Study on the optimal incident proton energy of ^(7)Li(p,n)^(7)Be neutron source for boron neutron capture therapy

Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.

Reviews on Agricultural Nonpoint Source Pollution Monitoring Techniques and Methods

Farmland nutrient loss has become one of the main reason causing agri- cultural nonpoint source pollution and water nitrogen, phosphorus eutrophication. Agricultural nonpoint source pollution monitoring techniques and methods are very important in agricultural nonpoint source pollution control. This paper reviews the various monitoring techniques of agricultural non-point source pollution, including runoff pollutant monitoring, leaching pollutant monitoring and on-line monitoring. The runoff pollutant monitoring methods are mainly included artificial simulation of rain- fall runoff method, flow meter method, weir method and volumetric method. The leaching pollutant monitoring methods are mainly included leaching plate method, leaching gutter method, leakage pooling method, pumping filter pipe method and simulating soil column method. Although online monitoring of farmland nutrient loss still exists some technical bottlenecks and economic limitations, it is the future di- rection of development.

Study of neutron production and moderation for sulfur neutron capture therapy

Neutron capture therapy with Sulfur-33, similar to boron neutron capture therapy with Boron-10, is effective in treating some types of tumors including ocular melanoma. The key point in sulfur neutron capture therapy is whether the neutron beam flux and the resonance capture cross section of ^(33)S(n;α)^(30) Si reaction at 13.5 keV can achieve the requirements of radiotherapy. In this research,the authors investigated the production of 13.5 keV neutron production and moderation based on an accelerator neutron source. A lithium glass detector was used to measure the neutron flux produced via near threshold^7 Li(p,n)~7 Be reaction using the time-of-flight method. Furthermore, the moderation effects of different kinds of materials were investigated using Monte Carlo simulation.

氮源和N/P对眼点拟微球藻的生长、总脂含量和脂肪酸组成的影响

报道了NaNO3,NH4Cl和NH4NO3 3种氮源及N/P对海洋微藻眼点拟微球藻(Nannochloropsisoculata)的生长、总脂含量和脂肪酸组成的影响。结果表明 ,N/P从10增加到90 ,对细胞生长的影响不大 ,总脂含量最终都稳定在干重的20 %左右。16∶0、16∶1n 9和20∶5n 3 (EPA)是脂肪酸的主要组分 ,三者之和占总脂肪酸的70 %～80 %。在培养基N/P>20时 ,20∶5n 3和PUFA占总脂肪酸的比例接近30 %和35 %。在3种氮源中 ,使用NaNO3 可获得更高的生长速率 ,并在相对较低的N/P下 (N/P=54)时获得约30 %的EPA ,故NaNO3 是眼点拟微球藻生长、合成和积累EPA的最佳氮源。将培养基中所有营养盐增加4倍 ,EPA含量可提高到35 % ,说明富含氮、磷的培养基可使细胞始终保持旺盛生长、富含EPA的状态 ,这也是该种微藻大规模培养中高产EPA的关键措施。

氮磷配施对坡地谷子吸N,P量及土壤养分流失的影响

氮磷配施对坡地谷子吸Ｎ，Ｐ量及土壤养分流失影响的研究表明：（１）Ｎ，Ｐ肥的不同配比均能增加谷子对Ｎ，Ｐ的吸收，增施Ｐ对Ｎ吸收的效果较高于增施Ｎ对Ｐ的吸收；（２）施Ｎ，Ｐ量的增加与泥沙中Ｎ，Ｐ富集率无相关关系；（３）作物生物量与土壤侵蚀量的相关系数为－０．９７２４；（４）增施Ｎ，Ｐ肥对土壤侵蚀和全量养分减少的程度远高于对径流量和速效Ｎ。

MgAPO-11分子筛的合成及Pt/MgAPO-11在正十二烷临氢异构化反应中的催化性能

采用常规水热合成法合成了系列MgAPO-11分子筛,考察了晶化时间、P/Al投料比和Mg源对MgAPO-11分子筛的物相、酸性以及Pt/MgAPO-11催化正十二烷临氢异构化反应性能的影响.分别用X射线衍射、X射线荧光光谱和NH3程序升温脱附测定了样品的晶相、Mg含量和酸性质.结果表明,合成条件影响着合成产物的晶相组成、Mg含量及酸性质,从而影响到Pt/MgAPO-11在正十二烷临氢异构化反应中的催化性能.反应结果显示,Pt/MgAPO-11催化剂的催化活性与MgAPO-11分子筛的强酸位数目密切相关.较短的晶化时间、合成凝胶的P/Al摩尔比为1·0以及使用Mg(NO3)2为Mg源有利于提高MgAPO-11的强酸位数目,从而提高Pt/MgAPO-11的催化活性.

以PHBV为固相碳源同时去除地下水中硝酸盐氮和对氯苯酚的试验研究

化肥和农药的施用导致中国的地下水中硝酸盐氮和农药污染同时存在,并成为威胁人体健康的重要因素之一。其中氯酚类物质是一类常见的农药,具有高毒性和难降解性。目前,关于固相反硝化用于硝酸盐氮和对氯苯酚同时去除的研究较少,并且对微生物群落结构演变情况的分析还鲜见报道。论文以聚羟基丁酸戊酸共聚酯(PHBV)为反硝化固体碳源,通过序批试验研究同步去除硝酸盐氮和对氯苯酚的效果,并探讨对氯苯酚的加入对反硝化速率的影响;利用末端限制性长度多态性分析(T-RFLP)技术,使用Alu I酶切总细菌16S r RNA,研究对氯苯酚的存在对微生物群落的影响。结果表明,(1)在50 mg·L-1的硝酸盐氮(NO3--N)的浓度水平下,对氯苯酚(4-CP)的加入前后,硝酸盐氮(NO3--N)的去除率为(97.5±1.2)%和(95.3±1.7)%,总体上使去除效果略有降低;在10 mg·L-1的质量浓度水平下,对氯苯酚24 h的平均去除率为45.4%,其去除85.5%是由于微生物的降解作用引起的。(2)从对氯苯酚的加入到第45天的时间内,反硝化速率表现为先下降后上升,说明对反硝化速率起到先抑制后促进的作用。(3)在对氯苯酚加入前后45 d内,系统微生物群落结构发生明显的变化,趋向于多样化和均匀化。

Zn、Cd在InSb中的扩散

研究了Ｚｎ、Ｃｄ源量对ＩｎＳｂ扩散结深的影响。在相同的扩散条件下，扩散源Ｚｎ、Ｃｄ的量少于一定值时，结深将随源量减少而急剧减少，此一定值随扩散温度的升高而增大，但当扩散源量大于该定值后，结深则与源量无关。

黄河源区高寒草原土壤对不同PGPR菌肥的响应

以黄河源区玛多县高寒草原为对象,野外原位施加不同类型根际促生菌肥(PGPR),研究高寒草原土壤w(速效氮)、w(速效磷)、w(速效钾)对不同类型菌肥的响应,草地土壤营养库活化技术,并筛选适宜菌肥.结果表明,黄河源区高寒草原土壤表层速效养分含量均随生长季呈先上升后下降的趋势.5种菌肥处理与无菌肥CK处理相比较,土壤w(铵态氮)提升12.97%~41.18%,巨大芽孢杆菌作用最为显著(41.18%).土壤w(硝态氮)提升12.72%~37.88%,胶质芽孢杆菌作用最为显著(37.88%).土壤w(速效磷)改变-4.48%~28.77%,胶质芽孢杆菌(26.11%)和巨大/胶质/甲基营养型芽孢杆菌(28.77%)作用最为显著.土壤w(速效钾)提升2.65%~10.42%,胶质芽孢杆菌(10.42%)作用相对显著.对于自然环境严酷的高寒草原,在水热条件相对较好的时间段,土壤施加胶质芽孢杆菌菌肥可有效提升高寒草原土速效养分.

Novel sediment source fingerprinting quantifying erosion-induced total nitrogen and total phosphorus outputs from an intensive agricultural catchment,North China

Intensive farming is a primary cause of increased sediment and associated nitrogen(N)and phosphorus(P)loads in surface water systems.Determining their contributing sources,pathways and loads present major challenges in the high-intensity agricultural catchments.Herein,we quantify the sediment sources and magnitude of sediment total N and total P from different sources using a novel application of compound-specific stable isotope(CSSI)and fallout radionuclides(FRNs)of^(137)cs and^(210)pbex in an intensive agricultural catchment in North China.Sediment sources from surface and sub-surface soils were estimated from FRNs fingerprint and accounted for 62±7%and 38±7%respectively,while surface soil from land uses that originated from hillslope were identified by CssI fingerprint.Using a novel application of FRNs and CSSI sediment fingerprinting techniques,the dominant sediment source was derived from maize farmland(44±0.1%),followed by channel bank(38±7%).The sedimentation rate(13.55±0.30 t ha^(-1)yr^(-1))was quantifed by the^(137)cs cores(0-60 cm)at the outlet of this catchment.The total N and total P in sediment were both mostly derived from maize farmland and least from channel banks.The channel banks are significant sediment sources but contribute little to the input of sediment N and P for eutrophication.It implies that chemically-applied farmlands are the main hotspots for catchment erosion control and pollution prevention.The novel application of FRNs and CSSI techniques cost-effectively quantified sediment N and P loads from different sources with a single visit to the catchment,enabling rapid assessment for optimizing soil conservation strategies and land management practices.

Effects of Soluble Silicate and Nanosilica Application on Rice Nutrition in an Oxisol

Silicon （Si） has been supplied to plants via application of calcium silicate to soil; however, high doses of calcium silicate are required because of its low solubility. Nanoparticles can reduce Si doses and be applied to seeding furrows. This study investigated the effects of liquid Si sources, i.e., highly soluble silicate （115.2 g L^-1 Si and 60.5 g L^-1 Na20） and nanosilica （〈 200 nm）, on Si uptake by rice plants, plant lignification, plant C：N：P stoichiometry, plant physiology, and grain yield using an Oxisol under greanhouse condistions. The treatments included the application of nanosilica and soluble silicate to seeding furrows at Si doses of 0, 605, 1210, and 2 420 g ha^-1. Plant uptake and treatment effects were evaluated by measuring C and lignin contents, Si, N, and P accumulation, physiological characteristics, and grain yield of rice. The deposition of silica bodies and amorphous silica in the flag leaves was analyzed using scanning electron microscopy. Application of liquid Si increased Si accumulation in rice by 47.3% in relation to the control （0 g ha^-1 Si）, regardless of the Si sources used. Nanosilica application increased leaf lignin content by 112.7% when compared to that in the control. Silicon moderately affected the net C assimilation （increased by 1.83%） and transpiration rates （increased by 48.3%）; however, Si influenced neither plant growth nor grain yield of rice. These results are explained by the lack of biotic or abiotic stress in rice plants during the experiment. To the best of our knowledge, in Brazilian agriculture, this is the first report on the use of nanosilica as a Si fertilizer and its effect on plant nutrition. This study provides evidence that rice plants absorb and accumulate nanoparticles; however, further studies are required to investigate the use of nanoparticles in other plant species.

Systematic study of the(n,2n)reaction cross section for^(121)Sb and^(123)Sb isotopes

The cross sections of the^(121)Sb(n,2n)^(120)Sb^(m) and ^(123)Sb(n,2n)^(122)Sb reactions were measured at 12.50,15.79 and 18.87 MeV neutron energies relative to the standard ^(27)Al(n,α)^(24)Na monitor reaction using neutron activation and offline γ-ray spectrometry.Irradiation of the samples was performed at the BARC-TIFR Pelletron Linac Facility,Mumbai,India.The quasi-monoenergetic neutrons were generated via the ^(7)Li(p,n)reaction.Statistical model calculations were performed by nuclear reaction codes TALYS(ver.1.9)and EMPIRE(ver.3.2.2)using various input parameters and nuclear level density models.The cross sections of the ground and the isomeric state as well as the isomeric cross section ratio were studied theoretically from reaction threshold to 26 MeV energies.The effect of pre-equilibrium emission is also discussed in detail using different theoretical models.The present measured cross sections were discussed and compared with the reported experimental data and evaluation data of the JEFF-3.3,ENDF/B-VIII.0,JENDL/AD-2017 and TENDL-2019 libraries.A detailed analysis of the uncertainties in the measured cross section data was performed using the covariance analysis method.Furthermore,a systematic study of the(n,2n)reaction cross section for^(121)Sb and^(123)Sb isotopes was also performed within 14-15 MeV neutron energies using various systematic formulae.This work helps to overcome discrepancies in Sb data and illustrate a better understanding of pre-equilibrium emission in the(n,2n)reaction channel.

旱地冬小麦氮磷自然供给能力及其吸收氮磷来源的长期定位试验

利用在黄土旱塬上布置的 13年小麦连作肥料定位试验资料 ,研究了旱地冬小麦氮磷的自然供给能力和吸收来源于肥料和土壤的氮磷相对比例。结果表明 ,旱地冬小麦氮素的自然供给能力为 2 6 6 8～ 2 7 4 9kg/hm2 ,平均为 2 7 2kg/hm2 ;磷素自然供给能力为 5 2 1～ 8 4 9kg/hm2 ,平均为 7 31kg/hm2 。小麦吸收氮素有 51 9%～ 76 8%来自氮肥 ,平均为 6 6 6 % ;而来自土壤为2 3 2 %～ 4 8 1% ,平均 33 4 %。小麦吸收磷素来源于肥料的为 13 6 %～ 4 7 8% ,平均为2 8 7% ;来源于土壤为 52 2 %～ 86 4 % ,平均为 71 3%。同一肥底基础上 ,随肥料用量的增加 ,小麦吸收氮或磷素来源于肥料的比例也增大 ,而来源于土壤的比例逐渐减少。本试验条件下 ,氮肥利用率变幅为 32 6 %～ 6 6 0 % ,平均为 51 1% ;磷肥利用率变幅为 1 72 %～ 14 0 2 % ,平均为 7 0 %

宁夏引黄灌区春小麦不同生育期吸收氮、磷、钾养分的特点

选择宁夏引黄灌区中等肥力灌淤土，设置施肥与不施肥处理，在相距约5km的3个试验点进行了肥料田间试验，研究春小麦不同生育期氮、磷、钾养分的吸收特点。结果表明，在供试土壤条件下，施肥可明显提高小麦产量、干物质累积茸、体内氮、磷、钾含量及其累积量。施肥或不施肥，小麦地上部干物质的累积量随生育期呈典型“S型”曲线增长，其中拔节期和灌浆期出现两个高峰期，各占总累积量的30％左右。植株氮、磷、钾含量随生育期呈曲线下降趋势，特别是从拔节到灌浆中期下降幅度较大；而在分蘖期以前和灌浆中期以后变化幅度较小。植株氮、磷、钾累积吸收量随生育期的延长和施肥水平的提高而增加，但各生育期相对累积吸收比例，施肥与否差异不大。苗期氮、磷、钾的吸收量约占总吸收越的4％～5％，分蘖期占20％～23％，拔节期分别占30％、41％、34％，抽穗期分别占14％、12％、10％，灌浆期分别占29％、20％、26％，成熟期占1％～3％，其中拔节期是养分吸收的高峰时期。不论施肥与否，地上部氮、磷、钾累积吸收量与其干物质累积量之间均是极显著正相关，而与植株氨、磷、钾含量之间呈极显著负相关。

旱地春谷子不同生育期吸收氮、磷、钾养分的特点

研究了在施肥与不施肥处理情况下,半湿润偏旱区春谷子不同生育期氮、磷、钾养分的吸收特点。结果表明：在供试土壤条件下,施肥可明显提高春谷子产量、干物质累积量、体内氮、磷、钾含量及其累积量;施肥或不施肥,春谷子地上部干物质的累积量随生育期呈典型“S型”曲线增长,其中抽穗灌浆期为累积高峰期,占总累积量的50%左右;植株氮含量随生育期呈曲线下降趋势,整个生育期植株含磷量呈“W型”变化,植株含钾量呈单峰曲线变化,峰值出现在拔节期;植株氮、磷、钾累积吸收量随生育期的延长和施肥水平的提高而增加,但各生育期相对累积吸收比例,施肥与否差异不大;苗期氮、磷、钾的吸收量约占总吸收量的1%～3%,拔节期约占总吸收量的30%、20%、37%,是钾素吸收的高峰期,孕穗期约占22%、21%、34%,抽穗灌浆期约占43%、53%、23%,是氮、磷吸收的高峰期,籽粒形成期约占3%～5%;不论施肥与否,地上部氮、磷、钾累积吸收量与干物质累积量之间均呈极显著正相关,而与植株氮、钾含量之间呈极显著负相关。

东北地区农田土壤氮、磷平衡及其对面源污染的贡献分析

采用农田生态系统氮、磷平衡计算方法,对东北地区土壤氮、磷养分平衡状况及其对面源污染的贡献进行了研究。结果表明,东北三省农田化肥用量随时间的增加而增大,但不同种植区间化肥投入差异较大;氮、磷肥用量是造成农田土壤氮、磷平衡空间差异的直接因素,两者呈极显著相关关系;由于化肥投入量的增加,东北三省农田土壤氮、磷平衡均由建国初期的亏缺转为盈余,赢余量呈现随时间增加而增大的趋势,但区域间差异较大。与80年代相比,2002年由东北三省农田土壤总氮平衡和总磷平衡进入水体环境的氮、磷负荷均有所增加,各省农田进入水体环境氮、磷负荷的升高幅度分别为:辽宁,氮负荷29%,磷负荷3%;吉林,氮负荷93%,磷负荷229%;黑龙江,氮负荷39%,磷负荷125%。果树蔬菜种植面积比例的增加是造成农田土壤氮素盈余增加的原因之一,两者呈极显著相关关系。随着辽河流域果树、蔬菜种植面积的逐年增加,果树和蔬菜农田土壤养分过度累积对辽河水体面源污染的贡献不容忽视。

不同产地山药氮磷钾吸收规律研究

选同一山药品种在不同产地栽培,研究不同产地对山药N,P,K的吸收特点,分析不同生育时期的植株不同器官中N,P,K含量.结果表明,不同产地山药中N,P含量均以根茎膨大盛期前后最高;山药生长期内对N的吸收量最高,K次之,P最低;不同产地山药根茎对N,P,K的总吸收量最高,其次为叶、茎.

福州市郊菜地氮磷面源污染现状分析与评价

通过对福州市郊14片蔬菜基地的120个蔬菜样品、16个田面水样和11个地下水样的检测,并引用相关评价标准,分析了福州市郊菜地氮磷面源污染现状。结果表明:(1)处于严重污染(NO3-≥3100mg·kg-1)的蔬菜样品占检测总数的13.33%,处于重度污染(NO3-≥1440mg·kg-1)以上的蔬菜样品占检测总数的32.5%,处于中度污染(NO3-≥785mg·kg-1)以上的蔬菜样品占检测总数的50.83%。(2)氨氮含量超过地表水Ⅲ类(1mg·L-1)和Ⅴ类(2mg·L-1)水质标准的菜地田面水样数量分别占调查总量的62.5%和56.25%;硝态氮含量超过国家集中式生活饮用水地表水标准(10mg·L-1)的菜地田面水样数量占调查总量的12.5%;总氮平均含量和最高含量分别为10.99和33.80mg·L-1,分别是地表水Ⅴ类水质氮标准(2mg·L-1)的5.5和16.9倍;总磷平均含量和最高含量分别为4.75和12.75mg·L-1,分别是地表水Ⅴ类水质磷标准(0.4mg·L-1)的11.9和31.9倍。(3)氨氮含量超过Ⅴ类水质标准(0.5mg·L-1)的地下水样数量占调查总量的18.18%;硝态氮含量处于超标级别(≥10mg·L-1)以上的地下水样数量占调查总数的54.55%,处于严重超标级别(≥20mg·L-1)以上的地下水样数量占调查总量的27.27%;总氮含量全部超过Ⅴ类水质标准(2mg·L-1,GB3838—2002),超标率为100%;总磷含量超过Ⅴ类水质标准(0.4mg·L-1,GB3838—2002)的占调查总量的81.82%。

碳源对缺氧/厌氧/好氧工艺脱氮除磷效果的影响

通过投加有机碳源改变进水的碳氮比,考察了不同碳氮比条件下缺氧/厌氧/好氧工艺的脱氮除磷效果。结果表明:在污泥回流比为120%的条件下,当C/N值为7、C/P值为75时,缺氧/厌氧/好氧工艺对污水的脱氮除磷效果最佳,对TP、NH4+-N和TN的去除率分别可达95%以上、98%和67%。

新型后置反硝化工艺处理低C/N(C/P)比污水脱氮除磷性能研究

从内碳源有效利用角度出发,开发了新型连续流后置反硝化AOA工艺,将厌氧段混合液按一定比例分流至缺氧段,从而强化缺氧段反硝化除磷作用.进水NH+4-N和PO3-4-P浓度保持在(38.31±2.03)mg·L-1和(5.74±0.13)mg·L-1,在不同运行阶段进水COD分别控制在300mg·L-1和250 mg·L-1,考察了AOA工艺处理低C/N(C/P)比污水过程影响因素.当进水C/N比和C/P比分别为7.41±0.26和52.36±1.25时,通过将SRT由10 d延长到16 d,系统TN和PO3-4-P去除率分别稳定在65.86%±2.06%和90.00%±3.97%;当进水C/N比、C/P比降至6.14±0.32和43.40±1.37时,在SRT为16 d条件下,将A/O/A体积比由1/3/1调整为1/2/2,TN和PO3-4-P去除率分别升至69.76%±3.36%和98.73%±1.82%.结果表明,采用控制SRT、调整好氧/缺氧HRT等策略,可保证处理低C/N(C/P)比污水AOA工艺高效稳定运行.