Degradation of certain aromatic compounds by rhizobia

The ability of 22 strains of Rhizobium to degrade catechol, protocatechuic acid, p-hydroxybenzoic acid and salicylic acid all at 1 mm concentration was examined. In the presence of 4.8 mm Na-glutamate, all rhizobia tested degraded catechol (99–100%), p-hvdroxybenzoic acid (79–99%), protocatechuic acid (81 97%) and salicylic acid (20–83%).The concentration of Na glutamate in the medium affected the degradation of the phenolic compounds at 1 mm concentration. Increased glutamate favoured degradation of p-hydroxybenzoic and salicylic acids but had little effect on catechol. Degradation of protocatechuic acid was inhibited by increased glutamate concentration.Rhizobium phaseoli 405 grown with 8.0 mM Na-glutamate, directly cleaved catechol and protocatechuic acid. p-Hydroxybenzoic acid was converted to protocatechuic acid before ring cleavage. Salicylic acid was converted to gentisic acid before further oxidation. O₂ uptake experiments showed that R. phaseoli 405 grown with p-hydroxybenzoic acid was adapted to this compound and protocatechuic acid. A lag of 30 min was required for catechol and salicylic acid.     

Automatic method for the determination of Folin-Ciocalteu reducing capacity in food products

In the present work, an automatic flow procedure based on multi-syringe flow injection analysis was developed for the assessment of Folin-Ciocalteu reagent (FCR) reducing capacity in several types of food products using gallic acid as the standard. Different strategies for mixing of sample and reagent were tested (continuous flow of FCR, merging zones, and intercalated zones approaches); lower reagent consumption and higher determination throughput were attained for the merging zones approach (100 microL of sample+100 microL of FCR). The application of the proposed method to compounds with known antioxidant activity (both phenolic and nonphenolic) and to samples (wines, beers, teas, soft drinks, and fruit juices) provided results similar to those obtained by the conventional batch method. The detection limit was 0.6 mg L-1, and the determination frequency was about 12 h-1. Good repeatability was attained (RSD<1.3%, n=10).     

Antioxidizing potency of phenol compounds in olive oil mill wastewater

The antioxidizing potency of phenol compounds contained in olive oil mill wastewater (OOMWW) has been elucidated. Commercially available phenol standards at varying concentrations and the Rancimat oxidation test have been used. Refined purified olive oil was utilized as an oxidation lipid substrate. Synthetic antioxidants, such as 2,3-tert-butyl-4-hydroxyanisole (BHA), 3,5-di-tert-butyl-4-hydroxytoluene (BHT), l-ascorbic acid, and gallates (commonly used as food preservatives), and other known chemicals endowed with antioxidizing properties have been employed as reference compounds. The OOMWW phenol compounds have been classified into different groups depending on their antioxidizing potency. This was significantly affected by the tested concentrations of the standards. Mixtures of phenol standards and other antioxidants (l-proline, chlorophyll a, chlorophyll b, and alpha-, gamma-, and delta-tocopherol) have also been tested. Many phenol compounds present in OOMWW showed antioxidizing potency higher compared to that of the less safe synthetic antioxidants and could therefore replace these in the industrial preservation of food items. They could also be used in combination with other natural antioxidants (e.g., tocopherols). In fact, some mixtures of antioxidants, owing also to the synergistic phenomena, showed strong antioxidizing potency.     

Utilization of mineral nitrogen in the subsoil by winter wheat

Uptake of nitrogen from the subsoil (30–200 cm) by winter wheat has been measured in field experiments on deep loess-parabrown soils in northern Germany and at Rothamsted (England) for different crop rotations and manuring schemes. The results can be summarised as follows:

• 1 The mineral nitrogen content of the subsoil varies widely depending on farming practice.
• 2 The effective depth limit for N uptake by winter wheat appears to be 150 cm.
• 3 Averaged over 22 sites, 33% of the total N uptake was from the subsoil (range 9–75%); 25% was from the 30–90 cm soil layer and 8% from the 90–150 cm soil layer.
• 4 Decreasing the N supply to the topsoil increased N uptake from the subsoil.
• 5 N uptake from the subsoil is not dependent on water uptake from the subsoil; nitrate is readily transported to absorbing roots by diffusion.
• 6 When deciding on the rate of fertilizer N to apply in early spring, soil mineral N to a depth of 90 cm should be taken into account. For subsequent dressings, the soil mineral N between 90–150 cm depth needs to be considered.

     

Evaluation of acute toxicity of phenol and its chloro- and nitro-derivatives to certain teleosts

Acute toxicity bioassays were conducted to evaluate the comparative toxicity of phenol (an aromatic hydrocarbon) pentachlorophenol (chloro-derivative of phenol) and dinitrophenol (nitro-derivative of phenol) for determining the LC50 and acute toxicity range for 24, 48, 72 and 96h, against the test fishes Notopterus notopterus, Colisa fasciatus and Saccobranchus fossilis. Relative susceptibility of fish, safe concentrations, heterogeneity factors and fiducial limits (95 %) were calculated using 96 h LC₅₀ values. Regression equations and slope functions (s) were calculated for each time interval. On the basis of relative susceptibility for phenol, Notopterus notopterus was found to be more susceptible as compared to Saccobranchus fossilis and the susceptibility of Colisa fasciatus lies in between the two. In case of pentachlorophenol and dinitrophenol, susceptibility lies in the increasing order from Colisa fasciatus, Saccobranchus fossilis to Notopterus notopterus.     

水分状况与供氮水平对土壤可溶性氮素形态变化的影响

采用通气培养试验,研究比较了两种水稻土在不同水分和供氮水平下的矿质氮(TMN)和可溶性有机氮(SON)的变化特征。结果表明,加氮处理及淹水培养均显著提高青紫泥的NH4+-N含量;除加氮处理淹水培养第7 d外,潮土NH4+-N含量并未因加氮处理或淹水培养而明显升高。无论加氮与否,控水处理显著提高两种土壤的NO3--N含量,其中潮土始见于培养第7 d,青紫泥则始于培养后21 d;加氮处理可显著提高淹水培养潮土NO3--N含量,却未能提高淹水培养青紫泥NO3--N含量。两种土壤的SON含量从开始培养即逐步升高,至培养21～35 d达高峰期,随后急剧下降并回落至基础土样的水平;SON含量高峰期,潮土SON/TSN最高达80%以上,青紫泥也达60%。综上所述,潮土不仅在控水条件下具有很强硝化作用,在淹水条件下的硝化作用也不容忽视,因此氮肥在潮土中以硝态氮的形式流失的风险比青紫泥更值得关注;在SON含量高峰期,两种土壤的可溶性有机氮的流失风险也应予以重视。     

Carbon paste biosensor based on crude soybean seed hull extracts for phenol detection

In this study, a novel biosensor based on enzyme extracts from soybean seed hulls has been prepared, which demonstrated promising results in the detection of hydrogen peroxide and phenol. The biosensor preparation is straightforward and inexpensive, and the response time is 50 s. The optimum conditions of pH and temperature are a pH of 7.4 and a temperature of 20 degrees C. Contrary to expectations, the biosensor showed narrow pH and temperature optimums. The effects of enzyme loading and type of mediator were also investigated. The biosensor showed a linear response up to 500 microM phenol.     

Zinc chloride-diphenylamine reagent for thin layer chromatographic detection of some organophosphorus and carbamate insecticides

Zinc chloride-diphenylamine reagent, whose use has been reported for the detection of organochlorine insecticides by thin layer chromatography, was further studied for its ability to detect the organophosphorus insecticides phorate, phosphamidon, DDVP, and phosalone and the carbamate insecticide carbaryl and aldicarb. These insecticides give intense blue-green spots with this reagent. The procedure can be applied to the detection of the insecticides in biological materials and thus has a potential use in forensic toxicology.     

Deposition of sulphur and nitrogen compounds in Croatia

Since precipitation is an efficient scavenger of pollutants, concentrations of major ions in precipitation reflect changes in chemistry of the atmosphere and in the subsequent exposure of various ecosystems to deposition. The National Atmospheric Precipitation Chemistry programme was initiated in 1978 and operated by Meteorological and Hydrological Service of Croatia to provide needed information on geographical patterns and temporal trends in precipitation chemistry in Croatia. To accomplish this, a network of about 20 stations, settled in different geographical regions, operates on a daily basis for 15 years now. Some monitoring stations are site- and study- specific; others are included in long-term, regional, or European monitoring networks (EMEP, GAW, MEDPOL, GEMS). The purpose of this work was to summarise existing data from the whole network for the period 1981–1992 and to compare data from measurements with EMEP model calculations of acid deposition. Results presented here show that annual average concentration and deposition values at remote sites agree reasonably well compared to modelled ones.     

Transformation of nitrogen compounds in the tundra soils of Northern Fennoscandia

The transformation of organic nitrogen compounds in the soils of tundra ecosystems of Northern Fennoscandia has been studied under laboratory and natural conditions. Tundra soils contain significant reserves of total nitrogen, but they are poor in its extractable mineral and organic forms. The potential rates of the net mineralization and net immobilization of nitrogen by microorganisms vary among the soils and depend on the C: N ratio in the extractable organic matter and microbial biomass of soil. Under natural conditions, the rate of nitrogen net mineralization is lower than the potential rate determined under laboratory conditions by 6–25 times. The incubation of tundra soils in the presence of plants does not result in the accumulation of mineral nitrogen compounds either in the soil or in microbial biomass. This confirms the high competitive capacity of plants under conditions of limited nitrogen availability in tundra ecosystems.     

Microbial transformation of nitrogen compounds in soils of the southern taiga

The intensity of the processes of nitrogen mineralization, fixation, and denitrification was assessed in the high-moor peat gley, white-podzolic, pale-podzolic, burozem, low-moor peat, and soddy-gley soils of the Central Forest Biosphere Reserve (CFBR). The actual and potential activities of the nitrogen fixation and denitrification were determined using the gas-chromatographic method, and the intensity of the ammonification was determined using ion-selective electrodes. The maximum intensity of the nitrogen fixation was observed in the low-moor peat and soddy-gley soils, which are characterized by a high content of organic matter. High denitrification activity was found in the low-moor peat soil (0.31 nmol N₂O/g per h); this was determined by the excessive moistening of this soil. The processes of organic nitrogen mineralization were the most intensive in the upper (L and F) subhorizons of the litter.     

Improved reagent for detection of allantoin in thin-layer chromatographic method for urine stains on foods and packaging

Ten detection reagents known to react with either primary amine groups or indole derivatives were tested to improve sensitivity for allantoin (ALN) and indican (IND) in the official AOAC thin-layer chromatographic method for urine metabolites (44.175-44.177). The lowest levels found using the official method were 500 ng ALN and 6 ng IND. The best reagent was p-dimethylaminocinnamaldehyde (pDMAC), which yielded intensely colored spots with both compounds. The lowest amounts consistently found were 125 ng ALN and 13 ng IND. pDMAC was also used as an overspray for ALN after the spray specified in the official method, p-dimethylaminobenzaldehyde (pDMAB), was applied. This resulted in a detection limit of 250 ng. The overspray procedure was incompatible with IND detection, but provided an easy way to gain slightly greater sensitivity for ALN when use of pDMAB gave negative or borderline results. The combined use of pDMAC for ALN, and the official sprays (pDMAB and sodium acetate) for IND, maximized sensitivity for both compounds.     

基于叶片光谱透过特性的植物氮素测定

该文通过不同施氮水平下营养液栽培的水稻和黄瓜叶片在300～1100 nm的分光光谱透过率,与其叶绿素含量和含氮量的相关性分析,确定了560、650和720 nm作为特征波长,940 nm作为参比波长可用于植物营养的快速无损诊断。以上述波长的光谱透过率构建的21组光谱特征参数中,(T940-T560)/(T940+T560)、log(T940/T560)和log(T940/T650)与水稻和黄瓜叶片的叶绿素含量和含氮量的相关性较好,且经回归估测检验的相对误差均小于8%。因此,上述光谱特征参数可作为植物氮素营养指标用于植物叶片的叶绿素含量和含氮量的快速无损估测,从而为植物营养无损诊断提供技术支持。     

Mineralization of nitrogen compounds in soils of south-taiga ecosystems

The productivity of the nitrogen mineralization in the A0 (0–2 cm), A1 (2–3 cm), and A2 (3–13 cm) horizons of a soddy-podzolic soil was measured in a wood-sorrel-whortleberry birch forest (7Birch3Asp, 80 years, the second stand quality class, tree canopy density 0.7, Yaroslavl oblast) using the sample incubation method; the measurements were performed from May till October in eight replicates for each horizon. In 2007, 5.85 ± 0.73 g N/m² were mineralized in the soil. In the litter, 2.01 ± 0.23 g N/m² were mineralized, whereas 0.35 ± 0.03 and 3.49 ± 0.72 g N/m² were mineralized in the A1 and A2 horizons, respectively. In 2008, 3.34 ± 0.25 g N/m² were mineralized in the A0 and A1 horizons, of which 2.44 ± 0.23 g N/m² were in the former. Ammonification prevailed in all the horizons. The contribution of nitrification was assessed as 1.6 and 0.3% of the process’s productivity in 2007 and 2008, respectively. The C_org and N_org pools decreased in the litter by 407 g C/m² and 13.7g N/m² (or 33%) from May to October. Of this carbon amount, 67% is spent for humification and the organic mass preservation and 33% was transformed to carbonic acid. The nitrogen expenses for the synthesis of humus acids are equal to 70 and 30%; it is spent equally for the mineralization of the element and its immobilization by microorganisms. In the A0 and A1 horizons, the seasonal trends of the ammonification correlated with the carbon dioxide emission from these horizons in the year of 2008 with r = 0.75 atp = 0.09 and r = 0.82 atp = 0.04 for both horizons, respectively.     

Determination of phenol in honey by liquid chromatography with amperometric detection

A sensitive, selective analytical method has been developed for determination of phenol in honey by liquid chromotography (LC) with amperometric detection (AMD). Phenol is extracted with benzene from the distillate of honey. The benzene extract is washed with 1% sodium bicarbonate solution and then reextracted with 0.1N sodium hydroxide followed by cleanup on a C18 cartridge. Phenol is determined by reverse-phase LC with amperometric detection. An Inertsil ODS column (150 X 4.6 mm, 5 microns) is used in the determination. The mobile phase is a mixture (20 + 80 v/v) of acetonitrile and 0.01M sodium dihydrogen phosphate containing 2mM ethylenediaminetetraacetic acid, disodium salt (EDTA) with the pH adjusted to 5.0. The flow rate is 1 mL/min under ambient conditions. The applied potential of the AMD using a glassy carbon electrode is 0.7 V vs an Ag/AgCl reference electrode. Average recoveries of phenol added to honey were 79.8% at 0.01 ppm spiking level, 90.4% at 0.1 ppm, and 91.0% at 1.0 ppm. Repeatabilities were 3.4, 1.3, and 1.8%, respectively. The detection limit of phenol in honey was 0.002 ppm. For analysis of 112 commercial honey samples, the range and average values of 32 detected samples were 0.05-5.88 ppm and 0.71 ppm, respectively.     

Microbial transformation of nitrogen compounds in middle taiga soils

The intensity of mineralization, nitrogen fixation, and denitrification in forest soils of the Karelian middle taiga ecosystems has been evaluated. Podzol-gleyish soil underlying a birch forest with gramineous plants and miscellaneous herbs was shown to have the highest nitrogen-fixing activity. The loss of gaseous nitrogen during denitrification was insignificant due to the low nitrifying activity of the soils named above. N₂O uptake by microorganisms was rather intensive in all the soils analyzed, and in illuvial-humo-ferric podzols underlying pine and spruce forests this process predominated. Podzolic sandy loam gley-like soil of a birch forest with gramineous plants and miscellaneous herbs had the highest potential for the mineralization of organic nitrogen; the rate of ammonification and nitrification in this soil was maximal.     

Inhibition of nitrification in soil by heterocyclic nitrogen compounds

Summary The relationship between the structures of diverse heterocyclic nitrogen (N) compounds and the effectiveness of these compounds for the inhibition of nitrification in soil was studied by determining the effects of different amounts of 12 unsubstituted and 33 substituted heterocyclic N compounds on the production of (NO ₂ ^– +NO ₃ ^– )-N in soils incubated at 25 °C for 21 days after treatment with ammonium sulfate. The results showed that unsubstituted heterocyclic N compounds containing two adjacent ring N atoms inhibit nitrification in soil and that two of these compounds, pyrazole and 1,2,4-triazole, are potent inhibitors. They also showed that several substituted pyrazoles and thiadiazoles are good inhibitors of nitrification in soil (e.g., 3-methylpyrazole and 3,4-dichloro-1,2,5-thiadiazole).     

Microbial activity differentially regulates the vertical mobility of nitrogen compounds in soil

Alongside nitrate, dissolved organic nitrogen (DON) represents a significant N loss pathway in many agroecosystems. To better understand the factors controlling DON leaching in soil we followed the vertical movement of ¹⁵N-labeled NO₃⁻, NH₄⁺, alanine and trialanine in packed soil columns in response to a simulated rainfall event. We show that in autoclaved (sterile) soil where sorption is assumed to be the dominant regulating factor, leaching followed the series NO₃⁻ > trialanine > alanine > NH₄⁺. In the non-sterile packed soil columns, the rapid rate of NO₃⁻ leaching was unaffected whilst the movement of the amino acid, peptide and NH₄⁺ was almost completely prevented due to microbial immobilization. Our results support the view that (1) DON loss from agricultural soils occurs mainly in the form of recalcitrant compounds (e.g. humic DON) rather than in the form of labile low MW DON (e.g. oligopeptides and amino acids), and (2) that although nitrate was bioavailable, it was not a preferred N form for the C-limited microbial biomass.     

Utilization of seed and medium nitrogen in young plant seedlings

It is well known that plants can begin to absorb medium nitrogen just after germination (1, 3). However, it is also true that most plants can develop roots and shoots using their seed materials until they can grow autotrophically through fixing carbon dioxide and absorbing nutrients. Moreover, young rice seedlings removed of their endosperm are depressed in the growth of roots and shoots even though they are supplied with nitrogen and sulphur sources through the culture medium (4). In this report, the importance of seed nitrogen in terms of amino acids in the growing roots and shoots of rice, corn and soybean is discussed. The experimental procedures were as follows.     

Stimulating effect of earthworm excreta on the mineralization of nitrogen compounds in soil

The effect of excreta of earthworm species Aporrectodea caliginosa and Eisenia fetida on the mineralization of nitrogen compounds in soils has been studied. A single application of excreta obtained from three earthworms in one day increased the formation of nitrate nitrogen compounds in the soil by 10–50%. The application of ammonium nitrogen (in the form of NH₄Cl) in amounts equivalent to the ammonium nitrogen content in the daily excreta of three earthworms had the same effect on the mineralization of nitrogen compounds. The effect of earthworm excreta, as well as the effect of ammonium nitrogen, on the nitrification process was an order of magnitude higher than their contribution to the formation of nitrates due to the oxidation of the introduced ammonium. Hence, ammonium—an important component of the earthworm excreta—can exert a stimulating effect on nitrification processes in the soil and produce long-term cumulative effects that are much more significant than the direct effect of this nitrogen compound.