Accumulation Of Humic Acids Research Articles

Relationship between soil humus dissimilation, soil biological and chemical properties, and leaf litter characteristics in pure forests

Soil humus dissimilation in 8 kinds of pure forests was detected and its relationship with soil biological and chemical properties and leaf litter characteristics was assessed using partial least squares regression (PLS-R). The results indicated that: The particular soil properties in pure forest rather than the litter characteristics exhibited the dominant impacts on humus accumulation and degree of humifications. High soil microbial biomass carbon (MC), alkaline N and available P contents, soil phosphatase, dehydrogenase and urease activities, and litter accumulation were associated with high humic acid accumulation, while high soil available Fe and litter Mn contents were opposite. High soil MC, alkaline N, available Zn and P contents, and dehydrogenase and phosphatase activities were in favour of fulvic acid accumulation, while the high litter Mn content were opposite. High soil MC and alkaline N contents, dehydrogenase and phosphatase activities and high litter N content were associated with the accumulation of humin, in contrast, increase in soil available K and Zn contents and sucrase activity hindered this process. Increases in soil available K content, urease and peroxidase activities and litter accumulation and C/P ratio increased the degree of humifications of soil, while the increases in soil available Fe and Cu contents, catalase activity and litter P content significantly decreased it.

Removal of perfluorooctane sulfonates from water by a hybrid coagulation–nanofiltration process

Perfluorooctane sulfonates (PFOS) as a persistent, bioaccumulative and toxic pollutant has been detected in surface water around the world and attracted great attention in recent years. It’s important and urgent to develop effective technology to remove PFOS. The effect of coagulation pretreatment on the removal efficiency of PFOS by nanofiltration (NF) was investigated. Two types of NF membranes were used to test the PFOS rejections in three different solutions including DI water, humic acid (HA) solution and coagulation solution. The characterizations such as HA and PFOS accumulation on the membranes, scanning electron microscopy (SEM) and surface ζ potential analysis of virgin and fouled membranes were conducted to study the separation mechanism. The experimental results showed that PFOS can be partly removed by coagulation. The NF270 membrane exhibited a higher PFOS rejection (>95%) than the HYDRACORE membrane (40–60%) in single NF process. The surface negative charge density of both NF membranes reached a minimum value after filtering coagulation effluent, which might be a result of floc adsorption on the membrane surface. Coagulation pretreatment was effective to enhance the PFOS rejection of the NF membranes. In particular, the rejection efficiency of the HYDRACORE membrane increased from 55% to 86% at a trans-membrane pressure of 0.4MPa. The SEM images showed that the fouling layer formed by flocs was loose and highly permeable.

Partitioning of humic acids between aqueous solution and hydrogel. 2. Impact of physicochemical conditions.

The effects of the physicochemical features of aqueous medium on the mode of partitioning of humic acids (HAs) into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) were explored. Experiments were performed under conditions of different pH and ionic strength as well as in the presence or absence of complexing divalent metal ions. The amount of HA penetrating the gel phase was determined by measuring its natural fluorescence by confocal laser scanning microscopy. In both gel types, the accumulation of HA was spatially heterogeneous, with a much higher concentration located within a thin film at the gel surface. The thickness of the surface film (ca. 15 μm) was similar for both types of gel and practically independent of pH, ionic strength, and the presence of complexing divalent metal ions. The extent of HA accumulation was found to be dependent on the composition of the medium and on the type of gel. Significantly more HA was accumulated in PAAm gel as compared to that in alginate gel. In general, more HA was accumulated at lower background salt concentration levels. The distribution of different types of HA species in the gel body was linked to their behavior in the medium and the differences in physicochemical conditions inside the two phases.

Accumulation of alkaline and alkaline-earth elements in subcolloidal fraction of bottom sediment at the river-sea geochemical barrier

Data on the concentrations of alkaline (K, Li, Cs, Rb, Tl), alkaline-earth (Mg, Be), and other elements and humic acids in subcolloidal fraction of bottom sediment at river-sea geochemical barrier are given. Higher concentrations of Al and Mg is detected in river BS corresponding to the initial stage of water mixing. The increase in the concentrations of Li, Cs, and Rb is shown to best correspond to the accumulation of humic acids in marine deposits.

Partitioning of Humic Acids between Aqueous Solution and Hydrogel: Concentration Profiling of Humic Acids in Hydrogel Phases

The partitioning of the natural polyelectrolyte humic acid (HA) from an aqueous dispersion into a model biomimetic gel (alginate) and a synthetic polyacrylamide gel (PAAm) is explored. In both gels, the spatial distribution of HA in the gel body, as measured by confocal laser scanning microscopy, is markedly nonhomogeneous. A striking feature is the enhanced accumulation of HA in a thin film of thickness ca. 15 μm at the surface of the gel body, resulting in average local concentrations that are, for PAAm and alginate respectively, a factor of 10 and 4 greater than that in the bulk solution. The time dependence of accumulation in the surface film is predominantly controlled by the diffusive supply of HA from the aqueous medium, with a time constant on the order of 10(3) s for both gels. The concentration of HA within the bulk gel body differs significantly from that in the bulk aqueous medium: substantially higher for PAAm but much lower for alginate. The results are significant for understanding the nature and rate of sink/source functioning at permeable phases in contact with aqueous media, e.g., biofilms and gel-like layers at biological interfaces or employed in chemical speciation sensors.

Formalized analysis of associativity of morphogenetic types and humus condition of ground litter in marsh birch forests

There are six morphogenetic types of forest ground litter in the gradient of big grass-sphagnous-dead litter marsh birch forest: deeply degraded litter, half degraded litter, rhizomatous litter (coarsely degraded), peaty litter, turfy-formed litter, and turfy litter. The specificity of their biochemical transformations is caused by the accumulation of humic acids (HA), especially of the first fraction (HA-1), alongside the relatively steady background formation of fulvic acids. The C/N value suggests that the intensity of HA-1 formation is closely associated with the biological activity of the substrate. However, the indistinct difference of these parameters in the forestry-morphological types of litters limits their diagnostic reliability. Grouped biochemical types of litters, such as “soft” (half- and deeply degraded), “intermediate” (rhizomatous, peaty and turfy-formed), and “coarse” (mossy), are considerably discriminated by both the C/N ratio (20, 30, 40) and the level of HA-1 (14, 10, and 6%) respectively.

Deactivation of nanoscale zero-valent iron by humic acid and by retention in water

The effects of the deactivation of nanoscale zero-valent iron (NZVI), induced by humic acid (HA) and by the retention of NZVI in water, on nitrate reduction were investigated using a kinetic study. Both the nitrate removal and generation of ammonia were significantly inhibited as the HA adsorption amount and retention time were increased. However, HA removal was greatly enhanced when the NZVI was used after 1 d or 25 d of retention in water. The results are caused by the formation of iron oxides/hydroxides, which increased the specific surface area and the degree of NZVI aggregation which was observed by transmission electron microscopy (TEM). However, the nitrate reduction was greater at the beginning of reaction in the presence of HA when fresh NZVI was used, because of the enhanced electron transfer by the HA in bulk phase and on NZVI surface as train sequences. The pseudo second order adsorption kinetic equation incorporating deactivation and a Langmuir-Hinshelwood (LH) type kinetic equation provided accurate descriptions of the nitrate removal and ammonia generation, respectively. The deactivation constant and the reaction rate constant of the LH type kinetic equation were strongly correlated with the HA amount accumulated on NZVI. These results suggest that the HA accumulation on the NZVI surface reactive sites plays the dominant role in the inhibition and the inhibition can be described successfully using the deactivation model. The HA accumulation on NZVI was verified using TEM.

Humic acid characteristics and effects on the reactivity of nano-scale zero-valent iron particles during nitrate reduction

ABSTRACT Humic acid (HA) comprises a significant fraction of natural organic matter (NOM), greatly influencing the performance of water and wastewater treatment processes. HA is expected to significantly affect the reactivity of nano-scale zero-valent iron (NZVI), which is receiving increasing attention due to its high reactivity. The effects of HA on nitrate reduction by NZVI were investigated to evaluate the potential of NZVI in practical applications. HA was characterized to identify the mechanism whereby HA affects. Nitrate reduction was enhanced at low HA concentration, but inhibited as HA concentration increased. HA decreased to reach a plateau and considerable amount of Fe3+ was detected when HA was present in dissolved phase. The increase in the degree of condensation of HA was verified by UV–vis spectroscopy, fluorescence spectroscopy, and size exclusion chromatography. Fourier transform infrared spectra confirmed that the Fe3+–HA complexes were formed in both the dissolved and solid fractions, without coexisting metal ions. The HA aggregation on NZVI and discrete HA macroaggregates were observed by transmission electron microscopy. The results suggest that HA induces complex effects on NZVI reactivity by improving iron dissolution, inhibiting readsorption of released iron, enhancing electron transfer, and inhibiting nitrate mass transfer via forming HA accumulation. It indicates that the clogging by aggregated NOM should be considered when NZVI is used for groundwater treatment or in combination with porous materials.

Rhizosphere humic acid interacts with root cell walls to reduce hydraulic conductivity and plant development

Humic acids are ubiquitous, organic-end-products of the chemical and microbial degradation of dead biota in soils throughout the world. Humic acids can be transported in soil water as heterogeneous, supra-molecular, colloidal-agglomerates. Humic acid accumulation in the rhizosphere of transpiring plants may chemically stimulate development by increasing root availability of mineral nutrients and/or growth regulatory biomolecules. This report introduces novel, physical mechanisms by which humic acid can also reduce plant development. Effects of humic acid addition to the root media of intact maize plants (Zea mays L.) on their growth, transpiration and resistance to water deficits were assayed, as were the effects of external humic acid on the hydraulic conductivity of excised primary-roots. Humic acid reduced shoot growth, transpiration and resistance to water stress but not root growth. Root hydraulic conductivity was reduced by up to 44% via a time-, concentration- and size-dependent fouling mechanism resulting from humic acid accumulation at root cell-walls. Thus, humic acid is shown, apparently for the first time, to be able to exert novel physical effects in addition to its known chemical effects on plant development.

Evolution of organic matter fractions after application of co-compost of sewage sludge with pruning waste to four Mediterranean agricultural soils. A soil microcosm experiment

The effect of co-compost application from sewage sludge and pruning waste, on quality and quantity of soil organic carbon (SOC) in four Mediterranean agricultural soils (South Spain), was studied in soil microcosm conditions. Control soil samples (no co-compost addition) and soils treated with co-composts to a rate equivalent of 140 Mg ha −1 were incubated for 90 days at two temperatures: 5 and 35 °C. The significances of incubation temperature and the addition of co-compost, on the evolution of the different fractions of SOC, were studied using a 2 3 factorial design. The co-compost amendment increased the amounts of humic fractions: humic acids (HA) (1.9 times), fulvic acids (FA) (3.3 times), humin (1.5 times), as well as the free organic matter (1.4 times) and free lipids (21.8 times). Incubation of the soils enhanced its biological activity mainly in the amended soils and at 35 °C, leading to progressive SOC mineralization and humification, concomitant to the preferential accumulation of HA. The incubation results show large differences depending on temperature and soil types. This fact allows us to select suitable organic amendment for the soil when a rapid increase in nutrients through mineralization is preferred, or in cases intending the stabilization and preservation of the SOC through a process of humification. In soils with HA of more than 5 E 4/ E 6 ratio, the incubation temperature increased rates of mineralization and humification, whereas lower temperatures limited the extent of both processes. In these soils the addition of co-compost in spring or summer is the most recommendable. In soils with HA of lower E 4/ E 6 ratio (<5), the higher temperature favoured mineralization but not humification, whereas the low temperature maintained the SOC levels and even increased the HA/FA ratio. In these soils the moment of addition of organic amendment should be decided depending on the effect intended. On the other hand, the lower the SOC content in the original soil, the greater are the changes observed in the SOC after amendment with co-compost. The results suggest that proper recommendations for optimum organic matter evolution after soil amendment is possible after considering a small set of characteristics of soil and the corresponding soil organic matter fractions, in particular HA.

Accumulation of Humic Acid in DET/DGT Gels

Gel layer based sensors are increasingly employed for dynamic trace metal speciation analysis in aquatic and soil media. In DGT (Diffusive Gradient in Thin film), polyacrylamide hydrogels are commonly used for the diffusive gel layer. While some effects of humic and fulvic acids on the DGT detection of metal species have been observed, the gel permeation properties of the actual humic and fulvic acid compounds themselves have not been analyzed thus far. Here we show with DET (Diffusive Equilibrium in Thin film) that these natural complexing agents do enter the gel layer, and that humic acids even appear to accumulate in the gel, with enrichment factors typically on the order of 10. The results have consequences for the interpretation of DGT-data on metal fluxes from aquatic media containing humics and fulvics.

Accumulation of Soil Carbon and Phosphorus Contents of a Rehabilitated Forest

The world's tropical rainforests are decreasing at an alarming rate as they are converted to agricultural land, pasture, and plantations. Decreasing tropical forests affect global warming. As a result, afforestation progams have been suggested to mitigate this problem. The objective of this study was to determine the carbon and phosphorus accumulation of a rehabilitated forest of different ages. The size of the study area was 47.5 ha. Soil samples were collected from the 0-, 6-, 12-, and 17-year-old rehabilitated forest. Twenty samples were taken randomly with a soil auger at depths of 0–20 and 20–40 cm. The procedures outlined in the Materials and Methods section were used to analyze the soil samples for pH, total C, organic matter, total P, C/P ratio, yield of humic acid (HA), and cation exchange capacity (CEC). The soil pH decreased significantly with increasing age of forest rehabilitation regardless of depth. Age did not affect CEC of the rehabilitated forest. Soil organic matter (SOM), total C, and total P contents increased with age. However, C/P ratio decreased with time at 0–20 cm. Accumulation of HA with time and soil depth was not consistent. The rehabilitated forest has shown signs of being a C and P sink.

PH, Ionic strength and flow velocity effects on the NOM filtration with TiO 2/ZrO 2 membranes

The effects of pH, ionic strength and flow velocity on the volumetric permeate flux and the rejection of dissolved organic carbon (DOC) in a 15 kDa ceramic ultrafiltration membrane are evaluated. The decrease of pH produces a drop in the elimination of DOC, despite humic acid accumulation in the surface of membrane. Membrane has a lower humic acid flux resistance when pH decreases due to molecular compression of humic acid. Ionic strength has a relevant influence in humic substances processed with ceramic ultrafiltration membranes. A significant permeate flux reduction is approached when ionic strength increases as well as DOC removal reduction. Regarding the ionic strength rise, it can be observed that the resistance of the cake layer falls as in the case of falling pH. On the other hand, permeate flux rises due to the reduction of the effective size of the molecule. Concerning flow velocity, permeate flux reduction plays a significant role in contrast to DOC removal. Low flow velocity allows cake layer formation that considerably reduces flux permeate. Experiments carried out at neutral pH and low ionic strength, to analyse flow velocity, show no electro kinetic effects that influence the cake layer formation and flux permeate.

Studies on nanofiltration membrane fouling in the treatment of water solutions containing humic acids

A major factor limiting the use of nanofiltration (NF) in the water treatment process is membrane fouling by natural organic matter. Two NF membranes, Desal 5 DK and DL, which have different hydraulic permeabilities, were compared. Solution chemistries selected for this investigation were concentrated on the common salts found in a variety of wastewaters, including monovalent ions (Na +, Cl −), divalent hardness cations (Ca 2+, Mg 2+) and divalent anions (SO 2− 4). Results of fouling experiments with humic acids demonstrated that the condition of hydrodynamics and the chemical compositions of the feed solutions could significantly influence the fouling tendency. Higher crossflow velocity and lower initial flux mitigated accumulation of humic acid (HA) on the membrane to some extent. The adsorption of humic substances onto the membrane surface was markedly enhanced in the presence of divalent cations due to the formation of HA-complexed divalent cations. The experiment also indicated that the membrane surfaces preferred to adsorb divalent cations rather than divalent anions because the membrane had a negative charge in the higher pH range investigated. In addition, choosing a proper divalent cation chelating agent as a cleaning reagent, especially at basic conditions, can improve the membrane process by dissolving and removing the HA fouling substance.

Changes in the composition of hydrolyzed lignin during composting

Microbial assemblages were composed for composting hydrolysed lignin. Data on bioconversion of aromatic compounds with various types of substitution in the ring were used for this purpose. Composting of hydrolysed lignin reduced the contents of lignin, low-hydrolyzable polysaccharides, resins, and low-molecular-weight phenols and resulted in accumulation of humic acids. The resulting compost showed no phytotoxicity.

Comparison of humus composition in the subsoil of Japanese Paddy and upland fields

Characteristics of the humus composition in the subsoil of paddy fields were examined in two studies. Humus composition of the subsoil samples collected from paddy (n=31) and upland (n=20) fields in Aichi and Gifu Prefectures, central Japan, was compared statistically (Study I). Humification degree of HAs was compared between the profiles of paddy fields and adjacent upland fields on two diluvial soils (Study II). Humus was extracted with 0.1 m NaOH and 0.1 m Na4P2O7 successively, fractionated into humic acid (HA) and fulvic acid (FA) fractions. The HAs were classified into Types A, E, P, Rp based on their spectrophotometric properties. Forty one out of 51 Na4P2O7-extractable HA samples from the subsoil of paddy and upland fields belonged to Type A. Type E or Type Rp HAs were often found in the subsoil of Strong Gley Lowland soils and diluvial soils. Although no difference in the spectrophotometric properties was found between HAs from alluvial paddy (n=24) and alluvial upland (n=17) soils, the amount of Na4P2O7-extractable HAs in the subsoil was significantly larger in paddy fields than in upland fields. The other characteristics of the humus composition in the subsoil of paddy fields compared with those of upland fields were the lower proportion of extractable humus in total carbon (C), mainly due to a lower amount of NaOH-extractable FAs, and a higher proportion of Na4P2O7-extractable HAs in total HAs and in total C. Humification degree of the Na4P2O7-extractable HAs in the subsoil of diluvial upland fields decreased with depth, most of them belonged to Type B. On the contrary, the humification degree of the same fraction from the adjacent paddy fields was high even in deeper layers, all the samples except for one were classified into Type A (Study II). Therefore, it was concluded that the accumulation of Na4P2O7-extractable HAs belonging to Type A is a characteristic of humus in the subsoil of well drained paddy fields.

Influence of Humic Acid on Water Adsorption Characteristics of Kaolin and Quartz

AbstractWater vapor adsorption isotherms were measured for samples of kaolin and quartz amended with different amounts of humic acid extracted from a Cambic Arenosol under forest. Applying the approximation of the adsorption isotherms with the BET equation the monolayer capacities (surface areas) for the studied systems were calculated. For kaolin systems the surface area decreased sharply at low humic acid additions and this slowly increased with the further rise of the humic acid content, whereas for the quartz the increase of surface area was only noted for high humic acid contents. Using an exponential isotherm equation with a local BET model, the adsorption energy distribution functions were calculated for kaolin systems. The shape of the adsorption energy distributions showed that the increase in humic acid content changed the character of the surface from more hydrophilic to more hydrophobic. For intermediate humic acid contents, the energy distribution function had two maxima – more polar and less polar. At high humic acid contents the energy distribution function tended to the estimated value for pure humic acid, indicating high surface coverage with organic material.As measured by the mercury intrusion porosimetry, for the kaolin samples the amount of the largest pores decreases and the amount of the smallest pores increases with the accumulation of humic acid. For the quartz systems only very high doses of humic acid are reflected in changes of pore size distribution.

Interactions between Organic and Inorganic Components in Particle‐Size Fractions Separated from Four Soils

AbstractLittle information is available in the literature on the mechanism(s) of interaction of organic matter (OM) and inorganic crystalline and noncrystalline components in particle‐size fractions. To obtain a better understanding of this subject, five particle‐size fractions, ranging from coarse silts to fine clays, were separated from two soils from eastern Canada (Armadale and Bainsville) and from two prairie soils (Melfort and Regina). Each size fraction was characterized by chemical and mineralogical methods. Humic acids (HAs), fulvic acids (FAs), and humins were found to accumulate in size fractions ranging from medium silts to coarse clays, while aliphatics were concentrated in fractions from medium silts to fine clays. Amino acids tended to be enriched in clay fractions of the two prairie soils, but accumulated in the silt fractions separated from the two soils from eastern Canada. Except for one soil, NH3‐N accumulated in the fine silt and finer fractions, which were rich in expandable phyllosilicates. In general, amounts of OM, aliphatics, and NH3‐N tended to accumulate in fractions rich in noncrystalline inorganics. Noncrystalline inorganics separated from the two prairie soils were rich in Si, which appeared to contribute to the preferential accumulation of humin, HA, and neutral amino acids. On the other hand, noncrystalline components from the two soils from eastern Canada were rich in Al, which may have been associated with the accumulation of NH3‐N and acidic amino acids in these soils. The pH‐dependent charges of noncrystalline inorganics may also have contributed to the accumulation of OM.