Nitrogen and phosphorus intake by phytoplankton in the Xiamen Bay

This paper describes a time series experiment examining the nitrogen and phosphorus intake of natural phytoplankton communities by a microcosms approach.Seawater samples containing natural phytoplankton communities were collected from waters around Baozhu Islet in inner Xiamen Bay and around Qingyu Islet in the outer bay.The goal was to elucidate the relationship between phytoplankton population enhancement,the biological removal of nitrogen and phosphorus from the seawater,and the phytoplankton nitrogen an...     

The fluvial flux of particulate organic matter from the UK: the emission factor of soil erosion

Soil erosion has been identified as a potential global carbon sink since eroded organic matter is replaced at source and eroded material is readily buried. However, this argument has relied on poor estimates of the total fate of in‐transit particulates and could erroneously imply soil erosion could be encouraged to generate carbon stores. These previous estimates have not considered that organic matter can also be released to the atmosphere as a range of greenhouse gases, not only carbon dioxide (CO₂), but also the more powerful greenhouse gases methane (CH₄) and nitrous oxide (N₂O). As soil carbon lost by erosion is only replaced by uptake of CO₂, this could represent a considerable imbalance in greenhouse gas warming potential, even if it is not significant in terms of overall carbon flux. This work therefore considers the flux of particulate organic matter through UK rivers with respect to both carbon fluxes and greenhouse gas emissions. The results show that, although emissions to the atmosphere are dominated by CO₂, there are also considerable fluxes of CH₄ and N₂O. The results suggest that soil erosion is a net source of greenhouse gases with median emission factors of 5.5, 4.4 and 0.3 tonnes CO_2eq/yr for one tonne of fluvial carbon, gross carbon erosion and gross soil erosion, respectively. This study concludes that gross soil erosion would therefore only be a net sink of both carbon and greenhouse gases if all the following criteria are met: the gross soil erosion rate were very low (<91 tonnes/km²/yr); the eroded carbon were completely replaced by new soil organic matter; and if less than half of the gross erosion made it into the stream network. By establishing the emission factor for soil erosion, it becomes possible to properly account for the benefits of good soil management in minimizing losses of greenhouse gases to the atmosphere as a by‐product of soil erosion. Copyright © 2015 John Wiley & Sons, Ltd.     

黄河冲积扇平原浅层地下水中氮循环对砷迁移富集的影响

黄河冲积扇平原浅层地下水砷含量超标情况严重,豫北平原的主体是黄河冲洪积扇平原.全面了解豫北平原浅层地下水氮循环驱动下砷的富集模式,对地下水资源的可持续利用和居民健康至关重要.本文采集豫北平原513组浅层地下水样品,采用原子荧光光谱法测定砷含量,原子吸收光谱和离子色谱等方法进行全分析及微量元素分析,对该地区高砷地下水的水...     

再力花/菖蒲生物湿地床去除河水中氮磷的试验

采用再力花和菖蒲构建湿地床,以考察其对污染河水的净化效果。6个月的连续试验表明:在水力负荷为0.24 m3/(m2.d)、植物种植密度大于158株/m2的条件下,2种植物存活率均大于93%,说明植物能适应低污染负荷、高种植密度的无土培养环境;再力花和菖蒲湿地床月均去除率分别为:总氮(TN),48.22%～78.53%和43.23%～72.42%;总磷(TP),77.62%～85.67%和58.07%～80.77%。再力花湿地床对TN、TP的净化效果好于菖蒲湿地床;2种植物吸收N、P含量分别占去除总量的比例:N为44.14%、37.75%,P为73.43%、62.05%。湿地床技术可有效去除来水中的TN、TP,通过植物吸收作用累积N、P含量较高,不同种类的植物构建湿地床对污染河水中N、P去除效果存在显著差异,且硝化反硝化和植物吸收是去除N的主要途径,而植物吸收是去除P的有效手段。     

太湖春季浮游植物群落对不同形态氮的吸收

为研究太湖春季浮游植物群落氮吸收特征及其与浮游植物群落结构和环境因子的关系,于2010年5月中旬采集太湖6个点位水样,利用15N稳定同位素示踪技术,测定太湖浮游植物群落对硝态氮,铵态氮和尿素的吸收,结果表明:太湖浮游植物群落对铵态氮的吸收速率均值最高,占几种氮总吸收量p(DN)的62.8%,各点位值在0.181 -1....     

江西鄱阳湖地区土壤酸化与人为源氮的关系

江西鄱阳湖地区是我国土壤酸化严重的地区之一,对比研究区多目标区域地球化学调查与第二次土壤普查资料发现,研究区土壤酸化趋势严重,强酸性土壤占研究区面积比例由58.22%上升到78.44%;赣江、抚河水系入湖区和饶河流域表层土壤酸化明显。研究区因施肥、大气干湿沉降和灌溉输入到农田的氮素分别为123.84 kg.hm-.2a-1、74.13 kg.hm-.2a-1、11.02 kg.hm-.2a-1。研究区因人为氮带入农田的H+为18.67 kmol.hm-.2a-1。化肥氮是引起土壤酸化的主控因素,氮沉降也是影响土壤酸化的主要因素之一。土壤pH与氮含量呈较差负相关,说明土壤中的有机氮对土壤酸化作用有限,增施有机肥和复合肥,适当减少氮肥,特别是铵态氮肥的比例,可以补充盐基物质的相对不足,达到缓解土壤酸化的作用。土壤pH与钙含量呈极显著正相关,适量增施含钙物质可以有效地防止表层土壤酸度降低。     

扎龙湿地芦苇沼泽对农田排水中氮、磷净化效果的模拟研究

农田排水已经成为扎龙湿地水环境污染的重要来源之一.采集扎龙湿地芦苇(Phragmites australis)沼泽区土壤和植物样品,开展为期18天的室内模拟试验,以进水中氨氮(NH4+-N)含量为基准,设计了6组实验,研究芦苇沼泽对不同氮、磷含量农田排水中主要污染物的去除效果,及进水在沼泽中的不同停留时间对湿地去污效果...     

Nitrogen uptake and primary productivity rates in the Mid-Atlantic Bight (MAB)

Nutrient concentrations, primary productivity, and nitrogen uptake rates were measured in coastal waters of the Mid-Atlantic Bight over a two-year period that included measurements from all four seasons. In order to assess carbon productivity and nitrogen demand within the context of the physical environment, the region was divided into three distinct hydrographic regimes: the Chesapeake and Delaware Bay outflow plumes (PL), the southern Mid-Atlantic shelf influenced by the Gulf Stream (SS), and the mid-shelf area to the north of the Chesapeake Bay mouth (MS). Annual areal rates of total nitrogen (N) uptake were similar across all regions (10.9 ± 2.1 mol N m⁻² y⁻¹). However, annual areal rates of net primary productivity were higher in the outflow plume region (43 mol C m⁻² y⁻¹), than along the Mid-Atlantic shelf and in areas influenced by the Gulf Stream (41 and 34 mol C m⁻² y⁻¹, respectively). Rates of net primary productivity were not well correlated with Chl a concentrations and were uncoupled with net N uptake rates. Seasonally averaged annual areal rates of net primary productivity for the Mid-Atlantic Bight measured in this study were higher than those calculated in previous decades and provide important validation information for biogeochemical models and satellite remote sensing algorithms developed for the region.     

Harmful algal blooms and eutrophication: ��strategies�� for nutrient uptake and growth outside the Redfield comfort zone

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.     

Effect of nitrogen to phosphorus ratios on cell proliferation in marine micro algae

The ratio of nitrogen/phosphorus (N/P) is known to affect cell proliferation of some marine micro algae. We evaluated the effect of N/P ratios on the proliferation and succession of phytoplankton using five marine micro algae species. We used two sources of nitrogen, NH4Cl (N1) and urea (N2), and a single source of phosphorous, NaH2PO4(P). The optimal N/P ratio that differed among the five species was affected by the source of nitrogen, being as follows (N1/P, N2/P in order): Thalassiosira sp. (30/1, 20/1),...