Controls on the chemical and isotopic compositions of urban stormwater in a semiarid zone

The temporal variations in the chemical and isotopic compositions of urban stormwater under different land uses, and their dependence on physical parameters such as precipitation intensity, stormwater discharge, cumulative stormwater volumes and the size of the drainage area, were investigated in the coastal city of Ashdod, Israel. During 2000/2001 and 2001/2002, 46 stormwater events were intensively monitored for precipitation distribution and intensity at three stations across the city, and for stormwater discharge at seven stations draining 85% of the city area. Sixty-eight and 202 precipitation samples were collected and analyzed for chemical and isotopic compositions, respectively, as were 186 stormwater samples, collected from the drains during 15 of the 46 events. Land use had only a minor effect on the concentrations of major ions and trace elements. Conversely, the concentrations and variety of volatile and semi-volatile organic compounds were significantly higher in stormwater generated in the industrial area than in that draining from residential areas. Ion and trace-metal concentrations were very low (below drinking-water standards) in 97% of the stormwater samples collected from all drains. Stormwater concentrations were higher at stations draining a larger area, thereby linking concentrations to the length of the stormwater flow paths. A first-flush effect was documented on both a seasonal and event basis for both ions and trace elements. The high concentrations of fecal coliform bacteria exceeded the drinking-water standards and displayed a random pattern. The isotopic ratios of oxygen and hydrogen in the stormwater suggest very little exposure to the atmosphere, resulting in very limited fractionation. The presence of fecal coliforms, ammonium in some samples, and specific ratios of oxygen and nitrogen isotopes, suggest that although the sewer and stormwater-collection systems are separated, wastewater, possibly from overflowing sewers, contributed to the drained stormwater.     

Hydrogeochemistry of seepage water collected within the Youngcheon diversion tunnel,Korea: source and evolution of SO4‐rich groundwater in sedimentary terrain

In the Youngcheon Diversion Tunnel area, South Korea, 46 samples of tunnel seepage water (TSW) and borehole groundwater were collected from areas with sedimentary rocks (mainly sandstone and shale) and were examined for hydrogeochemical characteristics. The measured SO₄ concentrations range widely from 7·7 to 942·0 mg/l, and exceed the Korean Drinking Water Standard (200 mg/l) in about half the samples. The TDS (total dissolved solid) content generally is high (171–1461 mg/l) from more shale‐rich formations and also reflects varying degrees of water–rock interaction. The water is classified into three groups: Ca? SO₄ type (61% of the samples collected), Ca? SO₄? HCO₃ type (15%) and Ca? HCO₃ type (24%). The Ca? HCO₃ type water (mean concentrations=369 mg/l Ca, 148 mg/l HCO₃ and 23 mg/l SO₄) reflected the simple reaction between CO₂‐recharged water and calcite, whereas the more SO₄‐rich nature of Ca? SO₄ type water (mean concentrations=153 mg/l Ca, 66 mg/l HCO₃ and 416 mg/l SO₄) reflected the oxidation of pyrite in sedimentary rocks and fracture zones. Pyrite oxidation resulted in precipitation of amorphous iron hydroxide locally within the tunnel as well as in high concentrations of Ca (mean 153 mg/l) and Na (mean 49 mg/l) for TSW, and is associated with calcite dissolution resulting in pH buffering. The pyrite oxidation required for the formation of Ca? SO₄ type water was enhanced by the diffusion of oxygenated air through the fractures related to the tunnel's construction. The subsequent outgassing of CO₂ into the tunnel resulted in precipitation of iron‐bearing carbonate. Copyright © 2001 John Wiley & Sons, Ltd.     

High sulphate concentrations in squeezed Boom Clay pore water: evidence of oxidation of clay cores

Pore water has been extracted from Boom Clay by mechanical squeezing. Clay cores were obtained from various boreholes, all drilled at the SCK·CEN domain (Mol, Belgium).In contrast to pore water collected from piezometers, high sulphate concentrations are measured in the squeezed pore water. The lowest sulphate concentrations (<60 mg/l) were measured in pore waters squeezed immediately after drilling. Higher sulphate concentrations were often measured in the pore water when the clay cores were preserved for some time (generally <500 mg/l SO₄²⁻, but sometimes up to 20,000 mg/l SO₄²⁻). Nevertheless, a relation between preservation time and sulphate content could not be retrieved. However, major ion concentrations were obviously correlated with the sulphate content in the squeezed waters. The observed evolution in chemical composition were explained by water–rock interactions considering the pyrite oxidation and the subsequent ion exchange and mineral dissolution reactions.     

Changing properties of precipitation concentration in the Pearl River basin, China

In this paper, precipitation concentrations across the Pearl River basin and the associated spatial patterns are analyzed based on daily precipitation data of 42 rain gauging stations during the period 1960–2005. Regions characterized by the different changing properties of precipitation concentration index (CI) are identified. The southwest and northeast parts of the Pearl River basin are characterized by lower and decreasing precipitation CI; the northwest and south parts of the study river basin show higher and increasing precipitation CI. Higher but decreasing precipitations CI are found in the West and East River basin. Comparison of precipitation CI trends before and after 1990 shows that most parts of the Pearl River basin are characterized by increasing precipitation CI after 1990. Decreasing precipitation CI after 1990 (compared to precipitation CI changes before 1990) is observed only in a few stations located in the lower Gui River and the lower Yu River. Significant increasing precipitation CI after 1990 is detected in the West River, lower North River and upper Beipan River. These changes of precipitation CI in the Pearl River basin are likely to be associated with the consequences of the well-evidenced global warming. These findings can contribute to basin-scale water resource management and conservation of ecological environment in the Pearl River basin.     

Comparative characteristics of ion and electron precipitation in the dawn and dusk sectors

Characteristics of ion and electron precipitations in the dawn and dusk sectors are investigated by DMSP F6 and F7 satellite observations. It is shown that in the dusk sector the positions of electron and ion precipitation boundaries are nearly coincident for all levels of magnetic activity; however the latitudinal distribution of energy fluxes indicates that the positions of electron and ion precipitation maxima are spatially separated. Maximum energy fluxes of ions is observed at the equatorial precipitation boundary, while those of electrons at the poleward one. In the dawn sector, the electron precipitation region is 3°–4° wider than that of ions. The isotropy boundary in the dusk sector is located in the region of diffuse precipitation (DAZ) near its poleward boundary for all levels of magnetic activity, while in the dawn sector it falls in the region of structured precipitations (AOP). Electron precipitations are dominating in the dawn sector. Here in the region of diffuse precipitation (DAZ), the ion energy fluxes Fi make less than 5% as compared to the electron energy flux Fe. In the region of structured precipitations (AOP), the portion of Fi decreases with increasing magnetic activity from ~10–20% for AL ≈ -100 nT to <5% for AL ≈ -1000 nT. As for the dusk sector, in the AOP region, electron precipitations are dominating as well, while in the DAZ region the ion energy fluxes are significant. In the 1500–1800 MLT sector, the ratio Fi/Fe increases from ~0.7 to ~3.0 with AL changing from -100 nT to -1000 nT.     

Assessment of the quantitative and qualitative buffer function of an alluvial wetland: hydrological modelling of a large floodplain (Garonne River,France)

For 2 years, water flow‐patterns in the Garonne floodplain of south‐western France were studied in the field and through hydrodynamic modelling (MARTHE Hydrodynamic Software developed by BRGM). Water flow‐paths and the transport of dissolved elements between river and aquifer have been investigated and modelled. In order to quantify the buffer function of the alluvial floodplain, we focused our work on the effect of a major flood on the water flow‐direction, and on nitrate transport. Thus, we showed that the effect of a large flood in the river was rapidly lost with increasing distance from the river. During the observation period, a hydrologically active strip only 300 m wide on either side of the riverbed played a buffering role in absorbing the flood crest. It was also found that meanders favour the exchange between river and alluvial aquifer, shown by the creation of bypasses between the upstream and downstream parts of meanders. This, in turn, contributes to a dilution of nitrates in the phreatic aquifer, which here has higher nitrate content than the surface water; such dilution may result in an overestimation of the denitrification process in the wooded riverbanks. The coupling of chemical measurements—especially of chlorides and nitrate—with modelling of the dissolved‐element transport allows us to establish the water balance for the riparian wetland, and to separate the effect of dilution and denitrification on nitrate concentration. This indicated the existence of areas in the riparian wetlands where denitrification is particularly strong, leading to reductions in nitrate concentrations of 10 to 30 mg/l NO₃^? during the flood. Copyright © 2003 John Wiley & Sons, Ltd.     

Tritium in atmospheric precipitation over the European territory of CIS as an indicator of climatic changes

Many-year observational data on the ³H content of mean monthly precipitation at the network of stations in eight natural-climatic belts of the European part of the CIS are studied. Relationships between ³H concentrations and the climatic characteristics are analyzed. The ratio of the ³H content of precipitation in July to that in December is shown to be the best indicator of the atmospheric moisture transfer. The regular variations in the ³H content of precipitation with time (1980–1994) recorded in different natural-climatic belts testify that the western source of atmospheric moisture intensified during the above period and the climate on the European territory of CIS became warmer.Translated from Vodnye Resursy, Vol. 32, No. 2, 2005, pp. 247–253.Original Russian Text Copyright © 2005 by Vlasova, Ferronskii.     

The Likelihood of Coliform Bacteria in NJ Domestic Wells Based on Precipitation and Other Factors

The influence of precipitation on coliform bacteria detection rates in domestic wells was investigated using data collected through the New Jersey Private Well Testing Act. Measured precipitation data from the National Weather Service (NWS) monitoring stations was compared to estimated data from the Multisensor Precipitation Estimate (MPE) in order to determine which source of data to include in the analyses. A strong concordance existed between these two precipitations datasets; therefore, MPE data was utilized as it is geographically more specific to individual wells. Statewide, 10 days of cumulative precipitation prior to testing was found to be an optimal period influencing the likelihood of coliform detections in wells. A logistic regression model was developed to predict the likelihood of coliform occurrence in wells from 10 days of cumulative precipitation data and other predictive variables including geology, season, coliform bacteria analysis method, pH, and nitrate concentration. Total coliform (TC) and fecal coliform or Escherichia coli (FC/EC) were detected more frequently when the preceding 10 days of cumulative precipitation exceeded 34.5 and 54 mm, respectively. Furthermore, the likelihood of coliform detection was highest in wells located in the bedrock region, during summer and autumn, analyzed with the enzyme substrate method, with pH between 5 and 6.99, and (for FC/EC but not TC) nitrate greater than 10 mg/L. Thus, the likelihood of coliform presence in domestic wells can be predicted from readily available environmental factors including timing and magnitude of precipitation, offering outreach opportunities and potential changes to coliform testing recommendations.     

Climatic factors controlling chemical and isotopic characteristics of precipitation in Syria

The chemical and isotopic composition of monthly composite rain samples collected at 13 meteoric stations in Syria during two hydrological cycles from 1991 to 1993 have been measured. The chemical analysis of the samples revealed at a number of stations pollution due to industry and sand storms. The temporal and spatial variation of the isotopic composition has been found to be comparable with one of the neighbouring countries such as Jordan and others. The average weighted oxygen‐18 and deuterium values are − 7·5 and − 39·11‰, respectively, and the deuterium excess is 21‰ . The individual isotope values can be divided into two groups. One group is represented by winter precipitation and fits closely the Mediterranean Meteorological Water Line (MMWL). Thus, for winter precipitation, condensation of Mediterranean water vapour appears to be the dominating isotope fractionation process. The other group represents spring precipitation and is spread along an evaporation line below the MMWL, thus indicating the influence of sub‐cloud evaporation. The d‐excess has been found to be lower in the north of Syria (19·9‰ at Tartous, 18·1‰ at Jarablous) than in the south of the country (23·4‰ at Sweida, 24·1‰ at Izra) where Mediterranean air mass dominates. The d‐excess of precipitation in neighbouring countries is also close to the average value of the eastern Mediterranean basin of 22‰ , e.g. for Jordan the value is 23‰ , which signifies that Mediterranean water vapour is, for all these countries, the dominant source of precipitation. The tritium content of precipitation was found to increase with distance from the coast (5·3 TU at coastal station Tartous, 8·8 TU at continental station Palmyra). Low tritium content and high d‐excess at coastal stations clearly indicate a Mediterranean air moisture source. Copyright © 2010 John Wiley & Sons, Ltd.     

Precipitazioni intense al margine meridionale delle Alpi

Riassunto In questo lavoro sono studiate specialmente le precipitazioni intense (quantità giornaliere 50 mm) del periodo 1901–1950, mediante 6 stazioni del margine meridionale delle Alpi, confrontate con una stazione del nord delle Alpi (Zurigo) e una della Lombardia (Milano). Si trova che le precipitazioni intense sul versante sud delle Alpi sono molto più frequenti che nelle stazioni di confronto e che al margine meridionale delle Alpi è considerevole l'apporto delle precipitazioni intense alla somma totale.

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Summary In the present paper is being examined particularly the frequency of large precipitations (daily amounts 50 mm) on the southern side of the Swiss Alps (period 1901–1950). For this purpose the conditions of precipitation of six stations in Southern Switzerland are compared with those of one station on the northern side of the Alps (Zürich) and of one in Lombardy (Milan). It is shown that the frequency of large precipitations is much higher on the southern slope of the Alps than on the stations mentioned in comparison. Also that the share of the amount of large precipitations on the total amount is rather considerable.

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Zusammenfassung In der vorliegenden Arbeit werden vor allem die grossen Niederschläge (Tagesmengen 50 mm) der Periode 1901–1950 anhand von 6 Stationen auf der Alpensüdseite untersucht und mit je einer Station auf der Alpennordseite (Zürich) und in der Lombardei (Mailand) verglichen. Dabei zeigt sich, dass grosse Niederschläge an der Südabdachung der Alpen viel häufiger sind als an den Vergleichstationen und dass der Anteil der grossen Niederschläge an der Gesamtmenge am Alpensüdfuss beträchtlich ist.

     

“Man and Biosphere” — Studies on Sikkim Himalayas. Part 2: Acute Toxity of Mixed Copper-Zinc Solutions on Common Carp,Cyprinus carpio (LINN.)

In batch experiments for 6 to 48 h, individuals of Cyprinus carpio (2 g individual weight) were exposed to mixed solutions of copper and zinc sulphate: pH = 6.3, temperature 15 °C, 6.8 mg/l O₂, 7.1 mg/l Ca²⁺, 0.7 mg/l Mg²⁺. The LC₅₀ for the individual substances on exposures of 24 and 48 h amount to 9.04 and 7.28 mg/l, resp., of Zn and 0.11 and 0.095 mg/l, resp., of Cu. The sum of the biological activity of the two kinds of metal ions is assessed according to MARKING'S index: at low concentrations of the mixed solutions the two metals show an additive effect, at higher concentrations a synergistic effect occurs.     

Investigation of spatial and temporal variability of precipitation in Iran over the last half century

Investigation of the precipitation phenomenon as one of the most important meteorological factors directly affecting access to water resources is of paramount importance. In this study, the precipitation concentration index (PCI) was calculated using annual precipitation data from 34 synoptic stations of Iran over a 50-year period (1961–2010). The trend of precipitation and the PCI index were analyzed using the Mann–Kendall test after removing the effect of autocorrelation coefficients in annual and seasonal time scales. The results of zoning the studied index at annual time scale revealed that precipitation concentration follows a similar trend within two 25-year subscales. Furthermore, the PCI index in central and southern regions of the country, including the stations of Kerman, Bandarabbas, Yazd, Zahedan, Shahrekord, Birjand, Bushehr, Ahwaz, and Esfahan indicates a strong irregularity and high concentration in atmospheric precipitations. In annual time scale, none of the studied stations, had shown regular concentration (PCI < 10). Analyzing the trend of PCI index during the period of 1961–2010 witnessed an insignificant increasing (decreasing) trend in 16 (15) stations for winter season, respectively, while it faced a significant negative trend in Dezful, Saghez, and Hamedan stations. Similarly, in spring, Kerman and Ramsar stations exhibited a significant increasing trend in the PCI index, implying significant development of precipitation concentration irregularities in these two stations. In summer, Gorgan station showed a strong and significant irregularity for the PCI index and in autumn, Tabriz and Zahedan (Babolsar) stations experienced a significant increasing (decreasing) trend in the PCI index. At the annual time scale, 50 % of stations experienced an increasing trend in the PCI index. Investigating the changes in the precipitation trend also revealed that in annual time scale, about 58 % of the stations had a decreasing trend. In winter, which is the rainiest season in Iran, about 64 % of stations experienced a decreasing trend in precipitation that caused an increasing trend in PCI index. Comparing the spatial distribution of PCI index within two 25 years sub-periods indicated that the PCI index of the second sub-period increased in the spring time scale that means irregularity of precipitation distribution has been increased. But in the other seasons any significant variations were not observed. Also in the annual time scale the PCI index increased in the second sub-period because of the increasing trend of precipitation.     

Contamination of groundwater under cultivated fields in an arid environment, central Arava Valley, Israel

The purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment (precipitation of 50 mm/year) due to cultivation. Additional aims were to study the fate of N, K, and other ions along the whole hydrological system including the soil and vadose zone, and to compare groundwater in its natural state with contaminated groundwater (through the drilling of several wells).

A combination of physical, chemical, and isotopic analyses was used to describe the hydrogeological system and the recharge trends of water and salts to the aquifers. The results indicate that intensive irrigation and fertilization substantially affected the quantity and quality of groundwater recharge. Low irrigation efficiency of about 50% contributes approximately 3.5–4 million m³/year to the hydrological system, which corresponds to 0.65 m per year of recharge in the irrigated area, by far the most significant recharge mechanism.

Two main contamination processes were identified, both linked to human activity: (1) salinization due to circulation of dissolved salts in the irrigation water itself, mainly chloride, sulfate, sodium and calcium, and (2) direct input of nitrate and potassium mainly from fertilizers.

The nitrate concentrations in a local shallow groundwater lens range between 100 and 300 mg/l and in the upper sub-aquifer are over 50 mg/l. A major source of nitrate is fertilizer N in the excess irrigation water. The isotopic compositions of δ¹⁵N–NO₃ (range of 4.9–14.8‰) imply also possible contributions from nearby sewage ponds and/or manure. Other evidence of contamination of the local groundwater lens includes high concentrations of K (20–120 mg/l) and total organic carbon (about 10 mg/l).     

Distribution and fluxes of metals in the St. Lawrence River from the outflow of Lake Ontario to Québec City

Six anchor stations in the St. Lawrence River from the outflow of Lake Ontario to Quebec City, were occupied for ca. 24 hours in June 1987 during low flow conditions. Samples of water and suspended particulate matter were separated by continuous-flow centrifugation, and were collected every two hours.During this sampling period, fluxes of dissolved forms of zinc, copper and nickel increased in Lac St. François and downstream relative to the sum of the fluxes for the two upstream stations at the outflow of Lake Ontario. Increases in the flux of dissolved zinc and copper were pronounced below Montreal and above Lac St. Pierre. For particulate forms of metals, all five metals show that there are significant inputs in the section of the St. Lawrence River between Lac St. François and the station just above the entrance to Lac St. Pierre.The average concentrations of dissolved cadmium, lead, zinc, copper and nickel ranged from 7–23 ng/l; 9–35 ng/l; 0.434–0.939 g/l; 0.15–0.89 g/l and 0.58–1.12 g/l respectively.Regression analysis of the dissolved and particulate metal concentrations suggests that the concentration of dissolved cadmium, lead, zinc and nickel can be predicted from the regression equation and the determination of particulate metal concentration. This prediction appears to be independent of the suspended particulate matter concentration which varies from ca. 1 to 10 mg/l from the outflow of Lake Ontario to Québec City.     

Long-term chemical effects of petroleum in south Louisiana wetlands—I. Organic carbon in sediments and waters

The chemical effects of chronic petroleum input into a shallow water marsh were examined by measuring hydrocarbon levels and dissolved organic carbon content of sediments associated with two active oil fields in south Louisiana. Annual levels of total organic carbon in the surface waters of the oil fields were higher by 1 mg C/l. in the salt marsh and 5 mg C/l. in the fresh marsh than the respective controlsites. Average dissolved organic carbon concentrations in the interstitial waters of cores taken within the oil field environments were 105% higher than the control in the salt marsh and 43% higher than the control in the fresh marsh. Significantly lower ratios of C₁₇ to pristane occurred in both oil field sediments; however, average odd-even predominance values were not indicative of petroleum contaminated sediments. The results indicate that microbial processes are responsible for dissolution of petroleum into dissolved organic carbon and that dissolved organic carbon concentrations may be a more significant measure of chronic petroleum input than hydrocarbon distribution.     

Organochlorines and other environmental contaminants in muscle tissues of sportfish collected from San Francisco Bay

Edible fish species were collected from 13 locations throughout San Francisco Bay, during the spring of 1994, for determination of contaminant levels in muscle tissue. Species collected included white croaker, surfperch, leopard and brown smoothhound sharks, striped bass, white sturgeon and halibut. 66 composite tissue samples were analysed for the presence of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (P0CBs), pesticides, trace elements and dioxin/furans. The US EPA approach to assessing chemical contaminant data for fish tissue consumption was used for identifying the primary chemicals of concern. Six chemicals or chemical groups were found to exceed screening values (SVs) established using the US EPA approach. PCBs (as total Aroclors) exceeded the screening level of 3 ng g⁻¹ in all 66 muscle tissue samples, with the greatest concentrations (638 ng g⁻¹) found near San Francisco's industrial areas. Mercury was elevated (> 0.14 μg g⁻¹) in 40 of 66 samples with the greatest concentrations (1.26 μg g⁻¹) occurring in shark muscle tissues. Concentrations of the organochlorine pesticides dieldrin, total chlordane and total dichlorodiphenyltri-chloroethane (DDT) exceeded screening levels in a number of samples. Dioxin/furans (as toxic equivalent concentrations (TEQ's)) were elevated (> 0.15 pg g⁻¹) in 16 of the 19 samples analysed. Fish with high lipid content (croaker and surfperch) in their muscle tissue generally exhibited higher organic contaminant levels while fish with low lipid levels (halibut and shark) exhibited lower organic contaminant levels. Tissue samples taken from North Bay stations most often exhibited high levels of chemical contamination. The California Office of Health Hazard Assessment is currently evaluating the results of this study and has issued an interim Health Advisory concerning the human consumption of fish tissue from San Francisco Bay.     

Trend analysis in Turkish precipitation data

This study aims to determine trends in the long‐term annual mean and monthly total precipitation series using non‐parametric methods (i.e. the Mann–Kendall and Sen's T tests). The change per unit time in a time series having a linear trend was estimated by applying a simple non‐parametric procedure, namely Sen's estimator of slope. Serial correlation structure in the data was accounted for determining the significance level of the results of the Mann–Kendall test. The data network used in this study, which is assumed to reflect regional hydroclimatic conditions, consists of 96 precipitation stations across Turkey. Monthly totals and annual means of the monthly totals are formed for each individual station, spanning from 1929 to 1993. In this case, a total of 13 precipitation variables at each station are subjected to trend detection analysis. In addition, regional average precipitation series are established for the same analysis purpose. The application of a trend detection framework resulted in the identification of some significant trends, especially in January, February, and September precipitations and in the annual means. A noticeable decrease in the annual mean precipitation was observed mostly in western and southern Turkey, as well as along the coasts of the Black Sea. Regional average series also displayed trends similar to those for individual stations. Copyright © 2005 John Wiley & Sons, Ltd.     

1950s以来鄱阳湖流域降水变化趋势及其持续性特征

以鄱阳湖流域1950s至2005年10个台站的日降水量为基础,采用距平分析、Mann-Kendall非参数检验对鄱阳湖流域1950s以来的年、季降水特征和变化趋势进行分析,并以此为基础,结合Hurat指数,从3年、5年、10年三个时间尺度上分析该流域未来降水的变化趋势.结果表明,鄱阳湖流域年内降水分配不均,年际变化较为...     

Solute concentrations in the lower niger river and the source rock contribution

Water quality analyses for the Niger River for the 1980/81 hydrological year are presented. The samples were collected from the main river at Lokoja, and from two main tributaries, the Kaduna and the Benue Rivers. Different water types were distinguished by the concentrations of major ions. The type Ca > Na > Mg > K - HCO₃ > SO₄ > Cl was represented at all stations during at least part of the year. Chloride was found to dominate the sulphate ion in the Kaduna and Niger, while the Benue maintained a higher concentration of sulphate relative to chloride all year round. Distinct patterns of seasonal variation in the ion concentrations were observed, particularly for the samples collected at Lokoja. Low ion concentrations were prominent during periods of high discharge, while low flow periods coincided with high dissolved ion concentrations. The contribution of rainwater to the total dissolved solids in the river waters was assessed indirectly using rainwater chemistry data from the Gulf of Guinea. The estimated rainwater contribution to the Lower Niger amounts to 5.15 mg 1^?1. Geochemical weathering calculations involving reactions of the four major minerals of granitic rocks - anorthite, biotite, albite, and K-feldspar - with carbon dioxide and water, can account for the average water composition of the Lower Niger. The proportion of the ionic components was also related to the occurrence of the respective element in the minerals.     

Back Trajectory Analysis of Precipitation Chemistry in the Urban and Forest Areas of Istanbul,Turkey

There are many influences on precipitation chemistry and its variation. The transport paths of air masses before rainfall provide useful knowledge for evaluating and understanding the results of the analysis of the chemical compositions of precipitation. As a consequence, it is important to determine the variation of the chemical composition of rainwater by back trajectory analysis for estimating the source of the emissions. In this study, the rainwater samples were collected using specially designed collectors between November 1997 and June 1998 in the urban and forest areas of Istanbul. The rainwater samples were analyzed for major ion concentrations and pH. The volume‐weighed mean pH values were 5.8. The rainwater samples were classified to determine the source region of pollutants in rainwater using synoptic maps. In general, the results of the analysis on the chemical concentrations of precipitation during the measurement period showed that most of ions reached Istanbul from the directions of W‐SW, NW‐W, and NE‐N, respectively.