Binding phosphate at participation of alginate/FeCl₃ capsules was studied with laboratory experiments. The hydrogel microcapsules were obtained with the dropping-in method, by gelation of sodium alginate water solution by iron (III) chloride solution. Phosphate adsorption characteristics were studied in a static batch system with respect to changes in contact time, initial phosphates concentration, pH of solution, and temperature. After 24 h of the tests, average 87.5% of phosphate ions were removed from the natural water solutions; after 48 h, an equilibrium was reached. The adsorption data were well fit by the Freundlich isotherm model. Parameter k of the isotherms amounted from 43.4 to 104.7, whereas parameter n amounted from 0.362 to 0.476. The course of processes of phosphate adsorption and iron desorption to aquatic phase, as well as changes in pH, suggests that phosphate adsorption is a major mechanism of phosphate removal, whereas simultaneously, but at a much lower degree, a process of precipitation of phosphate by iron (III) ions released from the capsules to the solution takes its place. Parameters calculated in the Freundlich isotherm equation show that by using several times smaller amounts of iron, it is possible to remove similar or bigger amounts of phosphorus than with other adsorbents containing iron. The alginate/FeCl₃ adsorbent removes phosphate in a wide pH spectrum—from 4 to 10. Results suggest that the proposed adsorbent has potential in remediation of contaminated waters by phosphate.

A shortage in available water resources for rice production makes the evaluation of rice yield and greenhouse gas emission in response to drought caused by water scarcity vital. Here, we examined three forms of irrigation management (normal amount [NA], 70 % of NA [NA 70 %], and 30 % of NA [NA30%]) and two rice varieties (Oryza sativa L. cv. Hanyou 8 and Oryza sativa L. cv. Huayou 14) to determine their effects on CH₄ emission and rice yield in two rice growing seasons. Hanyou 8 is a variety of water-saving and drought-resistance rice (WDR), while Huayou 14 is a common rice variety with no known adaptation to drought conditions. NA 70 % reduced CH₄ emission by 30.3–53.3 %, and NA 30 % further depressed CH₄ emission by 51.0–76.7 % relative to NA in both seasons. However, NA 70 % and NA 30 % significantly decreased rice yield by 6.3 % (P < 0.05) and 10.1 % (P < 0.01), respectively, for Huayou 14 when compared with NA in the relatively dry season. Conversely, no differences in rice yield among different irrigation managements were observed for Hanyou 8 in both seasons, suggesting that Hanyou 8 is more drought-resistant than Huayou 14 in terms of rice yield. The results suggest that, to meet the water scarcity, the use of rice varieties with water-saving and drought-resistant traits may minimize rice yield loss and mitigate CH₄ emission in the rice-cultivated regions of the world.

Drainage filters using porous granular material constitute new innovative technologies for remediating phosphorus (P) from agricultural tile drainage water. In drainage filters where convective velocities are often high, we hypothesize that intragranular diffusion may affect solute transport depending on filter characteristics and flow rate. This was investigated for six drainage filter materials (Leca, Filtralite-P®, granulated limestone, crushed seashells, calcined diatomite earth (CDE), and a poorly ordered Fe oxide aggregate (CFH)) conducting a tritium (³H₂O) tracer experiment at low (0.26 cm h⁻¹), medium (23 cm h⁻¹), and high (41 cm h⁻¹) flux densities. The filter materials differed widely with respect to grain-size distribution (D ₅₀ from 1.6 to 3.3 mm), uniformity coefficient (1.7 to 2.2), particle density (1.75 to 2.76 g cm⁻³), bulk density (0.34 to 1.46 g cm⁻³), and water-filled porosity (0.39 to 0.73 cm³ cm⁻³). Measurements of specific surface area (SSA) included both SSABET and SSAEGME to ensure inclusion of the intragranular microporosity, not accounted by N₂-BET. SSA varied widely across methods and allowed the differentiation of filters according to the significance of the intragranular porosity. Tritium transport varied from approximately equilibrium transport at all flow rates in Leca, Filtralite-P®, and limestone, to progressive non-equilibrium transport as flow rate increased in Seashells, CDE, and CFH. In general, the filter materials were highly variable in hydro-physical properties. Filters with (approximately) equilibrium transport were, however, all characterized by low specific surface areas. The non-equilibrium transport was explained by an intragranular diffusion in filters with larger specific surface area (Seashells, CDE, and CFH).

The removal of As(V) from aqueous solutions by leonardite loaded with ferric ions (Fe-leonardite) has been investigated. The influence of pH, contact time, and arsenate concentration on the adsorption process were evaluated. Batch kinetic studies showed that equilibrium time was reached at 24 h of contact time. Equilibrium data obtained with low initial arsenate concentrations (10–400 ppb) were fitted to both Langmuir and Freundlich models, and the maximum adsorption capacity was estimated to be 322 μg g⁻¹. Arsenic sorption was evaluated in continuous mode to reproduce industrial applications and to determine the conditions where the process was controlled by either mass transfer or reaction rate. A maximum sorption capacity of 905 μg g⁻¹ was obtained in continuous experiments. These results indicate that Fe-leonardite is a great potential material for removing arsenate at low initial concentrations from contaminated water.

Adsorption of six neutral (chlorpyrifos, α-endosulfan, fenthion, parathion, parathion metyl, and cis permethrin) and six basic (pirimicarb, prochloraz, prometryn, pirimiphos ethyl, quinoxyfen, and triadimefon) pesticides was measured in ten natural soils in order to unravel the parameters influencing soil sorption. Linear regression confirmed that organic carbon content of soil is the determinant factor of soil sorption along with a secondary role of clay in the case of basic pesticides. Concerning pesticides themselves, their potential to be absorbed is governed by hydrophobic, electrostatic, and polar interactions. Electrostatic interactions can be expressed by considering the molecular fraction of positively charged species (F⁺). The combination of these parameters led to good prediction models, where the two expressions of lipophilicity, octanol-water partition (logP) and distribution coefficient (logD), showed similar performance. Finally, the role of electrostatic interactions to soil sorption and their successful expression by F⁺ parameter was further confirmed using artificial adjustment of the acidity of one soil at different pH values not covered by the natural acidity of the investigated soils.

The interaction between different volatile organic compounds (VOCs) is a critical issue associated with bioremediation of co-contaminated sites. Contradictory results have been reported on the effects of co-existence of VOCs on biodegradation of each VOC. These contradictions are thought to be caused by inter-study variability in microbial diversity. To examine the effects of co-existing VOCs on biodegradation of each VOC, a series of biodegradation tests were carried out with a microcosm capable of degrading all three VOCs: dichloromethane (DCM), benzene, and toluene. We added different combinations of the VOCs to the microcosm while monitoring VOC concentration and microbial community diversity. Degradation of DCM and benzene was minimally influenced by co-existence of other VOCs; however, degradation of toluene was dramatically enhanced by the co-existence of benzene. Propioniferax was identified in cultures exposed to benzene alone and cultures simultaneously exposed to benzene, toluene, and DCM. Propioniferax was dominant, but prior to this study, it was not known to degrade benzene, toluene, and DCM. In the cultures exposed to only toluene, Rhodanobacter, Mycobacterium, Bradyrhizobium, and Intrasporangium increased during the biodegradation. The former three bacteria increased more rapidly when benzene and DCM were also included. These results suggest that co-existence of benzene and DCM can enhance the activity of Rhodanobacter, Mycobacterium, and Bradyrhizobium and consequently accelerate the degradation of toluene.

Titania/silica nanomaterials have many possible applications; however, they can be toxic to living organisms, particularly if the material accumulates in niche environments, e.g. areas colonised by actinomycetes. This study therefore investigated the effect of non-activated and UV light-activated titania/silica nanospheres on an environmental Streptomyces strain. The bacteria were incubated with the nanospheres and subsequently cultured on solid medium. The morphology and elemental composition were analysed using optical and electron microscopy (TEM, STEM) and energy-dispersive X-ray spectroscopy (EDX). The appearance of Streptomyces sp. in the experimental and control samples demonstrated that the nanospheres did not have bactericidal properties in the used dose. Furthermore, the observed strain not only survived in the presence of the nanomaterial but also appeared to play a role in its dissolution with an accumulation of the titanium in the intracellular globules of polyphosphate (volutin). Additionally, it was discovered that the UV light-activated titanium dioxide altered the ability of the bacteria to secrete humic acid. The reported phenomenon might be made possible through an accumulation of titanium in the volutin compounds. These findings suggest that streptomycetes could be employed to participate in the dissolution of nanomaterials which enter the natural environment.

Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3 N fertilizer rates) were used. The CRM treatments were (1) R0: 100 % of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83 % of the N using mineral and 17 % manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450 kg N ha⁻¹ year⁻¹. At the end of the experiment, soil NO₃-N was reduced by 33 % from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44 % increase in occluded particulate organic C and N, and 80 °C extracted dissolved organic N, 19 to 32 % increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17 % of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.

The automobile exhausts are one of the major sources of particulate matter in urban areas and these particles are known to influence the atmospheric chemistry in a variety of ways. Because of this, the oxidation of dissolved sulfur dioxide by oxygen was studied in aqueous suspensions of particulates, obtained by scraping the particles deposited inside a diesel truck exhaust pipe (DEP). A variation in pH showed the rate to increase with increase in pH from 5.22 to about ∼6.3 and to decrease thereafter becoming very slow at pH = 8.2. In acetate-buffered medium, the reaction rate was higher than the rate in unbuffered medium at the same pH. Further, the rate was found to be higher in suspension than in the leachate under otherwise identical conditions. And, the reaction rate in the blank reaction was the slowest. This appears to be due to catalysis by leached metal ions in leachate and due to catalysis by leached metal ions and particulate surface both in suspensions. The kinetics of dissolved SO₂ oxidation in acetate-buffered medium as well as in unbuffered medium at pH = 5.22 were defined by rate law: k ₒbₛ = k ₀ + k cₐₜ [DEP], where k ₒbₛ and k ₀ are observed rate constants in the presence and the absence of DEP and k cₐₜ is the rate constant for DEP-catalyzed pathway. At pH = 8.2, the reaction rate was strongly inhibited by DEP in buffered and unbuffered media. Results suggest that the DEP would have an inhibiting effect in those areas where rainwater pH is 7 or more. These results at high pH are of particular significance to the Indian subcontinent, because of high rainwater pH. Conversely, it indicates the DEP to retard the oxidation of dissolved SO₂ and control rainwater acidification.

China is experiencing serious acid rain contamination, with Beijing among the worst-hit areas. To understand the chemical feature and the origin of inorganic ions in precipitation of Beijing, 128 precipitation samples were collected and analyzed for major water-soluble ions and δ³⁴S. The pH values ranged from 3.68 to 7.81 and showed a volume weighted average value (VWA) of 5.02, with a frequency of acid rain of 26.8 %. The VWA value of electrical conductivity (EC) was 68.6 μS/cm, which was nearly 4 times higher than the background value of northern China. Ca²⁺ represented the main cation; SO₄²⁻ and NO₃⁻ were the dominant anion in precipitation. Our study showed that SO₄²⁻ and NO₃⁻ originated from coal and fossil fuel combustion; Ca²⁺, Mg²⁺, and K⁺ were from the continental sources. The δ³⁴S value of SO₄²⁻ in precipitation ranged from +2.1 to +12.8‰ with an average value of +4.7‰. The δ³⁴S value showed a winter maximum and a summer minimum tendency, which was mainly associated with temperature-dependent isotope equilibrium fractionation as well as combustion of coal with relatively positive δ³⁴S values in winter. Moreover, the δ³⁴S values revealed that atmospheric sulfur in Beijing are mainly correlated to coal burning and traffic emission; coal combustion constituted a significant fraction of the SO₄²⁻ in winter precipitation.