The present study reports the use of Citrus limetta (CL) residue for cultivating Chlorella sp. mixotrophically to augment production of biodiesel. The cultivation of Chlorella sp. using CL as media was carried out by employing a fed-batch technique in open tray (open tray+CL) and in software (BioXpert V2)–attached automated photobioreactor (PBR+CL) systems. Data showed the limit of nitrogen substituent and satisfactory organic source of carbon (OSC) in CL, causing > 2-fold higher lipid content in cells, cultivated in both the systems than in control. For the cells grown in both the systems, ≥ 3-fold enhancement in lipid productivity was observed than in control. The total fatty acid methyl ester (FAME) concentrations from lipids extracted from cells grew in PBR+CL and in open tray+CL techniques were calculated as 50.59% and 38.31%, respectively. The PBR+CL system showed improved outcomes for lipid content, lipid and biomass productivity, FAME characteristics and physical property parameters of biodiesel than those obtained from the open tray+CL system. The physical property parameters of biodiesel produced from algal cells grown in PBR+CL were comparable to existing fuel standards. The results have shown lower cold filter plugging point (− 6.57 °C), higher cetane number (58.04) and average oxidative stability (3.60 h). Collectively, this investigation unveils the novel deployment of CL as a cost-effective feedstock for commercialisation of biodiesel production.

N-nitrosodimethylamine (NDMA), a toxic disinfection byproduct commonly associated with chloramination, has recently been found to form from an anti-yellowing agent (4,4′-hexamethylenebis (1,1-dimethylsemicarbazide) (HDMS)) during ozonation but the mechanisms are unclear. In this paper, the potential roles of molecular ozone (O₃) and hydroxyl radical (∙OH) on NDMA formation from HDMS were investigated under various oxidation conditions (ozone dosages, pH) and different components in water (bromide ion (Br⁻), bicarbonate ion (HCO₃⁻), sulfate ion (SO₄²⁻), and humic acid (HA), as well as natural organic matter (NOM) from a lake). Moreover, HDMS transformation pathways by ozonation were determined. The results indicated that the formation of NDMA was enhanced through the combined effect of O₃ and ∙OH compared to that by O₃ alone (addition of tert-butyl alcohol (tBA) as ∙OH scavenger). ∙OH itself cannot generate NDMA directly; however, it can transform HDMS to intermediates with higher NDMA yield than parent compound. The NDMA generation was affected (small dosages promoted but high dosages inhibited) by HA or Br⁻ no matter with or without tBA. The presence of SO₄²⁻ and HCO₃⁻ ions lowered NDMA formation through ∙OH scavenging effect. Increasing pH not only increased degradation rate constant by enhancing ∙OH generation but also affected HDMS dissociation ratio, reaching the maximum NDMA formation at pH 7–8. Natural constituents in selected water matrix inhibited NDMA formation. Impacts of these influencing factors on NDMA formation by only O₃ however were significantly less pronounced over that by the joint roles of O₃ and ∙OH. Based on the result of Q-TOF, LC/MS/MS, and GC/MS, the possible transformation pathways of HDMS by ozonation were proposed. The NDMA enhancement mechanism by the combined effect of O₃ and ∙OH can be attributed to greater amounts of intermediates with higher NDMA yield (such as unsymmetrical dimethylhydrazine (UDMH)) produced. These findings provide new understanding of NDMA formation upon ozonation of typical amine-based compounds.

Transport sector contributed numerous carbon emissions in China. It is important to promote low-carbon bicycle-sharing using in China. This paper aims to analyze the influencing factors of the satisfaction and engagement of bicycle-sharing in China. An extended model of customer satisfaction is established, which considers both customer satisfaction theory and customer engagement theory. We explore the different effect of convenience, health, safety, and facility on satisfaction of bicycle-sharing using. We also explore the role of satisfaction on three different dimensions of engagement: enthusiasm, participation, and social interaction. Multi-group structure equation model is employed to explore the different roles of gender on the determinants of satisfaction and engagement of bicycle-sharing using. The findings reveal that facilities had the larger effect on satisfaction of bicycle-sharing using than safety and health for male. Safety had the largest influence on satisfaction of bicycle-sharing using for female, followed by facility, convenience, and health.

Our study evaluated 163 individuals, being 74 soybean farmers, occupationally exposed to pesticides, and 89 individuals from Goias municipalities, Central Brazil, with similar conditions to the exposed group, comprising the control group. Of the 74 soybean farmers, 43 exposed directly to pesticides and 31 exposed indirectly. The exposed group consisted of individuals aged 19 to 63 years, 21 women and 53 men, and the control group had ages ranging from 18 to 64 years, being 36 women and 53 men. 18.9% of the exposed group were poisoned by pesticides, and the most common symptoms were headache and gastrointestinal problems. The genotype frequencies of the rs2031920 (T>C) polymorphism in the CYP2E1 gene present significant differences between the exposed and control groups (p = 0.02), showing that 24.3% of the exposed group were heterozygotes against 6.7% in the control group. For the OGG1 gene, two SNPs, rs1052133 (G>C) and rs293795 (T>C), were evaluated and the genotype frequencies were not statistically different between the exposed and control groups. The DNA damage was distinct (p < 0.05) in the three analyzed comet parameters (tail length, Olive tail moment, %DNA) between groups. However, there was no influence of age and alcohol consumption between the groups associated with the polymorphisms in the CYP2E1 and OGG1 genes and DNA damage. We also did not find altered hematological and biochemical parameters in the exposed group. Thus, this pioneering study at Goias State carried out an overview of the health of soybean farmers. We evaluated classic laboratory exams, associated with exposure markers (comet assay) and susceptibility markers (genetic polymorphisms), emphasizing the need to expand the Brazilian health assessment protocol. We found, in soybean farmers, increased DNA damage and a higher number of heterozygotes in CYP2E1 gene, compared with the control group, despite the lack of association with age, educational level, smoking, drinking habits, and genetic polymorphisms.

Mobile sources are considered to be one of the most important sources of air pollution among which are motor vehicles, recognized as the major contributor of air pollutants in urban areas. To determine the emissions for CO, SO₂, and NO₂ from motor vehicles as part of the attempt to realize the extent of traffic air pollution, measurements were carried out in two heavily traversed traffic tunnels in Tehran metropolitan area. The concentrations of pollutants and metrological and traffic data were collected through intensive measurements from September 27 to October 17, 2016. Resalat Tunnel fleet was composed of about 10% diesel-fueled vehicles and 90% non-diesel-fueled vehicles while throughout the entire duration of our campaign, only non-diesel-fueled vehicles traversed Niayesh Tunnel. Under an average traffic speed of 43 km h⁻¹, emission factors from Resalat Tunnel campaign were measured to be (6.59 ± 2.69)E+3, (1.42 ± 0.84)E+2, and 6.80 ± 4.99 mg km⁻¹ for CO, SO₂, and NO₂, respectively. These values were respectively 11% higher, 22% lower, and 40% higher than those from Niayesh Tunnel measurements which were recorded at a traffic speed of 30 km h⁻¹. Current results indicate that the vehicular emissions in certain countries, especially the developing ones and in this case, Iran, are quite different from those measured in developed countries and that the high emission levels of SO₂ in Iran are associated with the high sulfur content of the gasoline.

The quantification of heavy metal contents in soils and their sources are essential for contamination monitoring and the assessment of the potential risks to the ecosystems. This study aims to investigate the source of heavy metals and other elements in soils from a uranium-phosphate deposit using integrated multivariate and geostatistics techniques. For this, 50 soil samples in Itataia deposit, Northeastern, Brazil, were collected at 0–0.2-m depth for the determination of U, Fe, Al, Mn, Ti, Zn, Cu, Ni, Mo, Co, Cr, Cd, Pb, As, Se, V, B, and Zr. The Pb, Se, Ni, Cr, As, and Mo mean contents were closer or exceeded The Brazilian Environmental Council (CONAMA) prevention values for soils. Uranium content was about 500 times higher than the mean levels reported for Brazilian soils. The cluster analysis indicates three geochemical groups based on different contamination levels. The first principal component was associated with lithological origin, the second principal component may be related to anthropogenic sources, and the third and fourth principal components indicated a joined source (natural and anthropogenic), indicating different sources of contamination. Mo was not related to other heavy metals, being found independent in the area. The accumulation of heavy metals in soils is associated not only with the parent material but also with the minerals of the soil. In the area of study, calcareous soils favored alkaline conditions that influenced the dynamics of heavy metals. The multivariate and geostatistical analyses were able to provide preliminary information regarding the metal contents in soil for environmental management.

Polycyclic aromatic hydrocarbons (PAHs) are toxic organic pollutants and omnipresent in the aquatic and terrestrial ecosystems. A high-efficient pyrene-degrading strain CP13 was isolated from activated sludge and identified as Mycobacterium gilvum based on the analysis of 16S rRNA gene sequence. More than 95% of pyrene (50 mg L⁻¹) was removed by CP13 within 7 days under the alkaline condition. Pyrene metabolites, including 4-phenanthrenecarboxylic acid, 4-phenanthrenol, 1-naphthol, and phthalic acid, were detected and characterized by GC-MS. Results suggested that pyrene was initially attacked at positions C-4 and C-5, then followed by ortho cleavage, and further degraded following the phthalate metabolic pathway. Analysis of pyrene-induced proteins showed that the extradiol dioxygenase, a key enzyme involved in pyrene degradation, was highly up-regulated in pH 9 incubation condition, which illustrated the high efficiency of CP13 under alkaline environment. The present study demonstrated that the isolated bacterial strain CP13 is a good candidate for bioremediation of alkaline PAH-contaminated sites.

Inferring causality has long been a challenging task in environmental impact studies and monitoring programs, mostly because of the problem of confounding bias, i.e. the difficulty of separating impact from natural variation. Traditional approaches for dealing with confounding, despite improvements in study design and statistical analysis, are inadequate. Using aquatic biota as a case study, this review explains the limitations of traditional methods used to separate the impact of human-made pollution from natural variation in the environment. Advantages and disadvantages of the traditional and novel techniques are enumerated. Bayesian networks (BNs) and structural equation modelling (SEM) as causal modelling techniques are introduced as approaches to improve environmental impact monitoring.

Three representative earthen canals from urban, peri-urban, and rural-urban fringe of Sri Lanka were studied for a 2-year period against different seasons to capture insights important in ecological rehabilitation. Only the canal from rural-urban fringe showed a better water quality in wet season; elucidating, the impact of contaminated catchment runoff in the other canals. At a given sampling session, one or two peaks (relative maxima) were observed in urban and peri-urban canals for pollution representative parameters such as nitrate nitrogen and soluble reactive phosphorus. Those peaks were highly localised, an indication of poor advection. In general, two-dimensional variations of electrical conductivity and turbidity in dry season were uniform in urban and peri-urban canals, an indication of dominant molecular diffusion. This was further evidenced via physical models for different flow stages (low, high, and bankfull). Therefore, fate of contaminants had to be mainly governed by assimilation via sediments. However, grey water footprint analyses showed urban and peri-urban canals have over utilised the natural assimilation capacity of many water quality parameters by several folds. This study proved the importance of inducing attenuation by instream physical heterogeneity similar to natural streams or naturalised canals such as the canal from the rural-urban fringe of this study.