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991.
反硝化(DNF)和硝酸盐异养还原为氨(DNRA)是水域生态系统中硝酸盐异养还原的2个主要过程.DNF和DNRA之间的竞争控制着硝酸盐在水域生态系统中的异养还原方式和最终归趋.选取太湖流域的傀儡湖为研究对象,采用室内培养实验和稳定氮同位素示踪技术,考察傀儡湖沉积物-水界面的DNF和DNRA速率及其对硝酸盐异养还原过程的贡献.结果显示,沉积物表现为NH4+-N的源和NO3--N的汇,潜在DNF速率为18.89~54.00μmol/(kg·h)[均值(36.39±3.86)μmol/(kg·h)],DNRA反应速率为1.02~5.89μmol/(kg·h)[均值(3.21±1.15)μmol/(kg·h)].DNF与沉积物有机质含量和含水率存在显著的正相关关系,DNRA与沉积物需氧量(SOD)之间存在相关性.反硝化是傀儡湖中硝酸盐异养还原的主导过程,贡献率为84.23%~96.90%,而DNRA过程只占3.10%~15.77%.与海洋河口区域相比,淡水湖泊生态系统中DNRA速率和DNRA在硝酸盐异养还原中所占的比重均较小. 相似文献
992.
Effects of Tourism and Topography on Vegetation Diversity in the Subalpine Meadows of the Dongling Mountains of Beijing,China 总被引:1,自引:0,他引:1
Subalpine meadows in the Dongling Mountains (located at E115o26′-115o40′, N40o00′-40o05′) of Beijing, China are important
for tourism and the provision of ecosystem services. However, because of poor management serious degradation has occurred
on these subalpine meadows. The aim of this paper is to present a quantitative analysis of effects of tourism disturbance
and topography on the status and diversity of montane meadow communities and to provide direction for improved management.
Sixty quadrats of 2 × 2 m2 along 10 transects were set up to collect data on site characteristics and vegetation status. The relationships between community
composition and structure, species diversity, and tourism disturbance and topographic variables were analyzed by multivariate
methods (TWINSPAN and CCA). The results showed that eight meadow communities were identified by TWINSPAN. Most of them were
seriously degraded. The first CCA axis identified an elevation and tourism disturbance intensity gradient, which illustrated
that tourism disturbance and elevation were most important factors influencing meadow types, composition and structure. Some
resistant species and response species to tourism disturbance were identified and can be used as indicator species of tourism
disturbance. Species richness, heterogeneity and evenness were closely related to tourism disturbance and elevation. It is
concluded that tourism disturbance must be controlled to enable grassland rehabilitation to occur in the meadows. Measures
of effective management of the meadows were discussed. 相似文献
993.
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995.
系统采集典型汞污染地区(铅锌冶炼、金矿冶炼和燃煤电厂)食物样品(大米、蔬菜和鱼肉) 409个,测定其总汞含量以评估当地居民食物摄入汞暴露的健康风险。结果显示:铅锌冶炼地区大米总汞含量的几何均值为5.99μg·kg~(-1)(3.02~30.7μg·kg~(-1)),仅有1个样品总汞含量超过我国大米汞限量标准(20μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为0.646~5.44μg·kg~(-1)和1.80~26.4μg·kg~(-1),均未超过我国食品汞限量标准;金矿冶炼地区大米总汞含量的几何均值为4.46μg·kg~(-1)(3.13~8.67μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为0.760~7.83μg·kg~(-1)和1.59~21.9μg·kg~(-1),所有食物均未超过我国食品汞限量标准;燃煤电厂地区大米总汞含量的几何均值为3.63μg·kg~(-1)(1.05~11.4μg·kg~(-1)),蔬菜和鱼肉总汞含量分别为1.12~3.78μg·kg~(-1)和2.24~12.3μg·kg~(-1),所有食物均未超过我国食品汞限量标准。铅锌冶炼、金矿冶炼和燃煤电厂3个地区居民通过食用食物(大米、鱼肉和蔬菜途径)总汞摄入量的均值分别为0.068、0.038和0.031μg·d~(-1)·kg~(-1),均未超出联合国粮农组织和世界卫生组织食品添加剂联合专家委员会(JECFA)推荐的人体安全总汞摄入量0.71μg·d~(-1)·kg~(-1);表明3个研究地区居民汞暴露的风险较低。大米汞摄入量占3个地区居民食物总汞摄入量的比例分别为77.2%、70.8%和71.4%,食用大米是当地居民汞暴露的主要途径。 相似文献
996.
Yao Zhang Yayi Wang Yuan Yan Haicheng Han Min Wu 《Frontiers of Environmental Science & Engineering》2019,13(1):7
997.
利用氧化亚铁硫杆菌(Acidithiobacillus ferrooxidans,A.f)对采自株洲霞湾港底泥中的Cu、Cd、Pb和Zn 4种重金属进行生物淋滤实验,在实验中加入丝状菌考察其对重金属去除效果的影响。结果表明,丝状菌可以有效抑制低分子量有机酸对A.f的毒害作用,促进各种重金属的去除。当加入10%(体积比)的丝状菌后,生物淋滤过程中系统pH值在5 d内降低到2以下,Fe2+在4 d内完全氧化。经过10 d的处理,Cu、Cd、Pb和Zn 4种重金属的最高去除率分别达到76.3%、92.5%、52.6%和88.5%,与不加入丝状菌的处理相比,达到最大去除率所需的时间缩短1~2 d,4种重金属中,丝状菌的加入对Pb的去除促进作用最为明显,其去除率增加1倍左右。因此,在生物淋滤处理重金属-有机物复合污染底泥工艺中接入丝状菌对处理效果有很好的促进作用。 相似文献
998.
Sardar Khan Abd El-Latif Hesham Min Qiao Shafiqur Rehman Ji-Zheng He 《Environmental science and pollution research international》2010,17(2):288-296
Background, aim, and scope
Soil contamination with heavy metals occurs as a result of both anthropogenic and natural activities. Heavy metals could have long-term hazardous impacts on the health of soil ecosystems and adverse influences on soil biological processes. Soil enzymatic activities are recognized as sensors towards any natural and anthropogenic disturbance occurring in the soil ecosystem. Similarly, microbial biomass carbon (MBC) is also considered as one of the important soil biological activities frequently influenced by heavy metal contamination. The polymerase chain reaction–denaturing gradient gel electrophoresis (DGGE) has recently been used to investigate changes in soil microbial community composition in response to environmental stresses. Soil microbial community structure and activities are difficult to elucidate using single monitoring approach; therefore, for a better insight and complete depiction of the soil microbial situation, different approaches need to be used. This study was conducted in a greenhouse for a period of 12 weeks to evaluate the changes in indigenous microbial community structure and activities in the soil amended with different application rates of Cd, Pb, and Cd/Pb mix. In a field environment, soil is contaminated with single or mixed heavy metals; so that, in this research, we used the selected metals in both single and mixed forms at different application rates and investigated their toxic effects on microbial community structure and activities, using soil enzyme assays, plate counting, and advanced molecular DGGE technique. Soil microbial activities, including acid phosphatase (ACP), urease (URE), and MBC, and microbial community structure were studied. 相似文献999.
采用苦土为沉淀剂对模拟氮磷废水和实际氮磷废水进行了脱氮除磷实验研究,探讨了苦土投加量、pH及反应时间对废水中氮磷去除率的影响。此外,对苦土处理氮磷废水的动力学进行了研究,并对苦土及反应沉淀物进行了XRD分析。结果表明,以苦土为沉淀剂,处理氨氮浓度为200 mg/L的模拟废水的最佳条件为:苦土与氨氮(NH4+-N)的质量比为25∶1,平衡时间10 min,氨氮去除率可达到93%,磷去除率达到99%。用苦土为沉淀剂处理南京某厂的实际氮磷废水(氨氮浓度为590 mg/L,磷浓度为1 630 mg/L),氨氮的去除率达到92%,磷的去除率达到99%。苦土处理氮磷废水的动力学数据符合二级动力学模型,主要以化学反应为主。处理后废水中沉淀物的XRD分析表明其主要成分为磷酸铵镁,进一步证明苦土处理氮磷废水主要以化学反应为主。 相似文献
1000.