浙江柑橘果品农药残留状况分析

为摸清浙江省柑橘生产过程中农药使用情况及果品质量安全状况,2018—2020年采用超高效液相色谱-串联质谱法和气相色谱-串联质谱法对浙江省台州、宁波、衢州、温州、金华等柑橘主产区265个样品进行136种农药残留的检测。结果表明,2018—2020年共检测出农药38种,包括18种杀虫剂、11种杀菌剂、6种杀螨剂及3种植物生长调节剂。3 a样品的农药残留检出率为95.85%,逐年依次为87.72%、99.02%和97.17%,农药最高检出率为杀虫剂>杀螨剂>杀菌剂;总样本超标率为3.02%,逐年依次为1.75%、5.88%、0.94%,禁限用农药检出结果逐年明显趋好;柚类农药残留检出率、超标率均小于橘、柑类。因此,样品中农药使用情况较为普遍,近2 a使用农药种类存在增加趋势,但禁限用农药控制较好,浙江柑橘果品质量安全性整体较好。     

苹果、梨、桃和枣4种水果5种重金属含量检测与分析

以GB 2762—2012《食品安全国家标准食品中污染物限量》为依据,采用原子吸收光谱法、原子荧光光度法等检测方法,对山西省中部、南部水果主产区的苹果、梨、桃和枣共70个样品进行了铅、镉、砷、铬和镍5种重金属元素的检测和分析。结果表明,5种重金属铅、镉、砷、铬和镍在苹果中的检出率分别为10%,100%,23.3%,100%和60%,在梨中的检出率分别为20%,0,0,100%和50%,在桃中的检出率分别为20%,100%,30%,100%和90%,在枣中的检出率分别为10%,25%,0,100%和75%;其中,4种水果铅和镉的超标率均为0,5种重金属元素含量由少到多依次为镉砷铅镍铬。套袋特别是套塑料袋能减少梨重金属的含量;4种水果对重金属的吸附能力也存在一定的差异,梨对重金属的吸附性能最低,桃对重金属的吸附性能最高;靠近公路的苹果样品中重金属的含量较远离公路的样品中重金属含量高,其中对铅含量的影响最大。     

山西省番茄中农药与重金属污染特征及膳食摄入风险评估

为了明确番茄中农药与重金属(铅和镉)污染物残留特征及由此产生的居民膳食摄入风险,在山西省番茄主产区随机抽取番茄样品60份,采用气相色谱串联质谱法(GC-MS/MS)和超高效液相色谱-串联质谱法(UPLC-MS/MS)测定70种农药残留,采用石墨炉原子吸收法测定铅、镉含量,根据检测结果对2种污染物的残留特征进行分析,同时采用英国食品标准局(FSA)风险排序体系和食品安全指数(IFS)法对番茄中检出的农药和重金属进行安全性评价。结果显示,番茄样品的农药检出率为73.3%,检出农药19种,其中杀菌剂占63.2%,杀虫剂占31.6%,杀菌剂以腐霉利为主,检出率达40.0%,杀虫剂以啶虫脒为主,检出率为8.3%;检出的农药中包括1种禁限用农药、2种未在番茄生产中登记的农药和3种未制定限量标准的农药;检出3种及以上农药残留样品9个,占检出样品的20.5%;番茄中农药残留种类和数量存在地区差异。农药风险排序得出,19种农药在高、中、低风险水平的比例分别为5.3%、15.8%和78.9%,其中氧乐果是风险较高的农药品种。从农药残留安全指数评价结果来看,19种农药的IFS均1,摄入风险在可接受范围。番茄样品中重金属铅和镉的检出率分别为53.3%和100.0%,其平均值均低于国家食品污染物限量标准,安全指数评价结果也进一步证明了番茄中铅和镉残留量的总体水平处于安全状态。总之,山西省番茄农药残留和重金属风险均在可接受范围,番茄质量安全情况良好。     

2011—2013年西安市蔬菜水果农药残留状况分析

连续三年随机对西安市大型超市、批发市场和基地中的五大类蔬菜及水果进行了随机抽样检测,共抽取样品1 808个,采用气相色谱、液相色谱、气质联用色谱定性定量检测。结果表明:1不同年份不同季节之间农药残留种类检出情况没有明显区别,每个样品都有农药残留检出,且以叶类蔬菜中农药残留种类检出最多。2连续3 a,不同品种的蔬菜水果高残留农药种类都集中在有机氯农药百菌清、三唑酮、腐霉利。3连续三年以叶类蔬菜禁限用农药检出率最高,禁限用农药中以氧化乐果检出率相对较高,对硫磷检出率最低。     

福建省市售茉莉花茶中65种农药残留检测与分析

为了解福建地区来自广西横州市的市售茉莉花茶中农药残留情况,保障福建市场茉莉花产品质量安全提供科学依据,在市场上随机采购2022年1—6月的230份茉莉花茶样品,采用气相色谱-质谱法和液相色谱-质谱法对样品进行65种农药的残留检测,依据GB 2763—2021标准判断,结合检测结果分析不同种类农药的残留情况。结果表明：230份茉莉花茶中,93份样品有农药残留检出,检出率为40.42%,检出21种农药单品。三大类农药检测项目种类最多的为杀虫杀螨类,其次为杀菌剂类、除草剂类,21种农药残留检出率前五的主要为联苯菊酯（27.83%）、啶虫脒（16.09%）、虫螨腈（12.61%）、吡虫啉（11.30%）、氯氰菊酯（9.13%）。样品中农残检出均未超标,说明福建省市售茉莉花茶农药残留总体安全,在茶叶生产中以联苯菊酯和啶虫脒使用居多,但农药残留的检出量也远低于GB 2763—2021国家标准限定值。     

市售园林水果农药残留现状及清洗方法研究

选取日常消费量大的市售园林水果——苹果、梨、桃、葡萄、鲜枣作为研究对象,对其农药残留情况进行分析检测,并对超标水果采用不同清洗方法进行处理,比较不同清洗方法对残留农药的去除效果。结果表明,市售园林水果农药残留仍较为普遍,现状不容乐观,尤以葡萄的农药残留超标现象最为严重;采用的不同农药残留清洗方法,均能不同程度降低水果的农药残留量,以50℃温水浸泡10 min后在流动自来水下冲洗20s对农药残留的去除效果最好。     

昌平苹果中农药残留污染情况调查与分析

为摸清昌平苹果生产中农药使用及残留污染现状,笔者对昌平区27个种植基地、55个农户进行农药使用情况调查,并抽取103个样品进行农药残留定量检测。调查显示,昌平地区使用的农药采购多来自昌平本地,农药的购入途径以植保站和正规农资公司为主,种植过程中都会使用杀虫剂、杀菌剂,种植户基本掌握农药安全间隔期,但是存在随意使用农药现象。结合调查问卷,对103个苹果样品中的62种农药残留进行检测分析,其中59种农药未检出、3种农药检出;本次检测未发现超标样品和使用禁用农药样品;根据超标、检出、销量进行62种农药风险等级划分,无高风险农药,将氯氰菊酯划分为中风险农药。通过分析发现,昌平苹果存在随意用药、农药检测项目不全面等问题。总体来看,昌平苹果农药残留水平较低,农产品质量相对安全,今后还应该继续强化监测力度,加强对农药使用的科学管理。     

2017-2019年成都地区水果农药残留状况

【目的】为保障消费者食用水果质量安全,并为成都市行政主管部门在农药质量管理、标准化种植管理、禁限用农药查处及制定水果抽检频率提供技术支撑,切实保障消费者食用水果质量安全。【方法】参照GB/T 23200.19—2016、GB/T 5009.144—2003、SN/T 3643—2013、NY/T 761—2008等方法对2017—2019 年从成都市区域内水果种植基地采集的738个水果样品进行66种农药的残留检测。检测结果依据GB 2763—2016进行判定。【结果】738个样品中,有453个水果样品检出共计40种农药残留,农药检出率达61.39%。浆果类水果占检出样品的44.37%,而核果类水果检出5个样品不合格,占总不合格率的41.67%。【结论】成都地区基地水果合格率98.37%,总体良好,但仍需增大农药质量监督范围和数量、引进CAQS-GAP等标准化种植管理技术体系及严格按照抽样标准对各水果生产主体进行随机抽查样品的入市前端管理。     

中国苹果农药残留研究初报

为评估中国苹果农药残留状况,2003—2004年从主产区采集样品153个(渤海湾地区65个,西北黄土高原地区88个),检测29种农药的残留量。96.08%的样品检出农药残留,13.07%的样品农药残留超标。14种农药检测到了残留,但只有多菌灵、敌敌畏、对硫磷和倍硫磷等4种农药出现残留超标,超标率分别为6.54%、4.58%、2.61%和0.65%。分析了残留超标原因,提出了降低农药残留对策。     

温州市田间杨梅农药残留现状的调查与分析

为摸清温州市田间杨梅农药残留现状,为杨梅病虫害防控和上市产品安全提供依据。2016年和2017年的6-7月份,随机采集温州市146个杨梅生产主体的229份成熟期杨梅样品,采用国家标准检测方法中的气相色谱法和液相色谱-串联质谱法对46种农药进行残留检测,并以GB2763-2016《食品安全国家标准食品中农药最大残留限量》作判定依据。结果:检出20种农药有不同程度的残留,其中5种农药样品残留检出率≥10%,并以多菌灵检出率最高,为24.02%;3个样品有甲维盐或百菌清农药残留超标,超标率为1.31%。共检出带有农药残留样品118份,检出率为51.53%;检出有2种以上农药同时残留的样品计68个,最多检出1个样品中有6种农药同时残留。表明:成熟期杨梅的农药残留合格率接近99%,但因其为鲜食裸水果,尚存一定的潜在风险。应当加强对杨梅生产过程,特别是成熟期间农药使用和产品安全监管,严格执行用药安全制度及休药期规定,从源头上彻底消除上市杨梅的安全隐患。     

Alternatives, traditions, and diversity in agriculture

This review essay examines several recentbooks about agriculture, including two books on thelinks between cultural and biological diversity intraditional agriculture, two books on the US farmcrisis, and a collected volume examining globalaspects of agricultural restructuring andsustainability. Finally, a history of ``alternative'agriculture provides a framework for thinking aboutthe ways the different cases shed light on the complexrelations between tradition and innovation inagriculture. A historical perspective highlights theextent to which ``alternative' is a relative term. Themonocrop, ``factory' mode that dominate US agriculturetoday certainly differs from what has characterizedfarming for most of history and in most of the world.Small-scale, more or less organic, diversified farms,which appear so ``alternative' in the present context,have until lately counted as the norm, here andelsewhere. These books also highlight both the dangersof the currently dominant industrial agriculture andthe potential for genuine alternatives.     

Structure, dynamics, and reactivity in hemoglobin

The static structure of hemoglobin and its functional properties are very well characterized. It is still not known how energy is stored and used within the structure of the protein to promote function and functional diversity. An essential part of this question is understanding the mechanism through which the overall protein structure (quaternary structure) couples to the local environment about the oxygen binding sites. Time-resolved resonance Raman spectroscopy has been used to probe the vibrational degrees of the freedom of the binding site as a function of protein structure. Comparison of the spectra from both equilibrium and transient forms of deoxy hemoglobin from a variety of mammalian, reptilian, and fish hemoglobins reveals that for each quaternary structure there exist two tertiary states stabilized by the presence or absence of an iron-bound ligand. Pulse-probe Raman experiments show that for photodissociated, ligated hemoglobins the local tertiary structure relaxes at a solution-dependent rate extending from tens of nanoseconds to microseconds. In this local environment, the linkage between the iron and the proximal histidine proves to be the single observed structural feature that responds in a systematic and substantial manner to structural changes in the protein. The additional finding of a correlation between the frequency of the iron-proximal histidine stretching motion (nu Fe-His) and various parameters of ligand reactivity, including geminate recombination, implicates the associated localized structural element in the mechanism of protein control of ligand binding. On the basis of these and related finds, a model is presented to account for both coarse and fine control of ligand binding by the protein structure.     

Gallium, germanium, indium, and iridium in lunar samples

Neutron activation analyses of gallium, germanium, indium, and iridium in eight lunar samples and in meteorites and rocks (including four calciulnrich achondrites and five terrestrial basalts) with similar bulk compositions are reported. Lunar gallium concentrations are remarkably constant at about 5 parts per million, three times higher and four times lower than those in eucritic (calcium-rich) achondrites and terrestrial basalts, respectively. Lunar germanium concentrations range from 相似文献   

Potassium, rubidium, strontium, barium, and rare-Earth concentrations in lunar rocks and separated phases

Concentrations of potassium, rubidium, strontium, barium, and rareearth elements have been determined by mass spectrometric isotope dilution for eight Apollo 11 lunar samples and for some separated phases. Potassiumn and ritbidium are at chondritic levels, strontium at 15 times, and barium and rare earths at 30 to 100 times chondritic levels. There are trace element similarities between the lunar samples and basaltic achondrites, terrestrial dredge basalts and the bulk earth. The trace element data appear to be consistent with these lunar samples being the result of limited partial fusion of some material similar to the brecciated eucrite meteorites.     

重金属Pb、Cr、Cd对烟草生长的影响及其分布规律

[目的]研究重金属Pb、Cr、Cd对烟草的生理作用及其在烟草中的吸收累积规律.[方法]采用盆栽试验方法,测定烟草根、茎、叶等器官中Pb、Cr、Cd含量,分析不同重金属污染程度下烟草的株高及叶片干物质重的变化.[结果]重金属处理的土壤中烟草的株高都显著低于对照,呈现抑制作用,添加外源Pb和Cr处理下,烟草叶片干重随添加浓度的升高而降低,Cd处理则呈现出先升高后降低的趋势.Pb、Cr、Cd重金属在烟草器官中的含量均为根>茎>叶,根系中Pb、Cr、Cd的浓度与添加浓度具有较好的相关性,而叶片中只有Cd含量与添加浓度具有较好的相关性.[结论]烟草植株中的重金属主要来源于土壤,烟草对重金属的传输过程具有一定的滞阻作用.     

DNA conformation, dynamics, and interactions in solution

The conformation and dynamics of the d(CGCGAATTCGCG) duplex, its analogs containing mismatched base pairs and helix interruptions, and its complexes with actinomycin and Netropsin, bound separately and simultaneously, have been investigated by nuclear magnetic resonance spectroscopy in aqueous solution. Structural information has been deduced from chemical shift and nuclear Overhauser effect parameters, while the kinetics have been probed from line width and saturation recovery experiments on proton and phosphorus markers at the individual base pair level. These studies lead to an improved understanding of the role of nucleic acid sequence on the structure, flexibility, and conformational interconversions in the duplex state. The nuclear magnetic resonance measurements readily identify helix modification and antibiotic binding sites on the nucleic acid and estimate the extent to which the observed conformational and dynamic perturbations are transmitted to adjacent base pair regions.