Current status and prospects of research on 1,4-dioxane pollution and treatment technologies in the water environment

1,4-dioxane pollution is characterized by its early identification, widespread sources and extensive distribution. The pollutant is highly mobile and persistent in the water environment and is classified as a B2(probable) human carcinogen. After reviewing recent researches on the pollution status,transport and transformation characteristics of 1,4-dioxane in the water environment, as well as the environmental pollution remediation and treatment technologies, and the status of environmental regulation,this paper addresses that the distribution of 1,4-dioxane in water bodies is significantly correlated with chlorinated hydrocarbon pollutants such as 1,1,1-trichloroethane(1,1,1-TCA) and trichloroethylene(TCE).It is noteworthy that 1,4-dioxane often occurs in symbiosis with 1,1,1-TCA and has a similarity contamination plume distribution to 1,1,1-TCA. The natural attenuation of 1,4-dioxane in groundwater environment is weak, but there is a certain degree of biological oxidation attenuation. Current methods for treating 1,4-dioxane pollution mainly include extraction-treatment technology, advanced oxidation treatment technology, modified biological treatment technology and phytoremediation technology, all of which have their limitations in practical application. Currently, there is no environmental regulation available for the 1,4-dioxane pollution worldwide, and no enforceable standard established for defining the health trigger levels of 1,4-dioxane in drinking water. Research on this contaminant in China is generally limited to the site or laboratory scale, and there are no studies on the environmental risk and quality standards for 1,4-dioxane in the water environment.

Evolutionary trend of water cycle in Beichuan River Basin of China under the influence of vegetation restoration

The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected area.Magnetic data(n=84)measured,processed and interpreted as qualitative and quantitatively.The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies.The magnetic values ranged from-137 nT to 2345 nT with a mean of 465 nT.Reduction to equator shows significant shifting of causative bodies in the southern and northern directions.Analytical signal map shows exact boundary of granitic bodies.Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines.Sudden decrease of magnetic values from 2042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence.Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well.Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m,respectively.Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0,1,2,and 3 and found depth ranges from<10 m to>90 m.Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.

Comparison of 1,2,3-Trichloropropane reduction and oxidation by nanoscale zero-valent iron, zinc and activated persulfate

Trichloropropane（TCP） is a chlorinated solvent which derives from chemical manufacturing as a precursor, and it is also an important constituent of solvent formulations in cleaning/degreasing operations. The control and remediation of TCP in polluted sites is a challenge for many conventional remediation techniques due to its refractory behaviour. This challenge in mind, some nano-materials and oxidants were tested to evaluate their effectiveness as in TCP degradation in a laboratory setting. Experimental results indicate that the use of nanoscale zero-valent iron prepared by green tea（GT） as a reductant has negligible degradation effect on TCP under normal temperature and pressure conditions. However, zinc powders of similar size but higher surface reactivity, demonstrated stronger dechlorination capacity in the breakdown of TCP, as almost all of TCP was degraded by carboxymethocel（CMC） stabilized nanoscale zinc within 24 h. Activated persulfate by citric acid（CA） and chelated Fe（Ⅱ） was also used for TCP treatment with a TCP removal efficiency rate of nearly 50% within a 24 h reaction period, and a molar ratio of S2O82-, Fe2+ and CA is 20:5:1. Both the reduction and oxidation reactions are in accordance with the pseudo-first order kinetic equation. These results are promising for future use of TCP for the remediation of polluted sites.

Study on detecting spatial distribution availability in mine goafs by ultra-high density electrical method

The purpose of this research is to explore the spatial distribution and influence range of the mined-out area of a coal mine in Hebei Province,the advantages of ultra-high density resistivity method,such as large data volume,high efficiency and high precision,are brought into full play,the abnormal patterns of dislocation and partial drainage area of shallow continuous aquifer caused by subsidence zone are detected,and then the spatial distribution patterns of subsidence and fractures caused by deep mining subsidence zone are deduced,this method not only extends the exploration range of high-density resistivity method in mining subsidence disaster assessment,but also improves the accuracy of measurement,the distribution and influence range of mined-out area are revealed accurately,and good exploration results have been obtained in this project.How to select reasonable geophysical prospecting methods and give full play to the role of geophysical prospecting methods according to the geological characteristics of the study area,this exploration work is not only a good combination of geophysical prospecting methods and actual geological conditions,it also provides a valuable reference version for the exploration work under the same geological conditions.

Predicting the effect of dissolved humic acid on sorption of benzotriazole to biochar

Dissolved organic matter plays a critical role in affecting sorption properties of biochar for organic contaminants.In this study,dissolved humic acid(DHA)as a representative of dissolved organic matter and oak sawdust-derived biochar as a sorbent were prepared and characterized.Roles of DHA in sorption of benzotriazole(BTA),an emerging organic contaminant,to biochar in different electrolyte solutions were investigated.The results revealed the dual roles of DHA in BTA sorption to biochar.On the one hand,DHA can compete for sites and/or block pores available for BTA to inhibit the adsorption of BTA to biochar.On the other hand,the sorbed DHA on biochar can serve as additional partitioning phase to promote the partition of BTA.The finding was in accordance with the site energy distribution analysis of BTA sorption that the site energy of the highest occurring frequency in the DHA-BTA system was lower than that in the DHA-free system(3.41-10.4 versus 13.1-20.1 kJ mol^(−1)).The variation in apparent BTA sorption to biochar affected by DHA was thus a combination of changes in both its partition and adsorption properties.A modified Dual-mode model including the aqueous concentration of DHA was proposed to predict the effect of DHA on BTA sorption to biochar in different electrolyte solutions,which showed good prediction performance with most BTA sorption coefficient(K_(d),L g^(−1))deviations within 0.1 log unit.