公路附近茶园土壤中铅和镉的化学形态

研究了浙江省各地采集的公路附近茶园土壤中铅和镉的化学形态。结果表明,表层土壤中铅和镉总量和各形态组分的含量因采样地和土壤性质的差异可有很大的差别。土壤剖面中铅和镉从下至上有规律地显著增加,表明表土中积累的铅和镉的主要为外源铅镉。土壤中残余态、氧化物结合态、有机质结合态铅和镉的含量主要与土壤中铅、镉积累有关;而生物有效性较高的交换态和水可溶态铅、镉受土壤pH有很大的影响。因此,长期植茶导致的土壤酸化可能是土壤中铅和镉活度增加的主要原因,并可增加茶树对铅和镉的吸收。     

闽北地区不同类型茶园土壤硒赋存形态特征及影响因素分析

为探讨闽北典型茶园土壤中硒形态特征,采集了闽北地区4个主要土壤类型(黄壤、红壤、潮砂土、紫色土)的35份茶园表层土壤(0~20 cm),分析土壤中硒含量、赋存形态及影响因素。结果表明:闽北地区35份茶园土壤全硒含量为0.22~1.07 mg·kg^(-1),均值为0.59 mg·kg^(-1),达到富硒土壤标准(>0.4 mg·kg^(-1))比例茶园占82.86%;土壤硒活化率均值为8.34%,土壤中硒的有效度较低。不同土壤类型中以黄壤茶园土壤全硒及各形态硒含量最高,潮砂土含量硒含量最低,但其茶园土壤硒活化率最高。茶园土壤硒形态分布规律表现为有机结合态>残渣态>可交换态及碳酸盐结合态>铁锰氧化物结合态>可溶态,土壤硒的生物有效性较低。相关分析表明,茶园土壤硒形态总体受土壤有机质、氮素形态及pH的影响,土壤有效磷与土壤全硒、有机结合态和残渣态硒之间呈显著或极显著正相关,土壤铁锰氧化物结合态硒与土壤理化性质之间相关性均不显著。总体而言,该区域茶园富硒土壤为发展天然富硒茶提供了物源保证,但硒生物有效性不高,如何提高硒生物有效性还有待进一步研究。     

酸化和有机质积累对茶园土壤铅生物有效性的影响

本文用土培试验研究了质地差异较大的二种茶园土壤酸化和有机质积累引起的水溶性铅、有效态铅和铅的化学形态的变化。结果表明,土壤酸化可显著地促进其它形态的铅向可交换态铅转化,增加土壤铅的水溶性和生物有效性。当土壤pH较高(pH>4)时,增加土壤有机质可促进土壤铅的活化,但在pH较低(pH<4)的土壤中,有机质积累降低了土壤中的有效态铅。酸化和有机质积累对铅的生物有效性影响在砂质土壤比粘质土壤更为明显。     

茶树及成品茶叶中铅的研究进展

本文针对茶叶中铅含量超标问题,对茶园土壤、茶树对铅的吸收及茶叶中铅含量的影响因素等方面进行了分析.提出正常饮用茶叶不会导致铅中毒;但茶叶深加工产品的使用安全性尚需进行科研证实.     

蔬菜产地酸性土壤中Pb、Cd、Cr形态分析研究

在海南岛中部市县采集了8种蔬菜及其产地酸性土壤样品,采用连续浸提法分析土壤样品中Pb、Cd、Cr元素的水溶态、离子交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态、残渣态以及全量态等的含量,同时测定了对应蔬菜样本中Pb、Cd、Cr的含量,探讨酸性土壤Pb、Cd、Cr元素的形态分析方法、分布规律及对蔬菜含量的影响。结果表明:Pb、Cd、Cr元素形态分析结果的符合率分别为107%、94%和81%。3元素各形态含量占全量的百分比大小顺序分别为:Pb元素的残渣态>铁锰氧化物结合态>有机物结合态>碳酸盐结合态>离子交换态>水溶态;Cd元素的碳酸盐结合态>残渣态>离子交换态>水溶态>有机物结合态>铁锰氧化物结合态;Cr元素的残渣态>有机物结合态>水溶态>铁锰氧化物结合态>离子交换态>碳酸盐结合态。土壤中有70%以上的Pb、Cr离子处于被固定的状态(即残渣态),不容易被植物吸收,而有70%以上的Cd离子处于活化状态,容易被植物吸收,说明Cd元素是蔬菜无公害安全质量生产中重要的风险控制指标。     

天然矿物对茶园土壤中铅的固定作用

茶园土壤中铅的生物有效性直接影响茶叶中铅的积累。为了解外加天然矿物对土壤中铅的固定作用,本文比较研究了4种矿物(高岭石、膨润土、沸石和磷灰石)在不同加入量和不同磨细程度条件下对土壤交换态铅和水溶性铅的影响。结果表明,加入矿物改良剂对土壤有效态铅(交换态铅和水溶性铅)有明显的降低作用,其效果与矿物类型、矿物加入量及加入矿物的磨细程度等有关。矿物对土壤有效铅的降低作用是:磷灰石>沸石>膨润土>高岭石。过100目处理矿物对土壤中铅的固定效果高于过18目处理的矿物。加入矿物对土壤水溶性铅的降低作用明显高于对交换态Pb的作用。结果认为,用天然矿物来改良铅污染茶园土壤、降低土壤有效铅是可行的。当土壤铅污染水平较低时,加入矿物量为20g/kg已能达到改良效果。     

3种改良剂对强酸性高硒茶园土壤硒有效性调控效果与机理

通过室内模拟试验和田间试验相结合的方法,探究3种改良剂(秸秆生物质炭、钙镁磷肥和蚯蚓液态肥)及其不同配施方式对强酸性高硒茶园土壤硒有效性的调控效果与机理。模拟施肥试验结果表明,不同处理均可显著提高土壤pH值和降低交换态铝含量,同时显著提高有效硒含量。形态分析结果表明,硒由有机结合态向可溶态转化,从而增加土壤有效硒含量;铝由交换态向有机配位态转化,土壤潜性酸度降低,进一步增强硒的有效性。田间试验结果表明,秸秆生物质炭和钙镁磷肥的不同配施方式均能有效抑制茶园土壤进一步酸化,显著提高土壤硒有效性及茶叶硒含量,其中同时施用秸秆生物质炭和钙镁磷肥再错时配施蚯蚓液态肥的效果最佳。本研究可为酸性富硒土壤地区开发富硒茶提供依据。     

土壤对茶叶铅污染的影响及植物修复研究

通过对茶园土壤和茶叶含铅量的分析,以及盆栽植物铅富集量的测定,结果表明:成品茶中铅含量超标主要原因之一是茶园土壤含铅量过高引起的,它们成高度正相关,相关系数r=0.8583。8种植物对铅的富集和忍受力差异很大,富集量从高到低的次序是青笋、甘蓝、黑麦草、菠菜、大白菜。耐性表现在含高浓度铅的土壤中植物生长量的大小,其排列顺序是:菠菜、萝卜、大白菜、甘蓝、青笋、黑麦草。     

茶叶中铅含量现状及研究动态

通过对茶叶中铅含量及变化趋势的论述揭示了重金属铅在茶叶中的污染状况。茶叶中的铅主要来源于大气中的气铅、尘铅、土壤中有效态铅及茶叶加工机械合金中的铅，其污染程度受环境因素和加工水平的影响，并提出了控制茶叶中铅污染的相应问题和建议。     

酸化对茶园土壤矿物转变及供钾能力的影响

酸化是种植茶树后土壤变化的普遍现象。为了解酸化对茶园土壤矿质组分和钾素的长期影响,选择花岗岩发育的红壤茶园为研究对象,以相邻林地为对照,采用实地采样分析与模拟试验相结合的方法,研究长期种植茶树20 a和50 a后土壤酸化导致的土壤矿物和土壤钾素形态的变化,以及酸化对外源钾肥在土壤中钾形态转变的影响。结果表明,茶园土壤酸化降低了土壤缓效性钾的容量,减少了砂粒和粉粒中云母、长石等含钾矿物含量,促进了土壤黏粒中2∶1型（伊利石）矿物向1∶1型矿物（高岭石）的转变,降低了土壤总钾量。随着土壤酸度的增加,土壤中矿物态钾和缓效钾的比例逐渐下降,水溶态钾的比例逐渐增加。土壤酸化后,施入土壤中的钾主要以活性较高的水溶态和交换态存在,向非交换态转化的比例明显降低,土壤对外源钾的缓冲性逐渐下降。在酸性土壤中施用沸石可增强土壤对钾素形态转变的缓冲性。研究认为,茶园土壤酸化可显著降低土壤总钾量,减弱土壤供钾能力及对肥料钾的缓冲能力。     

Beta-N-methylamino-l-alanine: LC-MS/MS Optimization,Screening of Cyanobacterial Strains and Occurrence in Shellfish from Thau,a French Mediterranean Lagoon

β-N-methylamino-l-alanine (BMAA) is a neurotoxic non-protein amino acid suggested to be involved in neurodegenerative diseases. It was reported to be produced by cyanobacteria, but also found in edible aquatic organisms, thus raising concern of a widespread human exposure. However, the chemical analysis of BMAA and its isomers are controversial, mainly due to the lack of selectivity of the analytical methods. Using factorial design, we have optimized the chromatographic separation of underivatized analogues by a hydrophilic interaction chromatography coupled to tandem mass spectrometry (HILIC-MS/MS) method. A combination of an effective solid phase extraction (SPE) clean-up, appropriate chromatographic resolution and the use of specific mass spectral transitions allowed for the development of a highly selective and sensitive analytical procedure to identify and quantify BMAA and its isomers (in both free and total form) in cyanobacteria and mollusk matrices (LOQ of 0.225 and 0.15 µg/g dry weight, respectively). Ten species of cyanobacteria (six are reported to be BMAA producers) were screened with this method, and neither free nor bound BMAA could be found, while both free and bound DAB were present in almost all samples. Mussels and oysters collected in 2009 in the Thau Lagoon, France, were also screened, and bound BMAA and its two isomers, DAB and AEG, were observed in all samples (from 0.6 to 14.4 µg/g DW), while only several samples contained quantifiable free BMAA.     

Phytochemical analysis of wastewater (nejayote) obtained after lime-cooking of different types of maize kernels processed into masa for tortillas

In order to generate value-added products from the wastewater (nejayote) of lime-cooked maize for tortilla production, we analyzed the phytochemical composition of six different types of kernels that were optimally cooked. Kernels, masas and nejayote solids were analyzed in terms of free and bound phenolics, ferulic acid and antioxidant (AOX) capacity. The germplasm analyzed included white (NWH), yellow (NYE), white quality protein (QPM), red (RED), high-carotenoid (HCA) and blue (BLU). Approximately 87, 82 and 91% of the phenolics associated to raw kernels, masa and nejayote were bound. Total phenolics of nejayote were about twice as much compared to kernels and masa. Lime-cooking reduced around 1/3 of bound ferulic in masa but enhanced at least 10 times the liberation of free moieties. The nejayote solids contained approximately 125 and 10 times as much free ferulic and 15 and 53 times more bound ferulic compared to kernels and masa. The nejayote solids contained approximately 40 and 8 times higher free and 191 and 61 times higher bound AOX capacities compared to those exerted by raw kernels and masa, respectively. Therefore, the nejayote solids are promising as a source of antioxidants which are known to promote health benefits and combat oxidative stress.     

Phytochemical analysis of wastewater (nejayote) obtained after lime-cooking of different types of maize kernels processed into masa for tortillas

In order to generate value-added products from the wastewater (nejayote) of lime-cooked maize for tortilla production, we analyzed the phytochemical composition of six different types of kernels that were optimally cooked. Kernels, masas and nejayote solids were analyzed in terms of free and bound phenolics, ferulic acid and antioxidant (AOX) capacity. The germplasm analyzed included white (NWH), yellow (NYE), white quality protein (QPM), red (RED), high-carotenoid (HCA) and blue (BLU). Approximately 87, 82 and 91% of the phenolics associated to raw kernels, masa and nejayote were bound. Total phenolics of nejayote were about twice as much compared to kernels and masa. Lime-cooking reduced around 1/3 of bound ferulic in masa but enhanced at least 10 times the liberation of free moieties. The nejayote solids contained approximately 125 and 10 times as much free ferulic and 15 and 53 times more bound ferulic compared to kernels and masa. The nejayote solids contained approximately 40 and 8 times higher free and 191 and 61 times higher bound AOX capacities compared to those exerted by raw kernels and masa, respectively. Therefore, the nejayote solids are promising as a source of antioxidants which are known to promote health benefits and combat oxidative stress.     

伊斯帕汗小麦NAM-B1基因序列与蛋白质含量变异的分析

野生二粒小麦(Triticum dicoccoides Krn.,AABB,2n=4x=28)NAM-B1基因的表达可以加速植株衰老,促进叶片营养向籽粒转移,提高籽粒蛋白质、铁、锌等物质含量。本研究采用同源克隆方法从6份伊斯帕汗小麦(T.ispahanicum Heslot,AABB,2n=4x=28)中克隆得到5个NAM-B1基因。它们具有典型的NAM基因核苷酸结构特点,均含有3个外显子和2个内含子。与已报道的NAM-B1基因比对分析发现,居群PI330548中的NAM-B1基因因核苷酸序列上第11位点T的插入而引起移码突变,具有无功能型基因的结构特征,其他4个则具有功能类型基因的结构特征。4个功能类型NAM-B1基因的推导氨基酸序列一致性高达99.7%,它们之间仅有5个氨基酸的变异。供试的6份伊斯帕汗小麦之间籽粒蛋白质含量(GPC)存在显著差异。与高GPC材料PI346782相比,低GPC材料PI572904的NAM-B1基因编码氨基酸序列中存在2个位点的变异,分别为NAC域内的C亚区第88位Q→R和TAR区域第364位P→R的替换。推测伊斯帕汗小麦GPC的变异与其NAM-B1基因的这些突变存在一定关系。     

笋壳多糖脱蛋白方法的比较

为了研究笋壳多糖的脱蛋白工艺,以脱蛋白率、糖保留率和DPPH自由基清除能力为指标,对比研究了Sevag法、TCA法、酶法和醋酸铅法的笋壳多糖的脱蛋白效果。结果表明,最佳笋壳多糖脱蛋白方法为醋酸铅法,其脱蛋白工艺为：1 mg/mL糖液中添加醋酸铅使终浓度为1.0％,室温静置1 h,5 000 r/min离心20 min,最终脱蛋白率为80.17％,多糖保留率为81.12％,自由基清除能力为40.56％。该方法操作简便,脱蛋白效果好,且兼具良好的脱色澄清效果,适合工业上大规模生产使用。     

Iron Complexation to Oxygen Rich Marine Natural Products: A Computational Study

The natural products kahalalide F, halichondrin B, and discodermolide are relatively large structures that were originally harvested from marine organisms. They are oxygen rich structures that, to varying degrees, should have the ability to bind iron (II or III) by Fe-O and/or Fe-N bonds. In this semi empirical study, the binding of these natural products to iron (II) is studied and the aqueous stability factor (ASF) is used to determine which bonding configuration is most stable. The energy, the complex charge (+1), the average Fe-O (or Fe-N) bond distances and the dipole moments are used to calculate the ASF. The ASF provides insight to which complex will be the most stable and water soluble, important for a medicinal application. The ability of a molecule with a more than six oxygen and/or nitrogen atoms to bind iron (hexavalent, octahedral) by shifting which six atoms (O/N) are bound to the iron qualifies it as a polarity adaptive molecule.     

石墨消解-等离子体质谱法测定天然橡胶中14种元素的含量

建立了石墨消解-等离子体质谱（ICP-MS）法快速测定天然橡胶中铅、镉、铜、铬等14种无机元素的方法,旨在为天然橡胶中多元素检测标准的制定提供研究基础。通过优化石墨消解法的前处理条件,再应用ICP-MS测定天然橡胶样品中14种元素（Ba、Na、Mg、K、Ca、Cr、Mn、Fe、Ni、Cu、Zn、Cd、Pb、Co ）的含量,采用在线内标校正基体效应和信号漂移,以确保数据准确性。结果表明,该方法具有较低的检出限,检出限范围为0.0014~0.020 mg/kg,方法回收率86%~96%,RSD在0.53%~6.13%,得到的线性关系良好,充分满足实验要求。石墨消解法操作简便,可按照设定程序自动完成消解全过程,消解时间固定,适用于大批量样品的检测分析,同时,设备以及耗材成本较低。与传统干灰化-原子吸收光谱法相比,本检测方法更适用于天然橡胶中14种无机元素含量的测定,具有耗时短、干扰小、检测范围宽、处理效率高等优点,适用于大批量橡胶样品的多元素检测分析。已应用本实验方法,快速测定了我国6个橡胶主产区中的天然橡胶样品。     

Free and bound minor polar compounds in oats: Different extraction methods and analytical determinations

The extraction capacity of several solvent mixtures and comparison between alkaline and acid hydrolysis to extract free and bound minor polar compounds in oat samples were carried out. The extraction yield of each method was evaluated by correlating several spectrophotometric indices (absorption at 320 nm and total phenolic compounds by the Folin–Ciocalteu method) with HPLC-MS and the antioxidant activities of the oat extracts (DPPH radical method). The results showed that methanol and alkaline hydrolysis reported the highest recovery of polar compounds, and spectrophotometric indices overestimated the content of these compounds. Antioxidant compounds of five Romanian oat samples, named Comun, Jeremy, Mures, Lovrin 1, Lovrin 27-T were determined. Large intervarietal differences in phenolic compounds and their antioxidant activities among oat varieties were detected. Total minor polar contents content was in the range of 1179.47 and 1897.18 mg/kg of seed. According to the literature, we found that the majority of the minor polar compounds existed in bound form.     

羟磷灰石/SDBS丝网印刷碳电极快速测定茶叶痕量铅

为改善快速测定铅电化学传感器的稳定性、灵敏度和安全性,本研究利用SDBS（十二烷基苯磺酸钠）分散羟磷灰石替代惯用的有毒汞修饰丝网印刷碳电极,并滴加Nafion膜增加稳定性,构建了一种快速测定痕量铅的新型电化学传感器。采用方波溶出伏安法,支持电解质为0.1mol/L HAc-NaAc,在优化的羟磷灰石量、测试底液pH、富集时间等工作条件下,得到2~300μg/L线性范围内的铅标准曲线,检测限为0.46µg/L（S/N=3）;其重复性好,连续5次测定后的相对标准偏差为4.59%;本方法与ICP-MS法对茶叶样本的测定结果相近。研究出的快速检测铅的新型电化学传感器具有较好的稳定性、灵敏度和安全性,且测定结果准确,具有一定的应用潜力。