Lidar-aided analysis of boreal forest backscatter at Ku band     

《International Journal of Applied Earth Observation and Geoinformation》2020

This paper analyzes the backscatter of the microwave signal in a boreal forest environment based on a Ku -band airborne Frequency-Modulated Continuous Waveform (FMCW) profiling radar—Tomoradar. We selected a half-managed boreal forest in the southern part of Finland for a field test. By decomposing the waveform collected by the Tomoradar, the vertical canopy structure was achieved. Based on the amplitude of the waveform, the Backscattered Energy Ratio of Canopy-to-Total (BERCT) was calculated. Meanwhile, the canopy fraction was derived from the corresponding point cloud recorded by a Velodyne VLP-16 LiDAR mounted on the same platform. Lidar-derived canopy fraction was obtained by counting the number of the first/ the strongest returns versus the total amount of returns. Qualitative and quantitative analysis of radar-derived BERCT on lidar-derived canopy fraction and canopy height are investigated. A fitted model is derived to describe the Ku-band microwave backscatter in the boreal forest to numerically analyze the proportion contributed by four factors: lidar-derived canopy fraction, radar-derived canopy height, the radar-derived distance between trees and radar sensor and other factors, from co-polarization Tomoradar measurements. The Root Mean Squared Error (RMSE) of the proposed model was 0.0958, and the coefficient of determination R2 was 0.912. The fitted model reveals that the correlation coefficient between radar-derived BERCT and lidar-derived canopy fraction is 0.84, which illustrates that lidar surface reflection explains the majority of the profiling /waveform radar response. Thus, vertical canopy structure derived from lidar can be used for the benefit of radar analysis.  相似文献   

Cover crops and precipitation influence soluble reactive phosphorus losses via tile drain discharge in an agricultural watershed     

Matt T. Trentman  Jennifer L. Tank  Todd V. Royer  Shannon L. Speir  Ursula H. Mahl  Lienne R. Sethna 《水文研究》2020,34(23):4446-4458

Subsurface tile drainage speeds water removal from agricultural fields that are historically prone to flooding. While managed drainage systems improve crop yields, they can also contribute tothe eutrophication of downstream ecosystems, as tile-drained systems are conduits for nutrients to adjacent waterways. The changing climate of the Midwestern US has already altered precipitation regimes which will likely continue into the future, with unknown effects on tile drain water and nutrient loss to waterways. Adding vegetative cover (i.e., as winter cover crops) is one approach that can retain water and nutrients on fields to minimize export via tile drains. In the current study, we evaluate the effect of cover crops on tile drain discharge and soluble reactive phosphorus (SRP) loads using bi-monthly measurements from 43 unique tile outlets draining fields with or without cover crops in two watersheds in northern Indiana. Using four water years of data (n = 844 measurements), we examined the role of short-term antecedent precipitation conditions and variation in soil biogeochemistry in mediating the effect of cover crops on tile drain flow and SRP loads. We observed significant effects of cover crops on both tile drain discharge and SRP loads, but these results were season and watershed specific. Cover crop effects were identified only in spring, where their presence reduced tile drain discharge in both watersheds and SRP loads in one watershed. Varying effects on SRP loads between watersheds were attributed to different soil biogeochemical characteristics, where soils with lower bioavailable P and higher P sorption capacity were less likely to have a cover crop effect. Antecedent precipitation was important in spring, and cover crop differences were still evident during periods of wet and dry antecedent precipitation conditions. Overall, we show that cover crops have the potential to significantly decrease spring tile drain P export, and these effects are resilient to a wide range of precipitation conditions.  相似文献   

波浪作用下沉积物中氮、磷释放速率的试验研究     

张严严  房文艳  许国辉  任宇鹏  许兴北 《中国海洋大学学报(自然科学版)》2020,50(4):102-110

湖泊或海湾中的沉积物吸附氮(N)、磷(P)等元素所形成的沉积层成为水体富营养化的內源。在波浪作用下,尤其是强浪作用下,沉积物中的N、P会通过内源释放作用大量进入水体中。本文在自制的U型水槽中开展实验,采用不同水头差来模拟波浪的循环荷载作用,研究了沉积层中的N、P在静置固结状态(Ⅰ)、加波未液化状态(Ⅱ)、加波液化状态(Ⅲ)下的释放规律,并给出该试验条件下的沉积物释放速率的拟合方程。试验结果表明:沉积物中总氮(TN)和溶解性总氮(TDN)的释放速率会随着水动力作用的增强而增加;总磷(TP)、溶解性总磷(TDP)和活性磷酸盐(SRP)的释放速率也随着水动力作用增强而增加,但水体中悬浮物(SS)含量过高会限制其释放速率。  相似文献   

臭氧及臭氧类高级氧化技术降解甲基对硫磷的效能          下载免费PDF全文

林存旺  许珊珊  项丰云  章小芳 《海洋开发与管理》2018,35(9):94-99

文章研究了臭氧及臭氧类高级氧化技术(AOPs-O3)在不同pH条件下降解甲基对硫磷(MP)的效能。结果表明,在pH 3~10的条件下(反应过程控制pH),单独臭氧化5min即可完全降解MP,但不同pH下化学耗氧量(COD)和有机磷的释放率差异明显。在pH为3.3,7.5和9.4的条件下单独臭氧30min后COD的去除率分别为55.17%,89.64%和93.10%,有机磷的释放率分别为16.33%,95.00%和99.99%。考虑酸性条件下可以规避碳酸盐的负面影响(特别是高浓度废水),利用O3/H2O2/Ti(IV)在pH 3.3条件下处理MP溶液,COD去除率和有机磷释放率分别达到89.64%和81.57%。相对法计算求得MP与O3和羟基自由基(·OH)的速率常数分别为31.98L·(mol·s)-1和7.488×109 L·(mol·s)-1。活性污泥法的测试结果表明,MP经O3/Ti(IV)/H2O2(pH=3.3)和O3(pH=9.4)可提升含MP废水的可生化性,但与培养液体系相比仍具有一定的毒性。  相似文献   

Nine thousand years of upper montane soil/vegetation dynamics from the summit of Caratuva Peak,Southern Brazil     

《Journal of South American Earth Sciences》2014

Biodiversity loss, climate change, and increased freshwater consumption are some of the main environmental problems on Earth. Mountain ecosystems can reduce these threats by providing several positive influences, such as the maintenance of biodiversity, water regulation, and carbon storage, amongst others. The knowledge of the history of these environments and their response to climate change is very important for management, conservation, and environmental monitoring programs. The genesis of the soil organic matter of the current upper montane vegetation remains unclear and seems to be quite variable depending on location. Some upper montane sites in the very extensive coastal Sea Mountain Range present considerable organic matter from the late Pleistocene and other from only the Holocene. Our study was carried out on three soil profiles (two cores in grassland and one in forest) on the Caratuva Peak of the Serra do Ibitiraquire (a sub-range of Sea Mountain Range – Serra do Mar) in Southern Brazil. The δ¹³C isotopic analyses of organic matter in soil horizons were conducted to detect whether C₃ or C₄ plants dominated the past communities. Complementarily, we performed a pollen analysis and ¹⁴C dating of the humin fraction to obtain the age of the studied horizons. Except for a short and probably drier period (between 6000 and 4500 cal yr BP), C₃ plants, including ombrophilous grasses and trees, have dominated the highlands of the Caratuva Peak (Pico Caratuva), as well as the other uppermost summits of the Serra do Ibitiraquire, since around 9000 cal yr BP. The Caratuva region represents a landscape of high altitude grasslands (campos de altitude altomontanos or campos altomontanos) and upper montane rain/cloud forests with soils that most likely contain some organic matter from the late Pleistocene, as has been reported in Southern and Southeastern Brazil for other sites. However, our results indicate that the studied deposits (near the summit) are from the early to late Holocene, when somewhat wetter and warmer conditions (since around 9000 cal yr BP) enabled a stronger colonization of the ridge of Pico Caratuva by mainly C₃ plants, especially grassland species. However, at the same time, even near the summit, the soil core from the forest site already presented the current physiognomy (or a shrubby/elfin or successional forest), indicating that the colonization of the neighboring uppermost saddles and valleys were probably populated mainly by upper montane forest species.  相似文献   

气相色谱法测试土壤中分段石油烃的标准化定量方法初探   总被引：2，自引：1，他引：1  

刘玉龙  黄燕高  刘菲 《岩矿测试》2019,38(1):102-111

目前土壤样品中分段石油烃的分析方法中石油烃包括的碳原子数范围和采用的校准物质不统一,造成不同实验室的量值不具有可比性。为保证不同实验室之间结果的可比性,本文尝试建立一种石油烃相邻碳原子数标准化定量方法。该方法主要包括:(1)规定了石油烃包括的碳原子数范围为气相色谱峰中正己烷和正四十碳烷之间所有的烃(含正己烷);(2)总石油烃(TPH)分为挥发性石油烃(VPH)和半挥发性石油烃(SPH),分别选取碳原子数为6～10的5个正构烷烃作为VPH校准物质,选取碳原子数为10～40的31个正构烷烃作为SPH校准物质。采用平均响应因子法或一次线性回归法,建立校准物质的峰面积-浓度的校准关系;(3)采用相邻峰标准化校准方法,逐一定量所有的目标色谱峰;(4)计算正构烷烃含量、总石油烃含量和任意分段的石油烃含量。该方法为环境样品中石油烃分析方法的标准化建设提供了数据基础。  相似文献   

金活动态提取剂提取-电感耦合等离子体质谱法测定深穿透地球化学样品中的金     

王冀艳  胡家祯  丁汉铎  曹立峰  张明炜  张帆  黄杰  姚文生 《岩矿测试》2020,39(4):525-534

金的地球化学勘查基于金的准确测定,地球化学样品中金含量通常处于ng/g水平,需先进行分离富集,再采用电感耦合等离子体质谱法(ICP-MS)或石墨炉原子吸收光谱法(GFAAS)进行测定。当前,隐伏矿床勘查是地球化学探测技术的发展前沿,金活动态提取技术是寻找隐伏金矿的有效手段之一。相比于全量分析,金的活动态含量更低,需要解决选择性提取、高效预富集与准确测定等一系列难题。本文采用柠檬酸铵与土壤中黏土矿物及次生矿物作用促使吸附和可交换组分的金进入提取液,以硫脲和硫代硫酸钠络合金使活动态金向提取液中扩散,达到选择性提取的目的,建立了提取液中金的预富集及ICP-MS测定方法。实验确定的分析条件为:采用5g/L柠檬酸铵-2g/L硫脲-5g/L硫代硫酸钠为提取剂,提取时间24h,在酸性硫脲介质下用活性炭富集金,金吸附率可达89.6%～109.2%,灰化解吸温度为650～700℃。本方法检出限为0.05ng/g,相对标准偏差(RSD)为9.4%～10.2%,加标回收率为91.2%～93.4%。与已报道的硫酸铁-硫脲-硫代硫酸钠溶液提取再GFAAS测定的方法相比,本方法具有检出限低、测试线性范围宽、测试速度快的优势;应用于森林覆盖区黑龙江东安金矿区地球化学探测试验,金活动态异常与隐伏金矿位置一致。  相似文献   

微小亚历山大藻(Alexandrium minutum)的氮磷吸收、生长、产毒动态变化     

俞群娣  王亚军  余新威  刘寅政  李叶  方力  陈成吉  罗红宇 《海洋与湖沼》2018,49(2):346-351

采用浮游植物计数法、高效液相色谱串联质谱法、分光光度法等分析方法,探索了微小亚历山大藻(Alexandrium minutum)在批次培养过程中氮磷吸收、产毒、生物量、p H等参数的动态变化关系。结果表明,微小亚历山大藻对磷的吸收迅速,可以将磷储存于体内,待生长使用。该藻对氮的吸收相对缓慢,环境中氮缺乏时,产毒量不再增加,说明氮对产毒有着重要的调控作用。在第二对数期中出现了碳限制环境,导致叶绿素a在碳限制条件下无法表征藻的生物量,相反,叶绿素a和生物量呈负线性关系,可能是叶绿素转化成其它含碳物质,用于生长。毒素不仅存在于细胞体内,培养液中(胞外)也含有毒素,并且胞外毒素从稳定期开始逐渐升高。胞内毒素的组成中GTX1/4占据绝对优势,GTX2/3含量相对较少。生长延缓期和第一对数期,各种毒素组成比例相对稳定,而在随后的生长期内,GTX1/4在总毒素中的占比逐渐上升,GTX2/3占比逐渐下降,表明微小亚历山大藻毒素组成会随着生长周期的变化而发生变化。  相似文献   

Influence of land use on the persistence effect of riverine phosphorus          下载免费PDF全文

Dingjiang Chen  Fang Xia  Xu Shang  YuanYuan Liu  Randy A. Dahlgren  Kun Mei 《水文研究》2018,32(1):118-125

The persistence effect contribution of legacy nutrients is often cited as a reason for little or no improvement in water quality following extensive implementation of watershed nutrient mitigation actions, yet there is limited knowledge concerning factors influencing this response, often called the “persistence effect.” Here, we adopted detrended fluctuation analysis and Spearman analysis methods to assess the influence of land use on the watershed phosphorus (P) persistence effect, using monthly water quality records during 2010–2016 in 13 catchments within a drinking water reservoir watershed in eastern China. Detrended fluctuation analysis was used to calculate the Hurst exponent α to assess watershed legacy P characteristics (α  ≈ 0.5, α  > 0.5, and α  < 0.5 indicate white noise, persistence, and anti‐persistence, respectively). Results showed weak to strong P persistence (0.60–0.81) in the time series of riverine P in the 13 catchments. The Hurst exponent α had negative relationships with agricultural land (R = ?.47, p = .11) and developed land (R = ?.67, p = .01) and a positive relationship with forest land cover (R = .48, p = .10). The persistence effect of riverine P was mainly determined by retention ability (biogeochemical legacy) and migration efficiency (hydrological legacy). A catchment with strong retention capacity (e.g., biomass uptake/storage and soil PO₄ sorption) and low migration efficiency results in a stronger persistence effect for riverine P. In practice, source control is more effective in catchments with weak persistence, whereas sink control (e.g., riparian buffers and wetlands) is preferred in catchments with strong persistence effects.  相似文献   

硫铝酸盐水泥去除微污染水体中磷的性能及机理     

杨蕤  刘国  黄艳采  张琪琪  徐芬  廖兵  刘静 《湖泊科学》2022,34(3):828-842

微污染湖泊、水库等水体中磷的去除已成为水质研究的主要方向.磷是造成水体富营养化的关键因素,其浓度较低时即可导致水体富营养化与水华的发生,许多除磷方法对低浓度磷的去除效果不佳.因此,我们从22种天然矿物、火山灰质材料和水硬性材料中,筛选出了能高效去除低浓度磷的硫铝酸盐水泥（代号R.SAC 42.5,简称R）,该材料在中性、偏酸性的溶液中呈絮凝体状态.本文从吸附动力学、等温吸附曲线、SEM和XRD分析3个方面研究了R对微污染水体中磷的去除机理、环境因素（pH、温度、光照、扰动和溶解氧浓度）对已被R絮凝体吸附的磷酸盐再次溶出的影响以及R在实际微污染水体中的应用效果.结果表明,中性条件下,R絮凝体在0.5 min内就可完成对磷酸盐的去除.当R絮凝体用量为0.10 g/L时,可将0.10 mg/L的磷酸盐完全去除.初步分析表明,磷的去除是由于R絮凝体与磷酸盐之间的化学吸附作用,吸附初始反应阶段可由Langmuir等温线描述.SEM和XRD分析表明磷酸盐主要吸附在R中的硅酸三钙表面,絮凝后的R通过溶液中离子的网捕、压缩、沉降增加了磷酸盐吸附量.环境因子实验表明,在pH为5.0~8.0范围内,磷酸盐去除率可达90%以上.光、温度和溶解氧不影响磷酸盐的去除.扰动会导致部分磷酸盐解吸,但磷酸盐浓度仍低于0.05 mg/L.对微污染湖泊/水库除磷研究表明,絮凝后的R在湖泊/水库除磷、截留水中悬浮物、预防水体富营养化与水华方面具有潜在的应用前景.  相似文献