Bohai Sea is one of the most intensively exploited region in the world and its environment has been severely impacted by the extensive human activities. The Yellow River is the most important river which connects with the Bohai Sea. Therefore, this study focused on analyzing heavy metals (HMs) in 21 surface sediment samples collected from the Yellow River, China. Sequential extraction procedure (SEP), proposed by the Community Bureau of Reference (BCR), was applied in the present study to determine the concentration and fractionation characteristics of these HMs. The aim of this study was to investigate the spatial distribution, fractionation, risk assessment, and sources of HMs, including copper (Cu), zinc (Zn), lead (Pb), chromium (Cr), iron (Fe), manganese (Mn), and nickel (Ni). The results obtained from this research will play a significant role in understanding the migration, transformation, and accumulation of HMs for future research in study area. Results of fractionation revealed that most of the HMs in the study area mainly existed in residual fraction; however, Mn mostly existed in exchangeable fraction. A high percentage of reducible fractions was found for Cu and Pb. The mean contamination factor (Cf) values indicated that Pb was the highest. It was >1 and showed moderate contamination, followed by Cr, Cu, Mn, Ni, and Zn, had <1 and indicated low contamination. Among studied HMs Pb had higher enrichment factor (EF) as compared to others. Significant positive correlations within all studied HMs and principal component analysis (PCA) results indicated their common sources, however, Pb showed the different contamination sources. The total contents of HMs in sediment were compared with the threshold effect level (TEL) and probable effect level (PEL) sediment quality guideline (TEL/PEL-based SQGs) values for trace metals in sediment, as well as literature reported data for comparative purposes, which indicated that the selected river in present study is not severe.

The response of soil respiration (Rs) to nitrogen (N) addition is one of the uncertainties in modelling ecosystem carbon (C). We reported on a long-term nitrogen (N) addition experiment using urea (CO(NH₂)₂) fertilizer in which Rs was continuously measured after N addition during the growing season in a Chinese pine forest. Four levels of N addition, i.e. no added N (N0: 0 g N m⁻² year⁻¹), low-N (N1: 5 g N m⁻² year⁻¹), medium-N (N2: 10 g N m⁻² year⁻¹), and high-N (N3: 15 g N m⁻² year⁻¹), and three organic matter treatments, i.e. both aboveground litter and belowground root removal (LRE), only aboveground litter removal (LE), and intact soil (CK), were examined. The Rs was measured continuously for 3 days following each N addition application and was measured approximately 3–5 times during the rest of each month from July to October 2012. N addition inhibited microbial heterotrophic respiration by suppressing soil microbial biomass, but stimulated root respiration and CO₂ release from litter decomposition by increasing either root biomass or microbial biomass. When litter and/or root were removed, the “priming” effect of N addition on the Rs disappeared more quickly than intact soil. This is likely to provide a point of view for why Rs varies so much in response to exogenous N and also has implications for future determination of sampling interval of Rs measurement.

Low-cost catalysts with high activity and stability toward producing strongly oxidative species are extremely desirable, but their development still remains a big challenge. Here, we report a novel strategy for the synthesis of a magnetic CoFe₂O₄/C₃N₄ hybrid via a simple self-assembly method. The CoFe₂O₄/C₃N₄ was utilized as a photo-Fenton-like catalyst for degradation of organic dyes in the presence of H₂O₂ under natural indoor light irradiation, a green and energy-saving approach for environmental cleaning. It was found the CoFe₂O₄/C₃N₄ hybrid with a CoFe₂O₄: g-C₃N₄ mass ratio of 2:1 can completely degrade Rhodamine B nearly 100 % within 210 min under room-light irradiation. The effects of the amount of H₂O₂ (0.01–0.5 M), initial dye concentration (5–20 mg/L), solution pH (3.08-10.09), fulvic acid concentration (5–50 mg/L), different dyes and catalyst stability on the organic dye degradation were investigated. The introduction of CoFe₂O₄ on g-C₃N₄ produced an enhanced separation efficiency of photogenerated electron − hole pairs by a Z-scheme mechanism between the interfaces of g-C₃N₄ and CoFe₂O₄, leading to an excellent activity as compared with either g-C₃N₄ or CoFe₂O₄ and their mixture. This study demonstrates an efficient way to construct the low-cost magnetic CoFe₂O₄/C₃N₄ heterojunction as a typical Z-scheme system in environmental remediation.

Tetracycline (TC) in aqueous environment could be reductively degraded by using a hydrogen-based membrane biofilm reactor (H₂-MBfR) under denitrifying conditions as it provides an appropriate environment for the antibiotic-degrading bacteria in biofilm communities. This study evaluates the performance of H₂-MBfR for simultaneous removal of nitrate and TC, formation of degradation products of TC, and community analysis of the biofilm grown on the gas-permeable hollow fiber membranes. Hence, a H₂-MBfR receiving approximately 20 mg N/l nitrate and 0.5 mg/l TC was operated under different H₂ pressures, hydraulic retention times (HRTs), and influent TC concentrations in order to provide various nitrate and TC loadings. The results showed that H₂-MBfR accomplished successfully the degradation of TC, and it reached TC removal of 80–95 % at 10 h of HRT and 6 psi (0.41 atm) of H₂ gas pressure. TC degradation took placed at increased HRT and H₂ pressures while nitrate was the preferred electron acceptor for most of the electrons generated from H₂ oxidation used for denitrification. The transformation products of TC were found at part per billion levels through all the experiments, and the concentrations decreased with the increasing HRT regardless of H₂ pressure. Analyses from clone library showed that the microbial diversity at the optimal conditions was higher than that at the other periods. The dominant species were revealed to be Betaproteobacteria, Acidovorax caeni, and Alicycliphilus denitrificans.

Soil organic carbon (SOC) is one of the most important soil properties affecting many other soil and environmental properties and processes. In order to understand and manage SOC effectively, it is important to identify the scale-specific main factors affecting SOC distributions, which in this study occurred in a watershed on the Loess Plateau. Two transects were selected that passed along the upper slopes on each side of the main gully of the Liudaogou watershed. Transect 1 (3411-m length) had 27 sampling sites at 131-m intervals; transect 2 (3597 m length) had 30 sampling sites at 124-m intervals. The two transects were chosen in order to compare landscape patterns of differing complexity that were in close proximity, which reduced the effects of factors that would be caused by different locations. The landscape of transect 1 was more complex due to the greater diversity in cultivation. Multivariate empirical mode decomposition (MEMD) decomposed the total variation in SOC and five selected environmental factors into four intrinsic mode functions (IMFs) and a residual according to the scale of occurrence. Scale-specific correlation analysis was used to identify significant relationships between SOC and the environmental factors. The dominant scales were those that were the largest contributors to the total SOC variance; for transect 1, this was the IMF 1 (scale of 403 m), whereas for transect 2, it was the medium scale of the IMF 2 (scale of 688 m). For both transects, vegetation properties (vegetation cover and aboveground biomass) were the main factors affecting SOC distributions at their respective dominant scales. At each scale, the main effective factors could be identified although at the larger scales, their contributions to the overall variance were almost negligible. The distributions of SOC and the factors affecting it were found to be scale dependent. The results of this study highlighted the suitability of the MEMD method in revealing the main scale-specific factors that affect SOC distributions, which is necessary in understanding and managing this important soil property.

Reservoirs in semi-arid areas are subject to water level fluctuations (WLF) that alter biogeochemical processes in the sediment. We hypothesized that wet–dry cycles may cause internal eutrophication in such systems when they affect densely vegetated shallow areas. To assess the impact of WLF on phosphorus (P) mobilization and benthic P cycling of iron-rich sediments, we tested the effects of (i) sediment drying and rewetting, (ii) the impact of organic matter availability in the form of dried Brazilian Waterweed (Egeria densa), and (iii) alternating redox conditions in the surface water. In principle, drying led to increased P release after rewetting both in plant-free and in plant-amended sediments. Highest P mobilization was recorded in plant amendments under oxygen-free conditions. After re-establishment of aerobic conditions, P concentrations in surface water decreased substantially owing to P retention by sediments. In desiccated and re-inundated sediments, P retention decreased by up to 30 % compared to constantly inundated sediments. We showed that WLF may trigger biochemical interactions conducive to anaerobic P release. Thereby, E. densa showed high P release and even P uptake that was redox-controlled and superimposed sedimentary P cycling. Macrophytes play an important role in the uptake of P from the water but may be also a significant source of P in wet–dry cycles. We estimated a potential for the abrupt release of soluble reactive phosphorus (SRP) by E. densa of 0.09–0.13 g SRP per m² after each wet–dry cycle. Released SRP may exceed critical P limits for eutrophication, provoking usage restrictions. Our results have implications for management of reservoirs in semi-arid regions affected by WLF.

The aim of this study is to evaluate blood cadmium levels (BCLs) in Chinese adults and explore whether blood cadmium is associated with diabetes or obesity. This study included 5544 adults from a cross-sectional SPECT-China study. BCL and blood lead level (BLL) was measured by atomic absorption spectrometry. Fasting plasma glucose (FPG) was used to define prediabetes and diabetes. Overweight and obesity were defined by body mass index (BMI). The associations of BCL with prediabetes, diabetes, overweight, and obesity were analyzed by multinomial logistic regression analyses. Medians (interquartile range) of BCL were 1.97 μg/L (0.60–3.82) in men and 1.59 μg/L (0.54–3.51) in women. Subjects in low-economic-status areas and urban areas had significantly higher BCL. BCL in current smokers was significantly higher than in current non-smokers. In the adjusted model, a mild positive relationship between BCL and FPG was found. Meanwhile, the prevalence of prediabetes was increased according to the increase in BCL tertiles. Surprisingly, BCL had a negative relationship with prevalence of overweight. In conclusion, BCL in Chinese adults was much higher than in other developed countries and was influenced by gender, smoking, and residential area. BCL was positively related to prediabetes while negatively related to overweight.

The potential of mayfly Ephemera orientalis McLachlan eggs and first-instar larvae in ecotoxicological testing was investigated. Both stages of E. orientalis showed high tolerance to various environmental variables, such as water temperature, pH, water hardness, and dissolved organic carbon. Toxicological assays were conducted with three insecticides (emamectin benzoate, endosulfan, and cypermethrin), one fungicide (mancozeb), and one herbicide (paraquat dichloride). The two toxicity endpoints for the assay were the 14-day egg median hatching rate (EHC₅₀) in static and renewal exposure systems and 24-h median larval mortality (LC₅₀). Cypermethrin was the most toxic to both eggs (EHC₅₀ in static system = 36.9 μg/L; EHC₅₀ in renewal system < 0.15 μg/L) and larvae (LC₅₀ = 4.5 μg/L), and paraquat dichloride was the least toxic to eggs (EHC₅₀ in static system = 54,359.8 μg/L; EHC₅₀ in renewal system = 49541.3 μg/L) and larvae (LC₅₀ = 9259.5 μg/L). The results were compared to literature data of Daphnia magna Straus and Cloeon dipterum Linnaeus to determine its relative sensitivity to pesticides. These three species had different toxicities to the tested pesticides, especially according to the exposure system. E. orientalis eggs in the static system were found to be less sensitive were D. magna and C. dipterum, but eggs in the renewal system and larvae had similar or higher sensitivities to the tested pesticides. The results revealed that this species has potential for use in ecotoxicological testing of pesticides. Because of its geographic distribution, E. orientalis may be used as an alternative or complementary test species for ecotoxicological studies in Northeast Asian countries, where natural populations of the international standard species, D. magna, are rarely found.

Potassium-fly ash (K-FA) sorbents were investigated for high-temperature CO₂ sorption. K-FAs were synthesised using coal fly ash as source of silica and aluminium. The synthesised materials were also mixed with Li₂CO₃ and Ca(OH)₂ to evaluate their effect on CO₂ capture. Temperature strongly affected the performance of the K-FA sorbents, resulting in a CO₂ uptake of 1.45 mmol CO₂/g sorbent for K-FA 1:1 at 700 °C. The CO₂ sorption was enhanced by the presence of Li₂CO₃ (10 wt%), with the K-FA 1:1 capturing 2.38 mmol CO₂/g sorbent at 700 °C in 5 min. This sorption was found to be similar to previously developed Li-Na-FA (2.54 mmol/g) and Li-FA (2.4 mmol/g) sorbents. The presence of 10 % Li₂CO₃ also accelerated sorption and desorption. The results suggest that the increased uptake of CO₂ and faster reaction rates in presence of K-FA can be ascribed to the formation of K-Li eutectic phase, which favours the diffusion of potassium and CO₂ in the material matrix. The cyclic experiments showed that the K-FA materials maintained stable CO₂ uptake and reaction rates over 10 cycles.

This work aimed to quantify the transport and sorption behavior of four individual phthalate esters (PAEs) in sandy aquifer using column experiments so as to provide important parameters for the prediction and control of PAEs pollution plume in groundwater system. The transport curves of four individual PAEs were simulated with HYDRUS-1D through fitting linear and nonlinear equilibrium (LE/NO), linear and nonlinear, first-order, one-site non-equilibrium (LO/NO), linear and nonlinear, first-order, two-site non-equilibrium (LFO/NFO) sorption models. Simulation results showed that two-site models (LFO and NFO) displayed similar best fittings. The results from LFO model simulation showed that when water flowed 1000 m in sandy aquifer, PAEs with shorter carbon chains (DMP and DEP) transport 31.6 and 22.2 m, respectively. Unexpectedly for the same water transport distance, PAEs with longer carbon chains (DBP and DiBP) transported 40.2 and 60.7 m, respectively, which were faster than DMP and DEP, mainly due to the limited accessibility of type-2 sorption sites. The retardations were mainly caused by the sorption of PAEs on the time-dependent type-2 sites. DBP and DiBP exhibited higher mass transfer speed to and fro type-2 sites but showed lower total sorption coefficient (K) due to the limited accessibility of sorption sites. Coexistence of PAEs and smaller sorbent particles increased total K values of DBP and DiBP due to synergic development of more sorption sites with DMP and DEP.