Summer rain events in south-east Asia: Spatial and temporal variations

During the summer monsoon period in south-east Asia marine airstreams normally prevail at the south China coast. However, when tropical cyclones approach then polluted airmasses from south-eastern China can impart high ionic concentrations and high acidity to rainwater. This is illustrated by two examples and the small-scale horizontal variations in rainwater composition are minor during these episodes. Since long-term quality-assured studies of the composition of rainwater in south-east Asia are scarce, the results at three sampling sites in Hong Kong during summer monsoon periods are compared with previous data from the same season. The results for the mid- to end-1990's show a similar trend to those for the ambient concentrations of sulphate and nitrate in aerosol in Hong Kong, which show flattened trends from 1995 to 1999. A marked increase in acidity is found in the summer monsoon period of 2004 which is attributed to the greater proportion of approaching cyclone weather systems in the dataset, reflecting both the increased local emission sources and the burgeoning economic growth of the Pearl River Delta Region. Comparison of the rainwater composition with that at other south-east Asian cities during the summer monsoon period shows that it is most acidic in Hong Kong.     

Influence of Changes in the Prevailing Synoptic Conditions on the Response of Aerosol Characteristics to Land- and Sea-Breeze Circulations at a Coastal Station

The changes in the response of near surfaceaerosol properties to land- and sea-breezecirculations, associated with the changes in the prevailing synoptic meteorological conditions, are examined for a tropical coastal station. Aerosol properties are nearly similar in both the breeze regimes (land and sea) during seasons of marine airmass while they are distinct during seasons of continental airmass. As the prevailing winds shift from continental to marine and the ambient weather changes from winter conditions to the humid monsoon season, the submicron mode, which dominated the aerosol mass-size distribution, is largely suppressed and the dominance of the super micron mode increases. During periods of continental air mass (winter), the aerosol loading is significantly higher in the land-breeze regime, (particularly in the submicron range) but as the winds shift to marine, the loading initially becomes insensitive to the breeze regimes and later becomes higher in the sea-breeze regime, particularly in the super micron range.     

Rainwater chemistry and bulk atmospheric deposition in a tropical semiarid ecosystem: the Brazilian Caatinga

We assessed the rainwater chemistry, the potential sources of its main inorganic components and bulk atmospheric deposition in a rural tropical semiarid region in the Brazilian Caatinga. Rainfall samples were collected during two wet seasons, one during an extremely dry year (2012) and one during a year with normal rainfall (2013). According to measurements of the main inorganic ions in the rainwater (H⁺, Na⁺, NH₄ ⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?, NO₃ ^?, and SO₄ ^2?), no differences were observed in the total ionic charge between the two investigated wet seasons. However, Ca²⁺, K⁺, NH₄ ⁺ and NO₃ ^? were significant higher in the wetter year (p < 0.05) which was attributed to anthropogenic activities, such as organic fertilizer applications. The total ionic contents of the rainwater suggested a dominant marine contribution, accounting for 76 % and 58 % of the rainwater in 2012 and 2013, respectively. The sum of the non-sea-salt fractions of Cl^?, SO₄ ^2?, Mg²⁺, Ca²⁺ and K⁺ were 19 % and 33 % in 2012 and 2013, and the nitrogenous compounds accounted for 2.8 % and 6.0 % of the total ionic contents in 2012 and 2013, respectively. The ionic ratios suggested that Mg²⁺ was probably the main neutralizing constituent of rainwater acidity, followed by Ca²⁺. We observed a low bulk atmospheric deposition of all major rainwater ions during both wet seasons. Regarding nitrogen deposition, we estimated slightly lower annual inputs than previous global estimates. Our findings contribute to the understanding of rainfall chemistry in northeastern Brazil by providing baseline information for a previously unstudied tropical semiarid ecosystem.     

Summer monsoon indices on June rainfall in Hong Kong and its vicinity

Climatologically, June is usually the wettest month in Hong Kong. With significant interannual variation of the summer monsoon, the rainfall variability in June is also large. As Hong Kong is in close proximity to the peripheries of different monsoon regions, the variability of June rainfall largely depends on the relative strength of various monsoon systems. In the present study, a new index comparing the relative condition of the western North Pacific summer monsoon and the South China Sea summer monsoon is developed based on the difference between the respective monsoon indices WNPMI (western North Pacific summer monsoon index) and UMI (unified monsoon index). It is shown that June rainfall in Hong Kong and its vicinity is better correlated with this new index than either WNPMI or UMI alone. Based on the signs of the new index in conjunction with those of WNPMI and UMI, a framework to stratify the monsoon conditions into different configurations together with a simple scheme to summarize the associated rainfall responses is formulated. This study highlights how the rainfall variability on a local or regional scale can be quantified by the broad-scale conditions of different monsoon systems.     

TYPICAL WEATHER CHARACTERISTICS ASSOCIATED WITH AIR POLLUTION IN HONG KONG AREA

With the hourly data of Air Pollution Index (API) by Hong Kong Environmental Protection Department (HKEPD) during the 6 years of 2000 - 2005 and NCEP / NCAR reanalysis data of 2.5° × 2.5° wind and pressure fields, the characteristics of API in Hong Kong area and the impacts of typical weather characteristics on the air pollution in Hong Kong have been studied. The results are shown as follows. (1) The API exhibits obvious seasonal variability as the number of air pollution days increases by the year. For most of the local monitoring stations, it is the most from January to March, a little less from July to September and the least from April to June. (2) There are four typical types of weather situations that are responsible for the air pollution in Hong Kong: tropical cyclones, continental cold highs, transformed highs that have moved out to sea and low pressure troughs.     

Indirect radiative forcing and climatic effect of the anthropogenic nitrate aerosol on regional climate of China

The regional climate model (RegCM3) and a tropospheric atmosphere chemistry model (TACM) were coupled, thus a regional climate chemistry modeling system (RegCCMS) was constructed, which was applied to investigate the spatial distribution of anthropogenic nitrate aerosols, indirect radiative forcing, as well as its climatic effect over China. TACM includes the thermodynamic equilibrium model ISORROPIA and a condensed gas-phase chemistry model. Investigations show that the concentration of nitrate aerosols is relatively high over North and East China with a maximum of 29 μg m^-3 in January and 8 μg m^-3 in July. Due to the influence of air temperature on thermodynamic equilibrium, wet scavenging of precipitation and the monsoon climate, there are obvious seasonal differences in nitrate concentrations. The average indirect radiative forcing at the tropopause due to nitrate aerosols is -1.63 W m^-2 in January and -2.65 W m^-2 in July, respectively. In some areas, indirect radiative forcing reaches $-$10 W m^-2. Sensitivity tests show that nitrate aerosols make the surface air temperature drop and the precipitation reduce on the national level. The mean changes in surface air temperature and precipitation are -0.13 K and -0.01 mm d^-1 in January and -0.09 K and -0.11 mm d^-1 in July, respectively, showing significant differences in different regions.     

Rainwater Chemistry at Mt. Etna (Italy): Natural and Anthropogenic Sources of Major Ions

Major ion content of 37 wet-only rainwater samples collected on the southern flank of Mount Etna volcano was investigated. Measured pH values range from 3.80 to 7.22 and display a positive correlation with Ca²⁺ and an inverse correlation with NO₃ ^–, suggesting that anthropogenic NO_x are the most effective acidifying agents while Ca, likely as solid CaCO₃, is the prevailing proton acceptor. Na/Cl ratios indicate a dominant marine origin for both species, while K, mg and Ca contents point to additional sources (soil dust, fertilisers etc.). Nitrate and sulphate concentrations display a nearly constant ratio indicating a common anthropogenic origin, and only a few samples are characterised by sulphate excess. The analysis of time series reveals a good correlation between the excess sulphate in rainwater and SO₂ fluxes from the summit craters plume. Non sea salt chloride contents show also a significant correlation with volcanic activity indicating a magmatic sulphur and chloride contribution to rainwater. Meteoric flux estimations point to a prevailing magmatic origin for sulphur in the collected rainwaters while sea spray is the main source of chlorine.     

North-East monsoon rainfall extremes over the southern peninsular India and their association with El Niño

The present study investigates the relationship between extreme north-east (NE) monsoon rainfall (NEMR) over the Indian peninsula region and El Niño forcing. This turns out to be a critical science issue especially after the 2015 Chennai flood. The puzzle being while most El Niños favour good NE monsoon, some don’t. In fact some El Niño years witnessed deficit NE monsoon. Therefore two different cases (or classes) of El Niños are considered for analysis based on standardized NEMR index and Niño 3.4 index with case-1 being both Niño-3.4 and NEMR indices greater than +1 and case-2 being Niño-3.4 index greater than +1 and NEMR index less than −1. Composite analysis suggests that SST anomalies in the central and eastern Pacific are strong in both cases but large differences are noted in the spatial distribution of SST over the Indo-western Pacific region. This questions our understanding of NEMR as mirror image of El Niño conditions in the Pacific. It is noted that the favourable excess NEMR in case-1 is due to anomalous moisture transport from Bay of Bengal and equatorial Indian Ocean to southern peninsular India. Strong SST gradient between warm western Indian Ocean (and Bay of Bengal) and cool western Pacific induced strong easterly wind anomalies during NE monsoon season favour moisture transport towards the core NE monsoon region. Further anomalous moisture convergence and convection over the core NE monsoon region supported positive rainfall anomalies in case-1. While in case-2, weak SST gradients over the Indo-western Pacific and absence of local low level convergence over NE monsoon region are mainly responsible for deficit rainfall. The ocean dynamics in the Indian Ocean displayed large differences during case-1 and case-2, suggesting the key role of Rossby wave dynamics in the Indian Ocean on NE monsoon extremes. Apart from the large scale circulation differences the number of cyclonic systems land fall for case-1 and case-2 have also contributed for variations in NE monsoon rainfall extremes during El Niño years. This study indicates that despite having strong warming in the central and eastern Pacific, NE monsoon rainfall variations over the southern peninsular India is mostly determined by SST gradient over the Indo-western Pacific region and number of systems formation in the Bay of Bengal and their land fall. The paper concludes that though the favourable large scale circulation induced by Pacific is important in modulating the NE monsoon rainfall the local air sea interaction plays a key role in modulating or driving rainfall extremes associated with El Niño.     

Influence of Tropical Cyclones on Hong Kong Air Quality

Tropical cyclones(TCs) constitute one of the major atmospheric activities affecting the air quality of the Pearl River Delta region. In this study, the impact of TCs on air quality in Hong Kong during the TC active season(July–October) from 2000 to 2015 is investigated. It is found that 57.5% of days with concentration of particulate matter with an aerodynamic diameter 10 μm(PM_(10)) above the 90th percentile are related to TC activity. TCs in three regions, located to the east, southeast, and southwest of Hong Kong, have obvious impacts on pollutant concentration. When TCs are located east of Hong Kong near Taiwan, 65.5%/38.7% of the days have high or extremely high PM_(10)/ozone(O_3) levels, which are associated with northerly wind, sinking motion, and relatively low precipitation. When TCs are located southeast of Hong Kong, 48.1%/58.2% of the days have high pollution levels, associated mainly with continental air mass transport. When TCs are south or west of Hong Kong, only 20.8%/16.9% of the days have high PM_(10)/O_3 levels, and the air quality in Hong Kong is generally good or normal due to TC-associated precipitation, oceanic air mass transport, and an enhanced rising motion. The higher chance of high O_3 days when TCs are present between Hong Kong and Taiwan, possibly due to lower-than-normal precipitation along the east coast of China under TC circulation. The results in this study highlight the important influence of TC position and associated atmospheric circulations on the air quality in Hong Kong.     

Long-Term Trends in Pre-Summer Daytime and Nocturnal Extreme Hourly Rainfall in a Coastal City of South China

The long-term trends in the occurrence frequency of pre-summer daytime and nocturnal extreme hourly rainfall(EXHR) during 1988-2018 in Hong Kong and their spatial distributions are examined and analyzed. Despite a significant increasing trend observed in the occurrence frequency of pre-summer EXHRs during the investigated period,the increase in daytime and nocturnal EXHRs show distinct spatial patterns. Nocturnal EXHRs show uniform increasing trends over the entire Hong Kong. However, the increa...     

Chemical composition of rain water and influence of airmass trajectories at a rural site in an ecological sensitive area of Western Ghats (India)

Samples of rain water were collected during monsoon season (June to September) of 2006 and 2007 at Hudegadde, a rural site located in an ecological sensitive area of Western Ghats. The collected samples were analyzed for pH, conductivity and major ions. At this site, rainwater pH varied from 4.20 to 7.39 with 5.65 as volume weighed mean. The observed mean was slightly lower than the average pH reported at most of the Indian continental sites. Monthly variation showed that average pH of rain water was the lowest during September (end of monsoon) and the highest during July (peak of monsoon). Overall, marine sources had dominating influence at this site. However, significant influence of anthropogenic and crustal sources from local as well as inter-continental regions was also noticed. As compared to NO₃⁻, higher concentration of SO₄²⁻ was noticed which might be due to contribution from industrial activities responsible for SO₂ emission. At this site, influence of five types of airmass trajectories was noticed i.e. i) C.I.O. (Central part of Indian Ocean)-when air masses blown from Maldives and nearby region of central Indian ocean. These airmasses had higher concentrations of nss Ca²⁺ which did not show any adverse impact on the pH; ii) N.W.I.O.(North-West Indian Ocean)-when airmasses travelled from oceanic region close to north-east Africa. These airmassses had higher concentrations of nss sulphate and nitrate and gave rise to acid rain; iii) S.W.I.O. (South -West Indian Ocean)- when airmasses came from southern part of Indian ocean (close to Mauritius). During these airmasses, rain water samples had almost equal ratio of nss SO₄²⁻ and nss Ca²⁺ similar to N.W.I.O but very low NO₃⁻ ; iv) Gulf-when airmasses were observed coming from Gulf region. Although these airmasses contributed only 2% of the total number of samples but carried high amount of nss SO₄²⁻ which gave rise to acid rain. The second lowest pH was observed during these airmasses which might be due to very high nssSO₄²⁻/nssCa²⁺ ratios; v) N.W.I.O. + S.W.I.C. (North-West Indian Ocean+South-West Indian Continental)- when airmasses originated from north-west Indian Ocean travelling towards south continental part of India and then arriving to the site. During these airmasses, samples showed typical influence of urban activities having high concentrations of nss SO₄²⁻ and NO₃⁻ leading to the lowest pH of rain water.     

Precipitation chemistry and corresponding transport patterns of influencing air masses at Huangshan Mountain in East China

One hundred and ten samples of rainwater were collected for chemical analysis at the summit of Huangshan Mountain, a high-altitude site in East China, from July 2010 to June 2011. The volume-weighted-mean （VWM） pH for the whole sampling period was 5.03. SO2- and Ca2＋ were the most abundant anion and cation, respectively. The ionic concentrations varied monthly with the highest concentrations in winter/spring and the lowest in summer. Evident inter-correlations were found among most ions, indicating the common sources for some species and fully mixing characteristics of the alpine precipitation chemistry. The VWM ratio of [SO]-]/[NO3] was 2.54, suggesting the acidity of rainwater comes from both nitric and sulfuric acids. Compared with contemporary observations at other alpine continental sites in China, the precipitation at Huangshan Mountain was the least polluted, with the lowest ionic concentrations. Trajectories to Huangshan Mountain on rainy days could be classified into six groups. The rainwater with influencing air masses originating in Mongolia was the most polluted with limited effect. The emissions of Jiangxi, Anhui, Zhejiang and Jiangsu provinces had a strong influence on the overall rain chemistry at Huangshan Mountain. The rainwater with influencing air masses from Inner Mongolia was heavily polluted by anthropogenic pollutants.     

抚顺市区酸雨分布特征研究

降水酸度在一定程度上反映了降水和大气的污染程度。以煤烟型城市抚顺为研究对象,分析了抚顺市区降水污染的现状及降水pH值的频率、时间、空间的分布特征,以此为城市环境治理提供参考依据。结果表明:抚顺的酸雨主要出现在10月和12月,降水污染主要受局地影响。降水月平均pH值与同期降水量有关,酸雨频率的季节分布与空气中的SO2和NOX浓度的季节分布状况相一致。     

A Long Term Study on Chemical Composition of Rainwater at Dayalbagh, a Suburban Site of Semiarid Region

Rainwater samples were collected for the monsoon period of 1988 and 1991–1996 at Dayalbagh (Agra), a suburban site situated in semiaridregion. The mean pH was 7.01 ±1.03 well above 5.6, which is the reference pH. Concentration of Ca²⁺ was observed to be highest followed by Mg²⁺, NH₄ ⁺,SO₄ ^2–, Cl^–,NO₃ ^–, Na⁺, F^– and K⁺. The ratios of SO₄ ^2– + NO₃ ^– andCa²⁺ + Mg²⁺ (TA/TC) have been considered as indicatorfor acidity. In the Agra region ratio of TA/TC is quite below 1.0 indicating alkaline nature of rainwater. The lowest value of 0.24 was observed in 1991 likely due to the lowest rain depth of the decade. The highest value of 0.54 was observed in 1996, a year with a large rain depth and increase in line (vehicular traffic) and area sources (population growth). Good correlation between Ca²⁺ and NO₃ ^–,Ca²⁺ and SO₄ ^2– andSO₄ ^2– and NO₃ ^–,indicates that wind carried dust and soil play a significant role in neutralization of precipitation acidity.     

On the variability and correlation of surface ozone and carbon monoxide observed in Hong Kong using trajectory and regression analyses

This paper investigates, the variability and correlation of surface ozone (Os) and carbon monoxide (CO) observed at Cape D'Aguilar in Hong Kong from 1 January 1994 to 31 December 1995. Statistical analysis shows that the average O3 and CO mixing ratios during the two years are 32±17ppbv and 305±191 ppbv, respectively. The O3/CO ratio ranges from 0.05 to 0.6 ppbv/ppbv with its frequency peaking at 0.15. The raw dataset is divided into six groups using backward trajectory and cluster analyses. For data assigned to the same trajectory type, three groups are further sorted out based on CO and NOX mixing ratios. The correlation coefficients and slopes of O3/CO for the 18 groups are calculated using linear regression analysis. Finally, five kinds of air masses with different chemical features are identified: continental background (CB), marine background (MB), regional polluted continental (RPC), perturbed marine (P*M), and local polluted (LP) air masses. Further studies indicate that O3 and CO in the conti     

Tracking emission sources of sulfur and elemental carbon in Hong Kong/Pearl River Delta region

The Tagged Species Source Apportionment (TSSA) algorithm is applied to study contributions to pollutants PM sulfate, SO2 and elemental carbon (EC) in Hong Kong by emitting sectors as well as non-emitting sources within and beyond the Pearl River Delta (PRD) region. We look at three areas of Hong Kong: western new towns, central downtown, and eastern countryside. Pollutant transport from beyond the PRD influenced all three areas during January and October 2004 but the source sectors impacting the three areas were different. Specifically, power plant SO2 from Hong Kong and Shenzhen, and vehicle EC from Shenzhen contribute to 11?~?66?% of SO2 concentration, and 33?~?75?% of EC concentration in the western new towns, respectively. Ships in and around Hong Kong contribute 8?~?56?% to the sulfate concentration in the downtown area, while local moving vehicles take up 28?~?81?% of the EC concentration there. The study also shows that diurnal variation of planetary boundary layer (PBL) causes day-night difference in SO2 by as much as 50?%. In addition, 13?~?38?% of all SO2 emissions have been converted to PM sulfate.     

The influence of meteorology on the organic and inorganic properties of aerosols in Hong Kong

The organic and inorganic species in total suspended particulates (TSP) collected from June to December in 1998 in Hong Kong were identified by gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS) to investigate the sources of Hong Kong aerosols and the mechanisms that control the chemical compositions and variations in the atmosphere. These samples were classified according to the climate: wet, dry under the influence of southerly winds from the sea (Dry-S) and dry under the influence of northerly winds from the continent (Dry-N). There were significant increases of materials from crustal, biogenic and pollution sources in the Dry-N period by a factor of 5, 4, and 2, respectively. Since the crustal tracers (e.g., Al, Fe) could be from coal flyash, the estimate of crustal material in the Dry-N period may include some materials from pollution source. Therefore, a positive correlation between crustal and pollution elements was observed. From the analysis of solvent-extractable organics (SEOC), microbial and meat cooking sources showed slight increase (1.2-fold). Higher levels of plant wax materials in the Dry-N period were probably due to the higher wind speed during the winter monsoon. The percentage of crustal material in TSP was 47% in the Dry-N period, and only 22% in the wet season and the Dry-S period. Plant wax materials (biogenic source) had a higher percentage in the Dry-N period (39% of SEOC) while microbial and meat cooking sources accounted for 49% of SEOC in the wet season. This study revealed that wind direction and precipitation had a significant influence not only on the concentrations but also on the chemical compositions and sources of Hong Kong aerosols.     

Thymol as a Biocide in Japanese Rainwater

Rainwater samples (wet-only; event samples) collected in Niigata in late autumn 1996 and springtime 1997 were used to assess the effectiveness of thymol as a biocide in Japanese rainwater. Upon collection each rainwater sample was divided into sub-samples, with thymol added to one sub-sample. Sub-samples with and without thymol were shipped to CSIRO, Australia, for chemical analysis. Comparison of analytical results for each pair of sub-samples proved the effectiveness of thymol in preventing biological action in this region where effects of rainwater microflaura and fauna on rainwater composition have not before been studied. Sub-samples without thymol exhibited lowered electrical conductivity, loss of the cations H⁺ and NH ₄ ^- , and loss of the anions HCOO^-, CH₃COO^-, C₂O ₄ ^2- , CH₃SO ₃ ^- and PO ₄ ^3- . Nitrate showed no change in all but one of the samples, indicating that ammonia was the preferred source of nitrogen for the biological processes that consumed the rainwater organic acids and phosphate. These results suggest that thymol is a suitable rainwater biocide for use under Japanese conditions.     

Diurnal and seasonal variations of CO2 fluxes and their climate controlling factors for a subtropical forest in Ningxiang

In this study, the diurnal and seasonal variations of CO2 fluxes in a subtropical mixed evergreen forest in Ningxiang of Hunan Province, part of the East Asian monsoon region, were quantified for the first time. The fluxes were based on eddy covariance measurements from a newly initiated flux tower. The relationship between the CO2 fluxes and climate factors was also analyzed. The results showed that the target ecosystem appeared to be a clear carbon sink in 2013, with integrated net ecosystem CO2exchange(NEE), ecosystem respiration(RE), and gross ecosystem productivity(GEP) of-428.8, 1534.8 and1963.6 g C m-2yr-1, respectively. The net carbon uptake(i.e. the-NEE), RE and GEP showed obvious seasonal variability,and were lower in winter and under drought conditions and higher in the growing season. The minimum NEE occurred on12 June(-7.4 g C m-2d-1), due mainly to strong radiation, adequate moisture, and moderate temperature; while a very low net CO2 uptake occurred in August(9 g C m-2month-1), attributable to extreme summer drought. In addition, the NEE and GEP showed obvious diurnal variability that changed with the seasons. In winter, solar radiation and temperature were the main controlling factors for GEP, while the soil water content and vapor pressure deficit were the controlling factors in summer. Furthermore, the daytime NEE was mainly limited by the water-stress effect under dry and warm atmospheric conditions, rather than by the direct temperature-stress effect.     

Source identification and variation in the chemical composition of rainwater at coastal and industrial areas of India

Studies on precipitation chemistry were carried out to understand the nature and sources of rainwater at Rameswaram and NTPC Dadri, India representing coastal and industrial region during 2010. The rainwater samples, collected at these locations, were analyzed for major ions and pH. The data were assessed for its quality. The pH of rainwater at two locations varied from 5.53 to 6.73 and 5.1–6.6, indicating alkaline nature except a few acidic events. The dominance of Cl− and Na+ were observed in coastal environment whereas dominance of Ca2+ was seen in industrial environment. The nss-SO42- (37.9%) at Rameswaram is less influenced by anthropogenic activities whereas nss-SO42- (72.5%) at NTPC Dadri is influenced by pollutants emitted by anthropogenic sources. The ratio of H+/(NO3- + SO42-) was observed as 0.04 and 0.008 for Rameswaram and NTPC Dadri which is close to zero, indicate 99.99% of acidity was neutralized in precipitation. Ca2+, NH4+ and Mg2+ play an important role in neutralization of acidic ions in rainwater. For source identification, correlation matrix analysis was established, which showed that in general, at both sites; correlation between the acidic ions SO42- and NO3- indicating their origin from similar sources, because of the similarity in their behavior in precipitation and the co-emissions of their precursors SO2 and NOX. The correlation coefficient of (SO42- + NO3-) vs (Ca2+) at Rameswaram and NTPC Dadri were 0.77 and 0.87 indicates that CaCO3 is the major neutralizing agent for both the region. Overall, the influence of marine, terrestrial and anthropogenic sources was observed in the rain events.