Greenhouse gas emissions from paddy soils respond differently to different combinations of crop root residues and N forms. An incubation experiment was carried out to explore the effect of four crop residues (milk vetch, ryegrass, winter wheat, and rape) and four nitrogen treatments (without fertilizer, urea, (NH₄)₂SO₄, and KNO₃) on CH₄, CO₂, and N₂O emissions in a paddy soil. Except in KNO₃ application treatments, CH₄ emissions of milk vetch residue treatments were significantly higher than those of the rest residue treatments. In the presence of milk vetch and ryegrass residues, urea application significantly increased CH₄ emissions in comparison to treatments without fertilizer. Urea significantly promoted CO₂ emissions, whereas (NH₄)₂SO₄ and KNO₃ significantly inhibited CO₂ emissions at all root residue treatments. Urea did not increase N₂O emissions, but (NH₄)₂SO₄ and KNO₃ promoted N₂O emissions at all residue treatments. In addition, KNO₃ had more effects on the increase of N₂O emissions than (NH₄)₂SO₄ in milk vetch-amended soils. Urea addition had no effect on global warming potentials, and (NH₄)₂SO₄ and KNO₃ addition significantly increased global warming potentials at all residue treatments except KNO₃ + winter wheat residue combination. Our results indicated that urea application had no additive effect on global warming when root residues were left in paddy soils, whereas (NH₄)₂SO₄ and KNO₃ application could increase the risk of global warming.

Growing rice with less water is direly needed due to declining water sources worldwide, but using methods that require less water inputs can have an impact on grain characteristics and recovery. A 2-year field study was conducted to evaluate the impact of conventionally sown flooded rice and low-water-input rice systems on the grain characteristics and recovery of fine rice. Three fine grain rice cultivars—Super Basmati, Basmati 2000, and Shaheen Basmati—were grown under conventional flooded transplanted rice (CFTR), alternate wetting and drying (AWD), and aerobic rice systems. Grain characteristics and rice recovery were significantly influenced by different water regimes (production systems). Poor milling, including the lowest percentage of brown (head) rice (65.3%) and polished (white) rice (64.2–66.9%) and the highest percentage of broken brown rice (10.2%), husk (24.5%–26.3%), polished broken rice (24.7%), and bran (11.0–12.5%), were recorded in the aerobic rice system sown with Shaheen Basmati. With a few exceptions, cultivars sown in CFTR were found to possess a higher percentage of brown (head) and polished (white) rice and they had incurred the least losses in the form of brown broken rice, husk, polished broken rice, and bran. In conclusion, better grain quality and recovery of rice can be attained by growing Super Basmati under the CFTR system. Growing Shaheen Basmati under low-water-input systems, the aerobic rice system in particular, resulted in poor grain characteristics tied with less rice recovery.

The aim of the study was to determine the changes in suspension particle size identified in biologically treated wastewater, which was then treated in hydroponic system with use of engineering lighting by the light-emitting diodes (LED). The study was subjected to wastewater purified under laboratory conditions, in a hydroponic system using the effect of macrophytes Pistia stratiotes and growing algae. Measurement of particle size was made using a laser granulometer. Analysis of the results showed that the additional lighting of the hydroponic system with LED can significantly influence the ability of the suspension particles to agglomerate and, consequently, determine their sedimentation properties. In hydroponic system supported by additional lighting, more particles were observed with equivalent diameter D(3.2) smaller than 10 μm than those in the tank without additional lighting, indicating a higher reactivity of the particles. Determining the size of equivalent diameters D(4.3) allowed us to observe that in hydroponic system, particles of relatively small size predominate, which negatively affects the sedimentation process of the suspensions. Determination of particle size of suspensions consisting mainly of algae and the dynamics of their changes are the basis for specification of an effective method of removing particles from the system to protect the receiver from excessive suspension concentrations.

The aim of this study was to determine if benthic diatoms can be used as effective and reliable indicators of ionic composition and conductivity in different stream order categories. Samples were collected on two occasions from 22 sampling sites within the Bloukrans River system, Eastern Cape Province, South Africa. The data collected were subjected to multivariate statistical technique, i.e. CCA, to determine environmental gradients along which the diatom species were distributed as well as to elucidate hypothesised differences in community structure per stream order. Significant differences between the two sampling periods were observed in dissolved oxygen, temperature, Na, B, Ca, Zn, Cu, Cr, K, Fe, phosphate, conductivity, salinity and nitrate, while significant stream order variation was observed for conductivity, salinity, Mg, Ca and sediment nitrates. Study sites were grouped into two broad categories (stream order 1 and 2/3 sites) based on CCA. As pollution increased, low to moderate pollution-tolerant species such as Fragilaria tenera, Cyclostephanos dubius and Gyrosigma acuminatum were replaced by high pollution-tolerant species such as Nitzschia palea, Gomphonema parvulum, Tryblionella apiculata, Diploneis vulgaris and Staurosira elliptica. This shows that diatom assemblages are appropriate indicators of ionic composition/conductivity and hydromorphological characteristics (e.g. stream size) of running waters. The results highlight the importance of creating regional calibration datasets which will make it possible to develop procedures to determine conductivity and ion concentration effects on biota.

With the organic carbon of acetate (SBR-A) and propionate (SBR-P), the effect of organic carbon sources on nitrogen removal and nitrous oxide (N₂O) emission in the multiple anoxic and aerobic process was investigated. The nitrogen removal percentages in SBR-A and SBR-P reactor were both 72%, and the phosphate removal percentages were 97 and 85.4%, respectively. During nitrification, both the NH₄⁺-N oxidation rate in the SBR-A and SBR-P had a small change without the influence of the addition of nitrite nitrogen (NO₂⁻-N). With the addition of 10 mg/L NO₂⁻-N, the nitrate nitrogen (NO₃⁻-N) production rate, N₂O accumulation rate and emission factor had increased. At the same time, the N₂O emission factor of SBR-A and SBR-P reactors increased from 2.13 and 0.87% to 4.66 and 2.08%, respectively. During exogenous denitrification, when nitrite was used as electron acceptor, the N₂O emission factors were 34.1 and 8.6 times more than those of NO₃⁻-N as electron acceptor in SBR-A and SBR-P. During endogenous denitrification with NO₂⁻-N as electron acceptor, the accumulation rate and emission factor of N₂O were higher than those of NO₃⁻-N as electron acceptor. High-throughput sequencing test showed that the dominant bacteria were Proteobacteria and Bacteroidetes in both reactors at the phylum level, while the main denitrification functional bacteria were Thauera sp., Zoogloea sp. and Dechloromonas sp. at the genus level.

In this study, activated red mud was used to develop an effective adsorbent in order to remove a toxic azo dye (tartrazine E102) from aqueous solutions. To increase the adsorption capacity, the red mud was activated by acid-heat treatment using 20 wt.% HCl (RM-HCl). To establish the optimum operating parameters, the influence of pH, adsorbent dose, contact time, initial dye concentration, and stirring rate was investigated. The adsorption equilibrium was studied using Langmuir, Freundlich, Dubinin-Radushkevich, Temkin isotherm models, and the characteristic parameters for each adsorption isotherm were determined. The kinetics of the adsorption process was analyzed by means of pseudo-first-order and pseudo-second-order models. The maximum removal efficiency obtained under optimum conditions was 84.72%. These results were in accordance with the isotherm and kinetic data. The results suggested that tartrazine adsorption process follows the pseudo-second-order kinetic model and also that fits Langmuir isotherm model. The maximum monolayer adsorption capacity was 136.98 mg/g.

This paper explores the proposition that we are living in an era marked by unprecedented quantities and exotic types of human waste and environmental contamination by examining the impact of anthropogenic activity on the Earth’s epiderm. Specifically, the paper introduces anthrosols and technosols as critical markers of unfettered human activity as recorded in the terrestrial stratigraphic signature of soils and sediments adversely impacted by municipal, agricultural, industrial and maritime activities. The paper presents examples of the sources and fates of some of the most worrisome contaminants, many of them persistent organic pollutants, including common heavy metals-metalloids and hydrocarbons but also instances of more unfamiliar drug residues and antibiotic resistant genes, at Australia’s 160,000 contaminated sites.Consideration is given to how anthropogenic elements and compounds in soil may bioaccumulate and bioconcentrate in animals, and how they can subsequently be consumed to the detriment of human health. Among the 75,000 identified contaminants in Australian soils are tributyltin, which has a half-life of at least 10 years and is one of the most toxic chemicals introduced into the environment by man, and uranium-contaminated mine tailings, which require constant and careful management for up to 75,000 years if their polluting effects are to be minimized. The author concludes that anthrosols and technosols provide evidence of the Anthropocene in Australia.

The photocatalytic degradation of a cationic dye, rhodamine 6G (Rh-6G) under UV light irradiation was carried out. Rh-6G was completely decolorized in 180 min of photo-oxidative degradation period. The extent of degradation was confirmed performing total organic carbon (TOC) analysis, and up to 90.14%, TOC removal was achieved. Several critical analytical techniques including UV-Vis spectroscopy, high-performance liquid chromatography (HPLC), and ultra-performance liquid chromatography coupled with electrospray ionization mass spectrometry (UPLC/MS) were employed to scrutinize the mechanistic insights of the dye photodegradation. The degraded N-demethylation intermediates and several small molecular products were qualitatively identified, and a tentative photodegradation pathway was proposed. Toxicological evaluation of the degradation products was carried out three types of cell lines (MTT assay) and Triticum sativum seeds. In conclusion, enhanced biodegradability accompanied by toxicity reduction confirmed the promising efficiency of photocatalysis for Rh-6G degradation and therefore could be used for the remediation of textile effluents.

Air pollution represents a significant fraction of the total mortality estimated by the World Health Organization (WHO) global burden of disease project (GBD). The present paper discusses the characteristics of trace gases (O₃, NO, NO₂, and CO) and particulate matter (PM₁₀ and PM₂.₅) in two Asian megacities, Delhi (India) and Beijing (China). A continuous measurement of trace gases and particulate matter are considered from 12 measuring sites in Beijing and 8 sites in Delhi. Over Beijing, the annual average of PM₂.₅, PM₁₀, O₃, NO₂, and CO is, respectively, 85.3, 112.8, 58.7, and 53.4 μg/m³ and 1.4 mg/m³, and, respectively, over Delhi 146.5, 264.3, 24.7,and 19.8 μg/m³ and 1.73 mg/m³. From the spatial variations of pollutants, the concentrations of particulate matter and trace gases are observed to be much higher in the urban areas compared to the suburban areas. The higher average concentrations of PM₁₀ and PM₂.₅ over Delhi and Beijing are observed during winter season compared with other seasons. The maximum diurnal variation of PM₁₀ concentration is observed during winter season over Beijing and Delhi. The comparison of trace gases shows that the O₃ concentrations during daytime are obviously higher compared with nighttime, and the highest diurnal variation of O₃ is observed during summer. The concentrations of CO are highest during winter season, and higher concentrations are observed during nighttime compared to daytime. The O₃ and CO show negative correlation over Beijing and Delhi. The negative correlation between O₃ and NO₂ is merely observed over Beijing, while CO and NO₂ concentrations, in contrast, show positive correlation over Beijing.

The sorption of three organic contaminants with different structure and polarity including non-polar phenanthrene (PHEN), 1,2,4,5-tetrachlorobenzene (TeCB), and polar 1,2-dichlorobenzene (DCB) onto original kaolinite, smectite, vermiculite, and fulvic acid (FA)/humic acid (HA)–clay complexes were investigated, and possible sorption mechanisms were inferred from sorption isotherms and characteristics of humic substances (HS) and HS–mineral complexes. Results showed smectite and vermiculite had stronger sorption ability than kaolinite, and the adsorbed amount of DCB was much higher than that of PHEN and TeCB on each clay. Due to FA/HA-facilitated hydrophobic interaction, FA/HA–clay complexes except FA–vermiculite complex showed a stronger affinity for PHEN and TeCB than the original clays, particularly for HA–clay complexes. The non-linearity parameter values of n for all the Freundlich sorption isotherms of DCB were greater than 1, indicating that clays possessed some unique sites with strong affinity and capacity to sorb DCB from aqueous solutions. FA/HA did not significantly affect the sorption of polar DCB on clays, implying sorption of DCB on clays was probably due to polar interactions between the polar group of DCB and clays. Cation-π bonding between PHEN and iron cation was directly evidenced by X-ray photoelectron spectroscopy, and FA impeded the sorption of PHEN on vermiculite by occupation of iron cation sites. This study will benefit understanding behaviors of contaminants in the soil environments.