Chemical and strontium isotope characterization of rainwater in Beijing,China

Major ion concentrations and Sr isotope ratios (⁸⁷Sr/⁸⁶Sr) were measured in rainwater samples collected at an urban site in Beijing over a period of one year. The pH value and major ion concentrations of samples varied considerably, and about 50% of the rainwater studied here were acidic rain with pH values less than 5.0. Ca²⁺ and NH₄⁺ were the dominant cations in rainwaters and their volume weighted mean (VWM) values were 608 μeq l^?1 (14–1781 μeq l^?1) and 186 μeq l^?1 (48–672 μeq l^?1), respectively. SO₄^2? was the predominant anion with VWM value of 316 μeq l^?1 (65–987 μeq l^?1), next was NO₃^? with VWM value of 109 μeq l^?1 (30–382 μeq l^?1).Using Na as an indicator of marine origin, and Al for the terrestrial inputs, the proportions of sea salt and terrestrial elements were estimated from elemental ratios. More than 99% of Ca²⁺ and 98% of SO₄^2? in rainwater samples are non-sea-salt origin. The ⁸⁷Sr/⁸⁶Sr ratios were used to characterize the different sources based on the data sets of this study and those from literatures. Such sources include sea salts (⁸⁷Sr/⁸⁶Sr～0.90917), soluble soil dust minerals originating from either local or the desert and loess areas (～0.7111), and anthropogenic sources (fertilizers, coal combustion and automobile exhausts). The high concentrations of alkaline ions (mainly Ca²⁺) in Beijing atmosphere have played an important role to neutralize the acidity of rainwater. However, it is worth noting that there is a remarkable acidification trend of rainwater in Beijing recent years.     

Seasonal variation in long-range transported dust to a subtropical islet offshore northern Taiwan: Chemical composition and Sr isotopic evidence in rainwater

We investigated chemical and Sr isotopic composition of monthly rainwater collected on Peng-Chia-Yu (PCY) in northern Taiwan. Rainwater ⁸⁷Sr/⁸⁶Sr ratios, Na/Cl, Ca/Cl, Sr/Cl, Sr/Ca, NH₄/Cl, NO₃/Cl, SO₄/Cl and Na/Sr, showed clear seasonal cycles, reflecting mixture of loess carbonates (high Ca/Sr and more radiogenic ⁸⁷Sr/⁸⁶Sr) and seawater (low Ca/Sr and intermediate ⁸⁷Sr/⁸⁶Sr). Model results showed that the former source contributes up to 45% during the winter monsoon period, but seawater is the dominant Sr source in rainwater (>50%) at other times. Two anomalously low ⁸⁷Sr/⁸⁶Sr values occurred in July and August 1998, coinciding with the Merapi eruption in Indonesia. Air-mass backward trajectories and the geochemical and isotopic compositions in rainwater and Merapi lava (i.e. Ca/Sr = 100 and ⁸⁷Sr/⁸⁶Sr = 0.705400) suggested that the Merapi eruption delivered ash across the western equatorial Pacific to PCY. Aerosols leaching experiments were conducted to examine the impact of the 1998 eruption, demonstrating that only a minor terrestrial signature can be extracted by distilled water, implying rapid dispatch of volcanic gases or high-efficiency dissolution of ash related substance in acidic rains.     

Assessing decadal changes in rainwater alkalinity at a rural Mediterranean site in the Montseny Mountains (NE Spain)

Annual volume-weighted mean (VWM) concentrations in rainwater collected at La Castanya (LC, Montseny Mountains, NE Spain) were analysed from 1983 to 2000 to study the temporal trends in precipitation chemistry, and the causes behind the changes. A significant positive correlation was found between annual rainwater SO₄²⁻ concentrations at LC and Spanish SO₂ emissions (r=0.73, P=0.0008) both decreasing remarkably during this period. Rainwater alkalinity increased during the period, shifting from negative values at the beginning (VWM in the 5 initial years=−2.7 μeq l⁻¹) to alkaline values in recent years (VWM in the 5 final years=18.0 μeq l⁻¹). Stepwise regression analysis indicated that 88% of the variation of alkalinity could be accounted for by the variability of non-marine Ca²⁺ and non-marine SO₄²⁻, with a more prominent dependence on Ca²⁺.Rains of African provenance were highly enriched in alkalinity and Ca²⁺, but no significant increases in their occurrence were found for the study period. Because of the reported higher dust updraft in northern Africa during years of high North Atlantic Oscillation (NAO) index, we also explored the relationship between rainwater variables associated with an African provenance and NAO. Annual precipitation was inversely related to NAO (r=−0.61, P=0.007). The annual wet deposition of African dust-related elements showed no correlation with NAO, probably because wet deposition of these elements depends on two factors (precipitation and dust updraft) which have opposite behaviour with respect to NAO. We hypothesise that dry deposition of African dust during dry spells (not sampled in this study) might be higher during high NAO-index years.     

Quantifying the sources of hazardous elements of suspended particulate matter aerosol collected in Yokohama,Japan

We analyzed metals (Mg, Al, Ca, V, Cr, Mn, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb and Bi), water-soluble ions (Na⁺, NH₄⁺, K⁺, Ca²⁺, Cl^?, NO₃^? and SO₄^2?) and carbonaceous mass (EC and OC) in SPM aerosol samples using an ICP-MS, ion chromatograph and CHN corder, respectively. The SPM samples were collected from 1999 to 2005 at two locations (urban site A and industrial site B) of Yokohama, Japan with concentrations in mean and ranges of 34.2 and 19.7–50.3 μg m^?3 and 22.9 and 12.7–35.1 μg m^?3 for the respective location. Source apportionment of SPM aerosol was conducted appropriately for the first time to these locations employing PCA-APCS technique. Major sources of SPM at site A were a) crustal source, b) urban origin, c) undefined, and d) mineral rock. At site B, the sources were predicted as a) urban origin, b) undefined, c) crustal source, and d) secondarily formed aerosol. The tracers and nature of the source related to urban origin at both sites were similar but retaining different source strength. Secondarily formed aerosol was quite unique at site B. However, mineral rock was remarkable at site A.     

Chemical composition of rainwater in the northeastern Romania, Iasi region (2003–2006)

Chemical composition of rainwater was studied in the northeastern Romania, Iasi region, and the concentrations of major inorganic and organic ions were measured in samples collected between April 2003 and December 2006. The pH of the rainwater is 5.92 (volume weighted mean average, VWM) suggesting a sufficient load of alkaline components neutralizing its acidity. On average, 97% of the acidity in the collected samples is neutralized by CaCO₃ and NH₃. Clear seasonal variations were observed for some of the identified ions (e.g., SO₄²⁻, NO₃⁻, Ca²⁺, NH₄⁺). The data obtained during this work revealed that both concentrations and fluxes of anthropogenic source-related ions (e.g., SO₄²⁻, NO₃⁻ and NH₄⁺) are among the highest reported for European sites. It is shown that meteorology and long-range transport processes may concur to their high levels.     

Tissue S/N ratios and stable isotopes (δS and δN) of epilithic mosses (Haplocladium microphyllum) for showing air pollution in urban cities in Southern China

In urban cities in Southern China, the tissue S/N ratios of epilithic mosses (Haplocladium microphyllum), varied widely from 0.11 to 0.19, are strongly related to some atmospheric chemical parameters (e.g. rainwater SO₄²⁻/NH₄⁺ ratios, each people SO₂ emission). If tissue S/N ratios in the healthy moss species tend to maintain a constant ratio of 0.15 in unpolluted area, our study cities can be divided into two classes: class I (S/N > 0.15, S excess) and class II (S/N < 0.15, N excess), possibly indicative of stronger industrial activity and higher density of population, respectively. Mosses in all these cities obtained S and N from rainwater at a similar ratio. Sulphur and N isotope ratios in mosses are found significantly linearly correlated with local coal δ³⁴S and NH₄⁺-N wet deposition, respectively, indicating that local coal and animal NH₃ are the major atmospheric S and N sources.     

Organic carbon,total nitrogen,and water-soluble ions in clouds from a tropical montane cloud forest in Puerto Rico

Chemical characterization to determine the organic and nitrogen fractions was performed on cloud water samples collected in a mountaintop site in Puerto Rico. Cloud water samples showed average concentrations of 1.09 mg L^?1 of total organic carbon (TOC), of 0.85 mg L^?1 for dissolved organic carbon (DOC) and of and 1.25 mg L^?1 for total nitrogen (TN). Concentrations of organic nitrogen (ON) changed with the origin of the air mass. Changes in their concentrations were observed during periods under the influence of African dust (AD). The ON/TN ratios were 0.26 for the clean and 0.35 for the AD periods. Average concentrations of all these species were similar to those found in remote environments with no anthropogenic contribution. In the AD period, for cloud water the concentrations of TOC were 4 times higher and TN were 3 times higher than during periods of clean air masses associated with the trade winds. These results suggest that a significant fraction of TOC and TN in cloud and rainwater is associated to airborne particulate matter present in dust. Functional groups were identified using proton nuclear magnetic resonance (¹H NMR) spectroscopy. This characterization led to the conclusion that water-soluble organic compounds in these samples are mainly aliphatic oxygenated compounds, with a small amount of aromatics. The ion chromatography results showed that the ionic species were predominantly of marine origin, for air masses with and without African dust influence, with cloud water concentrations of NO₃^? and NH₄⁺ much lower than from polluted areas in the US. An increase of such species as SO₄^2?, Cl^?, Mg²⁺, K⁺ and Ca²⁺ was seen when air masses originated from northwest Africa. The changes in the chemical composition and physical properties of clouds associated with these different types of aerosol particles could affect on cloud formation and processes.     

Isotopes as tracers of sources of lead and strontium in aerosols (TSP & PM2.5) in Beijing

Even after its being phased out in gasoline in the late 90s, lead (Pb) is still present at relatively high levels in the atmosphere of Beijing, China (0.10–0.18 μg m^?3). Its origin is subject to debate as several distinct sources may contribute to the observed pollution levels. This study proposes to constrain the origin(s) of Pb and strontium (Sr) in aerosols, by coupling both Pb and Sr isotope systematics. The characterisation of the main pollution sources (road traffic, smelters, metal refining plants, coal combustion, cement factories, and soil erosion) shows that they can unambiguously be discriminated by the multi-isotope approach (²⁰⁶Pb/²⁰⁴Pb and ⁸⁷Sr/⁸⁶Sr). The study of total suspended particulates (TSP) and fine particles (PM_2.5) from Beijing and its vicinity indicates that both size fractions are controlled by the same sources. Lead isotopes indicate that metal refining plants are the major source of atmospheric lead, followed by thermal power stations and other coal combustion processes. The role of this latter source is confirmed by the study of strontium isotopes. Occasionally, emissions from cement plants and/or input from soil alteration are isotopically detectable.     

Analysis of Hong Kong daily bulk and wet deposition data from 1994 to 1995

Results from a 1-year daily rainwater sampling program, employing both wet and bulk deposition samplers with replicate samples, from 1994 to 1995 in Hong Kong are presented and analysed. Analyte concentrations were found to vary over a wide range of several orders of magnitude, with [H⁺] for example, from 0.16 to 208.9 μeq dm^-3. Diurnal pH values less than 3.83 were measured on five occasions. A significant correlation between pH and lognormal windspeed has been found. This is taken to indicate the minor importance of long-range transport in determining rainwater acidity, since local pollutant emissions accumulate and react under conditions of atmospheric stability in the sub-tropical climate. The H⁺ wet deposition flux onto a polythene surface was 90 meq m^-2 yr^-1 during 1994–1995 at City University. Dry deposition exerts a neutralizing influence upon the acidity from this wet deposition. Although paired t-tests indicated significant differences between the bulk versus wet deposition datasets for cations, but not anions, the dataset means consequently showed such large standard deviations that t-tests indicated no significant differences. In rainwater, the charges from SO^2-₄ and NO^-₃ anions seldom balance the proton charges, implying that they are also derived from solubilization of primary and secondary airborne Ca²⁺, Mg²⁺ and NH⁺₄ particulate matter in rainwater. Use of the [SO^2-₄]/[NO^-₃] ratios in rainwater in fingerprinting pollutant origins has drawbacks, but is generally indicative of a predominantly regional contribution of these secondary pollutants to rainwater. Bulk deposition pH in Hong Kong would be in the region of 4.1 if basic Ca²⁺ compounds alone did not neutralize acidity. The regional rainout pH, inferred after exhaustive below-cloud scavenging, is about 5. The temporal trends in Hong Kong rainwater acidity are blurred.     

Measurements of primary trace gases and NOY composition in Houston,Texas

Concentrations of CO, SO₂, NO, NO₂, and NO_Y were measured atop the University of Houston's Moody Tower supersite during the 2006 TexAQS-II Radical and Aerosol Measurement Project (TRAMP). The lowest concentrations of all primary and secondary species were observed in clean marine air in southerly flow. SO₂ concentrations were usually low, but increased dramatically in sporadic midday plumes advected from sources in the Houston Ship Channel (HSC), located NE of the site. Concentrations of CO and NO_x displayed large diurnal variations in keeping with their co-emission by mobile sources in the Houston Metropolitan Area (HMA). CO/NO_x emission ratios of 5.81 ± 0.94 were observed in the morning rush hour. Nighttime concentrations of NO_x (NO_x = NO + NO₂) and NO_Y (NO_Y = NO + NO₂ + NO₃ + HNO₃ + HONO + 21N₂O₅ + HO₂NO₂ + PANs + RONO₂ + p-NO₃^? + …) were highest in winds from the NNW-NE due to emission from mobile sources. Median ratios of NO_x/NO_Y were approximately 0.9 overnight, reflecting the persistence and/or generation of NO_Z (NO_Z = NO_Y ? NO_x) species in the nighttime Houston boundary layer, and approached unity in the morning rush hour. Daytime concentrations of NO_x and NO_Y were highest in winds from the HSC. NO_x/NO_Y ratios reached their minimum values (median ca 0.63) from 1300 to 1500 CST, near local solar noon, and air masses often retained enough NO_x to sustain additional O₃ formation farther downwind. HNO₃ and PANs comprised the dominant NO_Z species in the HMA, and on a median basis represented 17–20% and 12–15% of NO_Y, respectively, at midday. Concentrations of HNO₃, PANs, and NO_Z, and fractional contributions of these species to NO_Y, were at a maximum in NE flow, reflecting the source strength and reactivity of precursor emissions in the HSC. As a result, daytime O₃ concentrations were highest in air masses with HSC influence. Overall, our findings confirm the impact of the HSC as a dominant source region within the HMA. A comparison of total NO_Y measurements with the sum of measured NO_Y species (NO_Yi = NO_x + HNO₃ + PANs + HONO + p-NO₃^?) yielded excellent overall agreement during both day ([NO_Y](ppb) = ([NO_Yi](ppb)11.03 ± 0.16) ? 0.42; r² = 0.9933) and night ([NO_Y](ppb) = ([NO_Yi](ppb)11.01 ± 0.16) + 0.18; r² = 0.9975). A similar comparison between NO_Y–NO_x concentrations and the sum of NO_Zi (NO_Zi = HNO₃ + PANs + HONO + p-NO₃^?) yielded good overall agreement during the day ([NO_Z](ppb) = ([NO_Zi](ppb)11.01 ± 0.30) + 0.044 ppb; r² = 0.8527) and at night ([NO_Z](ppb) = ([NO_Zi](ppb)11.12 ± 0.69) + 0.16 ppb; r² = 0.6899). Median ratios of NO_Z/NO_Zi were near unity during daylight hours but increased to approximately 1.2 overnight, a difference of 0.15–0.50 ppb. Differences between NO_Z and NO_Zi rarely exceeded combined measurement uncertainties, and variations in NO_Z/NO_Zi ratios may have resulted solely from errors in conversion efficiencies of NO_Y species and changes in NO_Y composition. However, nighttime NO_Z/NO_Zi ratios and the magnitude of NO_Z ? NO_Zi differences were generally consistent with recent observations of ClNO₂ in the nocturnal Houston boundary layer.     

Quantitative chemical composition and characteristics of aerosols over western India: One-year record of temporal variability

One-year quantitative chemical data set consisting of water-soluble constituents (NH₄⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^?, NO₃^?, SO₄^2? and HCO₃^?), crustal and trace elements (Al, Fe, Ca, Mg, K, Mn, Zn, Pb) and carbonaceous species (OC, EC) in ambient aerosols, collected over an urban site located in a high-dust semi-arid region of western India, reveals excellent linear relationship (r² = 0.92; slope = 0.96 ± 0.05) between gravimetrically assessed TSP (total suspended particulates) and chemically analyzed aerosol mass. The TSP abundance ranging from 60 to 250 μg m^?3, over a period of 12 months (January–December), is dominated by mineral dust (～70%); whereas contribution from sea-salts, anthropogenic and carbonaceous species exhibits significant temporal variability depending upon the wind regimes. The mineral dust is enriched in Ca, Mg and Fe with respect to upper continental crust (UCC); whereas Zn and Pb exhibit a characteristic anthropogenic source and high enrichment factors. The carbonaceous species show significant seasonality; with dominance of OC (range: 4.6–28 μg m^?3; average: 12.8 μg m^?3; SD: 6.8) and minor contribution from EC (range: 0.3–4.4 μg m^?3; average: 2.4 μg m^?3; SD: 1.4). The observed concentrations are significantly lower than those reported for the metro cities in South Asia but the OC/EC ratios (range: 4.3–35; average: 8.3; SD: 5.7) are significantly higher than the characteristic ratio (～2–4) reported for the urban atmosphere. Such quantitative chemical characterization of aerosols is essential in assessing their role in atmospheric chemistry and climate change. This study could also be useful in understanding the physical and optical aerosol properties documented from the same site and thus, in validating regional climate models.     

Chemical composition of rainwater and anthropogenic influences in the Piracicaba River Basin,Southeast Brazil

The influences of different kinds of anthropogenic activities on rainwater chemistry in a tropical area were studied during one uninterrupted year at Piracicaba River Basin (Southeast Brazil). A total of 272 rainwater samples collected continuously from August 1997 to July 1998 at four different sites were analyzed for F⁻, CH₃COO⁻, HCOO⁻, MSA, Cl⁻, NO₂⁻, Br⁻, NO₃⁻, SO₄²⁻, C₂O₄²⁻, PO₄³⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, DOC (dissolved organic carbon), DIC (dissolved inorganic carbon), pH and conductivity. The most abundant ion was H⁺ and rain acidity was significant at all sampling sites (average pH of 4.4–4.5). The sources of this free acidity differ among sites and appear to be correlated to the different land-uses. The composition of rainwater appeared to be controlled mostly by three sources: soil dust, sugar cane burning and industrial emissions.     

NH4+, NO3−, and SO42− in roadside and rural size-resolved particles and transformation of NO2/SO2 to nanoparticle-bound NO3−/SO42−

This study investigates ammonium, nitrate, and sulfate (NH₄⁺, NO₃^?, and SO₄^2?) in size-resolved particles (particularly nano (PM_0.01–0.056)/ultrafine (PM_0.01–0.1)) and NO_x/SO₂ collected near a busy road and at a rural site. The average (mass) cumulative fraction of secondary inorganic aerosols (SO₄^2?+NO₃^?+NH₄⁺) in nano or ultrafine particles at the roadside was found to be three to four times that at the rural site. The above three secondary inorganic aerosol species were present in similar cumulative fractions in particles of size 1–18 μm at both sites; however, dissimilar fractions were observed for Cl^?, Na⁺, and K⁺. The nitrogen ratios (NRs: NR = NO₃^??N/(NO₃^??N + NO₂–N)), sulfur ratios (SRs: SR = SO₄^2??S/(SO₄^2??S + SO₂–S)), dNR/D_P (derivative of NR with respect to D_P (particle diameter)), and dSR/D_P (derivative of SR with respect to D_P) at the roadside were higher than those at the rural site for nano/ultrafine particles. At both sites (particularly the roadside), the nanoparticles had significantly higher dNR/D_P and dSR/D_P values than differently sized particles, implying that NO₃^?/SO₄^2? (from NO₂/SO₂ transformation or NO₃^?/SO₄^2? deposition) were present on these particles.     

Deposition processes of ionic constituents to snow cover

Atmospheric deposition is an important removal process of aerosol particles and gases from the atmosphere. To elucidate the relative contributions of wet and dry processes and in-cloud and below-cloud scavenging based on deposition amounts in winter at Mt. Tateyama, central Japan, we obtained daily samples (December, 2006–March, 2007) of size-segregated aerosol particles and precipitation at Senjyugahara (SJ; 475 m a.s.l.) and vertical samples of spring snow cover at Murododaira (MR, 2450 m a.s.l., 13 km distance from SJ) on the western flank of Mt. Tateyama. The NH₄⁺ and nssSO₄^2? in aerosols were mostly found in the fine fraction (<2 μm), although Na⁺, NO₃^?, and nssCa²⁺ were mainly detected in the coarse fraction (>2 μm). Average ionic concentrations (μg g^?1) in precipitation at SJ were higher about 3.8 for Na⁺ and nssCa²⁺, 3.4 for NO₃^?, 3.7 for NH₄⁺, 2.5 for nssSO₄^2? than those at MR, whereas cumulative precipitation amounts at SJ and MR were, respectively, 84 and 175 cm of water equivalent. Wet and dry deposition amounts during the study period were estimated for sites using size-segregated aerosol data, winter averages of HNO₃, NH₃, and SO₂ concentrations, and dry deposition velocities. Particle-dry deposition comprised about 3% (Na⁺) to 11% (NH₄⁺) of the total deposition at MR. The maximum amounts of gas dry deposition were estimated, respectively, as 4, 13, and 3% of the total deposition at MR for NH₄⁺, NO₃^?, and nssSO₄^2?. The relative contributions of below-cloud scavenging (BCS) between MR and SJ were estimated as considering the wet only deposition amount at MR. Higher contributions of BCS were obtained for Na⁺ (56%) and nssCa²⁺ (45%), whereas BCSs for NH₄⁺, NO₃^?, and nssSO₄^2? were lower than 28%. Ionic constituents existing predominantly in the coarse fraction showed a large contribution of BCS.     

Canopy leaching of nutrients and metals in a mountain spruce forest

Precipitation and throughfall fluxes of major ions, nutrients (C, N, P), and metals (Al, Fe, Mn), and the chemical composition of litter fall and living plant tissue in Norway spruce stands (the Bohemian Forest; Czech Republic), were used to evaluate how microbial processes and decay of plant tissue in canopies influence canopy leaching (CL) of elements. Proton exchange for Mg²⁺, Ca²⁺, and K⁺ in decaying biomass and co-transport of Ca²⁺ and K⁺ out of plant cells with organic acid anions were the most likely processes contributing to CL of base cations. The CL of total P and N (and also NO₃^?) was minor. Important proportions of the N and P mineral forms were transformed to organic forms by microbial processes (primary and bacterial production), with the respective CL of ?13.9 and 16.4 mmol m^?2 yr^?1 for NH₄⁺ and organic N, and ?0.33 and 0.22 mmol m^?2 yr^?1 for dissolved reactive P (DRP) and organic P. Most of particulate P and N in throughfall (～90%) originated from microbial DRP and NH₄⁺ transformations, but particulate C mostly came from the fragmentation of plant tissue (58%). Among metals, CL was not observed for Al, was small for Fe (0.3 mmol m^?2 yr^?1), and greatest for Mn (0.9 mmol m^?2 yr^?1) due to leaching from decaying tissue by acidic precipitation.     

Strontium isotope constraints on the seasonal variation of the provenance of base cations in rain water at Kawakami, Central Japan

The ⁸⁷Sr/⁸⁶Sr ratios in monthly precipitation in the forested basin at Kawakami, central Japan, varied seasonally from 0.709 to 0.711 in spring to as low as 0.7062 ± 0.0004 in autumn over nine years from 1987 to 1995. The seasonal variation can be explained in terms of the mixing of three sources of Sr: sea salt (⁸⁷Sr/⁸⁶Sr 0.70917), soluble eolian minerals originating from deserts in continental Asia ( 0.711), and biogenic materials growing on soils derived from the volcanic rock substrates in the vicinity ( 0.706). It is estimated that the contribution of sea-salt Sr into the Kawakami rain Sr is relatively constant (10 ± 5%) and that more than half of the Sr is of biogenic origin throughout the year except during spring rains when 50% of the Sr is due to the dissolution of Ca-minerals from Asian dusts. The dominant contribution of eolian components to spring rains is consistent with the high concentration of ³H, which is typical of air masses from Asia.     

An integrated assessment of seawater intrusion in a small tropical island using geophysical,geochemical, and geostatistical techniques

In this study, geophysics, geochemistry, and geostatistical techniques were integrated to assess seawater intrusion in Kapas Island due to its geological complexity and multiple contamination sources. Five resistivity profiles were measured using an electric resistivity technique. The results reveal very low resistivity <1 Ωm, suggesting either marine clay deposit or seawater intrusion or both along the majority of the resistivity images. As a result, geochemistry was further employed to verify the resistivity evidence. The Chadha and Stiff diagrams classify the island groundwater into Ca-HCO₃, Ca-Na-HCO₃, Na-HCO₃, and Na-Cl water types, with Ca-HCO₃ as the dominant. The Mg²⁺/Mg²⁺+Ca²⁺, HCO₃ ^?/anion, Cl^?/HCO₃ ^?, Na⁺/Cl^?, and SO₄ ^2?/Cl^? ratios show that some sampling sites are affected by seawater intrusion; these sampling sites fall within the same areas that show low-resistivity values. The resulting ratios and resistivity values were then used in the geographical information system (GIS) environment to create the geostatistical map of individual indicators. These maps were then overlaid to create the final map showing seawater-affected areas. The final map successfully delineates the area that is actually undergoing seawater intrusion. The proposed technique is not area specific, and hence, it can work in any place with similar completed characteristics or under the influence of multiple contaminants so as to distinguish the area that is truly affected by any targeted pollutants from the rest. This information would provide managers and policy makers with the knowledge of the current situation and will serve as a guide and standard in water research for sustainable management plan.     

Anthropogenic inputs of boron into urban atmosphere: Evidence from boron isotopes of precipitations in Guiyang City,China

Boron (B) concentrations and isotopic compositions were measured in the precipitations of Guiyang, China for one year. Most precipitation samples have boron concentrations of from 2.1 to 4.8 ng ml^?1, and δ¹¹B values of from +2.0‰ to +30.0‰. Boron concentrations and δ¹¹B values of heavy rain samples are generally higher than those of light rain and snow samples. Anthropogenic inputs provided most of the SO₄^2? and NO₃^?, which were predominant ions in the precipitation. The major cation Ca²⁺ in the precipitation was mainly originated from local dust.The total boron in precipitation from Guiyang is explained by the mixing model of three boron sources. Assuming a δ¹¹B value of +45‰ for the seawater component, contributions of marine source, organic matter and biomass combustion, and coal combustion were estimated to be 32%, 49%, and 19%, respectively to the total boron in Guiyang precipitations. The coal combustion and biomass (and/or organic matter) combustion showed different contributions of boron to the rainwaters in different seasons, the former in cold season while the latter in summer season had a more marked influence on the chemical and isotopic composition of the rainwater. The largest contribution of seawater-originated boron was observed for the heavy rain samples, which was up to 68%. This study indicates that the atmospheric environment of Guiyang city was strongly influenced by human activities, and boron isotopic composition is of great sensitivity to anthropogenic sources and can be a powerful technique to trace various sources of atmospheric emissions and even their origins.     

Chemical characteristics of chromophoric dissolved organic matter in rainwater

Proton nuclear magnetic resonance (¹H-NMR), UV absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy were used to define the chemical characteristics of chromophoric dissolved organic matter (CDOM) in whole and C₁₈ extracted rainwater. The average total recovery of fluorescence determined from the sum of extract and filtrate fractions relative to the whole was 86% suggesting that 14% of fluorescent CDOM in rainwater is comprised of very hydrophobic material that cannot be eluted from the column. Half the fluorescence of rainwater was recovered in the filtrate fraction which is important because it suggests that 50% of the chromophoric material present in precipitation is relatively hydrophilic. The average spectral slope coefficient was smaller in extracted samples (16.3 ± 9.0 μm^?1) relative to whole samples (18.9 ± 2.8 μm^?1) suggesting that the extracted material contains larger molecular weight material. Approximately one-third of the total dissolved organic carbon (DOC) in rainwater exists in the extract fraction suggesting that a large percentage of the uncharacterized DOC in rainwater can be accounted for by these hydrophobic macromolecular species. The fluorescence of extracted samples is strongly correlated with total NMR integration and is most sensitive to aromatic protons suggesting that molecules in this region are the most important in controlling the optical properties of rainwater. The lower removal efficiency of CDOM in rainwater relative to surface waters or the water-soluble fraction of aerosols during solid phase extraction (SPE) suggests that rainwater contains significantly more hydrophilic chromophoric compounds which are compositionally different than found in these other aquatic matrices.     

Atmospheric nitrogen fluxes at the Belgian coast: 2004–2006

Daily and seasonal variations in dry and wet atmospheric nitrogen fluxes have been studied during four campaigns between 2004 and 2006 at a coastal site of the Southern North Sea at De Haan (Belgium) located at coordinates of 51.1723° N and 3.0369° E. Concentrations of inorganic N-compounds were determined in the gaseous phase, size-segregated aerosol (coarse, medium, and fine), and rainwater samples. Dissolved organic nitrogen (DON) was quantified in rainwater. The daily variations in N-fluxes of compounds were evaluated with air-mass backward trajectories, classified into the main air-masses arriving at the sampling site (i.e., continental, North Sea, and Atlantic/UK/Channel).The three, non-episodic campaigns showed broadly consistent fluxes, but during the late summer campaign exceptionally high episodic N-deposition was observed. The average dry and wet fluxes for non-episodic campaigns amounted to 2.6 and 4.0 mg N m^?2 d^?1, respectively, whereas during the episodic late summer period these fluxes were as high as 5.2 and 6.2 mg N m^?2 d^?1, respectively.Non-episodic seasons/campaigns experienced average aerosol fluxes of 0.9–1.4 mg N m^?2 d^?1. Generally, the contribution of aerosol NH₄⁺ was more significant in the medium and fine particulate fractions than that of aerosol NO₃^?, whereas the latter contributed more in the coarse fraction, especially in continental air-masses. During the dry mid-summer campaign, the DON contributed considerably (～15%) to the total N-budget.Exceptionally high episodic aerosol-N inputs have been observed for the late summer campaign, with especially high deposition rates of 3.6 and 2.9 mg N m^?2 d^?1 for Atlantic/UK/Channel and North Sea-continental (mixed) air-masses, respectively. During this pollution episode, the flux of NH₄⁺ was dominating in each aerosol fraction/air-mass, except for coarse continental aerosols. High deposition of gaseous-N was also observed in this campaign with an average total N-flux of 2–2.5-times higher than in other campaigns.