Living with floating vegetation invasions

Invasions of water bodies by floating vegetation, including water hyacinth (Eichhornia crassipes), are a huge global problem for fisheries, hydropower generation, and transportation. We analyzed floating plant coverage on 20 reservoirs across the world’s tropics and subtropics, using > 30 year time-series of LANDSAT remote-sensing imagery. Despite decades of costly weed control, floating invasion severity is increasing. Floating plant coverage correlates with expanding urban land cover in catchments, implicating urban nutrient sources as plausible drivers. Floating vegetation invasions have undeniable societal costs, but also provide benefits. Water hyacinths efficiently absorb nutrients from eutrophic waters, mitigating nutrient pollution problems. When washed up on shores, plants may become compost, increasing soil fertility. The biomass is increasingly used as a renewable biofuel. We propose a more nuanced perspective on these invasions moving away from futile eradication attempts towards an ecosystem management strategy that minimizes negative impacts while integrating potential social and environmental benefits.Electronic supplementary materialThe online version of this article (10.1007/s13280-020-01360-6) contains supplementary material, which is available to authorized users.     

三种化合物浸泡处理对石棉晶格结构和表面电荷的影响

为了研究经柠檬酸铝、混合稀土或亚硒酸钠浸泡处理温石棉对温石棉晶格结构和表面电荷的影响,用不同浓度的柠檬酸铝、混合稀土或亚硒酸钠溶液浸泡温石棉1小时后,通过透射电镜测定其衍射环直径的大小,分析石棉晶格结构的改变,并利用石棉纤维吸附亚甲蓝能力的测定方法,分析温石棉表面电荷。结果显示,用三种化合物处理石棉后,其衍射环直径均增大,而且用三种化合物处理后的石棉对亚甲蓝的吸附能力均明显降低,并且随着化合物剂量的增加其降低愈明显。上述结果表明,用三种化合物处理石棉,均可改变石棉的晶格结构,且可能减少其表面电荷。     

区域可持续发展的人地关系探讨

本文从人的生存空间、活动空间以及人的生存活动、社会生产活动与自然环境的物质、能量、信息交流来论述人地关系，并且从人的生存与发展需求的角度讨论了人地关系矛盾的内涵与外在表现，进而提出了实现区域可持续发展的一般原则     

Yttrium Normalisation: a New Tool for Detection of Chromium Contamination in Soil Samples

The measurement of chromium and yttrium concentration could give a chance to detect 5–10 times less chromium contamination in soil by using the yttrium normalisation method. The principle of the method is the following: elements such as chromium and yttrium exist naturally in the soil in a strongly bonded form. Therefore, in a noncontaminated area there should be a close correlation between the yttrium and chromium concentrations. If the measured Cr concentration in a sample is not on the Cr–Y trend line then the distance of plotted point from the line indicates the amount of anthropogenic chromium. Anthropogenic chromium can be detected only in the case when the contamination does not contain yttrium. This theory was tested in an agricultural–toxicological field experiment where Cr(VI) was added to the soil. Applying the yttrium normalisation method a much smaller anthropogenic effect was detected than by other evaluation methods.     

螺旋藻对稀土铒离子的吸附特性研究

以螺旋藻为吸附剂,对模拟矿山废水中的稀土Er³⁺进行吸附特性研究.研究了被处理液的pH值、螺旋藻的剂量、初始Er³⁺浓度和吸附时间等因素对吸附过程的影响.通过Freundlich,Langmuir,Redlich-Peterson和Dubinin-Radushkevich等温吸附模型,以及伪一级、伪二级、Elovich方程和颗粒内扩散动力学模型,对该过程的吸附动力学和热力学规律进行探讨,以了解该吸附过程的机理.吸附结果显示：当被处理液的pH值为5、螺旋藻的剂量为2.0g/L、吸附温度为298K、初始Er³⁺浓度为100mg/L和吸附时间为60min时,螺旋藻对模拟矿山废水中Er³⁺的吸附去除率为90.73%,通过HNO₃解吸附,回收率可达97.12%,表明螺旋藻的吸附速率快、吸附和回收效果较为理想.研究表明：该过程的吸附动力学行为符合伪二级动力学模型（R²>0.99）,主要受化学吸附控制,且吸附等温线能较好用Langmuir方程进行模拟（R²>0.9）,属于自发吸热的吸附过程.     

稀土元素对38CrMoAl钢离子渗氮工艺的影响

目的缩短38CrMoAl钢离子渗氮工艺周期。方法在离子渗氮过程中,添加稀土金属镧(La)及稀土镧铈合金(La-Ce)。通过显微硬度仪、光学金相显微镜、扫描电镜及能谱分析仪对于离子氮化层的表面硬度、脆性、微观显微组织、稀土元素含量进行检测分析,并和常规离子渗氮工艺进行对比研究。结果在离子渗氮工艺过程中,添加稀土金属镧(La)及镧铈合金(La-Ce)后,氮化层表面硬度提高约130～200 HV,渗氮速度提高了15%～30%,氮化周期显著缩短。稀土催渗离子渗氮层的脆性均为Ⅰ级,比常规离子渗氮更优异。同时,稀土元素的渗入细化了晶粒,使得渗层氮化物组织致密、呈弥散分布,优化了氮化层的相结构组成。结论稀土元素的加入可以有效提高渗氮层的表面硬度和脆性等级,改善了氮化层性能。同时缩短了离子渗氮工艺周期。     

离子型稀土尾矿残留铵缓释性分析

为探究尾矿残留NH₄⁺的缓释性,以江西信丰离子型稀土矿为研究对象,柱浸制备浸出尾矿,去离子水淋洗尾矿.按照淋洗→封存→再淋洗的步骤,考察了淋洗尾矿不同含水率（1.3%,15%,35%,250%）,不同封存时间（15,30,60,120,180,195,210,240d）和不同传质机制（对流、扩散）下NH₄⁺的淋出量.结果表明：尾矿再淋洗仍能淋出NH₄⁺,NH₄⁺淋出量受含水率、封存时间和传质方式影响;含水率≥15%时,NH₄⁺淋出量整体随时间推移而递增;同时间下,NH₄⁺淋出量整体随含水率增大而增大;其他条件相同时,对流传质下NH₄⁺淋出量大于扩散.尾矿再次淋出的NH₄⁺是可交换态NH₄⁺向水溶态NH₄⁺转化的结果.     

An experimental study on shrinkage of earth plaster with natural fibres for straw bale buildings

In this paper, a series of laboratory tests on shrinkage of plaster materials are presented. The plaster materials consist of cohesive soil, sand and different natural fibres. Three types of fibres, wheat straw, barley straw and wood shavings, were used as reinforcement in the tests. The shrinkage behaviour of earth plasters was studied by laboratory tests for different compositions and under different curing conditions. The specimens of plaster material were dried under a constant temperature of 30, 50 and 70°C, respectively. The effect of the following factors on shrinkage was investigated: temperature, soil composition, fibre type and fibre content. It was established that shrinkage crack formation decreases with increasing fibre content and increases with increasing soil content. In general, it was also found that lower curing temperature and higher fibre content are to be preferred to improve the performance of earth plasters.     

我国黑土退化研究现状与展望

黑土是一种腐殖质层厚,质地松散,肥力很高,孔隙比较大而透水性差,粘粒含量高,适于耕作的淋溶土。但是随着人类社会的发展,在缺乏保护和可持续利用意识、急功近利思想影响下,黑土遭到过度垦殖和掠夺式经营,人类对其活动范围远远超过了其再生能力,导致有机质含量减少,肥力下降,孔隙比减小,保水持水能力降低, 土壤板结,黑土严重退化。在国家振兴东北老工业基地和防止黑土退化及加强黑土保护之际,通过对黑土分布状况和黑土退化研究现状的分析,总结出黑土退化方式,揭示了其退化的主要原因,提出了防止黑土地退化和保护黑土地的措施,在现有研究的基础上提出黑土退化研究的新方向,希望能为黑土资源可持续利用和进一步研究起到抛砖引玉的作用。     

NdFeB酸法生产Nd_2O_3废水的处理与资源化研究

任何浓度的盐酸都可以与水共沸,根据这一原理,采用蒸发浓缩的方法回收高铁含量的草沉废水中的盐酸和氯化亚铁。石灰中和法适用于脱除低铁含量的洗水中的Fe2+。本方法在NdFeB酸法生产Nd2O3废水的工业化处理实践中获得了良好的效果,废水中的盐酸回收为稀盐酸,废水中的铁回收为氯化亚铁晶体产品。