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As a hydrophobic pollutant, benzo(a)pyrene (BaP) is difficult to be degraded by microbes due to its poor water solubility. To improve its water solubility, this study harvested a biosurfactant from swine wastewater. The role of the biosurfactant in BaP biodegradation in contaminated water and soil were investigated. The biodegradation kinetics of BaP in contaminated water and the improvement of soil properties were determined. Results showed that critical micelle concentration (CMC) of the biosurfactant was 46.8 mg/L. The biosurfactant has a high pH stability in range of 3–9 and a strong salt stability in NaCl concentration range of 0–20%. At concentrations of 1, 2, 3, 4 and 5 CMC, the biosurfactant increased BaP water solubility by 1.4, 2.6, 4.0, 5.2 and 6.6 times. BaP biodegradation in contaminated water was effectively promoted by the biosurfactant, and the concentrations of BaP in sludge phase decreased to 1.015 mg/L (47.9% decrement) and 0.675 mg/L (65.4% decrement) when the dosed biosurfactant were 1 and 3 CMC, respectively. The biodegradation kinetics of BaP in contaminated water by the biosurfactant fitted well with the two-compartment kinetic model well (R2 > 0.90). For the bioremediation of BaP contaminated soil, adding 0.1%–0.5% (w/w) biosurfactant biodegraded 39.2%–84.8% of BaP, while the control without biosurfactant was 24.2%. In addition, the application of the biosurfactant significantly improved the properties of the contaminated soil, behaved as the increase in microbial quantity, water holding capacity (WHC) and dehydrogenase (DH) activity of the soil. To sum up, the biosurfactant facilitated the BaP biodegradation and can be effectively used in in–site remediation of polycyclic aromatic hydrocarbons (PAHs) (BaP in this study) contaminated water and soil.

We investigated the electrochemical corrosion behavior of pyrite in simulated acid rain with different acidities and at different temperatures. The cyclic voltammetry, polarization curve, and electrochemical impedance spectroscopy results showed that pyrite has the same electrochemical interaction mechanism under different simulated acid rain conditions, regardless of acidity or environmental temperature. Either stronger acid rain acidity or higher environmental temperature can accelerate pyrite corrosion. Compared with acid rain having a pH of 5.6 at 25 °C, the prompt efficiency of pyrite weathering reached 104.29% as the acid rain pH decreased to 3.6, and it reached 125.31% as environmental temperature increased to 45 °C. Increasing acidity dramatically decreases the charge transfer resistance, and increasing temperature dramatically decreases the passivation film resistance, when other conditions are held constant. Acid rain always causes lower acidity mine drainage, and stronger acidity or high environmental temperatures cause serious acid drainage. The natural parameters of latitude, elevation, and season have considerable influence on pyrite weathering, because temperature is an important influencing factor. These experimental results are of direct significance for the assessment and management of sulfide mineral acid drainage in regions receiving acid rain.

4-[(1E)-3-Hydroxy-1-propenyl)]-2-methoxyphenol (coniferyl alcohol) is a potential marker compound for wood smoke emissions in the atmosphere. In this work, the heterogeneous reaction of coniferyl alcohol adsorbed on silica particles with NO 3 radicals was investigated. According to gas chromatography mass spectrometry (GC–MS) analysis, five products including glycolic acid, oxalic acid, 4-hydroxy-3-methoxy-benzaldehyde, 4-hydroxy-3-methoxy-benzoic acid, and 4-hydroxy-3-methoxy-5-nitrobenzaldehyde were confirmed. Based on the identified products, the reaction mechanisms were proposed and the favored sites for NO 3 electrophilic addition were olefinic C C bond and the meta -position to the hydroxyl group in the benzene ring. The obtained results might shed light on the chemical behaviors of coniferyl alcohol at night.

Methoxyphenols, as an important component of wood burning, are produced by lignin pyrolysis and considered to be the potential tracers for wood smoke emissions. In this work, the heterogeneous reaction between ferulic acid particles and NO 3 radicals was investigated. Six products including oxalic acid, 4-vinylguaiacol, vanillin, 5-nitrovanillin, 5-nitroferulic acid, and caffeic acid were confirmed by gas chromatography-mass spectrometry (GC-MS). In addition, the reaction mechanisms were proposed and the main pathways were NO 3 electrophilic addition to olefin and the meta -position to the hydroxyl group. The uptake coefficient of NO 3 radicals on ferulic acid particles was 0.17 ± 0.02 and the effective rate constant under experimental conditions was (1.71 ± 0.08) × 10 −12 cm 3 molecule −1 s −1 . The results indicate that ferulic acid degradation by NO 3 can be an important sink at night.

In this study, a biopolymer was harvested from piggery wastewater to treat biological sludge. Effectiveness of the combination of polyaluminum chloride (PAC) and this biopolymer in sludge dewatering was investigated and the dewatering mechanism was discussed. Results showed that as high as 3.11 g of biopolymer can be harvested from 1 L of piggery wastewater by cultivating Bacillus megaterium. After treated by PAC with a dosage of 1.5 g/L at pH point of 7.5, specific resistance to filtration (SRF), moisture content (MC), settled volume after 30 min (SV30) and capillary suction time (CST) of the sludge were decreased to 3.4 × 1012 m/kg, 84.5%, 79.8% and 65 s, respectively, and dry solid (DS) was increased to 21.4%, indicated that sludge dewatering was obviously enhanced by PAC. After further treated by 2 g/L of the biopolymer, SRF, MC, SV30 and CST were further decreased to 2.1 × 1012 m/kg, 59.8%, 55.6% and 39 s, respectively, and DS was increased to 28.6%, indicated that sludge dewatering was further enhanced by the biopolymer. For the enhancing mechanism, on the one hand, the extracellular polymeric substances (EPS) was significantly disintegrated to release binding bound water, which was facilitating sludge dewatering; on the other hand, the synergistic effect of PAC coagulation and biopolymer flocculation, including charge neutralization and bridge-aggregation, were favorable to sludge dewatering. Additionally, we found that the dewatered sludge was helpful for remediation of chromium (Cr)(VI)-contaminated soil by raising soil pH and decreasing bioavailability of Cr(VI) in the soil, after remediated by 75 g/kg of the dewatered sludge for 60 days, the soil pH was increased from its initial value of 4.32–8.52, and the residue Cr(VI) in the soil extract was appeared as 2.2 mg/L.

Pyrite weathering often occurs in nature and causes heavy metal ion pollution and acid mine drainage during the process. Humic acid (HA) is a critical natural organic material that can bind metal ions, thus affecting metal transfer and transformation. In this work, in situ electrochemical techniques combined with spectroscopic analysis were adopted to investigate the interfacial processes involved in pyrite weathering with/without HA. The results showed that the pyrite weathering mechanism with/without HA is FeS2 → Fe2+ + 2S0 + 2e−. The presence of HA did not change the pyrite weathering mechanism, but HA adsorbs on the pyrite surface and inhibits the further transformation of sulfur. Furthermore, HA and Fe(II) ions can form complex at 45.0 °C. Increased concentration of HA, decreased HA solution acidity or decreased environmental temperature would all weaken the pyrite weathering, for the above conditions cause pyrite weathering to have a larger resistance of the double layer and a larger passive film resistance. Pyrite will release 73.7 g m−2·y−1 Fe2+ to solution at pH 4.5, and the amount decreases to 36.8 g m−2·y−1 in the presence of 100 mg/L HA. This study provides an in situ electrochemical method for the assessment of pyrite weathering.

Galena can be easily weathered under acid rain conditions and causes environmental issues. This process, in nature, is an electrochemical process. In situ electrochemical technology and surface analysis technology were combined to investigate this weathering process. The experimental results showed that galena weathering under simulated acid rain (SAR) could cause an initial increase in Pb2+ ions and result in the formation of a passive S0 film, and the terminal product was SO42−. Increased acidity stimulates galena weathering, and the promotion efficiency was 2208% as the pH of the SAR decreased from 5.2 to 4.2. The presence of pyrite is favourable for galena weathering, and the promotion efficiency was 150% when contained 25% (wt%) pyrite. Galena will release 1.7 g per m2 per year Pb2+ to solution when the pH of acid rain is 5.2, and the released Pb2+ will reach 95.7 g per m2 per year when the pH of acid rain is 4.2 plus the galvanic effect of pyrite.