The vegetation classification in coal mine overburden dump using canopy spectral reflectance     

Hong SunMinzan Li  Daoliang Li 《Computers and Electronics in Agriculture》2011,75(1):176-180

The canopy spectral characteristics of typical plants in the overburden of the Fuxin coal mine dump were measured and analyzed. The reflectance of Leymus chinensis was affected by the soil, with a slight shift from green (550 nm) to the near infrared (NIR) region. Changes in chlorophyll and water absorption were not significant in the red (670 nm) and NIR bands, respectively. The reflectance curve trend for Artemisia lavandulaefolia was similar to those of Sophora japonica and Ulmus pumila, while the reflectance of S. japonica and U. pumila fluctuated in the NIR region (760-1200 nm), especially with greater water absorption around 930 and 1120 nm. In contrast, the reflectance of A. lavandulaefolia fluctuated slightly around 930 nm and a significant peak appeared at 1127 nm. In addition, the spectral reflectance of S. japonica was lower than for the other species in the visible band (400-700 nm). However, it was higher than for L. chinensis in the NIR region (780-1200 nm). Three classifiers, the self-organizing map (SOM), learning-vector quantization (LVQ), and a probabilistic neural network (PNN), were used to classify the vegetation and the results of all classifiers were compared based on total spectral reflectance data from 400 to 1200 nm. The PNN was the best classifier in terms of training and testing accuracy. The first difference reflectance was calculated, and the red edge parameter was able to classify the herbs (L. chinensis and A. lavandulaefolia) and the arbores (S. japonica and U. pumila) with an accuracy of 77 and 84%, respectively, although it did not perform as well for detail species. A mixing parameter matrix was built based on the sensitive wavelengths (550, 674, 810, 935, and 1125 nm), the vegetation indices (SAVI and NDGI), and the water absorption slope. High classification accuracy was obtained by applying the mixing parameter matrix. This method could be used for revegetation monitoring and in decision making.  相似文献   

Aerodynamic analysis and CFD simulation of several cellulose evaporative cooling pads used in Mediterranean greenhouses     

A. Franco  A. Peña 《Computers and Electronics in Agriculture》2011,76(2):218-230

The present work makes an aerodynamic analysis and computational fluid dynamics (CFD) simulation of the four commercial models of corrugated cellulose evaporative cooling pads that are most widely used in Mediterranean greenhouses. The geometric characteristics of the pads have been determined as well as the volume of water they retain at different flows of water, thus obtaining the mean thickness of the sheet of water which runs down them and their porosity. By means of low velocity wind tunnel experiments, the pressure drop produced by the pads has been recorded at different wind speeds and water flows. In this way it has been possible to obtain the relationship of the permeability and the inertial factor with pad porosity using a cubic type equation. Finally, a CFD simulation with a 3D model has been carried out for both dry pads (Q_w = 0 l s⁻¹ m⁻²) and wet ones (Q_w = 0.256 l s⁻¹ m⁻²), finding good correlation between the simulated and experimental pressure drop, with maximum differences of 9.08% for dry pads and 15.53% for wet ones at an airspeed of 3 m s⁻¹.  相似文献   

贵州省土壤锰的空间异质性及其影响因子          下载免费PDF全文

王烨  刘方  朱健  陈祖拥  刘元生 《农业资源与环境学报》2023,40(4):817-828

为探究贵州省土壤锰（Mn）的空间分布特点,本研究对贵州省376个采样点土壤锰含量进行空间插值,再与贵州省不同类型环境因子分布矢量数据进行叠加分析,利用地理探测器探明土壤锰空间异质的主要影响因子。结果表明,贵州省不同类型土壤锰含量具有明显的差异性,平均含量依次为石灰土>棕壤>红壤>黄棕壤>黄壤>紫色土,表层土壤锰含量范围为2.57~5 203.98 mg·kg^-1,平均值为876.92 mg·kg^-1,变异系数为0.89,具有较强变异性。贵州省依据土壤锰含量水平可划分为低锰区（0~500 mg·kg^-1）、中锰区（>500~700 mg·kg^-1）、富锰区（>700~1 200 mg·kg^-1）、高锰区（>1 200 mg·kg^-1）,全省土壤以富锰水平为主,面积占比达54.05%。空间块金系数达0.51,表明土壤锰分布具有空间中等自相关性。利用地理探测器模型定量评估发现,与锰含量显著相关（P<0.05）的影响因子解释力大小依次为年代地层（0.20）、地质岩性（0.17）、海拔（0.09）、土地利用类型（0.03）;年代地层与地质岩性的组合变化是影响土壤锰空间异质性最主要的因素,在此基础上,海拔和土地利用类型进一步影响土壤锰空间异质性。可见,贵州省土壤锰的空间分布是多种因素共同作用的结果,对区域土壤锰含量水平进行分区有助于指导土地资源的区域生态管理与安全利用。  相似文献   

辽宁省4种主要水果矿质元素含量及其膳食暴露评估   总被引：2，自引：0，他引：2  

匡立学  聂继云  李志霞  毋永龙  闫震  程杨  关棣锴 《中国农业科学》2016,49(20):3993-4003

【目的】针对辽宁省苹果、梨、桃和葡萄4种主要水果开展矿质元素含量及其风险评估研究,明确主要矿质元素含量水平及其对消费者健康的暴露水平,为水果生产和消费提供科学依据。【方法】从主产区(大连、鞍山、营口、锦州、朝阳、葫芦岛和绥中)共采集包括苹果、梨、桃和葡萄在内的140个样品,采用电感耦合等离子体发射光谱仪测定10种矿质元素含量,应用SPSS17.0数据处理软件对不同矿质元素含量水平及相关性进行分析;并分别以日推荐摄入量(RNI)或适宜摄入量(AI)和可耐受最高摄入量(UL)为评价标准,对不同年龄段人群每日从4种水果中摄入矿质元素的量进行分析和暴露评估;再结合居民平衡膳食宝塔和食物成分表,进行成人全膳食风险评估。【结果】10种矿质元素的平均含量由高到低依次为:K(367.68 mg·kg~(-1))P(122.65 mg·kg~(-1))Mg(78.93 mg·kg~(-1))Ca(76.36 mg·kg~(-1))Na(12.37 mg·kg~(-1))B(3.03 mg·kg~(-1))Fe(2.86 mg·kg~(-1))Cu(1.17 mg·kg~(-1))Mn(1.02 mg·kg~(-1))Zn(0.82 mg·kg~(-1)),变异系数范围为27.80%(Mg)—82.05%(Cu);4种水果的K和Mg之间均呈极显著正相关,所测10种矿质元素之间的相关性以正相关为主;不同年龄组人群从4种水果中摄入的矿质元素的量占其RNI或AI的比值分析表明,K元素的比值根据年龄段由低到高呈下降趋势,其余元素按照年龄段变化呈现降-升-降的趋势。Fe最大比值位于4—7岁年龄段,比值为6.54%,其余元素均在2—4岁年龄段比值最高,其中Cu高达83.30%,Mg达11.01%,P、K、Zn、Ca、Na依次为8.57%、8.43%、4.25%、2.46%和0.39%。来自4种水果的膳食风险评估结果表明,Cu元素在2—4岁人群中的平均风险指数和最大风险指数分别为12.50%和37.02%,除Cu以外,来自4种水果的矿质元素摄入风险指数均很低,风险指数远小于100%,风险指数的范围为0.33%(Zn)—13.40%(Mn);用UL为评价标准计算成人全膳食风险,风险评估结果由高到低分别为Mn(53.82%)Fe(49.93%)P(46.27%)Ca(35.23%)Zn(33.50%)Cu(28.61%),风险均低于100%。【结论】4种水果中大量元素K、P、Mg、Ca的含量远高于其他微量元素,水果中矿质元素之间以协同作用为主。各类人群从4种水果摄入矿质元素的量是安全的,Cu元素的风险指数高于其他元素,需重点关注。成人从全膳食中摄入矿质元素的量不会构成健康风险。  相似文献   

Comparative analysis of three chemometric techniques for the spectroradiometric assessment of canopy chlorophyll content in winter wheat   总被引：3，自引：0，他引：3  

Clement Atzberger  Martine Guérif  Willy Werner 《Computers and Electronics in Agriculture》2010,73(2):165-173

Hyperspectral data sets contain useful information for characterizing vegetation canopies not previously available from multi-spectral data sources. However, to make full use of the information content one has to find ways for coping with the strong multi-collinearity in the data. The redundancy directly results from the fact that only a few variables effectively control the vegetation signature. This low dimensionality strongly contrasts with the often more than 100 spectral channels provided by modern spectroradiometers and through imaging spectroscopy. With this study we evaluated three different chemometric techniques specifically designed to deal with redundant (and small) data sets. In addition, a widely used 2-band vegetation index was chosen (NDVI) as a baseline approach. A multi-site and multi-date field campaign was conducted to acquire the necessary reference observations. On small subplots the total canopy chlorophyll content was measured and the corresponding canopy signature (450-2500 nm) was recorded (n_obs = 42). Using this data set we investigated the predictive power and noise sensitivity of stepwise multiple linear regression (SMLR) and two ‘full spectrum’ methods: principal component regression (PCR) and partial least squares regression (PLSR). The NDVI was fitted to the canopy chlorophyll content using an exponential relation. For all techniques, a jackknife approach was used to obtain cross-validated statistics. The PLSR clearly outperformed all other techniques. PLSR gave a cross-validated RMSE of 51 mg m⁻² for canopy chlorophyll contents ranging between 38 and 475 mg m⁻² (0.99 ≤ LAI ≤ 8.74 m² m⁻²). The lowest accuracy was achieved using PCR (RMSE_cv = 82 mg m⁻² and ). The NDVI, even using chlorophyll optimized band settings, could not reach the accuracy of PLSR. Regarding the sensitivity to artificially created (white) noise, PCR showed some advantages, whereas SMLR was the most sensitive chemometric technique. For relatively small, highly multi-collinear data sets the use of partial least square regression is recommended. PLSR makes full use of the rich spectral information while being relatively insensitive to sensor noise. PLSR provides a regression model where the entire spectral information is taken - in a weighted form - into account. This method seems therefore much better adapted to deal with potentially confounding factors compared to any 2-band vegetation index which can only avoid the most harmful factor of variation.  相似文献   

不同苹果品种果实矿质元素含量的因子分析和聚类分析   总被引：8，自引：0，他引：8  

匡立学  聂继云  李志霞  关棣锴  毋永龙  闫震  程杨 《中国农业科学》2017,50(14):2807-2815

【目的】研究不同苹果品种果实矿质元素含量特征,为苹果营养功能评价、苹果消费以及苹果育种亲本选择等提供科学依据。【方法】以125个品种的苹果果实为试材,测定K、P、Mg、Ca、Zn、Cu和Mn 7种矿质元素指标,应用因子分析和聚类分析对矿质元素含量进行分析。【结果】7种矿质元素的平均含量由高到低依次为:K(1 112.72 mg·kg~(-1))P(119.59 mg·kg~(-1))Mg(65.69 mg·kg~(-1))Ca(56.96 mg·kg~(-1))Zn(0.69 mg·kg~(-1))Cu(0.66 mg·kg~(-1))Mn(0.63 mg·kg~(-1)),变异系数范围为19.4%(Mg)—43.9%(Cu)。K、P、Mg、Ca之间存在显著差异(P0.05),Zn、Cu、Mn之间差异不显著。K-S检验表明7种矿质元素含量均服从正态分布。因子分析结果表明,苹果的特征矿质元素为Cu、K、Mg、P和Mn,提取的4个公因子累积方差贡献率为86.30%,因子1(F1)主要综合了Cu、K、Mg、P 4种矿质元素的信息,得分排名前3位的苹果品种依次为‘秋锦’‘五月’‘国庆’;F2代表Mn元素,排名前3位的苹果品种依次为‘斯塔克矮生’‘春香’和‘黄魁’;F3代表Zn元素信息,排名前3位的苹果品种依次为‘燕山红’‘Szampion’和‘4-23’;F4代表Ca的信息,排名前3位的苹果品种依次为‘新倭锦’‘伏锦’和‘太平洋玫瑰’。综合得分排名前5名的苹果品种由高到低依次为‘秋锦’‘五月’‘新国光’‘北斗’‘长红’。聚类分析将125个苹果品种分为5类,第1类包含9个苹果品种,这些苹果品种Ca很高;第2类包含28个苹果品种,Cu含量较高;第3类包含23个苹果品种,这些苹果品种Zn含量较高;第4类包含44个品种,这些苹果品种Ca、Cu、K、Mg、P、Zn含量均很低;第5类包含21个样品,这些苹果品种K、Mg、Mn、P含量均较高,Zn含量较低。【结论】苹果中K、Mg、Cu、P两两之间分别呈极显著正相关,相关系数均在0.5以上。Cu、K、Mg、P和Mn是苹果的特征矿质元素。不同品种苹果间7种矿质元素的组成存在差异,可分为5类,即高钙品种、高铜品种、高锌品种、高钾镁锰磷品种和低矿质元素品种。  相似文献   

水稻秸秆生物炭对镉污染农田中番茄产量和品质的影响机制     

吴伟健  陈艺杰  李高洋  张伟健  林海虹  蔺中  甄珍 《农业环境科学学报》2022,41(3):492-503

为探究不同比例生物炭对镉污染农田中番茄产量和品质及其体内镉累积的影响,以千禧番茄（Lycopersicon esculentumMill.）为材料,设计4个处理（CK：不添加生物炭;T₁：1%生物炭;T₂：3%生物炭;T₃：5%生物炭）,采用盆栽试验研究了不同处理下番茄根系、茎部和果实中镉的累积、产量与品质和土壤理化性质与酶活性的差异。结果表明：与CK处理相比,添加生物炭显著提高了番茄的产量和品质（维生素C、番茄红素、可溶性蛋白、可溶性糖含量和糖酸比）,其中T₂处理的品质提升效果最显著,分别较CK处理提高了24.7%、114.4%、12.0%、37.4%和80.0%。添加生物炭可显著降低番茄体内（根系、茎部和果实）镉含量,其中T₃处理的效果最显著,在生长末期,T₃处理番茄根系、茎部和果实中的镉含量分别为1.31、0.33 mg·kg^-1和0.03 mg·kg^-1。此外,在番茄的整个生育期中添加生物炭可显著改善土壤理化性质（pH和腐殖质）,提高土壤养分含量（碱解氮、速效磷和速效钾）和酶活性（脲酶、过氧化氢酶、蔗糖酶和纤维素酶）,其中在生长末期,T₂处理的碱解氮、速效磷、速效钾含量和脲酶、过氧化氢酶、蔗糖酶和纤维素酶活性显著高于其余处理,依次为47.42、165.85、167.76 mg·kg^-1和6.28 mg·g^-1·d^-1、3.20 mg·g^-1·20 min^-1、1.07 mg·g^-1·d^-1和2.13 mg·g^-1·d^-1;T₃处理对pH、腐殖质含量提高效果最为明显,分别为7.15和24.56 g·kg^-1,但与T₂处理无显著差异。研究表明,添加生物炭可显著降低番茄体内镉含量,改善土壤理化性质并提高土壤养分含量,进而提高番茄的产量和品质,其中以3%生物炭处理效果最佳。同时,添加生物炭显著提高了土壤的酶活性,改善土壤的生态环境。  相似文献   

水生植物对生态沟渠底泥磷吸附特性的影响   总被引：8，自引：3，他引：8  

李红芳  刘锋  肖润林  何洋  王迪  吴金水 《农业环境科学学报》2016,35(1):157-163

以用于小流域源头区农业面源污染防控的3条生态沟渠为研究对象,采集入口处(S1)、中间段(S2)和出口处(S3)沟渠底泥,分析其属性和磷吸附特性。结果表明,沟渠底泥全磷含量在0.19~0.60 g·kg~(-1)范围内,且沿水流方向有增大趋势;草酸提取态磷(Pox)及有机质含量与全磷含量呈显著正相关(P0.01,R2=0.920和P0.05,R2=0.549,n=9);而底泥的p H值则随着水流方向有降低的趋势。Langmuir方程拟合吸附数据发现,底泥吸附/解吸平衡磷浓度(EPC0)、磷最大吸附量(Smax)和磷吸附键能参数(Kc)分别为0.08~0.38 mg·L~(-1)、555.6~909.1 mg·kg~(-1)和0.18~0.52 L·mg~(-1)。样点S2(挺水植物梭鱼草和沉水植物绿狐尾藻交接种植区)的Smax最大、EPC0最小,样点S3次之,而样点S1的Smax最小、EPC0最大。这说明水生植物的种植和合理配置,不仅能够影响底泥基本属性的变化,且能增强底泥对磷的吸附作用,有利于降低生态沟渠的磷输出风险。  相似文献   

重庆三峡库区鲍威尔脐橙花期叶片矿质营养诊断   总被引：2，自引：0，他引：2  

郑永强  王娅  杨琼  贾学梅  何绍兰  邓烈  谢让金  易时来  吕强  马岩岩 《中国农业科学》2018,51(12):2378-2390

【目的】通过对重庆三峡库区江津和奉节鲍威尔脐橙果园叶片矿质元素测定并进行叶片营养状况诊断,为鲍威尔脐橙高产优质施肥方案的制定提供依据。【方法】以重庆三峡库区江津和奉节40个代表性12年生枳橙砧鲍威尔脐橙小区植株为试材,通过测定盛花期叶片中氮（N）、磷（P）、钾（K）、钙（Ca）、镁（Mg）、铁（Fe）、铜（Cu）、锰（Mn）、锌（Zn）元素的含量和小区产量,运用叶片营养组分分析法(CND)、诊断施肥综合法(DRIS)和标准含量适宜偏差百分数法(DOP)3种方法对两个地区低产组叶片营养状况进行诊断。【结果】根据CND拐点法确定高产园划分临界值为330 t·hm^-2,其中仅有奉节地区6个小区满足此条件,占总样本15.0%,同时依据高产组叶片N、P、K、Ca、Mg、Fe、Mn、Cu和Zn等各营养元素含量范围确定上述元素适宜值分别为N(2.0±0.1)%、P(0.12±0.01)%、K(2.1±0.5)%、Ca(3.1±0.4)g·kg^-1 DW、Mg (0.31±0.03)g·kg^-1 DW、Fe(36.6±13.1)mg·kg^-1 DW、Mn (51.4±21.6)mg·kg^-1 DW、Cu(2.2±0.7)mg·kg^-1 DW和Zn(12.3±1.5)mg·kg^-1 DW;建立不同营养元素CND法叶标准参比值为V_N*=3.62±0.07,V_P*=0.78±0.08,V_K*=1.36±0.21,V_Ca*=1.74±0.14,V_Mg*=-0.55±0.10,V_Fe*=-2.74±0.36,V_Mn*=-2.40±0.39,V_Cu*=-5.55±0.32,V_Zn*=-3.78±0.10;依据DRIS法对江津地区筛选出N/K、N/Fe、N/Cu、P/K、P/Fe、P/Cu、K/Fe、K/Cu、Ca/N、Ca/P、Ca/K、Ca/Fe、Ca/Mn、Ca/Cu、Mg/N、Mg/P、Mg/K、Mg/Fe、Mg/Cu、Mn/N、Mn/P、Mn/K、Mn/Mg、Mn/Fe、Mn/Cu、Mn/Zn、Zn/Ca、Zn/Mg、Zn/Fe、Zn/Cu等30个,奉节地区筛选出Ca/K、Mg/K、Mg/Zn、Mn/N、Mn/P、Mn/K、Mn/Ca、Mn/Mg、Mn/Fe、Mn/Cu、Cu/P、Cu/K、Cu/Mg、Cu/Fe等14个叶片营养浓度比值参数;根据叶片矿质元素含量适宜值采用CND、DRIS、DOP 3种方法对奉节低产小区和江津地区橘园盛花期叶片营养诊断。其中,CND法需肥顺序：江津为Ca＞Mg＞N＞P＞Mn,奉节为N＞Ca＞P＞Zn＞Fe＞Mn;DRIS法需肥顺序：江津为Ca＞Mg＞＞Mn＞N＞P,奉节为Zn＞＞Fe＞Ca＞Mn＞N＞Mg;DOP法需肥顺序,江津为Ca＞Mn＞Mg,奉节为Mn＞＞Zn＞Fe＞Ca＞Mg＞N。【结论】3种方法诊断结果表明,果园营养不平衡指数江津地区CND、DRIS、DOP分别为166.5、4 291.0、117.5,奉节低产小区分别为37.2、570.0、14.1,奉节果园营养平衡状况均优于江津,两产区均具有很大的增产潜力。  相似文献   

黑麦草抗氧化酶对Cd、Zn和Pb复合污染的响应   总被引：1，自引：1，他引：1  

张军  王文科  耿雅妮  任雪盈  王周锋  曹书苗 《农业环境科学学报》2018,37(6):1117-1124

为研究植物抗氧化酶活性与重金属复合污染之间的关系,通过土培正交实验考察重金属Cd(0、10、20、30、40、50 mg·kg~(-1))、Zn(0、150、250、350、450、550 mg·kg~(-1))、Pb(0、100、300、500、700、900 mg·kg~(-1))复合污染在不同胁迫时间(14、21、28、35 d)对黑麦草过氧化氢酶(CAT)、过氧化物酶(POD)和超氧化物歧化酶(SOD)活性的影响。结果表明,Cd对CAT和POD起激活作用,对SOD起抑制作用;Zn和Pb对CAT和POD起抑制作用,对SOD起激活作用。在重金属复合污染胁迫下,POD和SOD活性随着培养时间的延长而显著增加,在28 d和35 d时达到最大,分别为对照的260%和637.4%。考虑交互作用,SOD活性对Cd×Zn、Cd×Pb、Zn×Pb有显著响应(P0.05)。3种抗氧化酶中,SOD活性对重金属污染反应最敏感,可以作为表征重金属污染的指示指标。  相似文献   

阿苯达唑对蚯蚓若干生化指标的影响     

丛琳  武瑞  李银生 《农业环境科学学报》2016,35(7):1264-1270

采用人工污染土壤的方法进行阿苯达唑的蚯蚓毒性试验,设计阿苯达唑的暴露浓度为0、50、100、200、400、600 mg·kg-1,暴露实验进行3、7、14、28 d后,分别检测蚯蚓体内超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)、谷胱甘肽转移酶(GST)活性和丙二醛(MDA)含量。结果表明,在供试浓度范围内,蚯蚓体内各生化指标对污染物暴露指示的敏感性存在差异,敏感性大小为:MDAGSTSOD≈CATPOD。400 mg·kg-1和600 mg·kg-1浓度下,阿苯达唑能够引起蚯蚓机体的氧化应激响应。这些敏感的生化指标可以用作阿苯达唑生态毒理的生物标志物。  相似文献   

多环芳烃(菲)添加对珠江河口农村和城市河流湿地土壤氮矿化过程的影响   总被引：2，自引：1，他引：1  

尹硕  白军红  温晓君  张光亮  韩玲  胡星云 《农业环境科学学报》2019,38(3):600-608

为研究多环芳烃(菲)添加对珠江口河流湿地土壤氮矿化的影响,选取珠江三角洲番禺区的农村河流和城市河流湿地,采用鲜土对两种湿地土壤添加3种浓度的菲(0、15、100 mg·kg-1)进行为期42 d的室内培养实验,分析了两类湿地土壤氮矿化速率以及影响氮矿化过程的脲酶活性及氨氧化古菌(AOA)与氨氧化细菌(AOB)的比例变化。结果表明:土壤氮矿化速率变化范围为-4.885～5.877 mg·kg-1·d-1,氨化速率变化范围为-3.823～4.677 mg·kg-1·d-1,硝化速率变化范围为-4.990～5.369 mg·kg-1·d-1。所有处理中脲酶活性均呈下降趋势,下降比例在26.1%～83.4%的范围内。多环芳烃添加处理组下降比例显著小于无添加对照组(P0.05),而农村河流湿地中的高浓度处理组除外(P0.05)。农村河流湿地中,无添加和高浓度处理下培养后的AOB在氨氧化过程中的占比比培养前减少25.85%和7.31%,低浓度添加则增加36.37%。而菲添加对城市河流湿地AOA和AOB两者比例变化的影响较小。研究表明,除高浓度多环芳烃添加利于城市河流湿地土壤氮矿化外,其他添加实验均显示多环芳烃不利于土壤氮矿化。与对照组相比,多环芳烃的添加对土壤脲酶活性有促进作用(农村河流湿地高浓度处理除外)。在农村河流湿地土壤中,AOB对多环芳烃适应性比AOA更强,低浓度适应性最高,而多环芳烃对城市河流湿地土壤氨氧化微生物群落结构基本无影响。  相似文献   

Assessing effect of wind tunnel sizes on air velocity and concentration boundary layers and on ammonia emission estimation using computational fluid dynamics (CFD)     

Chayan Kumer SahaGuoqiang Zhang  Bjarne Bjerg 《Computers and Electronics in Agriculture》2011,78(1):49-60

The objective of this study was to investigate the effect of different geometric sizes of wind tunnels on aerial boundary layers above the emission surface and therefore their effect on ammonia emission using CFD tool. Five wind tunnels of different sizes were used for the CFD simulation. Detail experimental measurements on air velocity and concentration profiles above the emission surface were realised using average inlet velocities of 0.1, 0.2, 0.3, and 0.4 m s⁻¹ in two wind tunnels under isothermal condition. The TAN (Total Ammoniacal Nitrogen) and pH of ammonia aqueous solution were kept constant during the experiments. The boundary conditions necessary for the CFD study were obtained from the measured experimental data. The CFD model used for simulations was first validated using the data from the two wind tunnel experiments. For assessing the effects of wind tunnel size, the air velocity range of 0.1-0.6 m s⁻¹ was used in CFD investigations. It was found that the velocity and concentration boundary layer thickness decreased with the increase of inlet air velocity where the concentration boundary was thinner than the corresponding velocity boundary layer. Wind tunnel sizes affected both velocity and concentration boundary layer thicknesses (P < 0.001). The velocity and concentration boundary layer was thicker in a wind tunnel with larger heights than in small height. The over estimation of ammonia emission of smaller wind tunnels were observed comparing to the largest wind tunnel or open field situation (P < 0.001). Non-linear regression equations were developed using four wind tunnels data for velocity boundary layer thickness (δ_u), concentration boundary layer thickness (δ_c), and ammonia mass transfer coefficient (k_G) as a function of wind tunnel height (H) and average inlet velocity (u_m), which given clear quantitative indication of effects of H, and u_m on δ_u, δ_c, and k_G, respectively.  相似文献   

Use of ground based hyperspectral remote sensing for detection of stress in cotton caused by leafhopper (Hemiptera: Cicadellidae)   总被引：2，自引：0，他引：2  

M. Prabhakar  Y.G. PrasadM. Thirupathi  G. SreedeviB. Dharajothi  B. Venkateswarlu 《Computers and Electronics in Agriculture》2011,79(2):189-198

Detection of crop stress is one of the major applications of hyperspectral remote sensing in agriculture. Many studies have demonstrated the capability of remote sensing techniques for detection of nutrient stress on cotton with only few on pest damage but none so far on leafhopper (LH) severity. Subsequent to introduction of Bt cotton, leafhopper is emerging as a key pest in several countries. In view of its wide host range, geographical distribution and damage potential, a study was initiated to characterise leafhopper stress on cotton, identify sensitive bands, and derive hyperspectral vegetation indices specific to this pest. Cotton plants with varying levels of LH severity were selected from three locations across major cotton growing regions of India. About 57-58 cotton plants from each location exhibiting different levels of LH damage symptoms were selected. Reflectance measurements in the spectral range of 350-2500 nm were made using hyperspectral radiometer. Simultaneously chlorophyll (Chl) and relative water content (RWC) were also estimated from the selected plants. Reflectance from healthy and leafhopper infested plants showed a significant difference in VIS and NIR regions. Decrease in Chl a pigment was more significant than Chl b in the infested plants and the ratio of Chl a/b showed a decreasing trend with increase in LH severity. Regression analysis revealed a significant linear relation between LH severity and Chl (R² = 0.505^∗∗), and a similar fit was also observed for RWC (R² = 0.402^∗∗). Plotting linear intensity curves between reflectance at each waveband with infestation grade resulted in six sensitive bands that exhibited maximum correlation at different regions of the electromagnetic spectrum (376, 496, 691, 761, 1124 and 1457 nm). Regression analysis of several ratio indices formulated with two or more of these sensitive bands led to the identification of new leaf hopper indices (LHI) with a potential to detect leafhopper severity. These new indices along with 20 other stress related hyperspectral indices compiled from literature were further tested for their ability to detect LH severity. Two novel indices LHI 2 and LHI 4 proposed in this study showed significantly high coefficients of determination across locations (R² range 0.521 to 0.825^∗∗) and hence have the potential use for detection of leafhopper severity in cotton.  相似文献   

江苏沿岸四种贝类软体铅的含量特征及其风险评价   总被引：1，自引：0，他引：1  

戚原野  王李宝  万夕和  凌云  乔毅  王长海 《农业环境科学学报》2016,35(2):253-260

于2012年9月-2013年8月和2015年3月采集江苏沿岸文蛤、青蛤、杂色蛤、四角蛤蜊4种主要滩涂贝类样品,分析贝类软体铅(Pb)含量及其时空变化特征,采用点估计法和靶标危害系数法评价贝类软体Pb含量对人体暴露的风险。结果表明,采集的江苏沿岸4种主要滩涂贝类软体Pb含量范围为0.05~0.56 mg·kg~(-1),均值为0.23 mg·kg~(-1),所有贝类软体Pb含量均低于GB2762-2012(1.5 mg·kg~(-1))和NY5073-2006(1.0mg·kg~(-1))限值。茅家港站位4种贝类软体中Pb含量均在夏季达到最高值,分别为文蛤0.77 mg·kg~(-1)、青蛤0.12 mg·kg~(-1)、杂色蛤0.23 mg·kg~(-1)、四角蛤蜊0.61 mg·kg~(-1),文蛤和四角蛤蜊月度波动变化较为显著,青蛤和杂色蛤月度变化不显著;空间分布特征为贝类软体Pb含量最高值在S_3站位(陈家港,0.44 mg·kg~(-1)),次高值位于S4站位(滨海港,0.32 mg·kg~(-1)),最低值位于S11站位(洋口港,0.21 mg·kg~(-1)),其余站位差异较小,基本在0.21~0.30 mg·kg~(-1)之间。江苏沿岸居民在正常消费水平下,摄入地产经济贝类后,靶标危害系数(THQ)值均未超过1。风险评价结果显示,正常消费水平下,江苏沿岸4种滩涂贝类软体Pb暴露对目标人群的健康风险较低。  相似文献   

镉对姬松茸农艺性状及矿物质元素吸收的影响   总被引：2，自引：2，他引：0  

刘朋虎  李波  江枝和  雷锦桂  翁伯琦  黄在兴 《农业环境科学学报》2018,37(1):58-63

为了探讨不同浓度的镉对姬松茸子实体农艺性状、显微结构及部分矿物质元素吸收的影响,在培养料中添加不同浓度的外源镉进行出菇试验,研究了姬松茸子实体农艺性状、显微结构及部分矿物质元素含量的变化规律。结果表明:随着添加镉浓度的增加,柄量、柄直径、盖重、盖直径、朵重等农艺性状先增加后减小;子实体孢子和囊状体大小也是先增加后减小;子实体中锌含量逐渐降低,铜和铁的含量均先增加后降低,但是含量均高于对照,钙、镁的含量均先降低后增加。低浓度镉(2.5 mg·kg~(-1))促进农艺性状,而高浓度镉(2.5 mg·kg~(-1))抑制农艺性状,镉通过影响农艺性状影响产量;低浓度镉(2 mg·kg~(-1))能促进子实体孢子和囊状体的生长,而高浓度镉(2 mg·kg~(-1))对孢子和囊状体有毒害作用;镉对锌的吸收具有抑制作用,能促进铜和铁的吸收,低浓度镉抑制钙、镁的吸收,而高浓度镉促进钙、镁的吸收。  相似文献   

Assessment of forage mass from grassland swards by height measurement using an ultrasonic sensor     

Thomas Fricke  Felix RichterMichael Wachendorf 《Computers and Electronics in Agriculture》2011,79(2):142-152

The non-destructive assessment of forage mass in legume-grass mixtures as a tool for yield mapping in precision farming applications has been investigated in two field experiments. An ultrasonic sensor was used to determine sward heights. Forage mass-height relationships were evaluated by carrying out static measurements on binary legume-grass mixtures of white clover (Trifolium repens L.), red clover (Trifolium pratense L.), and lucerne (Medicago sativa L.) with perennial rye grass (Lolium perenne L.) across a wide range of sward heights (5.0-104.2 cm) and forage mass (0.15-11.25 t ha⁻¹). Mobile measurements, hereafter referred to as “on-the-go” were conducted by mounting the ultrasonic sensor in combination with a high-precision Differential Global Positioning System (DGPS) on a vehicle. Data were recorded along experimental plots consisting of perennial rye grass and grass-clover mixtures similar to the mixtures that were used for the static experiment. The static experiment revealed a relationship between ultrasonic sward height and forage mass explaining 74.8% of the variance with a standard error (SE) of 1.05 t ha⁻¹ in a common dataset. The type of legume species, weed proportion, and growth period had a significant impact on the above mentioned relationship. Legume-specific regression functions had higher R²-values of up to 0.855 (white clover mixture). Datasets including legume-specific mixtures and pure swards of both components reached comparable R² values between 0.799 and 0.818 but exhibited higher SE values. The abundance of weeds resulted in increased ultrasonic sward heights for the same levels of forage mass. On-the-go measurements across experimental field plots yielded a sward height range of 1.4-70.4 cm. Abrupt forage mass changes at the transition from treatment plots to cut interspaces resulted in a significant deviation from stubble height within a distance of 50 cm to plot borders. When legume-specific equations derived from static measurements were applied to sward heights, forage mass was overestimated by 21.4% on average. Mean residuals from predicted forage mass ranged between 0.893 (pure grass) and 1.672 (red clover mixture) and increased significantly if the point sampling distance along the track was increased to more than 0.82 m on average across all plots. The prediction accuracy of forage mass from ultrasonic height measurements is promising; however, further modifications to the technique are necessary. One such improvement can be the use of spectral reflectance signatures in combination with the ultrasonic sensor.  相似文献   

佳乐麝香与镉污染对土壤微生物和酶活性的影响   总被引：1，自引：1，他引：1  

赵芷玉  律泽  魏炜  韩晓墨 《农业环境科学学报》2021,40(8):1738-1745

为探究有机污染物与重金属复合污染对土壤中微生物的影响,以佳乐麝香(HHCB)和镉(Cd)为研究对象,研究HHCB与Cd污染对土壤中微生物数量和酶活性的影响。结果表明,HHCB单一及与Cd复合污染培养时间为1 d时,对细菌表现为抑制作用,培养时间为80 d时,表现为促进作用(100 mg·kg~(-1)HHCB的单一污染除外);对真菌生长均表现为促进作用,对放线菌生长均表现为抑制作用。细菌基因拷贝数随着HHCB浓度的升高而增加,而真菌基因拷贝数和放线菌基因拷贝数随着HHCB浓度的升高而降低。HHCB单一及与Cd复合污染对脲酶活性(1 d时)表现为抑制作用(800 mg·kg~(-1)HHCB的污染除外),对脲酶活性(80 d时)、酸性磷酸酶活性(1 d时)和蔗糖酶活性也均表现为抑制作用。培养时间为80 d时,400、800 mg·kg~(-1)HHCB的单一及与Cd复合污染对酸性磷酸酶活性表现为促进作用。  相似文献   

两种AMF对巨菌草根际土壤Cd生物可利用性以及Cd积累的影响   总被引：1，自引：0，他引：1  

姬朋朋  尹光彩  陈志良  周兵  林亲铁  刘千钧  刘德玲 《农业环境科学学报》2016,35(12):2306-2313

利用盆栽巨菌草(Pennisetum sp.)实验,研究了不同土壤镉(Cd)浓度(T0:空白;T1:5 mg·kg~(-1);T2:10 mg·kg~(-1);T3:15 mg·kg~(-1))条件下,接种两种丛枝菌根真菌(Arbuscular mycorrhizal fungi,AMF)[摩西斗管囊霉(Funneliformis mosseae,Fm)和根内根孢囊霉(Rhizophagus intraradices,Ri)]后土壤中Cd的生物有效性、巨菌草生物量、巨菌草Cd积累量等的变化。结果表明:与不施加菌剂(CK)相比,接种AMF显著降低了土壤中Cd的生物可利用性,在5、10、15 mg·kg~(-1)处理下,接种Fm和Ri后可交换态Cd分别降低了18.65%、20.51%、6.53%和12.54%、16.64%、6.66%;在10、15 mg·kg~(-1)处理下,接种Fm和Ri,植物地上部分生物量分别增加了20.98%、36.94%和36.54%、43.88%,地下部分生物量增加了14.31%、21.79%和25.78%、12.83%。接种AMF显著提高了巨菌草对Cd的吸收能力,其中在5 mg·kg~(-1)处理下接种Ri,巨菌草的重金属富集系数(BCF)最高,达到0.77,由于植物地上、地下部分Cd的含量均增加,巨菌草的Cd转移系数(TF)并没有显著变化。  相似文献   

硫对镉胁迫下小白菜镉富集、光合速率等生理特性的影响   总被引：2，自引：5，他引：2  

梁泰帅  刘昌欣  康靖全  敬志豪  吕金印 《农业环境科学学报》2015,34(8):1455-1463

以小白菜品种"七宝青"为材料,采用盆栽试验,研究外施硫(50 mg·kg^-1)对不同镉(Cd)处理水平(0、5、25、50、100 mg·kg^-1>)下小白菜生长、Cd吸收转运、光合特性及渗透调节物质含量的影响。结果显示,与单一Cd处理相比,5.25 mg·kg^-1 Cd处理水平下,外施硫显著促进了小白菜的生长,其株高分别增加了11.14%和21.16%,地上部干重分别增加了22.55%和19.90%,根部干重分别增加了27.83%和20.29%,叶绿素含量分别增加了11.81%和15.13%。外施硫降低了小白菜Cd的转运系数(TF)和地上部生物富集系数(BCF),提高了根部BCF。25 mg·kg^-1 Cd处理水平下,外施硫小白菜地上部Cd含量显著降低了24.82%,根部Cd含量显著增加了23.94%,TF值最小。5.25 mg·kg^-1 Cd处理水平下,外施硫能够明显缓解Cd胁迫对小白菜叶片光合作用的抑制,其净光合速率(Pn)分别增加了13.15%和15.22%,气孔导度(Gs)分别增加了13.81%和15.42%。25 mg·kg^-1 Cd处理水平下,外施硫小白菜叶片可溶性蛋白、可溶性糖、脯氨酸及抗坏血酸含量分别增加了20.82%、23.34%、26.79%和25.72%。研究结果表明,在25 mg·kg^-1 Cd处理水平下,外施50 mg·kg^-1硫显著减少了Cd从根部向地上部转移,降低小白菜地上部Cd含量,提高Cd胁迫下小白菜叶片的光合强度以及渗透调节物质的含量,对小白菜Cd毒害的缓解效应最为显著。  相似文献