Oxidative removal of fluorescent components from soil DOM and its effect on heavy metals around abandoned mining areas.

The oxidation stability of soil organic matter (SOM) plays an important role in the environmental chemical behavior of heavy metals (HMs). In this study, the oxidation stability of SOM and soil dissolved organic matter (DOM) for four soils around the mining area in Western China, including grassland (GR), forest land (FR), farmland soil (FA), and mining area soil (MA), was investigated. The oxidation effect of fluorescent DOM (FDOM) was determined by using synchronous fluorescence spectroscopy (SFS). The results showed that the oxidation stability of SOM for four soils follows the order: MA > GR > FR > FA. Protein-like fluorescence (A2) is dominant in soil DOM, more than 96% of which were more easily degraded. As the wavelength increases, FDOM components become more difficult to oxidize. Second derivative, two-dimensional correlation spectroscopy (2D-COS) and 1/n power transformation can identify more FDOM components, protein-like materials can be preferential removal by the oxidation process, followed by humic-like substances. The oxidation process increased the release of Cr, Cu, Zn, Pb and Fe in FA soil. Therefore, the oxidation stability of SOM and FDOM can affect the immobilization and release of HMs, and this work provides scientific guidance for remediation of soil HMs around abandoned mining areas.

Advanced synergetic nitrogen removal of municipal wastewater using oxidation products of refractory organic matters in secondary effluent by biogenic manganese oxides as carbon source.

Due to the high operational cost and secondary pollution of the conventional advanced nitrogen removal of municipal wastewater, a novel concept and technique of advanced synergetic nitrogen removal of partial-denitrification anammox and denitrification was proposed, which used the oxidation products of refractory organic matters in the secondary effluent of municipal wastewater treatment plant (MWWTP) by biogenic manganese oxides (BMOs) as carbon source. When the influent NH4+-N in the denitrifying filter was about 1.0, 2.0, 3.0, 4.0, 5.0 and 7.0 mg/L, total nitrogen (TN) in the effluent decreased from about 22 mg/L to 11.00, 7.85, 6.85, 5.20, 4.15 and 2.09 mg/L, and the corresponding removal rate was 49.15, 64.82, 69.40, 76.70, 81.36 and 90.58%, respectively. The proportional contribution of the partial-denitrification anammox pathway to the TN removal was 12.00, 26.45, 39.70, 46.04, 54.97 and 64.01%, and the actual CODcr consumption of removing 1 mg TN was 0.75, 1.43, 1.26, 1.17, 1.08 and 0.99 mg, respectively, which was much lower than the theoretical CODcr consumption of denitrification. Furthermore, CODcr in the effluent decreased to 8.12 mg/L with a removal rate of 72.40%, and the removed organic matters were mainly non-fluorescent organic matters. Kinds of denitrifying bacteria, anammox bacteria, hydrolytic bacteria and manganese oxidizing bacteria (MnOB) were identified in the denitrifying filter, which demonstrated that the advanced synergetic nitrogen removal was achieved. This novel technology presented the advantages of high efficiency of TN and CODcr removal, low operational cost and no secondary pollution.

Influence of thermal air oxidation on the chemical composition and uranium binding property of intrinsic dissolved organic matter from biochar.

In this work, uranium (U(VI)) binding characteristics of the intrinsic dissolved organic matters (DOM) from the biochars prepared under thermal air oxidation (TAO) and non-TAO conditions were studied using synchronous fluorescence spectra (SFS) and Fourier transform infrared (FTIR) in conjunction with the general two-dimensional correlation spectroscopy (2D-COS), heterospectral 2D-COS and moving-window (MW) 2D-COS. The chemical compositions of the intrinsic DOMs from biochars with/without TAO were investigated by Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS). Results showed that the preferential binding of U(VI) to functional groups followed the order: 937 (carboxyl γC-OH), 981 (carboxyl γC-OH), 1511 (aromatic vC = C), 1108 (esters or ethers vC-O), 1282 (esters or carboxyl vC-O), 1698 (saturated carboxylic acid or ketone vC = O) cm-1 for biochar DOM after TAO (OB600), and 937 (carboxyl γC-OH), 1484 (lipids δC-H or phenolic vC-O), 1201 (esters or carboxyl vC-O), 1112 (esters or ethers vC-O), 1706 (saturated aldehyde, carboxylic acid or ketone vC = O), 1060 (phenolic, esters or ethers vC-O), 1014 (phenolic, esters or ethers vC-O) cm-1 for the pristine biochar (B600). Fulvic-like substances at 375 nm in the biochar DOM showed a preferential binding with U(VI) after TAO, while humic-like substances played a more critical role in the U(VI) complexation with biochar DOM obtained from non-TAO condition. The results also indicated that TAO increased the content of fluorescent DOM and the chemical stability of DOM-U(VI) complexes. The FT-ICR MS results showed an increase in the relative abundance of protein-like, carbohydrates-like, tannins-like, unsaturated hydrocarbons, and condensed aromatic structure and a decrease in the relative abundance of lipid-like and lignin-like after TAO. Consequently, although biochar after TAO had a much poorer content of intrinsic DOM, its intrinsic DOM showed a much higher capacity in U(VI) precipitation. Therefore, the TAO substantially changed the chemical composition, binding property and environmental behavior of intrinsic DOM from biochar.

Insight into the effects of biological treatment on the binding properties of copper onto dissolved organic matter derived from coking wastewater.

Biological treatment can remove more than 89.8% of total organic carbon (TOC) and 94.4% of fluorescent dissolved organic matter (DOM) in the coking wastewater, thereby affecting the migration, transformation and bioavailability and binding characteristics of heavy metals (HMs). The results of parallel factor analysis (PARAFAC) show that protein-like materials accounted for 97.53% in the coking wastewater DOM, a large number of humic-like substances are produced and accounted for more than 55.40% after biological treatment. A new spectral data processing method, the 1/n-th power transformation after two-dimensional correlated spectroscopy (2D-COS) in combination with synchronous fluorescence spectra (SFS), can identify small features obscured by strong peaks, and reveal more binding sites as well as preserve the sequential order information. The result indicates that the preferential bonding of Cu(II) is at 306 nm (protein-like) for coking wastewater DOM, and at 514 nm (humic-like) for effluent DOM. The C-O group of esters and alcohols can preferentially complexate with Cu(II) in the coking wastewater and effluent DOM. The log KM values of PARAFAC components with Cu(II) are in the range of 3.59-5.06 for coking wastewater DOM, and in the range of 4.80-5.64 for the effluent DOM. Log KM values for protein-like materials with Cu(II) are higher than these for fulvic- and humic-like substances. Humic-like substances can form more stable complexes with Cu(II) in the effluent DOM. Biological treatment increases the chemical stability of DOM-Cu(II) complexes, thereby further reducing the environmental risk of Cu(II).

Ratiometric Monitoring of Biogenic Amines by a Simple Ammonia-Response Aiegen.

Herein, we developed a paper-based smart sensing chip for the real-time, visual, and non-destructive monitoring of food freshness using a ratiometric aggregation-induced emission (AIE) luminogen (i.e., H+MQ, protonated 4-(triphenylamine)styryl)quinoxalin-2(1H)-one) as pH sensitive indicators. Upon exposure to amine vapors, the deprotonation of H+MQ occurs and triggers its color change from blue to yellow, with the fluorescence redshift from blue to amaranth. Consequently, we successfully achieved the sensitive detection of ammonia vapors by recording the bimodal color and fluorescence changes. Given the high sensitivity of H+MQ to ammonia vapor, a paper-based smart sensor chip was prepared by depositing H+MQ on the commercial qualitative filter paper through a physical deposition strategy. After being placed inside the sealed containers, the developed H+MQ-loaded paper chip was applied to the real-time monitoring of biogenic amine contents according to its color difference and ratio fluorescence change. The detection results were further compared with those obtained by the high-performance liquid chromatography method, which verified the feasibility of the designed paper chip for the food spoilage degree evaluation. Briefly, this work indicates that the designed H+MQ-loaded paper chip could be a promising approach for improving food freshness monitoring.

Effect of biochar-derived DOM on the interaction between Cu(II) and biochar prepared at different pyrolysis temperatures.

The structure and composition of biochar-derived dissolved organic matter (DOM) at different pyrolysis temperatures differed significantly, affecting the environmental geochemical behavior of heavy metals (HMs). Herein, the binding properties of Cu(II) onto walnut-shell DOM were investigated using spectroscopic methods. The results showed that the DOM at low pyrolysis temperatures (300 °C and 500 °C) showed higher Cu(II) affinity than that at high pyrolysis temperature (700 °C). There was a preferential Cu(II) binding with fulvic-like substances (360 nm) at 300 °C, and with protein-like materials (275 nm) at 500 °C and 700 °C. The C-O group of alcohols, ethers, and esters showed preferential binding with Cu(II) at 300 °C and 700 °C pyrolysis temperatures. However, preferential bonding of Cu(II) to the C-O stretching vibration and O-H bending vibration of carboxyl was exhibited at 500 °C pyrolysis temperature. Pyrolysis temperature played a crucial role in the release of biochar-derived DOM and in the migration and bioavailability of HMs. Meanwhile, the adsorption effect of Cu(II) increased by 11.2% for biochar at 300 °C, and decreased by 15.0% and 61.1% for biochar at 500 °C and 700 °C, respectively, after the removal of DOM, suggesting that the presence of DOM influenced the adsorption behavior of biochar towards Cu(II).

Effects on the complexation of heavy metals onto biochar-derived WEOM extracted from low-temperature pyrolysis.

Biochar-derived water-extractable organic matter (WEOM) was obtained under low-temperature pyrolysis (300 °C) using corncob as raw material. WEOM may affect the mobility and bioavailability of soil heavy metals (HMs) through complexation when biochar was used for soil HM remediation. Herein, the characteristics of complexation between HMs (Cr(III) and Cu(II)) and biochar-derived WEOM were investigated by using spectroscopic techniques in conjunction with parallel factor (PARAFAC) analysis and two-dimensional correlation spectroscopy (2D-COS). Six components were identified by PARAFAC modeling, in which protein-, fulvic- and humic-like components accounted for 48.86%, 25.63% and 25.51%, respectively. A nonlinear model was employed to determine the conditional stability constant (KM) and total ligand concentration (CL) of WEOM-HM complexes. The log KM values were in the range of 4.02-5.04 for WEOM-Cr(III) and 4.04-6.58 for WEOM-Cu(II). The 2D-COS in conjunction with log-transformed synchronous fluorescence spectroscopy (SFS) suggested that WEOM components were preferentially complexed with HMs in the following order: 433/270, 433/335, 496/270, 496/335, 370/335, 433/402, 496/402, 335/290, 402/290 for Cr(III), and 290/280, 390/280, 433/280, 496/280, 433/335, 496/335, 390/335, 433/420, 496/402, 335/290, 316/290 for Cu(II). The results of 2D-FTIR-COS suggested a preferential bonding of Cr(III) to the C-N group of alkyl, and Cu(II) to the CO group of alcohols, ethers and esters. Meanwhile, the CO group of ethers and the CN group of alkyl indicated preferential susceptibilities for the addition of Cr(III) and Cu(II) at different concentrations. In addition, protein-like components had remarkably higher total ligand concentration (CL) than fulvic- or humic-like components.

Effects of hydrophyte decomposition on the binding mechanism between fluorescent DOM and copper.

Hydrophyte decomposition caused large amounts of dissolved organic matter (DOM) to enter aquatic environment that influence the migration and transformation of heavy metals (HMs). Six hydrophytes with five dry weight gradients (DWG) were used for the decomposition experiments. The results showed that protein-like materials occupy relatively high content in the hydrophyte-derived DOM. The binding properties of DOM-Cu(II) have been explored by using two-dimensional correlation spectroscopy (2D-COS) in conjunction with synchronous fluorescence spectroscopy (SFS) and log-transformed SFS. The weak signals of binding site can be amplified by the log-transformed 2D-COS analysis. Herein, more binding sites can be identified by the log-transformed 2D-COS analysis. The results reveal that tryptophan-like materials show a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively low DWG and sediment DOM, and fulvic-like substances indicate a preferential sequence of binding Cu(II) in the hydrophyte-derived DOM with a relatively high DWG. Meanwhile, the results of binding parameters indicate that the log K is the range of 3.61-4.25, 4.33-4.74, 4.59-4.97, 3.91-4.41, and 4.14-4.78 for D1-D5, respectively, suggesting that hydrophyte decomposition can change the binding affinity between DOM components and Cu(II). The complexes of fluorescent components with Cu(II) showed a high log K value at long wavelength (e.g. humic-like substances), and a relatively low fluorescent ligand proportion (f%) at shorter wavelength in the hydrophyte-derived DOM. However, the log K is the range of 3.08-4.31, 4.09-4.45, 3.93-4.35, 4.39-4.75, and 3.95-4.36 for C1-C5, separately. Protein-like substances with Cu(II) showed a relatively high log K value with the exception of C4. The log-transformed 2D-COS can be an analytical tool to understand the binding heterogeneity of DOM with HMs. The study can provide a guide for managing and controlling the effects of hydrophyte decomposition.

Study on the complexation of heavy metals onto biogas slurry DOM using two-dimensional correlation spectroscopy combined with the log-transformed synchronous fluorescence spectroscopy.

The fluorescent components of dissolved organic matter (DOM) in biogas slurry can react with heavy metals (HMs) and affect the migration, transformation, toxicity, and bioavailability of HMs in soil. Fluorescence quenching titration combined with two-dimensional correlation spectroscopy (2D-COS) can reveal the binding mechanism between HMs and different fluorescent components of biogas slurry DOM. The logarithmic-transformed (log-transformed) 2D-COS can be used to decrease the difference in the fluorescence intensity between low-intensity and high-intensity fluorophores that provides a better insight into the binding mechanism between biogas slurry DOM and HMs. Synchronous maps suggest that protein-like substances are more susceptive to the variation of the concentration of metal ions than fulvic-like substances. Asynchronous maps show that the preferential bonding of Cu(II) and Cr(III) to humic-like substances can be found in the biogas slurry DOM, as well as Fe(III) and Pb(II) to protein-like materials. DOM-Cu(II) may lead to an increasing risk of the migration of Cu(II) from soil to water environment due to the low log K values in the range from 2.93 to 3.46. Protein-like substances can also increase the environmental risk of HMs when these low-stable complexes occur migration and transformation. The potential environmental risk of protein-like with HMs follows the order: Pb(II) > Cu(II) > Cr(III). Here we demonstrate that the log-transformed 2D-COS can also identify fluorescence components at longer wavelength with relatively low content and reveals their preferential binding sequence and the number of binding sites. The study on the complexation between biogas slurry DOM and HMs provides a scientific basis for the environmental chemical behavior of HMs after the application of biogas slurry in agricultural soils.

Effects of digestate on biomass of a selected energy crop and soil properties.

BACKGROUND: A large number of digestates have not been fully utilized due to a lack of scientific, reasonable guidance, as well as imperfect technology. Hybrid giant Napier has great potential for use as a type of energy plant. As such, this study investigated the effects of digestate on the growth of a candidate energy crop and examined whether digestate was an ecologically viable means for soil restoration. RESULTS: The results showed that the total yields of all treatment groups receiving irrigation of digestate were higher (5.19-26.00%) than those of the control. The total phosphorus, total potassium, available nitrogen, available phosphorus, and available potassium content of the soil had also increased after digestate application, compared with the control. Urease activities for all treatments increased 15.28 to 69.44% more than that of the corresponding control. Soil dissolved organic matter (DOM) mainly contained humic-like and fulvic-like components through the application of digestate. More fluorescent components were also identified by two-dimensional correlation spectroscopy (2D-COS). These fluorescent components can improve the aromaticity and molecular weight of soil DOM so as to improve soil quality. CONCLUSIONS: Digestate improved not only the aboveground biomass accumulation, but also the chemical properties of the soil, which was an appropriate strategy for restoring soil quality and contributing to the sustainable development of marginal. The long-term impact of digestate application on soil quality will require additional long-term experiments. © 2020 Society of Chemical Industry.

The application of two-dimensional correlation spectroscopy for the binding properties of heavy metals onto digestate-derived DOM from anaerobic digestion of chicken manure.

Anaerobic digestate has been widely used for agricultural activities as an organic fertilizer product. Dissolved organic matter (DOM) derived from anaerobic digestate plays a key role in the speciation, bioavailability and ultimate fate of metals that is related to agriculture and food safety as well as the soil environment. Hence, the binding properties of Cu, Pb and Zn with digestate DOM are investigated using two-dimensional correlation spectroscopy (2D-COS) in combination with ultraviolet absorption, synchronous fluorescence spectra (SFS) and Fourier transform infrared (FTIR) spectroscopy. The 2D absorption COS shows that the DOM at 200 nm is most susceptive with the addition of Pb, followed by Zn and Cu. The log-transformed absorption spectra can also obtain more valuable signals than that from conventional absorption spectra. The 2D-SFS-COS indicates that protein-like peak is more sensitive to the variation of the concentration of metal ions, and fulvic-like substances can preferentially interact with the three heavy metals (HMs). The 2D-FTIR-COS reveals that Cu(II) and Zn(II) ions can be bonded preferentially to the N-H of secondary amide (II), and phenolic OH groups shows a favorable binding with Pb(II). Humic-like peaks with Cu(II) and Zn(II) obtains relatively higher log KM values than fulvic- and protein-like substances. However, the proportion of initial fluorescence (f) for DOM-Cu(II) and DOM-Zn(II) decreased with an increase in wavelength. Protein-like materials have more fluorescent substances that can combine with Cu(II) and Zn(II). This study provides a guide for understanding the geochemical behavior of metal ions in agricultural soils when anaerobic digestate is applied as an organic fertilizer product.

Effects of digestate DOM on chemical behavior of soil heavy metals in an abandoned copper mining areas.

The influence of digestate dissolved organic matter (DOM) on chemical behavior of soil heavy metals (HMs) in an abandoned copper mining areas was explored by fluorescence quenching titration and heavy metal extracting experiment. Five fluorescent components were obtained from digestate DOM by PARAFAC model combined with the EEM data. The stability constant (log KM) values were in the range of 4.95-5.53, 5.05-5.29, 5.21-6.00, and 4.12-4.75 for DOM-Cr(III), DOM-Cu(II), DOM-Fe(III) and DOM-Pb(II) complexes, respectively. Alcohols, ethers and esters in digestate DOM were preferentially combined with Fe(III), Cu(II) and Zn(II). However, phenolic hydroxyl groups were more likely to combine with Cr(III) and Pb(II). The speciation distribution of HMs indicated that mining resulted in a higher concentration of Cu(II) in the grassland soil (GS) than those in the agricultural soil (AS) and forest land soil (FS). Fe-Mn oxides and organic forms of Pb(II) increased dramatically due to mining. Digestate DOM extraction can increase the content of Cr(III), Fe(III) and Pb(II), and decrease the content of Cu(II) and Zn(II) in the AS, GS, and FS. However, the contents of HMs in the mining soil (MS) and slag soil (SS) decreased due to the application of digestate DOM, except for Cu(II) in the SS.

Investigating adsorption performance of heavy metals onto humic acid from sludge using Fourier-transform infrared combined with two-dimensional correlation spectroscopy.

Efforts to improve sludge resource utilization have become increasingly important. In this study, humic acid (HA) was extracted from sludge samples collected from a sewage treatment plant, and then used for the adsorption of heavy metals. We used two-dimensional correlation spectroscopy (2D-COS) integrated with Fourier-transform infrared spectroscopy (FTIR) to explore the adsorption between sludge HA (HA) and three metal ions (Cu, Ni, and Pb). The resulting adsorbing data conformed to the isotherm of Langmuir adsorption. The maximum capacity values (qm) were 5.34, 1.49, and 26.29.8 mg/g for Cu, Ni, and Pb, respectively. The data from 2D-FTIR-COS analysis showed that the susceptibility of the functional group followed the order 2300 → 1130 → 1330 → 1480 → 1580 cm-1 for Cu(II) and Ni(II), and 2300 → 1130 → 1330 → 1480 → 1200 → 1580 cm-1 for Pb(II). The sludge HA with Pb(II) showed more adsorption sites than sludge HA with Cu(II) and Ni(II), and these adsorption sites could preferentially bond with Pb(II) at × 1 compared with Cu(II) and Ni(II). Our findings indicate that 2D-FTIR-COS technology has great potential for application as a useful tool for understanding the adsorption mechanism between adsorbents with heavy metals.

Insight into the binding properties of carbamazepine onto dissolved organic matter using spectroscopic techniques during grassy swale treatment.

Carbamazepine (CBZ) is a worldwide anti-epileptic drug, whose fate and migration can be greatly influenced by contact with dissolved organic matter (DOM). The properties of DOM in road runoff can be greatly changed by grassy swale (GS) treatment, which influences the complexation of CBZ with DOM. Spectroscopic techniques were employed to explore the different binding properties between CBZ and DOM, and to understand the migration and biogeochemistry of CBZ. The two-dimensional correlation spectroscopy (2D-COS)demonstrated that effluent DOM displayed more binding sites for CBZ than influent DOM, and the binding sequencing of CBZ with DOM fluorophores can be greatly influenced by GS treatment. The results also suggest that protein-like materials exhibit higher log KM values than other fluorescent components, indicating that fluorescent protein-like materials play a crucial role in the biogeochemical behavior of CBZ. Meanwhile, the log KM values showed a remarkable increase after GS treatment. GS treatment can also remove most fluorescent DOM, reducing the risk of CBZ in the water environment.

Insights into the pollutant-removal performance and DOM characteristics of stormwater runoff during grassy-swales treatment.

The water purification performance of grassy swales for treating stormwater road runoff was evaluated using a simulated experimental device in two different seasons. The results showed that the removal rates for total suspended solids (TSS), chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) reached 89.90%, 56.71%, 32.37%, and 19.67%, respectively, in summer, and 34.09%, 7.75%, 56.71%, and 13.33%, respectively, in winter, suggesting that grassy swales showed higher water purification performance in summer than in winter. Soil filtration in grassy swales also showed high removal rates of TSS, COD, TN and TP in summer (98.13%, 59.10%, 33.82%, and 24.59% respectively). The structure, composition and source of dissolved organic matter (DOM) were investigated using ultraviolet visible (UV-Vis) spectra and fluorescence spectra. The spectral parameters indicated a relatively high humification and aromaticity of DOM, and a relatively higher contribution of organic matter derived from microbial substances in summer than in winter. In addition, grassy-swale treatment showed a slight decrease in metal-ion concentrations at the surface, while the removal rates in the bottom samples were 38.42%, 40.59%, 33.81%, and 40.06% for Cu2+, Cd2+, Pb2+, and Zn2+, respectively. The results of 2D-COS suggested that grass swales treatment can change the binding sites and binding sequencing of DOM with heavy metals and further influence the metal speciation, mobility and biotoxicity.

The binding properties of copper and lead onto compost-derived DOM using Fourier-transform infrared, UV-vis and fluorescence spectra combined with two-dimensional correlation analysis.

Three dissolved organic matter (DOM) samples were obtained from municipal solid wastes at the initial (C0), high-temperature (C7) and mature (C51) period during composting. Two-dimensional correlation spectroscopy (2D-COS) analysis on Fourier-transform infrared (FTIR), ultraviolet visible (UV-vis), and synchronous fluorescence spectra (SFS) were used to investigate the metal binding properties of compost-derived DOM. Synchronous and asynchronous maps of 2D-FTIR-COS of DOM-Cu(II) and DOM-Pb(II) were similar, however, the susceptibility and binding sequence of the corresponding spectral region was different. The N-H (amide I), phenolic OH, and C-O of alcohols, ethers, and esters were the most susceptive in the C0, C7, and C51 samples, respectively. 2D absorption COS indicated that the preferential binding with Cu(II) was shown to be at 305 nm for C0, at 236 nm for C7 and C51, and with Pb(II) at 247 nm for C0, at 233 nm for C7 and C51. 2D-SFS-COS indicated that protein-like matter showed a higher susceptibility and preferential binding with Cu(II) than humic-like substances. DOM showed a higher complexing affinity with Cu(II) than Pb(II) on the basis of the log K values. Spectral techniques combined with 2D-COS are useful to understand the binding heterogeneities of ligand sites within DOM-Cu(II) or Pb(II) during the composting.

Characteristic contaminants in snowpack and snowmelt surface runoff from different functional areas in Beijing, China.

Characteristics of physicochemical parameters, dissolved-phase heavy metals, and polycyclic aromatic hydrocarbons (PAHs) were investigated for 68 urban snowmelt surface runoff and snowpack samples collected from five different functional areas in Beijing, including a business area (BA), a cultural and educational area (CEA), a garden area (GA), a residential area (RA), and a roadside area (RSA). Both snowmelt surface runoff and snowpack were significantly polluted by organic matter, as indicated by their high concentrations of chemical oxygen demand (COD) and total organic carbon (TOC). Among the 11 heavy metals analyzed, Zn was the most enriched in all samples, followed by Mn, Fe, and Cu, whereas the concentrations of Pb, Cr, Cd, As, Ni, Sb, and Co were comparatively low. The results suggested that typical traffic emissions, natural events, industrial practices, and human activities were mainly sources of heavy metals. Low molecular-weight (LMW) PAHs were the dominant sources in snowmelt and snowpack. Anthracene (Ant) and fluorene (Flo) were the most enriched PAHs in both snowmelt surface runoff and snowpack. Coal burning for heating and traffic activities were the most important contributors of PAH pollutants in snowmelt surface runoff and snowpack in Beijing in the winter. Ecological risk assessment demonstrated, however, that heavy metals in snowmelt surface runoff pose little risk to downstream aquatic environments. A middle potential ecological risk could be caused by Ant, Flo, benzo[g, h, i]perylene (BghiP), and benzo[a]pyrene (BaA).

Characterization of dissolved organic matter from biogas residue composting using spectroscopic techniques.

Dissolved organic matter (DOM) extracted from composting of biogas residue was characterized using spectroscopic techniques. Spectral parameters, specific UV absorbance at 254 (SUVA254), ratios of spectral slopes (SR), and humification index (HIX) were used to assess the structural characteristics of the DOM. During composting, the UV absorbance at 254 increased as the relatively resistant aromatic fraction was released and the DOM molecular weight increased with the degree of humification. Fluorescence excitation-emission matrix (EEM) spectra with regional integration analysis (FRI) and accumulative fluorescence emission (AFE) combined with second derivative spectroscopy were used to assess the evolution of the DOM and evaluate the production of resistant humic-like substances during composting. Second derivative spectroscopy showed that microbial-derived humic-like substance A2 was easily degraded during composting. Two-dimensional correlation spectroscopy (2D-COS) combined with Fourier-transform infrared (FTIR) spectroscopy determined the preferential change sequence of the functional groups was 2000-2300 (CC or CN) → 1288 cm-1 (amide III) at x1 and 2935 (aliphatic groups) → 1420 (carboxylic groups) → 3100-3400 (hydroxyl groups) → 1660 cm-1 (aromatic CC) at x2, suggesting that functional groups of CC or CN, and amide III can be degraded preferentially, and aromatic CC groups were difficultly degraded. The present study showed spectroscopic techniques are valuable tools for assessing composting of biogas residues.

Tracking variations of fluorescent dissolved organic matter during wastewater treatment by accumulative fluorescence emission spectroscopy combined with principal component, second derivative and canonical correlation analyses.

Accumulative fluorescence emission (AFE) spectroscopy combined with principal component analysis (PCA), second derivative and canonical correlation analysis (CCA) was firstly developed into an available tool to track variations in dissolved organic matter (DOM) fractions and contents during wastewater treatment. Samples were collected from a wastewater treatment plant with a traditional anaerobic/anoxic/oxic (A2O) process. The AFE spectroscopy deduced from the sum of intensities along the excitation wavelengths of fluorescence excitation emission matrix (EEM), could distinctly track tyrosine-like, tryptophan-like, fulvic-like substances. The AFE spectroscopy with the PCA not only disaggregated DOM fractions into the tyrosine-like, tryptophan-like, microbial humic-like, fulvic-like and humic-like substances, but discriminated DOM fractions from the physical sedimentation, anaerobic/anoxic and oxic processes. Absolute areas of fluorescence components obtained by the second derivative AFF spectra had positive liner correlations with Fmax of the relevant components modeling from EEM-PARAFAC, especially the tryptophan-like (R2 = 0.95, p < 0.01) and tyrosine-like (R2 = 0.83, p < 0.01) substances. The CCA of the sites presented that the potential factors contained the tryptophan-like and tyrosine-like substances. This indirectly proved that the tryptophan-like and tyrosine-like substances were the dominant components of fluorescent DOM, which were further removed in A2O than the other fluorescent components. The CCA of the fluorescent components exhibited that the potential factors included the sites #1 to #6, which were located in the original wastewater, sand setting, primary sedimentation, anaerobic, anoxic, facultative units. This elaborated that the fluorescent components were mainly degraded in the physical sedimentation, anaerobic and anoxic processes.

Experimental and visual research on the microbial induced carbonate precipitation by Pseudomonas aeruginosa.

Microbial induced carbonate precipitation (MICP) is a common occurrence of geochemistry influences in many fields, such as biological, geographical, and engineering systems. However, the processes that control interactions between carbonate biomineralization and biofilm properties are poorly understood. We develop a method for real time, in situ and nondestructive imaging with confocal scanning microscopy. This method provides a possible way to observe biomineralization process and the morphology of biomineralized deposits within biofilms. We use this method to show calcite biominerals produced by Pseudomonas aeruginosa biofilms which extremely change biofilm structures. The distribution of calcite precipitation produced in situ biomineralization is highly heterogeneous in biofilms and also to occur primarily on the bottom of biofilms. It is distinct from those usual expectations that mineral started to precipitate from surface of biofilm. Our results reveal that biomineralization plays a comprehensive regulation function on biofilm architecture and properties.