Wet Deposition Fluxes and Related Atmospheric Chemistry at Three Sites in Mexico

Wet deposition was collected in Mexico City (MC), Metropolitan Area of Monterrey (MAM) and El Chico National Park (ECNP), during 2009 and 2010. pH, conductivity, Cl-, , Na+, K+, Ca2+ and Mg2+ were determined. In MC, sulphate levels were greater than nitrate levels, and NH4 had mixed sources (vehicular emissions and agriculture activities). MAM had markedly alkaline atmospheric deposition, Na+ and Cl-levels were unexpectedly high, especially during hurricane “Alex”. Low pH values were found in ECNP and nitrate concentrations were high, suggesting the influence of a local source (forest fires). Deposition fluxes (Kg.ha-1yr-1) for N-NO3, N-NH4 and S-SO4 were 1.36, 2.74 and 4.84 for MAM;7.27, 0.57 and 4.32 for ECNP;and 5.97, 4.96 and 6.78 for MC, respectively. Nitrogen deposition fluxes in ECNP were high considering that this site is a natural reserve.

Annual Fluxes of Heavy Metal Elements in Atmospheric Dry and Wet Depositions in the Pearl River Delta Economic Region, Guangdong Province

There are 158 sampling points to be set up in the Pearl River delta economic region. The collecting period is mostly one year, namely, from July 2007 to July 2008. The eight heavy metal elements of Cr, Ni, Cu, Pb, Zn, As, Hg, and Cd in 474 dry and wet deposition samples were tested in terms of the standard procedures. Their average annual fluxes have no obvious difference between dry deposition and wet deposition. So these elements might be at an equilibrium or quasi-equilibrium state between dry deposition and wet deposition.

A four-year investigation on wet deposition in western Thailand

The investigation of pH variation and the chemical composition of rainwater have been studied from April 2003 to October 2006 at a rural area of Nakorn Pathom Province, western Thailand. The pH value ranged from 4.0 to 7.8 with an average of 6.1. Out of 319 rain events, 72 events were observed in acidic range （pH 〈 5.6）. The pH of rainwater gradually increased over the sampling period. The volume-weighted mean concentrations （ixeq]L） of ion species followed the order： Ca^2＋ 〉 NH4^＋ 〉 SO4^2- 〉 HCO3^- 〉 NO3^- 〉 Na^＋ 〉 Cl^- 〉 CH3COO^- 〉 Mg^2＋ 〉 K^＋ 〉 H^＋ 〉 HCOO^- 〉 PO4^3-. Neutralization factor calculations reveal that Ca^2＋ plays a major role in neutralization processes in this area. Enrichment factor calculations indicate that SO4^2-, K^＋, Ca^2＋ and Mg^2＋ were originated from non-marine sources. The statistical measure principle component analysis indicates influence of various local emission sources e.g., soil, limestone mines, biomass burning and agricultural emissions, on the chemical composition of rainwater.

Fabrication of Nanoscale Step Height Structure Using Atomic Layer Deposition Combined with Wet Etching

The current techniques used for the fabrication of nanosteps are normally done by layer growth and then ion beam thinning. There are also extra films grown on the step surfaces in order to reduce the roughness. So the whole process is time consuming. In this paper, a nanoscale step height structure is fabricated by atomic layer deposition （ALD） and wet etching techniques. According to the traceable of the step height value, the fabrication process is controllable. Because ALD technology can grow a variety of materials, aluminum oxide （Al2O3） is used to fabricate the nanostep. There are three steps of Al2O3 in this structure including 8 nm, 18 nm and 44 inn. The thickness of Al2O3 film and the height of the step are measured by anellipsometer. The experimental results show that the thickness of Al2O3 film is consistent with the height of the step. The height of the step is measured by AFM. The measurement results show that the height is related to the number of cycles of ALD and the wet etching time. The bottom and the sidewall surface roughness are related to the wet etching time. The step height is calibrated by Physikaliseh-Technische Bundesanstalt （PTB） and the results were 7.5±1.5 nm, 15.5±2.0 nm and 41.8±2.1 nm, respectively. This research provides a method for the fabrication of step height at nanoscale and the nanostep fabricated is potential used for standard references.

Estimation of the Total Dust Column and Dry Deposition Flux over the Yellow Sea,China Based on Shipboard Sun Photometer Measurements:Case Study

The total dust column and the dry deposition flux were calculated based on the optical properties that were measured by a shipboard sun photometer POM-01 MK II in a cloud-free and nonfrontal dust condition on 24 April 2006. The total dust column was calculated by using an integration method of the particle size distribution; the mean value was 1.42±0.30 g m 2. A linear correlation between the total dust column and the aerosol optical depth （AOD） with a linear factor of 2.7 g m 2 over the Sahara was applied to calculate the total dust column in this study; the results were lower than these calculated by the integration method. A reasonable factor of 3.2 g m^-2 was achieved by minimizing the standard deviation （SD） of the two methods. The two layers model, which includes the deposition processes of turbulent transfer, Brownian diffusion, impaction and gravitational settling over the sea＇s surface, was used to calculate the dry deposition flux; the mean value was 5.05±2.49 μg m^-2 s^-1. A correlation among the total dust column, dry deposition flux, AOD, and effective radius was discussed. The correlation between the total better than that between dust column and the AOD was the total dust column and the effective radius; however, the correlation between the dry deposition flux and the effective radius was better than that between the dry deposition flux and the AOD.

Simulated seasonal variations in nitrogen wet deposition over East Asia

The regional air quality modeling system Regional Atmospheric Modeling System–Community Multiscale Air Quality was applied to estimate the spatial distribution and seasonal variation in nitrogen wet deposition over East Asia in 2010. The simulated results were evaluated by comparing modeled precipitation rates and ion concentrations, such as ammonium（NH_4~＋）, nitrate（NO_3^-）, and sulfate, in rainwater, against observations obtained from Acid Deposition Monitoring Network in East Asia and meteorological stations in China. Comparison of simulated and observed precipitation showed that the modeling system can reproduce seasonal precipitation patterns reasonably well. For major ion species, the simulated results in most cases were in good agreement with those observed. Analysis of the modeled wet deposition distributions indicated that China experiences noticeable variation in wet deposition patterns throughout the year. Nitrogen wet deposition（NH_4~＋ ＋ NO_3^-） during summer and spring accounted for 71% of the annual total（3.9 Tg N yr^（-1））, including 42.7% in summer. Precipitation plays a larger role in the seasonal variation of wet deposition; whereas, aerosol concentrations affect its distribution patterns. In China, the amount of annual nitrogen wet deposition ranged from 1 to 18 kg N ha^（-1）. Nitrogen in wet deposition was mainly in the form of NH_4~＋, accounting for 65.76% of the total amount, and the molar ratio of NH_4~＋∕NO_3^- was mostly more than 1, indicating a relatively larger effect from agricultural activities.

Influence of nitrogen wet deposition on nitrogen output in a typical watershed in the Three Gorges Reservoir Area

In order to explore the influence of wet nitrogen(N)deposition on N output in watersheds,this study selected a typical small watershed(Chenjiagou,CJG)in the Three Gorges Reservoir(TGR)area based on one-year observation of rainfallrunoff N forms.Characteristics and sources of N output were clarified by chemical statistics and isotopic abundance,and the contribution of N deposition to the N output was quantified by the output coefficient method.The N flux of wet deposition was estimated at 18.53 kg N ha^(-1) yr^(-1),and originated mostly from agricultural activities.Watershed N was significantly accumulated from upper to lower reaches due to frequent human activities.Seasonal changes of riverine N were strongly affected by chemical fertilizer,with the highest concentration in spring and the lowest in winter.Nitrate was mainly derived from chemical fertilizer,accounting for 38.83% of all sources.N concentration in processes of different rainfall events had a hysteresis effect corresponding to the flow rate.Three rainfall events greatly changed DTN(Dissolved total N)outputs:rainstorm caused 91.26 kg DTN output,which was 11 times that of moderate rain(8.46 kg)and 4 times that of heavy rain(20.80 kg).N deposition contributed 19.89% of riverine N output in the watershed.The results can provide theoretical support for the control of N pollution in the TGR area.

Simulating Dry Deposition Fluxes of PM_(10) and Particulate Inorganic Nitrogen over the Eastern China Seas During a Severe Asian Dust Event Using WRF-Chem Model

A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March, 2002. The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom. The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system. The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event, respectively. However, the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea. Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March. The dust plume arrived in the Yellow Sea on 20 March, decreasing the particulate inorganic nitrogen in mass concentration accordingly. The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival, respectively. In contrast, when the dust plume crossed over the Yangtze Delta area, it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea, where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival.

Study of Trace Ions in Wet Deposition of an Industrial Site in Monterrey’s Metropolitan Area, Mexico

The chemistry of rainwater has been subject to numerous investigations during the last two decades due to the increase of environmental problems caused by the acid deposition. The present study focuses on one aspect of air pollution, the chemical composition of wet deposition of an industrial zone. The sampling period was from March to December 2009. The station was located on the roof of the Chemistry School at the University of Nuevo León, an area in the north of Monterrey where the majority of pollution is generated. Twenty-five wet precipitation samples were collected with an automatic sampler and analyzed for pH, ions (, , Cl-, Ca2+, Mg2+, Na+, K+) and conductivity. The results show that the average pH is higher than 5.6;the characteristics of the rainwater studied are of alkaline nature due to the values of pH found;there is an evident anthropogenic source contributing to the alkaline of rain water. In order to find possible association between ions and consequently the possible sources of pollutants correlation study was applied using the program SPSS v.12. Good correlations were found between ions and along with Ca2+ and Mg2+. The local extraction industry and surrounding aerosols might be causing of alkaline rain which may be due to the neutralization effect of particulate matter. This study represents a continuation of the studies of rainwater chemistry in the Northeast of Mexico.

Wet deposition and scavenging ratio of air pollutants during an extreme rainstorm in the North China Plain

Atmospheric wet deposition plays an important role in the supply of nutrients and toxic substances to terrestrial and aquatic environments. Although long-term（e.g. annual, multi-year） wet deposition is recorded well, pronounced and short-term changes in precipitation chemistry are less well investigated. In the present study, the precipitation chemistry and scavenging ratio of air pollutants were observed during an extreme torrential rain event（325.6 mm at the observation site） that occurred over 19–21 July 2016 in the North China Plain（NCP）. The scavenging ratio of particles showed a similar spatial distribution to that of the precipitation amount in the NCP, indicating the efficient removal of particulate matter due to the large amount and precipitation intensity of the storm. In addition, the scavenging ratio of water soluble ions was larger than that of organics and gaseous pollutants such as SO_2 and NO_2, likely due to their differences in water solubility.Consequently, raindrops incorporated more aerosol sulfate than gaseous compounds. Due to the heavy precipitation amount, almost all species in rainwater during this storm showed their lowest concentration but the highest flux compared with other rain events, indicating an important role played by this storm in terms of the substances received by the terrestrial and marine ecosystems of the region. However, the contribution of this storm to the annual chemical flux was lower than that of precipitation amount, indicating that the atmospheric compounds were scavenged below-cloud first and were then diluted by the cloud/rainwater. Future studies are needed in the context of the occurrence of extreme rainfall events in the NCP from the perspective of climate variability.

Effects of process parameters on the depth-to-width ratio of flux-cored wire underwater wet welding

The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.

External Influence to Geochemical Assessment of the Land Quality—Atmospheric Dry and Wet Deposition

The heavy metals in the atmosphere mainly come from the gas and dust which involved by the energy costs,transport,metallurgy and building materials production.Other than the element of Hg,the heavy metals come into the atmosphere in the form of aerosol basically and go into the soil through

Regional pattern of mercury wet deposition in Beijing

The regional pattern of mercury were deposition in Beijing was studied. The Hg concentrations in precipitation were detected in 0—0.83 ng/ml(summer) and in 0.371—1.73 ng/ml(winter), under extreme condition up to 3.4 ng/ml in heating periods. The sum of Hg wet deposition was 101.52 μg/(m 2·a) within Nov. 1994— Nov. 1995 and 123.09 μg/(m 2·a) within Nov. 1995 — Nov. 1996. The more precipitation fall down, the more Hg was removed from atmosphere, especially in heating periods. Burning coal for heating was thought as the reason of a baseline seasonable with highest Hg levels in winter. The Hg concentration in rainfall decreased with the raining duration, which clearly shows the efficiency of washouting Hg by wet deposition.

Simulation Study of Heat Flux Deposition Pattern on the Surface of HT-7 Toroidal Limiters

The heat flux deposition pattern on the toroidal limiters installed in HT-7 was simulated with ANSYS code. The simulation model was established with the ripple of the magnetic field. The heat deposition pattern and temperature distribution on the surface of the toroidal linfiters were obtained. A comparison of the results obtained with and without the shaped tiles, used to reduce the heat flux on the leading edge of the limiters, was made. The maximum heat load allowed at the leading edge was about 1.8 MW/m2 because of the poor power removing capacity on the ends of the limiters. This approach can also be applied to other devices with a limiter configuration in a circular cross-section shape.

Wetting behavior of CaO-Al_(2)O_(3)-based mold flux with various BaO and MgO contents on the steel substrate

The Interfacial phenomena in mold have a great impact on the smooth operation of continuous casting process and the quality of the casting product.In this paper,the wetting behavior of CaO-Al_(2)O_(3)-based mold flux with different BaO and MgO contents was studied.The results showed that the contact angle between molten flux and interstitial free(IF)steel substrate increased from 62.4°to 74.5°with the increase of BaO content from 3 wt%to 7 wt%,while it decreased from 62.4°to 51.3°with the increase of MgO content from 3 wt%to 7 wt%.The interfacial tension also increased from 1630.3 to 1740.8 mN/m when the BaO content increased,but it reduced from 1630.3 to 1539.7 mN/m with the addition of MgO.The changes of contact angle and interfacial tension were mainly due to the fact that the bridging oxygen(O^(0)) at the interface was broken into non-bridging oxygen(O^(-)) and free oxygen(O_(2-)) by MgO.However,more O^(-) and O_(2-) connected into O^(0) when BaO was added,since the charge compensation effect of BaO was so stronger that it offset the effect of providing O_(2-).

Chemical Composition, Fluxes and Seasonal Variation of Acid Deposition in Carmen Island, Campeche, Mexico

Two hundred and seven rain events from April to October 2012 were collected in Carmen Island, Campeche, Mexico, and the concentration of 8 major ions with the pH of the rainwater was analyzed. Chemical composition variations as a result of seasonal patterns, meteorological conditions, and mixed local and regional sources contribution were assessed. In spite of the fact that nitrate and sulfate levels were higher than background hemispheric values, the average pH values were almost neutral. Carmen Island was under the influence of both, local and long-range transported emissions. Chemical composition showed a dilution effect as a result of the monthly rainfall amount. Ca2+ and Na+ were the most abundant ions, and these ions acted as acid neutralizers and buffered the acidity of the rain, suggesting that marine and crustal aerosols played an important role in the acid-base interactions. Wet deposition fluxes obtained were compared with reference values proposed as critical loads, fluxes obtained in this study did not exceed the critical values reported for sensitive ecosystems in Europe, indicating that this site has yet enough capacity to support acidity, nitrogen and sulfur deposition. However, it is necessary to obtain reference values characteristics for tropical regions.

Study on the Characteristics of Atmospheric Dry and Wet Deposition in the Upper Reaches of Baiyangdian

To study the characteristics of atmospheric dry and wet deposition in the upper reaches of Baiyangdian,two sampling sites in Baoding City were monitored for 1 year from September 2018 to August 2019.The results showed that the dry and wet deposition fluxes of total nitrogen(TN)during the monitoring period were 6.87 and 6.46 kg/(hm^(2)·a),respectively.The ratio of wet to dry deposition of TN was approximately 1∶1,with wet deposition being dominated by ammonium nitrogen deposition.The dry and wet deposition fluxes of total phosphorus(TP)were 0.228 and 0.125 kg/(hm^(2)·a),and it was dominated by dry deposition.The average concentration of TN in wet deposition exceeded the standard threshold for eutrophic waters,and its ecological effects on the Baiyangdian basin should be concerned.Wet deposition fluxes of nitrogen and phosphorus had a significantly positive correlation with rainfall,while their deposition concentrations were negatively correlated with rainfall.The dry deposition of atmospheric nitrogen and phosphorus was influenced by the amount of dustfall and climatic factors such as rainfall,temperature,and humidity,which mainly occurred from April to August.

Dissolved organic carbon fractionation in wet deposition and its potential impact on radiative forcing in the central Tibetan Plateau

As an important component of carbonaceous matters,dissolved organic carbon(DOC)can absorb and scatter the solar radiation at ultraviolet and blue wavelengths.The wet deposition process has great impact on the con-centration and light absorption ability of precipitation DOC,affecting the climatic effect caused by DOC in the atmosphere.In this study,light absorption and fluorescence characteristics of precipitation DOC was investigated in the central Tibetan Plateau(TP).The results showed that the mean DOC concentration and mass absorption cross-section measured at 365 nm(MAC_(365)) in Tanggula(TGL)station were 0.59±0.42 mg/L and 0.37±0.19 m^(2)/g,respectively,while both values showed much higher volatilities than those of aerosols.DOC concentrations had significant negative correlation with the precipitation amount,while MAC_(365) values increase with the precipitation amount in TGL station.Therefore,DOC with high light-absorbing ability was preferred to be retained in the atmosphere during wet deposition.In this study,precipitation DOC contained three fluorescent components(one humic-like component and two tyrosine-like components)mainly from local biomass burning sources.DOC concentration showed a negative relationship with MAC_(365) value in TGL station.The wet deposition of DOC with low light-absorbing ability can reduce the strong negative radiative forcing caused by secondary organic aerosol due to high proportion of DOC in secondary organic carbon.Similar phenomenon was also found in Nam Co,Lulang and Everest stations of previous study,which may have a potential impact on radiative forcing in the atmosphere of TP.

Dated deposition couplets link catchment erosion flux with storm discharge on the Chinese Loess Plateau

Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.

Catalytic wet oxidation of aniline over Ru catalysts supported on a modified TiO_2

The catalytic wet air oxidation of aniline over Ru catalysts supported on modified Ti 2 （Ti 2, Ti0.9Ce0.1O2, Ti0.9Zr0.1O2） is investigated. A series of characterization techniques are conducted to determine the relationship between the physico-chemical properties and the catalytic performance. As a result of the good metal dispersion and large number of surface oxygen species, the Ru/Ti0.9 Zr0.1O2 catalyst presents the best catalytic activity among the tested samples. The effects of the operating conditions on the reaction are investigated and the optimal reaction conditions are determined. Based on the relationship between the by-products concentration and the reaction time, the reaction path for the catalytic oxidation of aniline is established. Carbonaceous deposits on the surface of the support are known to be the main reason for catalyst deactivation. The catalysts maintain a constant activity even after three consecutive cycles.