Phospholipid fatty acid composition of a 2,4,6-trinitrotolune contaminated soil and an uncontaminated soil as affected by a humification remediation process

Analysis of phospholipid fatty acids (PLFAs) was performed to investigate effects of 2,4,6-trinitrotoluene (TNT) contamination and soil remediation on microbial biomass and community structure. A TNT-contaminated and an uncontaminated soil from a former ammunition plant were analysed before and after a humification/remediation process. TNT contamination reduced microbial biomass but indicated only minor differences in PLFA composition between the contaminated and uncontaminated soils. The humification process increased microbial biomass and altered soil PLFA patterns to a larger degree than did TNT contamination.     

Mineralisation and humification of plant matter in soil samples as a tool in the testing of soil quality

Since life is inevitably dependent on the assimilation and dissimilation of carbon, and since most of the organic carbon is bound in soil humic matter, the mineralisation and humification of plant carbon in soil should be monitored, so as to evaluate soil quality and avoid ecological risks. For this reason we suggested an incubation test of thirty days in duration with soil samples amended or not with lucerne meal as a source of plant carbon. During the incubation period, CO₂ release is to be measured repeatedly, and thereafter contents of humic acids (HA) and fulvic acids (FA) should be estimated and compared with those determined in the original soil samples. Our results obtained with samples from non-fertilized or long-term (?>?40 years) fertilized plots of two field trials indicate that fertilization by NPK?+ farm yard manure resulted in (i) a slight enhancement of C mineralisation, i.e., CO₂ release from soil, and (ii) a significant increases of HA and FA contents. Soil samples from a reclaimed mine spoil, and either fertilised or not with sewage sludge did not show distinct differences in the same parameters. The practicability of the incubation test as a tool in the monitoring of soil quality should be further proved using samples from differently affected soils.     

Determination of biological stability in compost: A comparison of methodologies

Biological [dynamic respiration index (DRI); chemical humification indexes: humification index (HI), degree of humification (DH) and humification rate (HR); and thermoanalytical (thermostability index, R₁ and a labile fraction)] indexes were used to assess compost stability of 15 end products. By use of these three techniques independent assessment of compost stability was made possible. Evidence of unstable materials was found where labile, easily biodegradable, and non-humified organic fractions were present. The DRI was used as a reference index for biological stability, and no significant correlation was observed between DRI and the humification indices (HI, DH, HR) and the thermogravimetry index (R₁). On the other hand, significant correlation was observed for DRI vs. non-humified carbon (NHC), which was determined using the chemical method and the labile fraction determined by thermogravimetry, as well as for NHC vs. “labile fraction”. These fractions represent labile, easily biodegradable, and non-humified organic matter. Significant correlations were also observed between the three above mentioned measurements and TEC, suggesting that this fraction is mainly formed of the easily degradable organic fraction. These results suggest that the integrated use of biological, chemical, and thermoanalytical methods could represent a useful tool in differentiating stabilized composts from non-stabilized ones, and it could provide more reliable information for both managerial and sanitary health aspects involved in good agricultural practice.     

砂土中有机物质腐解与有机质调控

通过砂滤管和尼龙网袋法研究了有机物料在砂土的腐殖化和矿质化规律,对该土壤有机质培肥及调控提出了建议。研究表明:供试的几种物料总的分解速率趋势为:玉米秸杆>小麦秸杆>鸡粪>牛粪>猪粪。砂土有机质的矿化速率为3.06%;同时发现两种研究方式下,土壤有机质含量和活性有机质含量二者之间具有明显的相关性。     

Microbial biomass and organic matter turnover in wetland rice soils

A decline in rice yields has been associated with intensification of rice production. In continuously irrigated systems this has been attributed to a decline in soil N supply. Nutrient mineralisation and immobilisation is constrained by the quantity and nature of the organic substrates and the physico-chemical environment of the soil system itself. A flooded soil is very different from an aerobic one; electron acceptors other than oxygen have to be used. The transition to continuously anaerobic conditions associated with the intensification of wetland rice systems affects their organic matter turnover and may adversely affect their productivity.     

有机物料腐植酸和碳氮比对有机肥品质的影响

本试验通过对7种不同物料的总氮（N）、有机质（OM）和总腐植酸（HA）测定,计算腐殖化率（HR）和碳氮比（C／N）。结果表明,糠醛渣和风化煤有机质含量较高,分别为78．61％和85．84％,C／N比也高,腐殖化率则较低,而沼渣、污泥、草炭有机质含量在44．63％～55．03％之间,其C／N低,但腐殖化率较高,特别是草炭,腐殖化率在90％左右。     

Carbon and nitrogen transformation during composting of sweet sorghum bagasse

Two types of compost, consisting of sweet sorghum bagasse with either sewage sludge or a mixture of pig slurry and poultry manure, were studied in a pilot plant using the Rutgers system. The total degradation of the piles as determined by the weight loss of organic matter during the bio-oxidative and maturation phases accounted for 64% of the organic matter applied and followed a first-order kinetic function. Concentrations of total and organic N increased during the composting process as the degradation of organic C compounds reduced the compost weight. Losses of N through NH₃ volatilization were low, particularly in the compost with sewage sludge due to pH values of <7.0 and the low temperatures reached in the compost during the first 2 weeks. The C:N ratio in the two composts decreased from 24.0 and 15.4 to values between 12 and 10. Increases in cation exchange capacity and in fulvic and humic acid-like C revealed that the organic matter had been humified during composting. The humification index, the C:N ratio, fulvic:humic acid-like C, and cation exchange capacity proved to be the most suitable parameters for assessing the maturity of these composts.     

Isoelectric focusing of humic substances on ultrathin polyacrylamide gels: evidence of fingerprint performance

Differentiated interactions between humic substances and isoelectric focusing-carrier ampholytes were demonstrated by comparing specific absorption ratios from the supernatant after precipitation with 2 M HCl and with acid ampholytes (pH 2–4) containing both carboxylic and sulphate groups. An increasingly stronger interaction was observed when comparing soil humic substances to those of synthetic origin or those extracted from young reclaimed soil material. Electrofocusing of the humic substances under study revealed a fingerprint-like quality; the band patterns observed were consistent with the concept of three main fractions.