Meta分析生物质炭对中国主粮作物痕量温室气体排放的影响

该文采用Meta分析方法定量分析生物质炭输入对中国主粮作物痕量温室气体的影响,研究可为农田痕量温室气体减排提供有效的途径.结果表明相对于不施加生物质炭,生物质炭输入对甲烷吸收/排放并无显著影响,而甲烷排放在不同耕作和施氮情况下发生显著变化.旋耕和不施氮情况下施加生物质炭分别显著提高稻田甲烷排放达30%和46%,而在翻耕和施氮的情况下施加生物质炭可减少稻田甲烷排放达9%和10%.生物质炭输入分别可显著减少主粮作物氧化亚氮、全球增温潜势(global warming potential,GWP)及温室气体排放强度(greenhouse gas intensity,GHGI)达41%、18%及25%.不同土地利用类型、耕作类型、生物质炭施用量及生物质炭类型均可显著影响农田氧化亚氮、GWP和GWPI.合理的管理主粮作物生物质输入可为减少温室气体排放做出贡献,建议生物质炭与施氮和翻耕2种农作措施相结合,施加小于10 t/hm2及碳氮比(C/N)低于80的生物质炭,以利于主粮作物综合温室效应的减排.     

气候模拟数据订正方法在作物气候生产潜力预估中的应用 ——以江苏冬小麦为例

利用全球气候模式BCC_CSM1.1（Beijing Climate Center Climate System Model version 1.1）,耦合区域气候模式RegCM4（Regional Climate Model version 4）输出的1961-1990年（基准时段）气候模拟数据,并根据同期实测资料,确定模拟值和实测值之间的非线性传递函数与方差订正参数,构建气候模拟数据的误差订正模型。利用1991-2005年（验证时段）模拟数据与实测资料验证该模型的有效性,并对RCP（Representative Concentration Pathway）情景下2021-2050年（未来时段）气候模拟数据进行订正,同时通过潜力衰减方法预估未来江苏冬小麦气候生产潜力格局。结果表明：将气候模拟数据订正方法应用到作物气候生产潜力预估是有效的。以均值传递函数和方差信息建立的模型可以较好订正江苏逐日气候模拟数据。订正后的秋冬季气温、辐射量、蒸散量和冬春季降水量模拟偏差明显减小。在此基础上研究发现,冬小麦的成熟期在RCP4.5和RCP8.5情景下介于153~175和153~174,较基准时段均明显提前。两种情景下冬小麦气候生产潜力分别介于10335~14368kg·hm^-2和9991~13708kg·hm^-2,较基准时段呈下降趋势。其变异系数分别介于7.6%~14.6%和7.5%~13.6%,较基准时段呈增大趋势,表明江苏冬小麦气候生产潜力总体趋于不稳定。未来时段,徐州中北部、连云港东北部、宿迁西部以及盐城东南部冬小麦在RCP4.5和RCP8.5情景下可以保持相对较高的生产潜力（≥12501kg·hm^-2）,该省应确保这些地区的冬小麦种植用地。研究建议,作物气候生产潜力预估应考虑利用研究区实测资料对气候模拟数据进行订正,以提高预估可信度。     

Effect of green manuring (Sesbania aculeata) on zinc equilibria in submerged calcareous and non-calcareous soils

Summary A pot experiment was conducted to study the effect of green manuring (Sesbania aculeata) on pH, electrical conductivity (EC), Zn concentration and ZN equilibria in a calcareous and a non-calcareous soil under submerged conditions. The soil solutions were drawn anaerobically by gravity and analysed for pH, EC and Zn. Green manuring lowered the pH and increased the EC throughout submergence compared with the untreated control. The effect of green manuring was more pronounced in non-calcareous soil. The concentration of water-soluble Zn under submergence alone continued to decline up to the end of the experiment in both soils. But Zn concentration in green manure-amended soil was lower during the initial stages and higher in the later stages in comparison with the unamended soil. Zn potential values in the case of submergence alone were within the range of the ZnCo₃-Zn²⁺ (aq) system up to 1 week and 4 weeks for non-calcareous and calcareous soil, respectively. Thereafter they shifted to those of the Zn-soil (unknown solid phases)-Zn²⁺ (aq) system. Under green manuring the values were within the range of the latter system throughout the experiment.     

Variations in soil characteristics affecting the occurrence of Aphanomyces root rot of sugar beet - Risk evaluation and disease control

Damping off and chronic root rot of sugar beet caused by Aphanomyces cochlioides is a major constraint in cultivation of sugar beet, with occurrence of the disease in Sweden being concentrated to specific areas. This study examined soil factors that can be used for risk assessment of Aphanomyces root rot. Soils from 134 field plots were assessed over three years for Aphanomyces root rot potential in bioassays and analysed for easily measured soil factors such as soluble nutrients, pH and soil electrical conductivity (EC). Classification of the field plots into four groups with increasing disease severity index (DSI) according to the bioassay revealed that the group with the lowest DSI (<39) had an average soil calcium (Ca) content of 430 mg/100 g and a soil EC of 1.12 mS/cm, which were significantly higher than in the groups with DSI >40. From these results, we concluded that soil Ca concentration is an easily measured factor that can be used to identify soils with an increased risk of Aphanomyces root rot. We suggest that the Ca content should be above 250 mg Ca/100 g soil to avoid problems with Aphanomyces root rot in sugar beet. To gain a more thorough understanding of the geographical variation in Aphanomyces root rot and its connection to the geological origin of the soils, a number of other soil factors were analysed in the field plots, including clay mineralogy, CEC, and particle size distribution. Aphanomyces root rot was very rare in soils with a high proportion of smectite and vermiculite relative to illite and kaolin minerals, here predominantly calcareous soils developed on clay till in south-western Scania.     

复垦土壤重金属污染潜在生态风险评价

为揭示矿区复垦土壤中重金属元素潜在的污染特征,采用Hakanson 潜在生态风险指数（The Potential Ecological Risk Index）,对安太堡露天煤矿复垦土壤中Cd,Cr,Cu,Pb,Hg,As等6种污染元素进行了分析,研究了露天煤矿复垦土壤重金属污染程度及潜在的生态危害性。结果表明：安太堡露天煤矿不同复垦时间和复垦模式下不同层次的复垦土壤的综合污染程度范围为8.29～16.90,平均值为10.72,处于中等的污染程度。重金属潜在风险指数在131.43～331.03之间,平均191.68,生态风险达到了中等程度,特别是复垦13年的南排1?420退化平台,综合潜在生态风险指数为331.03,达到了较高程度。0～40 cm土层的潜在生态风险综合评价属于中度的潜在生态风险。Hg是主要的污染因子,其对潜在的生态风险指数所贡献的比例达到了72.5%～84.62%。其余重金属的生态风险较低。因此,在安太堡露天煤矿复垦土壤中,Hg是最主要的潜在污染因子,应采取一定的措施,防止Hg的污染。应用该体系对复垦土壤重金属污染生态风险评价所得的结论同其它研究结果互为补充和借鉴。     

Iron Toxicity in Lowland Rice

Lowland rice is a staple food for more than 50% world population. Iron toxicity is one of the main nutritional disorders, which limits yield of lowland rice in various parts of the world. The toxicity of iron is associated with reduced soil condition of submerged or flooded soils, which increases concentration and uptake of iron (Fe^{2 +}). Higher concentration of Fe^{2 +} in the rhizosphere also has antagonistic effects on the uptake of many essential nutrients and consequently yields reduction. In addition to reduced condition, increase in concentration of Fe^{2 +} in submerged soils of lowland rice is associated with iron content of parent material, oxidation-reduction potential, soil pH, ionic concentration, fertility level, and lowland rice genotypes. Oxidation-reduction potential of highly reduced soil is in the range of –100 to –300 mV. Iron toxicity has been observed in flooded soils with a pH below 5.8 when aerobic and pH below 6.5 when anaerobic. Visual toxicity symptoms on plants, soil and plant tissue test are major diagnostic techniques for identifying iron toxicity. Appropriate management practices like liming acid soils, improving soil fertility, soil drainage at certain growth stage of crop, use of manganese as antagonistic element in the uptake of Fe^{2 +} and planting Fe^{2 +} resistant rice cultivars can reduce problem of iron toxicity.     

Radiocesium interception potential (RIP) of smectite and kaolin reference minerals containing illite (micaceous mineral) as impurity

Cesium-137 (¹³⁷Cs) is strongly adsorbed on clay minerals, especially on illite. The adsorption of Cs⁺ on reference clay minerals, however, has not been fully investigated in relation to the presence of illite. The objective of this study was to clarify the effect of impurities (i.e., illite and vermiculite), present in reference smectite group minerals and kaolin minerals, on the retention of Cs⁺. The clay mineralogy of the reference minerals was characterized by X-ray diffraction (XRD). The radiocesium interception potential (RIP) was measured as an index of the Cs⁺ retention ability of clays. The content of illite in clay was represented by the total potassium (K) content given that illite is a major source of K in the clay fraction. The content of vermiculite in clay was represented by the Cs fixation capacity induced by Cs saturation followed by heating of samples at 110°C. Metabentonite and beidellite gave extremely high RIP values compared with other smectite group minerals, although a peak for illite (at 1.0 nm) was not observed in XRD analysis. The reference smectite and kaolin minerals showed a range of RIP values, even though their RIP values are theoretically zero. The RIP values had a significant positive correlation with the total K content of all the reference clay minerals (r_s = 0.621*). This indicated that the retention ability for ¹³⁷Cs depended more on the content of illite, as impurity, rather than the type of bulk mineral. Hence, the contribution of illite to the magnitude of the RIP was elucidated by the combination of measurement of total K content and XRD analysis.     

基于植被恢复潜力的强度石漠化地区立地因子研究

 石漠化地区立地分类及其植被恢复潜力评价是石漠化地区生态修复的重要基础,立地因子研究是立地分类与评价的前提。通过对典型强度石漠化地区毕节石桥小流域和花江峡谷立地条件调查,利用成因分析与统计分析方法,研究强度石漠化地区影响植被恢复潜力的主要立地因子。结果表明：岩性和坡性是强度石漠化地区基于植被恢复潜力的主导立地因子。研究结果可为强度石漠化地区立地分类的建立与植被恢复潜力评价提供依据。     

关于“恒电位表面”概念的讨论

长期以来,人们认为水合氧化物型表面（可变电荷表面）的定位离子是Ｈ＾＋和ＯＨ＾－,所以表面电位（Φ０）只是ｐＨ值的函数,而与电解质的浓度无关。所以反水合氧化物型表面又称恒电位表面。本文从理论上和实验上都表明,情况并非这样,可变电荷表面的电位强烈地依赖于电解质浓度,并且其表面电荷密度既依赖于溶液ｐＨ值也依赖于电解质浓度。所以,可变电荷表面并非恒电位表面。     

Spatial and Temporal Variability of Groundwater Nitrate Concentrations in Irrigated Mediterranean Agriculture

As nitrogen (N) fertilizer-use efficiency rarely exceeds 50% in most agricultural systems, the potential leaching of N to the groundwater, particularly under irrigated conditions, has economic, health, and environmental implications. Research in the Akarsu irrigation district in the Lower Seyhan Plain in southern Turkey sought to determine spatial and temporal variability of groundwater (GW) nitrate (NO₃) concentrations in 2007–2008. Shallow groundwater observation wells 3 m deep were installed at different locations to represent the whole irrigation district. Groundwater samples were collected (February, April, July, October) and analyzed for ammonium (NH₄) and NO₃ concentrations. Because NH₄ values were negligible, only NO₃ data were processed to determine spatial and temporal variability and then used to develop regional NO₃ maps using geographic information systems. Groundwater NO₃ concentrations ranged between 0.17 and 55.96 mg L^–1 during the 2 years, only exceeding the critical 50 mg L^–1 concentration in 1% of the area sampled. The areal mean of NO₃ concentration was greatest in February, indicating a potential N leaching of unused N from the early season with intensive rainfall, especially in wheat-growing areas. Groundwater NO₃ concentrations decreased after February; however, during the peak irrigation season in July, NO₃ was relatively low because of crop uptake during spring and summer. In about half the area, groundwater NO₃ concentrations ranged between 20 and 50 mg L^–1 and were thus marginal relative to the critical pollution level. As N fertilizer use will continue to increase, especially with the expanded irrigation that is now occurring in the Mediterranean region, regular monitoring of groundwater NO₃ is advisable under such conditions.