Aerosol optical properties were measured and analyzed through the ground-based remote sensing Aerosol Robotic Network (AERONET) over an urban-industrial site, Nanjing (32.21° N, 118.72° E, and 62 m above sea level), in the Yangtze River Delta, China, during September 2007–August 2008. The annual averaged values of aerosol optical depth (AOD₅₀₀) and the Ångström exponent (AE₄₄₀–₈₇₀) were measured to be 0.94 ± 0.52 and 1.10 ± 0.21, respectively. The seasonal averaged values of AOD₅₀₀ (AE₄₄₀–₈₇₀) were noticed to be high in summer (autumn) and low in autumn (spring). The characterization of aerosol types showed the dominance of mixed type followed by the biomass burning and urban-industrial type of aerosol at Nanjing. Subsequently, the curvature (a ₂) obtained from the second-order polynomial fit and the second derivative of AE (α′) were also analyzed to understand the dominant aerosol type. The single scattering albedo at 440 nm (SSA₄₄₀) varied from 0.88 to 0.93 with relatively lower (higher) values during the summer (spring), suggesting an increase in black carbon and mineral dust (desert dust) aerosols of absorbing (scattering) nature. The averaged monthly and seasonal evolutions of shortwave (0.3–4.0 μm) direct aerosol radiative forcing (DARF) values were computed from the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model both at the top of atmosphere (TOA) and bottom of atmosphere (SUR) during the study period. Further, the aerosol forcing efficiency (AFE) and the corresponding atmospheric heating rates (AHR) were also estimated from the forcing within the atmosphere (ATM). The derived DARF values, therefore, produced a warming effect within the atmosphere due to strong absorption of solar radiation.

This paper proposes multilayer perceptron neural network (MLPNN) to predict phycocyanin (PC) pigment using water quality variables as predictor. In the proposed model, four water quality variables that are water temperature, dissolved oxygen, pH, and specific conductance were selected as the inputs for the MLPNN model, and the PC as the output. To demonstrate the capability and the usefulness of the MLPNN model, a total of 15,849 data measured at 15-min (15 min) intervals of time are used for the development of the model. The data are collected at the lower Charles River buoy, and available from the US Environmental Protection Agency (USEPA). For comparison purposes, a multiple linear regression (MLR) model that was frequently used for predicting water quality variables in previous studies is also built. The performances of the models are evaluated using a set of widely used statistical indices. The performance of the MLPNN and MLR models is compared with the measured data. The obtained results show that (i) the all proposed MLPNN models are more accurate than the MLR models and (ii) the results obtained are very promising and encouraging for the development of phycocyanin-predictive models.

Laboratory batch and column experiments were performed to better understand the effects of Ca²⁺, Mg²⁺, and HCO₃ ⁻ on Cr(VI) removal from aqueous systems with pyrite. Batch results show that increasing HCO₃ ⁻ concentration led to an increase in Cr(VI) removal by pyrite due to pH buffering capacity of HCO₃ ⁻. However, while Ca²⁺ and Mg²⁺ individually had no effect on Cr(VI) removal at pH 4, the addition of Ca²⁺ or Mg²⁺ to systems containing HCO₃ ⁻ resulted in a significant decrease in Cr(VI) removal at pH 8 relative to the systems containing HCO₃ ⁻ alone. The XPS data proved that while Ca²⁺ precipitated as CaCO₃₍S₎ onto pyrite surface, Mg²⁺ sorbed and/or accumulated as Mg(OH)₂₍S₎ onto oxidized pyrite surface. The formation of surface precipitates (e.g., CaCO₃) inhibited further Cr(VI) reduction by blocking electron transfer between Cr(VI) and pyritic surface sites. While the precipitation of Ca²⁺ as CaCO₃ led to a significant decrease in effluent pH, the decrease in effluent pH was very low in systems containing Mg²⁺, most probably due to much higher solubility of Mg²⁺ at pH 8. Zeta potential measurements provided further evidence that while Ca²⁺ or Mg²⁺ had no effect on zeta potential of pyrite particles under acidic conditions (e.g., pH < 7), the addition of Ca²⁺ or Mg²⁺ to systems containing Cr(VI) reversed the pyrite surface potential from negative to positive under alkaline pH conditions (e.g., pH > 8) relative to system containing only Cr(VI), suggesting the sorption and/or accumulation of surface precipitates on pyrite surface.

The major obstacle to biological denitrification is the cost of the carbon source used as electron donor. Therefore, it is desirable to identify inexpensive alternatives to enable efficient denitrification. Corn husk, a type of agroforestrial waste, has the potential to release organic materials. This study investigated the possibility of enhancing aerobic denitrification by thermophilic Chelatococcus daeguensis TAD1 when corn husk that had been pretreated with hydrolysate was employed as the carbon source. The results showed that the particle size of 10–40 mesh, the NaOH dose of 0.01 mol L⁻¹, the loading dose of 60 g L⁻¹, the temperature of 40 °C, and pretreatment time of 24 h were appropriate to release available carbon source for denitrification by TAD1. Additionally, an initial pH of 8.5 was optimal for denitrification with maximum N₂O production as low as 0.053 % of denitrified NO₃ ⁻-N, which was the least at pH 6.0–9.0, taking advantage of corn husk hydrolysate (CHH). At an initial NO₃ ⁻-N of 253.36 mg L⁻¹, the denitrification rate and removal efficiency reached 24.55 mg L⁻¹ h⁻¹ and 96.91 %, respectively, without accumulation of nitrite and N₂O utilizing CHH as a sole carbon source. To sum up, CHH was an economical and efficient carbon source for aerobic denitrification by TAD1 with low levels of N₂O, capable of tolerating the fluctuation of pH and the high nitrate load.

This paper investigated the influence of various florfenicol concentrations on the treatment effect of greenhouse turtle breeding wastewater by intermittent aeration dynamic membrane bioreactor (IADMBR). The results showed that when the florfenicol concentration reached 80 and 120 ng L⁻¹, the average removal efficiencies of ammonia nitrogen and chemical oxygen demand (COD) decreased by 32 and 48 %, respectively. Thus, the enhanced removal of florfenicol and its maintenance at a low concentration are prerequisites to ensure excellent effluent quality. Orthogonal experiments showed that the optimized IADMBR process parameters were hydraulic retention time (HRT) = 5 h, sludge retention time (SRT) = 30 days, and C/N = 2.5; using this combination, the florfenicol concentration was reduced to 25.8 ng L⁻¹, and the average removal efficiency was as high as 78.5 %. The large-scale field pilot test showed that the optimized IADMBR process not only ensured standardized discharge of greenhouse turtle breeding wastewater but also effectively reduced antibiotic pollution and was thus worthy of use in practical applications.

Acid drainage is an environmental liability that impacts the quality of surface waters. However, the precipitation of iron and aluminum oxy/hydroxides decreases the concentration of dissolved toxic metals (such as arsenic) in rivers that receive acid drainage. Additionally, hydrodynamic factors (e.g., flow velocity fields and mixing ratios) control incomplete chemical mixing. Despite the occurrence of incomplete mixing in streams, its role on the fate and transport of contaminants has not been explored. We analyzed these processes at the Azufre River (pH 2)–Caracarani River (pH 8.6) confluence, northern Chile. We performed cross-sectional measurements of pH, turbidity, and particle size distributions and sampled water and suspended solids to analyze iron, aluminum, and arsenic. To complement field measurements, mixing experiments and geochemical modeling were performed. We found that there were distinct mixing zones on the field that promoted the precipitation of iron phases (pH >3) or the precipitation of iron and aluminum phases (pH ∼5). While iron phases immobilized arsenic by sorption (up to 8700 mg kg⁻¹ of arsenic concentration in the solid phase), aluminum contributed to produce particles with the capacity to resist shear stress (strength factors ∼90 %). More than 50 % of the total arsenic was removed from the aqueous phase within 100 m from the junction point, suggesting settling of iron and aluminum particles. These results showed that incomplete mixing was a controlling factor in the fate and transport of arsenic. Fluvial confluences receiving acid drainage are natural reactors that can attenuate toxic metals. A better understanding of the chemical-hydrodynamic interactions in fluvial confluences can lead to new strategies for enhanced attenuation of toxic metals.

Mine soils often contain high levels of metals that produce serious environmental problems and poor fertility conditions that limit their reclamation. The aim of this study was to evaluate the influence of a compost and biochar amendment on the nutrient phytoavailability in a mine soil from the depleted copper mine of Touro (Spain). For this purpose, a greenhouse experiment was carried out amending the mine soil with increasing proportions (20, 40, 80 and 100%) of the compost and biochar mixture and planting Brassica juncea plants. The results revealed that the mine soil had an extremely acid pH and low fertility conditions and was affected by copper contamination. The addition of compost and biochar to the mine soil increased soil pH values (from 2.7 to 8.7), total carbon (from undetectable values to 149 g kg⁻¹) and total nitrogen (from undetectable values to 11,130 mg kg⁻¹) contents and phytoavailable concentrations of K, Mg, Na and P and promoted plant growth, since B. juncea plants did not survive in the untreated mine soil. The application of amendment decreased the phytoavailable concentration of Al, Co, Cu, Fe and Ni in the soil, resulting in a reduction of copper toxicity. The use of compost and biochar as a soil amendment combined with B. juncea plants could be an efficient strategy for the reclamation of degraded soils with low fertility conditions.

Microbial desalination cells (MDCs) have been studied for contaminant removal from wastewater and salinity reduction in saline water. However, in an MDC wastewater treatment and desalination occurs in different streams, and high salinity of the treated wastewater creates challenges for wastewater reuse. Herein, a single-stream MDC (SMDC) with four chambers was developed for simultaneous organic removal and desalination in the same synthetic wastewater. This SMDC could achieve a desalination rate of 12.2–31.5 mg L⁻¹ h⁻¹ and remove more than 90 % of the organics and 75 % of NH₄⁺-N; the pH imbalance between the anode and cathode chambers was also reduced. Several strategies such as controlling catholyte pH, increasing influent COD concentration, adopting the batch mode, applying external voltage, and increasing the alkalinity of wastewater were investigated for improving the SMDC performance. Under a condition of 0.4 V external voltage, anolyte pH adjustment, and a batch mode, the SMDC decreased the wastewater salinity from 1.45 to below 0.75 mS cm⁻¹, which met the salinity standard of wastewater for irrigation. Those results encourage further development of the SMDC technology for sustainable wastewater treatment and reuse.

Acid mine drainage (AMD) impairs many streams throughout the historical and current coal mining regions. Abandoned mines often have sulfur-rich coal that produces sulfuric acid after exposure to water and oxygen. These streams are characterized by lowered pH, increased metal load, and decreased biotic assemblage complexity in comparison to unimpaired streams. Remediation efforts using alkaline addition have been successful in reducing the impacts of AMD by improving the chemical environment and reestablishing biotic assemblages that more closely resemble unimpacted streams. We used phospholipid fatty acids (PLFA) to detect changes in biofilm fatty acid profiles, differences in specific fatty acid biomarkers, and nutritional quality among AMD-unimpaired, AMD-impaired, and AMD-remediated stream sites in southeastern Ohio (USA). In general, the physical, chemical, and biological measurements of the remediated sites were intermediate between the unimpaired and impaired streams. PLFA content was five times greater in AMD-unimpaired sites when compared to AMD-impaired and double that of AMD-remediated sites. PLFA profiles separated sites of the three categories into two statistically distinct groups: AMD-unimpaired/AMD-remediated and AMD-impaired. The results of this study showed that PLFA profiles have great promise as an additional metric to evaluate AMD impact for stream biomonitoring programs.

Biogas slurry is a product of anaerobic digestion of manure that has been widely used as a soil fertilizer. Although the use for soil fertilizer is a cost-effective solution, it has been found that repeated use of biogas slurry that contains high heavy metal contents can cause pollution to the soil-plant system and risk to human health. The objective of this study was to investigate effects of biogas slurry on the soil-plant system and the human health. We analyzed the heavy metal concentrations (including As, Pb, Cu, Zn, Cr and Cd) in 106 soil samples and 58 plant samples in a farmland amended with biogas slurry in Taihu basin, China. Based on the test results, we assessed the potential human health risk when biogas slurry containing heavy metals was used as a soil fertilizer. The test results indicated that the Cd and Pb concentrations in soils exceeded the contamination limits and Cd exhibited the highest soil-to-root migration potential. Among the 11 plants analyzed, Kalimeris indica had the highest heavy metal absorption capacity. The leafy vegetables showed higher uptake of heavy metals than non-leafy vegetables. The non-carcinogenic risks mainly resulted from As, Pb, Cd, Cu and Zn through plant ingestion exposure. The integrated carcinogenic risks were associated with Cr, As and Cd in which Cr showed the highest risk while Cd showed the lowest risk. Among all the heavy metals analyzed, As and Cd appeared to have a lifetime health threat, which thus should be attenuated during production of biogas slurry to mitigate the heavy metal contamination.