一个重要诱导因子;根据化学分析结果而配制的模拟样品的离体EROD测试结果表明,多环芳烃类物质对梅梁湾地区水体Ah受体效应的贡献约为40%～50%.研究还发现,SPMD提取液离体EROD测试结果与同时暴露的鱼体肝胰脏的活体EROD测定结果之间也存在较好的相关性(R²=0.62).因此认为,SPMD结合离体EROD测试的方法能够很好的用于评价水体中Ah受体效应物质的污染水平,并能够用于揭示特定化合物与相应的生物效应之间的定量关系.     

Upper Yellow River air concentrations of organochlorine pesticides estimated from tree bark, and their relationship with socioeconomic indices

Organochlorine pesticide(OCP) concentrations in tree bark from the upper Yellow River region were determined. Total OCP concentrations ranged from 2.7 to 82 ng/g dw, with a mean of 20 ng/g dw. Concentrations of total(Σ) DDTs(0.49–37 ng/g dw), HCHs(0.55–4.5 ng/g dw), and HCB(0.1–1.0 ng/g dw) were much higher than the other OCPs and accounted for 89% of the ΣOCP concentrations. p,p′-DDT was the dominant member of the DDT pesticide group and-HCH was the dominant HCH isomer. The p,p′-DDT/p,p′-DDE and-HCH/-HCH ratios suggested that there were recent DDT and-HCH releases. OCP concentrations in the air were estimated from the tree bark, and the estimated median ΣDDTs, ΣHCHs, and HCB concentrations in the air were 0.09, 0.14, and 0.024 pg/m3, respectively. The relationship between total OCP concentrations and socioeconomic and natural environment indices were assessed using multiple linear regression analysis, and a regression equation including all these factors was obtained. Population density and tertiary industry were the two dominant factors that appeared to affect OCP concentrations in the upper Yellow River region.     

卤代苯化合物水溶解度及正辛醇/水分配系数的三维构效关系研究

对卤代苯化合物的水溶解度(-lg Sw)和正辛醇/水分配系数(lg Kow)分别进行了基于三维结构的比较分子场(Co MFA)和比较分子相似性指数(Co MSIA)分析,建立了三维定量结构-性质相关(3D-QSPR)模型,并将所获结果与密度泛函理论(DFT)方法得到的2D-QSPR模型进行了比较.结果表明:-lg Sw的Co MFA和Co MSIA模型交叉验证相关系数Q2分别为0.902和0.940,决定系数R2分别为0.982和0.986,模型稳定性和估算能力较好;lg Kow的Co MFA和Co MSIA模型Q2分别为0.926和0.988,R2分别为0.983和0.997;本研究所建的3D-QSPR模型的估算能力优于2D-QSPR模型;Co MFA和Co MSIA模型三维等势图表明,取代基的疏水效应对该类化合物的水溶解性能及正辛醇/水分配系数的影响更为显著,立体效应次之,静电场效应影响较小.     

利用LUR模型模拟杭州市PM2.5质量浓度空间分布

模拟城市大气污染物浓度空间分布对研究城市空气质量及人体健康至关重要.本研究利用土地利用回归模型(Land Use Regression,LUR),提取包括污染点源因子、交通因子、人口因子、土地利用因子和气象因子等60个预测因子,基于地理加权算法(GWR)建立春、夏、秋、冬四个季节的模型,实现对杭州地区近地表PM_(2.5)质量浓度空间分布的预测.结果表明:基于地理加权回归算法时,检验模型的R2值分别达到0.76(春季)、0.70(夏季)、0.73(秋季)、0.76(冬季),模型能够解释PM_(2.5)浓度值80%以上的变异.每个季度杭州地区PM_(2.5)浓度变化不尽相同,但总体以杭州中部最高,西南部偏低.研究说明基于LUR模型模拟大尺度地区PM_(2.5)质量浓度空间分布是可行的.     

Evaluating the influence of air pollution on solar radiation observations over the coastal region of Alicante (Southeastern Spain)

The present study evaluates ground-based downward surface shortwave radiation (R_s) over the coastal region of Alicante (Southeastern Spain). Hourly measurements collected over the eleven-year period 2010-2020 are used. Two weather stations located over the region capital, Alicante, have been selected as representative of urban and suburban typologies. Two additional weather stations far from the city have been selected representing rural typologies. R_s is significantly reduced over the urban station during the morning hours within the winter season compared to the observations recorded over the suburban and rural stations, with a global mean difference of -81 and -120 W/m² at 10 LT, respectively. However, no significant differences are obtained during the midday sun, with a global mean difference of -20 W/m² between the urban and rural stations. With the aim of explaining these differences, the current paper investigates the relationship between R_s and different air pollutants: NO_x, SO₂, and fine particulate matter (PM_2.5 and PM₁₀) as well as the wind field measured at the urban and suburban stations. The results found in this work point towards a close relationship between R_s and NO_x concentrations annual cycles, which are also influenced by the prevailing wind circulations observed over the study area. A global mean NO_x concentration of 107 µg/m³ is observed over the urban station at 10 LT during the winter season. In contrast, these high concentrations are significantly reduced over the suburban station, with global mean value of 40 µg/m³ at 10 LT, for this period of the year.     

基于偏最小二乘模型的河流水质对土地利用的响应

流域土地利用类型变化是影响河流水质的重要因素之一.为探究子流域尺度土地利用与河流水质之间的相互关系,本文基于太子河流域遥感影像和水质数据,采用偏最小二乘模型(partial least squares,PLS),分析不同土地利用类型对流域水质的影响程度.选取7个不同子流域土地利用类型面积百分比作为自变量X,总氮(TN)、硝酸根离子(NO_3~-)、氯离子(Cl-)与硫酸根离子(SO_4~(2-))这4个水质参数浓度值作为因变量Y,构建了土地利用类型与河流水质数据的偏最小二乘模型,并使用其余子流域数据对构建的模型进行验证.结果表明,太子河流域不同子流域土地利用类型与河流水质指标TN与NO_3~-之间线性关系显著,决定系数R~20.62.其中,耕地面积变化对水体中TN浓度变化影响明显,居民及工矿建设用地面积变化则对水体中NO_3~-浓度变化影响强烈.但对于Cl-和SO_4~(2-)来说,土地利用类型对其浓度大小有一定影响,但并不是最主要的影响因素.虽然太子河流域未利用地面积百分比极小(1.13%),但是未利用地面积变化对水质参数有较显著影响(影响系数0.24).     

Changes in soil respiration across a chronosequence of tallgrass prairie reconstructions

Close relationships among climatic factors and soil respiration (R_s) are commonly reported. However, variation in R_s across the landscape is compounded by site-specific differences that impede the development of spatially explicit models. Among factors that influence R_s, the effect of ecosystem age is poorly documented. We hypothesized that R_s increases with grassland age and tested this hypothesis in a chronosequence of tallgrass prairie reconstructions in central Iowa, U.S.A. We also assessed changes in root biomass, root ingrowth, aboveground net primary productivity (ANPP), and the strength of soil temperature and moisture in predicting R_s. We found a significant increase in total growing season R_s with prairie age (R² = 0.79), ranging from 714 g C m^?2 in the youngest reconstruction (age 4) to 939 g C m^?2 in the oldest prairie (age 12). Soil temperature was a strong predictor of intra-seasonal R_s among prairies (R² = 0.78–0.87) but mean growing season soil temperature and moisture did not relate to total R_s. The increase in R_s with age was positively correlated with root biomass (r = 0.80) and ANPP (r = 0.87) but not with root ingrowth. Our findings suggest that growing season R_s increases with tallgrass prairie age, root biomass, and ANPP during young grassland development.     

Response surface method for modeling the removal of carbon dioxide from a simulated gas using water absorption enhanced with a liquid-film-forming device

This paper presents the results from using a physical absorption process to absorb gaseous CO_2mixed with N_2using water by producing tiny bubbles via a liquid-film-forming device(LFFD)that improves the solubility of CO_2in water.The influence of various parameters—pressure,initial CO_2concentration,gas-to-liquid ratios,and temperature—on the CO_2removal efficiency and its absorption rate in water were investigated and estimated thoroughly by statistical polynomial models obtained by the utilization of the response surface method(RSM)with a central composite design(CCD).Based on the analysis,a high efficiency of CO_2capture can be reached in conditions such as low pressure,high CO_2concentration at the inlet,low gas/liquid ratio,and low temperature.For instance,the highest removal efficiency in the RSM–CCD experimental matrix of nearly 80%occurred for run number 20,which was conducted at 0.30 MPa,CO_2concentration of 35%,gas/liquid ratio of 0.71,and temperature of 15°C.Furthermore,the coefficients of determination,R~2,were 0.996 for the removal rate and 0.982 for the absorption rate,implying that the predicted values computed by the constructed models correlate strongly and fit well with the experimental values.The results obtained provide essential information for implementing this method properly and effectively and contribute a promising approach to the problem of CO_2capture in air pollution treatment.     

咪唑类离子液体毒性的QSAR/QSPR研究

离子液体因其独特的物化性质广受关注,被誉为"新一代绿色溶剂".用定量结构-性质/活性相关(QSAR/QSPR)方法建立了43种咪唑类离子液体毒性的多元线性回归预测模型,并用10种物质进行了外部测试.模型中包含了启发式算法筛选出的6个结构描述符,其统计数据分别为R2=0.921,R2CV=0.894,F=70.35,S2=0.098,外部测试集的R2=0.952.结果表明,该模型具有良好的可靠性,可用于咪唑类离子液体的毒性预测.     

喀斯特常绿落叶阔叶混交林旱季CO2通量特征及其影响因子

对广西木论国家级自然保护区喀斯特常绿落叶阔叶混交林旱季生态系统CO₂净交换（NEE）的变化特征及其与环境因子的关系进行初步分析，计算研究期间碳汇大小，与其他相似气候条件下的不同生态系统进行对比，以期为准确估算该生态系统的年碳汇量提供基础。利用涡度相关法对该地区旱季（2018年10月1日~2019年3月31日）CO₂通量进行连续观测，同时开展降水量（P）、光合有效辐射（PAR）、空气温度（T_air）、土壤温度（T_soil）以及土壤含水量（SWC）等环境因子监测。观测期内该生态系统CO₂通量及浓度具有明显的"单谷"状日变化特征，白天表现为明显的碳汇，夜间则表现为明显的碳源，NEE在12：00最强，为-0.309±0.330 mg CO₂/（m²·s），18：30最弱，为0.074±0.061 mg CO₂/（m²·s）；观测期内NEE、生态系统呼吸（Re）、生态系统总生产力（GEP）分别为-121.4、209.2、330.6 g C/m²，该生态系统在2019年2月的碳吸收能力最强，Re、GEP在2018年10月达到最强；光合有效辐射是白天生态系统CO₂净交换（NEE_d）变化的主要控制因素（R²=0.40，p<0.01），空气温度与夜间生态系统CO₂净交换（NEE_n）存在指数关系（R²=0.1267，p<0.01）；观测期内的降雨抑制了该生态系统的碳汇能力，即降水对NEE产生了抑制作用。旱季该生态系统整体表现出明显的碳汇，碳汇值为1.214 t C/ha，明显低于相似气候条件下的其他生态系统。     

开顶式气室原位研究水稻汞富集对大气汞浓度升高的响应

采用开顶式气室熏气实验和土壤加汞培育实验,原位研究水稻各器官汞富集对大气汞质量浓度升高的响应关系.结果表明,水稻根中汞含量与大气汞质量浓度无显著相关性(P0.05),与土壤汞含量呈显著正相关(R=0.998 8,P0.05),表明水稻根中的汞主要来自于对土壤中汞的吸收累积.水稻茎中汞含量随大气汞质量浓度的升高呈线性增加(RB=0.964 6,RU=0.983 1,P0.05),且上部茎中汞含量高于下部茎;茎下部汞含量随土壤汞含量的升高呈线性增加(R=0.990 1,P0.05),茎上部汞含量随土壤汞含量的升高呈二次拟合增加(R=0.998 9,P0.05),且下部茎汞含量高于上部茎,说明茎汞含量受土壤和大气汞浓度的共同影响.水稻叶中汞含量与大气汞质量浓度呈显著正相关(R=0.998 5,P0.05),与土壤汞含量也有很好的线性关系(R=0.998 3,P=0.058 5),表明水稻从大气吸收的汞主要积累在叶片中,从土壤吸收的汞主要富集在根中并通过茎部向叶部传输.利用实验建立的函数关系对水稻地上生物质中汞的大气来源估算,至少60%~94%和56%~77%水稻叶和上部茎中的汞来自大气,而大气对下部茎仅贡献8%~56%.由此水稻地上部分生物质汞主要来自对大气汞的吸收,为区域大气汞的收支及汞循环模型提供理论依据.     

西藏色季拉山两种典型天然林分土壤活性有机碳组分与土壤呼吸特征研究

森林土壤活性有机碳和土壤呼吸及其组分区异是森林土壤碳循环过程研究的关键问题.青藏高原亚高山原始森林植被是我国重要的生态屏障,对全球陆地生态系统的碳收支平衡具有举足轻重的作用.本研究选取西藏色季拉山两种最典型的天然林分(急尖长苞冷杉和林芝云杉)为研究对象,测定了这两种林分的土壤活性有机碳含量和同期的土壤呼吸速率及其组分速率,分析了土壤呼吸及其组分与土壤活性有机碳组分之间的关系,结果表明,西藏色季拉山两种天然林分土壤总有机碳(TOC)、土壤颗粒有机碳(POC)、易氧化有机碳(LOC)和微生物量碳(MBC)含量均具有显著的表聚性.急尖长苞冷杉林土壤活性有机碳含量较高,其TOC、POC、LOC、MBC含量分别为57.05 g·kg-1、17.9 g·kg-1、12.2 g·kg-1和365.6 mg·kg-1.两种林分的土壤总呼吸速率(Rt)和微生物呼吸速率(Rh)差异不显著(p0.05),但它们与枯枝落叶呼吸速率(Rl)和根系呼吸速率(Rr)差异极显著(p0.01),同时,Rl和Rr之间差异极显著(p0.01).从不同林分来看,林芝云杉林的土壤总呼吸速率(Rt)和微生物呼吸速率(Rh)高,而急尖长苞冷杉林的枯枝落叶呼吸速率(Rl)和根系呼吸速率(Rr)高.两种林分土壤呼吸各组分对土壤总呼吸速率(Rt)的贡献率大小依次为:RhRlRr.两种林分均表现为微生物呼吸对总呼吸的贡献比例最高,林芝云杉为92.42%,冷杉为70.81%.两种林分的土壤活性碳组分与土壤呼吸关系最密切的是MBC,其次是LOC,最不密切的是POC.     

BP网络框架下MODIS气溶胶光学厚度产品估算中国东部PM2.5

近年来随着中国经济的快速发展,中国区域的大气污染情况日趋严重,大气污染监测与治理已刻不容缓.由于卫星遥感具有较广的空间覆盖、成本低等优点,卫星遥感反演气溶胶光学厚度(AOD)产品被普遍认为是地面PM2.5浓度的重要指标,且已被广泛地应用于地面PM2.5遥感监测.利用2007～2008年的MODIS/Terra气溶胶光学厚度产品,考虑中国东部地区5个大气成分站点风速、风向、温度、湿度和边界层高度等气象数据,构建后向(BP)神经网络,提出了基于MODIS AOD产品估算PM2.5的模型.利用5个大气成分站点PM2.5观测数据对模型进行散点拟合和时间序列拟合验证,结果表明:①从PM2.5观测值与估算值的散点回归分析来看,PM2.5估算值与观测值相关系数最好的为庐山站(R=0.6),其它4个站次之,但其相关系数均在0.4(中强相关)以上;②从PM2.5观测值与估算值的时间序列比对分析来看,PM2.5估算值和观测值差值随时间变化而变化,且存在明显的日际振荡现象,但经相邻5 d滑动平均处理,5个站点的PM2.5估算值与观测值相关系数得到普遍提升,滑动后的相关系数RMA均在0.7以上(除郑州外),庐山RMA达到0.83.结果表明在BP网络框架下,基于MODIS AOD产品估算PM2.5的模型能较好地应用于PM2.5监测.     

Identical full-scale biogas-lift reactors (BLRs) with anaerobic granular sludge and residual activated sludge for brewery wastewater treatment and kinetic modeling

Two identical full-scale biogas-lift reactors treating brewery wastewater were inoculated with different types of sludge to compare their operational conditions, sludge characteristics, and kinetic models at a mesophilic temperature. One reactor （R1） started up with anaerobic granular sludge in 12 weeks and obtained a continuously average organic loading rate （OLR） of 7.4 kg chemical oxygen demand （COD）/（m3.day）, COD removal efficiency of 80%, and effluent COD of 450 mg/L. The other reactor （R2） started up with residual activated sludge in 30 weeks and granulation accomplished when the reactor reached an average OLR of 8.3 kg COD/（m^3·day）, COD removal efficiency of 90%, and effluent COD of 240 mg/L. Differences in sludge characteristics,biogas compositions, and biogas- lift processes may be accounted for the superior efficiency of the treatment performance of R2 over R1. Grau second-order and modified StoverKincannon models based on influent and effluent concentrations as well as hydraulic retention time were successfully used to develop kinetic parameters of the experimental data with high correlation coefficients （R2 〉 0.95）, which further showed that R2 had higher treatment performance than R1. These results demonstrated that residual activated sludge could be used effectively instead of anaerobic granular sludge despite the need for a longer time.     

Survival of Norovirus Surrogate on Various Food-Contact Surfaces

Norovirus (NoV) is an environmental threat to humans, which spreads easily from one infected person to another, causing foodborne and waterborne diseases. Therefore, precautions against NoV infection are important in the preparation of food. The aim of this study was to investigate the survival of murine norovirus (MNV), as a NoV surrogate, on six different food-contact surfaces: ceramic, wood, rubber, glass, stainless steel, and plastic. We inoculated 10⁵ PFU of MNV onto the six different surface coupons that were then kept at room temperature for 28 days. On the food-contact surfaces, the greatest reduction in MNV was 2.28 log₁₀ PFU/coupon, observed on stainless steel, while the lowest MNV reduction was 1.29 log₁₀ PFU/coupon, observed on wood. The rank order of MNV reduction, from highest to lowest, was stainless steel, plastic, rubber, glass, ceramic, and wood. The values of d _R (time required to reduce the virus by 90 %) on survival plots of MNV determined by a modified Weibull model were 277.60 h (R ² = 0.99) on ceramic, 492.59 h (R ² = 0.98) on wood, 173.56 h on rubber (R ² = 0.98), 97.18 h (R ² = 0.94) on glass, 91.76 h (R ² = 0.97) on stainless steel, and 137.74 h (R ² = 0.97) on plastic. The infectivity of MNV on all food-contact surfaces remained after 28 days. These results show that MNV persists in an infective state on various food-contact surfaces for long periods. This study may provide valuable information for the control of NoV on various food-contact surfaces, in order to prevent foodborne disease.     

基于改进的PSO优化LSSVM参数的松花江哈尔滨段悬浮物的遥感反演

悬浮物是松花江水质和水环境评价的重要参数之一.利用在松花江哈尔滨段江面上29个采样点的实测高光谱和悬浮物浓度数据,用20个采样点数据为训练集,9个采样点数据为测试集.将机器学习和全局优化智能计算方法引入,应用改进的粒子群(PSO)优化最小二乘支持向量机(LSSVM)参数,以均方根误差RMSE为适应度函数,根据迭代得到LSSVM最优参数值,用700 nm和750 nm光谱反射率比值(R700/R750)为特征变量,悬浮物数据为目标变量,用训练集数据训练得到反演模型,使用测试集数据进行验证.结果表明,此模型收敛速度快,精度高,得到预测值的均方根误差RMSE为10.11 mg·L-1,平均绝对百分误差MAPE为10.72%,模型决定系数R2为0.952,该方法可用来对其它水质参数反演预测提供参照.