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.

Secondary copper smelting (SeCu) is widely considered to be an important source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs and PCDFs; PCDD/Fs). Laboratory experiments were performed using SeCu fly ash as a matrix for thermochemical reactions to investigate the effects of fly ash on the formation of PCDD/Fs and the potential mechanisms. Thermochemical reactions on SeCu fly ash over a temperature range of 250–450 °C and reaction times of 10–120 min caused the PCDD/F concentrations in the fly ash to increase significantly. The PCDD/F concentrations formed in the thermal reactions were about 99–139 times higher than the PCDD/F concentrations in the original fly ash, clearly indicating that fly ash promoted the formation of PCDD/Fs. The PCDFs dominated the PCDDs, and the PCDF/PCDD concentration ratio was about 30–40. Octachlorodibenzofuran (OCDF), octachlorodibenzo-p-dioxin, and the heptachlorodibenzofurans were the most dominant homologs that were formed. A comparison of the PCDD/F patterns produced in the thermochemical reactions and the patterns in the original fly ash suggested that the chlorination of less chlorinated PCDFs might be an important pathway in the formation of higher chlorinated furans. The results of this study indicated that SeCu fly ash has a high PCDD/F formation potential. It is crucial to have the fly ash filter at low temperature and that fly ash in the cooling system should be minimized.

The main source of natural estrogens to municipal wastewater is human excretions via urine or feces, thus their concentrations in raw wastewater should show positive linear relationship with their human excretions. This study mainly focused on their concentration relationship in raw wastewater. Based on comparison between chemical analyses and predictions through human excretion rates, the observed concentrations of estriol (E₃) in municipal wastewater were found to be noticeably lower than the predicted values. The main cause for the disparity is that substantial conjugated E₃also exists in raw wastewater. This work suggested that monitoring both E₃and its conjugates is necessary to get more accurate E₃removal performance of wastewater treatment plants (WWTPs).

Exposure of tryptophan (Trp) in aqueous solutions to UVA radiation resulted in decrease of Trp (C1) but generated an unknown fluorescent component (C2) with fluorescence emission maxima extending into wavelength range characteristic of humic substance (HS)-like material. The intensity of the two components (C1 and C2) could be operationally fit to linear functions of the illumination time t (0~40 h). However, C1 and C2 decreased and increased nonlinearly respectively in a mixture (Trp mixed with a reference sample of natural organic matter, i.e., NOM) which was exposed to the same UVA illumination, and the change of both C1 and C2 was faster than that in the absence of NOM. Moreover, the UV-Vis absorption maximum (ex = 278 nm) of Trp was faster removed for the mixture (after 5 h) than for Trp solutions without NOM (after 20 h). These observations suggested NOM-facilitated photobleaching of Trp and photoproduction of a new FDOM component under UVA illumination. Meanwhile, the fluorescence of the NOM in the absence of Trp was well represented by two HS-like components which decayed monotonically upon exposure to UVA light, while the photoinduced decay became nonmonotonic in the presence of Trp, and one component even increased with illumination during certain time window, indicating Trp-facilitated production of HS-like fluorescence signatures from NOM. The findings show that UVA-induced optical signature changes of tryptophan and HS-like materials are coupled and highlight the potential impact of absorption of solar UVA light by natural dissolved organic matter (DOM) on using the optical signatures to trace sources and sinks of DOM.