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981.
施用碱渣对茶园土壤酸度和茶叶品质的影响 总被引:4,自引:0,他引:4
开展田间小区试验研究了不同施用量条件下碱渣对酸化茶园土壤的酸度和茶叶品质的影响.结果表明,施用碱渣可以显著提高土壤pH、土壤交换性盐基和盐基饱和度,降低土壤交换性酸和交换性铝含量,并使土壤中钙、镁养分保持合理比例.施用碱渣提高了茶叶中茶多酚、儿茶素、咖啡碱、氨基酸和叶绿素含量,降低了茶叶中铅含量,使茶叶品质得到改善.碱渣施用量为4 500 kg·hm-2时,可将土壤pH值调节至5.51,达到最适合茶树生长的酸度条件,该条件下生产的茶叶品质也最佳,茶叶茶多酚、儿茶素、咖啡碱、氨基酸和叶绿素含量分别比对照提高22.5%、27.8%、34.9%、69.0%和52.1%,而Pb含量下降51.2%. 相似文献
982.
Occurrence, distribution, and source of polybrominated diphenyl ethers in soil and leaves from Shenzhen Special Economic Zone, China 总被引:2,自引:0,他引:2
Pei-Heng Qin Hong-Gang Ni Yang-Sheng Liu Ye-Hong Shi Hui Zeng 《Environmental monitoring and assessment》2011,174(1-4):259-270
Polybrominated diphenyl ethers (PBDEs) were measured in soil and three plant species samples taken at different land use areas in Shenzhen China. The concentrations of ??7BDEs (BDE-28, BDE-47, BDE-99, BDE-100, BDE-153, BDE-154, and BDE-183) and BDE-209 in the surface soils ranged from 0.23 to 271 and 8.9 to 5,956 ng/g dry weight (dw), respectively. These figures are comparable to that in the soils of electronic waste dismantling sites. BDE-209 was the predominant congener (contributes 85?C99% of ??8PBDEs (??7PBDEs plus BDE-209)) in soils. The regression slopes of total organic carbon and individual BDE congeners were rather gentle, indicating that factors other than soil organic matter regulated the soil concentrations. Proximity to sources of deposition processes might be the major factors. In the plant leaves, ??7BDEs and BDE-209 concentrations ranged from 1.29 to 5.91 and 5.49 to 28.2 ng/g dw, respectively. BDE-209 is also the dominant component, but the contribution was much lower compared with that in soils. Bauhinia purpurea Linn. and Michelia alba DC. show some similarities on the uptake of PBDEs, while Ficus microcarpa var. pusillifolia is different from them. The correlations between plant leaf concentrations and predicted gaseous concentrations were moderate, indicating that gaseous concentration did not influence the leaf concentration significantly. 相似文献
983.
Changes in the area of inland lakes in arid regions of central Asia during the past 30 years 总被引:5,自引:0,他引:5
Jie Bai Xi Chen Junli Li Liao Yang Hui Fang 《Environmental monitoring and assessment》2011,178(1-4):247-256
Inland lakes are major surface water resource in arid regions of Central Asia. The area changes in these lakes have been proved to be the results of regional climate changes and recent human activities. This study aimed at investigating the area variations of the nine major lakes in Central Asia over the last 30 years. Firstly, multi-temporal Landsat imagery in 1975, 1990, 1999, and 2007 were used to delineate lake extents automatically based on Normalized Difference Water Index (NDWI) threshold segmentation, then lake area variations were detailed in three decades and the mechanism of these changes was analyzed with meteorological data and hydrological data. The results indicated that the total surface areas of these nine lakes had decreased from 91,402.06 km2 to 46,049.23 km2 during 1975?C2007, accounting for 49.62% of their original area of 1975. Tail-end lakes in flat areas had shrunk dramatically as they were induced by both climate changes and human impacts, while alpine lakes remained relatively stable due to the small precipitation variations. With different water usage of river outlets, the variations of open lakes were more flexible than those of other two types. According to comprehensive analyses, different types of inland lakes presented different trends of area changes under the background of global warming effects in Central Asia, which showed that the increased human activities had broken the balance of water cycles in this region. 相似文献
984.
985.
986.
为计算建筑施工安全系统的效能,基于ADC效能评估模型,尝试构建建筑施工安全系统效能的测算方程,该系统方程包括建筑施工安全可用度A的测算、建筑施工安全可信度D的测算、建筑施工安全固有能力C的测算和建筑施工安全效能干扰因子G的测算,进而推导出建筑施工安全系统效能评估的一般数理模型及特定模型,并以脚手架搭设系统为例进行效能测算。算例表明该数理模型可以较准确计算建筑施工安全子系统的效能。 相似文献
987.
基于遗传算法的支持向量机预测有机物自燃点的研究 总被引:1,自引:1,他引:0
根据定量构效关系(QSPR)原理,研究自燃点(AIT)与其分子结构间的内在定量关系。以265种有机化合物作为样本集,随机选择238种作为训练集,27种作为测试集,用遗传算法(GA)进行变量选择,分别建立多元线性回归(MLR)模型和支持向量机(SVM)模型研究有机物的自燃点与其分子结构间的关系。通过分析,发现造成模型预测效果不佳的原因是试验数据本身存在问题。通过对2个模型的比较,结果为GA-SVM模型明显优于GA-MLR模型,说明自燃点与其分子结构间具有很强的非线性关系。 相似文献
988.
采用间接阳极氧化处理活性染料模拟废水,以自制钛基IrO2电极为阳极,石墨为阴极,NaCl为支持电解质,考察了Ti/IrO2电极间接阳极氧化活性橙X - GN模拟废水的处理效果,研究了pH值、电压、电解时间及NaCl投加量对其降解效果的影响.结果表明,在pH值为3,电压为20V,NaCl投加量为2.5 g/L,室温条件下,电解30 min后该染料的脱色率达到100%,电解60min后COD去除率可达68%.在本试验条件下,染料通过电解产生的Cl2、ClO -、HClO等物质间接氧化降解.为探讨电化学氧化降解活性橙X - GN的过程,对该染料的降解过程进行UV - Vis光谱分析,初步探讨了该染料的降解规律.在电解过程中,染料的发色偶氮共轭体系首先被破坏,染料溶液的颜色逐渐褪去;经偶氮双键形成的共轭体系被破坏的同时,染料结构中的苯环结构、均三嗪结构以及萘环结构也遭到破坏,UV - Vis光谱中各基团的特征吸收峰基本消失;反应60 min后,UV - Vis光谱中已无明显吸收峰,表明该染料降解效果较好. 相似文献
989.
To reduce the leaching potential, to prevent groundwater contamination and to maintain the efficacy of a pesticide, natural polysaccharides have received increasing attention due to their biocompatibility and useful biological reactivity for controlled release formulations (CRFs) of pesticides. In this paper, the toxicities of the chiral herbicide dichlorprop (DCPP) and its complexes with chitosan molecules (DCPP-CS) and chitosan nanoparticles (DCPP-NP) to two different green algae were determined and compared. The inhibition rates of DCPP, DCPP-CS and DCPP-NP were determined at 24, 48, 72, 96, 120, 144, 168 h, and the results show that (S)-DCPP was more toxic to Chlorella vulgaris than (R)-DCPP, while the (R)-DCPP was more toxic to Scenedesmus obliquus than (S)-DCPP. The study also found that the chiral selectivity of DCPP to Chlorella vulgaris and Scenedesmus obliquus could be changed when DCPP was complexed with chitosan molecules (CS) or chitosan nanoparticles (NP). For Chlorella vulgaris, the order of inhibition was (R)-DCPP-CS > (S)-DCPP-CS and (R)-DCPP-NP > (S)-DCPP-NP; for Scenedesmus obliquus, the order was (S)-DCPP-CS > (R)-DCPP-CS and (S)-DCPP-NP > (R)-DCPP-NP. This phenomenon suggests that the enantioselective behaviors of chiral compounds might shift when interactions with other chiral receptors coexist in different biological environments. Additionally, chitosan molecules and chitosan nanoparticles also showed different toxicities, which could be ascribed to the difference in the physicochemical properties between CS and NP or the differences in the cell walls of the two fresh water green algae. 相似文献
990.
To determine the incidence of organochlorine pesticides (OCPs) in soil in a rapid urbanization region, soil samples from various land use types in Shenzhen were collected in winter, 2007. The concentration of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs) ranged from non-detected to 149 ng g(-1) and 19 to 88 ng g(-1), respectively. The highest levels of OCPs were observed in soil from traffic and industry areas, reflecting that intensive human disturbance make the soil pollution accumulation more disperse. HCHs and DDTs profiles revealed that the sources were associated mainly with lindane and technical DDTs, respectively, while HCHs in the soil of Shenzhen might originate from both recent and historical sources. The loss of OCPs by soil erosion will enter surface runoff and impose impact on the water environment. Non-dietary exposure estimation indicates that children were the most sensitive group. The average daily exposure to OCPs for males was more serious than for females. Non-dietary exposure to DDTs and HCHs in residential blocks of Shenzhen were far below the acceptable daily intake recommended by the Food and Agriculture Organization/World Health Organization. 相似文献