大鹏湾近岸海域水质状况与富营养化水平

根据2012—2016年大鹏湾近岸海域的监测资料,采用单因子污染指数法和有机污染指数法对海域海水水质状况进行评价;采用富营养化指数和潜在性富营养化指数对海域富营养化水平进行分析,并探讨其与环境因子盐度的相关性。结果表明:2012—2016年,大鹏湾近岸海域水质状况良好,满足GB 3097—1997《海水水质标准》中第二类海水水质标准,水质年际变化呈波动状态,无明显规律,空间分布上仅沙头角湾受到明显污染;富营养化水平基本表现为低营养,年际变化呈上升趋势,空间分布上仅沙头角湾和南澳湾分别呈现富营养和高富营养状态;潜在性富营养化主要集中在Ⅰ级(贫营养);大鹏湾近岸海域富营养化指数与盐度呈负相关,表明海域受河口冲淡水和陆源带来的低盐、高浓度的污染物影响较大。     

改进的QGA-BP模型在弥苴河总氮量预测中的应用

水质预测对水环境规划、评价和管理十分重要。构建一种改进的量子遗传算法（QGA）优化BP神经网络的模型,即在量子遗传算法中引入了旋转角的动态改进策略和遗传算法的交叉变异操作,并以改进的QGA作为进化操作准则优化BP模型的权值和阈值。以弥苴河复杂水环境水质预测为实例,选取一组历史观测数据作为训练样本,对其进行分析。将结果与BP模型、QGA-BP模型仿真结果进行了对比,改进后的QGA-BP模型在进化代数、收敛速度和预测结果的准确率有较大提高。对弥苴河水质的预测结果表明,将改进QGA-BP模型用于水质预测是可行、有效的预测方法。     

Effect of alginate on the aggregation kinetics of copper oxide nanoparticles (CuO NPs): bridging interaction and hetero-aggregation induced by Ca<Superscript>2+</Superscript>

The stability of CuO nanoparticles (NPs) is expected to play a key role in the environmental risk assessment of nanotoxicity in aquatic systems. In this study, the effect of alginate (model polysaccharides) on the stability of CuO NPs in various environmentally relevant ionic strength conditions was investigated by using time-resolved dynamic light scattering. Significant aggregation of CuO NPs was observed in the presence of both monovalent and divalent cations. The critical coagulation concentrations (CCC) were 54.5 and 2.9 mM for NaNO₃ and Ca(NO₃)₂, respectively. The presence of alginate slowed nano-CuO aggregation rates over the entire NaNO₃ concentration range due to the combined electrostatic and steric effect. High concentrations of Ca²⁺ (>6 mM) resulted in stronger adsorption of alginate onto CuO NPs; however, enhanced aggregation of CuO NPs occurred simultaneously under the same conditions. Spectroscopic analysis revealed that the bridging interaction of alginate with Ca²⁺ might be an important mechanism for the enhanced aggregation. Furthermore, significant coagulation of the alginate molecules was observed in solutions of high Ca²⁺ concentrations, indicating a hetero-aggregation mechanism between the alginate-covered CuO NPs and the unabsorbed alginate. These results suggested a different aggregation mechanism of NPs might co-exist in aqueous systems enriched with natural organic matter, which should be taken into consideration in future studies.

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Graphical abstract Hetero-aggregation mechanism of CuO nanoparticles and alginate under high concentration of Ca²⁺

     

2000~2014年武汉市城市扩展时空特征分析

基于不同时相的高分辨率遥感影像,采用面向对象的解译方法提取了武汉市2000、2005、2010和2014年的土地覆被信息,从城市扩展强度指数,城市中心坐标迁移和分形维数等方面分析了武汉市2000～2014年城市扩展时空特征。结果表明：2000～2014年间,武汉市城市扩展强度指数为1.41,各主城区城市扩展强度不一,洪山区建设用地的增加对主城区城市扩展的贡献最大;在扩展过程中,武汉市城市分形维数增加,城市空间形态变复杂;其扩展呈现核心-放射扩展模式,并逐渐转向圈层式;自然条件、经济、人口、交通、政策和城市规划是武汉市城市扩展的主要驱动力,但随着交通的发展,自然条件和经济对武汉市城市扩展的驱动作用正逐渐减弱。     

脆弱生态环境耦合下的贫困地区可持续发展研究

研究表明，中国贫困地区的分布与脆弱生态环境的分布存在一种地理空间意义上的耦合，这种耦合是一种非良性的耦合，存在着诸多问题并我着当地的社会经济发展，要改变这一现状，实现区域社会经济可持续发展，必须革新现有的贫困人口生存方式和社会经济发展模式，据此，本文提出了实现贫困地区社会经济可持续发展的战略措施应是依托现有的资源优势，推广生态农业技术，发展绿色食品和开展生态旅游。     

DOC/SCR组合方式及关键参数对NOx转化效率的影响

在柴油机中等转速下,通过改变柴油机氧化催化器（DOC）和选择性催化还原催化器（SCR）的组合方式,以及改变喷嘴位置、两级SCR载体间距和催化剂成分,获得各种条件下的NOx转化效率,为优化组合方式和关键参数提供重要数据支撑。结果表明：增加尿素喷嘴与SCR入口的相对距离,NOx转化效率升高,喷嘴距离为45 cm较为合适;载体间距的增大,NOx转化效率先略有升高,后急剧下降,间距为2 cm较为合适;载体体积增大,NOx转化效率明显升高,在满足目标NOx转化效率的前提下,载体体积不宜过大;DOC与SCR的组合方式对NOx转化效率具有明显差异,前置DOC能够有效的提高NOx转化效率;在催化条件下,NOx转化效率由高到低排序为：铜基 > 钒基 > 铁基;对于复合催化剂而言,铜铁复合基>铁铜复合基。     

甘肃合水地区全新世以来土壤剖面黑碳记录及其气候变化

针对甘肃合水马家村(MJC)全新世黄土剖面进行野外采样,分析磁化率和黑碳(焦炭和烟炱)等古气候指标,试图探讨黄土高原北部全新世以来生物质燃烧特征以及自然生态环境演变过程,结果表明:末次冰期和全新世早期(11500—8500 a BP)气候寒冷而干旱,区域野火事件时而发生,植被生物量是此阶段野火发生与蔓延的限制因素;距今8000年以来,黑碳和炭屑浓度整体呈现下降趋势。由于季节性降水增多从而抑制大范围火灾发生几率。然而,8000—7000 a BP和3500—2500 a BP野火频率明显上升,这可能与仰韶时期老官台文化和寺洼文化时期的古人类放火烧荒和开垦农田等活动有关;全新世晚期(3100 a BP至今)气候进一步干旱,生物质燃烧增强与人口增加和人类土地利用水平密切相关,其中1500—1000 a BP出现一次较为明显的峰值,这可能与隋唐以来该区农耕活动加强有关。可见,近2000年以来黄土高原北部地区生物质燃烧特征受到气候和人类活动复合驱动所控制。     

信号分子强化改性挂膜沸石持续抑制沉积物中氨氮释放

为寻找一种长期有效的底泥修复方式,对沸石进行了改性并挂膜的实验.考察了 4种铝盐[AlCl3、Al(NO3)3、Al2(SO4)3和KAl(SO4)2]改性挂膜沸石对上覆水中氨氮的去除情况.结果表明,AlCl3改性挂膜沸石效果最佳,且最佳改性浓度为0.8 mol·L-1.进一步分析添加信号分子OHHL后,AlCl3改性...     

The effects of autophagy on vascular endothelial cells induced by airborne PM2.5

The purpose of this study was to examine the direct toxicity of PM2.5 collected from Beijing on human umbilical vein endothelial cells(HUVEC). A Cell Counting Kit 8(CCK8) assay demonstrated that PM2.5 exposure decreased the proliferation of HUVECs in a dosedependent manner. We also found that PM2.5 exposure induced autophagy in HUVECs, as evidenced by:(1) an increased number of double-membrane vesicles;(2) enhanced conversion and punctuation of the microtubule-associated protein light chain 3(LC3); and(3) decreased levels of the selective autophagy substrate p62 in a time-dependent manner.Furthermore, promoting autophagy in PM2.5-exposed HUVECs with rapamycin increased the cell survival rate, whereas inhibiting autophagy via 3-methyladenine significantly decreased cell survival. These results demonstrate that PM2.5 exposure can induce cytotoxicity and autophagy in HUVECs and that autophagy play a protective role against PM2.5-induced cytotoxicity. The findings of the present study imply a direct toxic effect of PM2.5 on HUVECs and provide novel insight into the mechanism of cardiovascular diseases caused by PM2.5 exposure.     

Selection of appropriate organic additives for enhancing Zn and Cd phytoextraction by hyperaccumulators

Chelant-enhanced phytoextraction is one of the most promising technologies to remove heavy metals from soil. The key of the technology is to choose suitable additives in combination with a suitable plant. In the present study, laboratory batch experiment of metal solubilization, cress seeds germination were undertaken to investigate the metal-mobilizing capability and the phytotoxicity of organic additives, including ethylene diamine triacetic acid （EDTA）, citric acid, acetic acid, oxalic acid, glutamine and monosodium glutamate waste liquid （MGWL） from food industry. Experiments in pots were carried out to study the effects of the additives on Zn and Cd phytoextraction. Furthermore, a leaching experiment with lysimeter was performed to evaluate the environmental risks of additive-induced leaching to underground water. The results showed that EDTA had a strong mobilizing ability for Zn and Cd, followed by mixed reagent （MR） and MGWL. MGWL and acetic acid at 5 mmol equivalent per liter resulted in seed germination index less than 2%. Experiments in pots verified the phytotoxicity of acetic acid and MGWL. Addition of the mixed reagent at 6--10 mmol/kg significantly increased Zn phytoextraction by Thlaspi caerulescens. The same for EDTA and the mixed reagent at 10 mmol/kg by Sedum dfredii. But only mixed reagents could significantly increase Cd phytoextraction by the studied hyperaccumulators. This suggested that the strong chelant was not always the good agent to enhance phytoextraction. S. alfredii combined with 2--10 mmol/kg soil MR was preferred for phytoremediation of Cd/Zn contaminated soils in southern China, this could result in high phytoextraction of Cd/Zn and reduce the leaching risk to underground water than EDTA assisted phytoextration.