Levels Of Humic Acid Research Articles

Analyzing bacterial community in pit mud of Yibin Baijiu in China using high throughput sequencing.

“Yibin Baijiu” (YB) is a special Chinese strong-aroma Baijiu (CSAB) that originated in Yibin, a city in western China. YB is fermented in cellars lined with pit mud (PM), the microbiota in which may affect YB quality. In this study, high throughput sequencing of the 16S rRNA gene was used to demonstrate the bacterial community structure and diversity in PM of YB. In addition, the physicochemical characteristics of PM were also analyzed, including moisture content, pH, and available phosphorous, ammonia nitrogen, and humic acid levels. Results showed that Firmicutes was the dominant phylum in all PM samples with abundance > 70.0%, followed by Euryarchaeota (11.3%), Bacteroidetes (6.5%), Synergistetes (3.0%), Actinobacteria (1.4%), and Proteobacteria (1.2%). Furthermore, 14 different genera with average relative abundance of > 1% were detected. The Chao1 and Shannon indexes did not vary significantly between the sub-layer and middle-layer PM (P > 0.05). However, Linear discriminant analysis Effect Size (LEfSe) analysis showed that the relative abundance of Lactobacillus in the sub-layer PM was significantly higher than in middle-layer PM. pH differed significantly (P < 0.05) between the two groups. Canonical correspondence analysis revealed that bacterial community in PM correlated significantly with available phosphorous content and pH. Our study provides basic data for further elucidating the diversity of microbiota in the PM of YB and the potential mechanism of Baijiu production.

Effects of heavy metals released from sediment accelerated by artificial sweeteners and humic acid on a green algae Scenedesmus obliquus

Artificial sweeteners (ASs) are emerging polar organic contaminants, which can chelate with heavy metals in the environment. Recently, the ASs have been widely detected in the aquatic environment. However, little is known about the influence of ASs on the mobility and toxicity of heavy metals associated in sediment. In the present study, the release of heavy metals from a lake sediment and the toxicity to a green algae Scenedesmus obliquus were examined in the presence of two most frequently detected ASs, acesulfame and sucralose, and humic acid (HA), respectively. The existence of 1.00–100 mg/L of acesulfame, sucralose, and HA enhanced the release rates (Rrelease) of Cd, Cu, and Pb from the virgin lake sediment significantly by up to 46.7%, 86.0%, and 79.9%, respectively. Further, the results from microcosm experiments revealed that the existence of 1.00–10.0 mg/L of acesulfame, sucralose, and HA in the water phase prompted the release and toxicity of heavy metals associated with Cd- and Cu-spiked sediment, and the promotion capacity followed the order of HA > acesulfame > sucralose. The inhibitions on cell-specific growth rate (μ) of the algae were found increasing significantly with the elevated levels of acesulfame and HA (p < 0.05). Additionally, photosynthesis of the algae was affected by the co-existence of ASs or HA and heavy metals released from sediments, as indicated by the changes in fluorescence parameters. The present study provides valuable insight into the likelihood of the combined effect of ASs and heavy metals on aquatic organisms.

Rice straw addition and biological inoculation promote the maturation of aerobic compost of rice straw biogas residue

Rice straw biogas residue contains high lignin content, so the decomposition of this material by natural compost is slow. This study investigated the effect of the combination of rice straw addition and microbial inoculation (Aspergillus niger CICIMF0410 and Phanerochaete chrysosporium AF96007) on the physiochemical properties of rice straw biogas residue in the composting process. Four composting treatment groups were designed: rice straw biogas residue (RR; T1), RR + rice straw (RS) (T2), RR + inoculants (T3), and RR + RS + inoculants (T4). The addition of rice straw significantly accelerated the initial temperature rise during composting, and microbial inoculation accelerated lignocellulose decomposition. After composting, the electrical conductivities of samples T1 to T4 were 1.22, 0.87, 0.99, and 0.82 DS ml−1, respectively. Compared with other treatment samples, T4 showed noticeably increased degradation rates of HC, CL, and ADL after decomposition. The total humic acid levels of samples T1 to T4 were 9.5, 12.7, 10.5, and 18.6%, with humification index values of 1.45, 1.80, 1.69, and 2.46, respectively, after maturation. After 12 weeks of composting, T4 showed the highest increase in total nitrogen (37.6%), phosphorus (33.6%), and potassium (29.8%) levels. Furthermore, compared with other treatment samples, T4 showed the best maturity indices, such as morphology, color, and odor. Rice straw addition and biological inoculation for biogas residue composting not only significantly decreases the time required for decomposition but also eliminates the toxicity risk for crops and improves the stability of the biogas residue fertilizer.

Detection of humic acid in water using flat-sheet and folded-rod viscous alkaline glucose syrups.

The utility of a low-cost biocompatible material for the detection of pollutants in water is highly essential to ensure safety and economic efficiency. In this paper, solutions of two viscous alkaline glucose syrups (AGS@22-sheet and AGS@60-rod), obtained under two different temperature conditions (22 °C and 60 °C) were used to detect low levels of humic acid (HA), a carcinogen pro-molecule and metal-complexing agent in an aqueous solution. The AGS materials were characterized using ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy and scanning electron microscopy (SEM). By evaluation, a detection limit (LOD) as low as 4.6 × 10-5 mg L-1 was obtained. The sensing capability of the new technology was further extended to the detection of HA in a real water sample (tap water) using the standard addition method with 98 and 100.05% recoveries. The sensing was improved in the presence of sodium acetate and sodium citrate and was found to follow a pseudo-first order reaction. These findings show that the as-synthesized glucose syrups have the potential to detect humic acid in water and thus may be employed for the quantification of HA in water treatment plants or textile industry.

Response of soil applied lignite coal derived humic acid on yield and quality of spinach (Spinacia oleracea L.)

A pot experiment was carried out in the net house of the Department of Soil Science &amp; Agricultural Chemistry, Banaras Hindu University, Varanasi, Uttar Pradesh during rabi season of 2017-2018, to study the effect of lignite coal derived humic acid (HA) on growth and development of spinach (Spinacia oleracea L.) in an Inceptisol of Varanasi, Uttar Pradesh with six doses of lignite coal originated humic acid [ i.e. 0.0 (H0), 0.5 (H1), 0.75 (H2), 1.5 (H3), 2.5 (H4) and 5.0 (H5) mg HA kg-1 of soil] and four doses of N (urea) fertilizer [0.0 (N0), 18.50 (N1), 27.80 (N2) and 37.0 (N3) mg kg-1 soil] in different combination. The plant growth parameters (viz. no. of leaves, fresh weight &amp; dry weight) and biochemical parameters (viz. brix value, chlorophyll, nitrogen and protein content) were taken at 30, 45 and 60 days after sowing. The highest values of yield and quality parameters was recorded in the treatment, where higher level (5 mg kg-1 soil) of humic acid was applied with full dose of nitrogen (37.0 mg kg-1 soil) through urea fertilizer. The application of humic acid with nitrogen fertilizers in soil was noticed to be promising technique in increasing yield and quality of spinach.

Composition of organic C fractions in soils of different texture affected by sugarcane monoculture

ABSTRACT Sugarcane is a strategic commodity in Indonesia. It is usually raised in a monoculture system. There is a lack of information about the effects of extended sugarcane monoculture on the soil carbon fraction. The aim of this study was to determine the relative changes in the soil organic C fractions in response to the duration of sugarcane monoculture on Entisols, Inceptisols, and Vertisols. The measured variables were the percentages of sand, silt, and clay, organic matter (OM), total nitrogen (TN), pH (H2O), cation exchange capacity (CEC), NH4 +, NO3 -, labile carbon fraction (soil carbon mineralization (C-Min), soil microbial carbon (C-Mic), and carbon particulate organic matter (C-POM)), and stable carbon fraction (humic and fulvic acids). Soil type with sugarcane monoculture period had significant influences on the percentages of clay, sand, silt, CEC, and pH (H2O). Soil type and sugarcane monoculture period had no apparent significant effect on C-Min or C-POM but did significantly influence C-Mic. The humic and fulvic acid levels in all three soil types were affected by the duration of sugarcane monoculture. To establish the impact of long-term sugarcane monoculture on the physicochemical properties of soils with various textures, it is more appropriate to measure the soil stable carbon fractions such as humic and fulvic acid rather than the soil labile carbon fractions such as C-Min, C-POM, or C-Mic.

The effect of tropical peat land-use changes on plant diversity and soil properties

Alterations in land use of a million hectares of peatlands in Central Kalimantan and other regions, without an understanding of the characteristics of tropical peatlands, have led to land degradation. This study aimed to determine the effect of land-use changes on plant diversity and soil characteristics of peatlands in Central Kalimantan, Indonesia. The conversion of secondary forests to critically degraded land, acacia forest, agroforestry land, rubber gardens, and palm oil plantations by clear-cutting and fire converted organic materials to available nutrients and increased soil pH at the soil surface. However, the nutrients are easily leached by high rainfall intensity thus resulted in a more degraded land at long-term periods. Land-use change resulted in high humic acid levels, aromatic area, hydrophobic surface area, but low water storage capability. This condition made it easily burn during the dry season and is prone to flooding during the rainy season. The Shannon indexes for all tropical peatland land uses at all levels of plant growth categorized plant diversity and number of individuals as low to moderate due to waterlogging, low pH, low soil fertility, high metal toxicity, and fire. Land with oil-, sap- and litter-producing plants, which resist decomposition, and monoculture plantations tended to contain higher amounts of humic acid, hydrophilic areas, aromatic areas, and bulk density than naturally regenerated forests, although these land uses had lower organic C, available N, and water-holding capacity. Closed cycles of organic matter, carbon, water, nutrient, energy, production, and crops should be maintained for rehabilitation of peatland.

Freeze-thawed humic acid/polyvinyl alcohol supramolecular hydrogels

Novel supramolecular hydrogels were prepared on the basis of polyvinyl alcohol loaded with different amounts of humic acid nanoparticles via a freezing-thawing method. The results showed the humic acid nanoparticles act as functional sites to aggregate the polyvinyl alcohol chains and result in the formation of three-dimensional supramolecular networks. It was shown that the humic acid nanoparticles can interact with the polyvinyl alcohol chains and interconnect the polymeric chains as functional crosslinkers. The results showed up to 3.4 % increase in the gel fraction value of polyvinyl alcohol hydrogel by incorporating humic acid nanoparticles. In addition, 2.5 and 5.7 °C increases in the glass transition temperature and the melting point of polyvinyl alcohol hydrogel were observed by incorporating 9 wt.% of humic acid, respectively. By incorporating the mentioned level of humic acid, up to 87 and 26 % increases were observed in the storage modulus at glassy state and crystallinity of polyvinyl alcohol hydrogel.

Effect of humic acid and seaweed extract (ALGA) on growth characteristics and nutrient content of local apricot seedlings Prunus armeniaca L.

The research was carried out at the Plant canopy of the Department of Horticulture and Landscape, College of Agriculture, University of Kerbala during the growing season of 2016. A factorial experiment with two factors designed. In accordance of randomized completely block design R.C.B.D. to study the effect of spraying with three levels of humic acid (0, 5 and 10 cm3.l−1)and three levels of Alga seaweed extract (0, 1 and 1.5 cm3.l−1)on some vegetative, root growth characteristics and leaf content of mineral elements N, P, K for local apricot seedlings. Treatments with three replicates. Each containing 45 seedlings with five seedlings per experimental unit were adopted. The results showed that a significant increase in plant height, stem diameter, number of leaves, leaf area, leaf content of chlorophyll, nitrogen, phosphorus and potassium, dry weight of shoot, root length, and dry weight of root was noticed when treated with humic acid or seaweed extract (ALGA) alone or jointly compared with control treatment. The interaction between treatments measured at a concentration of 10 cm3.l−1 humic acid and 1.5 cm3.l−1. Alga the highest significant increase in the vegetative, root and leaf content of N.P.K for apricot seedlings was observed.

Characterization of DOC and CDOM and their relationship in turbid waters of a high-altitude area on the western Loess Plateau, China.

Dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM) in rivers and reservoirs on the western Loess Plateau, which is an area of severe soil erosion, were investigated in September 2017 to analyze the CDOM characteristics and composition, DOC distribution and influence of environmental factors on these parameters. Great differences of water parameters were exhibited between different groups based on the analysis of variance (p < 0.01). The results indicated that rivers exhibited higher DOC concentrations (mean: 3.70 mg/L) than reservoir waters (mean: 2.04 mg/L). Artificial and agricultural lands exert a large influence on DOC concentrations, which verifies the hypothesis that intense anthropogenic activity results in high DOC concentrations. The CDOM absorption at 350 nm [aCDOM(350)] of tributary water samples was 2.73 m-1, which was higher than that in the Yellow River (1.71 m-1) and reservoir waters (1.33 m-1). The effects of DOC, TC and turbulence (Tur) on CDOM are positive and significant (p < 0.05) according to the multiple linear regressions. An analysis of the optical characteristics of CDOM indicated that waters on the Loess Plateau contained abundant humic acid and higher levels of allochthonous DOM with a higher molecular weight (MW) based on the spectral slopes (S) and specific UV absorbance (SUVA254) values.

SOME CATIONS MOVEMENT IN CALCAREOUS SOIL COLUMNS UNDER EFFECT OF SALINE WATER MIXED WITH HUMIC ACID

A laboratory experiment was conducted to study the impact of humic acid with different levels of saline water on the movement of Sodium, Calcium and Magnesium, and the kinetics of Sodium adsorption ratio in calcareous soil with a texture clay loam using the mixing displacement techniques. The soil was taken from the surface layer (0-30 cm), air dried and passed through a 2 mm diameter sieve. It was filled in columns of polyethylene. A fixed column of water was placed above the surface of the soil column of different salinity water (0.72, 3.00, 5.00 and 7.00 dSm-1), in accordance with humic acid levels of 0.00, 0.25 and 0.50 g L -1. The process of washing and collecting leachate continued daily. The amount of Sodium, Calcium and Magnesium in the water filtered over time. The results showed that the amount of Sodium released increases with the levels of added humic acid and any levels of saline water used. The amount of Calcium and Magnesium released decreases with time and increases the added levels of the humic acid and any levels of saline water used. Diffusion equation is the best equation described the movement of salt.

Detection of low-level humic acid in water using room temperature-synthesized copper (I) oxide colloids

Abstract

Antimony speciation and mobility during Fe(II)-induced transformation of humic acid-antimony(V)-iron(III) coprecipitates

Antimony, as the Sb(V) species, often occurs in oxic soils and sediments as coprecipitates with poorly-crystalline Fe(III)-bearing minerals. It is common for these Sb(V)-Fe(III) coprecipitates to also contain varying quantities of co-occurring humic acid (HA). When exposed to reducing conditions, the production of Fe(II) may cause the initial metastable HA-Sb(V)-Fe(III) phases to undergo rapid transformations to more stable phases, thereby potentially influencing the geochemical behavior of coprecipitated Sb(V). However, little is known about the impacts of this transformation on the mobility and speciation of Sb. In this study, we reacted synthetic HA-Sb(V)-Fe(III) coprecipitates (Fe:Sb ratio = 4, and C:Fe molar ratios = 0, 0.3, 0.8 and 1.3) with 0, 1 or 10 mM Fe(II) under O2-free conditions at pH 7.0 for 15 days. Fe K-edge EXAFS spectroscopy revealed that solid-phase Fe(III) in the initial coprecipitates contained a mixture of ∼4/5 ferrihydrite (Fe10O14(OH)2) and ∼1/5 tripuhyite (FeSbO4), regardless of the corresponding amount of coprecipitated HA. Tripuhyite persisted throughout the full experiment duration, while ferrihydrite was partially replaced by goethite (FeOOH) when either 1 or 10 mM Fe(II)aq was added to the coprecipitates. The greatest level of goethite formation (∼55% of solid-phase Fe) was observed in the HA-free/10 mM Fe(II)aq treatment, with ferrihydrite transformation being partially attenuated at higher levels of HA. Mobilisation of aqueous Sb was the greatest for 1 mM Fe(II) treatments at high HA:Fe ratios. Sb K-edge XANES spectroscopy showed that the largest reduction of Sb(V) to Sb(III) (∼37%) and the greatest repartitioning of Sb to the mineral surface (∼7.9–9.8%) occurred in the coprecipitates with the highest HA contents in the presence of 10 mM Fe(II). The results indicate that the amount of HA in HA-Sb(V)-Fe(III) coprecipitates can greatly influence mobility and speciation of Sb in Fe(II)-rich conditions. The results of this study provide new insights into alterations in Sb mobility and retention in response to Fe cycling under organic matter-rich reducing conditions.

Influence of nano-silica and humic acid on physiological characteristics of Bermuda grass (Cynodon dactylon L.) under salinity stress

This research was conducted to evaluate the effects of water salinity and nano-silica (NS) and humic acid (HA) on Bermuda grass. The study was carried out under greenhouse and exterior space conditions in a completely randomized design with factorial arrangements. Treatments included 4 water salinity levels (0, 5, 7 and 9 dS/m) and 4 level of NS (0, 1, 2 and 3 mm/l) as well as 4 level of HA (0, 50, 100 and 150 mg/l). Results indicated a decrease in chlorophyll content, and increase in proline, malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD) and electrolyte leakage (EL) with increasing levels of salinity. The chlorophyll content in greenhouse and exterior space also increased with increasing levels of NS and HA, while proline in two environments, with increasing levels of NS and HA decreased. EL with increasing levels of NS fluctuated, but with increasing levels of HA, it decreased in two environments. With increasing levels of NS, CAT in both environments was eventually decreased after the oscillation, but there was no particular trend in HA levels. With increasing levels of NS and HA, MDA in the greenhouse decreased and in the exterior space – it increased. Finally, by increasing levels of NS and HA, SOD did not show any change in the greenhouse condition, but in the exterior space, the SOD was decreased.

EFFECT OF APPLYING HUMIC ACID AND FOLIAR FERTILIZATION WITH POTASSIUM ON GROWTH AND YIELD OF Zea mays L.

A factorial experiment was conducted in clay loam soil at a farm belonging to Salam city, 25 km northeast of Baquba during autumn season 2015, to study the effect of applying humic acid and foliar fertilization with potassium and their interaction on growth and yield of maize (Zea mays L.), synthetic variety 5018 was used. Randomized Complete Block Design (R.C.B.D) with three replications was used. Four levels of humic acid (0, 0.5, 1, and 2 g m-2), and four levels of potassium (0, 1000, 2000, and 3000 mg K l-1 as potassium sulfate 41.5 % K) were used. The results showed that humic acid 2 g m-2 had a significant effect on plant height which gave 204.866 cm, leaf area 588.120 cm2, chlorophyll index 55.213 SPAD, the weight of 500 grain 154.096 g, and plant yield 256.356 g plant-1. While spraying with potassium at a concentration of 3000 mg K l-1 gave the highest plant height 205.000 cm, leaf area 585.933 cm2, chlorophyll index 54.904 SPAD, the weight of 500 grain 153.645 g, and plant yield 253.072 g plant-1.

Effect of Different Levels of Humic Acid and Mineral Fertilizers on Growth and Productivity of Sunflower

Two field experiments were conducted out at Itay EL-Baroud Agricultural Research Station to investigate the effect of different levels of humic acid and mineral fertilization alone or in combination on two sunflower cultivars, Sakha 53 and G102 during two summer seasons 2016 and 2017. The treatments were, i.e. T1 (100% mineral fertilizers + zero humic acid), T2 (75% mineral fertilizers + 2 litters of humic acid/feddan), T3 (50% mineral fertilizers + 2 litter of humic acid/feddan), T4 (50% mineral fertilizers + 1 litter of humic acid/feddan) and T5 (0% mineral fertilizers + 2 litter of humic acid/feddan), foliar application of humic was done on 25, 35 and 45 day after sowing (DAS). The experiments were designed in RCBD using split plot with three replications. The results indicated that highly significant difference were found between sunflower cultivars, also found between fertilization treatments during the two seasons, Sakha 53 recorded the best values for plant height, head diameter , seed yield/plant and seed yield/fad, while Giza 102 achieved desirable values for days to flowering and oil %. The treatments T1 and T2 exhibited the best results for most studied characters such as plant height, head diameter (cm), stem diameter (cm), no. of seeds/plant, 1000-seeds weight/plant and seed yield/fad with exception of oil % and physiological maturity date. Best value of benefit cost ratio was obtained by T1 and T2 among treatments and Sakha 53 compared to Giza 102.

Effect of Humic acid levels on fodder production of maize (Zea mays) varieties under agro-climatic conditions of Tandojam-Sindh Pakistan

In Pakistan, maize is the fourth largest grown crop after wheat, cotton, rice and is considered as fodder for livestock as well. There are various reasons for low productivity of this crop which includes low soil organic matter (O.M). Chemical fertilizers indiscriminate utilization disturbs the soil tithe and its chemical composition which caused in reduction plant yield. Hence to overcome the problem of this low fertility, humic acid is strongly recommended throughout the world. Hence and research experiment was conduct as student’s Agronomy experimental farm, at Sindh Agriculture University Tandojam, Pakistan during the year 2017 on humic acid levels effect on fodder production of maize (Zea Mays). The experiment was designed by following the randomize complete block design (RCBD) with net plot size 3 by 4 m (12 m.seq). The experiment comprises of the recommended dose of NPK and various levels of humic acid such as HA1 = Untreated, HA2 = 2 kg ha-1, HA3 = 3 kg ha-1 and HA4 = 4 kg ha-1. The results of our study showed that significant effect on different levels of humic acid on the different varieties of maize crop. The results revealed that the application of humic acid @4Kgha-1 gave maximum yield and better growth of maize varieties as compared to lower levels of humic acid application where as in varieties Akbar and Sadaf produced maximum fodder yield than variety Neelum in response to humic acid application. Keywords: Fodder production; Humic acid levels; Maize (Zea mays L.) http://dx.doi.org/10.19045/bspab.2019.80108

Effects of humic acid and cow manure biochar (CMB) in culture medium on growth and mineral concentrations of basil plant.

In sustainable agriculture, protection of the ecosystem and reduce chemical fertilizers are the main goals. Nowadays, sweet basil, one of the best general fragrant foliage, is considered as an industrial plant. In present study to compare different levels of cow manure biochar (CMB) and humic acid (HA) on vegetative traits and mineral absorption rate of green basil plants, an experiment was conducted based on a completely randomized block design with four replications in 2015. The treatments included different levels of CMB (0, 1%, 2%, and 3%) and HA (2.5, 5 and 7.5 g/L) in the culture medium. The traits that were analyzed were included: plant height, leaf number, leaf area, stem diameter, leaf chlorophyll concentration (LCC), fresh and dry weights of aerial part and root, concentration of potassium, nitrogen, calcium and phosphorus. Results showed that fresh and dry weights of shoot and root were increased by application of 3% CMB and 7.5 g/L HA in the culture medium. Theuse of CMB and HA significantly affected most of the studied traits except LCC, stem diameter, and leaf area. Concentration of N, P, K and Ca was considerably increased by application of 3% CMB and 7.5 g/L HA in the culture medium. The highest concentration of nutrients was detected in the plants treated with 3% CMB. In conclusion, the use of 3% CMB and HA at 7.5 g/L in the culture medium can be recommended to improve the qualitative and quantitative traits of basil plants.

EFFECT OF HUMIC ACID and POTASSIUM FERTILIZER IN THE SALT RESISTANCE OF PEPPER CPSICUM ANNUUM L

A field study was carried out during the spring season of 2018 in the fields of the Faculty of Agriculture- University of Anbar to evaluate the effects study of the interaction between humic acid and potash fertilizer in raising the resistance of peppers to salinity. The factorial experiment with three replicates was carried out with three factors. The first factor of irrigation water salinity at four levels was (2, 4, 6 and 8) ds m-1. and the second factor was the humic acid levels (0, 25 and 50) kg ha-1 and the third factor is the Potassium fertilizer at the levels of 0, 75 and 150 kg k2o ha1. And carried out by following the design of the complete random sectors and three replicates were transferred seedlings to the field according to the experimental factors after development in the dishes of cork and after germination were watering fresh water for 20 days. After five leaves, all seedlings were irrigated with saline water. 2 ds m-1 for 15 days after it was irrigated with saline water 2, 4, 6 and 8 ds m-1. for 15 days and then transferred to the field according to the experimental parameters. The most significant results obtained from the experiment can be summed up above the treatment of air conditioning at saline level 6 ds m-1 in plant height with 80.63 cm and The most significant results obtained from the experiment can be summed up above the treatment of air conditioning at saline level 2 ds m-1 in yield per plant 7.10 kg.plant-1. The results showed an decrease in plant height and yield per plant by increasing the salinity of irrigation water by 8 ds m-1 for dry weight and the increase in the addition of humic acid and potassium fertilizer. The results showed an increase in nitrogen concentration and potassium and decrease of phosphorus by increasing the salinity and increase of irrigation water and increase (N. P. K) when adding HA and K.

Concentration dependent effect of humic acid on the transformations of silver nanoparticles

Influence of humic acid (HA) concentration on the colloidal stability and dissolution of silver nanoparticles (AgNPs) was evaluated in a series of long-term experiments. The stability of freshly synthesized and uncoated AgNPs was investigated as a function of HA concentration (0–250 mg/L). In the absence of HA, AgNPs underwent oxidative dissolution and aggregation disturbing the colloidal stability of AgNPs. In the HA concentration range of 1–20 mg/L, HA stabilized AgNPs due to the inhibition of the release of ionic Ag ensuring the persistence of AgNPs in the aquatic environment for a longer period. At higher concentrations of HA (20–250 mg/L) in the soil environment, AgNPs were wrapped by the HA molecules, increasing the hydrodynamic diameter of the AgNPs. Due to the suppression of dissolution of AgNPs, primary particles remained stable in the environment for a prolonged period with no change in the primary particle size and morphology. Furthermore, it was observed that ionic Ag in the solution can be reduced to form fresh, secondary AgNPs at the lower levels of HA in the aquatic environment, in the presence of sunlight. This study is important in understanding the role of HA on the stability of AgNPs in the natural environment.