土壤团聚体有机碳研究进展

土壤有机碳是衡量土壤肥力的重要指标,对于促进土壤养分循环、增加养分有效性有重要作用。土壤团聚体是土壤的重要组成部分,是组成土壤结构的最小单元,受到自然因素和人为因素的影响,其形成转化过程与土壤固碳过程息息相关,因而研究团聚体和有机碳的关系及团聚体有机碳影响因素对于土壤结构的改善和土壤质量的提升具有重要意义。本文通过对文献的总结,明晰了土壤团聚体和有机碳的关系,阐述了土壤类型、施肥方式、土地利用和矿区复垦对土壤团聚体有机碳的影响,并从生物质炭的长期定位研究和复垦矿区的土壤修复两方面对土壤团聚体有机碳的研究进行展望,研究结果可为合理的农业生产提供科学依据。     

Poorly crystalline iron and aluminium oxides contribute to the carbon saturation and sorption of dissolved organic carbon in the soil

Soil carbon (C) saturation implies an upper limit to a soil's capacity to store C depending on the contents of silt + clay and poorly crystalline Fe and Al oxides. We hypothesized that the poorly crystalline Fe and Al oxides in silt + clay fraction increased the C saturation and thus reduced the capacity of the soil to sorb additional C input. To test the hypothesis, we studied the sorption of dissolved organic carbon (DOC) on silt + clay fractions (<53 µm) of highly weathered oxic soils, collected from three different land uses (i.e., improved pasture, cropping and forest). Soils with high carbon saturation desorbed 38% more C than soils with low C saturation upon addition of DOC, whereas adsorption of DOC was only observed at higher concentration (>15 g kg^?1). While high Al oxide concentration significantly increased both the saturation and desorption of DOC, the high Fe oxide concentration significantly increased the desorption of DOC, supporting the proposition that both oxides have influence on the DOC sorption in soil. Our findings provide a new insight into the chemical control of stabilization and destabilization of DOC in soil.     

Impact of grassland contract policy on soil organic carbon losses from alpine grassland on the Qinghai–Tibetan Plateau

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi‐household management pattern (MMP: grassland shared by several households without enclosures) and a single‐household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government's grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 × 10⁷ and 6.15 × 10⁷ Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre‐1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for land management strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.     

Seasonal Losses of Surface Litter in Northern Great Plains Mixed-Grass Prairies

Surface litter protects rangeland soils against wind and water erosion and provides food and nesting materials for wildlife and insects. However, the ability of grassland systems to provide these services depends on the little studied topic of seasonal surface litter decomposition. Seasonal and annual surface litter decomposition rates were determined between 2014 and 2015 in central and western South Dakota at three mixed-grass prairie locations. Residue bags containing surface litter were placed in the field in late fall (1 November) of 2014 and removed after the winter (1 April), spring (1 July), and summer + fall seasons (1 November) of 2015. The litter was analyzed for total C, total N, acid detergent fiber (ADF), and acid detergent lignin (ADL). Average winter temperatures ranged from −5^oC to −15^oC, while summer temperatures ranged from 10^oC to 35^oC. Litter decomposition was lowest during the winter (0.57−0.86 g [kg × day]⁻¹) and greatest during the summer + fall (2.12−2.69 g [kg × day]⁻¹). Over the entire season, 40.8−62% of the surface litter decomposed. Winter litter decomposition was positively correlated with air temperature (r = 0.62, P < 0.01) and snow depth (r = 0.61, P < 0.01), and negatively correlated with C/N ratio (r = −0.65, P < 0.01), ADF (r = −0.35, P < 0.05), and ADL (r = −0.25, P < 0.05) concentrations. These findings indicate that winter decomposition cannot be ignored and that winter surface litter decomposition increases with snow depth.     

活性炭吸附痕量银的研究

在静态、动态吸附条件下，分别选用果壳类净水用活性炭和煤质净水用活性炭对胶片工业废水中的痕量银的吸附行为进行了研究．结果表明，废水中的银浓度可降至＜５０ｐｐｂ，活性炭对银的吸附量达到３～５ｍｇ／ｇ．微孔发达的活性炭更适于吸附废水中的痕量银．随着银液浓度的升高，银液量增大，活性炭吸附能力增加．银液的最佳吸附ｐＨ值是５．     

The effects of stubble burning and tillage on soil carbon sequestration and crop productivity in southeastern Australia

Abstract. In Australia, stubble burning and tillage are two of the major processes responsible for the decline of soil organic carbon concentration in cropped soils, and the resulting soil degradation. However, the relative importance of these two practices in influencing the soil organic carbon concentration and the long-term impact on soil quality and productivity are not clear. The effects of stubble burning as practised by farmers in southeastern Australia were evaluated in two field trials, one of 19 years duration, the other of 5 years. Conventional tillage (three tillage passes) led to greater loss of soil organic carbon than stubble burning. Loss of total soil organic carbon attributed to stubble burning in the 0–10 cm layer was estimated to be 1.75 t C ha⁻¹ over the period of the 19-year trial, equivalent to 29% of that lost due to tillage. In the 5-year trial, no change in soil organic carbon due to stubble burning was detectable. Changes in soil quality associated with stubble burning detected in the longer trial included a reduction in macro-aggregate stability, and increases in pH and exchangeable K⁺. Only the latter two were detected in the shorter trial. A higher mean wheat yield (average 0.15 t ha⁻¹) following stubble burning was observed in the 19-year trial but not in the 5-year trial. Research to monitor the longer term effects of stubble burning is needed, and to identify conditions where loss of soil organic carbon is minimized.     

有效碳数法研究及其在农药气相色谱分析中的应用

有机化合物结构与其所含有的有效碳数有一定的关系，本文给出了２０类结构化合物及其所含有有效碳数的关系，并对理论计算值和实测值进行了比较，结果十分接近，利用有效碳数法可以设计农药分析实验方案和无标样的情况下测定农药杂质含量。     

甘肃温室葡萄生产的能量利用与碳足迹研究

【目的】探明甘肃温室葡萄生产的能量投入和碳足迹构成,识别主要的碳排放贡献因子,为温室葡萄清洁生产提供依据。【方法】以甘肃温室葡萄为研究对象,将温室葡萄栽培区分为兰州市永登县及武威市凉州区、古浪县、天祝县华藏寺镇和天祝县哈溪镇5个不同海拔区域,通过农户调查获得2019年葡萄生产数据,核算温室葡萄生产各环节的能量输入、能量输出和碳排放,对比分析不同海拔区域温室葡萄生产的能量利用效率、能量生产率、净能量、比能和碳足迹。【结果】甘肃温室葡萄生产的能量输入为273 862～434 421 MJ/hm²,能量输出为170 723～327 962 MJ/hm²,葡萄产量为14 460～27 793 kg/hm²,属于高投入高产出型。甘肃温室葡萄生产的能量利用效率为0.45～1.13,能量生产率为0.038～0.096 kg/MJ,净能量为-263 798～2 496 MJ/hm²,比能为13.51～44.85 MJ/kg;直接能量投入和可再生能量投入占比低,间接能量投入和不可再生能量投入占比高。单位面积碳足迹和单位产量碳足迹分别为32 959～55 075 kg/hm²和1.59～5.70 kg/kg,碳足迹很大程度上来源于氮肥的投入,其占比达45.5%～62.4%。不同区域相比,天祝县哈溪镇温室葡萄生产的能量输入低,能量输出和产量较高,能量利用效率和能量生产率也较高,净能量最大且为正值,比能最小,单位面积碳足迹和单位产量碳足迹均最小;天祝县华藏寺镇能量利用指标最差,碳足迹最大。【结论】甘肃温室葡萄生产的能量利用效率较低,碳足迹较高,能量利用效率的提高和碳足迹的降低空间均较大。因此应采取降低氮肥使用量、优化氮肥与有机肥配比等科学合理的管理措施,提高甘肃温室葡萄生产的能量利用效率,降低碳足迹,改善其环境效应。     

氮沉降对城市森林凋落物养分元素含量及其耦合性的影响

目前,氮沉降增加呈现全球化趋势,影响森林生态系统生物地球化学循环过程,已成为生态和环境研究的热点内容之一。为探讨氮沉降增加对城市森林凋落物养分含量的影响,进一步认识城市森林养分循环过程,为区域城市化进程的生态风险评估提供科学依据,本研究以安徽省合肥市蜀山国家森林公园凋落物为研究对象,在连续3年模拟氮沉降实验后（氮添加设置3种水平,分别为对照组：0 kg·hm^-2·a^-1、CK;低氮：50 kg·hm^-2·a^-1、LN;高氮：100 kg·hm^-2·a^-1、HN）,研究氮沉降对城市森林凋落物（枝叶果碎）养分元素含量及其耦合性的影响。结果表明：（1）不同施氮水平下,凋落果内CK与HN中C元素含量,凋落叶中CK与LN、碎中LN与HN两组中N元素含量差异显著（P＜0.05）。（2）凋落物不同组分间,N沉降显著影响Ca元素含量（P＜0.05）,对C元素含量无显著影响;凋落枝组分间K含量差异显著（P＜0.05）,凋落叶与其他各组间N含量差异显著（P＜0.05）,凋落果与其他各组间P含量差异显著（P＜0.05）;凋落叶与凋落果间Mg元素差异显著。（3）N沉降对各组分间的C/N、C/P、N/P等生态化学计量比无显著性影响,但对凋落叶、凋落果中C/N值有显著抑制作用（P＜0.05）。（4）N沉降显著影响C、N间相关性及Ca、Mg间相关性,且均表现为LN显著增强相关性,HN显著抑制相关性;N沉降显著增强了P、K间的相关性,而显著降低了K与Ca、Mg的相关性。（5）N沉降对C/N与N/P、C/P与N/P间的耦合性有显著影响,且均表现为LN显著增强生态化学计量比间的耦合性,HN显著降低二者耦合性。研究结果为城市森林凋落物养分循环过程对N 沉降的响应提供了理论依据。