Nanotechnology is a fast-emerging field and has received applications in almost every field of life. Exploration of new synthetic technologies for size and shape control of nanomaterials is getting immense consideration owing to their exceptional properties and applications. Magnetic nanoparticles (MNPs) are among the most important group of nanoparticles thanks to their diverse applications in medical, electronic, environmental, and industrial sectors. There have been numerous synthetic routes of MNPs including thermal decomposition, co-precipitation, microemulsion, microwave assisted, chemical vapor deposition, combustion synthesis, and laser pyrolysis synthesis. The synthesized MNPs have been successfully applied in medical fields for therapy, bioimaging, drug delivery, and so on. Among environmental aspects, there has been great intimidation of organic pollutants in air and water. Utilization of various wastes as adsorbents has removed 80 to 99.9% of pollutants from contaminated water. MNPs as adsorbents compared to coarse-grained counterparts have seven times higher capacity in removing water pollutants and degrading organic contaminants. This study is focused to introduce and compile various routes of MNP synthesis together with their significant role in water purifications and degradation of organic compounds. The review has compiled recent investigation, and we hope it will find the interest of researchers dealing with nanoparticles and environmental research. Graphical abstract Synthesis and applications of magnetic nanoparticles.

To better understand the sources as well as characterization of regional aerosols at a rural semi-arid region Kadapa (India), size-resolved composition of atmospheric particulate matter (PM) mass concentrations was sampled and analysed. This was carried out by using the Anderson low-pressure impactor for a period of 2 years during March 2013–February 2015. Also, the variations of organic carbon (OC), elemental carbon (EC) and water-soluble inorganic ion components (WSICs) present in total suspended particulate matter (TSPM) were studied over the measurement site. From the statistical analysis, the PM mass concentration showed a higher abundance of coarse mode particles than the fine mode during pre-monsoon season. In contrast, fine mode particles in the PM concentration showed dominance over coarse mode particle contribution during the winter. During the post-monsoon season, the percentage contributions of coarse and fine fractions were equal, whereas during the monsoon, coarse mode fraction was approximately 26 % higher than the fine mode. This distinct feature in the case of fine mode particles during the studied period is mainly attributed to large-scale anthropogenic activities and regional prevailing meteorological conditions. Further, the potential sources of PM have been identified qualitatively by using the ratios of certain ions. A high sulphate (SO₄) concentration at the measurement site was observed during the studied period which is caused by the nearby/surrounding mining activity. Carbon fractions (OC and EC) were also analysed from the TSPM, and the results indicated (OC/EC ratio of ~4.2) the formation of a secondary organic aerosol. At last, the cluster backward trajectory analyses were also performed at Kadapa for different seasons to reveal the origin of sources from long-range transport during the study period.

Growing concern has been raised over the potential hazard of nanoparticles (NPs) on human health from ambient particulate air pollution. Silicon dioxide (SiO₂) NPs are one of the most widely used nanoparticles in many sectors of industry. Research on NPs has focused mainly on their toxicity in organs. Meanwhile, NPs are present in the air year-round, but are more serious in winter. Thus, the aim of this study was to evaluate the inflammatory response to SiO₂ NPs using in vivo test systems. The composition of particulate matter is complicated; however, elemental silicon accounts for a significant proportion. Cold exposure can induce many kinds of systemic reactions. Thus, the second aim of this study was also to evaluate the combined effect of NPs and cold exposure on human health. There is little research on the combined effects of nanoparticles and cold on inflammation. Sprague-Dawley rats were randomly divided into four groups: those exposed to SiO₂ NPs by intratracheal instillation, those exposed to at 4 °C 4 h/day for 4 weeks, a combined SiO₂ NPs and cold exposure group, and a control group. Inflammatory cell infiltration in the lungs was mainly observed after exposure to SiO₂ NPs or cold. Hematoxylin and eosin staining revealed that inflammation of the lungs was more serious in the combined group. In the white adipose tissue and brown adipose tissue of the combined groups, the mRNA expressions of pro-inflammatory cytokines were upregulated. In conclusion, SiO₂ NPs combined with cold exposure induced a stronger systemic inflammatory response, accompanied by more serious health hazards.

Diatoms hold great promise as potential sources of biofuel production. In the present study, the biomass and lipid production in the marine diatom Navicula phyllepta, isolated from Cochin estuary, India and identified as a potential biodiesel feedstock, were optimized using Plackett-Burman (PB) statistical experimental design followed by central composite design (CCD) and response surface methodology (RSM). The growth analyses of the isolate in different nitrogen sources, salinities and five different enriched sea water media showed the best growth in the cheapest medium with minimum components using urea as nitrogen source at salinity between 25 and 40 g kg⁻¹. Plackett-Burman experimental analyses for screening urea, sodium metasilicate, sodium dihydrogen phosphate, ferric chloride, salinity, temperature, pH and agitation influencing lipid and biomass production showed that silicate and temperature had a positive coefficient on biomass production, and temperature had a significant positive coefficient, while urea and phosphate showed a negative coefficient on lipid content. A 2⁴ factorial central composite design (FCCD) was used to optimize the concentration of the factors selected. The optimized media resulted in 1.62-fold increase (64%) in biomass (1.2 ± 0.08 g L⁻¹) and 1.2-fold increase (22%) in estimated total lipid production (0.11 ± 0.003 g L⁻¹) compared to original media within 12 days of culturing. A significantly higher biomass and lipid production in the optimized medium demands further development of a two-stage strategy of biomass production followed by induction of high lipid production under nutrient limitation or varying culture conditions for large-scale production of biodiesel from the marine diatom.

A water-compatible magnetic triclosan (TCS) imprinted material (TCS-CTS-Fe⁰-MIPs) was synthesized for selective enrichment and detection of TCS in real complex water samples. The material was synthesized by using chitosan (CTS) as functional monomer, which has rich surface O- and N-containing functional groups. The TCS imprinted CTS was coated on Fe⁰ surface and then cross-linked with glutaraldehyde. Scanning electron microscopy suggested that the imprinted material was covered with a layer of imprinted film, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirmed that the imprinted material had more functional groups (amino and hydroxyl groups) than that of non-imprinted material. The TCS imprinted and non-imprinted materials used in each adsorption experiments were 0.1 mg mL⁻¹. The maximum adsorption capacity of the TCS imprinted material and non-TCS imprinted material were 20.86 and 15.11 mg g⁻¹, respectively. The adsorption results showed that selectivity coefficient was 10.151, 1.353, and 8.271 in the presence of p-chlorophenol, 2,4,6-trichlorophenol, and bisphenol-A, respectively. The recoveries of river water and lake water samples were 92.8, 91.3, 92.4, and 81.4, 82.3, 82.1%, respectively, when the samples were spiked with 4, 6, and 8 μg L⁻¹ of TCS with the imprinted material. The adsorption capacity of the TCS imprinted material and non-TCS imprinted material lost 5.2 and 6.2% after six times of recycling. The high selectivity and excellent adsorption capacity of the imprinted material can be attributed to the presence of sterically complementary imprinted sites and high surface, which would also made it more accessible to TCS than that of non-imprinted material. The present study would provide an environmental friendly and convenient method for the removal and the monitoring of TCS in environmental water samples.

Salinity is a worldwide environmental problem of agricultural lands. Smoke and plant growth-promoting bacteria (PGPR) are individually used to improve plant growth, but the combined effects of these have not been studied yet under saline conditions. The combined effect of plant growth-promoting bacteria Bacillus safensis and plant-derived smoke Cymbopogon jwarancusa was studied under different salinity level as 50, 100, and 150 mM on rice (cv. Basmati-385). Smoke dilutions of C. jwarancusa (C-500 and C-1000) and bacterial culture of B. safensis were used to soak seeds for 10 h. It was observed that the salt concentration decreases the germination percentage, vegetative growth, ion contents (K⁺ and Ca²⁺), and photosynthetic pigments (Chl “a,” Chl “b,” and carotene) while an increase occurred in Na⁺, total soluble protein (TSP), proline, total soluble sugar, catalase (CAT), and peroxidase (POD) contents. The combined effect of B. safensis and smoke primed seeds increased the germination percentage, seedling growth, ion contents (K⁺, Ca²⁺), and photosynthetic pigments (Chl “a,” Chl “b,” carotene) and reduced the Na⁺ ion content, total soluble protein, proline content, total soluble sugar, CAT, and POD activity by lowering the drastic effect of salt stress. It was concluded that combined effect of smoke and PGPR is more effective than individual effect.

The rapid increase in agricultural pollution demands judicious use of inputs and outputs for sustainable crop production. Crop straws were pyrolyzed under oxygen-limited conditions at 400 °C for 2 h to prepare peanut straw biochar (PB), canola straw biochar (CB), and wheat straw biochar (WB). Then, 300-g soils were incubated each with urea nitrogen (UN) and UN + biochars with or without dicyandiamide (DCD) for 60 days. During the incubations, soil acidification induced by urea was somewhat inhibited by biochars, but nitrification of hydrolyzed NH₄ ⁺ produced much more acidity than the neutralization potential of the biochars. In single UN (200 mg/kg) treatment, soil pH decreased drastically and the final pH after incubation was lower than the control. Antagonistic to UN, all three biochars neutralized the soil acidity, which was consistent to their inherent alkalinity. DCD inhibited nitrification which was obvious throughout the incubations, as 30 mg/kg DCD + 200 mg/kg UN combined with 1 % PB, CB, and WB retained 0.94, 0.79, and 1.19 units higher pH, respectively, and significantly reduced exchangeable acidity over the treatments without DCD (P < 0.05). The treatments of UN + biochars with and without DCD had highly significant effects on soil pH, exchangeable Al³⁺, NH₄ ⁺-N, (NO₃ ⁻+NO₂ ⁻)-N, and available P (P < 0.05). Amplified NH₄ ⁺-N retentions at higher rates of PB referred increased negatively charged sites for nutrient adsorptions. Applied UN transformations varied among different treatments, and the maximum amounts of total mineral N recovered were 218.3, 218.5, and 223.8 mg/kg in the presence of DCD by PB, CB, and WB, compared to 198.2, 201.6, and 205.2 mg/kg, respectively, in no DCD treatments. Urea induced severe soil acidification and even lowered the ameliorative effects of applied biochars. Thus, ammonium-based fertilizers must include nitrification inhibitor (DCD) and, if used in combination with biochars will offer a suitable choice to reduce the acidity, improve base saturation and fertility of soil for sustainable agriculture.