聚丙烯酸钠作为调理剂对好氧堆肥的保氮影响

实验以污泥、锯末、猪粪为原料,以聚丙烯酸钠(PAAS)为调理剂,利用自制好氧堆肥反应器,研究了PAAS在污泥好氧堆肥中的保氮效果。实验显示,PAAS会提高堆体的pH水平,抑制氨氮的生成,从而减少NH3的挥发源,在PAAS对水溶性氨的吸附作用下,堆肥产品的最终氨氮水平依然得到提高;PAAS对硝化反应有一定的促进作用,添加PAAS的堆体在堆肥周期内的硝氮平均增幅可达到未添加PAAS的空白堆体的4.64倍;添加PAAS的堆体在堆肥周期内全氮平均降幅只有空白堆体的52.24%。PAAS做为堆肥调理剂起到了较为明显的保氮效果。     

A novel use of anaerobically digested liquid swine manure to potentially control soybean cyst nematode

Experiments were carried out in two steps to determine the effect of anaerobically digested swine manure on soybean cyst nematode (SCN) egg control. In the first step, liquid swine manure underwent anaerobic digestion to search for the best digestion time for both volatile fatty acids (VFA) and ammonium nitrogen (NH₄ ⁺) enrichment. The results showed that about 17 and 28 days of incubation were needed, respectively, to reach the maximal levels of VFA and NH₄ ⁺ in the manure. In the second step, raw, VFA-enriched, and NH₄ ⁺-enriched manure were applied separately, at four different rates (25, 50, 100, and 200 mL/pot), to soil pots inoculated with nematode eggs in a greenhouse environment. Soil samples were collected 35 and 61 days after inoculation to determine the effect of such treated manure on SCN egg productivity. The data indicated that the SCN egg counts were inversely related to the manure application rates in a linear manner with correlation coefficients of 0.998, 0.967, and 0.900 for raw, NH₄ ⁺-enriched, and VFA-enriched manure for the 35-day samples. While no such relationships were found for the 61-day samples, implying that none of the treatments were still effective 61 days after application. At the four application rates, the VFA-enriched manure performed best in reducing SCN egg counts (by 18.1, 19.5, 34.3, and 18.6%) as compared to the raw manure treatment. In contrast, the NH₄ ⁺-enriched manure achieved mostly negative reductions. To achieve the best control of SCN egg growth, the VFA-enriched manure should be used and applied to soybean fields every 35 days.     

Kinetics study of fermentative hydrogen production from liquid swine manure supplemented with glucose under controlled pH

Kinetics of H₂ production from liquid swine manure supplemented with glucose by mixed anaerobic cultures was investigated using batch experiments under four different pH conditions (4.4, 5.0, 5.6, and uncontrolled). The temperature for the experiments was controlled at 37 ± 1°C and the length of experiments varied between 50 and 120 hours, depending upon the time needed for completion of each individual experiment. The modified Gompertz model was evaluated for its suitability for describing the H₂ production potential, H₂ production rate, and substrate consumption rate for all the experiments. The results showed that the Gompertz model could adequately fit the experimental results. The effect of pH was significant on all kinetic parameters for H₂ production including yield, production rate and lag time, and the substrate utilization rate. The optimal pH was found to be 5.0, at which a maximum H₂ production rate (0.64 L H₂/h) was obtained, and deviation from the optimal pH could result in substantial reductions in H₂ production rate (0.32 L H₂/h for pH 4.0 and 0.43 L H₂/h for pH 5.6). The results also showed that if pH was not controlled for the batch fermentation process, the substrate utilization efficiency could steeply decrease from 98.8% to 33.7%.     

Influences of adding easily degradable organic waste on the minimization and humification of organic matter during straw composting

To find a better composting process with low greenhouse gas emission and high humus production, the effect of adding kitchen waste on reduction and humification of organic matter during straw composting was studied. Three processes were compared, consisting of different ratios of straw and kitchen waste (1:2, 1:1, and 2:1). At four time points over a 62-d incubation, the reduction and humification of compost was evaluated by measuring the total mass, carbon content, and humic material content of the compost. Treatment 1 (straw/kitchen waste ratio of 1:2) reduced the total mass of compost the most. Treatment 2 (straw/kitchen waste ratio of 1:1) reduced the total carbon content the most, reflecting the highest emission of greenhouse gas. Treatment 3 produced the most humic acid material and released the lowest amount of carbon. Hence, from the point of view of reducing greenhouse gas emissions and increasing stable organic matter such as humus and humic acid during composting, treatment #3 was optimal. The three treatments resulted in significant differences in microbial biomass and enzyme activity during composting. The highest amount of active microbial biomass was associated with the largest reduction in compost mass (treatment 1). Higher proportions of straw (treatments 2 and 3), which contains more lignin, were associated with greater β-glycosidase activity, which may generate more humus that can improve soil quality. Dehydrogenase activity seemed to be the most important microbial factor in organic carbon catabolism or humification.     

Chemical oxidation of sulfadiazine by the Fenton process: Kinetics,pathways, toxicity evaluation

This paper investigated sulfadiazine oxidation by the Fenton process under various reaction conditions. The reaction conditions tested in the experiments included the initial pH value of reaction solutions, and the dosages of ferrous ions and hydrogen peroxide. Under the reaction conditions with pH 3, 0.25 mM of ferrous ion and 2 mM of hydrogen peroxide, a removal efficiency of nearly 100% was achieved for sulfadiazine. A series of intermediate products including 4-OH-sulfadiazine/or 5-OH-sulfadiazine, 2-aminopyrimidine, sulfanilamide, formic acid, and oxalic acid were identified. Based on these products, the possible oxidation pathway of sulfadiazine by Fenton's reagent was proposed. The toxicity evaluation of reaction solutions showed increased antimicrobial effects following the Fenton oxidation process. The results from this study suggest that the Fenton oxidation process could remove sulfadiazine, but also increase solution toxicity due to the presence of more toxic products.     

树脂固定床吸附含酚废水预测模型研究

针对应用于实际工业化的树脂固定床吸附研究较少,而与之相关的固定床吸附穿透曲线可以用来确定固定床吸附操作参数,为固定床的设计和实际操作提供指导。通过对恒定波振荡理论和吸附等温方程的联合,来预测固定床吸附穿透曲线;并研究了不同操作条件对大孔弱碱树脂吸附对硝基酚穿透曲线预测模型的影响。以期望为树脂固定床的设计和实际工业应用产生指导意义。     

Distribution and bioavailability of ceria nanoparticles in an aquatic ecosystem model

Along with the increasing utilization of engineered nanoparticles, there is a growing concern for the potential environmental and health effects of exposure to these newly designed materials. Understanding the behavior of nanoparticles in the environment is a basic need. The present study aims to investigate the distribution and fate of ceria nanoparticles in an aquatic system model which consists of sediments, water, hornworts, fish and snails, using a radiotracer technique. Concentrations of ceria in the samples at regular time intervals were measured. Ceria nanoparticles were readily removed from the water column and partitioned between different organisms. Both snail and fish have fast absorption and clearance abilities. Hornwort has the highest bioaccumulation factors. At the end of the experiment, sediments accumulated most of the nanoparticles with a recovery of 75.7 ± 27.3% of total ceria nanoparticles, suggesting that sediments are major sinks of ceria nanoparticles.     

Harvesting of Chlorella sp. using hollow fiber ultrafiltration

Introduction

The suitability of the application of ultrafiltration (UF) to harvest Chlorella sp. from the culture medium was examined. We investigated the effects of two improved UF system, forward air?Cwater flushing and backwash with permeate, on the concentration process.

Materials and methods

Backwash with permeate was selected as an optimization of the improved UF system, which was more effective for permeate flux recovery. Moreover, the hollow fiber UF system by adding periodical backwash with permeate was examined for Chlorella sp. harvesting.

Results and discussion

It was found that Chlorella sp. could be concentrated with high recovery in a lab-scale experiment. An overall algal biomass recovery of above 90% was achieved when the volume concentration factor was 10. For an original biomass of 1.3?±?0.05?g/L, 1?min backwash followed by 20?min forward concentrating was more effective, which resulted in a recovery of 94% and a high average flux of 30.3?L/m²/h. In addition, the algal recovery was highly correlated to the volume concentration factor and the initial biomass. A high concentration factor or a high initial biomass resulted in a low biomass recovery.     

Urbanisation and human health in China: spatial features and a systemic perspective

Background, aims and scope

Current studies have paid little attention to the dynamism in urban spatial expansion and its possible environmental and health effects or to the health effects of rapid urban environmental change at different points along the urbanisation gradient. This study adopts a public health ecology approach to systematically understand the relationship between urbanisation, urban environmental change and human health in China.

Method

Remote sensing image analysis, based on night light data at five different time periods in recent decades, was used to determine changes to the overall urban area. Through a review of the evidence on the relationships between environmental health, urbanisation and health, we advance a pathway framework for explaining urban human health ecology. The Spearman rank correlation coefficient was used to measure the correlation between disease prevalence and urbanisation level, adding a further dimension to a systemic understanding of urban health.

Results and conclusions

Urban areas have been increasing spatially, but unevenly, in recent decades, with medium and small cities also expanding rapidly in the past decade. Urbanisation and urban expansion result in changes to land use/coverage change, the urban environment and the residents?? lifestyle, which result in human health problems. Regions with the highest urbanisation level were more inclined to have a high prevalence of chronic disease in recent decades. An ecological public health approach provides insights into the multiple types of data which need to be routinely collected if human disease is not to become a barrier to social and economic development.     

石油类污染物自然衰减能力现场试验验证研究

在北京地区某加油站开展的前期石油类污染物自然衰减现场试验的基础上,进一步开展了验证试验,结果表明本次试验得到的挥发性有机物(VOCs)变化趋势及O2、CO2含量沿土壤深度分布和前期试验结果呈现相同的规律,说明基于自然衰减法设计实施的加油站现场试验检测分析结果可靠,试验方法具有合理性、可操作性及可重复性.进一步的理论分析对前期试验结果进行了验证,得出以下结论:(1)通过氧平衡和碳平衡计算对加油站土壤内的自然衰减方式进行评价,验证了该加油站地下土壤中实际发生的微生物降解既有需氧降解也有厌氧降解;(2)利用有机物的一级衰减模型对该污染现场土壤中石油类污染物的降解速率和半衰期进行计算表明,2次试验计算得到的石油类污染物的半衰期基本一致,该污染现场石油类污染物的半衰期为50 d左右;(3)在此基础上,对该加油站包气带土壤的自然衰减能力和环境质量进行评价,2次试验结果均表明该污染现场在自然衰减的作用下已经不存在环境风险.