Study of Leakage Current Behaviour on Artificially Polluted Surface of Ceramic Insulator

This paper presents the results of the study concerning to the leakagecurrent behaviour on artificially polluted ceramic insulator surface. From the present study it wasobserved that there is a reasonably well-defined inception of current i.e. scintillations at afinite voltage, The corresponding voltages for extinction of the current are in the range of 0.8 kVto 2.1 kV. Obviously, the dry band formed in the immediate vicinity of the pin prevents smoothcurrent flow as the voltage rises from zero. Only when the voltage is adequate it causes a flashoverof the dry band and current starts flowing. As is common in similar current extinction phenomena,here also, the extinction voltages are significantly lower than the inception voltages. Further, thevoltage-current curves invariably show hysteresis - the leakage currents are lower in the reducingportion of the voltage. This is obviously due to drying of the wet pollutant layer therebyincreasing its resistance. It is believed that this is the first time that such a directquantitative evidence of drying in individual half cycles is experimentally visualized.

Examination of Surface Water Along River-Rima Floodplain in Wamakko, Sokoto State, Nigeria

This study examined the hydrochemistry of surface water along the River-Rima floodplain area.Five sampling locations were purposively selected,and,in each point,three samples were taken from surface water(river).The sampling was repeated after 20 days.Thus,a total of 30 samples were collected.Water samples obtained were subjected to laboratory tests.Results revealed that BOD,TDS,Mg2+,and Fe3+are above the World Health Organization(WHO)and Standard Organization of Nigeria(SON)reference guidelines for drinking water quality.Isolates detected from the coliform bacteriological analysis include Enterobacter aerogene,Escherichia coli,and Citrobacter freundii with most of the samples showing coliform bacteria growth above the SON standard for drinking water.Hence,the water in the River-Rima floodplain of the Wamakko area is of low quality and unsafe for drinking.Results of principal component analysis(PCA)revealed external influences such as pollutant wash off and rock weathering as controls on hydrochemistry of surface water.There is some indication of anthropogenic inputs(Cl-,NO3-,and PO42-)based on hierarchical cluster analysis.Elements including Cl-,NO3-,and PO42-are increasingly added into surface water from human activities,mainly agriculture,and municipal sewage.

Fast spreading of surface ozone in both temporal and spatial scale in Pearl River Delta

Surface ozone(O_(3))is a major air pollutant and draw increasing attention in the Pearl River Delta(PRD),China.Here,we characterize the spatial-temporal variability of ozone based on a dataset obtained from 57 national monitoring sites during 2013-2019.Our results show that:(1)the seasonal difference of ozone distribution in the inland and coastal areas was significant,which was largely affected by the wind pattern reversals related to the East Asian monsoon,and local ozone production and destruction;(2)the daily maximum 8hr average(MDA8 O_(3))showed an overall upward trend by 1.11 ppbv/year.While the trends in the nine cities varied differently by ranging from-0.12 to 2.51 ppbv/year.The hot spots of ozone were spreading to southwestern areas from the central areas since 2016.And ozone is becoming a year-round air pollution problem with the pollution season extending to winter and spring in PRD region.(3)at the central and southwestern PRD cities,the percentage of exceedance days from the continuous type(defined as≥3 days)was increasing.Furthermore,the ozone concentration of continuous type was much higher than that of scattered exceedance type(<3 days).In addition,although the occurrence of continuous type starts to decline since2017,the total number of exceedance days during the continuous type is increasing.These results indicate that it is more difficult to eliminate the continuous exceedance than the scatter pollution days and highlight the great challenge in mitigation of O_(3)pollution in these cities.

Characteristics of water contamination in abandoned coal mines:a case study on Yudong River area,Kaili,Guizhou Province,China

The seasonal and spatial changes in the chemical composition of the water in abandoned mine drainages and rivers in Yudong River area in the years of 2017-2018 were analyzed.The effects of mine water drainage on the seasonality and physicochemical properties of the river water after mine closure were evaluated,and the feasibility of irrigation using river water and the degree of pollution to farmland were assessed using the Water Quality Standard for Farmland Irrigation.The results show that the mine water has low pH value(<3.5-4)and high levels of total hardness,SO_(4)^(2−),Fe,Al,and Zn.In addition,the pH of the mine water is negatively correlated with the presence of other metal ions.The correlation coefficient between the chemical oxygen demand(COD)and Fe reached 0.989.While the pollution levels of Pinglu and Baishui rivers were low,the confluence region of the two rivers was seriously polluted.However,only the levels of Fe and Cd slightly exceeded the Surface Water Environmental Quality Standard after the confluence of Yudong and Chongan rivers.Overall,the heavy pollution type of the confluent river is consistent with mine water pollution.The water quality is slightly better in the dry season compared than in the high-water period.Sulfate and Fe content decreased by 39 and 16 mg/L,respectively,and Cd content decreased two-fold.Despite these findings,this study shows that from 2017 to 2018,the pH and Cd content of the rivers at the confluence exceeded the irrigation limit and the water quality continued to deteriorate,which may pose a soil contamination risk.Long-term use of the river for irrigation water may cause toxic elements such as Cd,Fe,Mn,SO_(4)^(2−),Al,and F-to enter the food chain,thereby endangering the life and health of villagers in Yudong River area.

Effects of Poisonous and Harmful Elements Brought about by Coal Mining on Water Environment in Zibo Coal Mine, Shandong Province, China

Coal resources are very abundant in Zibo, Shandong Province, China. A lot of mining sewages are discharged during the coal mining. The mining sewage is characterized by high ρ (SO 2- 4 ), hardness and totally dissolved solids (TDS). Mining sewage in the southern Zibo is acidic, where heavy metals and benzene are detected. The Xiaofu River is polluted when mining sewage flows into it, so that the Mengshan Reservoir is polluted by Xiaofu River. The groundwater is polluted in Zichuan by the leaking of the Xiaofu River. The polluted Xiaofu River is thus used to irrigate the farmland in Mashang Mengshui zone. The irrigation water affects the quality of shallow groundwater. The laboratory soil column test shows that SO 2- 4, Cl -, Ca 2+ and Mg 2+ can migrate through vadose soil, especially SO 2- 4 and Cl -.

Distribution and assessment of heavy metals in the surface sediment of Yellow River, China

Large amounts of heavy metals discharged by industrial cities that are located along the middle reach of Yellow River, China have detrimental impacts on both the ecological environment and human health. In this study, fourteen surface sediment samples were taken in the middle reach of the Yellow River. Contents of Zn, Pb, Ni, Cu, Cr, Cd, As were measured, and the pollution status was assessed using three widely used pollution assessment methods, including the single factor index method, Nemerow pollution index method and potential ecological risk index. The concentrations of the studied heavy metals followed the order： Zn 〉 Cr 〉 Cu 〉 Ni 〉 Pb 〉 As 〉 Cd. Nearly 50% of sites had Cu and Cr accumulation. The concentration of Cu at the Yiluo River exceeded the secondary standard value of the Environmental quality standard for soils. Comparison of heavy metal concentrations between this study and other selected rivers indicated that Cu and Cr may be the major pollutants in our case. The single factor index indicated that many samples were at high levels of pollution for Cu and Cd; the Nemerow pollution index indicated that the Yihe River, Luohe River, Yiluo River and Huayuankou were polluted. According to the results of potential ecological risk assessment, Cd in the tributaries of Luo River, Yihe River,and Yiluo River showed high risk toward the ecosystem and human health, Cd in Huanyuankou and Cu in Yiluo River showed a middle level of risk and other samples were at a low level of risk.

Field scale interaction and nutrient exchange between surface water and shallow groundwater in the Baiyang Lake region,North China Plain

Fertilizer input for agricultural food production, as well as the discharge of domestic and industrial water pollutants, increases pressures on locally scarce and vulnerable water resources in the North China Plain. In order to：（a） understand pollutant exchange between surface water and groundwater,（b） quantify nutrient loadings, and（c） identify major nutrient removal pathways by using qualitative and quantitative methods, including the geochemical model PHREEQC） a one-year study at a wheat（Triticum aestivum L.） and maize（Zea mays L.） double cropping system in the Baiyang Lake area in Hebei Province, China, was undertaken. The study showed a high influence of low-quality surface water on the shallow aquifer. Major inflowing pollutants into the aquifer were ammonium and nitrate via inflow from the adjacent Fu River（up to 29.8 mg/L NH4-N and 6.8 mg/L NO3-N）, as well as nitrate via vertical transport from the field surface（up to 134.8 mg/L NO3-N in soil water）. Results from a conceptual model show an excess nitrogen input of about 320 kg/ha/a. Nevertheless,both nitrogen species were only detected at low concentrations in shallow groundwater,averaging at 3.6 mg/L NH4-N and 1.8 mg/L NO3-N. Measurement results supported by PHREEQC-modeling indicated cation exchange, denitrification, and anaerobic ammonium oxidation coupled with partial denitrification as major nitrogen removal pathways. Despite the current removal capacity, the excessive nitrogen fertilization may pose a future threat to groundwater quality. Surface water quality improvements are therefore recommended in conjunction with simultaneous monitoring of nitrate in the aquifer, and reduced agricultural N-inputs should be considered.

Nitrogen removal from summer to winter in a field pilot-scale multistage constructed wetland-pond system

A pilot-scale multistage constructed wetland-pond(MCWP)system with a"pre-ecological oxidation pond,two-stage horizontal subsurface flow constructed wetland(HSCW)and surface flow constructed wetland(SFCW)as the core and postsubmerged plant pond"as the process was used to treat actual polluted river water in the field,and the variation in nitrogen removal from summer to winter was investigated.The results showed that the average total nitrogen(TN)removal efficiency in the MCWP was approximately 40.74%.The significant positive correlation between the daily highest temperature and the TN removal efficiency of the whole system was fitted with a nonlinear curve(R^(2)=0.7192).The TN removal load rate in the HSCWs was 2.7–3.7 times that in the SFCW.The SFCW,which had high-density plants(35 plants/m^(2)),increased the proportion of nitrogen removed by plant harvesting and microbial function.The TN transformed by Iris pseudacorus L.accounted for 54.53%in the SFCW.Furthermore,bacteria completed the nitrogen cycle in the SFCW through a variety of nitrogen removal pathways.This research not only investigated the TN removal performance in an MCWP system but also made it possible to predict the TN removal efficiency according to the daily highest temperature from summer to winter in the field.