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321.
F. Stagnitti G. Allinson J. Sherwood M. Graymore M. Allinson N. Turoczy 《毒物与环境化学》2013,95(3-4):415-425
This paper investigates leaching of water and nutrients (NO‐ 3, Cl‐, PO3‐ 4) from the unsaturated layer in an Australian soil using a multisegment percolation system (MPS). Large undisturbed soil cores were collected from a clay‐based, basaltic plain, agricultural soil at Grassmere, 300 km west of Melbourne, Australia. Significant heterogeneity (or preferential flow) of effluent moisture and solutes was detected (one‐way ANO VA, p < 0.001). Fifty percent of the applied nitrate and chloride leached from the soil core within three days after initial application. Hundred percent of the applied nitrate and chloride leached from the soil core within 8 days after application. These results indicate little incorporation into the soil matrix, and possible denitrification or mineralisation. In contrast, after 18 days, less than 1 % of the total applied phosphates leached from the soil, indicating strong adsorption. Our experiments indicate considerable heterogeneity in water flow patterns and solute leaching on a small spatial scale. Very rapid transport of nitrate and chloride through the soil was evident, in comparison phosphate leaching was negligible. These results have important implications for the management of nutrient schedules in agricultural soils, particularly those located in the Western District of Victoria, Australia. 相似文献
322.
Changes in nitrification rates of an acid grassland soil with and without air drying have been monitored over 9 days, after first flushing native nitrate from the soils with deionised water. The results confirmed that full re-establishment of nitrification after air drying takes several days, supporting the hypothesis that any immediate first flush of nitrate from air-dried soils originates from cell lysis or flushing of ‘stored’ nitrate. Ammonium spiking confirmed that nitrification was not ammonium substrate limited. It was also found that ammonium accumulates in the soil during the drying process, providing a substrate pool once the population of nitrifiers has re-established. Over the first week of incubation, nitrate immobilisation was less conspicuous in the soil that had been rewetted after air drying compared with the incubated field moist soil. 相似文献
323.
An experiment has been conducted to contrast the effects of enhanced oxidised and reduced nitrogen deposition upon key chemical parameters in a Calluna moorland podzol. A 40 cm deep podzol profile, derived from granite, was reconstructed in one hundred 4.2 cm diameter cores. for 20 weeks, the cores were subjected twice weekly to simulated rainfall containing either twice ambient nitrogen deposition in Aberdeen, or further enhanced nitrogen (further 2- and 6-fold increases) as nitric acid or ammonium sulphate. to quantify the dynamics of soil change in each horizon, randomly selected cores were destructively analysed every two weeks and the soils analysed. Increased nitrogen inputs, regardless of form, substantially and immediately reduced surface soil pHwater via the mobile anion or salt effect. for the higher nitrogen treatments, the pH reduction was seen throughout the profile. Longer term soil acidification was also seen in the pHcalcium chloride results over the 20 weeks. at a given nitrogen deposition rate, the effects of ammonium sulphate and nitric acid on soil pHcalcium chloride were similar. the ammonium sulphate treatments were especially effective at reducing base saturation throughout much of the profile, the direct base cation leaching being associated with substantial ammonium accumulation. the results suggest that the direct base cation leaching caused by ammonium deposition needs to be considered when assessing atmospheric pollution “damage” to heathland soils. 相似文献
324.
Vegetables are the major source of nitrates and nitrites in human diet. Because of the potential of health hazards resulting from high intake of nitrates and nitrites, the assessment of these components in vegetables was undertaken in this study. The concentration of nitrates and nitrites in carrots and onions sampled from three central cities of Mazandaran state (Iran) was determined in 12 samples of each vegetable collected from farmlands of four geographical regions in each city using the ISO Method (NO. 6635). The average content of nitrates and nitrites in all of the samples was less than standard threshold limits. Babol-sampled carrot had significantly higher nitrate content than two other cities. On the other hand, onions which were sampled from Sari showed significantly higher content of nitrate than two other cities. Based upon the maximum levels that were specified by European Commission Regulation, data showed that the investigated vegetables were safe for consumption. 相似文献
325.
山东省地下水硝酸盐溯源研究 总被引:2,自引:0,他引:2
针对山东全省农村地区进行地下水取样,采用离子交换色层法对地下水NO3--N质量浓度大于10 mg·L-1的地下水样品进行预处理,做溯源研究,同时采集当地植物、化学肥料、人畜粪便、土壤等样品,测定δ15N值,以针对山东地区,对现存的δ15N值数据库进行完善与补充,使本研究更具代表性与准确性。研究结果表明,如以研究区域整体为单位,有35.45%地下水样品的NO3--N来自于粪肥污染,有27.1%的地下水样品是受化肥污染,还有37.45%的地下水样品的NO3--N污染来自于化肥、粪肥以及生活污水的混合污染。作者还进一步分析了地下水中NO3--N平均质量浓度高于20 mg·L-1的烟台和潍坊,结果表明,烟台地区的地下水NO3--N污染有55.56%来自于粪肥污染,有5.56%来自于化肥污染,有38.88%来自于化肥、粪肥以及生活污水的混合污染;潍坊地区的地下水NO3--N污染有16.13%来自于粪肥污染,有48.39%来自于化肥污染,还有35.48%来自于化肥、粪肥以及生活污水的混合污染。 相似文献
326.
针对富氧地下水中硝酸盐,采用粒状铁和甲醇支持的生物-化学联用法开展了批实验研究,优化了脱氮反应参数,初步探讨了脱氧脱氮的能力及途径。结果表明,该法的优化参数是粒状铁种类为GI-北京,m(粒状铁)∶m(水)为3∶800,粒状铁粒径为0.425~1.0 mm,反应时间为5 d,甲醇用量为210.59 mg.L-1。生物-化学法、粒状铁和好氧异养菌完全脱氧所需的时间分别是174、206和2 746 min。生物-化学法脱氧依赖于粒状铁化学还原和好氧异养菌有氧呼吸,并且前者起着关键作用。随着反应时间的增加,异养脱氮、自养脱氮和化学还原各自引起的NO3-去除率亦增加。当反应时间≤5 d时,自养脱氮和化学还原的去除率均〈10%,而当反应时间为5 d时,生物-化学法的NO3-去除率达到近100%。生物-化学法内存在异养脱氮、自养脱氮和化学还原3种脱氮途径,其中异养脱氮是最主要的途径,且三者存在共生、协同和促进作用。生物-化学法脱氮期间硝酸盐还原速率≥亚硝酸盐还原速率。生物-化学法去除地下水中硝酸盐是有效可行的。 相似文献
327.
328.
Submicron aerosol is of extensive concern not only due to its significant impact on air quality but also because it is detrimental to human health. In this study, we investigated the characteristics, sources and chemical processes of submicron aerosol based on realtime online measurements of submicron aerosols(NR-PM 1) during December 2015 at an urban site in Beijing. The average mass concentration of NR-PM 1 was 92.5 ±84.9 μg/m3, the hourly maximum was 459.1 μg/m3 during t... 相似文献
329.
Guoliang Zhang Liang Zhang Xiaoyu Han Shujun Zhang Yongzhen Peng 《Frontiers of Environmental Science & Engineering》2021,15(2):32
330.
太湖春夏两季反硝化与厌氧氨氧化速率的空间差异及其影响因素 总被引:3,自引:2,他引:1
反硝化和厌氧氨氧化是湖泊的重要脱氮过程,对维持湖泊氮素平衡具有重要意义.为了解大型富营养化浅水湖泊——太湖反硝化和厌氧氨氧化速率的时空变化及其影响因素,于2020年春季和夏季选择太湖的梅梁湾、贡湖湾、竺山湾、大浦口、胥口湾和湖心区采集无扰动泥柱,利用15N同位素示踪技术,在恒温水浴条件下开展反硝化和厌氧氨氧化流动培养实验.结果表明,春季太湖不同湖区反硝化和厌氧氨氧化速率的空间分布差异较大,反硝化速率为(27.74±8.45)~(142.43±35.54)μmol·(m2·h)-1,厌氧氨氧化速率为(2.35±1.06)~(17.95±8.66)μmol·(m2·h)-1,厌氧氨氧化对脱氮的贡献率相对较低,为(7.82±1.71)%~(11.20±1.53)%.夏季竺山湾脱氮速率最高,反硝化和厌氧氨氧化速率分别高达(165.68±62.14)μmol·(m2·h)-1和(33.56±10.66)μmol·(m2·h)-1,厌氧氨氧化对脱氮贡献率达到了(16.85±1.78)%,其他湖区的脱氮速率相对较低,且没有十分显著的空间差异,反硝化和厌氧氨氧化速率分别为(25.47±10.46)~(42.50±16.46)和(2.65±0.94)~(5.95±2.65)μmol·(m2·h)-1,厌氧氨氧化对脱氮的贡献率为(13.62±1.95)%~(7.24±1.78)%.总体来说,夏季反硝化速率要普遍低于春季,而厌氧氨氧化速率相对于春季并无明显下降.统计分析表明,反硝化和厌氧氨氧化速率与底物氮浓度呈显著的相关性(P<0.01),说明氮浓度是不同湖区脱氮速率差异的主要控制因素.此外,厌氧氨氧化对脱氮的贡献率与叶绿素a的浓度呈现显著的正相关性(P<0.05),说明蓝藻水华对厌氧氨氧化脱氮贡献率的变化有很大的影响,具体的影响机制还有待进一步研究. 相似文献