Synergistic photocatalytic effect of porous g-C_3N_4 in a Cr(Ⅵ)/4-chlorophenol composite pollution system

The photocatalytic reduction of aqueous Cr(VI)to Cr(III)was preliminarily studied using porousg‐C3N4as a photocatalyst under acidic conditions.The observed synergistic photocatalytic effect ofporous g‐C3N4on a Cr(VI)/4‐chlorophenol(4‐CP)composite pollution system was further studiedunder different pH conditions.Compared with single‐component photocatalytic systems for Cr(VI)reduction or4‐CP degradation,the Cr(VI)reduction efficiency and4‐CP degradation efficiency weresimultaneously improved in the Cr(VI)/4‐CP composite pollution system.The synergistic photocatalyticeffect in the Cr(VI)/4‐CP composite pollution system can be attributed to the acceleratedredox reaction between dichromate and4‐CP by electron transfer with porous g‐C3N4.

Combined Pollution and Pollution Index of Heavy Metals in Red Soil

A field experiment was conducted to study the effects of Pb, Cd, Cu, Zn and As coexisting in red soilon growth of rice (Oryza sativa L.), mung bean (Vigna rabiata (Linn.) Wilczek), alfalfa (Medicago sativaL.), slash pine (Pinus elliottii Engelm.) and aspen (Populus L.). Results showed that rice, mung bean andalfalfa were significantly innuenced by combined pollution of the heavy metals. The contents of Pb, cd andAs in rice grains greatly exceeded the National Standards for Food Hygiene of China. Heavy metals at ahigh concentration seriously retarded growth of mung bean and alfalfa, but not so obviously with slash pineand aspen. The composite index is suggested for evaluating the relativity of combined pollution witll heavymetals in soil.

Sources, distribution, behavior, and detection techniques of microplastics in soil: A review

In recent years, the problem of environmental pollution caused by microplastics has attracted widespread attention. This paper reviews the latest research progress in terms of the source, content and distribution characteristics, harm, and detection technology of soil microplastics by referring to the relevant literature on soil microplastics worldwide. It concludes that:(1) Existing studies worldwide have detected the presence of microplastics in soil, water, and atmosphere, and the use of agricultural films, sewage sludge,and other man-made activities are the main sources of microplastics in soil;(2) microplastics can adsorb heavy metals, persistent organic pollutants and antibiotics in soil, change the physical and chemical properties of soil. This will result in composite pollution and harm to the ecosystem;(3) microplastics in soil not only can destroy the activity of key soil microorganisms, but also enter the body of crops and soil animals, affecting normal growth of crops and soil animals, and further threaten human health;(4) at present, there is no unified operating standard for the sampling, processing, and detection process of microplastics. Analysis methods such as visual inspection, spectroscopy, and thermal analysis have both advantages and disadvantages, and emerging detection technologies require urgent development.Microplastics have become a new pollutant in soil and their distribution characteristics are closely related to human activities. They pollute the environment and threaten human health through the food chain.Although related research on soil microplastics has just begun, it will become the focus of research in the future.

Atmospheric Deposition-Carried Pb, Zn, and Cd from a Zinc Smelter and Their Effect on Soil Microorganisms

Dust emissions from smelters, as a major contributor to heavy metal contamination in soils, could severely influence soil quality. Downwind surface soils within 1.5 km of a zinc smelter, which was active for 10 years but ceased in 2000, in Magu Town, Cuizhou Province, China were selected to examine Pb, Zn, and Cd concentrations and their fractionation along a distance gradient from a zinc smelter, and to study the possible effects of Pb, Zn, and Cd accumulation on soil microorganisms by comparing with a reference soil located at a downwind distance of 10 km from the zinc smelter. Soils within 1.5 km of the zinc smelter accumulated high levels of heavy metals Zn （508 mg kg^-1）, Pb （95.6 mg kg^-1）, and Cd （5.98 mg kg^-1） with low ratios of Zn/Cd （59.1-115） and Pb/Cd （12.4-23.4）. Composite pollution indices （CPIs） of surface soils （2.52-15.2） were 3 to 13 times higher than the reference soils. In metal accumulated soils, exchangeable plus carbonate-bound fractions accounted for more than 10% of the total Zn, Pb, and Cd. The saturation degree of metals （SDM） in soils within 1.5 km of the smelter （averaging 1.25） was six times higher than that of the reference soils （0.209）. A smaller soil microbial biomass was found more frequently in metal accumulated soils （85.1-438 μg C g^-1） than in reference soils （497 μg C g^-1）, and a negative correlation （P 〈 0.01） of soil microbial biomass carbon to organic carbon ratio （Cmic/Corg） with SDM was observed. Microbial consumption of carbon sources was more rapid in contaminated soils than in reference soils, and a shift in the substrate utilization pattern was apparent and was negatively correlated with SDM （R = -0.773, P 〈 0.01）. Consequently, dust deposited Pb, Zn, and Cd in soils from zinc smelting were readily mobilized, and were detrimental to soil quality mainly in respect of microbial biomass .

Study on the Urbanization Process of Kunming City and Its Impact on the Water Environment of Dianchi Lake

[ Objective] We aimed to analyze the urbanization process of Kunming City and its impact on the water environment of Dianchi Lake. [ Method ] Using the Analytic Hierarchy Process （AHP）, we assessed the urbanization leve of Kunming in 1998 -2008 based on composite indicator evaluation system. Afterwards, we calculated water pollution composite index of Dianchi Lake and introduced the EKC to set up a coupling relation- ship model between the urbanization level and water environment quality. [ Result] During 1998 -2008, the urbanization level of Kunming increased gradually, that is, it was lower than 30.0% before 2002, with slow growth; at the later stage, it grew fast, and reached 75.0% in 2008. Water pol- lution composite index of Dianchi Lake showed that Dianchi Lake was polluted seriously, especially Caohai. From the EKC, we can see that the re- lationship curves between the urbanization level of Kunming and water pollution composite index of Dianchi Lake were akin to inversed U shapes and still at an antagonistic stage at present. [ Condusion] The research could provide scientific references for discussing the relationship between urban- ization process and water environment.

STUDY ON THE CHEMICAL CHARACTERISTICS OF POLLUTING FOG IN GUANGZHOU AREA IN SPRING

Samples of fog water collected in the area of Guangzhou during February, March and April of 2005 are used in this work to study the chemical composition of fog water in polluting fog there. Three typical episodes of polluting fog are analyzed in terms of ionic concentration and their possible sources. It is found that the concentration of various ions in fog water is much higher than those in rainwater. Fog not only blocks visual range but contains liquid particles that result in high degree of pollution and are very harmful to human health. SO4= is the anion with the highest concentration in fog water, followed by NO3-. For the cation, Ca++ and NH4+ are the highest in concentration. It is then known that rainwater is more acidic than fog water, indicating that ionic concentration of fog water is much higher than that of rainwater, but there are much more buffering materials in fog water, like NH4+ and Ca++. There is significant enrichment of Ca++, SO4=, and Mg++ in fog water. In the Guangzhou area, fog water from polluting fog is mainly influenced continental environment and human activity. The episodes of serious fog pollution during the time have immediate relationships with the presence of abundant water vapor and large amount of polluting aerosol particles.

Fabrication of Bi_2O_3/TiO_2nanocomposites and their applications to the degradation of pollutants in air and water under visible-light

A nanoheterojunction composite photocatalyst Bi2O3/TiO2 working under visible-light （λ≥ 420 nm） was prepared by combining two semiconductors Bi2O3 and TiO2 varying the Bi2O3/TiO2 molar ratio. Maleic acid was employed as an organic binder to unite Bi2O3 and TiO2 nanoparticles. The SEM, TEM, XRD and diffuse reflectance spectra were utilized to characterize the prepared Bi2O3/TiO2 nanoheterojunction. The nanocomposite exhibited unusual high photocatalytic activity in decomposing 2-propanol in gas phase and phenol in aqueous phase and, evolution of CO2 under visible light irradiation while the end members exhibited low photocatalytic activity. The composite was optimized to 5 mol% Bi2O3/TiO2. The remarkable high photocatalytic efficiency originates from the unique relative energy band position of Bi2O3 and TiO2 as well as the absorption of visible light by Bi2O3.

A vehicle-mounted dual-smog chamber:Characterization and its preliminary application to evolutionary simulation of photochemical processes in a quasi-realistic atmosphere

Smog chambers are the effective tools for studying formation mechanisms of air pollution.Simulations by traditional smog chambers differ to a large extent from real atmospheric conditions,including light,temperature and atmospheric composition.However,the existing parameters for mechanism interpretation are derived from the traditional smog chambers.To address the gap between the traditional laboratory simulations and the photochemistry in the real atmosphere,a vehicle-mounted indoor-outdoor dual-smog chamber(JNUVMDSC)was developed,which can be quickly transferred to the desired sites to simulate quasi-realistic atmosphere simultaneously in both chambers using“local air”.Multiple key parameters of the smog chamber were characterized in the study,demonstrating that JNUVMDSC meets the requirements of general atmospheric chemistry simulation studies.Additionally,the preliminary results for the photochemical simulations of quasi-realistic atmospheres in Pearl River Delta region and Nanling Mountains are consistent with literature reports on the photochemistry in this region.JNU-VMDSC provides a convenient and reliable experimental device and means to study the mechanism of atmospheric photochemical reactions to obtain near-real results,and will make a great contribution to the control of composite air pollution.