Application of Response Surface Methodology to Analyze the Effects of Soil/Liquid Ratio,pH, and Incubation Time on the Bioaccessibility of PAHs from Soil in In Vitro Method

Water, Air, & Soil Pollution - Central composite design using response surface methodology was employed to optimize soil/liquid ratio (S/L), pH, and incubation time for polycyclic aromatic...     

大别山区板栗林地水土流失特性研究

[目的]研究大别山区板栗林地水土流失特性,为该区水土流失综合防治和生态安全保障工作提供科学支持。[方法]以“全国板栗第一县”湖北省罗田县为典型,通过对10°,15°,20°共3种坡度板栗林及对照10°,15°撂荒小区2014—2018年的降雨、径流、泥沙、植被覆盖度进行观测分析,研究大别山区板栗林下水土流失特性。[结果](1)在同等坡度和降雨条件下,虽然板栗林植被覆盖度更高,但其土壤侵蚀程度较撂荒地更加严重,说明板栗林存在较明显的林下水土流失;(2)植被覆盖度越低土壤侵蚀越严重,但植被覆盖度最高时土壤侵蚀程度并不一定最弱,说明由于林分结构的复杂性,即使在相同降雨、土壤、坡度条件下,植被覆盖度也不能作为反映土壤侵蚀程度的唯一指标;(3)板栗林水土流失程度并非随坡度的增大而增大,其侵蚀峰值(临界坡度)在15°左右。[结论]大别山区板栗分布广泛,其林下水土流失现象需要引起科研和管理部门的进一步关注。     

基于PSO-BP的甘蔗施肥监控系统设计与试验

针对甘蔗横向种植机的施肥机构由于肥料潮湿结块易堵塞等问题,该研究对施肥机构进行电液传动与控制改造,构建了一套基于粒子群（Particle swarm optimization,PSO）-前反馈（Back Propagation,BP）神经网络预测的施肥监控系统。以施肥马达的压力、转速及肥料箱中肥料量为输入参数,将施肥机构的工作状态（空载状态、正常状态、重载状态、堵塞状态）作为输出,通过BP算法建立输入与输出之间的映射关系,并用PSO算法优化BP算法的权值与阈值,相比未优化BP算法,优化后的工作状态预测准确率由97%提高到99%。以识别施肥机构工作状态响应准确率以及重载状态下堵塞预防概率为试验指标进行车间试验,结果表明：工作状态响应识别准确率为89%;重载状态下,控制系统控制施肥马达正反转并消除堵塞的概率为87.5%。在田间试验中,监控系统能准确预测施肥机构的重载状态并自动执行防堵控制指令,没有出现堵塞故障。该施肥防堵塞监控系统无需上位机,能够满足复杂多变工况下施肥机构的工况预测及防堵控制要求,可为其他施肥机构的自动化改造提供参考。     

混合盐胁迫对马蔺幼苗根系构型及生长量的影响

为探讨不同种类盐胁迫对马蔺幼苗生长状况的影响,采用室内培养的方法,研究总质量浓度为0.3%的NaCl、NaHCO₃单盐溶液及其不同配比的混合盐溶液胁迫对马蔺(Iris lactea var. chinensis)幼苗生长量、地上部干鲜重比值、地下部干鲜重比值以及根系构型的影响。结果表明,随着胁迫时间的延长,0.3%NaCl溶液对叶数和株高增长量的影响最小,其次为3种混合盐溶液,各处理在第14天时株高增幅达到最大。经0.3%NaHCO₃处理后的幼苗地上部干鲜重的比值为空白对照的2.17倍,地下部干鲜重则为空白对照的56.61%,随着混合溶液中NaHCO₃浓度的上升,地上部干鲜重比值表现出上升的趋势,地下部干鲜重比值则表现出下降的趋势。经35天处理后,0.3%NaHCO₃胁迫的马蔺幼苗根系总长、根系表面积较对照均显著下降,降幅分别为39.73%、26.08%,而各处理间的根系体积却无显著差异。研究结果显示,0.3%NaHCO₃溶液对马蔺幼苗的胁迫作用最强,2种单盐对根系的胁迫作用强于混合盐胁迫,而0.3%NaCl溶液对生长量的胁迫作用最弱。     

Distribution characteristics and influencing factors of soil organic carbon in alpine ecosystems on the Tibetan Plateau transect, China

The undisturbed regions along the Qinghai-Tibet Highway crossing the natural zones of montane desert, alpine meadow-steppe, and montane shrub-coniferous forest were chosen as the study areas. Soil samples were collected at 23 sites and the relations between the influencing factors and distribution of soil organic carbon (SOC) content were studied. The results indicated that the order of SOC content for the whole soil profile with different vegetations and in the horizontal direction was shown as below: forest>shrub>meadow>steppe>desert. All the SOC contents of the top 10 cm soil layers of forest, shrub and meadow vegetations, as well as that of the top 20 cm soil layers in steppe, in the vertical direction, were higher than those of corresponding lower soil layers. However, the SOC content in the desert soil was in accordance. The grey correlative analysis between the climatic factors and SOC content in the top soil show that precipitation was the dominant climatic factor affecting the distribution of SOC in the Tibetan Plateau transect. The influence of precipitation on the horizontal distribution of SOC decreased with the increase of precipitation in the horizontal direction. The vertical distribution of SOC along the soil profile was greatly affected by precipitation or the soil clay content in top soil layers, and was clearly influenced by soil silt content or sand content in lower soil layers, as well. The influences of both soil bulk density and soil pH on the vertical distribution of SOC along the soil profile gradually declined. The plant biomass was the most important biotic factors affecting the distribution of the SOC. __________ Translated from Journal of Zhejiang University (Agriculture & Life Sciences), 2007, 33(4): 443–449 [译自: 浙江大学学报(农业与生命科学版)]     

Long-term cultivation impact on the heavy metal behavior in a reclaimed wetland,Northeast China

Purpose

Heavy metal fractionation varies according to land uses. To understand the behavior of heavy metals in wetland soils under long-term agricultural cultivation, we examined the distribution, source, and associated environmental risk of heavy metals in different types of wetland soils.

Materials and methods

Soils were collected in cultivated lands, artificial ditches, and riparian zones from a reclaimed wetland in the Sanjiang Plain, Northeast China. They were analyzed for total concentrations and chemical fractions of Pb, Cd, Cu, Zn, Cr, and Ni, as well as pH, soil organic matter, total phosphorus, and particle size distribution.

Results and discussion

Heavy metal concentrations were significantly lower in cultivated wetland than in ditch and riparian wetlands. Riparian wetland was found to exhibit the highest metal concentrations. When compared with other two wetland types, the cultivated wetland showed much higher partitioning levels of heavy metals in the acid-soluble fraction and lower partitioning levels in the oxidizable fraction. Although Cr, Cu, and Ni in ditch and riparian wetlands were identified as the metal pollutants of primary concern, they had a low or no risk of further dispersion to other environmental components. Weathering of parent materials was the main source of Cr and Cu, Pb, Cd, and Zn originated mainly from agricultural practices, and Ni emanated from a mixture of sources.

Conclusions

Long-term agricultural cultivation can lead to significant heavy metal loss in cultivated wetland but enrich heavy metal concentrations in ditch and riparian wetlands. Periodic ditch dredging is considered an effective measure for decreasing heavy metal input into the fluvial system and thereby reducing the dispersion to the regional water environment.     

不同种植间距对香根草植物边坡优先流发育特征的影响

[目的]分析优先流在香根草边坡中的发育特征,研究植物根系与优先流之间的关系,为进一步研究降雨条件下植物根系对边坡土体稳定性的影响提供理论依据。[方法]以种植间距为50 cm和10 cm的香根草为研究对象,模拟30 mm和50 mm两种不同的降雨量,采用示踪剂试验研究了香根草边坡土壤的优先流发育特征。[结果]香根草种植间距从50 cm减少到10 cm会增大边坡的水力响应。在50 mm的降雨量作用下,10 cm种植间距的香根草边坡土壤的染色面积比率和优先流比分别是50 cm的1.55,1.76倍。表层土0—10 cm土层深度范围内染色路径数量变化不明显,在10—35 cm深度土层范围,10 cm种植间距的染色路径数量多于50 cm种植间距的香根草边坡土壤。当降雨量由30 mm增加至50 mm时,水流会通过优势通道更迅速迁移到边坡土壤中。降雨量为30 mm土壤的染色面积比率(36.11%)和优先流比(67.25%)小于50 mm土壤的染色面积比率(49.68%)和优先流比(79.96%),并且染色路径数量随着降雨量的增加而增多。[结论]香根草根系特征与优先流关系密切。选择植物护坡时,应合理选...     

GC-MS鉴定叶绿素皂化母液提取物

本文报道GC-MS鉴定莫合烟叶叶绿素皂化母液提取物。分离出75个组份,鉴定其中主要组份为叶绿醇,含量13.18％;十六碳醛,含量11.52％;6,10,14-三甲基-2-十五酮,含量6.24％;3-甲基戊酸乙酯,含量5.05％;1-甲基戊苯,含量2.96％;9,12,15-十八碳三烯酸乙酯,磷量2.03％,叶绿醇、十六碳醛,6,10,14-三甲基-2-十五酮和十八碳三烯酸乙酯均有利用价值。     

Atomically resolved single-walled carbon nanotube intramolecular junctions

Intramolecular junctions in single-walled carbon nanotubes are potentially ideal structures for building robust, molecular-scale electronics but have only been studied theoretically at the atomic level. Scanning tunneling microscopy was used to determine the atomic structure and electronic properties of such junctions in single-walled nanotube samples. Metal-semiconductor junctions are found to exhibit an electronically sharp interface without localized junction states, whereas a more diffuse interface and low-energy states are found in metal-metal junctions. Tight-binding calculations for models based on observed atomic structures show good agreement with spectroscopy and provide insight into the topological defects forming intramolecular junctions. These studies have important implications for applications of present materials and provide a means for assessing efforts designed to tailor intramolecular junctions for nanoelectronics.     

镁基碱金属二元合金热力学性质的理论计算

本文运用Ｍｉｅｄｅｍａ理论，系统地计算了镁与碱金属组成的二元合金系统的液态混和焓和固态合金形成焓。根据理想溶液理论，还计算了Ｌｉ－Ｍｇ系统在１０００Ｋ时的熵、以及自由能－成分曲线，所得的结果同已有的实验结果和第一原理赝势方法计算的结果符合得比较好。