土施和喷施锌肥对镉低积累油菜吸收镉的影响

采用盆栽试验,研究了土施和喷施不同用量Zn SO4对镉(Cd)低积累油菜生长、Cd吸收及微量元素含量的影响,并通过分析Cd在油菜体内的累积分配规律及土壤Cd有效性变化来揭示其作用机理.结果表明,土施锌(Zn)肥可以显著提高Cd低积累油菜的地上部生物量,最大可使其比对照处理增加71.4%;而喷施Zn肥对Cd低积累油菜地上部生物量没有显著影响.土施和喷施Zn肥都可显著降低Cd低积累油菜的地上部Cd含量,最大降幅为41.4%;在Zn肥用量相差8~10倍的情况下,二者降低油菜地上部Cd含量的效果无显著差异.土施Zn肥可使Cd低积累油菜地上部Cu和Fe含量显著升高,而喷施Zn肥对其没有显著影响,土施和喷施Zn肥都使Cd低积累油菜地上部Mn含量显著降低.土施Zn肥可显著提高土壤有效态Zn含量,但对土壤有效Cd含量没有显著影响;土施和喷施Zn肥可以显著降低油菜根部Cd净吸收量和Cd转运系数,油菜地上部Cd含量与根部Cd净吸收量呈显著的正相关关系(p0.01),而与Cd转运系数无显著的相关性,这表明施用Zn肥降低油菜地上部Cd含量主要是由于抑制根部Cd吸收引起的.总之,喷施Zn肥是调控Cd低积累油菜安全生产的较好措施.     

Experimental study on ignitability of pure aluminum powders due to electrostatic discharges and Nitrogen's effect

In order to prevent dust explosions due to electrostatic discharges (ESD), this paper reports the minimum ignition energy (MIE) of aluminum powders in the air and the effective nitrogen (N₂) concentration for the inert technique. The Hartman vertical-tube apparatus and five kinds of different sized pure aluminum powders (median particle size, D50; 8.53 μm–51.2 μm) were used in this study. The statistic minimum ignition energy (MIE_s) of the most sensitive aluminum powder used in this study was 5 mJ, which was affected by the powder particle size (D50; 8.53 μm). In the case of aluminum powder, the inerting effects of N₂ were quite different from the polymer powders. The MIE of aluminum powder barely changed until the N₂ concentration was 89% in comparison with that of the normal air. When the N₂ concentration was 90%, the MIE of aluminum powders suddenly exceeded 1000 mJ, which does not occur easily with ESD in the industrial process.     

Resolving the influence of nitrogen abundances on sediment organic matter in macrophyte-dominated lakes, using fluorescence spectroscopy

A controlled experiment was designed to resolve the influence of nitrogen abundance on sediment organic matters in macrophyte-dominated lakes using fluorescence analysis. Macrophyte biomass showed coincident growth trends with time, but different variation rates with nitrogen treatment. All plant growth indexes with nitrogen addition (N, NH₄Cl 100, 200, 400 mg/kg, respectively) were lower than those of the control group. Four humiclike components, two autochthonous tryptophan-like components, and one autochthonous tyrosine-like component were identified using the parallel factor analysis model. The results suggested that the relative component changes of fluorescence in the colonized sediments were in direct relation to the change of root biomass with time. In the experiment, the root formation parameters of the plants studied were significantly affected by adding N in sediments, whichmay be related to the reason that the root growthwas affected byNaddition. Adding a low concentration of N to sediments can play a part in supplying nutrients to the plants. However, the intensive uptake of NH₄⁺ may result in an increase in the intracellular concentration of ammonia, which is highly toxic to the plant cells. Hence, our experiment results manifested that organic matter cycling in the macrophyte-dominated sediment was influenced by nitrogen enrichment through influencing vegetation and relevant microbial activity.     

控释肥条件下沿南四湖农田水稻吸氮特征

氮素是水稻必需营养元素中限制植物生长和形成产量的首要因素,同时也是南四湖水体主要营养性污染物之一.通过施用树脂包膜控释尿素不同氮肥量处理大田试验,研究了南四湖流域鱼台农田控释肥条件下水稻生育期的吸氮特征.结果表明,树脂包膜控释尿素对水稻产量有明显的促进作用,但并不随施氮量的增加呈线性增长,施用中氮量337.5 kg/h...     

Alternative cropping systems for sustainable water and nitrogen use in the North China Plain

Serious water deficits and excessive nitrogen (N) applications are threatening the sustainability of intensive agriculture in the North China Plain (NCP). This study examined the possibility of replacing the conventional system (Con.W/M) of winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.), with an optimized double cropping system (Opt.W/M), a 2-year system (winter wheat/summer maize-spring maize, W/M-M), and a monoculture system (spring maize, M) based on optimal water and N management strategies. From 2004 to 2010, a long-term field experiment conducted in the NCP showed that although >70 mm of irrigation water can be saved with Opt.W/M compared with Con.W/M, annual net groundwater use under Opt.W/M was still 250 mm, 65-90% of which was consumed during the winter wheat season. When wheat production was decreased, 35% and 61% of irrigation water could be reduced in W/M-M and M compared to Con.W/M, respectively. As a result, annual groundwater use was decreased to 190 mm in W/M-M and 94 mm in M. Meanwhile, the N fertilizer rate was reduced 59% and 72% in W/M-M and M compared to Con.W/M, respectively. There were no significant differences in net economic returns between Con.W/M and W/M-M across the 6-year period. In the 6 years, no significant economic loss was observed between Con.W/M and M except in the 2008-2010 rotation. The W/M-M and M systems showed great potential to reduce water and N application and achieve groundwater use balance, and thus should be considered for economic and sustainable agricultural development in the NCP.     

初始氨氮浓度对钝顶螺旋藻生长及其去除率的影响

螺旋藻是一种经济价值很高的微藻,研究氨氮对钝顶螺旋藻生长及其去除水中氨氮效率的影响,探讨其在废水处理中的可行性具有重要意义。结果表明,以硫酸铵作为氮源时,钝顶螺旋藻的对数期一般在4～6 d,随着氨氮浓度的升高对数期略有提前。钝顶螺旋藻对硫酸氨的耐受浓度为0.5 g/L,相应的氨氮浓度为106 mg/L。培养4～6 d时氨氮浓度下降幅度最大,培养结束时氨氮去除率为67.7%～82.5%,当硫酸铵投加量为0.4 g/L时,氨氮去除率最高,达82.6%。因此,螺旋藻可用于去除废水中的氨氮,具有很好的应用前景。     

Effect of substrate concentration on the bioleaching of heavy metals from sewage sludge

IntroductionTheproductionofexcesssewagesludgeisincreasingrapidlywiththewidespreadofwastewatertreatment,whichcausesseriousproblemtothedisposalofsewagesludge .Landapplicationofsewagesludgeisthemostcost effectiveandfeasibleutilizationapproachatpresent.Howeve…     

Preliminary techno-economic analysis of three typical decentralized composting technologies treating rural kitchen waste: a case study in China

● Decentralized composting (DC) is a profitable KW treating technology. ● SAC and BEC were economically attractive in rural area, while HDC was unprofitable. ● KW handling subsidy plays a vital role in making DC profitable. ● SAC and BEC have great potential in promoting rural KW treatment. This study was designed to evaluate whether the decentralized rural kitchen waste (KW) composting technologies used in China can be widely applied. To this end, we completed a techno-economic analysis of three typical types of KW compositing, namely solar-assisted (SAC), bio-enhanced (BEC), and heat-dewatering composting (HDC). These evaluations revealed that all three technologies produce composting products that meet China’s organic fertilizer standard and that both SAC and BEC are economically self-sustaining and generate net profits (18824.94 and 17791.52 US$/a) and positive net present values (32133.11 and 25035.93 US$). Subsequent sensitivity analysis demonstrated that the KW-handling subsidy plays a critical role in making decentralized composting economically attractive. Based on these analyses, we believe that reducing the coverage area of SAC, reducing the operating cost of BEC and HDC, upgrading composting products, and strengthening secondary pollution control would aid in supporting the technological improvement of these processes. Moreover, providing appropriate subsidies and promulgating specific standards and policies for KW fertilizer are key strategies for decentralized rural KW composting management.     

基于SWAT模型的湘江永州流域非点源氮磷污染特征分析

为精准治理流域非点源氮磷污染,基于SWAT模型,运用本地区第二次全国污染源普查数据和2000—2019年流域水文、水质数据,开展湘江永州流域非点源氮磷污染模拟。结果表明：湘江永州流域建立的SWAT模型具有较好的模拟效果,流域2005—2019年的总氮月均污染负荷为383.40～17 998.70 t/m;总磷月均污染负荷为64.62～567.86 t/m,总氮和总磷各月污染负荷均与各月降雨量呈显著相关关系;农田和林地是本流域总氮、总磷污染负荷总量最大的2种用地类型,但两者之间单位面积输出的污染负荷强度却相反,林地对流域水污染防控具有正面效应,农田种植面源污染是非点源氮磷污染治理的重点。     

15年实测氮沉降下竹仙洞小流域土壤酸化研究

以2000—2015年珠海竹仙洞水库小流域湿地松林、台湾相思林和灌木丛为样本,对其土壤属性指标进行相关性分析和主成分分析。结果表明,经过15年自然演替,3个群落的土壤可交换酸度呈下降趋势,其中台湾相思林和灌木丛酸度降低达到显著或极显著水平,受Al³⁺含量影响较大;3个群落的可交换Mg²⁺、K⁺、Na⁺在两种土层均有不同程度的显著下降,而可交换Ca²⁺的变化仅在台湾相思林中显著;总氮、总碳含量均呈上升趋势。主成分分析显示,台湾相思林的生物量丰富、土壤腐殖质多,固氮作用强,故对氮沉降的酸缓冲能力更强。