Types Of Humic Acids Research Articles

Effect of humic acids extracted from different organic sources and inoculation with Bacillus subtilis or Aspergillus Niger on urease activity in calcareous soil

Humic substances have received a large share of research and development as amendments to poor fertility soils that are poor in fertility and have deteriorating physical properties, since the process of extracting is a common process and easy to implement, as well as diluting these acids with water enables them to be used at economically acceptable levels over large areas. It is necessary to noticed that the properties of these acids depending on the organic source and the concentration added to the soil. A laboratory experiment was conducted at the Department of Soil Sciences and Water Resources, College of Agriculture, University of Basrah ,IRAQ to demonstrate the effect of humic substances extracted from different sources and inoculation with Bacillus subtilis or Aspergillus niger on the activity of the urease in calcareous soil. Wheat straw, alfalfa leaves, goat waste and poultry waste were composted aerobically for 3 months by filling a hole of 2×2×1.5 m by layers of such waste ,turned weekly for aeration. Each pile was extracted for humic acids (humic acid + fulvic acid) . Humic acid mixed with to soil at levels of 0, 25, and 50 L h-1. The soil was also inoculated with Bacillus subtilis or Aspergillus niger isolated from local soil at rates of 20.06×106 and 40× 103 cfu ml-1, respectively The samples were incubated at field capacity level 28±2°C for 30 days. Urease activity was estimated after 7 or 30 days by determining NH4+ released using steam distillation method . A decrease in urease activity was observed when treated with different types of humic acid compared to the control treatment. The lowest activity was obtained at humic acids extracted from poultry waste, reaching 312.0 and 188.72 µg N-NH4+g-1soil.2h-1 at incubation periods of 7 and 30 days, respectively .The results also indicated that increasing the level of humic acids significantly inhibited the activity of the enzyme. However, in soil treated with Bacillus subtilis or Aspergillus niger, an increase in urease activity was observed compared to the non-inoculation treatment. Treatment with the fungal inoculant had higher activity than the bacterial inoculum, reaching 324.5 and 297.2 µg N-NH4+ g-1 soil 2 hours-1 for both inoculants at a period of 7 days, and 178.09 and 150.31 µg N-NH4+g-1soil.2h-1at a period of 30 days, respectively.It is proposed that the inhibition of urease by humic acid addition may benefit for increasing urea fertilizer efficiency.

Effects of humic acid on chlorophyll content and root length of ryegrass (lolium multiflorum lam.)

Use of humic acid has great significance to improve soil quality and crop yield in loess hilly and gully areas. In the present study, potassium humate (PH) and potassium fulvic acid (PFA) were used as soil amendments in gully the control project area of Yan'an City, Shaanxi Province. A pot culture experiment was conducted to evaluate the influence of two types of humic acid (PH and PFA) on the growth characteristics of ryegrass in the loess hilly and gully area. Results showed that application of potassium humate and potassium fulvic acid considerably increased the chlorophyll synthesis as well as root length of ryegrass. When the proportion of PH and PFA was the same, the effect of PFA was to be found better than that of PFH. When the proportion of potassium humate was 15g/kg soil, the leaf chlorophyll content and root length attained the maximum, and the soil maturity effect was the best. Bangladesh J. Bot. 52(2): 467-472, 2023 (June) Special

Effects of humic acid on chlorophyll content and root length of ryegrass (lolium multiflorum lam.)

Use of humic acid has great significance to improve soil quality and crop yield in loess hilly and gully areas. In the present study, potassium humate (PH) and potassium fulvic acid (PFA) were used as soil amendments in gully the control project area of Yan'an City, Shaanxi Province. A pot culture experiment was conducted to evaluate the influence of two types of humic acid (PH and PFA) on the growth characteristics of ryegrass in the loess hilly and gully area. Results showed that application of potassium humate and potassium fulvic acid considerably increased the chlorophyll synthesis as well as root length of ryegrass. When the proportion of PH and PFA was the same, the effect of PFA was to be found better than that of PFH. When the proportion of potassium humate was 15g/kg soil, the leaf chlorophyll content and root length attained the maximum, and the soil maturity effect was the best. Bangladesh J. Bot. 52(2): 467-472, 2023 (June) Special

Study of Hybrid Humic Acids Modification of Environmentally Safe Biodegradable Films Based on Hydroxypropyl Methyl Cellulose

The possibility of increasing the strength and operational properties of ecologically safe biodegradable polymeric materials based on hydroxypropyl methyl cellulose by using its modification with the different types of humic acids (HAs) from lignite is considered. Hybrid ecologically safe high-strength films with antibacterial properties were obtained for the first time. Physicochemical studies and IR spectroscopy confirmed the development of hybrid structures of hydroxypropyl methyl cellulose, modified with the different types of HAs. Changes in water absorption, tensile strength, relative elongation at break, and time of mold appearance for the environmentally safe biodegradable polymeric materials based on hydroxypropyl methyl cellulose were revealed depending on the content of the different types of humic acids. It was also shown that the hybrid modification of hydroxypropyl methyl cellulose with the different types of HAs allows preserving the biodegradability of the films along with imparting the antibacterial properties. The developed ecologically safe biodegradable films with antibacterial properties based on hydroxypropyl methyl cellulose and HAs, in terms of their operational characteristics, are superior to the known similar biodegradable films based on natural biopolymers.

TECHNOLOGY OF HYBRID MODIFICATION WITH HUMIC ACIDS OF BROWN COAL HYDROXYPROPYLMETHYL CELLULOSE FILMS

The peculiarities of the technology of hybrid modification of lignite humic acids of biodegradable films based on hydroxypropylmethylcellulose are considered. As a result of the conducted research, hybrid biodegradable films with antibacterial properties were obtained for the first time. Hydroxypropylmethylcellulose of the Walocel brand was used for the production of biodegradable films, and citric acid (99.88%) according to GOST 3652 is used as a catalyst for crosslinking biodegradable polymer films. As part of the research, the hybrid structures of hydroxypropylmethylcellulose modified with different types of humic acids were actually determined by IR spectroscopy. As a result of the study, the regularities of changes in the time of appearance of mold of films within the framework of the technology of hybrid modification with lignite humic acids were established. It was also established that the technology of hybrid modification of hydroxypropylmethylcellulose films with humic acids of lignite and giving them antibacterial properties allows to preserve the properties of biodegradation. It was established that the technology of hybrid modification of hydroxypropylmethylcellulose with lignite humic acids of biodegradable hydroxypropylmethylcellulose films with different types of humic acids, while giving them antibacterial properties, allows the biodegradation of films based on them to be at least 91% within 6 months with an optimal humic acid content of 10% by mass. Biodegradable films with bactericidal properties based on hydroxypropylmethylcellulose, obtained according to the technology of hybrid modification with humic acids of lignite, in terms of their operational characteristics, are superior to known similar biodegradable films based on natural biopolymers and can be recommended for the manufacture of packaging of dry food products (bread, cereals, nuts, etc.) with an extended storage period.

Study of lignite humic acids hybrid modification technology of biodegradable films based on polyvinyl alcohol

Object of article study is lignite humic acids hybrid modification technology of biodegradable films based on polyvinyl alcohol. The possibility of increasing the strength and operational properties of biodegradable polymeric materials based on polyvinyl alcohol by using its modification with the different types of humic acids from lignite is considered. Lignite humic acids hybrid modification films with antibacterial properties were obtained. The two-stage technology of lignite humic acids hybrid modification of biodegradable films based on polyvinyl alcohol was formalized. At the first stage of lignite humic acids hybrid modification technologies for hybrid-modified biodegradable materials production, lignite humic acids are received. At the second stage, hybrid modification of lignite humic acids (that are part of biodegradable polyvinyl alcohol films), which are received by watering from a solution, takes place. It has been conducted a study on determining the effect of lignite humic acids hybrid modification on the most important operational properties of biodegradable film based on polyvinyl alcohol, i. e., tensile strength, relative elongation at break and time of mold appearance. Changes in tensile strength, relative elongation at break and time of mold appearance for the lignite humic acids hybrid modified biodegradable polymeric materials based on polyvinyl alcohol were revealed depending on the content of the different types of lignite humic acids. It was also shown that the lignite humic acids hybrid modification of polyvinyl alcohol with the different types of humic acids allows preserving the biodegradability of the films along with imparting the antibacterial properties. The developed lignite humic acids hybrid modified biodegradable polyvinyl alcohol films with antibacterial properties, in terms of their operational characteristics, are superior to the known similar biodegradable films based on natural biopolymers.

Effect of Humic Acid Binder on the Preparation of Oxidized Pellets from Vanadium-Bearing Titanomagnetite Concentrate

In order to pursue the goal of low-carbon ironmaking, a new type of humic acid (HA)-based binder was applied to the preparation of oxidized pellets from vanadium-bearing titanomagnetite (VTM) in this work. Effects of the HA binder (or with limestone) on the balling, preheating, and roasting behaviors of VTM were comparatively studied with bentonite. The embedded features of each mineral phase in sintered pellets, especially the crystallization and growth state of hematite grains, were deeply investigated by XRD, optical microscopy, and SEM–EDS measures. The binder dosage can be cut down by 50% when HA was used instead of bentonite. Fine hematite grains in HA pellets evolved into plump interlocking grains with ~5% of limestone addition. Pseudobrookite and magnesioferrite spinel phase formed at the optimal sintering temperature of 1250 °C, which could hinder the crystallization of hematite and affect the strength of final pellets.

REPEATED WASTE OF HUMATIVES INTO PLAIN METALS IN THE PURIFICATION OF WEAKLY ACID WATER, TO CLEAN Cu2+, Pb2+

Destroyed military and industrial facilities have grave consequences not only for the country's economy, but also for the environment and natural resources. At present, humic acids are quite well known and have been sufficiently studied by the natural sorbent. Due to a wide range of functional groups, they perform accumulative, transport, regulatory, protective and physiological functions. The interaction of metal ions with humates does not have a single clear described mechanism. This is facilitated by the complexity and diversity of the structure of humic acids, as well as various reaction conditions in laboratory and natural conditions. Therefore, ways to increase the efficiency of sorption, improve and search for new properties of these substances still remain relevant.
 In this work, the possibilities of reverse bonding of copper and lead ions in slightly acidic aqueous solutions at pH values of 4,4–6,3 are shown. Humic acids were isolated from peat and brown coal, and potassium humates produced in China were also used. In this study, model solutions of copper (II) sulfate and lead (II) acetate were used with a calculated concentration in terms of copper and lead of about 400 and 1000 mg/dm3, respectively. The regeneration of metal humate complexes was carried out by lowering the pH of the medium to 2,1–2,2. The degree of lead sorption was 97–99 % for Pb2+ solutions with a concentration of 216 mg/dm3. Studies have shown the effectiveness of re-use of regenerated humates with a degree of metal release of 85–91 % in relation to the sorbed amount.
 The metal content in the experiment was determined by inductively coupled plasma atomic spectroscopy.
 It was also found that the ratio of the average values of the specific sorption of lead and copper was from 2,8 to 3,1 for various types of humic acids (humates). The proximity of these values with respect to the atomic masses of lead and copper (3,3), in the author's opinion, is associated with the interaction of copper and lead ions with humates in a stoichiometric ratio due to a chemical reaction (reactions). The sorption given in the experiment is described by a linear dependence in the coordinate system: the mass of the sorbed metal (ions) – the mass of humates.

Compounding with humic acid improved nutrient uniformity in drip fertigation system using brackish water: The perspective of emitter clogging

Brackish water drip irrigation (BWDI) is an effective application to overcome the water scarcity issues and achieve sustainable agriculture development. However, emitter clogging and soil salinization is inevitable issue in BWDI, eventually threatening the environmental pollution and sustainable application of drip irrigation systems. Therefore, this study experimentally assessed the anti-clogging efficacy of compounding appropriate types of humic acid (HA) with conventional fertilizer in BWDI systems (BWDIs). Humic acid nitrogen (HAN), humic acid phosphate (HAP), humic acid potassium (HAK), were compounded with conventional fertilizers. Our results revealed, compared with conventional fertilizer (CK) the HA treatments indirectly affected the precipitates and particulate fouling by absorbing the active functional groups, and directly decreased the pH, calcium and magnesium contents in brackish irrigation water. Accordingly, HA compound fertilizer significantly reduced the fouling content of drip irrigation system, and the anti-clogging effect became better with the increase of HA application. Thus, based on better anti-clogging performance and minimum fertilizer costs, our results suggested, the HAN+HAK integrated fertigation could be an effective selection for BWDIs, which significantly enhanced the average discharge ratio and Christiansen coefficient of nutrient uniformity in BWDIs by 16.0% and 19.0% respectively. These results might provide a new guideline for the successful application of HA compound fertilizer in BWDIs, to increase the drip irrigation anti-clogging ability and overcome the agricultural non-point source pollution issues.

Effects of different types of humic acid isolated from coal on soil NH3 volatilization and CO2 emissions

Humic acid can improve soil nutrients and promote plant growth. Weathered coal and lignite can be used as agricultural resources due to high humic acid content, but their impact on soil NH3 volatilization and CO2 emissions are yet to be determined. In this study, a field experiment was carried out to compare the effects of four types of humic acid isolated from coal (pulverized weathered coal (HC), pulverized lignite (HL), alkalized weathered coal (AC) and alkalized lignite (AL)) on NH3 volatilization, CO2 emissions, pH, the C/N ratio and enzyme activities in soil cultivated with maize. The effect of biotechnology humic acids (BHA) was also examined for comparison. HL, AC, AL and BHA all increased cumulative NH3 losses by 147.7, 278.5, 113.9, and 355.3%, respectively, compared with the control (chemical fertilizer only), and notably, BHA caused an increase of 90.71% compared with the humic acids isolated from coal. A significant increase in cumulative CO2 losses was observed only under AL treatment, by 14.44–24.90% compared with all other treatments. Soil urease activity was positively correlated with cumulative NH3 losses (P < 0.001), while the soil C/N ratio (P < 0.001) and soil sucrase activity (P < 0.05) were positively correlated with cumulative CO2 losses. Since humic acid from pulverized weathered coal caused no increase in NH3 volatilization or CO2 emissions, it is therefore thought to be the most suitable humic acid for field application.

Clay-Humic Substance Composites for Removal of Pharmaceuticals from Water

Humic substances are the main component of soil organic matter and they actively interact with substances in soils, including pollutants. Humic acid-clay mineral composite materials can be considered as prospective and low-cost sorbents for contaminant removal. The aim of this study is to develop clay mineral and humic acid composite materials and to characterise their possible applications. For this research, montmorillonite, kaolinite and bentonite were saturated with three types of humic substances: technical humic acid from lignite, humic substances extracted from raised bog peat (Latvia) and technical K humate from lignite. Obtained sorbents were characterized using FTIR. The sorption was characterised according to the chosen clay mineral and humic acid type and concentration. Comparing the influence of clay minerals and humic substances on humic matter sorption, it has been found that the sorbed amount of humic substances depend on chosen humic substances and/or clay mineral. Obtained sorbents were used for sorption of chlorpromazine. Results indicate that the most perspective sorbents for chlorpromazine removal are bentonite and bentonite modified with humic acid. However, montmorillonite-humic composites also can be used for removal of chlorpromazine from water.

Efficiency of Prepared Chelate Fertilizer From Humic Acid in Reducing Ammonia Volatilization From Urea Fertilizer

Composted cow manure sample was collected from filed of college of Agriculture, University of Basrah. Its properties were identified. Humic acid was extracted from cow manure and diagnosed according to elemental analysis (CHN), spectral study (E4/E6), infra-red spectrum (IR), in addition to chemical composition of functional groups. Two types of humic acid were prepared, one of them humic acid with fermented plant residue (HA1-N) and other humic acid with zeolite (HA2-N). A laboratory experiment was carried out to study the amount of ammonia volatile from two prepared chelate fertilizers (HA1-N and HA2-N) and urea fertilizer by incubation two types of soils (sandy soil and clay loam soil) at 35°C with four rates of nitrogen (0, 125, 250 and 500 mg N kg-1 soil) and with five incubation time (3, 6, 12, 24 and 48 days). The study found that increasing rate of nitrogen and incubation time increased ammonia volatilization, and the highest value was at the rate 500 mg N kg-1 soil and at 48 days of incubation to reach a 21.427 and 9.736 mg N-NH3 Kg-1 soil for sandy soil and clay loam soil, respectively. Application of two prepared chelate fertilizers (HA1-N and HA2-N) at rate 500 mg N Kg -1 reduced ammonia volatilization to 99.30 % and 98.62 % for sandy soil and 98.96 % and 97.77 % for clay loam soil comparing with urea fertilizer . Fertilizers were took the following order in reducing ammonia volatilization : HA1-N &gt; HA2-N &gt; Urea.

Influence of humic acid on the structure memory effect of hydrocalumite and its performance in the adsorption cycles of bisphenol A

Different types of humic acid (HA) were extracted from black soil and sediments and their influence on the regeneration and reusability of hydrocalumite (calcium -LDHs, Ca-LDH) were studied. The results showed that the regeneration of Ca-LDH after calcination (Ca-CLDH) required the shortest time to reconstruct in HA solution, and dissolution-reprecipitation was the main process responsible for the structure memory effect of Ca-LDH. In addition, metal ions were released from the sample complexed with HA, which indicates that HA plays an important role in the regeneration process. The crystal size of LDHs regenerated in HA solutions were smaller than that in deionized water. Surface area, pore size and volume of regenerated Ca-LDH decreased in the HA solution. New Ca-LDH was decomposed to release Ca2+ ions and formed CaCO3 with CO32− in deionized water. Differently, the formation of CaCO3 in HA solution was inhibited. During the recycle use for removal of bisphenol A (BPA) through calcination method, Ca-LDH was converted to CaCO3 in the absence of HA and the adsorption ability was decreased evidently. However, in the presence of HA, Ca-CLDH could transform into layered structure and maintain its adsorption performance. This is because the presence of HA has an influence on the structure regeneration of Ca-LDH, especially inhibiting the transformation of LDH into CaCO3.

Amelioration effect of humic acid on saline-alkali soil

A field experiment was conducted to investigate the effects of three types of humic acid, i.e. oxidized humic acid (OHA), aminated humic acid (AHA) and microbial-humic acid (MHA), on physico-chemical properties of saline-alkali soil and maize growth. Results showed that the application of all humic acid materials had no significant effect on soil pH in the current season. However, the soil electrical conductivity (EC), the contents of water-soluble Na+ and K+, and sodium adsorption ratio (SAR) decreased under all three treatments of humic acid application measured in up to 40 cm soil depth. OHA had the strongest effect in reducing soil EC, while no significant differences were detected among the three tested materials in reducing contents of water-solu-ble Na+ and K+ and SAR. In addition, humic acid reduced soil NO3--N content and increased soil NH4+-N content, soluble organic nitrogen (SON) content and total soluble nitrogen (TSN) content, with higher effects of AHA and MHA than OHA. Moreover, the application of humic acid materials increased the content of soil available phosphorus, which was most significant in MHA. Humic acid addition could significantly enhance the yield and function leaf SPAD value of maize, which did not vary among the tested humic acid materials. The rank of effect size on apparent utilization efficiency of N and P fertilizer was in the order of AHA>MHA>OHA. While OHA treatment had the highest agronomic efficiency of N and P, AHA treatment achieved the highest partial factor productivity of applied N and P.

Effects of natural organic matter with different properties on levofloxacin adsorption to goethite: Experiments and modeling

Adsorption of levofloxacin (LEV) to goethite in the pH range of 3–10, and in the absence or presence of natural organic matter (NOM) represented by nine types of humic acid (HA) and fulvic acid (FA), was studied using batch experiments. The adsorption of LEV to goethite was weak and showed a maximum around pH 5.8. Adding NOM to goethite strongly increased LEV adsorption to goethite, but hardly affected its pH dependency. The adsorption envelopes were well fitted to a linear additive model, in which LEV adsorption to goethite was simulated with the Charge Distribution Multi-Site Complexation (CD-MUSIC) model, and LEV adsorption to NOM was simulated with the Langmuir model. The fitted affinity constants (log K) for LEV adsorption to NOM were significantly and positively correlated with the SUVA (specific ultraviolet absorbance at 280 nm) values of NOM, and negatively correlated with E2/E3 (absorbance ratio at 250 nm and 365 nm) values, carboxyl contents, and the polarity of NOM. The results indicated that aromatic moieties of NOM play a key role in the interactions between LEV and NOM, and hydrophobic interactions and π-π interactions were the major mechanisms for LEV adsorption to NOM, whereas H-bond or surface complexation might not play an important role. Results show that both the concentrations and properties of NOM have a significant effect on the distribution or treatment of antibiotics in soils and waters, which will eventually affect the influence of antibiotics on microorganisms in the environmental systems.

Heavy Metals Adsorption from Aqueous Solutions onto Unmodified and Modified Jordanian Kaolinite Clay: Batch and Column Techniques

Awareness of, and concern about, water pollution all over the world has been increasing. In Jordan, water also has been polluted by different kinds of pollutants such as heavy metals, It is widely agreed that a properly developed green, low – cost and more efficient adsorbent is desired approach towards removing pollutants. Jordan has huge reserves of kaolinite. Unfortunately, it has a relative low cation–exchange capacity and a small surface area. However, it can be modified to enhance its adsorption capacity towards heavy metal ions. Humic acid was used to this purpose. Two types of humic acid were used; one was commercial from Fluka Company and the other was natural extracted from King Talal Dam sediments. Comparison of Pb (II), Cd (II) and Zn (II) adsorption from aqueous solutions onto unmodified and modified Jordanian kaolinite clay were studied using batch technique at different temperatures (25, 35 and 45°C) and different pH (4, 5 and 6). The effects of contact time, adsorbent dose, and the initial metal ion concentration were also studied. The uptake at low concentration reaches above 90% for Pb (II). The adsorbed amount trend was as follows: Pb (II) > Cd (II) > Zn (II) for both modified kaolinite clay. The column technique was used effectively for the determination of metal ion loading capacity. The uptake percentage fall in the same order (Pb (II) > Cd (II) > Zn (II)) for both modified kaolinite clay.

Effects of humic acids on the sorption and bioavailability of pyrene and 1,2-dihydroxynaphthalene

Sorption of organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) is an important process that controls their mobility and toxicity in soil. The relationship between the chemical properties of various types of humic acids (HAs) and their pyrene (4-ring PAH) sorption ability was investigated in batch experiments. Commercial HAs as well as those obtained from Umbric Andosol, Dystric Cambisol and cow manure compost were used. Additionally, fractionated Aldrich humic acid (AHA), which was obtained by fractional precipitation with ethanol, was evaluated to better understand how its chemical characteristics affect pyrene sorption. The value of the carbon-normalized partition coefficient (Kdoc ×105 L kg-C−1) for pyrene in all commercial HAs was within the expected range in the two soil HAs (0.43–2.69). Correlation analysis indicated that Kdoc values for fractionated AHA series tended to increase with increasing aromaticity (r = 0.82). Subsequently, the effects of various HAs on the toxicity of pyrene and 1,2-dihydroxynaphthalene (DHN), which is one of the major microbial metabolite of PAH such as pyrene, to a test microorganism were examined by spread plate counting by using a solid agar medium. While pyrene (a poorly water-soluble compound) did not inhibit bacterial growth, the inhibitory effect of the water-soluble DHN was apparent at 10 mg L−1. However, the addition of HA at 25 mg-C L−1 mitigated DHN toxicity. Furthermore, the detoxification effect tended to increase with increasing aromatic carbon content of HA (r = 0.94). The observed reduction in toxicity of DHN may be due to its sorption to the aromatic moiety of HA, by which the bioavailability is reduced.

Ultraviolet Radiation-Absorbing “Humic Pigments” of Cyanobacteria in Microbial Mats: Their Presumptive Photoprotective Function and Relevance to Early Precambrian Microbial Ecology and Evolution

Cyanobacteria that form the primary components of microbial mats in freshwater bogs and intertidal marine environments in the Bahamas produce water-soluble brown pigments whose spectral properties imply that they are a type of humic acid. These “humic pigments” are produced by vital processes of living cyanobacteria, not by decomposition of dead ones, as shown by decreases in the concentrations of humic pigments, ultraviolet (UV) radiation-absorbing photoprotective mycosporine-like amino acids (MAAs), and chlorophyll from upper to lower layers of the mats, and by the occurrence of humic pigments in cyanobacterial cultures. Unlike MAAs, which absorb UV radiation only within limited ranges of wavelengths, humic pigments absorb radiation spanning the entire UV spectrum, and absorbance increases with decreasing wavelength. These observations suggest that the biosynthesis of humic pigments originated as a photoprotective adaptation in the early Precambrian, enabling cyanobacteria to colonize shallow-water and terrestrial environments even though the atmosphere was virtually devoid of O2 and O3 and therefore transparent to all solar radiation in the UV region of the spectrum. Moreover, the evolution of this photoprotective mechanism may have been linked to the evolution of photosynthesis.

Interactive Effects of Super Absorbent Polymer and Nitrate Nitrogen

The superfluous application and low use efficiency of chemical nitrate nitrogen fertilizer account for the nitrogen pollution of soil and water, threatening human’s health. In order to raise the fertilizer use efficiency, prevent from non- point pollution and nitrogen pollution of groundwater, and select superior material, five different kinds of super absorbent polymer (SAP) were selected as the objects. Through the analysis of the characteristics change of water and fertilizer absorbing of the five SAPs within different concentration of NO3--N, and the discussion of interactive effects between the SAPs and NO3--N, it is showed that: the water absorbent ability of all kinds of SAP exhibits a negative relationship with the concentration of KNO3 by decreasing of more than 50%. For all the five types of SAPs, the type of polyacrylate shows the strongest ability of water absorbing in all kinds of KNO3 concentration and the type of humic acid- polyacrylate is least affected by saline solution. The type of PAM- inorganic mineral SAP does well in nitrogen absorbing, whose absorbing amount linearly increases with the KNO3 concentration increasing, while the other types of SAP shows no obvious ability for nitrogen absorbing.

Np(V) reduction by humic acid: Contribution of reduced sulfur functionalities to the redox behavior of humic acid

The role of sulfur-containing functional groups in humic acids for the Np(V) reduction in aqueous solution has been studied with the objective to specify individual processes contributing to the overall redox activity of humic substances. For this, humic acid model substances type M1-S containing different amounts of sulfur (1.9, 3.9, 6.9wt.%) were applied. The sulfur functionalities in these humic acids are dominated by reduced-sulfur species, such as thiols, dialkylsulfides and/or disulfides. The Np(V) reduction behavior of these humic acids has been studied in comparison to that of the sulfur-free humic acid type M1 at pH 5.0, 7.0 and 9.0 under anaerobic conditions by means of batch experiments. For Np redox speciation in solution, solvent extraction and ultrafiltration were applied. In addition, redox potentials of the sample solutions were monitored. At pH 5.0, both rate and extent of Np(V) to Np(IV) reduction were found to increase with increasing sulfur content of the humic acids. At pH 7.0 and 9.0, sulfur functional groups had only a slight influence on the reduction behavior of humic acid toward Np(V). Thus, in addition to quinoid moieties and non-quinoid phenolic OH groups, generally acknowledged as main redox-active sites in humic substances, sulfur functional groups have been identified as further redox-active moieties of humic substances being active especially in the slightly acidic pH range as shown for Np(V). Due to the low sulfur content of up to 2wt.% in natural humic substances, their contribution to the total reducing capacity is smaller than that of the other redox-active functional groups.