Fractionation of soil humic acids by preparative polyacrylamide gel electrophoresis in the presence of concentrated urea

To separate soil humic acids (HAs) into their constituents and characterize them, polyacrylamide gel electrophoresis (PAGE) was carried out in the presence of 7 M urea using a preparative electrophoresis system. Two types of soil HAs were fractionated into nine fractions by PAGE. The dark-colored constituents were recovered from the electrophoretic fractions by precipitation on acidification, and the brown-colored constituents dissolved in the acidic solution of fast-moving fractions were recovered by adsorption onto DAX-8 resin. High-performance size-exclusion chromatography (HPSEC) confirmed that the constituents of the HAs were separated based on their molecular size by PAGE. The dark-colored constituents exhibited higher degrees of humification than did the corresponding unfractionated HAs, except for the constituents remaining in the electrophoretic gels at the end of electrophoresis. Diffuse reflectance infrared spectroscopy revealed that the chemical properties of the dark-colored constituents changed regularly: the content of carboxyl groups decreased and the proportions of proteinous, aliphatic and polysaccharide moieties increased with increasing molecular size. The humification degrees of the constituents adsorbed onto DAX-8 resin were considerably lower than those of the corresponding unfractionated HAs. The chemical properties of the DAX-8-adsorbed constituents were different from those of the dark-colored constituents. Observation of electrophoretic fractions under blue light (470 nm) and HPSEC with fluorescence detection at an excitation wavelength of 460 nm and an emission wavelength of 520 nm showed that green fluorescent substances were largely concentrated in the smallest molecular size fractions and were partitioned into both the dark-colored precipitates and DAX-8-adsorbed fractions. The proportion of organic carbon recovered by precipitation and adsorption onto DAX-8 resin was 45–63%, indicating that substantial parts of the HA constituents were missing. The unrecovered constituents were considered to be acid-soluble, nearly colorless substances. The dissociation of the acid-soluble constituents from the acid-insoluble dark-colored constituents during the preparative PAGE of soil HAs was ascribed to disruption of hydrogen bonding and hydrophobic interactions caused by concentrated urea.     

Occurrence of Polycyclic Musks in Sewage Sludge and their Behaviour in Soils and Plants. Part 1: Behaviour of Polycyclic Musks in Sewage Sludge of Different Treatment Plants in Summer and Winter (5 pp)

Background, Aim and Scope   Part 1: Behaviour of Polycyclic Musks in Sewage Sludge of Different Treatment Plants in Summer and Winter Part 2: Investigation of Polycyclic Musks in Soils and Plants -  Preamble. In Part 1 of the study, screening tests were performed to investigate the occurrence of PCMs in sewage sludges. For a preliminary risk assessment, further information is needed about their behaviour in the terrestrial environment. Hence, Part 2 examined the adsorption of PCMs to soil, their dissipation and leaching in soil and their uptake by plants. Background, Aim and Scope   Polycyclic Musks (PCMs) enter the environment via the waste water system. Because of their persistence, they can accumulate in different matrices like sewage sludge or biota. By the use of sewage sludge as a fertilizer, PCMs are transferred to agricultural soils. Therefore, in Part 1 of the study, screening tests were performed to investigate the occurrence of PCMs in sewage sludge. For a preliminary risk assessment, further information is needed about their behaviour in the terrestrial environment. Hence, Part 2 of the study examined the adsorption of PCMs to soil, their dissipation and leaching in soil, and their uptake by plants. Materials and Methods: In the screening study, samples of activated sewage sludge were taken both in summer and in winter at 21 treatment plants. In order to get an overview of the contamination situation, sampling covered different types of treatment plants (in rural, urban, industrial areas). Analytical methods for the determination of HHCB, AHTN, ADBI, ATTN, AHDI and ATII in the sludge samples were developed and applied. Results: The analytical screening of PCMs showed their presence in activated and dried sewage sludge samples. HHCB and AHTN represented about 95% of the PCMs investigated. Their concentrations in the activated sludge samples varied between 2.9 and 10.4 mg/kg dry mass (dm) and 1.1 to 4.2 mg/kg dm, respectively. Although different types of sewage treatment plants were investigated, similar PCM levels were found, showing the widespread input of these compounds into domestic waste water. Discussion: PCM concentrations in activated sludge varied widely. The variation drops substantially when concentrations are related to the varying dry mass. In dehydrated sludge, PCM concentrations were up to 24 mg/kg dm for HHCB and up to 6.9 mg/kg dm for AHTN. These high values are comparable to those obtained in other investigations analysing PCMs. If the degradation of organic mass during anaerobic decomposition is included in the evaluation, the figures obtained are comparable to those for activated sludge. Elimination in sewage sludge was higher in summer than in winter. Therefore, the contamination of the sludges in winter reached higher levels compared to the summer. Conclusions: The results show that PCMs are widespread contaminants in sewage sludge. Recommendations and Perspectives: PCM should be considered in a risk assessment as potential contaminants of sewage sludge destined for agricultural use. Due to the high PCM levels in sewage sludge, further investigations into the degradation and elimination behaviour in sewage sludge have to be carried out, including that involving PCM metabolites such as lactone derivatives.     

塔里木河下游环境退化的因子分析

 为了研究土地荒漠化及其影响因子,对塔里木河下游沿河道布设的39个样地,进行环境退化因子分析。通过数学变换,8个观测指标被转换为3个综合指标(水分指标、沙化指标、盐化指标)。根据本地区的实际,对3个综合指标进行环境解释。依据这3个主分量的贡献率,计算塔里木河下游39个样地的因子得分,并据此进行环境退化程度(荒漠化)的分类。从因子得分结果看,塔里木河下游地区呈明显的随距大西海子水库距离的增加荒漠化程度加重的特点,引起这一结果的主要原因,是水、盐条件逐渐恶化带来的植被衰败。从分类的结果看,与该地区的实际基本相符合。这说明因子分析的方法综合了多指标的综合影响,划分的结果更加客观。     

土壤侵蚀退化研究

土壤退化是全球性的重大环境问题之一,直接威胁人类的生存。在引起土壤退化的诸因素中,土壤侵蚀是最普遍和最重要的因素。在前人土壤侵蚀退化研究成果的基础上简单回顾了其发展现状,重点综述了土壤侵蚀退化机理,并针对性地提出了土壤侵蚀退化防治措施。     

我国土壤污染退化状况及防治对策

土壤污染退化已成为我国乃至全球性土壤退化的主要表现形式之一。本文在分析我国土壤资源污染退化状况和发展态势的基础上,着重分析了土壤污染退化对食物安全和生态环境效应的影响,并探讨了其原因,提出了防治我国土壤资源污染退化的对策。     

耕地生产力隐性退化遥感监测与影响因素分析

以江苏省永久耕地为例,基于2001—2019年中分辨率成像光谱仪(Moderate resolution imaging spectroradiometer, MODIS)遥感影像,开展耕地生产力隐性退化遥感监测和影响因素分析。BFAST(Breaks for additive seasonal and trend)算法用于建模历史时期耕地生产力变化的预期行为,并以此为基准判断监测时期耕地生产力是否存在隐性退化风险。基于地理探测器,从3个准则层的8项指标变量对耕地生产力隐性退化进行了主导影响因素探测和因子交互分析。研究结果表明：江苏省存在生产力隐性退化的耕地比例为21.9%,具有显著的空间差异。西北地区的徐州市、宿迁市的耕地生产力隐性退化比例最高,分别为47.2%和43.4%,且表现出聚集性。东南地区的苏州市、无锡市和南通市的耕地生产力隐性退化比例较低,均不足10%。因子探测分析表明外流人口数量、种植业从业人员数量和农业机械化总动力3项指标对江苏省耕地生产力隐性退化的解释力最强。多因子交互耦合后,人口因素与生产条件解释力增强最为显著。耕地生产力隐性退化的地域分异类型划分为生产条件约束型...     

棒曲霉素控制技术及检测方法研究进展

系统阐述了棒曲霉素的的理化性质,分析了国内外对棒曲霉素检测、去除及降解技术研究的现状及存在问题,提出了我国目前应着力解决的关键技术性问题:①建立食品中棒曲霉素的全程控制技术体系,从源头做起,在食品生产的不同阶段嵌入关键控制技术,实现全程监测、预警及控制;②建立棒曲霉素的现场快速检测方法及监测技术体系,为实时控制提供基础数据;③进一步研究完善食品中棒曲霉素的安全去除技术方法;④研究开发食品中棒曲霉素安全的降解技术,构建降解与去除相耦合的新型工艺技术体系。     

复合磷酸盐对鲜切牛肉肌球蛋白凝胶保水性的影响

研究了焦磷酸钠(SAP)、三聚磷酸钠(STP)、六偏磷酸钠(HMP)及复合磷酸盐对牛肉肌球蛋白凝胶保水性的影响。结果显示,当复合磷酸盐中SAP,STP和HMP的质量比为2∶1∶1,添加量为0.2%时,可获得最佳的感官品质和较好的凝胶保水性,影响凝胶保水性因素的主次顺序为SAP>HMP>STP,且SAP和HMP对凝胶保水效果具有显著影响。     

辐照交联热收缩套管凝胶含量的测定

辐照剂量的大小直接影响着热收缩套管的扩张难易程度及热收缩套管收缩性能,我们在通常的情况下一般采用测凝胶含量的方法来测定热收缩套管的吸收剂量(即辐照的好坏)。文章讲述了剂量对凝胶含量及热收缩套管的收缩倍率的影响。     

Defining the validity of a biochemical index of soil quality

 The native soils of Galicia (NW Spain) exhibit a biochemical equilibrium such that total soil N is a function of five biochemical and microbiological parameters: microbial biomass C, mineralized N, phosphomonoesterase, β-glucosidase and urease activities. To investigate whether the ratio of the total N calculated from biochemical soil properties (Nc) and the total N as measured by the Kjeldahl method (Nk; Nc/Nk) can be used as an index of soil quality, we determined these variables and consequently the ratio in three kinds of disturbed soils: an artificially Cu-contaminated soil, two lignite mine soils, and a number of arable soils. In none of the studied soils did the individual biochemical parameters respond consistently to the factors influencing soil quality, but in all cases soil degradation was reflected by the Nc/Nk value, which differed more or less markedly from 100%. Nc/Nk can therefore be used for the rapid evaluation of soil degradation, since it distinguishes among biochemically balanced soils, soils in a transient state of high microbiological and biochemical activity and degraded soils. It can also serve as a reliable basis for the rapid calculation of the "ecological dose" (ED₅₀) of soil pollutants. The use of Nc/Nk as an objective index of the biochemical quality of soils is recommended. Received: 20 December 1998