Solid components and acid buffering capacity of soils in South China

The effects of soil solid components on soil sensitivity to acid deposition by sequential extraction method were studied. A multiple regression equation of soil sensitivity was set up on the basis of stepwise regression analysis. The results showed that organic matter expressed dual effects that were decided by soil original pH value and exchangeable cation composition on acid buffering reactions. The hydrolysis of activated oxides was a very important proton buffering reaction when in low pH situation. The crystalline oxides also played a role in the buffering reactions, but the role was restricted by the rate of activation of oxides. Meanwhile, the results by stepwise analysis showed that factors that had significant effect on soil acid buffering capacity were content of montmorillite, soil original pH value, Al 0, Mn 0 and CEC in decreasing order. Finally, sixteen soils were classified into four types of sensitive with single index cluster and multiple fuzzy cluster analysis respectively.

A new combined criterion to better predict malignant lesions in patients with pancreatic cystic neoplasms

Objective:Cystic lesions of the pancreas have been increasingly recognized.Some lesions exhibit benign behavior,while others have unequivocal malignant potential.Thus,accurate identification of malignancy in patients diagnosed with pancreatic cystic neoplasms(PCNs)remains a major challenge.The aim of this study was to define a combined criterion to better predict malignant lesions in patients with PCNs.Methods:We retrospectively analyzed 165 patients who underwent resection of PCNs from October 2011 to May 2017.The relationship among malignancy and serum carbohydrate antigen 19-9(CA19-9),preoperative neutrophil-to-lymphocyte ratio(NLR),and the presence of enhanced solid component on imaging was analyzed.Results:NLR before surgery in patients with malignant PCNs(2.81±2.14)was significantly higher than that in patients diagnosed with pancreatic neuroendocrine tumor(1.90±0.69,P=0.013)or healthy volunteers(1.40±0.48;P<0.001).Serum CA19-9≥39U/m L,NLR>1.976 and presence of enhanced solid component were independent predictors of PCN malignancy.A combined criterion meeting any two or more of the three elements including CA19-9≥39 U/m L,NLR>1.976,and presence of enhanced solid component on computed tomography imaging is an indicator with a high positive predictive value of 80.5%and a high negative predictive value of 87.9%,and thus,represents a highly accurate test(86.1%).Conclusions:The new combined criterion is an effective predictor of tumor malignancy in patients with PCNs.

Occurrence,distribution,and potential influencing factors of sewage sludge components derived from nine full-scale wastewater treatment plants of Beijing,China

Millions of tons of waste activated sludge（WAS） produced from biological wastewater treatment processes cause severe adverse environmental consequences. A better understanding of WAS composition is thus very critical for sustainable sludge management. In this work, the occurrence and distribution of several fundamental sludge constituents were explored in WAS samples from nine full-scale wastewater treatment plants（WWTPs） of Beijing, China. Among all the components investigated, active heterotrophic biomass was dominant in the samples（up to 9478 mg/L）, followed by endogenous residues（6736 mg/L）,extracellular polymeric substances（2088 mg/L）, and intracellular storage products（464 mg/L）among others. Moreover, significant differences（p 〈 0.05） were observed in composition profiles of sludge samples among the studied WWTPs. To identify the potential parameters affecting the variable fractions of sludge components, wastewater source as well as design and operational parameters of WWTPs were studied using statistical methods. The findings indicated that the component fraction of sewage sludge depends more on wastewater treatment alternatives than on wastewater characteristics among other parameters. A principal component analysis was conducted, which further indicated that there was a greater proportion of residual inert biomass in the sludge produced by the combined system of the conventional anaerobic/anoxic/oxic process and a membrane bioreactor. Additionally, a much longer solids retention time was also found to influence the sludge composition and induce an increase in both endogenous inert residues and extracellular polymeric substances in the sludge.

Use of gamma-irradiation pretreatment for enhancement of anaerobic digestibility of sewage sludge

The effects of γ-irradiation pretreatment on anaerobic digestibility of sewage sludge was investigated in this paper.Parameters like solid components,soluble components,and biogas production of anaerobic digestion experiment for sewage sludge were measured.The values of these parameters were compared before and after γ-irradiation pretreatment.Total solid(TS),volatile solid(VS),suspended solid(SS),volatile suspended solid(VSS),and average floc size of samples decreased after cirradiation treatment.Besides,floc size distribution of sewage sludge shifted from 80–100 mm to 0–40 mm after γ-irradiation treatment at the doses from 0 to 30 kGy,which indicated the disintegration of sewage sludge.Moreover,microbe cells of sewage sludge were ruptured by γ-irradiation treatment,which resulted in the release of cytoplasm and increase of soluble chemical oxygen demand(SCOD).Both sludge disintegration and microbe cells rupture enhanced the subsequent anaerobic digestion process,which was demonstrated by the increase of accumulated biogas production.Compared with digesters fed with none irradiated sludge,the accumulated biogas production increased 44,98,and 178 mL for digesters fed sludge irradiated at 2.48,6.51,and 11.24 kGy,respectively.The results indicated that γ-irradiation pretreatment could effectively enhance anaerobic digestibility of sewage sludge,and correspondingly,could accelerate hydrolysis process,shorten sludge retention time of sludge anaerobic digestion process.