Lithological and environmental controls on large tafoni along conglomerate cliffs in subtropic humid Danxiashan UNESCO Global Geopark

Tafoni are a type of cavernous weathering features widespread in different climate zones around the world,but their origin has not been fully understood.Little attention was paid on tafoni in conglomerates.Danxiashan UNESCO Global Geopark,located within the subtropic humid region of South China,has a landscape of large tafoni that occur on cliffs of red conglomerates.Both the Dinosaur Rock and Pagoda Peak of the geopark were selected to investigate the formation mechanisms of tafoni in conglomerates.During the field investigation,the size,rock hardness,and the external and internal meteorology of tafoni were measured and tested.The texture and composition of rock samples were observed,and the ion chromatography experiments were performed as well.Results show that tafoni have well ellipsoidal openings.Clasts of the conglomerates are largely sub-rounded and poorly sorted,and the cement is dominantly composed of calcite and iron oxide.The hardness of the lips is almost equal to that of the columns,and both are slightly higher than the backwalls.Compared with the external intense environmental changes,the interior of the tafoni is characterized by smaller temperature and relative humidity ranges and windless condition.Therefore,the porous and permeable conglomerates provide favorable lithology for tafoni development,and the micro-environment within the caverns is conducive to improving water utilization efficiency and enhancing salt weathering.The salts mainly consist of sulfates and nitrates,which might be derived from frequent raining,water evaporation and red beds as well.Consequently,tafoni are the result of the synergistic effects by multiple factors,rather than a single mechanism.

Effects of sorbitol and sucrose on soybean-urease induced calcium carbonate precipitate

This study explores the effects of two nucleating agents,sucrose and sorbitol,on soybean-urease induced calcium carbonate precipitation(SICP)at a crystal level.Comparative studies on the mineral composition,crystal size,surface morphologies and thermal stability of SICP samples with/without nucleating agent were investigated with high resolution XRD,SEM and synchronous thermal analyzer(STA),respectively.The results show the introductions of sorbitol or sucrose to SICP reduce the content of vaterite(114)from 10.07%to 1.81%-3.93%,indicating their effect on transforming vaterite into stabler calcite.Sorbitol can enlarge the crystals and improve the thermostability of SICP,indicating an improvement of the crystallinity of SICP.The sucrose-regulated SICP shows medium thermostability which is worse than SICP without the nucleating agent,indicating the addition of sucrose reduces the crystallinity of SICP.Sorbitol is an effective nucleating agent that can improve the behaviors all-around,while sucrose increases the calcite content of SICP but inhibits the crystallinity of SICP.This study reveals the regulations of SICP because of the introduction of sorbitol or sucrose,and provides guidance to the subsequent engineering application of SICP.

Influence on shallow ground water by nitrogen in polluted river

The main purpose of the research is to discuss the influence on ground water by NH4-N in polluted river and river bed.In the lab-scale experiment three kinds of natural sand were chosen as infiltration medium,and polluted rivers were simulated by domestic sewage,after 10-month sand column test it was found that NH_4-N came to adsorption sa- turation on the 17th day in coarse sand and on the 130～140th day in medium sand,then had a higher effluent concentration because of desorption.It is concluded that NH_4-N eas- ily moved to ground water.When the concentration of NH_4-N in Liangshui River were 46.86,26.95 mg/L,that in groundwater are less than 1.10 mg/L.It is found that Liangshui River have a little influence on groundwater because of bottom mud,thickness and char- acter of the infiltration medium under the river bed and seepage quantity of river water. Clean water leaching test states that after the silt is cleared away and clean water is poured,NH_4-N in the penetration media under the polluted river is obviously carried into ground water,and ground water is polluted secondly.

Influence on shallow ground water by heavy metal in polluted river

The main purpose of the research is to study the influence on shallow ground water by heavy metal in polluted river. In the lab-scale experiment polluted rivers were simulated by domestic sewage, and three kinds of natural sand were chosen as infiltration medium, it was found that Cr（Ⅵ）penetrated on the 13th day and then had a removal ratio of 77%-99% in coarse sand,over 91% and 96% in two kinds of medium sand. From beginning to end in column 2 and column 3 the removal ratio of lead were greater than 97%. It is difficult for Cr（Ⅵ） and lead to enter ground water. In on-site test it indicates that the concentration of Cr（Ⅵ） in No.1-3 and coal yard well along the bank of Liangshui River is not greater than background concentration in groundwater, so Cr （Ⅵ） in Liangshui River has a little influence on ground water. The mechanism of Cr（Ⅵ） removal is reducing action and sedimentation. The removal mechanism of lead primarily is chemical adsorption and generation deposit. Cr（Ⅵ） mainly is transformed to precipitation by reducing action because of abundant reduction agent in the infiltration media, so the tests indicat that polluted river is not the source of Cr （Ⅵ） pollution in ground water. Generally lead may polluted soil, but not groundwater.

Oxygen vacancy mediated bismuth-based photocatalysts

Sunlight-driven photocatalysis,which can produce clean fuels and mitigate environmental pollution,has received extensive research attention due to its potential for addressing both energy shortages and environmental crises.Bismuth(Bi)-based photocatalysts with broad spectrum solar-light absorption and tunable structures,exhibit promising applications in solar-driven photocatalysis.Oxygen vacancy(OV)engineering is a widely recognized strategy that shows great potential for accelerating charge separation and small molecule activation.Based on OV engineering,this review focuses on Bi-based photocatalysts and provides a comprehensive overview including synthetic methods,regulation strategies,and applications in photocatalytic field.The synthetic methods of Bibased photocatalysts with OVs(BPOVs)are classified into hydrothermal,solvothermal,ultraviolet light reduction,calcination,chemical etching,and mechanical methods based on different reaction types,which provide the possibility for the structural regulation of BPOVs,including dimensional regulation,vacancy creation,elemental doping,and heterojunction fabrication.Furthermore,this review also highlights the photocatalytic applications of BPOVs,including CO_(2)reduction,N2 fixation,H2 generation,O_(2)evolution,pollutant degradation,cancer therapy,and bacteria inactivation.Finally,the conclusion and prospects toward the future development of BPOVs photocatalysts are presented.

The nitritation performance of biofilm reactor for treating domestic wastewater under high dissolved oxygen

The objective of this study was to investigate the nitritation performance in a biofilm reactor for treating domestic wastewater.The reactor was operated in continuous feed mode from phases 1 to 3.The dissolved oxygen（DO）was controlled at 3.5–7 mg/L throughout the experiment.The biofilm reactor showed excellent nitritation performance after the inoculation of nitrifying sludge,with the hydraulic retention time being reduced from 24 to 7 hr.Above 90%nitrite accumulation ratio（NAR）was maintained in phase 1.Afterwards,nitratation occurred with the low NH4^＋–N concentration in the reactor.The improvement of NH4^＋–N concentration to 20–35 mg/L had a limited effect on the recovery of nitritation.However,nitritation recovered rapidly when sequencing batch feed mode was adopted in phase 4,with the effluent NH4^＋-N concentration above 7 mg/L.The improvement of ammonia oxidizing bacteria（AOB）activity and the combined inhibition effect of free ammonia（FA）and free nitrous acid（FNA）on the nitrite oxidizing bacteria（NOB）were two key factors for the rapid recovery of nitritation.Sludge activity was obtained in batch tests.The results of batch tests had a good relationship with the long term operation performance of the biofilm reactor.

Generating ^(1)O_(2) and Co^(IV)=O through efficient peroxymonosulfate activation by ZnCo_(2)O_(4)nanosheets for pollutant control

Heterogeneous advanced oxidation processes(AOPs)based on non-radical reactive species are considered as a powerful technology for wastewater purification due to their long half-lives and high adaptation in a wide pH range.Herein,we fabricate surface Co defect-rich spinel ZnCo_(2)O_(4)porous nanosheets,which can generate≡CoIV=O and ^(1)O_(2) over a wide pH range of 3.81-10.96 by the formation of amphoteric≡Zn(OH)2 in peroxymonosulfate(PMS)activation process.Density functional theory(DFT)calculations show Co defect-rich ZnCo_(2)O_(4)possesses much stronger adsorption ability and more electron transfer to PMS.Moreover,the adsorption mode changes from terminal oxygen Co-O-Co to Co-O,accelerating the polarization of adjacent oxygen,which is beneficial to the generation of≡CoIV=O and Generating ^(1)O_(2) .Co defect-rich ZnCo_(2)O_(4)porous nanosheets exhibit highly active PMS activation activity and stability in p-nitrophenol(PNP)degradation,whose toxicity of degradation intermediates is significant reduction.The Co defect-rich ZnCo_(2)O_(4)nanosheet catalyst sponge/PMS system achieved stable and efficient removal of PNP with a removal efficiency higher than 93%over 10 h.This work highlights the development of functional catalyst and provides an atomic-level understanding into non-radical PMS activation process in wastewater treatment.

Government environmental control measures on CO_(2) emission during the 2014 Youth Olympic Games in Nanjing:Perspectives from a top-down approach

Strict air pollution control measures were conducted during the Youth Olympic Games(YOG)period at Nanjing city and surrounding areas in August 2014.This event provides a unique chance to evaluate the effect of government control measures on regional atmospheric pollution and greenhouse gas emissions.Many previous studies have observed significant reductions of atmospheric pollution species and improvement in air quality,while no study has quantified its synergism on anthropogenic CO_(2)emissions,which can be coreduced with air pollutants.To better understand to what extent these pollution control measures have reduced anthropogenic CO_(2)emissions,we conducted atmospheric CO_(2)measurements at the suburban site in Nanjing city from 1^(st) July to 30^(th) September 2014 and 1^(st) August to 31^(st) August 2015,obvious decrease in atmospheric CO_(2)was observed between YOG and the rest period.By coupling the a prioriemission inventory with atmospheric transport model,we applied the scale factor Bayesian inversion approach to derive the posteriori CO_(2)emissions in YOG period and regular period.Results indicate CO_(2)emissions from power industry decreased by 45%,and other categories also decreased by 16%for manufacturing combusting,and 37%for non-metallic mineral production.Monthly total anthropogenic CO_(2)emissions were 9.8(±3.6)×10^(9) kg/month CO_(2) for regular period and decreased to 6.2(±1.9)×10^(9) kg/month during the YOG period in Nanjing city,with a 36.7%reduction.When scaling up to whole Jiangsu Province,anthropogenic CO_(2)emissions were 7.1(±2.4)×10^(10) kg/month CO_(2)for regular period and decreased to 4.4(±1.2)×10^(10)kg/month CO_(2) during the YOG period,yielding a 38.0%reduction.

Monitoring Soil Microbial Activities in Different Cropping Systems Using Combined Methods

Cropping activities may affect soil microbial activities and biomass,which would affect C and N cycling in soil and thus the crop yields and quality.In the present study,a combination of microcalorimetric,enzyme activity(sucrase,urease,catalase,and fluorescein diacetate hydrolysis),and real-time polymerase chain reaction(RT-PCR) analyses was used to investigate microbial status of farmland soils,collected from 5 different sites in Huazhong Agriculture University,China.Our results showed that among the 5sites,both positive and negative impacts of cropping activities on soil microbial activity were observed.Enzyme activity analysis showed that cropping activities reduced soil sucrase and urease activities,which would influence the C and N cycles in soil.Much more attentions should be given to microbial status affected by cropping activities in future.According to the correlation analysis,fluorescein diacetate hydrolysis showed a significantly(P < 0.05) negative correlation with the time to reach the maximum power output(R ——0.898),but a significantly(P < 0.05) positive correlation with bacterial gene copy number(R = 0.817).Soil catalase activity also showed a significantly(P < 0.05) positive correlation with bacterial gene copy number(R = 0.965).Using combined methods would provide virtual information of soil microbial status.