Fate of humic acids isolated from natural humic substances

Composition of humic acids (HA) is a function of plant-derived inputs, degradation processes regulated by microorganisms, organo-mineral interactions and age. Characterization of different origin humic substances is important for evaluation of their contribution to stabile and labile carbon pool in the environment. The relative abundance of chemical components in HA isolated from soils, compost, commercial lignohumates, alginite, acadiane and lignite was studied with aim to quantify content of important biomarkers such as amino acid, lipids and polyphenols. HA were considered as a heterogeneous complex and high concentration of peptides, polyphenols and lipids was determined in acadian-HA to compare with soil-HA. Compost-HA contained much more amino acids to compare with soil-HA samples. Alginite-HA and lignite-HA were similar in biomarkers content to soil-HA. Fourier transform infrared spectroscopy confirmed that chemical composition and functional groups content differs with the origin, humification degree and the age of studied samples. Soil-HA are typically composed of a variety of ?OH, COOH?, C–O, C–H₂, (aliphatic and aromatic) groups, quinines, lignin fragments, polysaccharide, monosaccharide and proteins fragments, which are linked together by ?O?, ?NH?, ?H=, >C=O, metal ions and –S? groups. ¹³C NMR spectroscopy showed that aromatic carbon content was the highest in lignite-HA and soil-HA.     

Monitoring of subaqueous depots with active barrier systems for contaminated dredged material using dialysis samplers and DGT probes

Background, Aims and Scope  Disposal of dredged material in subaqueous depots is increasingly considered an economic and ecologically sound option in managing contaminated dredged material. The concept of subaqueous disposals capped with active barrier systems has been developed to minimize this risk of contaminant release. As such a depot represents a permanent installation within a sensitive ecosystem, it requires a thorough monitoring concept. It is the goal of this work to develop such a concept regarding general considerations and results of laboratory and field investigations. Methods  In addition to the state-of-the-art techniques developed for other under-water constructions, this monitoring concept is developed with particular respect to the chemical isolation of the dredged material from the overlying water body. It comprises the use of seepage meters, dialysis samplers, and DGT gel probes for determining the migration of selected target solutes. The capability of the dialysis samplers is demonstrated by comparing field results with model calculations. The appropriateness of DGT probes to assess the impact of humic substances on trace metal speciation and on copper toxicity is demonstrated with the aid of laboratory experiments. Results and Discussion  The experimental results show that, by using dialysis samplers, the temporal changes in concentration-depth-profiles of heavy metals in the pore solution can be monitored. Additionally, the application of DGT probes facilitates the in situ detection of labile species of a metal in the presence of dissolved humic substances, which serves to reflect its toxicity. Conclusions. Three subsequent monitoring phases are distinguished on the basis of both general considerations and the findings from field results: A hydraulic phase that is characterized by compaction and pore water expulsion, a geochemical phase in which the demobilization of pollutants can occur due to substantial changes in the physico-chemical conditions (pH, EH), and a steady-state-phase where pore water flow and geochemical conditions are approaching their minimum. Recommendations and Outlook  The monitoring concept suggested here provides a versatile tool to assess the chemical isolation of subaqueous sediment depots and other contaminated sediment sites. This is of great importance as subaqueous disposal is increasingly considered a future management strategy as space for upland disposal is limited and treatment, in general, proves to be too costly.     

Light Weight Aggregates made from Dredged Harbour Sediments

Goal  

Annually, 400.000 m₃ harbour sediments are dredged to maintain the water depth in the harbours of Bremen and Bremerhaven. The sediment contains organic and inorganic pollutants and hence is deposited on a landfill. Because of the limited capacity of that landfill alternative treatment techniques are investigated. This study aims to evaluate the production of Light Weight Aggregates (LWA) from harbour sediments with respect to the product quality and environmental aspects of the use of the LWA.     

黄土高原旱地轮作与施肥长期定位试验研究 Ⅱ.土壤酶活性与土壤肥力

本文分析了长期试验土壤酶活性与土壤有机C、全N、有效P含量、主要微生物类群之间的关系。相关分析表明,土壤脲酶、碱性磷酸酶、蛋白酶活性随土壤有机C含量的增加而增加,蔗糖酶、过氧化氢酶活性与有机C之间的关系因施肥种类及种植方式的不同而不同;微生物数量仅真菌与脲酶、蛋白酶活性之间的相关性达到显著水平。除过氧化氢酶外,其它4种酶的活性均与当年种植冬小麦处理的产量存在显著相关关系。利用主成分分析与通径分析揭示了土壤酶活性与养分之间的内在关系及酶活性对土壤养分的影响。根据主成分分析结果,旱地土壤肥力状况用脲酶、碱性磷酸酶、蛋白酶活性作为综合评价指标优于过氧化氢酶与蔗糖酶。     

Influence of spring preparation date and soil water content on seedbed physical conditions of a clayey soil in Sweden

Secondary tillage performed under inadequate soil water contents usually leads to a poor seedbed. Under normal Swedish weather conditions, clayey soils ploughed during autumn form a very dry top layer in spring, which acts as an evaporation barrier so that deeper layers remain wet. Thus, the conventional approach considering soil workability in relation to a single value of soil water content is difficult to apply. Hence, a field experiment was carried out to study the effect of seedbed preparation date, the associated soil water contents and traffic consequences on the physical properties of a spring seedbed. The field was autumn ploughed and the experiment started as soon as the field was trafficable after winter thawing. The seedbed preparation consisted of three harrowing operations on plots 8 m×8 m (three replications) with a spring tined harrow and a tractor mounted with dual tyres and was performed on 10 occasions from the beginning of April to the middle of May. With the exception of some short periods after rain, the soil had a clear water stratification during the experiment, with a very dry superficial layer (5–20 mm thick) contrasting to water contents over 300 g kg⁻¹ from only 40 mm depth. After the harrowing operation, the seedbed aggregate fraction less than 2 mm increased from about 40% at the beginning of April to about 60% for the last four treatments in May. Contributing factors to the rise were attributed to the lower water contents of the top layer (<40 mm) and the drying–wetting and freezing–thawing cycles that occurred in the surface layer during April. There were no significant differences in bulk density after harrowing between the treatments but an increase in penetration resistance up to a depth of 180 mm in the harrowed plots was statistically significant (P<0.001). In the non-harrowed soil, penetration resistance also increased, including in those soil layers where water contents kept nearly constant.

In conclusion, the seedbed preparation dates had only a minor effect on soil compaction, as measured by bulk density and penetration resistance, due to the slow drying beneath the dry top layer. The fraction of fine aggregates in the seedbed increased with time. Thus, the optimal time for seedbed preparation depended mainly on soil friability and not on the risk of compaction.     

Betaxanthin-Rich Extract from Cactus Pear Fruits as Yellow Water-Soluble Colorant with Potential Application in Foods

Cactus pear (Opuntia ficus-indica) fruit juice is a source of betaxanthin pigments which can be used as a natural yellow food colorant. The HPLC chromatographic pigment pattern corresponding to the betaxanthin-rich extract revealed the presence of four betaxanthins, of which indicaxanthin (proline-betaxanthin) accounts for around 85%. A betaxanthin-rich water-soluble food colorant from cactus pears fruits was produced by spray-drying microencapsulation using maltodextrin as a wall material. The resulting powder was characterized by scanning electron microscopy, and its apparent color was analyzed by spectrometry. The stability of the microcapsules was examined at +20, +4 and??20 °C in the dark during six months of storage. The degradation of betaxanthins was delayed by microencapsulation and their colorant stability increased at lower temperatures. The potential application of the colorant microcapsules was successfully assessed in two food model systems: a yogurt and a soft-drink. Both foods presented an attractive pale yellow color. Pigment retention and color parameters were investigated during storage under controlled conditions. Slight changes in the pigment retention, in both model systems, pointed to excellent preservation in the dark, even after 28 days at 4 °C. However, the presence of light contributed to betaxanthin deterioration. Spray-drying microencapsulation succeeds in reducing volumen of the pigment extract and can be easy in storage and delivery of the powders. It is proved to be a suitable process that can be recommended for stabilizing betaxanthins from cactus pears to be used as water-soluble natural colorants in foods.     

Effects of water table management on soil salinity and alfalfa yield in a semi-arid climate

A lysimeter experiment was conducted to investigate the effect of water table management (WTM) on distribution of soil salinity and annual alfalfa (Medicago scutellata) yield. Subirrigations with three levels of water table namely, 0.5 (WT0.5), 0.7 (WT0.7), and 1.0 m (WT1.0) and a free drainage (FD) conventional irrigation treatment were selected for this study. All treatments were arranged in a complete randomized block design with three replicates. The results of this study indicated that the average soil electrical conductivity of the saturated extract (ECe) in the root zone gradually increased and exceeded the designated crop threshold value (4 dS/m) after the first forage harvest in subirrigated lysimeters. A higher salt accumulation was observed at the WT0.5 treatment. The average dry matter yield of annual alfalfa in WT0.5 and WT0.7 treatments was found to be 52 and 73% higher compared with the control treatment, respectively.     

Evaluation of the durability of the <Emphasis Type="Italic">Barley yellow dwarf virus</Emphasis>-resistant <Emphasis Type="Italic">Zhong ZH</Emphasis> and <Emphasis Type="Italic">TC14</Emphasis> wheat lines

Serial passage experiments (SPE) of a Barley yellow dwarf virus-PAV (BYDV-PAV) isolate were performed on Zhong ZH and TC14 wheat lines to evaluate the durability of their resistance to BYDV. At different passage numbers (from the 2nd to the 114th), biological properties of the produced isolates were recorded either by monitoring infection percentages and virus titers of the first 3 weeks of viral infection or by measuring their impact on yield components. Statistical analyses using the area under pathogen progress curves and the area under concentration progress curves demonstrated that these two resistant lines induce, after only a few passages, a selection of variant(s) with significantly modified infection abilities. Isolates resulting from SPE performed on these lines induced important decreases of yield components. These results indicate that the use of Zhong ZH and TC14 lines in BYDV-resistant breeding programmes should be approached with caution.     

Integrated production of fish (pacu <Emphasis Type="Italic">Piaractus mesopotamicus</Emphasis> and red tilapia <Emphasis Type="Italic">Oreochromis</Emphasis> sp.) with two varieties of garnish (scallion and parsley) in aquaponics system

Aquaponics is emerging as an alternative for high-health food production. Being able to identify the technical viability of non-conventional plants and fish species would help to increase the interest and possibilities in aquaponic systems. The goal of the present study was to evaluate the aquaponics production of two garnish species: scallion (S) and parsley (P), using effluents of pacu and red tilapia culture. Two aquaponics devices were used, differing according to the fish species, generating two different effluents. Thus, for plant performance, four treatments were evaluated in a factorial design (plant species and fish effluent as main factors), as followed: Pacu-S, Tilapia-S, Pacu-P, and Tilapia-P, with three replicates each, for 35 days. Fish performance was evaluated using Student’s t test. Each experimental device included a fish tank, filters, and six experimental units for the plants (floating rafts). Results indicated that feed conversion ratio (FCR) was higher in tilapia as compared to pacu (p < 0.05); however, fish productivity and survival were similar between species. Plant performance parameters were similar with no significant differences regardless of the fish effluent (p > 0.05), except for higher number of leaves per plant in scallion cultured using pacu effluent. Plant performance comparing both plant species indicated that scallion performed better as compared to parsley in all parameters. In addition, scallion also performed better related to the plant quality index. The results indicate that pacu presented a viable alternative for the aquaponics production, and regarding to the garnish, scallion performed better results as compared to parsley.     

Decline of <Emphasis Type="Italic">Pinus thunbergii</Emphasis> Parlat. stands due to excess soil moisture caused by a buried andosol layer at a coastal sand site in Hokkaido,northern Japan

To demonstrate the effect of excess soil moisture on the decline of a coastal Pinus thunbergii stand in Oshamanbe, southwestern Hokkaido, Japan, soil moisture content was monitored for 4 years. The saturated hydraulic conductivities (K _S) of different soil types (coastal sand, supplied topsoil, and buried concreted andosol) and the distribution of the buried concreted andosol layer were investigated. We also examined needle length to verify the real-time response of P. thunbergii to excess soil moisture. Soil moisture content at the heavily damaged site was more heterogeneous than that at the slightly damaged site, and a sensor near the ground always reported a higher soil moisture content at the heavily damaged site than at the slightly damaged site. The buried concreted andosol layer was always found at the heavily damaged site. The K _S of the andosol layer was 10⁻⁵, suggesting that this layer is less permeable to water, leading to excess soil moisture at this site. P. thunbergii needles from the heavily damaged site were shorter than those from the slightly damaged site, possibly because of water stress. Together with other symptoms observed at the study sites, i.e., crown dieback and intense lateral growth, this information leads us to conclude that the decline of P. thunbergii stands at the heavily damaged site in Oshamanbe was caused by excess soil moisture due to the less permeable buried concreted andosol layer.