Chemical Composition Of Rainwater Research Articles

Alterations of throughfall and stemflow chemistry by vegetation in China: Insights from a machine learning based meta-analysis

In vegetated ecosystems, the chemical composition of rainwater is strongly altered after gross rainfall (GR) partitioning into throughfall (TF) and stemflow (SF) before entering the under-canopy soil. However, quantitative syntheses of the chemical alteration are lacking, rendering an insufficient comprehension of its overarching patterns and magnitudes. Here, we furnish a comprehensive dataset related to the chemistry of rainfall partitioning by vegetation in China compiled from 131 peer-reviewed papers published between 1988 and 2023. A meta-analysis was conducted to assess the chemical alterations as GR partitions into TF and SF. We discerned a marked acidification effect in SF but not in TF, with the pH being significantly lower in SF than in GR. Additionally, we observed a persistent concentration-based chemical enrichment of total nitrogen (TN) and total phosphorous (TP) as well as 12 commonly reported nutrient-ions (except for Cu2+) in both TF and SF, with SF generally exhibiting a greater degree of chemical enrichment than TF. Using a machine learning method (boosted regression trees), we identified the key drivers from twelve biotic and abiotic predictor variables on the effect sizes of pH, TN, TP, and each nutrient-ion, and further elucidated the prevalent non-linear partial effects of these key drivers on the magnitude of chemical alterations. For instance, three predictor variables were identified as key drivers for the effect sizes of TN for SF, with a descending relative influence of diameter at breast height (56.9 %; positive effect), Human Footprint (16.5 %; positive), and bark texture (14.0 %; stands with mixed bark textures exerting a greater impact). Our study has significant implications for an accurate estimation of nutrient budgets in vegetated ecosystems throughout China, contributes to a deeper understanding of the intricate ways in which biotic and abiotic predictors influence chemical alterations in rainfall partitioning, and aids in evaluating forest health and developing sensible forest management strategies.

The Impact of Canopy on Nutrient Fluxes through Rainfall Partitioning in a Mixed Broadleaf and Coniferous Forest

Rainfall constitutes the primary input in the nutrient flux within forest ecosystems. The forest canopy modulates this flux by partitioning rainfall and selectively absorbing or adding nutrients. In mixed forests, variation in tree species composition regulates rainwater chemical composition, potentially leading to spatial heterogeneity in nutrient distribution and influencing nutrient cycling processes. This study examined the partitioning of rainfall into throughfall and stemflow, as well as their associated nutrient concentrations and fluxes, in a mixed broadleaf and coniferous forest on Changbai Mountain in Northeast China. We observed a rising trend in nutrient contents from rainfall to throughfall and then stemflow. The nutrient contents of stemflow varied largely with tree species due to the differences in canopy structure and bark morphological characteristics. The nutrient input contributed by throughfall and stemflow was 92.30 kg ha−1 during the observation period, and most elements underwent passive leaching through washout except for F− and Na+. We note that the nutrient fluxes in stemflow differed among tree species, with Pinus koraiensis (PK) delivering more acid group anions and Quercus mongolica (QM) providing more cations. Our research provides new insights into nutrient cycling within mixed forest canopies, sparking a transformative advancement in forest management and protection strategies through hydrochemistry-driven solutions.

Economic and Industrial Development SignificantlyContribute to Acidity and Ionic Compositions of Rainwaterin China

To achieve a holistic understanding of the intricate interactions among human activities, atmospheric chemistry, and acid rain in China, a rigorous analysis of rainwater chemistry was made using a dataset comprising 2656 data points from 24 sites. The main cation and anion in the chemical composition of precipitation were Ca2+ and SO42− in China, with an average concentration of 169.9 μeq/L and 135.4 μeq/L, respectively. Acid rain generally occurs in southern cities such as Shenzhen, Guangzhou, Zhuhai, Xiamen, and Chongqing. There were evident regional disparities in acidity and ion concentrations in rainwater, with an increase in acidity and a decrease in ion concentrations from north to south across China. Utilizing positive matrix factorization, the study found that NH4+, SO42−, and NO3− mainly originated from anthropogenic sources such as fossil fuel combustion, vehicle exhaust emissions, agricultural fertilization, and industrial emissions (as reflected by F3 and F4). Ca2+ mainly stems from crustal factors, including industrial dust and natural crust (as represented by F1 and F4). Na+ and Cl− were traceable from marine sources (as reflected by F5), while Mg2+ originated from crust origin (as presented by F1). K+ was mainly derived from a mixed source of crust, marine, and biomass burning (as indicated by F2 and F3). The correlation analyses showed that SO42− and NO3− showed significant correlations with GDP and population. F− was associated with wastewater, which may be linked to the production of brick and tiles from clay with high fluoride contents. The pH was negatively related to industrial wastewater. Long-term analysis of precipitation chemistry in four cities suggested a clear decrease in the proportion of SO42− but a considerable increase in the proportion of NO3− in anions in metropolitans of Shanghai and Chongqing due to the environmental measures that targeted reducing sulfur dioxide (SO2) emissions and increase of vehicles. This showed that pollution control strategies had an impact on precipitation ion concentrations. These results can conclude that economic and industrial growth, which will increase energy consumption, utilization of coal combustion, and a subsequent rise in pollutant emissions, can contribute to the change in the chemical compositions of rainwater and the exacerbation of acid rain.

Chemical composition of rainwater at three sites in Kandy/Peradeniya, Sri Lanka, and its effect on air pollution

The composition of atmospheric precipitation, an important criterion considered to account for air pollution, is usually determined with respect to wet precipitation and dry precipitation, or as bulk deposition in combined form. Although rainwater quality should be continuously monitored in order to understand the extent of air pollution, such investigation lacks attention in Sri Lanka. This study was thus aimed to determine the composition of bulk deposition collected weekly for a period of eleven months from February to December 2019, in three sampling locations; namely the University of Peradeniya (UOP), Kandy City Central (KCC) and Polgolla. Parameters quantitatively determined, rainfall, pH, conductivity, salinity, total dissolved solids (TDS), hardness, anions: Cl−, NO3−, SO42−, F−, PO43− and trace metals: Zn, Fe, Al, Mn, Cu, Pb, Cr, using standard analytical methods indicated that the KCC site showed the overall highest degree of air pollution followed by UOP and Polgolla sites. Nevertheless, no acid rain occurrences were observed during the sampling period in any of the three sites according to pH measurements. Anions of bulk deposition showed the sequence Cl−> SO42− > NO3−in all three sites with Cl−and SO42- being dominant anions. Furthermore, trace metals of bulk deposition showed the sequence, Zn > Fe > Al > Mn > Cu > Pb, in all three sites. Bulk precipitation data analyzed using Pearson correlation showed high positive significant correlations between conductivity and salinity, conductivity and TDS, and salinity and TDS, among all water quality parameters. Among trace metals, the highest positive significant correlation was found to be between Fe and Mn at the UOP Site. The highest positive significant correlation was between Al and Zn at the KCC site. No correlation between trace metals was found at the Polgolla Site.

Trace-elements monitoring of single rainwaters for the environmental risks assessment in the “Land of Fires” located between the provinces of Naples and Caserta

Since rainwater chemical composition can provide valuable information on sources of local air pollution in urbanized and industrialized areas, rainwaters have been collected in the southern Plain of the region known as Campania (located between Caserta and Napoli provinces, Southern Italy). This area is characterized by the presence of heavy traffic, industries, high activity of intensive agriculture and recently sadly known as “Land of Fires” due to illegal uncontrolled burnings. Monitoring of major elements and trace elements of each single rainy event was conducted from May 2016 to January 2017 in four sampling sites long the perpendicular to the coastline, taking into account the main direction of local winds, influenced by sea breeze, to study chemical evidences. Samples were divided in the field into two aliquots: one for the analysis of anions (Cl−, NO3− and SO42−) and cations (Na+, K+, Mg2+ and Ca2+) by ion chromatography, and another one filtered and acidified for the analysis of trace elements (B, Al, Si, Mn, Fe, Cu, Zn, Rb, Sr and Ba) by ICP-MS. Moreover, electrical conductivity (EC) and pH were determined just after the rainfall by a portable instrument and total alkalinity (as HCO3−) was determined in the field by titration with 0.01 M HCl and methyl orange as indicator. Results and data processing confirm that the vertical wash-out of the atmospheric layers closest to the soil is the main mineralization process. There is also chemical evidence linked to the hardest environmental risks, probably just to the illegal uncontrolled burnings and to the agriculture activity. In fact, the maximum values of NO3− and of SO42− obtained in this study are, respectively, 51.6 mg/l and 19.5 mg/l. Moreover, sea breeze has a lavage effect, as well as morphology can save the atmospheric composition despite polluting sites closeness. Therefore, this research has tried to find an innovative experimental design in the environmental risks assessment, which may lead to differently unknown results due to the diversity of sources and/or extension and/or morphology of the territories studied. This is due to the simultaneous application of points only recently introduced in other similar studies, which are the monitoring of trace elements, of single rainfall and the study of air dynamics too through water data. This experimental design has proven to be a first step very suitable for locating and detailing the hardest environmental risks despite geographical extension and complexity of the investigated region: all the trace elements have shown high R correlations with both NO3− and SO42− for specific individuated groups of data, as well as due to the specific probable polluting processes above. In the future, there should be a study on trace elements in air to compare with the values obtained in rainwater.

Atmospheric Deposition around the Industrial Areas of Milazzo and Priolo Gargallo (Sicily-Italy)-Part A: Major Ions.

The chemical composition of rainwater was studied in two highly-industrialised areas in Sicily (southern Italy), between June 2018 and July 2019. The study areas were characterised by large oil refining plants and other industrial hubs whose processes contribute to the release of large amounts of gaseous species that can affect the chemical composition of atmospheric deposition As in most of the Mediterranean area, rainwater acidity (ranging in the study area between 3.9 and 8.3) was buffered by the dissolution of abundant geogenic carbonate aerosol. In particular, calcium and magnesium cations showed the highest pH-neutralizing factor, with ~92% of the acidity brought by SO42- and NO3- neutralized by alkaline dust. The lowest pH values were observed in samples collected after abundant rain periods, characterised by a less significant dry deposition of alkaline materials. Electrical Conductivity (ranging between 7 µS cm-1 and 396 µS cm-1) was inversely correlated with the amount of rainfall measured in the two areas. Concentrations of major ionic species followed the sequence Cl- > Na+ > SO42- ≃ HCO3- > ≃ Ca2+ > NO3- > Mg2+ > K+ > F-. High loads of Na+ and Cl- (with a calculated R2 = 0.99) reflected proximity to the sea. Calcium, potassium, and non-sea-salt magnesium had a prevalent crustal origin. Non-sea salt sulphate, nitrate, and fluoride can be attributed mainly to anthropogenic sources. Mt. Etna, during eruptive periods, may be also considered, on a regional scale, a significant source for fluoride, non-sea salt sulphate, and even chloride.

Depth distribution and chemistry of salts as factors controlling tafoni and honeycombs development

Salts play a pivotal role in the processes forming tafoni and honeycombs but only few studies have focused on their areal and depth distribution. An X-ray diffraction, rock leachates chemistry, and evaporation front depth were combined to get a deeper insight into factors controlling salt composition and distribution. Five sites representing various lithological and/or climate conditions were studied. The data show that salt composition is a result of the interaction between chemical compositions of rainwater and lithology. Gypsum was found to be a major salt on all sites with halite dominating in arid sites. On humid sites the high relative air humidity prevents its precipitation. Gypsum and epsomite dominate also on sites where the rock contains a considerable amount of pyrite. Alum-(K) occurs in quartz sandstones when affected by acid rain. Some ions probably occur in residual brines, rather than precipitated salts (CaCl in arid or NaCl in humid sites). On arid sites, the salt content in the tafoni backwalls is 4–20 times higher than in outer walls and rapidly decreases with depth which is consistent with shallow evaporation front in backwalls. The low salt content in the outer walls reflects the dilution effect of surface runoff after rains and the infiltration of water through the outer walls toward depth. In two humid sites, on the contrary, no differences were found between the salt content of the backwalls and the outer walls. At one site the data shows that the whole surface of tafoni serves as the salt precipitation zone and tafoni are thus recently degrading. The honeycomb site differs from all tafoni sites since the honeycombs are mostly protected from rain runoff, which prevents the washing-out of salts even from the outer walls.

Wet season chemical composition of atmospheric wet deposition at Cape Point

The measurement of precipitation chemistry enables the assessment of the temporal and spatial evolution of the chemical composition of the atmosphere associated with atmospheric physical and chemical mechanisms. The aims of this study were to report the chemical composition of rainwater collected at a marine environment, i.e. the Cape Point Global Atmosphere Watch (CPT GAW) station from 2004 to 2012. As expected, the volume weighted mean (VWM) concentrations of Na+ (298.64 μEq.L-1) and Cl- (354.18 μEq.L-1) were significantly higher compared to the VWM concentrations of other ionic species, as well as compared to the VWM concentrations thereof at the sites in the South African interior. The average pH of rainwater was slightly lower than the pH of unpolluted rainwater, mainly due to NO3- associated with the occasional influence of the Cape Town metropole. In contrast to the sites situated in the north-eastern South African interior, where anthropogenic SO42- was the major constituent in rainwater, SO42- at CPT GAW was entirely associated with marine air with no anthropogenic contribution. It was also indicated that 94% of the chemical content at CPT GAW can be attributed to the marine source.

Chemical Characteristics and Trends of Indian Summer Monsoon Rainfall: A Review

The Indian summer monsoon (ISM) regulates the pace of life for billions of people in the Indian subcontinent by driving the agriculture and Gross Domestic Product of the region. The chemical composition of ISM is influenced by pollutant type, meteorology, and topography. As a result, the chemical makeup of rainwater varies greatly across places. The current review article highlights the variations and trends of the principal chemical constituents of rainwater (Na+, K+, Ca2+, Mg2+, NH4+, NO3–, SO42– and Cl–) across six homogeneous Indian monsoon regions: Central Northeast, Hilly, Northwest, Northeast, Peninsular and West Central region. Average rainwater pH ranged from 5.31 to 6.70 in these six regions. The incidence of acidic rain events at three separate locations in the Peninsular region suggests a significant impact of anthropogenic emissions. The chemical composition of rainwater in all these regions varied considerably and seemed to form a regional pattern. The majority of the ions in rainwater were highest in the Northwest while lowest in the Peninsular region. Cl– had a significant correlation with Na+ and NH4+ in the Hilly region, and with Na+ and Mg2+ in the West Central region suggesting it is sourced from both marine and anthropogenic sources. The soil Enrichment Factor relative to Ca2+ demonstrated that soil has a significant effect on rainwater composition. Ca2+ was determined to be the most abundant neutralizing ion in all the regions. Furthermore, the synthesis of rainwater chemistry reveals a strong relationship with dominant interannual climate variability El Niño Southern Oscillation with significantly higher concentrations of Na+, K+, Ca2+, Cl– and SO4– in rainwater during El Niño year compared to La Niña year.

Influence of Typhoons on Chemical Makeup of Rainwater in Zhanjiang, China

Typhoons are extreme weather events with substantial effects on ambient air. However, whether typhoons of different intensities have the same effects on the chemical composition of rainwater is unclear. Therefore, 4 years of rainwater sampling and an analysis of the ionic composition (Cl–, Ca2+, Na+, SO42–, Mg2+, F–, and K+) of rainwater were conducted in Zhanjiang, a city on the southern tip of mainland China. The ionic composition varied seasonally, being high in dry seasons whereas low in wet seasons; ion levels were controlled by rainfall dilution effects rather than by the monsoon transition. Source determination demonstrated that the marine influences in the dry and wet seasons were similar, further indicating the limited impact of the monsoon climate on the ionic species’ seasonal patterns. The heavy rain and strong wind (> 47.4 m s–1) brought by a super typhoon led to an increase in ionic species carried from continental sources into ambient air, and such species were then captured by precipitation. The weak winds (10.71–12.84 m s–1) brought by weak typhoons failed to blow such ions into the air, but rainfall dilution still occurred and was dependent upon rainfall amount. Our results suggest that strong typhoons can increase ion concentrations in rainwater, whereas weak typhoons reduce such concentrations. The results provide new insight into the relationship between air quality and typhoons.

Chemical composition of rainwater at an urban and two rural stations in the west of Iran, Hamedan

Chemical composition of rainwater at an urban and two rural stations in the west of Iran, Hamedan

Study on Acidity and Neutralizing Ability of Ions in the Chemical Composition of Rainwater

The acidity in rainwater is mainly controlled by the presence of H2SO4, HNO3 in combination with the ability to neutralize cations in rainwater. pH is an important value in the evaluation of acidity in rainwater. The research used a series of rainwater quality monitoring data from 2005 to 2018 in Vietnam. The research showed that the average pH distribution at 23 stations ranged from 5.83 ± 0.62. The rains with pH <5.6 appear in all years at the research stations. Considering the ability of acid neutralizing to various ions shows that Ca2+ is the main contributor to acid neutralization processes in rainwater, followed by Mg2 +, NH4+, and K+. While Ca2+ always play the highest acid neutralizing role at all stations; Depending on each station, Mg2+ and NH4+ ions play a role in neutralizing acidity in rainwater. The research also shows a match between the trend of H+ concentration and the tendency of cations to contribute to acid neutralization in rainwater.

Interlinkages Between Total Nitrogen and DOC Levels at an Urban Site of Saharsa District of Bihar (India)

Nitrogen is an element essential for building fundamental blocks of life. When present in excess amount in air, it causes adverse effects for the environment and human health.Different air pollutants when scavenged through rains are deposited on the surface. The chemical composition of rain water is an indicator of the levels of different air pollutants in the region. The present study reports the concentrations of Dissolved Organic Carbon (DOC) and the reactive nitrogen species (NO3- and NH4+) in rain water at an urban site located in the Saharsa district of Bihar. The sampling was carried out during July 2018 to October 2018.Total 18 samples were collected during this period. Results showed that the concentration of NO3- was considerably higher (2.91 mg/L)ranging from 0.26 to 11.84 mg/L than the NH4+(0.84 mg/L) ranging from 0.00 to 3.2 mg/L.The pH value in the samples ranged from 5.50 to 7.68 with a mean value of 6.52.The DOC in rain water has been estimated by using the Shimadzu TOC analyzer. Apart from DOC, total carbon (TC), total nitrogen (TN) & inorganic carbon (IC) have also been also analyzed by Shimadzu TOC analyzer. The results showed that both anthropogenic and natural sources contributed to the dissolved organic carbon (DOC) in rain water. The linkages between the sources and the transformations of gaseous NH3 with DOC have been established considering the fact that most of TN is represented by NH3.Airmass back trajectory analysis showed that the site has trans-boundary source influence from Bay of Bengal and Bangladesh. The study suggests that there is need of continuous monitoring of these parameters in air in order to notice any impact on human health, soil and vegetation.

Baseline for rainwater chemistry and quality as influenced by Nyiragongo volcano permanent plume, East Africa

Single rainwater samples were collected in the city of Goma (~1,1 million inhabitants), eastern Democratic Republic of the Congo, from January to June 2013 to draw a baseline for rainwater chemical composition and quality as influenced by the permanent plume of Nyiragongo volcano. This was a better period for a baseline as the neighboring Nyamulagira volcano, only 15 km apart, had no important degassing from its central crater, and hence the recorded volcanic influence on the rainwater chemistry was solely from Nyiragongo's lava lake which has been active since May 2002. The baseline for the rainwater chemistry and quality is important for this highly populated region where rainwater is the unique potable water source for the inhabitants of many villages surrounding the volcanoes, and for some of the inhabitants of the city of Goma. Our results show that samples collected at the crater rim of Nyiragongo were more acidic with pH ranging from 3.70 to 3.82, while the majority of rainwater samples collected in downtown Goma city and to the northeastern zone of the volcano had pH close to 5.7; which represents the value for rainwater from unpolluted continental areas (Berner and Berner, 2012). However, the pH was as low as 3.93 to the west of Nyiragongo volcano because the volcanic plume is directed westward by the dominant local wind direction. The western part of the city of Goma as well as the small town of Sake and many villages (e.g. Rusayo, Mubambiro, Kingi, …) are located in this zone, and experience endemic fluorosis caused by high fluoride in the available water. The mean F− in this zone was 0.38 mg/L, while the southern and northeastern zones had mean F− concentrations on 0.44 and 0.01 mg/L respectively; even though concentrations higher than the WHO guidelines were found in few samples from the western zone (1.69 mg/L) and from the southern zone (3.44 mg/L). Compared to data from Cuoco et al. (2012) obtained during the Nyamulagira 2010 eruption, and from Balagizi et al.2017 and Liotta et al., 2017 obtained during the intense degassing of both Nyiragongo and Nyamulagira lava lakes; we have noted similarity in the spatial variation of the pH, but samples from the present study showed notable lower concentrations of major elements. This is the case for fluoride which is strictly of volcanic origin. For the other major elements, anthropogenic sources, mainly the traffic and wind-blown dust; or other non-volcanic natural sources influenced their concentrations. Thus, the anions (Cl− and SO42−) and cations (Na+, K+, Mg2+, and Ca2+) from the present study are either lower compared to that previously reported in the literature for the Virunga, or are both comparable for the zones impacted by anthropogenic activities.

Chemical Composition of Rainwater at Selected Sites on Upolu Island, Samoa

The study involved analysis of rainwater samples at four sites on Upolu Island, Samoa from November 2019 to April 2020. A total of 48 rainwater samples were analysed in order to determine the major cations (Na+, Mg2+, Ca2+, K+) and anions (Cl-, , ) in wet precipitation from the four sites. The average pH of the rainwater was 6.89, perhaps due to neutralization. Only 50% of the rain samples had a pH above 5.6. This shows strong inputs of alkaline species to rainwater samples in some sites. The average pH of samples higher than 5.6 is due to high loadings of sodium ions. The rainwater samples are dominated by Na+, Ca2+, Mg2+, Cl- and . The principal cations and anions, in decreasing order, are Na+ > Mg2+ > Ca2+ > K+ and Cl- > > . The correlation study and the comparison of major ion composition with other sites revealed that rainwater ion composition is strongly influenced by marine sources rather than anthropogenic and terrestrial sources.

Design of pH Responsive Textile as a Sensor Material for Acid Rain.

The chemical composition of rainwater can serve as an indicator of the excess of acidifying air pollutants. The pH value of rainwater in the presence of sulphur dioxide and nitrogen oxides, the precursors of acid rain, falls below pH 5.6, which is the limit value for acid rain. In this research, the tailoring of halochromic textile was examined for the design of a functional textile that can serve as a sensor and inform the wearer about the presence of pollutants in the air by means of an immediate colour change. For this purpose, a polyamide 6 fabric was dyed with the pH-sensitive Bromocresol green dye, which causes a colour change below pH 3.6 (yellow) and above pH 5.4 (blue). In addition, the dyed polyamide 6 fabric was treated with a water and oil repellent finish. Colour and colour change before and after immersion of unfinished and finished dyed samples in buffer solutions with different pH values were evaluated spectrophotometrically using the CIELAB colour space. The colour fastness to rubbing, washing, and light, and the water and oil repellency of the dyed fabrics were determined according to valid SIST EN ISO standards. The results showed that the unfinished dyed polyamide 6 fabric undergoes a reversible colour change faster and more clearly than the finished dyed polyamide 6 fabric. The dyed polyamide 6 fabric had good colour fastness to rubbing and domestic and commercial laundering, while the colour fastness to light was poor. In addition, the dyed polyamide 6 fabric was pH-sensitive, despite dye degradation under xenon light, regardless of whether it was finished.

Source apportionment of rainwater chemical composition in wet precipitation at Kelaniya in Sri Lanka

Rainwater quality is of utmost importance as it can be used to predict atmospheric quality which of course governs, to some extent, the health of the ecosystem. In this regard, the research reported here was to study chemical characteristics of precipitation in Kelaniya, Gampaha District, one of the most populated and most urbanized districts in Sri Lanka. This study was conducted during the period from 2012 to 2014, and wet precipitation was analyzed for pH, conductivity, Na+, NH4+, K+, Mg2+, Ca2+, F−, Cl−, NO3−, SO42−, Pb, Cu, Mn, Al, Zn, and Fe for a total of seventy-eight (78) samples. Volume-weighted average concentrations of the major ionic species present in precipitation samples were in the order of Na+ > Ca2+ > Cl− > SO42− > NH4+ > Mg2+ > NO3− > K+ > F−. Neutralization of the acidic species would take place due to the presence of NH4+ and CaCO3. When considering marine contribution, SO42−/Na+, Ca2+/Na+, and Mg2+/Na+ ratios are higher than the reference value suggesting that contribution of sources be possible other than marine. Among metallic constituents, the concentration of Al is the highest while that of Mn is the lowest. Significant correlation is observed among certain ions and elements (Ca2+, SO42−, Mg2+, Al, Cu, Fe, Zn, and H+) which indicates their source of origin and chemical interaction. This study reveals that chemical composition of rain water depends on both anthropogenic activities and natural phenomena.

Risk assessment and source apportionment of wet bulk deposition in three typical sites of Gampaha District, Sri Lanka

Scavenging of pollutants emitted to the atmosphere from natural resources and anthropogenic activities changes the chemical composition of rainwater. However, determination of the extent of atmospheric pollution and identification of pollution sources have not been regularly carried out in Sri Lanka. The objective of this research is therefore to analyze bulk deposition samples collected during a 7-month period from 10 June 2017 to 6 January 2018 in three different locations in Sri Lanka, Katunayake, Gampaha and Lunugama, followed by analysis of rainwater quality parameters including anions and cations using standard methods. These locations differ from each other in geography, industrialization and urbanization. Acid rain was not encountered in any of the three locations during the sampling period according to the pH measurements. The volume-weighted mean ion concentration in the three locations determined by ion chromatography varied as K+ < NH4+ < Mg2+ < Ca2+ < Na+. The dominant cations were Ca2+ and Na+, while Cl− and SO42− were identified as the dominant anions in all locations. The ratios between Na+ and the ions Cl−, SO42−, Ca2+, K+ and Mg2+, calculated using the enrichment factor, indicate that some ions from marine and anthropogenic activities contribute to the rainwater. The Katunayake sampling location showed the highest Pearson correlation between Na+ and Cl− because of the sea breeze, while Ca2+ and Mg2+ showed the highest Pearson correlation in the Gampaha and Lunugama locations because of soil dust. Although rainwater is not acidic according to pH measurements, it can be neutralized by calcium salts. This masking effect should thus be considered in risk assessment strategies. Continuous monitoring of rainwater quality is necessary to reach sound conclusions and make predictions about atmospheric quality.

Determining rainwater chemistry to reveal alkaline rain trend in Southwest China: Evidence from a frequent-rainy karst area with extensive agricultural production

Rainwater chemistry plays an important role in the earth-surficial ecosystem, but studies on rainwater chemical composition of karst agro-ecosystem are rare. To explore the rainwater alkalization and the provenance of components responsible for neutralization, two-years chemical monitoring of rainwater was carried out in a karst agricultural catchment in Southwest China. The main findings suggest that SO42−, NO3−, Ca2+, and NH4+ are the principal ions. All the ionic contents show distinctly seasonal variation (highest in winter) in response to variations in seasonal precipitation because the rain-scour process can efficiently remove atmospheric materials. Source identification indicates that Cl− and Na+ are mainly derived from marine input whereas SO42− and NO3− are controlled by anthropogenic emission, in particular, fixed emission sources. The source of NH4+ is attributed to intense agricultural production, while Ca2+ and Mg2+ are mainly derived from calcite dissolution. The rainwater alkalization caused by the seasonal acid neutralization (via basic components, Ca2+ and NH4+) is beneficial to crop growth but also reflect agricultural overfertilization. Sulfur controlled the total wet acid deposition (68%–94%) and could be a potential agent of weathering.

Atmospheric chemical composition of bulk deposition at two geographically distinct locations in Sri Lanka.

This study presented the research work carried out for the investigation of chemical composition of bulk precipitation in two geographically and economically distinct areas, namely Gampaha and Kandy Districts. This study was conducted from 2013 to 2014 at three sampling stations in each District. The bulk precipitation was analyzed for pH, conductivity, Na+, NH4+, K+, Mg2+, Ca2+, F-, Cl-, NO3-, SO42-, Pb, Cu, Mn, Al, Zn and Fe for a total of 375 samples. Only 8% events of acidic precipitation were recorded in Gampaha District when compared with 3% in Kandy District. The volume weighted average concentrations of the major ionic species present in precipitation samples were in the order of Na+ > Ca2+ > Cl- > NH4+ > SO42- > Mg2+ > NO3- > K+ > F- in the Gampaha stations, while the order was NH4+ > Ca2+ > Na+ > Cl- > SO42- > Mg2+ > NO3- > K+ > F- in Kandy District. Neutralization of acidity of precipitation is much more related to CaCO3 than NH3, and high content of Ca2+ ions present in both Districts strongly supports this fact. When considering marine contribution, SO42-/Na+, Ca2+/Na+ and Mg2+/Na+ ratios are higher than the reference value suggesting contribution of sources other than marine. Depositions of both Districts show that the concentration of Al is the highest while that of Mn is the lowest. Principal component analysis suggests that influencing human activities on chemical composition of rain water depends on thermal power plant, oil refinery, heavy traffic and waste incineration in the study area.