Field-scale modelling of carbon and nitrogen dynamics in soils amended with urban waste composts

Composting has emerged as a valuable route for the disposal of urban waste, with the prospect of applying composts on arable fields as organic amendments. Proper management of urban waste composts (UWC) requires a capacity to predict their impacts on carbon and nitrogen dynamics in the field, an issue in which simulation models are expected to play a prominent role.Here, we used a deterministic soil-crop model to simulate C–N dynamics in an arable field amended with three types of UWC (green waste and sludge, biodegradable waste, and solid waste), and a reference amendment (farmyard manure). The model is a version of CERES in which the soil C–N module was substituted with the NCSOIL model, whose microbiological parameters were determined from either laboratory incubation data or biochemical fractionation in a previous paper. CERES was tested against data from a field trial set up in 1998 in the Paris area, and managed as a maize (Zea mays L.)–wheat (Triticum aestivum L.) rotation. Comparison of observed and simulated data over the first 4 years of the field trial showed that CERES predicted the soil moisture and inorganic N dynamics reasonably well, as well as the variations in soil organic C. In particular, the parameterization of UWC organic matter from biochemical fractions achieved a similar fit as the parameterization based on incubation data. Wheat yields were also correctly predicted, but a systematic under-estimation of maize yields pointed at an under-estimation of spring and summer mineralization of N by CERES.Simulated N fluxes showed that the organic amendments induced an additional leaching ranging from 1 to 8 kg N ha⁻¹ yr⁻¹, which can be related to the initial mineral N content of the amendments. After 4 years, the composts had mineralized 3–8% of their initial organic N content, depending on their stability. Composts with slower N release had higher N availability for the crops. CERES could thus be used to aid in selecting the timing of compost application, in relation to its stability, based on both environmental and agronomical criteria.     

High-resolution inventory of NO emissions from agricultural soils over the Ile-de-France region

Arable soils are a significant source of nitric oxide (NO), a precursor of tropospheric ozone, and thereby contribute to ozone pollution. However, their actual impact on ozone formation is strongly related to their spatial and temporal emission patterns, which warrant high-resolution estimates.Here, we combined an agro-ecosystem model and geo-referenced databases to map these sources over the 12 000 km² administrative region surrounding Paris, France, with a kilometric level resolution. The six most frequent arable crop species were simulated, with emission rates ranging from 1.4 kg N-NO ha⁻¹ yr⁻¹ to 11.1 kg N-NO ha⁻¹ yr⁻¹. The overall emission factor for fertilizer-derived NO emissions was 1.7%, while background emissions contributed half of the total NO efflux. Emissions were strongly seasonal, being highest in spring due to fertilizer inputs. They were mostly sensitive to soil type, crops' growing season and fertilizer N rates.     

新疆地区气溶胶对地表太阳辐射的影响初探

为了进一步认识大气气溶胶对气候环境的影响,基于2017年Aqua MODIS C006气溶胶光学厚度（aerosol optical depth,AOD）产品、CERES SSF Aqua MODIS Edition 4A数据集的地表短波辐射以及地面观测太阳辐射数据,对2017年新疆地区AOD和地表太阳辐射年变化进行研究,并以沙尘和人类活动气溶胶丰富的南疆典型地区喀什为代表城市,采用AccuRT辐射传输模式定量化研究晴空时气溶胶对地表短波辐射的影响.结果表明：①地表太阳辐射月均值最大值出现在和田站的5月,为441.62 W·m^-2,最小值出现在乌鲁木齐站点的12月,为37.03 W·m^-2;CERES/SSF地表短波辐射资料与地面观测结果相比,阿克苏站、焉耆站和伊宁站的差距最小,喀什站和若羌站全年存在高估现象,其他站点存在不同程度的高低估现象.②2017年新疆地区AOD格点平均的年均值最小值为0.0175,最大值为0.4610,南疆地区的AOD整体高于北疆地区;2017年AOD格点春夏季的AOD均值分布与全年均值分布特征相似,其中春季的AOD高值区区域面积高于其他季节.③根据AccuRT计算,当AOD由0.05增加为0.56时,四季的地表向下短波总辐射均呈下降趋势,夏季下降幅度最大,由923.02 W·m^-2变化为677.61 W·m^-2,其次为春季和秋季,冬季下降幅度最小.AOD的减少变化导致的地表向下短波总辐射通量、直射辐射通量和散射辐射通量变化敏感度明显高于AOD增加所导致的变化敏感度.     

1983～2012年长江流域地表净辐射变化特征

本文采用统计相关分析、Morlet小波分析、Rodionov时间序列分析与GIS空间分析等技术方法,分析了1983年7月至2012年9月长江流域SRB和CERES地表净辐射月产品的时空变化特征.结果表明:拟合后遥感产品比气象辐射站点观测值整体高15.8％,平均误差为15.31 W/m2,均方根误差为21.58W/m2.长江流域地表净辐射多年均值为78.0W/m2,整体呈下降趋势,于1996年突降,存在16年和10年周期;季相上,呈夏＞春＞秋＞冬.空间上,呈现西部地区＞东部地区＞中部地区;1996～2012年相较1983～1995年净辐射整体下降,其中上游流域降幅大于中下游;净辐射降低主要出现在5～7月,降幅较大地区主要是长江上游流域部分地区和长江中游流域纬度较低地区.研究结果对于认识长江流域的气候变化条件下的能量和水分循环过程等具有重要意义.     

黄土高原地区小麦生产潜力模拟研究

分析了作物生产潜力常规研究方法的不足,探讨了作物生长模型模拟方法的优势,在模型验证和气象、土壤和作物数据库组建的基础上,应用DSSAT3中的CERES小麦模型模拟研究了黄土高原地区28个代表点冬小麦和春小麦的光温生产潜力和气候生产潜力,统计计算了各点小麦产量潜力多年平均值、标准差、最高值和最低值,分析了潜力值年际变异与地区分布差异,并计算了小麦的水分满足率。黄土高原冬小麦光温生产潜力、气候生产潜力和水分满足率分别为7970～8647kg/hm²、2219～7545kg/hm²和0.278～0.872,春小麦分别为7436～9127kg/hm²、0～7598kg/hm²和0.192～0.961。     

Estimating bulk optical properties of aerosols over the western North Pacific by using MODIS and CERES measurements

Over the western North Pacific, a large amount of land aerosols from Asian-Pacific countries is transported by the prevailing westerlies. This transport makes the radiative characteristics of these aerosols diverse, particularly when one compares those characteristics over the coastal sea with those over the open sea. In this paper we discuss a method that uses satellite data to obtain the single-scattering albedo (ω) and asymmetry factor (g) of atmospheric aerosols for two large-scale subdivisions—the coastal sea (within 250 km from the coast) and the open sea (the remaining area)—over the western North Pacific (110°E–180°, 20°N–50°N). Our estimation method uses satellite measurements, obtained over a six-year period (2000–2005), of aerosol optical depth (AOD) and shortwave fluxes at both the surface and the top of the atmosphere (TOA); the measurements are obtained using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Clouds and the Earth's Radiant Energy System (CERES). For the two subdivisions, the estimated annual means of (ω,g) at 630 nm are significantly different: (0.94, 0.65) over the coastal sea and (0.97, 0.70) over the open sea. From a quantitative viewpoint, this result indicates that in comparison with aerosols over the open sea, those over the coastal sea show greater absorption and lesser forward scattering of solar radiation. The estimated optical properties are responsible for the aerosol surface cooling observed by MODIS and CERES, which is approximately 138 and 108 W m⁻² per AOD over the coastal sea and open sea, respectively.