The Suess effect: Carbon-Carbon interrelations

The Suess Effect is a term which has come to signify the decrease in ¹⁴C in atmospheric CO₂ owing to admixture of CO₂ produced by the combustion of fossil fuels. This term is here extended, as a concept, to the shifts in isotopic ratio of both ¹³C and ¹⁴C in any reservoir of the carbon cycle owing to anthropogenic activities. To explain this generalized Suess Effect a four reservoir global model of the natural carbon cycle is developed in which isotopic fractionation and radioactive decay are fully taken into account. The model includes the cases in which the deep ocean is treated either as a single undifferentiated box model reservoir or is vertically differentiated with eddy diffusion governing the transport of carbon. Also, the governing equations are expressed with sufficient generality to apply simultaneously to both rare isotopes. In so far as possible, the model is expressed without approximation of the isotopic processes even though this leads to non-linear differential equations to describe the rates of change of rare isotopic carbon within carbon reservoirs. Linear approximations also developed and solved using the method of Laplace transforms. The sensitivity of the predicted Suess Effects to uncertainties in the assigned values of the model parameters is investigated in detail, including estimates of some of the effects of linearizing the governing equations.The approximation of Stuiver, in which the atmospheric Suess Effect is assumed to be 0.018 times the corresponding effect for ¹⁴C, is examined in detail and shown to arise when both isotopic fractionation and radioactive decay are left out of the model. This approximation, although correct as to order of magnitude, is found to be too imprecise to be recommended in modeling studies.As found in previous work, the predicted atmospheric Suess Effect for ¹³C for a given airborne fraction of industrial CO₂ is of similar magnitude whether the land biosphere has been a net source or sink of carbon during recent times. On the other hand, the corresponding effect for a surface ocean water is considerably smaller than otherwise if the land biosphere has been a source of CO₂ instead of a sink. The model is thus useful in indicating the need to consider isotopes in several reservoirs simultaneously.Although the emphasis is on formulating models rather than surveying and interpreting data, observational data are summarized and compared with model predictions. The oceanic data are seen to be too meager as yet to help settle the question of biospheric response to man's activities.     

近30 a贵州遵义县农田土壤有机碳动态及影响因素分析

论文选择贵州省遵义县为典型样区,使用1980 年代第二次土壤普查数据和2011 年实测数据,以耕地土壤图为基础,运用土壤类型法和通用有机碳密度度量法,测算样区近30 a农田土壤有机碳（SOC）储量和密度变化特征,借助逐步回归分析法,识别影响这一变化的潜在驱动因素,结果表明：①样区近30 a 农田总丢碳量2.94×10⁴ t,整体呈基本持平略带下降趋势;②样区近30 a农田单位面积碳变化量为-132.03 kg C·hm^-2,年均变化速率-4.40 kg C·hm^-2·a^-1,固碳、丢碳和相对平衡面积比为49.45: 32.96: 17.59;③不同土壤类型间不管是SOC储量还是土壤有机碳密度（SOCD）均差异显著,丢碳幅度最大的是山地黄棕壤,达77.34%,固碳幅度最大的是紫色土,是1980 年代的1.1 倍;④空间分布上,总体展现为以娄山山脉为界的西北丢碳东南固碳态势;⑤SOCD_1980s、机械组成（砂粒比、粘粒比、粉粒比）、全N密度、C/N 等指标是影响样区近30 a 间农田SOC变化的主要因素,且除SOCD_1980s外,剩余5 因素与SOCD年均变化速率间拥有正相关关系。研究有助于查明样区近30 a 农田SOC变化的本底和潜在影响因素,为未来农田SOC的管理提供数据基础。     

含硅熔渣对水稻养分吸收及产量的影响

采用盆栽试验方法，研究了不同含硅熔渣对水稻养分的吸收和产量的影响，结果表明，在施用氮、磷、钾肥的基础上，增施不同类型的含硅熔渣，可提高水稻中硅和磷的含量，降低根系、茎叶和籽粒中的氮、钾含量，增加水稻对氮、磷、钾、硅的总吸收量。不同含硅熔渣的增产效果差异较大，增产最显著的是铁渣和黄磷炉渣，分别比对照增产43．4％和31．6％，施用含硅熔渣的各处理比对照平均增产19．1％，各处理间的产量经方差分析和多重比较达显著或极显著差异水平。扩散方程、Elovich方程和多项式方程均能很好地描述水稻生长期内水稻对N、P、K、Si的吸收过程，尤以多项式方程拟合最佳。     

Fe-Al改性硅藻土与CaO配施改良Cd污染土壤

以人工模拟Cd污染土壤为研究对象,以Fe-Al改性硅藻土和CaO为原料制备组配改良剂,通过土壤培养试验研究了Fe-Al改性硅藻土与CaO不同配比对组配改良剂改良Cd污染土壤效果的影响.结果表明,向Cd污染土壤施加Fe-Al改性硅藻土与CaO以不同配比所制得组配改良剂对土壤Cd形态、pH值、CEC值、OM值、含水率、有效氮、速效磷、有效钾均产生了积极的影响.当Fe-Al改性硅藻土与CaO的配比为1：6时,土壤可交换态Cd含量较空白对照降低了74.67%,较单一施加Fe-Al改性硅藻土和CaO分别降低了64.63%和7.87%,与对照相比,土壤pH值提升了0.45,土壤CEC提升了69.78%,土壤有效氮、速效磷分别提升了28.57%、70.85%.Fe-Al改性硅藻土与CaO配施能有效控制土壤Cd污染,同时还可有效改善土壤耕作性能.