DNDC模型对川中丘陵区稻田CH4、N2O排放的模拟对比分析

利用IKONOS高分辨率(1m)卫星遥感图,进行典型抽样和地形→土地利用→土地覆盖→综合信息提取的方法,选定了代表川中丘陵区类特征的四川省金堂县为研究区域,通过对研究区域中不同固定耕作制度下代表性田块的选取,于2005年5月—2006年5月对田块管理者进行作物田间管理、作物产出等农业生产实际情况调查和分析,进行土壤理化性状、水样的测定,并结合当地的气象资料,利用DNDC模型模拟川中丘陵区不同耕作制度下稻田温室气体的排放情况。结果表明:冬水田-水稻田(PF)水稻生长期CH4排放通量为2.24 kg.hm-2.d-1,占年排放量的80.73%;水稻生长期和冬闲期N2O通量分别为0.033和0.003 6 kg.hm-2.d-1,水稻生长期排放量为4.28 kg.hm-2,占年总排放量的83.59%。CH4和N2O排放量在水稻整个生季节存在明显的互为消长关系。油菜-小麦田(RR)水稻生长期CH4排放通量为1.16 kg.hm-2.d-1,是休闲期的20.71倍,水稻生长期CH4排放量占年排放量的90.48%;水稻生长期和非水稻生长期N2O排放通量分别为0.070和0.027 kg.hm-2.d-1,水稻生长期N2O排放量为8.01 kg.hm-2,占年排放量的54.19%。小麦-水稻田(RW)水稻生长期CH4排放通量为1.24 kg.hm-2.d-1,是休闲期的21.02倍。水稻生长期CH4排放量占年排放量的89.75%;水稻生长期和非水稻生长期N2O排放通量分别为0.089和0.030 kg.hm-2.d-1,水稻生长期N2O排放量为9.61 kg.hm-2,占年排放量的55.23%。PF年CH4排放量是RR和RW的近3倍,且少一季作物产量,应尽量将冬水田改为两季田。     

采煤驱动下复杂井田含水层化学特征与水力联系辨识

通过分析复杂井田不同含水层的常规元素、微量元素、氘氧同位素与氚同位素的水化学特征来判断各含水层的水力联系,并分别建立了Piper识别图版、Durov识别图版、氘氧同位素识别图版,借此可以快速甄别矿井突水的来源.结果表明:研究区地下水主要为大气降水补给,第四系含水层与直罗组含水层存在显著联系,直罗组含水层与延安组存在有限的联系.利用各含水层不同岩性导致的水化学离子特征差异和氘氧同位素、氚同位素的示踪特性建立识别图版,可有助于快速识别补连塔矿区突水水源,并对不同含水层的突水事故提出针对性的解决措施.     

纳米磁性颗粒Fe3O4用于吸附水相中酸性红73及其机理研究

利用纳米磁性颗粒处理含酸性红73废水以利于进一步降低其色度.实验以酸洗废液制备的纳米磁粉Fe3O4作为吸附剂,并通过单因素实验和吸附动力学及热力学的分析探讨其对酸性红73的表面吸附的吸附机理.结果表明:纳米磁粉Fe3O4对酸性红73的表面吸附符合假二级动力学方程,其反应活化能为49.05 kJ·mol-1.磁粉对酸性红73的吸附是快速的表面物理吸附,其表面吸附行为符合Langmuir等温吸附式,是放热和熵减的自发过程.在温度T为303 K的条件下,20 min内的饱和吸附量能可达到40.1 mg·g-1.因此,用纳米磁粉Fe3O4吸附处理含偶氮染料废水,吸附平衡可在很短的时间内实现.     

Hemming process with counteraction force to prevent creepage

Creepage, a typical phenomenon in the hemming process, can be defined as undesired roll-in of the panel at the bending line. Creepage also reduces the final panel width and makes the hemming radius larger. In this study, experimental observations are reported, and a finite element model, based on the LS-DYNA^® two dimensional plane strain solid formulation, is utilized to study the mechanics of how the hem flange bends and folds during the hemming process. A novel hemming process incorporating a counteraction force is proposed in order to prevent the creepage phenomenon during the hemming process. An experimental hemming tool was designed according to this concept, and optimization of the tooling geometry was carried out utilizing the finite element model. An experimental study was conducted to confirm that the new hemming process can prevent creep be employed to help retain a sharp radius during flanging operation.     

富营养湖泊沉积物中磷组分对硫酸盐的响应

采用室内模拟实验于厌氧条件下持续6周,研究不同外源硫酸盐浓度下南湖沉积物和上覆水之间的硫酸盐转化及还原情况,采用31P核磁共振(31P-NMR)研究沉积物磷组分所受影响.结果表明,硫酸盐输入促进了上覆水中pH值的升高,而氧化还原电位则呈相反的变化趋势.上覆水中SO24-浓度随时间推移而降低,但间隙水中SO24-浓度的增加幅度并不与上覆水中降低幅度一致,表明沉积物中SO24-发生了转化.沉积物的硫酸盐还原指数随SO24-输入浓度的增大而增加,沉积物中硫酸盐还原菌(SRB)的数量在第2周达到峰值,输入硫酸盐的S500和S1000处理中SRB数量远远高于未加硫酸盐的对照(CK).利用31P-NMR测定了南湖沉积物NaOH-EDTA萃取物中各种磷化合物的相对含量,南湖沉积物中的磷组分主要有正磷酸盐、磷酸单酯、磷酸二酯和焦磷酸盐,且正磷酸盐含量占绝对优势(占总磷的84.10%～95.54%),沉积物中其它磷组分含量顺序为磷酸单酯>磷酸二酯>焦磷酸盐.从总趋势来看,硫酸盐促进了沉积物中正磷酸盐的释放,且在硫酸盐还原菌数量较高时使沉积物中磷酸单酯、磷酸二酯和焦磷酸盐含量增加.     

复合磁性光催化剂Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6的制备及其光催化性能

以Co_(0.5)Zn_(0.5)Fe_2O_4为磁基体,制备了Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6复合磁性光催化剂。分别采用XRD、SEM、EDS和PL光谱技术对光催化剂进行了表征。利用氙灯为光源,以环丙沙星为目标污染物,考察了光催化剂对环丙沙星的降解性能。表征结果显示:复合磁性光催化剂中Bi_2WO_6晶相含量高,且结晶度大;Co_(0.5)Zn_(0.5)Fe_2O_4与Bi_2WO_6的质量比为1∶8时,Co_(0.5)Zn_(0.5)Fe_2O_4磁基体与Bi_2WO_6基本复合(该复合磁性光催化剂以Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6(Ⅱ)表示);Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6复合光催化剂光生空穴和电子复合几率低,具有较好的光催化性能。实验结果表明,Co_(0.5)Zn_(0.5)Fe_2O_4/Bi_2WO_6(Ⅱ)具有较高的光催化活性,光催化反应140 min后对环丙沙星的降解率达82.39%,且具有良好的磁性能,易实现固液分离,便于回收再利用。     

One-pot hydrothermal fabrication of BiVO4/Fe3O4/rGO composite photocatalyst for the simulated solar light-driven degradation of Rhodamine B

• BiVO₄/Fe₃O₄/rGO has excellent photocatalytic activity under solar light radiation. • It can be easily separated and collected from water in an external magnetic field. • BiVO₄/Fe₃O₄/0.5% rGO exhibited the highest RhB removal efficiency of over 99%. • Hole (h⁺) and superoxide radical (O₂^•−) dominate RhB photo-decomposition process. • The reusability of this composite was confirmed by five successive recycling runs. Fabrication of easily recyclable photocatalyst with excellent photocatalytic activity for degradation of organic pollutants in wastewater is highly desirable for practical application. In this study, a novel ternary magnetic photocatalyst BiVO₄/Fe₃O₄/reduced graphene oxide (BiVO₄/Fe₃O₄/rGO) was synthesized via a facile hydrothermal strategy. The BiVO₄/Fe₃O₄ with 0.5 wt% of rGO (BiVO₄/Fe₃O₄/0.5% rGO) exhibited superior activity, degrading greater than 99% Rhodamine B (RhB) after 120 min solar light radiation. The surface morphology and chemical composition of BiVO₄/Fe₃O₄/rGO were studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, and Raman spectroscopy. The free radicals scavenging experiments demonstrated that hole (h⁺) and superoxide radical (O₂^•−) were the dominant species for RhB degradation over BiVO₄/Fe₃O₄/rGO under solar light. The reusability of this composite catalyst was also investigated after five successive runs under an external magnetic field. The BiVO₄/Fe₃O₄/rGO composite was easily separated, and the recycled catalyst retained high photocatalytic activity. This study demonstrates that catalyst BiVO₄/Fe₃O₄/rGO possessed high dye removal efficiency in water treatment with excellent recyclability from water after use. The current study provides a possibility for more practical and sustainable photocatalytic process.     

宁夏灌区不同类型农田土壤氮素累积与迁移特征

在宁夏灌区选择设施菜田（n=4）和水旱轮作大田（n=4）,通过田间多点取样观测和室内分析的方法,研究了2种类型农田土壤氮素累积与分布特点,以及其迁移对浅层地下水的影响。结果表明,设施菜田0~150 cm土壤剖面溶解性总氮（TSN）、硝态氮（NO3--N）和溶解性有机氮（SON）含量都显著高于大田,前者分别是后者的1.5~5.6、1.5~3.4倍和1.6~9.8倍。设施菜田土壤氮素主要累积在0~5 cm和5~20 cm土层,而大田主要在40~100 cm土体。设施菜田和大田土壤溶解性总氮占全氮比例分别在5.4%~11.5%和2.2%~4.9%之间,前者的淋失风险较高。设施菜田各形态氮素累积量表现为SON＆gt;NO3--N＆gt;NH4＋-N,大田为NO3--N＆gt;SON＆gt;NH4＋-N。设施菜田浅层地下水中TSN、NO3--N和SON含量也都显著高于大田,前者平均含量分别是后者的9.5、13.8倍和7.0倍。因此,硝态氮和溶解性有机氮都是2种类型农田氮素累积的主要形态,也是浅层地下水污染的重要来源。     

大气CO2摩尔分数升高对高、低应答水稻稻田N2O排放的影响

依托稻田大气CO₂摩尔分数（x［CO₂］）升高平台FACE （free-air CO₂ enrichment）,采用静态透明箱-气相色谱法研究x［CO₂］升高（正常x［CO₂］+200 μmol·mol^-1）对高、低应答水稻（产量对x［CO₂］升高的响应分别为>30%和10%~15%）稻田N₂O排放的影响.本试验设置4个处理：A-W （正常x［CO₂］+低应答水稻）、F-W （x［CO₂］升高+低应答水稻）、A-S （正常x［CO₂］+高应答水稻）和F-S （x［CO₂］升高+高应答水稻）.结果表明,对比正常x［CO₂］处理（A-S和A-W）,x［CO₂］升高条件下高、低应答水稻（F-S和F-W）稻田N₂O排放分别降低52.54%（P<0.05）和38.40%（P<0.05）,水稻产量分别增加22.96%（P<0.05）和12.11%（P>0.05）,稻田N₂O排放强度分别降低61.68%（P<0.05）和45.13%（P<0.05）.另外,高、低应答水稻稻田N₂O排放与稻田土壤NH₄⁺-N含量呈显著相关关系,而与NO₂^--N含量无显著相关.x［CO₂］升高条件下,土壤温度是影响高应答水稻稻田N₂O排放的重要因素.综合考虑,未来x［CO₂］升高条件下,高应答水稻品种的"增产减排"效果最佳.