Growth of continental-scale metro-agro-plexes, regional ozone pollution, and world food production

Three regions of the northern mid-latitudes, the continental-scale metro-agro-plexes, presently dominate global industrial and agricultural productivity. Although these regions cover only 23 percent of the Earth's continents, they account for most of the world's commercial energy consumption, fertilizer use, food-crop production, and food exports. They also account for more than half of the world's atmospheric nitrogen oxide (NOx,) emissions and, as a result, are prone to ground-level ozone (O(3)) pollution during the summer months. On the basis of a global simulation of atmospheric reactive nitrogen compounds, it is estimated that about 10 to 35 percent of the world's grain production may occur in parts of these regions where ozone pollution may reduce crop yields. Exposure to yield-reducing ozone pollution may triple by 2025 if rising anthropogenic NOx emissions are not abated.     

Impact of anthropogenic CO2 on the CaCO3 system in the oceans

Rising atmospheric carbon dioxide (CO2) concentrations over the past two centuries have led to greater CO2 uptake by the oceans. This acidification process has changed the saturation state of the oceans with respect to calcium carbonate (CaCO3) particles. Here we estimate the in situ CaCO3 dissolution rates for the global oceans from total alkalinity and chlorofluorocarbon data, and we also discuss the future impacts of anthropogenic CO2 on CaCO3 shell-forming species. CaCO3 dissolution rates, ranging from 0.003 to 1.2 micromoles per kilogram per year, are observed beginning near the aragonite saturation horizon. The total water column CaCO3 dissolution rate for the global oceans is approximately 0.5 +/- 0.2 petagrams of CaCO3-C per year, which is approximately 45 to 65% of the export production of CaCO3.     

Carbon Monoxide in the Earth's Atmosphere: Increasing Trend

The results of an analysis of more than 60,000 atmospheric measurements of carbon monoxide taken over 3(1/2) years at Cape Meares, Oregon (45 degrees N, 125 degrees W), indicate that the background concentration of this gas is increasing. The rate of increase, although uncertain, is about 6 percent per year on average. Human activities are the likely cause of a substantial portion of this observed increase; however, because of the short atmospheric lifetime of carbon monoxide and the relatively few years of observations, fluctuations of sources and sinks related to the natural variability of climate may have affected the observed trend. Increased carbon monoxide may deplete tropospheric hydroxyl radicals, slowing down the removal of dozens of man-made and anthropogenic trace gases and thus indirectly affecting the earth's climate and possibly the stratospheric ozone layer.     

Carbon dioxide emission from european estuaries

The partial pressure of carbon dioxide (pCO2) in surface waters and related atmospheric exchanges were measured in nine European estuaries. Averaged fluxes over the entire estuaries are usually in the range of 0.1 to 0.5 mole of CO2 per square meter per day. For wide estuaries, net daily fluxes to the atmosphere amount to several hundred tons of carbon (up to 790 tons of carbon per day in the Scheldt estuary). European estuaries emit between 30 and 60 million tons of carbon per year to the atmosphere, representing 5 to 10% of present anthropogenic CO2 emissions for Western Europe.     

Time scales in atmospheric chemistry: coupled perturbations to N2O, NOy, and O3

Nitrous oxide (N2O) is one of the top three greenhouse gases whose emissions may be brought under control through the Framework Convention on Climate Change. Current understanding of its global budget, including the balance of natural and anthropogenic sources, is largely based on the atmospheric losses calculated with chemical models. A representative one-dimensional model used here describes the photochemical coupling between N2O and stratospheric ozone (O3), which can easily be decomposed into its natural modes. The primary, longest lived mode describes most of the atmospheric perturbation due to anthropogenic N2O sources, and this pattern may be observable. The photolytic link between O3 and N2O is identified as the mechanism causing this mode to decay 10 to 15 percent more rapidly than the N2O mean atmospheric lifetime, affecting the inference of anthropogenic sources.     

Ice core records of atmospheric N2O covering the last 106,000 years

Paleoatmospheric records of trace-gas concentrations recovered from ice cores provide important sources of information on many biogeochemical cycles involving carbon, nitrogen, and oxygen. Here, we present a 106,000-year record of atmospheric nitrous oxide (N2O) along with corresponding isotopic records spanning the last 30,000 years, which together suggest minimal changes in the ratio of marine to terrestrial N2O production. During the last glacial termination, both marine and oceanic N2O emissions increased by 40 +/- 8%. We speculate that our records do not support those hypotheses that invoke enhanced export production to explain low carbon dioxide values during glacial periods.     

Enhanced open ocean storage of CO2 from shelf sea pumping

Seasonal field observations show that the North Sea, a Northern European shelf sea, is highly efficient in pumping carbon dioxide from the atmosphere to the North Atlantic Ocean. The bottom topography-controlled stratification separates production and respiration processes in the North Sea, causing a carbon dioxide increase in the subsurface layer that is ultimately exported to the North Atlantic Ocean. Globally extrapolated, the net uptake of carbon dioxide by coastal and marginal seas is about 20% of the world ocean's uptake of anthropogenic carbon dioxide, thus enhancing substantially the open ocean carbon dioxide storage.     

Nylon production: an unknown source of atmospheric nitrous oxide

Nitrous oxide in the earth's atmosphere contributes to catalytic stratospheric ozone destruction and is also a greenhouse gas component. A precise budgetary accounting of N(2)O sources has remained elusive, and there is an apparent lack of source identification. One source of N(2)O is as a by-product in the manufacture of nylon, specifically in the preparation of adipic acid. Characterization of the reaction N(2)O stoichiometry and its isotopic composition with a simulated industrial adipic acid synthesis indicates that because of high rates of global adipic acid production, this N(2)O may account for approximately 10 percent of the increase observed for atmospheric N(2)O.     

Temporal trends in deep ocean Redfield ratios

The Redfield ratio [carbon:nitrogen:phosphorus (C:N:P)] of particle flux to the deep ocean is a key factor in marine biogeochemical cycling. Changes in oceanic carbon sequestration have been linked to variations in the Redfield ratio on geological time scales, but this ratio generally is assumed to be constant with time in the modern ocean. However, deep-water Redfield ratios in the northern hemisphere show evidence for temporal trends over the past five decades. The North Atlantic Ocean exhibits a rising N:P ratio, which may be related to increased deposition of atmospheric nitrous oxides from anthropogenic N emissions. In the North Pacific Ocean, increasing C:N and C:P ratios are accompanied by rising remineralization rates, which suggests intensified export production. Stronger export of carbon in this region may be due to enhanced bioavailability of aeolian iron. These findings imply that the biological part of the marine carbon cycle currently is not in steady state.     

Atmospheric trace gases in antarctica

Trace gases have been measured, by electron-capture gas chromatography and gas chromatography-mass spectrometry techniques, at the South Pole (SP) in Antarctica and in the U.S. Pacific Northwest (PNW) ( approximately 45 degrees N) during January of each year from 1975 to 1980. These measurements show that the concentrations of CCl(3)F, CCl(2)F(2), and CH(3)CCl(3) have increased exponentially at substantial rates. The concentration of CCl(3)F increased at 12 percent per year at the SP and at 8 percent per year in the PNW; CCl(2)F(2) increased at about 9 percent per year at both locations, and CH(3)CCl(3) increased at 17 percent per year at the SP and 11.6 percent per year at the PNW site. There is some evidence that CCl(4) ( approximately 3 percent per year) and N(2)O (0.1 to 0.5 percent per year) may also have increased. Concentrations of nine other trace gases of importance in atmospheric chemistry are also being measured at these two locations. Results of the measurements of CHClF(2)(F-22), C(2)Cl(3)F(3)(F-113), SF(6), C(2)-hydrocarbons, and CH(3)Cl are reported here.     

Global carbon sinks and their variability inferred from atmospheric O2 and delta13C

Recent time-series measurements of atmospheric O2 show that the land biosphere and world oceans annually sequestered 1.4 +/- 0.8 and 2.0 +/- 0.6 gigatons of carbon, respectively, between mid-1991 and mid-1997. The rapid storage of carbon by the land biosphere from 1991 to 1997 contrasts with the 1980s, when the land biosphere was approximately neutral. Comparison with measurements of delta13CO2 implies an isotopic flux of 89 +/- 21 gigatons of carbon per mil per year, in agreement with model- and inventory-based estimates of this flux. Both the delta13C and the O2 data show significant interannual variability in carbon storage over the period of record. The general agreement of the independent estimates from O2 and delta13C is a robust signal of variable carbon uptake by both the land biosphere and the oceans.     

Europe's terrestrial biosphere absorbs 7 to 12% of European anthropogenic CO2 emissions

Most inverse atmospheric models report considerable uptake of carbon dioxide in Europe's terrestrial biosphere. In contrast, carbon stocks in terrestrial ecosystems increase at a much smaller rate, with carbon gains in forests and grassland soils almost being offset by carbon losses from cropland and peat soils. Accounting for non-carbon dioxide carbon transfers that are not detected by the atmospheric models and for carbon dioxide fluxes bypassing the ecosystem carbon stocks considerably reduces the gap between the small carbon-stock changes and the larger carbon dioxide uptake estimated by atmospheric models. The remaining difference could be because of missing components in the stock-change approach, as well as the large uncertainty in both methods. With the use of the corrected atmosphere- and land-based estimates as a dual constraint, we estimate a net carbon sink between 135 and 205 teragrams per year in Europe's terrestrial biosphere, the equivalent of 7 to 12% of the 1995 anthropogenic carbon emissions.     

Oceanic Uptake of Fossil Fuel CO2: Carbon-13 Evidence

The delta(13)C value of the dissolved inorganic carbon in the surface waters of the Pacific Ocean has decreased by about 0.4 per mil between 1970 and 1990. This decrease has resulted from the uptake of atmospheric CO(2) derived from fossil fuel combustion and deforestation. The net amounts of CO(2) taken up by the oceans and released from the biosphere between 1970 and 1990 have been determined from the changes in three measured values: the concentration of atmospheric CO(2), the delta(13)C of atmospheric CO(2) and the delta(13)C value of dissolved inorganic carbon in the ocean. The calculated average net oceanic CO(2) uptake is 2.1 gigatons of carbon per year. This amount implies that the ocean is the dominant net sink for anthropogenically produced CO(2) and that there has been no significant net CO(2) released from the biosphere during the last 20 years.     

The impact of agricultural soil erosion on the global carbon cycle

Agricultural soil erosion is thought to perturb the global carbon cycle, but estimates of its effect range from a source of 1 petagram per year(-1) to a sink of the same magnitude. By using caesium-137 and carbon inventory measurements from a large-scale survey, we found consistent evidence for an erosion-induced sink of atmospheric carbon equivalent to approximately 26% of the carbon transported by erosion. Based on this relationship, we estimated a global carbon sink of 0.12 (range 0.06 to 0.27) petagrams of carbon per year(-1) resulting from erosion in the world's agricultural landscapes. Our analysis directly challenges the view that agricultural erosion represents an important source or sink for atmospheric CO2.     

东北三省玉米生产资源投入和环境效应的时空特征

【目的】玉米的总产量在我国三大主粮作物中最高,位居世界第二位。东北三省玉米种植面积占全国的39%,而资源投入相对较低。本研究旨在明确东北三省玉米生产资源投入和环境效应的时空特征。【方法】基于生命周期评价（life cycle assessment）方法,采用适用于东北三省玉米生产的活性氮损失模型,定量化评价东北三省2007—2016年玉米生产系统的资源投入（肥料、农药和柴油等）及其相关的活性氮损失和温室气体排放等环境风险。【结果】东北三省玉米生产资源投入在时空尺度上均存在较大差异。吉林省玉米生产的平均总施肥量为400 kg·hm^-2,单产为7 065 kg·hm^-2,平均单位面积温室气体（GHG）排放量为2 965 kg CO₂ eq·hm^-2,均为三省最高,而碳、氮足迹较低,平均单位面积活性氮（Nr）损失量为中间水平且年际间变化不大。辽宁省的平均氮肥投入量为198 kg·hm^-2,Nr损失量为20.8 kg N·hm^-2,碳、氮足迹为493 kg CO₂ eq·Mg^-1和3.53 kg N·Mg^-1,均为最高。单产为5 966 kg·hm^-2,处于中等水平,GHG排放量年际间变化不大。黑龙江省平均施氮量为149 kg·hm^-2,单产水平为5 318 kg·hm^-2,Nr损失量和GHG排放量等均为三省最低,碳、氮足迹均处于中等水平。时间尺度上,2008—2015年东北三省玉米种植面积逐年增大,累积增加了5.73 Mhm²。2015年东北三省玉米产量最高,达91.2 Mt（百万吨）;2007—2016年玉米平均总产量占全国的32%,其中黑龙江省、吉林省和辽宁省分别占13.9%、11.7%和6.7%;10年平均种植面积占全国的30%,其中黑龙江省、吉林省和辽宁省分别占14.7%、9.3%和6.4%。东北三省玉米10年平均单产为6 116 kg·hm^-2,平均单产最高年份为2013年,为6 824 kg·hm^-2。2007—2016年10年间东北三省玉米生产的肥料投入整体呈上升趋势,氮肥稳中有降,磷钾肥逐年升高,2014—2016年3年肥料增长趋势大幅减缓,逐渐趋于稳定,10年间氮、磷、钾肥平均用量分别为177、101和70.2 kg·hm^-2。2007—2016年,东北玉米生产农药投入量呈现稳步上升趋势;柴油投入量前4年较为稳定,后逐渐上升。东北玉米生产10年间的平均农药用量为10.2 kg·hm^-2,平均柴油用量为94.6 L·hm^-2。10年间玉米生产（2007—2016）平均单位面积Nr损失量和GHG排放量分别为19.0 kg N·hm^-2和2 770 kg CO₂ eq·hm^-2。Nr损失量10年间较为稳定。2007—2008和2009—2011年玉米生产的平均GHG排放量呈下降趋势,2012—2016年呈稳定上升趋势,2016年达到最高的3 045 kg CO₂ eq·hm^-2。氮肥田间施用产生的氨挥发是玉米生产中活性氮损失的主要途径,硝酸盐淋洗损失次之,而氧化亚氮排放占比最低。温室气体的主要排放环节为肥料生产运输与田间施用。10年间,东北玉米生产的平均氮足迹和碳足迹分别为3.16 kg N·Mg^-1和459 kg CO₂ eq·Mg^-1。【结论】东北三省玉米生产的资源利用和环境代价在空间尺度上差异较明显,吉林省的平均肥料投入量比黑龙江省高124 kg·hm^-2,GHG排放量高524 kg CO₂ eq·hm^-2;在时间尺度上,10年间东北三省玉米生产的氮肥投入量为170—182 kg·hm^-2,Nr损失量变化范围为18.4—19.4 kg N·hm^-2,为我国玉米主产区中较低的氮肥投入与损失量。玉米生产碳、氮足迹的高低主要取决于资源投入（尤其是氮肥投入）与单产水平之间的平衡。东北三省玉米生产资源投入和环境效应的时空特征分析有助于明确现阶段限制因素与主控因子,为优化养分管理实现粮食安全和碳减排的双赢提供理论支撑。     

不同氮磷钾配施对棉花干物质积累、养分吸收及产量的影响

研究不同氮磷钾配施下棉花干物质积累与养分吸收分配的特点,为结合棉花生育特性制定高产施肥措施提供理论依据.不同施肥处理在整个生育期内植株干物质积累量较对照高9.68％～119.70％,氮、磷、钾吸收量分别较对照高12.52％～231.80％、14.92％～170.15％和13.00％～263.10％;各施肥处理籽棉和皮棉产量分别较对照提高9.42％～81.71％和15.51％％～136.96％.不同处理干物质积累和养分吸收量均大于对照,且差异显著(P＜0.05),干物质积累以N3P2(N 360 kg·hm-2,P2O5 135 kg·hm-2)处理最高,氮、磷素吸收以N3P2处理最高,钾素吸收以N2P2K2(300kg·hm-2,P2O5 135 kg·hm-2,K2O 75 kg·hm2)处理最高,籽棉和皮棉产量以N3P2处理最高.N3P2处理在生育期内干物质总积累为23 218.00 kg·hm-2,氮总吸收量为548.11 kg·hm-2,磷(P2O5)总吸收量为183.62 kg·hm-2,钾(K2O)总吸收量为668.98 kg·hm-2.籽棉产量为5 627.00 kg· hm-2,皮棉产量为2 622.33 kg·hm-2.每生产100 kg皮棉,适宜氮磷钾的养分吸收量分别为N 2.21 kg、P2O5 0.91 kg和K2O1.41kg,植株吸收养分适宜比例[m(N)∶ m(P2O5)∶m(K2O)]为2.42∶1.00∶1.55.     

A coherent signature of anthropogenic nitrogen deposition to remote watersheds of the Northern Hemisphere

Humans have more than doubled the amount of reactive nitrogen (Nr) added to the biosphere, yet most of what is known about its accumulation and ecological effects is derived from studies of heavily populated regions. Nitrogen (N) stable isotope ratios ((15)N:(14)N) in dated sediments from 25 remote Northern Hemisphere lakes show a coherent signal of an isotopically distinct source of N to ecosystems beginning in 1895 ± 10 years (±1 standard deviation). Initial shifts in N isotope composition recorded in lake sediments coincide with anthropogenic CO(2) emissions but accelerate with widespread industrial Nr production during the past half century. Although current atmospheric Nr deposition rates in remote regions are relatively low, anthropogenic N has probably influenced watershed N budgets across the Northern Hemisphere for over a century.     

有机无机肥配施对城郊设施甜玉米地N2O排放的影响

本文以长沙近郊设施菜地为研究对象,设置不施肥（CK）、常规施肥（CON）、30%牛粪有机肥氮+70%无机肥氮（CM）、30%鸡粪有机肥氮+70%无机肥氮（NM）4个处理,采用静态暗箱—气相色谱法监测甜玉米（Zea mays var. rugosa Bonaf.）生长季土壤氧化亚氮（N2O）的排放通量,同时测定土壤铵态氮、硝态氮、可溶性有机碳（DOC）含量和作物产量及吸氮量,探讨有机肥与化肥配施对甜玉米季N2O排放的影响。结果表明,甜玉米季表现出较高的N2O排放量,为24.6~33.6 kg/hm2。与CON处理相比,CM处理单位面积N2O累积排放量显著减少了26.9%,而NM处理减排不显著;CM和NM处理单位产量N2O排放量分别减少了35.7%和19.0%。与CON处理相比,CM和NM处理土壤铵态氮含量分别减少60.7%和50.1%,NM处理土壤硝态氮含量显著减少了40.4%, 而CM和NM处理土壤DOC含量无显著变化。随机森林模型和主成分分析结果表明,N2O排放通量与土壤铵态氮、硝态氮和DOC含量呈显著正相关,表明化肥配施有机肥能通过降低土壤无机氮供给,减少N2O产生。另外,较CK处理而言,CON、CM和NM处理的玉米产量分别增产了156.5%、191.8%和188.2%,且CM、NM处理较CON处理分别增加了13.8%和12.4%,CM的氮肥利用率相较于CON处理提高了15.2%。综上,30%有机肥+70%化肥能有效降低甜玉米地N2O排放和增加产量,且牛粪较佳。     

Ice record of delta13C for atmospheric CH4 across the Younger Dryas-Preboreal transition

We report atmospheric methane carbon isotope ratios (delta13CH4) from the Western Greenland ice margin spanning the Younger Dryas-to-Preboreal (YD-PB) transition. Over the recorded approximately 800 years, delta13CH4 was around -46 per mil (per thousand); that is, approximately 1 per thousand higher than in the modern atmosphere and approximately 5.5 per thousand higher than would be expected from budgets without 13C-rich anthropogenic emissions. This requires higher natural 13C-rich emissions or stronger sink fractionation than conventionally assumed. Constant delta13CH4 during the rise in methane concentration at the YD-PB transition is consistent with additional emissions from tropical wetlands, or aerobic plant CH4 production, or with a multisource scenario. A marine clathrate source is unlikely.     

Coupling of nitrous oxide and methane by global atmospheric chemistry

Nitrous oxide (N(2)O) and methane (CH(4)) are chemically reactive greenhouse gases with well-documented atmospheric concentration increases that are attributable to anthropogenic activities. We quantified the link between N(2)O and CH(4) emissions through the coupled chemistries of the stratosphere and troposphere. Specifically, we simulated the coupled perturbations of increased N(2)O abundance, leading to stratospheric ozone (O(3)) depletion, altered solar ultraviolet radiation, altered stratosphere-to-troposphere O(3) flux, increased tropospheric hydroxyl radical concentration, and finally lower concentrations of CH(4). The ratio of CH(4) per N(2)O change, -36% by mole fraction, offsets a fraction of the greenhouse effect attributable to N(2)O emissions. These CH(4) decreases are tied to the 108-year chemical mode of N(2)O, which is nine times longer than the residence time of direct CH(4) emissions.