长沙市大气颗粒物PM2.5和PM10的时空分布特征

利用 2017—2018 年长沙市空气质量监测数据，分析了长沙市大气颗粒物 PM2.5 和 PM10 的时空 分布特征。结果表明：长沙市大气颗粒物 PM2.5 和 PM10 均表现为冬季 > 秋季 > 春季 > 夏季，冬季浓度最 高，PM2.5 和 PM10 分别为 62.87 和 89.22 μg · m-3；空间变化特征：PM2.5 浓度为长沙城区＞长沙县＞宁乡 县＞望城区＞浏阳市， PM10 浓度为长沙城区＞宁乡县＞长沙县＞望城区＞浏阳市；颗粒污染物 PM2.5 与 PM10 浓度有极显著的线性相关性，r = 0.853，P=0.000（P ＜ 0.01）；降水对大气颗粒物有显著消减作用， 使 PM2.5、PM10 的浓度分别下降了 17.93% 和 27.67%。通过调整能源结构、提倡绿色出行、增加绿量、人 工降水等可有效控制长沙市大气颗粒物污染。     

Y型网式过滤器堵塞过程对有机肥浓度的响应研究

为研究水肥一体化设备中用于过滤有机肥的Y型网式过滤器的堵塞规律,对Y型网式过滤器在初始流量500 L/h、水源压力117.6 k Pa下,设置25、30、40、50 g/L共4种黄腐酸钾有机肥肥液质量浓度,进行了过滤器堵塞试验,分析了Y型网式过滤器的局部水头损失与单个滤孔滤网清洁度(单个滤孔有效过水断面面积与孔隙总面积比值) S/S0的关系,并利用XRD分析了过滤器内堵塞物质的成分。结果表明:肥液质量浓度对过滤器滤网清洁度影响显著,建议肥液质量浓度不超过40 g/L;过滤器局部水头损失在S/S0减小到10%后才逐渐开始增大,过滤器局部水头损失与滤网清洁度、肥液质量浓度有关,利用多项式拟合给出了过滤器滤网清洁度与肥液质量浓度、施肥持续时间的关系式及局部水头损失与肥液质量浓度、滤网清洁度的关系式;滤网堵塞物质主要成分为硫酸钙、草酸钙。本研究结果可为水肥一体化设备中过滤器的选择提供理论参考。     

广西西北喀斯特不同植被不同土层的土壤颗粒有机质

以广西西北喀斯特地区不同植被(草丛、灌丛、原生林)生态系统表层(0～10 cm)及深层(70～100 cm)土壤为研究对象,采用热裂解–气相–质谱(Pyr–TMAH–GC/MS)技术,研究不同植被表层与深层土壤颗粒有机质(POM)的变化特征。结果表明:表层土壤的pH值、有机碳、总氮、总磷、碱解氮、速效磷和速效钾含量均随植被的正向演替呈上升趋势;草丛表层土壤的有机碳、总磷和碱解氮含量均显著高于深层土壤的(P0.05);灌丛表层土壤的有机碳、总氮、总磷、碱解氮、速效磷和速效钾含量均显著高于深层土壤的(P0.05),灌丛表层土壤的pH值和总钾含量显著低于深层土壤的(P0.05);原生林表层土壤的总磷、速效磷和速效钾含量显著高于深层土壤的(P0.05);随着植被的正向演替,土壤POM总量呈增加趋势,表层土壤POM总量显著高于深层土壤的;土壤POM热裂解产物类型主要有木质素类、酚类、芳烃、多环芳烃及脂类化合物,木质素类化合物仅存在于表层土壤,稠环芳烃(此处指除萘和茚外的多环芳烃)占比则随植被的正向演替呈下降趋势;植被显著影响POM总量和POM热裂解产物中对羟基苯基、稠环芳烃、脂肪酸、正构烯烃、萘、氰的占比,土层深度显著影响POM总量和POM热裂解产物中对羟基苯基、愈创木基、丁香酚基、茚、脂肪酸、酮、苯、烷基苯、酚类和氰的占比,植被与土层的交互作用显著影响POM热裂解产物中对羟基苯基、萜烯和脂肪酸的占比;POM总量与有机碳、总氮、总磷、碱解氮、速效钾和速效磷含量呈显著正相关,与容重和总钾含量呈显著负相关,稠环芳烃与有机碳、总氮、总磷、碱解氮、速效磷和速效钾含量呈显著负相关,且碱解氮和pH值显著影响POM化合物组成。可见,在喀斯特地区,土壤POM含量能反映土壤中潜在活性养分含量,可作为喀斯特地区评价不同植被恢复对土壤有机质库及土壤质量动态变化影响的敏感指标。     

基于自适应滤波算法的树木年轮测量方法

为提高树木年轮测量仪的测量精度,提出了一种自适应低通滤波算法对年轮测量仪的直流电机电流信号进行滤波处理。普通低通滤波算法滤波系数固定,当树木年轮宽度发生变化时,既可能保留了部分噪声信号,又可能滤去部分有效的树木年轮信号,因此降低了年轮测量仪的测量精度。自适应低通滤波算法的滤波系数可随滤波器输入值和输出值的变化自动进行调整,提高了噪声滤除效果,减少了有效信号损失。使用自主研发的年轮测量仪测量了大、中、小3种径阶的60个落叶松圆盘,记录直流电机原始电流信号,分别采用自适应低通滤波算法和普通低通滤波算法对原始电流进行滤波处理,根据滤波后的电流波形图,预估圆盘年龄,并计算2种滤波算法的年轮识别正确率。结果表明,自适应低通滤波器年轮识别正确率的平均值为89. 66%,普通低通滤波器年轮识别正确率的平均值为75. 84%;当平均年轮宽度变窄时,自适应低通滤波器的年轮识别正确率从95. 61%下降到82. 02%,下降了13. 59个百分点,而普通低通滤波器的年轮识别正确率从86. 37%下降到62. 30%,下降了24. 07个百分点。表明自适应低通滤波器年轮识别正确率高,自适应能力强,年轮识别精度稳定。     

秸秆碳对不同施肥水平低肥力土壤碳组分的影响

为探明不同施肥水平下秸秆碳对低肥力土壤溶解性有机碳（DOC）、微生物量碳（MBC）和颗粒有机碳（POC）含量的影响，采用碳化硅管原位法，向不同施肥水平（0、120、240 kg·hm^-2，以纯氮计）的低肥力土壤添加¹³C标记小麦秸秆，定期取土样测定不同有机碳组分的含量及其δ¹³C值，并计算秸秆碳在各有机碳库中的转化及贡献比例。研究结果显示，秸秆添加后7 d是快速转化阶段，此后秸秆碳转化渐缓，以向POC转化为主。相较于DOC，秸秆碳更倾向转化为MBC和POC，秸秆添加60 d后的转化比例分别为0.12%~0.38%、4.01%~6.25%和4.74%~9.54%。秸秆添加后，土壤DOC、MBC和POC含量均显著增加，来自于秸秆碳的贡献分别为0.29%~15.01%、13.20%~32.85%和33.62%~59.69%。相较于0、240 kg·hm^-2的施氮处理，施氮量为120 kg·hm^-2时，秸秆添加能同时大幅提高试验土壤的活性和缓效性有机碳库含量。由此表明，秸秆还田条件下，适量施加氮肥更有利于低肥力土壤的培肥与固碳。     

饱和度及干密度对弱膨胀土土水特征曲线影响

采用滤纸法测量不同干密度下试样的总吸力与基质吸力,并绘制相应的土水特征曲线,分析饱和度与干密度对土水特征曲线的影响.实验结果表明:在饱和度一定时,总吸力与基质吸力均随干密度的增大而增大;随饱和度增大,不同干密度的总吸力差值和基质吸力差值逐渐减小;另外,试样的排水速率随饱和度的增大而减小,且干密度越大,排水速率越慢.在较低含水率时,试样的总吸力和基质吸力随干密度的增大而增大,随含水率的增大,干密度对总吸力和基质吸力的影响逐渐弱化.     

地源热泵水蓄能型植物工厂降温系统夏季运行特性

针对田间环境复杂、秸秆形态多样、秸秆覆盖率判断主观性影响过大、补贴面积测量耗时耗力等问题，该文开展了秸秆覆盖率率自动识别方法研究和监测设备研制。首先，提出利用时频变换进行秸秆识别，设计高通滤波器提取了图像的频域特征进行自适应分割。基于集成分类器利用已有的秸秆识别数据训练支持向量机分类器，对秸秆图像进行再识别和筛选。最后，设计多尺度占比滤波器，对识别图像中的噪声和空洞进行修补，生成适应多种情况的秸秆覆盖率识别算法。与北斗定位模块、无线通讯模块、摄像头、传感器、服务器等设备共同组成秸秆覆盖率识别系统。试验结果表明，设备的秸秆覆盖率识别误差为4.55%，平均单张图像耗时0.05 s。研究结果满足保护性耕作中的自动化监测要求，可为保护性耕作作业质量评测提供有效的技术支持。     

Review of Measurement Technologies for Air Pollutants at Livestock and Poultry Farms

With the intensification of livestock breeding, the air quality problem of livestock farms caused by high density breeding is becoming more and more serious. Animal husbandry has become one of the important sources of air pollutants in China. Air emitted from most intensive livestock houses contains a large amount of pollutants, including ammonia, sulfides, particulate matters (PM), volatile organic compounds (VOCs), which not only poses a big threat to animals and workers in livestock farms, but also spreads to the surrounding environment resulting in air pollution. Scientific and applicable air pollutants measuring methods are the basis of monitoring and controlling air pollution in livestock and poultry farms. In this article, the detection methods of livestock farming related hazardous gases (e.g., NH₃, H₂S), greenhouse gases, particulate matters and odor were summarized. The detection methods of hazardous gases in livestock houses mainly include chemical analysis, semiconductor gas sensor detection, spectroscopic methodology and mass spectrometry. The wet-chemical method is cheap and can detect gases sensitively and accurately, while it cannot detect gases in real time, and the process is time-consuming and labor-intensive. The gas tube is cheap and easy to operate, but the deviation is great. Electrochemical sensor is of high sensitivity, moderate cost and can be used to detect gas concentration continuously, however, the devices are easy to age. Spectrum method and mass spectrometry can detect gas quickly and accurately, but it is not suitable for conventional air detection of productive livestock farming due to its high costs. In this paper, the detection methods of greenhouse gases (e.g., CH₄, CO₂) generated from animal intestinal fermentation and livestock environment were also summarized. It is hard to conclude an accurate detection of greenhouse gases in animal husbandry, because the concentrations of greenhouse gases in animal husbandry changes all the time (diurnal and seasonal) and are related to other factors including sampling points. No international common testing method and measurement standard are concluded till now, therefore, the research of greenhouse gases detection method and standard in animal husbandry should be carried out as soon as possible. The detection methods of particulate matters (PM) in livestock farms were reviewed from three aspects: physical, chemical and biological characteristics. PM contains complex components in livestock farms, therefore, it is highly needed to improve PM detection technology. Besides, the component analysis and sensory analysis of odorous substances in livestock farms were overviewed. The odor analysis of professional olfactory discernment personnel owns stronger subjectivity and costs higher than gas chromatography- mass spectrometry. While, using gas chromatography-mass spectrometry is unable to determine all gaseous organic compounds with one sample. Combining gas chromatography and dynamic olfactometer can be more efficient for comprehensive analysis of odor samples. In this article, detection methods and techniques of air pollutants in animal husbandry were comprehensively reviewed to provide a reference for the development of air pollutants detection technologies in livestock and poultry breeding in China.     

Landuse impacts on soil organic carbon fractions in different rainfall areas of a subtropical dryland

Landuse can alter soil organic carbon (SOC) fractions by affecting carbon inflows and outflows. This study evaluated changes in SOC fractions in response to different landuses under variable rainfalls. We compared cropland, grassland and forest soils in high rainfall (Islamabad ~1142 mm) and low rainfall (Chakwal ~667 mm) areas of Pothwar dryland, Pakistan. Forest soils in both rainfall areas had highest SOC (11.32 g kg^?1), particulate organic carbon (POC, 1.70 g kg^?1), mineral-associated organic carbon (MOC, 7.17 g kg^?1) and aggregate-associated organic carbon (AOC, 7.86 g kg^?1). However, in rangeland and cropland soils, these varied with rainfall. Under high rainfall, SOC and MOC were 12% and 17% higher in rangeland than in cropland while POC and AOC were equal. Under low rainfall, SOC and MOC were higher in rangeland than in cropland by 7.21 and 1.79 g kg^?1 at 0–15 cm and equal at 15–30 cm depth. POC and AOC were higher in rangeland than in cropland, in both depths. Averagely, SOC, POC, MOC and AOC were 26%, 68%, 76% and 30% higher in high rainfall than in low rainfall soils. Sensitivity of SOC fractions to landuses observed under different rainfalls could provide useful information for soil management in subtropical drylands.     

森林生态系统中土壤有机质组分的固态13C核磁共振波谱表征

Forest management practices such as prescribed burning and thinning in forest ecosystems may alter the properties of soil organic matter (SOM).In this study,surface soils from field plots in the Bankhead National Forest,Alabama,USA,were used to investigate possible SOM transformations induced by thinning and burning.Elemental analysis and solid-state 13C cross polarization magic angle spinning nuclear magnetic resonance (13C CPMAS NMR) spectroscopy were used to characterize SOM fractions in whole soils,humic substances,and density fractions.Our data revealed that the changes in SOM fractions due to the repeated burning carried out in the forest ecosystem studied were involved mainly with alkyl C,O-alkyl C,and carbohydrate functional groups,implying that most prominent reactions that occurred involved dehydrogenation,de-oxygenation,and decarboxylation.In addition,burning and thinning might have also affected the distribution and composition of free and occluded particulate SOM fractions.The limited structural changes in SOM fractions suggested that low-intensity prescribed fire in the forest ecosystem studied will not create major structural changes in SOM fractions.