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Zhu H.,Southwest University | Zhao X.,Key Laboratory of Agricultural Resources and Environment of Chongqing
Advanced Materials Research | Year: 2012

A pot experiment was performed to study effects of application of metal rich sludge cocomposted with lime on soil physicochemical properties, ryegrass biomass and heavy metal uptake by ryegrass. The results show that application of sludge compost with(LSC) and without lime(SC) could increase the soil pH, and the organic matter, available N, P and K in soils, consequently, improve the growth of ryegrass. No significant differences were found in the plant growth between sludge composted with lime and without lime. Sludge compost rich in Zn and Cd resulted in two elementals accumulation in soil and plant. The content of Zn and Cd in ryegrass from LSC-treated soil was much lower than those from SC-treated soils at the same application rate. The results illustrated that lime was very effective in stabilizing Zn and Cd in compost. However, the fact that Cd in ryegrass from LSC treated soil was close to or even exceeded the guideline for the health standard of feed and food in China(GB 13078-2001) implied the limitation of liming in stabilization heavy metals in sludge. Source


Wang S.,Southwest University | Luo S.,Southwest University | Li G.,Southwest University | Zhao X.,Southwest University | Zhao X.,Key Laboratory of Agricultural Resources and Environment of Chongqing
Huanjing Kexue Xuebao/Acta Scientiae Circumstantiae | Year: 2011

The effect of anionic polyacrylamide (PAM) with different molecular weight (MW) and hydrolysis degree (HD) on the settleability and dewaterability of sewage sludge was evaluated by determining the particle size distribution, specific filtration resistance and cake solid content of flocculated sludge as well as the supernatant volume, and concentrations of DNA, protein and sugar in the supernatant of sewage sludge. Addition of anionic PAM increased the percentage of particles with diameter greater than 0.60 mm, while it decreased the percentage of particles with diameter less than 0.25 mm. The increase in the HD of PAM with the same MW led to a rise of the supernatant volume, but a decline in the specific filtration resistance. For PAM with the same HD, the supernatant volume increased with the MW from 6 to 8 MDa, but decreased with a further increase of MW to 12 MDa. The response of specific filtration resistance to the MW of anionic PAM was opposite to that of supernatant volume. The effective application dosage of PAM for optimal settleability and dewaterability varied with the type of PAM. The optimal settleability and dewaterability were obtained at 75 mg·L-1 for PAM with MW of 6 MDa and HD of 30%, and for the PAM with MW of 8 MDa and HD of 20%. It was also found that both the elevated HD of anionic PAM with the same MW and the elevated MW of anionic PAM with the same HD could induce an increasing concentration of protein and sugar in the supernatant of sewage sludge, implying that the release of extracellular polymeric substance (EPS) from the sludge surface was one of the main reasons for the improvement of settleability and dewaterability associated with PAM addition. Source


Shi Q.-B.,Southwest University | Zhao X.-L.,Southwest University | Zhao X.-L.,Key Laboratory of Agricultural Resources and Environment of Chongqing | Chang T.-J.,Southwest University | Lu J.-W.,Chongqing Dianjiang Environmental Protection Monitoring Station
Huanjing Kexue/Environmental Science | Year: 2016

A long-term experiment was utilized to study the effects of tillage methods on the contents and distribution characteristics of organic matter and heavy metals (Cu, Zn, Pb, Cd, Fe and Mn)in aggregates with different sizes (including 1-2, 0.25-1, 0.05-0.25 mm and <0.05 mm)in a purple paddy soil under two tillage methods including flooded paddy field (FPF) and paddy-upland rotation (PR). The relationship between heavy metals and organic matter in soil aggregates was also analyzed. The results showed that the aggregates of two tillage methods were dominated by 0.05-0.25 mm and<0.05 mm particle size, respectively. The contents of organic matter in each aggregate decreased with the decrease of aggregate sizes, however, compared to PR, FPF could significantly increase the contents of organic matter in soils and aggregates. The tillage methods did not significantly affect the contents of heavy metals in soils, but FPF could enhance the accumulation and distribution of aggregate, organic matter and heavy metals in aggregates with diameters of 1-2 mm and 0.25-1 mm. Correlation analysis found that there was a negative correlation between the contents of heavy metals and organic matter in soil aggregates, but a positive correlation between the amounts of heavy metal and organic matter accumulated in soil aggregates. From the slope of the correlation analysis equations, we could found that the sensitivities of heavy metals to the changes of soil organic matters followed the order of Mn>Zn>Pb>Cu>Fe>Cd under the same tillage. When it came to the same heavy metal, it was more sensitive in PR than in FPF. © 2016, Science Press. All right reserved. Source


Zhang M.-H.,Southwest University | Zhang M.-H.,Key Laboratory of Agricultural Resources and Environment of Chongqing | Lu J.-W.,Chongqing Dianjiang Environmental Protection Monitoring Station | Zhao X.-L.,Southwest University | Zhao X.-L.,Key Laboratory of Agricultural Resources and Environment of Chongqing
Huanjing Kexue/Environmental Science | Year: 2016

An aerobic incubation experiment was conducted at a constant temperature to investigate the differences in nitrogen mineralization between an acid purple soil and a calcareous purple soil amended with five organic materials including biogas residues of pig manure(PM), cow manure(CW), sewage sludge compost(SC), rural waste compost(RWC1)and the compost of rural waste plus 20% of sewage sludge(RWC2). The results showed that the organic nitrogen forms in these materials followed the order of amino acid N>hydrolysable unidentified N>ammonium N>non-hydrolysable N>amino sugar N. Application of organic materials could significantly improve the contents of NH4 +-N and NO3 --N in acid purple soil, PM and SC could significantly improve the content of NH4 +-N, but CM reduced the content of NO3 --N in calcareous purple soil. Except for CM, which had no significant effect on the quantity of nitrogen mineralization in acid purple soil, but decreased the quantity of nitrogen mineralization in calcareous purple soil, applying the organic materials could significantly increase the quantity of nitrogen mineralization in both soils. Correlation analysis showed that the quantity of nitrogen mineralization was significantly and positively correlated with the contents of amino acid N and ammonium N, but were significantly and negatively correlated with the content of organic matter and the C/N of organic materials. Overall, the results illustrated that the effect of organic materials on the mineralization of nitrogen varied with soil types and the characteristics of organic materials, especially the content of organic matter, C/N and the fractions of organic nitrogen in organic materials. © 2016, Science Press. All right reserved. Source


Wang F.,Southwest University | Wang Q.,Southwest University | Wang Q.,Key Laboratory of Agricultural Resources and Environment of Chongqing | Mu Z.-J.,Southwest University | And 3 more authors.
Huanjing Kexue/Environmental Science | Year: 2015

Phthalic acid esters (PAEs) have received increasing attention in recent years due to their widespread use and hazards to human health and fertility in the environment. In order to understand the migration and release processes of organic pollutants in huge fluctuating zone soil, Dibutyl-phthalate (DBP) was chosen as a typical substance, and its migration and release characteristics in the fluctuating zone of the Three Gorges Reservoir to overlying water and the impacts of DBP concentration in the soil, ionic strength and the concentration of organic mater in overlying water on the process were studied using static flooding method. The results showed that DBP migrated from the soil to the overlying water in the early days after flooding, and the release process of DBP was divided into two phases: one was quick release with a relatively short releasing time and a rapid releasing rate; the other was slow release with a relatively long releasing time and a slow releasing rate. The migration and release processes were well fitted by two-compartment first-order kinetics. After different concentrations DBP were added into soil, the rate of quick release increased with the increasing DBP concentrations in soil while the percent of quick release decreased with the increasing DBP concentrations. The results of rate of slow release and the percent of slow release were on the contrary. The water conditions of overlying water could impact the migration and releasing process of DBP when the soil in fluctuating zone was flooded. The amount of DBP released into the overlying water would increase when the ionic strength in the water increased. At the same time, when the ionic strength increased, in spite of the decreasing quick release rate, the percent of quick release increased. The higher concentration of organic matter in overlying water, the more the amount of DBP released into the overlying water. At the same time, all of the rates of quick release, slow release and the percent of quick release would increase with the increasing concentrations of organic matter, while there was almost no influence on the percent of slow release of DBP. ©, 2015, Science Press. All right reserved. Source

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