Samples were collected from the middle and lower reaches of the Yangtze River, China, to study the concentrations, distributions, and compositions of 16 US-EPA priority polycyclic aromatic hydrocarbons (PAHs) in water and suspended particulate matter (SPM). We also evaluated sources of the PAHs and their potential toxicity. Total concentrations of the PAHs (ΣPAHs) in water ranged from 17.33 to 77.12 ng L⁻¹, and in SPM, the levels ranged from 595.91 to 2473.74 ng g⁻¹. Total concentrations of seven carcinogenic PAHs (ΣCPAHs) ranged from 7.63 to 13.02 ng L⁻¹ in water and 276.55 to 1216.89 ng g⁻¹ in SPM. PAH levels in water samples were relatively low, and those in the lower reaches were higher than in the middle reaches. SPM samples had higher levels of PAHs, especially in the lower reaches and in Dongting Lake and Poyang Lake. Principal component analysis (PCA) with multiple linear regression analysis (MLR) was performed to quantitatively characterize the PAH sources. Two factors and their contributions were identified from water samples. Coal and wood combustion accounted for 74.1 % of the PAHs, and petroleum emissions explained 25.9 % of the PAHs. Three source factors were identified from SPM samples: these were vehicular emissions (46.3 % of PAHs), wood and coal combustion (40.4 % of PAHs), and petrogenic sources (13.3 %). Ecological risk assessment indicated that a moderate undesirable impact will be caused by PAHs, and some control measures and remedial actions should be conducted.

Studies on replacement of inorganic fertilizer with organic residues to improve crop productivity and their impact on greenhouse gas emission from agricultural soil merit more attention. Two-year field experiments were conducted to study the impact of different organic residues with varied carbon (C)/nitrogen (N) ratios as substitutes of chemical fertilizer on emission reduction of nitrous oxide (N₂O) and crop yield from a tropical summer rice paddy of India. Five treatments comprising of conventional N fertilizer (NPK), cow manure (CD), rice straw (RS), poultry manure (PM), and sugarcane bagasse (SCB) were applied in a rice field to estimate N₂O emission. Application of CD (at 10 t ha⁻¹) resulted in maximum reduction of seasonal N₂O emissions (15 %) over NPK, RS, PM, and SCB. Application of CD and RS enhanced leaf photosynthetic rate and caused maximum utilization of photosynthates towards developing grains as evident from grain filling ability and higher grain yield. Substitution of NPK with organic residues enhanced soil nutrient availability in terms of C and N resulting in improved soil fertility and to some extent influenced soil nitrogen processes which in turn reduced N₂O emissions. We conclude that suitable management of soil in agricultural ecosystem can reduce the emission of N₂O and protect and preserve the soil health without compromising the agronomic productivity reducing the use of chemical fertilizer and maintaining the sustainability of rice ecosystem as evident from lower carbon equivalent emissions (CEE) and higher carbon efficiency ratio (CER) at CD in rice paddies in the present study.

An endophytic isolate identified as Diaporthe sp. was explored for its biosorption and biodegradation potential on triphenylmethane (TPM) dyes. Treatment with live cells demonstrated strong decolorization activities towards methyl violet (MV, 100 mg L⁻¹), crystal violet (CV, 100 mg L⁻¹), and malachite green (MG, 50 mg L⁻¹), with 84.87, 78.81, and 87.80 %, respectively. These values are far greater than decolorization by dead cells via biosorption (DE% of 18.82–48.32 %). The absence of peaks in the UV-vis spectra after 14 days further suggested degradation of dye chromophores. Results revealed that Diaporthe sp. removed TPM dyes through biodegradation and biosorption, with the former as a more desirable mechanism due to its ability to degrade most dye chromophore and enhance decolorization efficiency, and as a mechanism to tolerate toxic MG. As such, application of live cells of Diaporthe sp. is advantageous as it allows biodegradation to occur.

Tropical forests play an important role in carbon cycle. However, the temporal and spatial variation in soil carbon dioxide (CO₂) emission of tropical forest remains uncertain, especially near the Tropic of Cancer. In this research, we studied the annual soil CO₂ fluxes from three tropical montane rainforests on the Hainan Island of China (pristine montane rainforest, PF; secondary montane rainforest, SF; and Podocarpus imbricatus plantation, PP). The results showed a lower annual average soil CO₂ flux as 6.85 ± 0.52 Mg C-CO₂ ha⁻¹ (9.17 Mg C-CO₂ ha⁻¹ in the wet season and 4.50 Mg C-CO₂ ha⁻¹ in the dry season). The CO₂ fluxes exhibited obviously seasonal variation during the study period. Among the three forest types, PF had the highest average CO₂ flux rate of 317.77 ± 147.71 mg CO₂ m⁻² h⁻¹ (433.08 mg CO₂ m⁻² h⁻¹ in the wet season and 202.47 mg CO₂ m⁻² h⁻¹ in the dry season), followed by PP of 286.84 ± 137.48 mg CO₂ m⁻² h⁻¹ (367.12 mg CO₂ m⁻² h⁻¹ in the wet season and 206.56 mg CO₂ m⁻² h⁻¹ in the dry season) and SF of 255.09 ± 155.26 mg CO₂ m⁻² h⁻¹ (351.48 mg CO₂ m⁻² h⁻¹ in the wet season and 155.71 mg CO₂ m⁻² h⁻¹ in the dry season). We found between CO₂ fluxes and soil temperature a highly significant linear relation (P < 0.01) at 5 cm depth and a highly significant exponential correlation (P < 0.01) at 10 cm depth for all three forest types; a significant linear relation (P < 0.05) between CO₂ fluxes and soil moisture content was found for SF and PF, but not for PP (P > 0.05). The CO₂ flux was significantly correlated (P < 0.05) with water-filled pore space only for PF. In conclusion, our results suggested soil CO₂ fluxes in the three forest types that exhibit obviously spatial and temporal variation, and the temperature is the major factor affecting soil CO₂ fluxes from this region.

Herbaspirillum chlorophenolicum strain FA1, a gram-negative bacterium isolated from activated sludge, was found to be able to use pyrene as sole carbon and energy sources. During biodegradation, the contribution of biosorption to the whole pyrene removal mattered in the early reaction stage, and biodegradation was the predominant process. Pyrene biodegradation was significantly enhanced with the presence of a typical carboxylated aromatic metabolite (phthalic acid) at concentrations of 30–50 mg l⁻¹, and the metabolite itself could also be efficiently biodegraded. For the purpose of practical application, immobilization of strain FA1 was carried out, and polyvinyl alcohol (PVA)-diatomite carrier by chemical method was proved to be the most efficient, with a PYR biodegradation of 92.8 % in 10 days. Investigation on the pyrene biodegradation kinetics by both free and immobilized cells showed that the experimental data fitted well to the first-order kinetic model. Besides, the PVA-diatomite carrier (chemical method) could be reused in at least eight consecutive biodegradation processes of PYR without any significant decrease in biodegradation efficiency. Further storage stability tests revealed that the ability to degrade pyrene using immobilized cells remained stable after storage at 4 °C for 45 days. Moreover, strain FA1 exhibited a relative broad substrate profile, including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, benzo[b]fluoranthene, benzene, toluene, and Tween 80. Taken together, results indicate that strain FA1 might be high potential in the development of treatment technologies for PAHs contamination.

Medium-pressure (MP) ultra violet (UV) disinfection was suggested as a pre-treatment to control biofouling in a semi-scale flow-through model water system. Water, spiked with Pseudomonas aeruginosa, nutrients, and carbon source, was flowed through the system and biofilm formation on glass, PVC, and stainless steel 316 slides was examined following 24 h runs. Following UV exposure a ∼99 % reduction in biovolume and average thickness of the biofilm was observed on all surfaces examined, despite clear differences in the virgin surface characteristics analyzed using contact angle, zeta potential, and atomic force microscopy (AFM). The findings support the stochastic behavior of biological systems in relation to predictions derived from conventional theories. The reduction of viable microbial counts seems to be the major mechanism in reducing the actual biofilm formation rate and the overall effect UV provides could indeed render it an effective tool in mitigating biofilm formation in water distribution systems.

Both ultrafine particles (UFP) and polycyclic aromatic hydrocarbons (PAHs) are widely present in the environment, thus increasing their chances of exposure to human in the daily life. However, the study on the combined toxicity of UFP and PAHs on respiratory system is still limited. In this study, we examined the potential interactive effects of silica nanoparticles (SiNPs) and benzo[a]pyrene (B[a]P) in bronchial epithelial cells (BEAS-2B). Cells were exposed to SiNPs and B[a]P alone or in combination for 24 h. Co-exposure to SiNPs and B[a]P enhanced the malondialdehyde (MDA) contents and reduced superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities significantly, while the reactive oxygen species (ROS) generation had a slight increase in the exposed groups compared to the control but not statistically significant. Cell cycle arrest induced by the co-exposure showed a significant percentage increase in G2/M phase cells and a decrease in G0/G1 phase cells. In addition, there was a significant increase in BEAS-2B cells multinucleation as well as DNA damage. Cellular apoptosis was markedly increased even at the low-level co-exposure. Our results suggest that co-exposure to SiNPs and B[a]P exerts synergistic and additive cytotoxic and genotoxic effects.

Fe₃O₄-CuO@montmorillonite was prepared using coprecipitation method, and its structure was determined by XRD, IR, and transmission electron micrograph (TEM). Montmorillonite in Fe₃O₄-CuO@montmorillonite nanocomposite allowed the silicate layer of montmorillonite to behave as a barrier, which prevented the agglomeration and natural crystallization of Fe₃O₄ and CuO. Furthermore, the chlorine dioxide (ClO₂) oxidative degradation of anthracene-contaminated soil was studied in detail using Fe₃O₄-CuO@montmorillonite as a magnetic heterogeneous catalyst. The operating parameters such as ClO₂ concentration, catalyst dosage, reaction time, and pH were evaluated. Compared with the conventional ClO₂ oxidation process without the catalyst, the ClO₂ catalytic oxidation system could significantly enhance the degradation efficiency. Under the optimal condition (anthracene concentration 89.8 mg/kg, water soil mass ratio 3:1, initial pH 7, ClO₂ concentration 1 mol/kg, catalyst dosage 1 g/kg, reaction time 30 min, and reaction temperature 25 °C), anthracene degradation efficiency achieved 96.2 %. The catalyst could be easily reused by magnetic separation and used at least 8 cycles without obvious loss of activity. The kinetic studies revealed that the ClO₂ catalytic oxidation degradation of anthracene-contaminated soil with Fe₃O₄-CuO@montmorillonite as catalyst followed pseudo-first-order kinetics with respect to ClO₂ concentration. Thus, this study showed potential application of ClO₂ catalytic oxidation process in remediation of organic pollutant-contaminated soil.

Wintertime precipitation sample data from 55 Snowpack sites and 17 National Atmospheric Deposition Program (NADP)/National Trends Network Wetfall sites in the Rocky Mountain region were examined to identify long-term trends in chemical concentration, deposition, and precipitation using Regional and Seasonal Kendall tests. The Natural Resources Conservation Service snow-telemetry (SNOTEL) network provided snow-water-equivalent data from 33 sites located near Snowpack- and NADP Wetfall-sampling sites for further comparisons. Concentration and deposition of ammonium, calcium, nitrate, and sulfate were tested for trends for the period 1993–2012. Precipitation trends were compared between the three monitoring networks for the winter seasons and downward trends were observed for both Snowpack and SNOTEL networks, but not for the NADP Wetfall network. The dry-deposition fraction of total atmospheric deposition, relative to wet deposition, was shown to be considerable in the region. Potential sources of regional airborne pollutant emissions were identified from the U.S. Environmental Protection Agency 2011 National Emissions Inventory, and from long-term emissions data for the period 1996–2013. Changes in the emissions of ammonia, nitrogen oxides, and sulfur dioxide were reflected in significant trends in snowpack and wetfall chemistry. In general, ammonia emissions in the western USA showed a gradual increase over the past decade, while ammonium concentrations and deposition in snowpacks and wetfall showed upward trends. Emissions of nitrogen oxides and sulfur dioxide declined while regional trends in snowpack and wetfall concentrations and deposition of nitrate and sulfate were downward.

Nanoscale zero-valent iron (NZVI) particles can be used for in situ groundwater remediation. The spatial particle distribution plays a very important role in successful and efficient remediation, especially in heterogeneous systems. Initial sand permeability (k ₀) influences on spatial particle distributions were investigated and quantified in homogeneous and heterogeneous systems within the presented study. Four homogeneously filled column experiments and a heterogeneously filled tank experiment, using different median sand grain diameters (d ₅₀), were performed to determine if NZVI particles were transported into finer sand where contaminants could be trapped. More NZVI particle retention, less particle transport, and faster decrease in k were observed in the column studies using finer sands than in those using coarser sands, reflecting a function of k ₀. In heterogeneous media, NZVI particles were initially transported and deposited in coarse sand areas. Increasing the retained NZVI mass (decreasing k in particle deposition areas) caused NZVI particles to also be transported into finer sand areas, forming an area with a relatively homogeneous particle distribution and converged k values despite the different grain sizes present. The deposited-particle surface area contribution to the increasing of the matrix surface area (θ) was one to two orders of magnitude higher for finer than coarser sand. The dependency of θ on d ₅₀ presumably affects simulated k changes and NZVI distributions in numerical simulations of NZVI injections into heterogeneous aquifers. The results implied that NZVI can in principle also penetrate finer layers.