Modification of activated carbon using urea to enhance the adsorption of dioxins.

Activated carbon is commonly used to remove dioxins from flue gas via adsorption. Improving the targeted adsorption capacity of activated carbon for dioxins can reduce the consumption of adsorbents and help achieve emission standards for target pollutants. Here, commercial coal-based activated carbon was used as a raw material and modified by urea impregnation along with treatment at high temperature under a nitrogen atmosphere. It was found that modification with urea effectively improved the pore structure of activated carbon while incorporating a certain amount of nitrogen. The best modification effect was achieved at a modification temperature of 600 °C, an impregnation ratio of urea to activated carbon of 1:1, and with high-temperature treatment for 2 h. The mesopore volume of the modified activated carbon (AC600) reached 0.38 cm3/g, accounting for 57.58% of the total pore volume. With an impregnation ratio of urea to activated carbon of 1:1, high-temperature treatment for 2 h, and a modification temperature of 800 °C, a certain amount of nitrogen was introduced into the carbon rings to form a modified activated carbon (AC800) rich in pyridine and pyrrole groups (atomic percentage = 4.84%). The activated carbon modified by urea and the unmodified activated carbon were subsequently selected for dioxin adsorption experiments using a dioxin generation and adsorption system. AC600 showed the highest adsorption efficiency for dioxins, reaching 97.65%, based on toxicity equivalents. Although AC800 has poor pore properties, it has more pyridine and pyrrole groups than AC600. Consequently, the efficiency of AC800 at adsorbing low-concentration dioxins reached 85.24% based on toxicity equivalents. Overall, this study describes two mechanisms for effectively modifying activated carbon with urea based on (1) optimizing the pore structure of activated carbon and (2) incorporating nitrogen.

Human rabies surveillance and control in China, 2005-2012.

BACKGROUND: Rabies reemerged in China during the 1990s with a gradual increase in the number and geographical dispersion of cases. As a consequence, a national surveillance program was introduced in 2005 to investigate the outbreak in terms of vaccination coverage, PEP treatment, and geographical and social composition. METHODS: The surveillance program was coordinated at the national level by the Chinese Center for Disease Control (CCDC) with data collected by regional health centres and provincial CCDCs, and from other official sources. Various statistical and multivariate analysis techniques were then used to evaluate the role and significance of implemented policies and strategies related to rabies prevention and control over this period. RESULTS: From 2005-2012, 19,221 cases were reported across 30 provinces, but these primarily occurred in rural areas of southern and eastern China, and were predominantly associated with farmers, students and preschool children. In particular, detailed analysis of fatalities reported from 2010 to 2011 shows they were associated with very low rates of post exposure treatment compared to the cases with standard PEP. Nevertheless, regulation of post-exposure prophylaxis quality, together with improved management and vaccination of domesticated animals, has improved prevention and control of rabies. CONCLUSIONS: The various control policies implemented by the government has played a key role in reducing rabies incidences in China. However, level of PEP treatment varies according to sex, age, degree and site of exposure, as well as the source of infection. Regulation of PEP quality together with improved management and vaccination of domesticated animals have also helped to improve prevention and control of rabies.

Comparative analysis of the pathogenic mechanisms of street rabies virus strains with different virulence levels.

OBJECTIVE: To characterize two strains of street rabies virus (RABV) isolated from the brain tissue of cattle from Inner Mongolia. Differences in the histopathological and ultrastructural changes in the brain tissue of infected mice were determined to reveal variation in the pathogenesis of infection between street rabies virus strains. METHODS: Ten-day-old mice were intracranially inoculated with one of three virus strains and brain tissue harvested when the mice were moribund. Various histopathological and ultrastructural markers of disease were then compared between the groups. RESULTS: Infection with the street virus strain CNM1101C resulted in severe neuronal dendrites damage, but only mild cell apoptosis, T lymphocyte infiltration and microglial activation. Infection with the other street virus strain, CNM1103C, was characterized by cell apoptosis, T lymphocyte infiltration and microglial activation as well as dendrites damage. However, in comparison, infection with the attenuated virus strain CTN caused severe T lymphocyte infiltration, microglial activation and cell apoptosis, but left the neuronal dendrites intact. CONCLUSION: The two street rabies virus strains isolated from cattle from Inner Mongolia had different levels of virulence and caused distinct pathological changes in infected mice. Therefore, we concluded that different pathogenic mechanisms exist between different RABV strains.

Dioxin emission and distribution from cement kiln co-processing of hazardous solid waste.

Cement kiln collaborative disposal technology can not only dispose of hazardous waste but also provide energy for the cement industry. However, the addition of hazardous waste may promote the formation of dioxins in cement kilns. In this study, typical hazardous solid wastes, such as solidified fly ash, electroplating sludge, and industrial residue, were co-processed in a cement kiln with different feeding positions and different feeding amounts. The concentrations of dioxins in the flue gas, clinker, and precalciner furnace slag were investigated. The effect of adding mixed hazardous solid waste on the formation of dioxin was also studied. The results showed that the concentration of dioxin in the flue gas without added hazardous waste was 1.57 ng/m3, and the concentration varied from 1.03 to 6.49 ng/m3 after the addition of hazardous waste. In addition, the concentration of dioxin in the flue gas and solid samples increased substantially when the co-processing ratio doubled. The large amount of Cu in solidified fly ash promoted the formation of dioxins, while the higher S content in the electroplating sludge suppressed the formation of dioxins. Compared with the addition of single hazardous waste, the concentration of dioxin in precalciner furnace slag increases by about 300%. Furthermore, the distributions of isomers in the clinker and precalciner furnace slag were similar. 1,2,3,4,6,7,8-HpCDD and OCDD accounted for a large proportion of the mass concentration, and the contribution rate ranged from 48.7 to 82.0%. Most importantly, correlation analysis showed that the concentration of dioxin was closely related to the copper content, hazardous waste types and additive proportion, with correlation coefficients of 0.79, 0.83, and 0.89, respectively. This study provides a basis for exploring the high environmental benefits of disposing of hazardous solid waste by co-processing in cement kilns.

[Adsorption Characteristics of Sulfamethazine on Three Typical Porous High-temperature Modified Solid Waste Materials].

Three typical porous solid wastes, including livestock manure, crop straw, and coal mining waste, were used as raw materials to prepare cattle manure charcoal, straw charcoal, and coal gangue charcoal by low-oxygen controlling temperature carbonization and calcination. Batch adsorption experiments of sulfamethazine (SMZ) in water were carried out. Adsorption kinetics and isothermal adsorption equilibrium were used to investigate the adsorption characteristics of SMZ on cattle dung charcoal, straw charcoal, and coal gangue charcoal, and the adsorption mechanism was discussed by means of field-electron scanning electron microscope, Fourier transform infrared spectroscopy, Boehm titration, Brunauer-Emmett-Teller measurement, and zeta potentiometric titration. The results showed that the adsorption of SMZ on the three carbon materials reached equilibrium at 24 h. The adsorption kinetics of SMZ on three kinds of carbon materials agreed with the quasi-second-order kinetics equation. R2 ranged from 0.9968 to 0.9999, and the adsorption rate decreased with the decrease in effective adsorption sites on the surface of carbon materials. The adsorption process mainly consists of three steps:membrane diffusion, intraparticle diffusion, and the equilibrium stage. Both intraparticle diffusion and membrane diffusion control the adsorption rate. Isothermal adsorption is more consistent with the Freundlich model. R2 is between 0.9874 and 0.9997. It is mainly physical adsorption and spontaneous exothermic reaction. The maximum adsorption capacity of the three kinds of carbon materials was cattle dung carbon (19.64 mg·g-1) > coal gangue carbon (12.06 mg·g-1) > straw carbon (9.16 mg·g-1). The adsorption mechanism of SMZ on the three kinds of carbon materials mainly includes hydrogen bonding between molecules, surface electrostatic adsorption of multi-molecular layers, and pore filling. Of these, electrostatic adsorption is the main adsorption mechanism. The best adsorption performance of cattle manure charcoal may be due to its rich oxygen-containing functional groups, more negative charges, and larger specific surface area and pore volume.

[Effect and Mechanism of Attapulgite and Its Modified Materials on Bioavailability of Cadmium in Soil].

The effect of attapulgite (magnesium aluminium phyllosilicate) and its modified materials on the extractability of soil Cd and the accumulation of Cd in lettuce (Lactuca sativa) were investigated using a pot-culture experiment, and the immobilization mechanism of attapulgite and its modified materials was explored through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed that attapulgite and its modified materials could significantly reduce the Cd concentration in Lactuca sativa, with maximum reductions of 41.0% and 56.5%, respectively, and attapulgite modified materials treatments appeared more efficient than attapulgite treatments in reducing Cd uptake of Lactuca sativa. The saturated adsorption capacity for the adsorption of Cd2+ on attapulgite rose distinctly after being modified. Attapulgite and its modified materials could significantly reduce Cd content in soil CaCl2 extract at the dosage of 1%, with the maximum reduction rates of 34.2% and 34.3%, respectively. The attapulgite formed a complex to immobilize Cd mainly through the surface silanol and Cd2+ complexation reaction, while the modified attapulgite formed a complex mainly through the complexation of Cd2+ with carboxyl groups which existed in addition to the complexation with surface hydroxyl, thus reducing the mobility of Cd2+ and achieving remediation of Cd-contaminated soil. In summary, attapulgite and its modified materials can both be used for remediation of Cd-contaminated soil, and the mechanisms for this function were found to be different.

Rabies Cases in the West of China Have Two Distinct Origins.

In China, rabies remains an ongoing threat to public health. Although control efforts have been effective in reducing the number of annual cases, the virus continues to spread into new areas. Tibet, Qinghai, Gansu and Ningxia in western China have, until recently, reported only a handful of events. However, since 2011, there have been increasing numbers of cases recorded in these areas. In this study, we report the collection and analysis of samples collected from these regions. We find that cases originate from two different sources. Strains collected from Gansu and Ningxia are closely related to the primary lineage associated with the current epizootic, whereas those from Tibet and Qinghai are related to the Arctic-like-2 lineage that is most commonly associated with wildlife cases in China. Thus, it appears that while the epizootic is beginning to encroach into Gansu and Ningxia, Tibet and Qinghai a significant number of rabies cases originate from wildlife.

[Effects of reclaimed water recharge on groundwater quality: a review].

Reclaimed water recharge to groundwater is an effective way to relieve water resource crisis. However, reclaimed water contains some pollutants such as nitrate, heavy metals, and new type contaminants, and thus, there exists definite environmental risk in the reclaimed water recharge to groundwater. To promote the development of reclaimed water recharge to groundwater and the safe use of reclaimed water in China, this paper analyzed the relevant literatures and practical experiences around the world, and summarized the effects of different reclaimed water recharge modes on the groundwater quality. Surface recharge makes the salt and nitrate contents in groundwater increased but the risk of heavy metals pollution be smaller, whereas well recharge can induce the arsenic release from sedimentary aquifers, which needs to be paid more attention to. New type contaminants are the hotspots in current researches, and their real risks are unknown. Pathogens have less pollution risks on groundwater, but some virus with strong activity can have the risks. Some suggestions were put forward to reduce the risks associated with the reclaimed water recharge to groundwater in China.

[Public awareness assessment of water reuse in Beijing].

Reusing reclaimed municipal wastewater to mitigate urban water shortage is gaining widespread attentions. Beijing has led the nation in implementation and close to 60% of the treated municipal wastewater effluent is being reused. We evaluated the public's awareness of water reuse practices throughout the city. Based on questionnaire and the SPSS software, we analyzed the people's knowledge on water, wastewater and reclaimed issues and willingness to use reclaimed water along with their socio-economical background. While the public was keenly aware of the severe water shortage and the need to treat wastewater, they did not have clear ideas on sources of water supply, the biggest users of water, and the largest contributor of municipal wastewater. Results show that the majority of the Beijing residents we surveyed were not cognizant of water reuses taken places throughout the city. Greater than 80% of the residents would accept reclaimed wastewater for reuses even for domestic usages as long as not related to drinking and food preparation. However, 63% of them would reject reusing it to supplement the public water supply. In general, subjects at a higher education level, with higher personal income, and between ages of 35 to 55 tended to be more supportive of the water reuses. The gender did not significantly affect the outcome of the survey. To enhance the awareness of the city residents, it suggests forwarding the propaganda and management, strengthening the policy-oriented and facility support from the public, community and government.

[Model simulation of the transportation, transformation and accumulation of synthetic musks in soils input through recycle water irrigation].

Environmental pollution of synthetic musks HHCB and AHTN, one type of PPCPs, have been attracted great attentions in latest years. One of the main input pathways of HHCB/AHTN to soils is reclaimed water irrigation. In this study, we monitored HHCB and AHTN in soils irrigated by reclaimed water and irrigation water and modeled the transportation and accumulation of HHCB and AHTN in soils using HYDRUS-1D. Results showed that concentrations of HHCB and AHTN in soils irrigated by recycling water were 5 times higher than tape water irrigation soils although both of the concentrations are trace. The temporal increase of accumulation was exponential when lgK(oc) value was 3.44, while linear when lgK(oc) were 4.12 and 4.86. Changes of half life of HHCB/AHTN did not affect their accumulation in surface soils. The downward transportation of HHCB and AHTN under recycling water irrigation was very slow. After 40 years of irrigation, it could only 53 cm at most favored conditionals. The downward movement was greatly impacted by the lgK(oc) values. The dissipation of those two synthetic musks through biological degradation and plant uptake were tiny. The highest dissipation rate through biological degradation and plant uptake was only 7.69% of the total input by reclaimed water irrigation after 40 years. The dissipation rate was increased with the decrease of lgK(oc) values and irrigation time. Results of this work may offer base for accurate assessing the ecological risks of HHCB and AHTN in soils caused by reclaimed water irrigation.

[Ecological risks of reclaimed water irrigation: a review].

Wastewater reclamation and reuse have become an important approach to alleviate the water crisis in China because of its social, economic and ecological benefits. The irrigation on urban green space and farmland is the primary utilization of reclaimed water, which has been practiced world widely. To understand the risk of reclaimed water irrigation, we summarized and reviewed the publications associated with typical pollutants in reclaimed water including salts, nitrogen, heavy metals, emerging pollutants and pathogens, systematically analyzed the ecological risk posed by reclaimed water irrigation regarding plant growth, groundwater quality and public health. Studies showed that salt and salt ions were the major risk sources of reclaimed water irrigation, spreading disease was another potential risk of using reclaimed water, and emerging pollutants was the hot topic in researches of ecological risk. Based on overseas experiences, risk control measures on reclaimed water irrigation in urban green space and farmland were proposed. Five recommendations were given to promote the safe use of reclaimed water irrigation including (1) strengthen long-term in situ monitoring, (2) promote the modeling studies, (3) build up the connections of reclaimed water quality, irrigation management and ecological risk, (4) evaluate the soil bearing capacity of reclaimed water irrigation, (5) and establish risk management system of reclaimed water reuse.

[Soil salinity in greenland irrigated with reclaimed water and risk assessment].

Compared to drinking water or groundwater, reclaimed water contains more salts. Therefore, the effects of application of reclaimed water on the soil salinity have received great attentions. To evaluate the potential risks posed by long-term reclaimed water irrigation, we collected surface soil samples from urban green lands and suburban farmlands of Beijing represented different irrigation durations. The electrical conductivity (EC) and sodium adsorption ratio (SAR) in soils were measured subsequently. Both EC1:5 and SAR1.5 from the green land and farmland soils irrigated with reclaimed water were significantly higher than those of control treatments (drinking water or groundwater irrigation). The EC1:5 values increased by 12.4% and 84.2% than control treatments in the greenland and farmland, respectively. The SAR1:5 values increased by 64.5% and 145.8% than control treatments, respectively. No significant differences of both EC1:5 and SAR1:5 were found between of 0-10 cm and 10-20 cm soil layer. A slight decrease of soil porosity was observed. The field investigation suggested there was a high potential of soil salinization under long-term reclaimed water irrigation. Proper management practices should be implemented to minimize the soil salinity accumulation risk when using reclaimed water for irrigation in Beijing.

[Effect of reclaimed water irrigation on soil properties and vertical distribution of heavy metal].

Utilization of reclaimed water is one of the important methods to alleviate water shortage. The effect of reclaimed water irrigation on soil is always a concern. To understand the effect of long time reclaimed water irrigation on soil, typical farmland irrigated with reused water was selected. Soil properties and heavy metal concentration of soil and water samples were analyzed to identify the effect of the irrigation on heavy metal vertical distribution and organic matter content, total carbon, total nitrogen and pH value in soil. The results show that heavy metal contents of irrigation water used in Liangshuihe farmland are 2.5 to 10.5 times higher than that of Beiyechang farmland, and reclaimed water irrigation could cause changes of soil properties that soil organic matter content, total carbon, total nitrogen were increased and pH values were reduced. Based on the field investigation results, the soil nutrient conditions benefit from irrigate reclaimed water, however, the accumulation of heavy metal in soil could raise the risk. As a source of soil heavy metal, reclaimed water irrigation could make differences on the accumulation and mobility of soil heavy metal. Also the distribution and mobility of soil heavy metal are influenced by soil organic matter content and there are more heavy metal were taken up by plants or transferred to the deeper area in Liangshuihe farmland.

[Modeling the Cd accumulation in agricultural soil irrigated with reclaimed water].

Recent years, soil pollution of heavy metal has affected human life seriously, especially in farmland. Heavy metal pollution in farmland is mainly caused by irrigation, fertilizing and atmospheric fallout. As the character of heavy metal input in farmland is chronic and low dosage, application of model would be more suitable than routine methods to illustrate the dynamic changes of heavy metals in soil. In this paper, we use the model of STEM-profile to analyze and predict Cd pollution in farmland in Tongzhou, Beijing, based on the data from field survey. The results showed that: the concentration of Cd in this land would exceed the national soil environment standard after 100 years under current situations, reaching 0.866 mg x kg(-1) in plow layer. Studies of the influence of the amount and the form of inputs and the amount of irrigation water on the distribution of Cd in soil showed that irrigated with reclaimed water or fertilized with organic manure could lead to accumulation of Cd in the soil, while groundwater irrigation with inorganic fertilization would not cause accumulation of Cd in soil. When Cd inputs changed from mineral to organic form, the concentration of Cd in plow layer would be 0.943 mg x kg(-1) after 100 year. When the amount of irrigation water increased from 0.8 ET to 1.5 ET and to 2.0 ET, the plow layer Cd content would be 0.952, 0.784 and 0.638 mg x kg(-1) respectively.

[Regional atmospheric environment risk source identification and assessment].

Identification and assessment for atmospheric environment risk source plays an important role in regional atmospheric risk assessment and regional atmospheric pollution prevention and control. The likelihood exposure and consequence assessment method (LEC method) and the Delphi method were employed to build a fast and effective method for identification and assessment of regional atmospheric environment risk sources. This method was applied to the case study of a large coal transportation port in North China. The assessment results showed that the risk characteristics and the harm degree of regional atmospheric environment risk source were in line with the actual situation. Fast and effective identification and assessment of risk source has laid an important foundation for the regional atmospheric environmental risk assessment and regional atmospheric pollution prevention and control.

[Characterization and potential risks of polycyclic aromatic hydrocarbons in green space soils of educational areas in Beijing].

Pollution of green space by polycyclic aromatic hydrocarbons (PAHs) in education area may pose a potential impact on the faculty, students, and staffs. To study the characterization, influencing factors, sources and risks of soil PAHs in Beijing educational areas, the concentrations of 16 priority PAH identified by United States Environmental Protection Agency (USEPA) in green spaces of 20 schools and academies were determined. The total PAHs concentration ranged from 194 microg x kg(-1) to 6 988 microg x kg(-1), with a mean of 1 637 microg x kg(-1). Middle and high molecular weight PAHs (4-6 rings) accounted for 85% of the total PAHs concentration. Coal combustion for winter heating and food supply were the main sources of PAHs in Beijing educational areas. Based on the Cluster analysis, the transportation and accumulation of NAP were distinguished from other 15 PAH congeners. No significant correlation between PAHs and soil organic matter (SOM) was found except for NAP, suggesting that most of the PAH congeners were derived from direct deposition of urban sources. The integrated lifetime cancer risks (ILCRs) associated with exposure to soil PAHs in Beijing educational areas were acceptable, but the indirect effects should not be ignored.

[Study on soil enzyme activities and microbial biomass carbon in greenland irrigated with reclaimed water].

The physicochemical properties of soils might be changed under the long-term reclaimed water irrigation. Its effects on soil biological activities have received great attentions. We collected surface soil samples from urban green spaces and suburban farmlands of Beijing. Soil microbial biomass carbon (SMBC), five types of soil enzyme activities (urease, alkaline phosphatase, invertase, dehydrogenase and catalase) and physicochemical indicators in soils were measured subsequently. SMBC and enzyme activities from green land soils irrigated with reclaimed water were higher than that of control treatments using drinking water, but the difference is not significant in farmland. The SMBC increased by 60.1% and 14.2% than those control treatments in 0-20 cm soil layer of green land and farmland, respectively. Compared with their respective controls, the activities of enzymes in 0-20 cm soil layer of green land and farmland were enhanced by an average of 36.7% and 7.4%, respectively. Investigation of SMBC and enzyme activities decreased with increasing of soil depth. Significantly difference was found between 0-10 cm and 10-20 cm soil layer in green land. Soil biological activities were improved with long-term reclaimed water irrigation in Beijing.

[Characteristics and sources of polycyclic aromatic hydrocarbons in surface soil from chemical industrial areas].

Concentrations and composition of 16 polycyclic aromatic hydrocarbons (PAHs) listed for prior control by US EPA were detected by analyzing 28 surface soil samples from the chemical industrial areas of Tianjin Binhai New Area with a gas chromatography equipped with mass spectrometry (GC/MS). Relative concentrations of PAH compounds with different benzene rings and principal component analysis were used to identify the possible sources of soil PAHs. The maximum PAH concentration in all the samples was 5,991.7 ng x g(-1), with a mean values of 1,185.0 ng x g(-1). The concentrations of four and five rings PAH components were higher than that of the other PAH components in Tanggu and Hangu chemical industrial areas, and three rings PAH components were major PAHs in Dagang petroleum industrial area. There is significant positive correlation (n = 28, R2 = 0.847, p < 0.01) between PAH concentrations and total organic carbon (TOC) contents in the soil samples. Coal combustion was the dominant source of PAHs in chemical industrial areas, while petroleum volatilization and leakage were main contributors of PAHs in Dagang petroleum industrial area.

[Kinetic characteristics of Cd2+ desorption in minerals and soils under simulated acid rain].

The kinetic characteristics of Cd2+ desorption in minerals and soils under simulated acid rain were studied by using the flow-stirred method. It showed that Cd2+ desorption could be described by first-order kinetics. Percents of desorption amounts of Cd2+ calculated were 70%-100% in red soil and goethite, and 25%-50% in latosols and kaolinite. Parabolic diffusion could describe Cd2+ desorption kinetics in latosols and not suitable for red soil and goethite and kaolinite. Cd2+ desorption, regarded as a heterogeneous diffusion in minerals and soils, could be fitted by Elovich equation more than Parabolic diffusion and two-constant equation. Cd2+ desorption could be divided into fast reaction and slow reaction. Except for latosols, fast reaction would be over during 60 min and be close to quasi-equilibrium. Adsorption forms of Cd2+ in soil surface could be exchangeable and specific. Fast reaction was relative to easily desorbed Cd2+. The affinity of edge hydroxyl to Cd2+ would lead to the difference of Cd2+ desorption rate and amounts. Increase of pH value in effluent indicated H+ consumption in the processes of Cd2+ desorption.