Response surface methodology (RSM) and central composite design (CCD) were used to develop models for optimization and modeling of a gas sparging assisted microfiltration of oil-in-water (o/w) emulsion. The effect of gas flow rate (Q G), oil concentration (C ₒᵢₗ), transmembrane pressure (TMP), and liquid flow rate (Q L) on the permeate flux and oil rejection were studied by RSM. Two sets of experiments were designed to investigate the effects of different gas–liquid two-phase flow regimes; low and high gas flow rates. Two separate RSM models were developed for each experimental set. The oil concentration and TMP were found to be the most significant factors influencing both permeate flux and rejection. Also, the interaction between these parameters was the most significant one. At low Q G , the more the gas flow rate, the higher the permeate flux; however, in the high gas flow rate region, higher Q G did not necessarily improve the permeate flux. In the case of rejection, gas and liquid flow rates were found to be insignificant. The optimum process conditions were found to be the following: Q G = 1.0 (L/min), C ₒᵢₗ = 1,290 (mg/L), TMP = 1.58 (bar), and Q L = 3.0 (L/min). Under these optimal conditions, maximum permeate flux and rejection (%) were 115.9 (L/m²h) and 81.1 %, respectively.

Optical and micro-physical features of aerosol are reported using Skyradiometer (POM-01L, Prede, Japan) observations taken from a high-altitude station Merak, located in north-eastern Ladakh of the western trans-Himalayas region during January 2011 to December 2013. The observed daily mean aerosol optical depth (AOD, at 500 nm) at the site varied from 0.01 to 0.14. However, 75 % of the observed AOD lies below 0.05 during the study period. Seasonal peaks of AOD occurred in spring as 0.06 and minimum in winter as 0.03 which represents the aged background aerosols at the site. Yearly mean AOD at 500 nm is found to be around 0.04 and inter-annual variations of AOD is very small (nearly ±0.01). Angstrom exponent (a) varied seasonally from 0.73 in spring to 1.5 in autumn. About 30 % of the observed a lies below 0.8 which are the indicative for the presence of coarse-mode aerosols at the site. The station exhibits absorbing aerosol features which prominently occurred during spring and that may be attributed by the transported anthropogenic aerosol from Indo-Gangatic Plain (IGP). Results were well substantiated with the air mass back-trajectory analysis. Furthermore, seasonal mean of single scattering albedo (SSA at 500 nm) varied from of 0.94 to 0.98 and a general increasing trend is noticed from 400 to 870 nm wavelengths. These features are apparently regional characteristics of the site. Aerosol asymmetry factor (AS) decreases gradually from 400 to 870 nm and varied from 0.66 to 0.69 at 500 nm across the seasons. Dominance of desert-dust aerosols, associated by coarse mode, is indicated by tri-modal features of aerosol volume size distribution over the station during the entire seasons.

Toxicity evaluation is an important segment in sediment quality monitoring in order to protect aquatic organisms and human health. The purpose of this study is to assess the toxicity of sediments from three sediment cores in Yangtze River Estuary, China, using the zebrafish (Danio rerio) embryo tests. Fertilized zebrafish eggs were exposed to both whole sediments and sediment organic extracts prepared from collected sediments, in order to provide a comprehensive and realistic insight into the bioavailable toxicity potential of the sediments. As end points, development parameters (mortality, hatching rate, and abnormality) in the developing embryos were recorded during the 96-h exposure. The results showed that some samples increased mortality, inhibited the hatching of embryos, and induced morphological abnormalities. The embryonic toxicities presented serrated changes and irregular distribution with depth, which may be related to hydrodynamic effect and unstable environmental input. However, lethal and sub-lethal effects were more significant at the sub-surface sediments (10∼40 cm), which indicated that the pollution is more serious in recent decades.

In recent years, the fine particulate matter pollution has become increasingly serious in Beijing, the capital of China. Being considered as an environment-friendly district of Beijing, current research concerning air pollution in Miyun area was relatively less. From August 24, 2013 to September 29, 2013, 24-h samples were collected in the urban and rural areas of Miyun, Beijing, so as to better understand the sources contributing to PM2.5 and the risk to human health in this district. The data obtained showed that daily PM2.5 mass concentrations ranged from 35.33 to 318.71 μg m⁻³ in the urban sampling site, which however were between 12.62 and 292.33 μg m⁻³ in the rural sampling site. At least 23.5 and 41.2 % of the monitoring data, respectively, exceeded the limit value. The mass concentrations of a number of PM2.5 elements fluctuated significantly in the decreasing order of Zn, Ba, Sr, Cu, Pb, Cr, V, Ni, Sb, and Cd. The daily contribution of three cations (NH₄ ⁺, K⁺, and Na⁺) and four anions (F⁻, Cl⁻, NO₃ ⁻, and SO₄ ²⁻) to PM2.5 mass simultaneously varied from 27.51 to 44.04 % and from 29.54 to 46.14 %. In addition, significant linear correlations between main constituents of the ions (SO₄ ²⁻, NO₃ ⁻, and NH₄ ⁺) at both sites indicated that the majority of NH₄ ⁺ was probably in the form of ammonium sulfate and ammonium nitrate. The risk levels of carcinogenic heavy metals detected in survey region occurred in the order of Cr, Cd, and Ni, of which, Cr may have a potential risk to the environment. High risk levels of both carcinogenic and non-carcinogenic heavy metals were easy to occur on haze–fog days.

The European Water Framework Directive aims to achieve a good ecological and chemical status in surface waters until 2015. Sediment toxicology plays a major role in this intention as sediments can act as a secondary source of pollution. In order to fulfill this legal obligation, there is an urgent need to develop whole-sediment exposure protocols, since sediment contact assays represent the most realistic scenario to simulate in situ exposure conditions. Therefore, in the present study, a vertebrate sediment contact assay to determine aryl hydrocarbon receptor (AhR)-mediated activity of particle-bound pollutants was developed. Furthermore, the activity and the expression of the CYP1 family in early life stages of zebrafish after exposure to freeze-dried sediment samples were investigated. In order to validate the developed protocol, effects of β-naphthoflavone and three selected sediment on zebrafish embryos were investigated. Results documented clearly AhR-mediated toxicity after exposure to β-naphthoflavone (β-NF) and to the sediment from the Vering canal. Upregulation of mRNA levels was observed for all investigated sediment samples. The highest levels of all investigated cyp genes (cyp1a, cyp1b1, cyp1c1, and cyp1c2) were recorded after exposure to the sediment sample of the Vering canal. In conclusion, the newly developed sediment contact assay can be recommended for the investigation of dioxin-like activities of single substances and the bioavailable fraction of complex environmental samples. Moreover, the exposure of whole zebrafish embryos to native (freeze-dried) sediment samples represents a highly realistic and ecologically relevant exposure scenario.

Increasing production and applications of nano zinc oxide particles (nano-ZnO) enhances the probability of its exposure in occupational and environmental settings, but toxicity studies are still limited. Taking the free Zn ion (Zn²⁺) as a control, cytotoxicity of a commercially available nano-ZnO was assessed with a 6-h exposure in Escherichia coli (E. coli). The fitted dose-cytotoxicity curve for ZnCl₂ was significantly sharper than that from nano-ZnO. Then, a genome-wide gene expression profile following exposure to nano-ZnO was conducted by use of a live cell reporter assay system with library of 1820 modified green fluorescent protein (GFP)-expressing promoter reporter vectors constructed from E. coli K12 strains, which resulted in 387 significantly altered genes in bacterial (p < 0.001). These altered genes were enriched into ten biological processing and two cell components (p < 0.05) terms through statistical hypergeometric testing, strongly suggesting that exposure to nano-ZnO would result a great disturbance on the functional gene product synthesis processing, such as translation, gene expression, RNA modification, and structural constituent of ribosome. The pattern of expression of 37 genes altered by nano-ZnO (fold change>2) was different from the profile following exposure to 6 mg/L of free zinc ion. The result indicates that these two Zn forms might cause toxicity to bacterial in different modes of action. Our results underscore the importance of understanding the adverse effects elicited by nano-ZnO after entering aquatic environment.

Biodegradability is a desired characteristic for synthetic soil amendments. Cross-linked polyacrylic acid (PAA) is a synthetic superabsorbent used to increase the water availability for plant growth in soils. About 4 % within products of cross-linked PAA remains as linear polyacrylic acid (PAAₗᵢₙₑₐᵣ). PAAₗᵢₙₑₐᵣhas no superabsorbent function but may contribute to the apparent biodegradation of the overall product. This is the first study that shows specifically the biodegradation of PAAₗᵢₙₑₐᵣin agricultural soil. Two¹³C-labeled PAAₗᵢₙₑₐᵣof the average molecular weights of 530, 400, and 219,500 g mol⁻¹were incubated in soil. Mineralization of PAAₗᵢₙₑₐᵣwas measured directly as the¹³CO₂efflux from incubation vessels using an automatic system, which is based on¹³C-sensitive wavelength-scanned cavity ring-down spectroscopy. After 149 days, the PAAₗᵢₙₑₐᵣwith the larger average molecular weight and chain length showed about half of the degradation (0.91 % of the initial weight) of the smaller PAAₗᵢₙₑₐᵣ(1.85 %). The difference in biodegradation was confirmed by the δ¹³C signature of the microbial biomass (δ¹³Cₘᵢc), which was significantly enriched in the samples with short PAAₗᵢₙₑₐᵣ(−13 ‰ against reference Vienna Pee Dee Belemnite,VPDB) as compared to those with long PAAₗᵢₙₑₐᵣ(−16 ‰ VPDB). In agreement with other polymer studies, the results suggest that the biodegradation of PAAₗᵢₙₑₐᵣin soil is determined by the average molecular weight and occurs mainly at terminal sites. Most importantly, the study outlines that the size of PAA that escapes cross-linking can have a significant impact on the overall biodegradability of a PAA-based superabsorbent.

Species sensitivity distribution (SSD) is the most common method used to derive water quality criteria, but there are still issues to be resolved. Here, issues associated with application of SSD methods, including species selection, plotting position, and cutoff point setting, are addressed. A preliminary improvement to the SSD approach based on post-stratified sampling theory is proposed. In the improved method, selection of species is based on biota of a specific basin, and the whole species in the specific ecosystem are considered. After selecting species to be included and calculating the cumulative probability, a new method to set the critical threshold for protection of ecosystem-level structure and function is proposed. The alternative method was applied in a case study in which a water quality criterion (WQC) was derived for ammonia in the Songhua River (SHR), China.

As an emerging group of endocrine-disrupting chemicals, parabens have attracted growing attention due to their potential effects on human health. In the present study, the occurrence and distribution of eight parabens, four chlorinated parabens, and their common hydrolysis product, p-hydroxybenzoic acid (PHBA), were investigated in 39 swimming pools in Beijing, China. Methyl paraben and propyl paraben were the predominant compounds in swimming pools, accounting for 91.2 % of the total parabens. It is noteworthy that octyl paraben, a paraben with longer chain, was firstly detected in this study. There were several factors affecting the levels of parabens among the 39 swimming pools. The concentrations of parabens and chlorinated derivatives detected in indoor pools (144 ng L⁻¹) were roughly 20-fold higher than those in outdoor pools (6.78 ng L⁻¹). Hotel pools appear to present higher level of target compounds (361 ng L⁻¹) than that in health club (228 ng L⁻¹), municipal (130 ng L⁻¹), school (75.6 ng L⁻¹), and community pools (63.0 ng L⁻¹). Moreover, the level of these compounds in pools during weekends (174 ng L⁻¹) was much higher than that during weekdays (52.3 ng L⁻¹). The dynamics of target compounds were also investigated to provide a general trend of the level of parabens in a school indoor swimming pool during a 14-week period. Human exposure assessment was conducted to estimate the potential risk of exposure to parabens and their chlorinated derivatives in swimming pools. Considering the total exposure dose of multiple parabens, human exposure to parabens from the water of swimming pools is negligible. However, the threat of these parabens to children in swimming pool should be concerned.

Daily PM₁₀ and PM₂.₅ samples were collected between April 2009 and July 2010 at a rural site (Sinop) situated on the coast of the Central Black Sea. The concentrations of PM₁₀ and PM₂.₅ were 23.2 ± 16.7 and 9.8 ± 6.9 μg m⁻³, respectively. Coarse and fine filters were analyzed for Cl⁻, NO₃ ⁻, SO₄ ²⁻, C₂O₄ ²⁻, PO₄ ³⁻, Na⁺, NH₄ ⁺, K⁺, Mg²⁺, and Ca²⁺ by using ion chromatography. Elemental and organic carbon content in bulk quartz filters were also analyzed. The highest PM₂.₅ contribution to PM₁₀ was found in summer with a value of 0.54 due to enhanced secondary aerosols in relation to photochemistry. Cl⁻, Na⁺, and Mg²⁺ illustrated their higher concentrations and variability during winter. Chlorine depletion was chiefly attributed to nitrate. Higher nssCa²⁺ concentrations were ascribed to episodic mineral dust intrusions from North Africa into the region. Crustal material (31 %) and sea salt (13 %) were found to be accounted for the majority of the PM₁₀. The ionic mass (IM), particulate organic matter (POM), and elemental carbon (EC) explained 13, 20, and 3 % of the PM₁₀ mass, correspondingly. The IM, POM, and EC dominated the PM₂.₅ (~74 %) mass. Regarding EU legislation, the exceeded PM₂.₅ values were found to be associated with secondary aerosols, with a particular dominance of POM. For the exceeded PM₁₀ values, six of the events were dominated by dust while two and four of these exceedances were caused by sea salt and mix events, respectively.