[Characterizing Dissolved Organic Matter (DOM) in Wastewater from Scale Pig Farms Using Three-Dimensional Excitation-Emission Matrices (3DEEM].

The properties of material composition in swine wastewater are closely related to its potential environmental effects, and it could provide theoretical bases for formulating scientific resource management measures to study the composition of organic matter in wastewater. In the present study, swine wastewater was directly collected from waste-retention basins in various scale pig farms with a different farming scale (based on the annual pig slaughter), namely Cheng Lin (CL, 5 000), Wu Yang-gao (WYG, 2 000), Wan Gu (WG, 20 000), and Zhang Bang (ZB, 24 000), located in Yujiang County of Jiangxi Province. The main purpose of this study was to characterize dissolved organic matter (DOM) in swine wastewater using three-dimensional excitation-emission matrices (3DEEM) and parallel factor analysis (PARAFAC). Results of all samples examined showed, with respect to CL and WYG farm, chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH+4), and dissolved organic carbon (DOC) concentration in swine wastewater was significantly higher than WG and ZB farm. Three DOM components, including two protein-like components (C1, C2) and one humic-like component (C3), were identified in wastewater using 3DEEM and PARAFAC. Results of linear regression showed, the fluorescence intensity of C1 linked significantly with C2 (p<0.001) and C3 (p<0.001), respectively, suggesting a same source or similar variation trend existed possibly between different DOM components. Furthermore, consistent with the variation trend of nutrient concentration in wastewater, fluorescence intensity of each DOM component in CL and WYG farm was significantly higher than WG and ZB farm. The total contribution of C1 and C2 to DOM in swine wastewater was CL (89.7%), WG (77.5%), WYG (87.9%), and ZB (72.9%), respectively, and the percentage of C3 was CL (10.3%), WG (22.5%), WYG (12.1%), and ZB (27.1%), respectively. Thus, the percentage of two protein-like components was significantly higher than humic-like in swine wastewater. Meanwhile, the fluorescence indices FI370 and humification index (HIX) of WG and ZB farm were higher than CL and WYG. In addition, Pearson correlation analysis showed that the effects of environmental parameters on fluorescence indices were different, and COD and DOC concentrations were significantly correlated with the fluorescence intensities of DOM components in swine wastewater. In summary, to a certain degree, the nutrient levels affected formation of fluorescence characteristics and DOM compositions in swine wastewater between different scale pig farms.

[Structural Analysis of Organic Matter Composition in Piggery Wastewater during the Process of Organic Degradation Based on FTIR Spectroscopy].

More and more attentions were paid on the environmental pollutions of wastewater discharged from scale pig farms, and it could provide scientific bases for formulating reasonable pollution control measures to study the structural changes of organic matter composition in piggery wastewater. In the present study, a laboratory-scale incubation experiment was carried out with piggery wastewater collected from different scale pig farms, and a continuous sampling was conducted at a certain interval during the process of incubation experiment. The main purpose of this study was to elucidate the change of structural composition of dissolved organic matter (DOM) in piggery wastewater during the process of organic degradation. All dried and solid DOM samples were achieved using filtration and freeze-drying methods. Spectral analysis of all DOM samples was completed with the application of Fourier transform infrared (FTIR) spectrometer. Results of spectral analysis showed a similar DOM structural composition was observed in the wastewater derived from different scale pig farms, and was mainly comprised of lipids, proteins, fulvic acids, polysaccharides, and phenolic compounds. With the increase in the incubation days, the percent of functional groups, related to proteins, phenolic acids, and lipids, decreased gradually and kept stable eventually, while these functional groups, linked with fulvic acids and polysaccharides, showed a significant increase and leveled off at the end. Compared with primary samples, fulvic acids and polysaccharides were the predominant fractions of DOM at 20 days after organic degradation, indicating a higher aromatic degree of DOM. Meanwhile, the degradation rate of OH bonded by intermolecular H-bond of cellulose was faster than OH bonded by intra-molecular H-bond of cellulose, whereas the latter was more sensitive to microbial degradation. The degradation rate of phenolic hydroxyl C­O was the fastest, followed by aromatic COOH, carbohydrate C­O, and amide CO. Furthermore, the carbohydrate C­O was apt to be utilized preferentially by microorganisms. In sum, the structural change of various DOM in piggery wastewater was different during the process of organic degradation.

Soil microbiome-induced changes in the priming effects of 13C-labelled substrates from rice residues.

Knowledge gap exists to understand the soil CO2 emission and microbial group response to substrates of whole plant residues and derived biochar. We used 13C-labelled substrates (rice straw, roots and biochar) to track influences of their decomposition on soil priming effect (PE) and phospholipid fatty acid (PLFA) composition during one-year incubation. Organic substrates at 1% (w/w) level increased soil pH, available nitrogen (AN) and available phosphorus (AP), especially during the first 45 days of incubation. After incubation, 44% of the added straw was mineralized to 13CO2, followed by roots (~35%) and biochar (~5%). Straw and roots amendment caused positive PE during 4-360 day of the incubation, where a lowest value of 41.9 mg C kg-1 was observed. Biochar amendment caused negative PE during 56-150 day of the incubation, where a largest value of -99.0 mg C kg-1 was observed. Analysis of 13C-labelled PLFA enabled the differentiation of microbial groups during substrates utilization. Gram positive bacteria (G+) and general bacteria groups were dominated in co-metabolizing both the native soil organic carbon (SOC) and substrates after straw and roots amendment. Gram negative bacteria (G-), especially identified by PLFA biomarkers cy17:0 and cy19:0, preferentially utilizes the 13C-labelled biochar but not promoting soil priming effect. Soil pH, SOC, AN and AP all explained changes of total and 13C-labelled PLFA contents (>75%, p < .05). Evidences showed that biochar is best in sequestering soil C pool, followed by straw and roots, and soil microbial groups in utilization of organic substances mediated SOC mineralization.

Soil CO2 flux in relation to dissolved organic carbon, soil temperature and moisture in a subtropical arable soil of China.

Soil CO2 emission from an arable soil was measured by closed chamber method to quantify year-round soil flux and to develop an equation to predict flux using soil temperature, dissolved organic carbon(DOC) and soil moisture content. Soil CO2 flux, soil temperature, DOC and soil moisture content were determined on selected days during the experiment from August 1999 to July 2000, at the Ecological Station of Red Soil, the Chinese Academy of Sciences, in a subtropical region of China. Soil CO2 fluxes were generally higher in summer and autumn than in winter and spring, and had a seasonal pattern more similar to soil temperature and DOC than soil moisture. The estimation was 2.23 kgCO2/(m2 x a) for average annual soil CO2 flux. Regressed separately, the reasons for soil flux variability were 86.6% from soil temperature, 58.8% from DOC, and 26.3% from soil moisture, respectively. Regressed jointly, a multiple equation was developed by the above three variables that explained approximately 85.2% of the flux variance, however by stepwise regression, soil temperature was the dominant affecting soil flux. Based on the exponential equation developed from soil temperature, the predicted annual flux was 2.49 kgCO2/(m2 x a), and essentially equal to the measured one. It is suggested the exponential relationship between soil flux and soil temperature could be used for accurately predicting soil CO2 flux from arable soil in subtropical regions of China.

[Translocation and transformation characteristics of fertilizer nitrogen in paddy soil: a study with simulated soil column].

Aimed to understand the translocation and transformation characteristics of applied fertilizer nitrogen in paddy soil, a simulated soil column experiment was conducted in laboratory to study the variations of soil mineral nitrogen along the profile under the application of 360 mg x kg(-1) (3 folds of conventional application rate) of urea- and ammonium sulfate nitrogen. In the experimental period, the soil NH4(+)-N and NO3(-)-N contents in the control (no fertilization) had less change, and no significant differences among different soil layers. Applying urea- and ammonium sulfate nitrogen resulted in a significant increase of soil NH4(+)-N and NO3(-)-N in 0-50 mm layer, being 186.0-2882.1 mg x kg(-1) and 268.7-351.5 mg x kg(-1), and 4.8-242 times and 5.7-316 times of those in CK, respectively. However, the NH4(+)-N and NO3(-)-N contents below 50 mm soil depth were similar to those in CK, indicating that the translocation and transformation of applied fertilizer nitrogen mainly occurred in 0-50 mm soil layer. The translocation of fertilizer nitrogen mostly occurred in the first 14 days after fertilization. In the whole experimental period, the NH4(+)-N and NO3(-)-N contents in each soil layer under the application of ammonium sulfate were 0.7-2.0 times of those under the application of urea, and the nitrification rate was 0.9-1.4 times of that, suggesting the higher transformation rate of applied ammonium sulfate in paddy soil, as compared with applied urea.

[Influences of humic acids on the dissimilatory iron reduction of red soil in anaerobic condition].

Iron oxide is abundant in red soil. Reduction and oxidation of iron oxide are important biogeochemical processes. In this paper, we reported the effects of humic acid on dissimilatory iron reduction (DISSIR) in red soil by adding glucose or humic acid (HA), under an anaerobic condition. Results indicated that DISSIR is weak for the red soil with a low content of organic matter, Glucose that act as electron donators promoted the process of DISSIR in red soil. HA added to soil solely didn't accelerate the DISSIR since it couldn't provide electron donators to microbe. However, adding of both glucose and HA promoted the DISSIR at the beginning of the incubation but then inhibited the process, which maybe caused by the effects of precipitation and adsorption of red soil. Concentrations of HA strongly affected the DISSIR, HA at low concentrations(0.20 and 0.02 g/kg) had weak effects, while HA at a high concentration (2.00 g/kg) promoted the process at the beginning and then inhibited it. HA extracted from different materials had distinct effects on the DISSIR. HA from Weathering coal of Datong in Shanxi Province (HAs), lignite of Gongxian in Henan Province (HAh) and Dianchi Lake sediment in Kunming of Yunnan Province (HAk) all promoted the DISSIR at the beginning of the incubation. However, at the end of incubation, HAk with a low aromaticity still promoted the process, while HAs and HAh with a higher aromaticity weakened the DISSIR. This may be due to the increase in adsorption of soil with the aromaticity of HA.

[Temperature sensitivity of organic C mineralization in gray forest soils after land use conversion].

A laboratory incubation test was conducted to study the organic C mineralization in gray forest soils after land use conversion and the temperature sensitivity of the mineralization. It was shown that after the conversion from wildwood land to farmland, the organic C and total N contents in 0-10 cm and 10-20 cm soil layers decreased by 68.5% and 76.8%, and 40.5% and 44.4%, and the average mineralization rate and cumulative mineralization of soil organic C in farmland were 24.4%-43.2% and 9.20%-13.7% of those in wildwood land, respectively. At lower temperature (< 25 degrees C), there was no significant difference in the temperature sensitivity of soil organic C mineralization between the two land use types; while at higher temperature ( > 25 degrees C), this temperature sensitivity in farmland soil was higher in 0-10 cm layer but significantly lower in 10-20 cm layer, compared with that in wildwood land soil.

[Effect of long-term fertilization on dissipation of pentachlorophenol in red paddy field].

Dissipation of pentachlorophenol (PCP) with initial concentration of 85 mg/kg in red paddy field with rice cultivation and non-rice cultivation were investigated under the conditions of four long-term fertilization treatments, including the ones without fertilizer (CK), application of urea (N), application of organic fertilizer (OM), and N + OM. The results showed that the extractable PCP residues in surface soil in the treatments CK, N, OM and N + OM under non-rice cultivation condition were 28.3, 34.2, 19.3, 18.7 mg/kg after harvesting rice plant, and the extractable PCP residues in subsurface soil were 6.3, 9.1, 5.1, 4.1 mg/kg,respectively. Under rice cultivation condition, the extractable PCP residues in surface soil were 19.4, 30.9, 16.7, 8.7 mg/kg, and the extractable PCP residues in subsurface soil were 3.7, 6.1, 2.6, 2.8 mg/kg, respectively. The results indicated that the long-term application of organic fertilizer or inorganic plus organic fertilizer significantly accelerated the dissipation of PCP in surface soil, and decreased the transportation of PCP down the soil profile. However, long-term application of urea inhibited the dissipation of PCP in surface soil, and increased the transportation of PCP down the soil profile. When compared with non-rice cultivation, rice cultivation significantly accelerated the dissipation of PCP in surface soil other than the treatment N. In addition,the rice cultivation significantly decreased the transportation of PCP down the soil profile. No matter rice was cultivated or not, the dechlorinated metabolites of PCP detected in paddy soil were 2,3,4,5-TeCP and 3,4,5-TCP. 2,3,4,5-TeCP was the major dechlorinated metabolite of PCP under non-rice cultivation condition,whereas 3,4,5-TCP was the major dechlorinated metabolite of PCP under rice cultivation condition.

[Effects of different types of litters on soil organic carbon mineralization].

Using litter incubation experiment in laboratory, decomposition discrepancies of four typical litters from Zijin Mountain were analyzed. The results show that organic carbon mineralization rates of soil with litters all involve fast and slow decomposition stages, and the differences are that the former has shorter duration,more daily decomposition quantity while the latter is opposite. Organic carbon mineralization rates of soil with litters rapidly reached maximum in the early days of incubation, and the order is soil with Cynodon dactylon litter (CK + BMD) (23.88 +/- 0.62) mg x d(-1), soil with Pinus massoniana litter (CK+ PML) (17.93 +/- 0.99) mg x d(-1), soil with Quercus acutissima litter (CK+ QAC) (15.39 +/- 0.16) mg x d(-1) and soil with Cyclobalanopsis glauca litter (CK + CGO) (7.26 +/- 0.34) mg x d(-1), and with significant difference between each other (p < 0.05). This order has not significant correlation to litter initial chemical elements. The amount of organic carbon mineralized accumulation within three months incubation is (CK + BMD) (338.21 +/- 6.99) mg, (CK + QAC) (323.48 +/- 13.68) mg, (CK + PML) (278.34 +/- 13.91) mg and (CK + CGO) (245.21 +/- 4.58) mg. 198.17-297.18 mg CO2-C are released during litter incubation, which occupies 20.29%-31.70% of the total litter organic carbon amounts. Power curve model can describe the trends of organic carbon mineralization rate and mineralized accumulation amount,which has a good correlation with their change.

[Effects of long-term fertilization on phospholipid fatty acids and enzyme activities in paddy red soil].

Soil samples were collected from the paddy fields at the Ecological Experimental Station of Red Soil, Chinese Academy of Sciences under different treatments of long-term fertilization, and their phospholipid fatty acids (PLFAs) and enzyme activities were determined. The results showed that soil enzyme activities, nutrient contents, microbial biomass, and PLFAs varied greatly with different fertilizations. Fertilization increased the kinds and amount of soil PLFAs. Compared with fertilized soil, unfertilized soil had more fungal PLFAs but less bacterial PLFAs, indicating that fungus was more adaptable to infertile soils than bacteria. Soils applied with NPK and organic fertilizer had higher amount of total PLFAs, which was 3.22 and 1.79 times higher than that under N fertilization and no fertilization. It was indicated that balanced fertilization with NPK or applying organic fertilizer was more beneficial to the growth of plants. Fertilization could also increase soil enzyme activities, and soil urease and phosphatase activities could be used as the indicators of soil fertility.

[Organic carbon mineralization in various size aggregates of paddy soil under aerobic and submerged conditions].

With incubation tests in laboratory, the mineralization of organic carbon in various size aggregates of paddy soil was investigated under aerobic and submerged conditions. The results showed that the organic carbon mineralization in various size aggregates decreased quickly at the beginning of the incubation, but remained stable during the late period of incubation. The mineralization rate varied significantly with the size of the aggregates. Through the incubation time, the organic carbon in 1-2 mm aggregates had the highest mineralization rate, while that in < 0.053 mm aggregates had the lowest one. Statistic analyses indicated that the mineralization rate of organic carbon in various size aggregates was significantly and linearly correlated with the contents of organic carbon and microbial biomass carbon in the aggregates. 0.25-1 mm aggregates had the highest contribution to the cumulative mineralization of soil organic carbon, accounting for 41.77% under aerobic condition and 34.11% under submerged condition, while < 0.053 mm and 1-2 mm aggregates had the lowest contribution under aerobic and submerged conditions, accounting for 7.8% and 6.6%, respectively.

Pathways and kinetics of redistribution of cobalt among solid-phase fractions in arid-zone soils under saturated regime.

An adequate supply of Co in pasture is important to the health of grazing animals. Bio-availability of Co in soils is largely depended upon its distribution among solid-phase fractions. Distribution of cobalt in six arid-zone soils and its redistribution among the solid-phase fractions during long-term saturated paste incubation were studied. Cobalt was fractionated by a selective sequential dissolution procedure into six empirically defined fractions. Concentrations of total Co and Mn or Fe, and Co and Mn fractionation pattern were strongly correlated in the soils. During saturated incubation, Co in soils was redistributed mainly from the Mn oxide bound, and to some extent, Fe oxide bound and organic matter bound fractions into the carbonate bound fraction. During saturated incubation, significant correlations were found between concentrations of Co and Mn in the Mn oxide bound, Fe oxide bound and carbonate bound fractions. Also, significant correlations between concentrations of Co and Fe in the Fe oxide bound fraction were present. However, a negative correlation between concentrations of Co and Fe in the Mn oxide bound fraction was observed. The rates of redistribution of Co between these solid-phase components were initially high: major changes occurred in the first 3 days in the sandy soil and the first 18 days in the loessial soil. Afterwards, the rates of change slowed but changes in redistribution continued during the rest of the study period of one year.