非饱和土壤中甲苯与三氯乙烯迁移过程和生物降解作用的耦合模拟

三氯乙烯(TCE)是常见的地下水污染物,通常对需氧生物降解具有抵制作用,在另一种化合物(如甲苯)的存在下,可以与之发生共同新陈代谢。利用实验室土柱对 TCE 和甲苯的耦合迁移和生物降解作用进行研究和建模。根据 Monod 动力学原理,建立甲苯的生物降解与微生物生长的关系;根据 Michaelis-Menten 动力学原理,描述TCE 的生物降解,并予以修正,以解释酶水平的变化。TCE 的生物降解模拟为甲苯降解速率的质量分数。生长和衰变都引入方程以模拟微生物群动力学过程。除初始生物量外,从独立的土壤分批实验获取描述两种降解函数的一套参数。物理参数从无微生物的土柱中得到。从柱室的入口到出口,初始生物量减少。甲苯在土柱中完全降解,大部分降解发生在最接近柱室的入口处。由于 TCE 比甲苯扩散快,变化速率慢,大量的 TCE 没有降解。

Biochar and sugar cane filter cake interaction on physical and hydrological soil properties under tropical field conditions

Biochar is known for its effects on carbon sequestration and soil fertility.However,there is a lack of information about its effects on soil physical and hydraulic properties for tropical soils.We assessed the effects of biochar(BC)plus sugar cane filter cake(FC)rate,and time of interaction on soil physical and hydraulic properties under humid tropical conditions.For this purpose,a field experiment was installed at a loamy sandy soil with five treatments and four replicates:control(only soil),25 Mg ha^(−1) sugar cane filter cake,and 25 Mg ha^(−1) sugar cane filter cake plus 6.25,12.5,and 25 Mg ha^(−1) Miscanthus biochar,respectively,two soil depths(0-10 and 10-20 cm)and two times of interaction(9 and 18 months).Physical prop-erties(aggregate stability,bulk density,total porosity,pores size distribution)and hydraulic properties(soil water holding capacity,hydraulic conductivity,plant-available water holding capacity)were measured after nine and eighteen months.The bulk density decreased slightly,and the porosity increased after nine months,for the biochar plus sugar cane filter cake(both 25 Mg ha^(−1)).After 18 months,biochar plus filter cake interaction increase micropores,aggregate stability,and plant-available water content.Saturated hydraulic conductivity was not influenced by sugar cane filter cake.However,biochar significantly reduced saturated hydraulic conductivity when combined with sugar cane filter cake after 18 months.We concluded that sugar cane filter cake in combination with biochar modified the pore size distribution,slightly increased plant-available water holding capacity,and significantly decreased saturated hydraulic conductivity.

Microwave-assisted combustion to produce benzene polycarboxylic acids as molecular markers for biochar identification and quantification

Biochar is a promising carbon dioxide removal(CDR)technology for climate change mitigation.Current procedures for its determination are lengthy,labor-intensive,and difficult to conduct.Benzene polycarboxylic acids(BPCA)are the most promising molecular markers for identification and quantification of biochar and its quality as they specifically represent the stable polyaromatic backbone of biochar.Therefore,using the BPCA method,its stability and,thus,its C sequestration potential could be used for CDR accounting.The current BPCA method relies on a specific high-pressure digestion apparatus,which is not available around the world.Therefore,the aims of the present work were(i)to compare the conventional high-pressure nitric acid oxidation with a microwave-assisted digestion technique and optimize the oxidation conditions in such a way that previous results are comparable with future ones,and(ii)to significantly reduce the digestion time of soil samples of 8 h and to develop a suitable routine method that produces comparable and reproducible results.For this purpose,soil and control sample series were prepared for different temperature-time-program.Obtained results were compared with the values of the conventional method both for individual samples and for the whole dataset separately.To ensure the representative-ness of the results,in addition to various soil samples with different properties,we included two reference materials into our data set,one without biochar(wheat flour)and a biochar sample.Our results showed that conventional nitric acid oxidation in the BPCA determination at 170°C and 8 h can be substituted by digestion in a microwave reaction system(CEM Mars6)at 190°C and 1 h.Our results further showed that this condition needs to be strictly matched,because,otherwise,over-or underestimation of biochar quantity and/or quality will be the consequence.The goal of a less time-consuming BPCA extrac-tion from soil samples was achieved by reducing the extraction time from 8 to 1 h using the microwave-assisted method.However,one disadvantage of the new method is that five times more sample material and chemicals are needed for further BPCA analysis,compared to the original method.

Effect of biochar fertilizers on amino acid variability of Secale cereale and Lupinus angustifolius

Little is known on the effects of biochar on N uptake and amino acid variability in crops such as winter rye and narrow-leafed lupine despite the fact that amino acids are important indicators,for food quality and plant stress.N uptake of both crops showed contrasting results when treated with different biochar fertilizers.Total amino acid contents referred to total nitro-gen generally tend to decrease in rye grains in the presence of biochar;whereas lupine seeds were more or less unaffected by biochar combined with mineral fertilizer or compost.In lupine seeds,total amino acid contents significantly increased when biochar was mixed with digestate but decreased when mixed with fermented digestate.Lysine,one of the most limiting amino acids in cereals,reached the recommended value of 4 g kg^(−1) in rye grain for most biochar fertilizers.In lupine seeds,lysine decreased when biochar had been applied but were still in the recommended range when used as animal feed.Proline,an indicator for plant stress,significantly decreased(−49%)in rye when 2 Mg biochar ha^(−1) was added in combination with mineral fertilizer.In contrast,proline increased when biochar was added to organic(digestate and compost)fertilizers(up to 43%).Further biochar research should focus much more on food quality,which is a key challenge for global food production.

Improving ITS sequence data for identification of plant pathogenic fungi

Plant pathogenic fungi are a large and diverse assemblage of eukaryotes with substantial impacts on natural ecosystems and human endeavours.These taxa often have complex and poorly understood life cycles,lack observable,discriminatory morphological characters,and may not be amenable to in vitro culturing.As a result,species identification is frequently difficult.Molecular(DNA sequence)data have emerged as crucial information for the taxonomic identification of plant pathogenic fungi,with the nuclear ribosomal internal transcribed spacer(ITS)region being the most popular marker.However,international nucleotide sequence databases are accumulating numerous sequences of compromised or low-resolution taxonomic annotations and substandard technical quality,making their use in the molecular identification of plant pathogenic fungi problematic.Here we report on a concerted effort to identify high-quality reference sequences for various plant pathogenic fungi and to re-annotate incorrectly or insufficiently annotated public ITS sequences from these fungal lineages.A third objective was to enrich the sequences with geographical and ecological metadata.The results-a total of 31,954 changes-are incorporated in and made available through the UNITE database for molecular identification of fungi(http://unite.ut.ee),including standalone FASTA files of sequence data for local BLAST searches,use in the next-generation sequencing analysis platforms QIIME and mothur,and related applications.The present initiative is just a beginning to cover the wide spectrum of plant pathogenic fungi,and we invite all researchers with pertinent expertise to join the annotation effort.