Influence of pH on the release and chemical fractionation of heavy metals in sediment from a suburban drainage stream in an arid mine-based oasis

Purpose

The objectives of this study were to explore the influences of pH on the release of Cu, Zn, Cd, Pb, Ni, and Cr in sediments derived from the upstream, middle, and downstream reaches of Dongdagou stream in Gansu Province, Northwest China, and to examine the fractionation changes of heavy metals in the sediments after reaching their release equilibrium under different pH conditions.

Materials and methods

Sediment samples were obtained using a stainless steel grab sampler to collect the uppermost 10 cm of sediment from the channel bed. The pH-dependent release experiment was conducted in the solid-to-liquid ratio of 1:20 at different pH values (2, 4, 6, 8, 10, and 12) at room temperature. The total Cu, Zn, Cd, Pb, Ni, and Cr concentrations in the sediments were digested using an acid digestion mixture (HNO₃ + HF + HClO₄) in an open system. Metal fractionation of selected sediments was obtained using the Tessier sequential extraction procedure. Heavy metal concentrations in the samples were determined using atomic absorption spectrophotometry.

Results and discussion

The mean concentrations of heavy metals in sediments decreased in the following order: Zn (1676.67 mg kg^?1) > Pb (528.65 mg kg^?1) > Cu (391.34 mg kg^?1) > Cr (53.48 mg kg^?1) > Ni (34.27 mg kg^?1) > Cd (11.53 mg kg^?1). Overall, the solubility of Cu, Zn, Cd, Pb, and Ni decreased with increasing pH, and they were strongly released at pH 2. Moreover, the solubility of Cr increased with increasing pH, and its release was highest at pH 12. After reaching the release equilibrium of heavy metals under different pH conditions, the percentages of organic Cu, Zn, Cd, and Fe-Mn oxyhydroxide Pb decreased, compared to their initial fractions. The residual fractions of Ni and Cr were dominant, regardless of pH.

Conclusions

The average concentrations of Cu, Zn, Cd, and Pb in sediments were highly elevated compared with the soil background values in Gansu Province, China. The results of this pH-dependent release experiment showed that the release behaviors of Cu, Zn, Pb, and Cr followed an asymmetric V-shaped pattern, whereas Cd and Ni followed an irregular L-shaped pattern. The changes in the release of heavy metals in sediments were related to their redistribution between chemical fractionations.

     

大黄素对人肺癌A549细胞增殖、凋亡的影响及机制探讨

研究大黄素对人肺癌A549细胞的药效及其诱导细胞凋亡的分子机制。通过MTT法检测大黄素对A549细胞的杀伤作用;通过Annexin V-FITC/PI双染和流式细胞术检测大黄素对A549细胞的凋亡作用;通过免疫印迹法检测细胞凋亡相关蛋白的表达量变化。大黄素对A549细胞具有良好的杀伤作用且呈浓度依赖性;荧光显微镜和流式细胞术检测发现大黄素能够诱导A549细胞的凋亡且呈时间依赖性;Western blot检测显示大黄素处理A549细胞后,p-AKT、Bcl-2的表达量明显减少,Bad和cleaved-caspase-3的表达水平明显增加。大黄素通过调控AKT信号传导途径诱导人肺癌A549细胞的凋亡。     

Morphological and genetic analysis of a cleistogamous mutant in rapeseed (<Emphasis Type="Italic">Brassica napus</Emphasis> L.)

Cleistogamy, the trait of non-opening flowers, is considered to be beneficial as it reduces the threat of genetic contamination and gene flow from genetically modified varieties into other crops or native species. A cleistogamous mutant Zhong9-Clg obtained in the rapeseed cultivar Zhongshuang 9 population (Brassica napus L.) treated by ethylmethanesulfonate were investigated. Mutation had pronounced effect on petal and sepal epidermal cells resulting in the inhibition or delay of petal development, forming folded petals which ultimately resulted in cleistogamous flowers. Genetic investigation revealed that this trait was monogenic and the allele for cleistogamy was dominant. Most of the eight agronomic traits tested, including seed yield per plant, were not significantly different between the mutant and wild type plants. Fertility of the cleistogamous mutant Zhong9-Clg was not significantly affected by mutation. Our research findings will lay the foundation for the development of the cleistogamous varieties that could be used in controlling the gene flow in rapeseed in combination with other means of containment strategies.     

多端元光谱解混模型的改进及对植被盖度的反演

以扎龙自然保护区为研究对象,运用分层的面向对象分类法与多端元光谱解混算法相结合反演该地区的植被覆盖度。结果表明:分层降低了场景复杂度,面向对象分类法与多端元光谱解混算法的结合,有效的减少了计算量和混合像元的端元变化;采用同期高分辨率的SPOT5多光谱遥感影像进行精度验证,与传统的多端元光谱解混模型的反演结果进行对比,相关系数从0.864 3提高到0.902 8,均方根误差从0.171 2减少到0.092 6。因此,分层面向对象多端元光谱解混模型适合对湿地植被覆盖度的反演。     

基于ABAQUS的子午线轮胎接地特性研究

为研究子午线轮胎接地特性的变化规律,利用ABAQUS建立了考虑轮胎非线性的有限元模型,基于轮胎额定胎压下的截面应力分布对模型进行了验证.研究了胎压和载荷对轮胎接地特性的影响.结果表明:在额定胎压下,轮胎的接地印痕近似为椭圆形,接地应力由中心向四周递减;在额定负载下,随着胎压的下降,法向应力的集中区域逐渐向印痕边缘偏移,...     

稻田稗草对噁唑酰草胺的抗药性水平和ACCase活性

为明确稻田稗草Echinochloa phyllopogon(Stapf.)Koss.对噁唑酰草胺的抗药性水平,在对采自辽宁省、黑龙江省、湖南省和江西省共20个水稻产区的稗草种群按田间推荐剂量筛选后,测定了疑似抗药性稗草种群BN-1、BN-16、BN-17和疑似敏感性稗草种群BN-20的整株抗药水平,并离体测定了不同种群体内乙酰辅酶A羧化酶(acetyl co-enzyme A carboxylase,ACCase)对噁唑酰草胺的敏感性。结果显示,在田间推荐剂量下,种群BN-1、BN-16、BN-17和BN-20相对鲜重分别为92.6%、86.6%、64.9%和1.1%。相比种群BN-20,种群BN-1、BN-16和BN-17对噁唑酰草胺敏感性较低,抗性指数分别为33.83、30.07和14.87;ACCase活性测定结果显示,种群BN-1、BN-16和BN-17的抗性指数分别为33.71、27.16和15.23。结果表明稗草种群BN-1、BN-16和BN-17均对噁唑酰草胺产生了抗药性,抗性程度依次为BN-1BN-16BN-17,而其体内ACCase敏感性降低可能是其产生抗药性的原因之一。     

松毛虫赤眼蜂对三种农田常用杀虫剂的敏感性

为明确常用杀虫剂对松毛虫赤眼蜂Trichogramma dendrolimi的安全性,室内评估了高效氯氰菊酯、阿维菌素和氯虫苯甲酰胺3种药剂对其成蜂的急性毒力以及田间推荐使用剂量对赤眼蜂各发育阶段的间接影响,并模拟自然情况,测定了不同残留期的3种药剂对赤眼蜂存活和寄生能力的影响.结果表明:以LC₅₀进行评估,对松毛虫赤眼蜂毒力最高的为阿维菌素,其次是高效氯氰菊酯,氯虫苯甲酰胺毒力最小;在田间推荐使用剂量下,阿维菌素、高效氯氰菊酯和氯虫苯甲酰胺的安全系数分别为0.017、0.066和69.175;在推荐使用剂量下,氯虫苯甲酰胺处理含有不同发育阶段赤眼蜂的米蛾Corcyra cephalonica卵后,平均羽化率最高为90.43%,其次是高效氯氰菊酯为56.46%,阿维菌素仅为9.84%;接触0~7 d残留期阿维菌素的玉米叶片24 h,松毛虫赤眼蜂全部死亡,无米蛾卵被寄生,但接触3~7 d残留期氯虫苯甲酰胺的玉米叶片,赤眼蜂的死亡率和寄生米蛾卵数量与清水对照无明显差异.表明在实施释放赤眼蜂的害虫综合治理方案中,应尽量避免使用阿维菌素,而氯虫苯甲酰胺对赤眼蜂风险性极低,具有很好的相容性,可以推广使用.     

昆虫基因组组装大小偏差的原因解析

为明确昆虫基因组组装大小产生偏差的原因,利用流式细胞术估测来自6目10科的21种常见农业昆虫的基因组大小,同时从动物基因组大小数据库收集和整理1 345个经流式细胞术估测的昆虫基因组大小信息,并从NCBI、GigaDB、DDBJ、i5k workspace@NAL、InsectBase和VectorBase等14个物种遗传信息数据网站获取536种昆虫的基因组组装信息进行比较分析。结果表明,收集的昆虫中有202种同时具有流式细胞术估测的基因组大小和基因组组装大小的信息,以更接近真实值的流式细胞术估测基因组大小为参照,比较发现其中42种昆虫的基因组组装大小偏大,98种昆虫的基因组组装大小偏小,而62种昆虫的基因组组装大小和经流式细胞术估测大小相似。基因组组装大小比经流式细胞术估测大小更大的物种,通过Wilcoxon秩和检验发现显著具有更多的重复序列,但与GC含量、contig N50及基因组测序和组装策略并无显著相关性。综合分析认为,在大多数情况下昆虫基因组组装大小更小,表明组装并不完整,但在重复序列占比较高的情况下,昆虫基因组的组装出现了冗余,导致组装大小更大。     

高效液相色谱法测定台农19号菠萝糖分

以90%乙醇作为提取液,色谱柱为CHO-820钙型阳离子交换柱,柱温为90℃,流动相为超纯水,流速为0.5mL/min,进样体积为10μL,用示差折光检测器检测不同季节成熟的台农19号菠萝果实中的糖类,结果表明:该测定方法的相对标准偏差为0.38%～1.35%,相关系数在0.9998以上,加标回收率为98.34%～100.40%;不同季节成熟的台农19号菠萝果肉的含糖量存在较大差异,夏季果的含糖量最高,秋季果次之,冬季果最低,其中蔗糖含量的季节性差异最为明显。     

农业信息市场化传播运行机制研究 ——以大荔模式为例

陕西省大荔县将农业信息服务中的公益性服务和经营性服务进行有机整合,构建了一种新型科技服务体系(简称为大荔模式),这是对国内农业信息传播模式的有益探索.笔者以陕西大荔模式为例,通过实地调研了解大荔模式的建设情况,对大荔模式的运行机制进行了分析.研究发现,保障机制是大荔模式运行机制的重要组成部分,利益分配机制是大荔模式运行...