Principal component analysis (PCA) and correlation have been used to study the variability of particle mass and particle number concentrations (PNC) in a tropical semi-urban environment. PNC and mass concentration (diameter in the range of 0.25–>32.0 μm) have been measured from 1 February to 26 February 2013 using an in situ Grimm aerosol sampler. We found that the 24-h average total suspended particulates (TSP), particulate matter ≤10 μm (PM₁₀), particulate matter ≤2.5 μm (PM₂.₅) and particulate matter ≤1 μm (PM₁) were 14.37 ± 4.43, 14.11 ± 4.39, 12.53 ± 4.13 and 10.53 ± 3.98 μg m⁻³, respectively. PNC in the accumulation mode (<500 nm) was the most abundant (at about 99 %). Five principal components (PCs) resulted from the PCA analysis where PC1 (43.8 % variance) predominates with PNC in the fine and sub-microme tre range. PC2, PC3, PC4 and PC5 explain 16.5, 12.4, 6.0 and 5.6 % of the variance to address the coarse, coarser, accumulation and giant fraction of PNC, respectively. Our particle distribution results show good agreement with the moderate resolution imaging spectroradiometer (MODIS) distribution.

Surface soil samples were collected from urban agglomeration of the Yangtze River Delta (YRD), China in 2003 and 2012, respectively. Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) were analyzed to determine if there were any changes in their levels and compositional profiles between the two sampling years. The concentrations of Σ₈PBDEs ranged from 0.553 to 13.0 μg kg⁻¹(with the mean of 3.31 μg kg⁻¹) in the 2003 samples and from 1.01 to 43.2 μg/kg (with the mean of 10.0 μg kg⁻¹) in the 2012 samples. The concentrations of Σ₃₂PCBs ranged from 0.301 to 3.29 μg kg⁻¹(with the mean of 1.01 μg kg⁻¹) in the 2003 samples and from 0.205 to 3.96 μg/kg (with the mean of 0.991 μg kg⁻¹) in the 2012 samples. The comparisons between the 2012 and 2003 data showed that PBDEs concentrations increased over the years, but PCB concentrations did not change much. BDE-209 was the major BDE congener in both the 2003 and 2012 samples, indicating that the dominant PBDE mixture production and usage in the YRD had been the commercial deca-BDE mixture. Investigation of the PBDE congener profiles indicated that there had been new input of octa-BDEs in this region in recent years. Little change was found for the pattern of PCBs congener profiles between 2 years’ samples. As such, spatial distributions of PBDEs or PCBs in surface soil samples reflected a gradient (from high to low) from the central cities out to rural areas in both the 2003 and 2012 data. In addition, high concentrations of PBDEs were observed in the industrial and residential areas, whereas high concentrations of PCBs were only observed in the industrial areas.

The main aim of this study was to determine the sorption and biodegradation parameters of trichloroethene (TCE) and tetrachloroethene (PCE) as input data required for their fate and transport modelling in a Quaternary sandy aquifer. Sorption was determined based on batch and column experiments, while biodegradation was investigated using the compound-specific isotope analysis (CSIA). The aquifer materials medium (soil 1) to fine (soil 2) sands and groundwater samples came from the representative profile of the contaminated site (south-east Poland). The sorption isotherms were approximately linear (TCE, soil 1, K d = 0.0016; PCE, soil 1, K d = 0.0051; PCE, soil 2, K d = 0.0069) except for one case in which the best fitting was for the Langmuir isotherm (TCE, soil 2, K f = 0.6493 and S ₘₐₓ = 0.0145). The results indicate low retardation coefficients (R) of TCE and PCE; however, somewhat lower values were obtained in batch compared to column experiments. In the column experiments with the presence of both contaminants, TCE influenced sorption of PCE, so that the R values for both compounds were almost two times higher. Non-significant differences in isotope compositions of TCE and PCE measured in the observation points (δ¹³C values within the range of −23.6 ÷ −24.3 ‰ and −26.3 ÷−27.7 ‰, respectively) indicate that biodegradation apparently is not an important process contributing to the natural attenuation of these contaminants in the studied sandy aquifer.

Polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) are toxic environmental pollutants that are often found in sediments. The Yangtze and Yellow rivers in China are two of the largest rivers in Asia and are therefore important aquatic ecosystems; however, few studies have investigated the PCDD/F and PCB content in the sediments of these rivers. Accordingly, this study was conducted to generate baseline data for future environmental risk assessments. In the present study, 26 surface sediments from the middle reaches of the Yellow and Yangtze rivers were analyzed for PCDD/Fs and dioxin-like (dl) PCBs by high-resolution gas chromatography and high-resolution mass spectrometry. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yellow River were 2.1–19.8, 1.11–9.9, and 0.08–0.57 pg/g (dry weight), respectively. The ranges of PCDD/F, dl-PCB, and WHO-TEQ content in sediments from the Yangtze River were 6.1–84.9, 1.8–24.1, and 0.13–0.29 pg/g (dry weight), respectively. Total organic carbon and dl-PCB contents in the Yellow River were significantly correlated (Spearman’s correlation coefficient, r = 0.64, P < 0.05). It is well known that total organic carbon plays a role in the transport and redistribution of dl-PCB. Principal component analysis indicated that PCDD/Fs may arise from pentachlorophenol, sodium pentachlorophenate, and atmospheric deposition, while dl-PCBs likely originate from burning of coal and wood for domestic heating. The dioxin levels in the river sediments examined in this study were relatively low. These findings advance our knowledge regarding eco-toxicity and provide useful information regarding contamination sources.

The response and detoxification mechanisms of three freshwater phytoplankton species (the cyanobacterium Aphanizomenon flos-aquae, the green alga Pediastrum simplex, and the diatom Synedra acus) to cadmium (Cd) were investigated. The cell growth of each species was measured over 10 days, and chlorophyll a fluorescence, Cd bioaccumulation (including surface-adsorbed and intracellular Cd), and phytochelatin (PC) synthesis were determined after 96-h exposures. The growth of the three phytoplankton species was significantly inhibited when Cd concentrations were ≥5 mg L⁻¹. Compared with P. simplex, greater growth inhibition in S. acus and A. flos-aquae occurred. The changes in chlorophyll fluorescence parameters including the maximal quantum yield of PSII (Fv/Fm) and relative variable fluorescence of the J point (Vj) demonstrated that the increase in Cd concentration damaged PSII in all three species. After 96-h exposures, the accumulation of surface-adsorbed Cd and intracellular Cd increased significantly in all three species, with the increase of Cd concentrations in the media; total cadmium accumulation was 245, 658, and 1670 times greater than that of the control in A. flos-aquae, P. simplex, and S. acus, respectively, after exposure to 10 mg L⁻¹. Total thiols exhibited a similar trend to that of Cd accumulation. PC₃ was found in A. flos-aquae and P. simplex in all Cd treatments. Glutathione (GSH) and PC₂ were also produced in response to exposure to high concentrations of Cd. PC₄ was only discovered at exposure concentrations of 10 mg L⁻¹ Cd and only in S. acus. The intracellular Cd/PCs ratio increased in all three phytoplankton with an increase in Cd concentrations, and a linear relationship between the ratio and the growth inhibition rates was observed with P. simplex and S. acus. Our results have demonstrated that metal detoxification mechanisms were dependent on the species. This study suggested that the variance of metal detoxification strategies, such as cadmium accumulation and PCs, might be an explanation why algal species have different sensitivity to Cd at various levels.

Hexaconazole is a potential fungicide to be used in the oil palm plantation for controlling the basal stem root (BSR) disease caused by Ganoderma boninense. Therefore, the dissipation rate of hexaconazole in an oil palm agroecosystem under field conditions was studied. Two experimental plots were treated with hexaconazole at the recommended dosage of 4.5 g a.i. palm⁻¹ (active ingredient) and at double the recommended dosage (9.0 g a.i. palm⁻¹), whilst one plot was untreated as control. The residue of hexaconazole was detected in soil samples in the range of 2.74 to 0.78 and 7.13 to 1.66 mg kg⁻¹ at the recommended and double recommended dosage plots, respectively. An initial relatively rapid dissipation rate of hexaconazole residues occurred but reduced with time. The dissipation of hexaconazole in soil was described using first-order kinetics with the value of coefficient regression (r ² > 0.8). The results indicated that hexaconazole has moderate persistence in the soil and the half-life was found to be 69.3 and 86.6 days in the recommended and double recommended dosage plot, respectively. The results obtained highlight that downward movement of hexaconazole was led by preferential flow as shown in image analysis. It can be concluded that varying soil conditions, environmental factors, and pesticide chemical properties of hexaconazole has a significant impact on dissipation of hexaconazole in soil under humid conditions.

Silver and gold nanoparticles of Jasminum nervosum L. had unique optical properties such as broad absorbance band in the visible region of the electromagnetic spectrum. Characterization of the nanoparticles using UV spectrophotometer, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy confirmed that the particles were silver (AgNPs) and gold (AuNPs) ranging between 4–22 and 2–20 nm with an average particles size of 9.4 and 10 nm, respectively. AgNPs and AuNPs of J. nervosum had high larvicidal activity on the filarial and arboviral vector, Culex quinquefasciatus, than the leaf aqueous extract. Observed lethal concentrations (LC₅₀ and LC₉₅) against the third instar larvae were 57.40 and 144.36 μg/ml for AgNPs and 82.62 and 254.68 μg/ml for AuNPs after 24 h treatment, respectively. The lethal time to kill 50 % of C. quinquefasciatus larvae were 2.24 and 4.51 h at 150 μg/ml of AgNPs and AuNPs, respectively, while in the case of aqueous leaf extract of J. nervosum it was 9.44 h at 500 μg/ml (F ₂,₁₄ = 397.51, P < 0.0001). The principal component analysis plot presented differential clustering of the aqueous leaf extract, AgNP and AuNPs in relation to lethal dose and lethal time. It is concluded from the present findings that the biosynthesised AgNPs and AuNPs using leaf aqueous extract of J. nervosum could be an environmentally safer nanobiopesticide, and provided potential larvicidal effect on C. quinquefasciatus larvae which could be used for prevention of several dreadful diseases.

Pure and cerium-doped [0.05, 0.1, 0.3, 0.5, and 1.0 Ce nominal atomic % (at.%)] TiO₂ was synthesized by the sol–gel method. The obtained catalysts were characterized by X-ray diffraction (XRD), UV–visible diffused reflectance spectroscopy (DRS), Raman, and BET surface area measurement. The photocatalytic activity of synthesized samples for the oxidative degradation of phenol in aqueous suspension was investigated. The content of Ce in the catalysts increases both the transition temperature for anatase to rutile phase transformation and the specific surface area, and decreases the crystallite size of anatase phase, the crystallinity, and the band gap energy value. The material with higher efficiency corresponds to 0.1 Ce nominal at.%. Under irradiation with 350 nm lamps, the degradation of phenol could be described as an exponential trend, with an apparent rate constant of (9.1 ± 0.6) 10⁻³ s⁻¹ (r ² = 0.98). Hydroquinone was identified as the main intermediate.

A health risk assessment of food crops contaminated with heavy metals (Cu, Zn, Pb, As, Cd, and Cr) through the intake of cereals and vegetables grown from biogas slurry irrigated sites was conducted. In the vegetable soils and cereal soils, the concentrations of Zn, Pb, and Cd were far higher than Chinese agricultural standards. The pollution conditions of the aforementioned heavy metals varied with the seasons. Typically, the pollution was more serious in summer than in autumn. Furthermore, the accumulative properties of the heavy metals were different in the cereals and vegetables. In particular, Cu, Zn, and Pb tended to accumulate in rice with concentrations of 6.70, 36.58, and 4.14 mg kg⁻¹, respectively. Pb and Cd in cereals and vegetables exceeded the maximum permissible concentrations in China. The health risk assessment revealed that the daily intake (DI) and target hazard quotients (THQs) of Pb, As, and Cd in cereals and vegetables also exceeded the FAO/WHO limit. The results indicated that heavy metal contamination posed a severe health risk to local humans.

Sloping croplands could result in soil erosion, which leads to non-point source pollution of the aquatic system in the Three Gorges Reservoir Region. Mulberry, a commonly grown cash plant in the region, is traditionally planted in contour hedgerows as an effective management practice to control soil erosion and non-point source pollution. In this field study, surface runoff and soil N and P loss on sloping land under crop-mulberry management were investigated. The experiments consisted of six crop-mulberry treatments: Control (no mulberry hedgerow with mustard-corn rotation); T1 (two-row contour mulberry with mustard-corn rotation); T2 (three-row contour mulberry with mustard-corn rotation); T3 (border mulberry and one-row contour mulberry with mustard-corn rotation); T4 (border mulberry with mustard-corn rotation); T5 (two-row longitudinal mulberry with mustard). The results indicated that crop-mulberry systems could effectively reduce surface runoff and soil and nutrient loss from arable slope land. Surface runoff from T1 (342.13 m³ hm⁻²), T2 (260.6 m³ hm⁻²), T3 (113.13 m³ hm⁻²), T4 (114 m³ hm⁻²), and T5 (129 m³ hm⁻²) was reduced by 15.4, 35.6, 72.0, 71.8, and 68.1 %, respectively, while soil loss from T1 (0.21 t hm⁻²), T2 (0.13 t hm⁻²), T3 (0.08 t hm⁻²), T4 (0.11 t hm⁻²), and T5 (0.12 t hm⁻²) was reduced by 52.3, 70.5, 81.8, 75.0, and 72.7 %, respectively, as compared with the control. Crop-mulberry ecosystem would also elevate soil N by 22.3 % and soil P by 57.4 %, and soil nutrient status was contour-line dependent.