Effect of agriculture on water quality of Lake Biwa tributaries, Japan

We investigated the effects of natural environments and human activity on Lake Biwa, central Japan. We determined the concentrations of 19 elements and the compositions of stable S and Sr isotopes in the main tributaries of the lake and compared them with the corresponding values obtained from the lake water during the circulation period. Results of a principal component analysis indicated that the components dissolved in the lower reaches of the tributaries can be divided into group 1 (HCO(3), SO(4), NO(3), Ca, Mg, Sr) and group 2 components (Cl, Br, Na, K, Ba, Rb, Cs). The concentrations of group 1 components were high in the rivers of the southern area, which is urbanized and densely populated, and the eastern area, which consists of plains where agriculture predominates, compared with the rivers of the northern and western areas, which are mostly mountainous and sparsely populated. The concentrations of group 2 components tended to be high in the river water of industrial areas. The delta(34)S values of SO(4) in the river water converged to 0+/-2 per thousand as the SO(4) concentration increased and, excluding the areas where limestone is extensively distributed, as the HCO(3) concentration increased. In particular, both the delta(34)S values (0+/-2 per thousand) and the (87)Sr/(86)Sr ratios (0.7117+/-0.0005) fell within narrow ranges in the small and medium rivers of the eastern plain area, where rice is widely grown. These values agreed respectively with the delta(34)S values of the fertilizers used in the Lake Biwa basin and the soil-exchangeable (87)Sr/(86)Sr in the eastern plain. The characteristics of water quality in the small and medium rivers of the eastern area can be explained by a model in which sulfuric, nitric, and bicarbonic acids generated by the decomposition of agricultural fertilizer and paddy rice selectively leached out alkaline-earth elements adsorbed on the soil and sediments of the plain or dissolved calcium carbonate enriched with Mg and Sr. Compared with tributary waters, the lake water was depleted in NO(3), owing to denitrification, and in Mn, owing to mineralization, which occur under the redox condition of bottom sediments. Excluding NO(3) and Mn, the compositions of both the dissolved elements and the Sr and S isotopes in the water of Lake Biwa can be approximately reproduced by simple mixing of the tributary water, indicating that these components provide effective indices for evaluating the relationship between the waters of the lake and its tributaries.     

三峡库区小流域(茅坪河)河水主要离子及锶地球化学组成特征与重金属污染

三峡库区河水主要离子及锶的水文地球化学组成的研究有助于认识库区水质演化地球化学行为,对保护库区水质有积极意义。本研究以三峡大坝坝下第一条支流——茅坪河河水为研究对象,对河水进行取样检测,结果显示:河水化学组成以Ca2+、Mg2+、Na+、K+和HCO3-、SO42-、Cl-为主。通过聚类分析、相关系数矩阵和piper三线图分析发现主要离子中,Ca2+、Mg2+主要来源于白云岩风化,Si2+与Na+、K+来源于钠长石和钾长石的风化,Cl-来源于硅酸盐造岩矿物的风化,Sr2+主要来源于白云岩和云英闪长岩中SrCO3和SrSO4风化。通过对重金属污染调查发现,Cu、Fe、Mn、Ni、Ag这5种重金属元素污染较重,工厂排放废水是重金属污染的主要来源。     

Evolution of anthropogenic aerosols in the coastal town of Salina Cruz, Mexico: part II particulate phase chemistry

An analysis of atmospheric gases and particles during periods of land and sea breezes in a coastal city in southwest Mexico indicates limited removal of total particle mass by deposition during periods when the air resides over the ocean. The average PM(2.5) mass concentrations for land and sea breeze samples were 25+/-1.0 and 26+/-1.0 microg m(-3), respectively. The average sum of the ion concentrations (NH(4)(+), SO(4)(2-), NO(3)(-), Na(+), Cl(-)) were 10 and 11.8 microg m(-3) for the samples taken during land and sea breeze periods. The average total carbon concentrations were 6.0 and 5.3 microg m(-3) for land and sea breeze periods. The mass of sulfate in particles of ocean origin, 3.3+/-2.8 microg m(-3), is marginally higher than those originating from the land, 2.0+/-0.8 microg m(-3), presumably as a result of the conversion of SO(2) recirculated from the city. The fraction of sulfate, nitrate and ammonium ions in rainwater samples is almost a factor of two higher than the fraction measured on filtered air samples. The rainwater also contains significant concentrations of elemental and organic carbon. This study, although extending over a period of only 15 days, with limited chemical samples, suggests that recirculation of anthropogenic particles from coastal cities should be taken into consideration when diagnosing and predicting air quality in such regions.     

Contribution of marine and continental aerosols to the content of major ions in the precipitation of the central Mediterranean

The region of the investigated receptor is situated in the southern part of the Adriatic Sea in the Mediterranean. The measuring station is located on the seashore, which, being considered as a border area, is representative for the qualitative and quantitative estimation of the influence of marine and continental aerosols on the content of major ions in precipitation. In the sampling period, precipitation in the region of the investigated receptor was more abundant during the summer and autumn than during the winter and spring. The most frequent precipitation heights were up to 20 mm, while high precipitation came exclusively from the continental region. The results of the measurements of ions readily soluble in water were used for the differentiation of marine from continental contributions of primary and secondary aerosols to their content in the precipitation. Using PCA, it was shown that main contribution of Cl(-), Na(+) and Mg(2+) came from primary marine aerosols, while the contribution from continental sources was dominant for the content of SO(4)(2-), NO(3)(-), NH(4)(+) and Ca(2+) in the precipitation. The continental origin of Ca(2+) was from a primary source, while SO(4)(2-), NO(3)(-) and NH(4)(+) were representatives of secondary aerosols produced by reactions between acid oxides and alkaline species in the atmosphere, but SO(4)(2-) and NO(3)(-) also exist in the precipitation as free acids. The origin of the trace elements Cd, Cu, Pb and Zn in the precipitation came from anthropogenic emission sources. The results obtained in this work are based on experimental data from 609 samples collected during the period 1995-2000.     

A new post-treatment process for attaining Ca2+, Mg2+, SO42- and alkalinity criteria in desalinated water

A novel post-treatment approach for desalinated water, aimed at supplying a balanced concentration of alkalinity, Ca(2+), Mg(2+) and SO(4)(2-), is introduced. The process is based on replacing excess Ca(2+) ions generated in the common H(2)SO(4)-based calcite dissolution post-treatment process with Mg(2+) ions originating from seawater. In the first step, Mg(2+) ions are separated from seawater by means of a specific ion exchange resin that has high affinity toward divalent cations (Mg(2+) and Ca(2+)) and an extremely low affinity toward monovalent cations (namely Na(+) and K(+)). In the second step, the Mg(2+)-loaded resin is contacted with the effluent of the calcite dissolution reactor and Mg(2+) and Ca(2+) are exchanged. Consequently, the excess Ca(2+) concentration in the water decreases while the Mg(2+) concentration increases. The process is stopped at a predetermined Ca(2+) to Mg(2+) ratio. All water streams used in the process are internal and form a part of the desalination plant sequence, regardless of the additional ion exchange component. The proposed process allows for the supply of cheap Mg(2+) ions, while at the same time enables the application of the cheap H(2)SO(4)-based calcite dissolution process, thus resulting in higher quality water at a cost-effective price. A case study is presented in which additional cost of supplying a Mg(2+) concentration of 12mg/L using the process is estimated at $0.004/m(3) product water.     

变电站土壤腐蚀性评价及接地网金属腐蚀特性分析

变电站土壤的腐蚀性与接地网金属服役寿命密切相关。分析了某变电站接地网11个典型部位土壤样品的电阻率、氧化还原电位、含水量、含盐量、pH值、Cl-、SO42-、HCO3-、Na+、Ca2+、Mg2+等理化指标,根据相关标准分析、评估该变电站土壤腐蚀性;同时用扫描电镜(SEM)、能谱(EDAX)分析了该变电站接地网金属样品腐蚀特性,认为:土壤的腐蚀性决定于土壤电阻率、氧化还原电位及Cl-、SO42-含量,许多情况下,Cl-与SO42-对接地网金属腐蚀起到促进作用。并提出了防腐方法。     

Major nutrients and acidity: budgets and trends at four remote boreal stands in Finland during the 1990s

Major nutrients and acidity were studied at six plots in four Integrated Monitoring catchments in Finland, located along a south-north deposition gradient. The quality and quantity of bulk precipitation, throughfall, soil water, and litterfall were monitored during the period 1989-1997. The results showed a marked decline in SO4 and H+ concentrations overall. Trends in throughfall ANC values were positive, while those in soil water were mostly negative. The increase in throughfall ANC values indicates recovery from acid deposition. The adsorption of base cations and release of organic acids was implicated in the decrease in soil water ANC trends. For all variables, the changes tended to be the greatest in the most southerly catchment, which received the most deposition loads. Mass balance budgets showed that total deposition inputs were greater than soil leaching outputs (at 40 cm) for NO3, NH4 and SO4, and were attributed to nutrient uptake and cycling processes. In contrast, for Ca, Mg, K and Na, and S (Valkea-Kotinen3 and Vuoskoj?rvi2 plots only), inputs were less than outputs, indicating net leaching. Throughfall + litterfall inputs to the forest floor showed that the organic layer is particularly important in the retention of Ca, Mg and N. Sulfur was retained in the lower soil layers, and attributed to Al and Fe hydroxide adsorption in the B horizon.     

Natural denitrification in the Kakamigahara groundwater basin,Gifu prefecture,central Japan

Although nitrate is recognized as the most common groundwater contaminant due to growing anthropogenic sources, such as agriculture in particular, its adverse effects on human and animal health are debatable. The current issue, however, is to control and reduce nitrate contamination with regards to the long residence time of groundwater within aquifers. Denitrification has recently been recognized for its ability to reduce high nitrate concentrations in groundwater. The Kakamigahara groundwater basin, Gifu prefecture, Japan, witnessed rising levels of nitrate (>12 mg/l NO(3)-N) originating from agricultural sources. Chemical analyses for the determination of major constituents of groundwater and delta(15)N of residual nitrate were performed on representative groundwater samples in order to fulfill two main objectives. One is to investigate the current situation of nitrate groundwater pollution. The second objective is to determine whether the denitrification is a potential natural mechanism, which eliminates nitrate pollution in the Kakamigahara aquifer. Agricultural nitrate contamination of groundwater was obvious from characteristically high concentrations of Ca(2+), Mg(2+), NO(3)(-) and SO(4)(2-). High nitrate concentrations were found on the eastern side of the basin in association with vegetable cultivation fields, and decreased gradually towards the west of the basin along the direction of groundwater flow. The decrease of nitrate concentration was conveniently coupled with increase of HCO(3)(-) (the heterotrophic denitrification product), pH and delta(15)N of residual nitrate (due to isotopic fractionation) from east to west. Therefore, denitrification in situ is continuously removing nitrate from the Kakamigahara groundwater system.     

Comparative PM10-PM2.5 source contribution study at rural, urban and industrial sites during PM episodes in Eastern Spain

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 sources were mineral dust (mainly Al2O3, Fe, Ti, Sr, CaCO3, Mg, Mn and K), emissions derived from power generation (SO4=, V, Zn and Ni), vehicle exhausts (organic and elemental carbon, NO3- and trace elements) and marine aerosol (Na, Cl and Mg). The latter was not identified in PM2.5. At the industrial site, additional PM10 sources were identified (tile covering in the ceramic production, petrochemical emissions and bio-mass burning from a large orange tree cultivation area). The contribution of each PM source to PM10 and PM2.5 levels experiences significant variations depending on the type of PM episode (Local-urban mainly in autumn-winter, regional mainly in summer, African or Atlantic episode), which are discussed in this study. The results show that it would be very difficult to meet the EU limit values for PM10 established for 2010. The annual mean PM levels are 22.0 microg PM10/m3 at the rural and 49.5 microg PM10/m3 and 33.9 microg PM2.5/m3 at the urban site. The natural contribution in this region, estimated at 6 microg/m3 of natural mineral dust (resulting from the African events and natural resuspension) and 2 microg/m3 of marine aerosol, accounts for 40% of the 2010 EU annual limit value (20 microg PM10/m3). Mineral dust concentrations at the urban and industrial sites are higher than those at the rural site because of the urban road dust and the ceramic-production contributions, respectively. At the urban site, the vehicle exhaust contribution (17 microg/m3) alone is very close to the 2010 EU PM10 limit value. At the rural site, the African dust is the main contributor to PM10 levels during the highest daily mean PM10 events (100th-97th percentile range). At the urban site, the vehicle exhaust product is the main contributor to PM10 and PM2.5 levels during the highest daily mean PM events (100th-85th percentile range). Mineral dust concentrations during African dust events accounts for 20-30 microg/m3 in PM10 and 10-15 microg/m3 in PM2.5. During non-African dust events, mineral dust derived from anthropogenic activities (e.g. urban road dust) is also a significant contributor to PM10, but not to PM2.5.     

Drinking water quality in the Ethiopian section of the East African Rift Valley I--data and health aspects

Drinking water samples were collected throughout the Ethiopian part of the Rift Valley, separated into water drawn from deep wells (deeper than 60 m), shallow wells (<60 m deep), hot springs (T>36 degrees C), springs (T<32 degrees C) and rivers. A total of 138 samples were analysed for 70 parameters (Ag, Al, As, B, Ba, Be, Bi, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Dy, Er, Eu, F, Fe, Ga, Gd, Ge, Hf, Hg, Ho, I, In, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Nd, Ni, NO(2), NO(3), Pb, Pr, Rb, Sb, Se, Si, Sm, Sn, SO(4), Sr, Ta, Tb, Te, Th, Ti, Tl, Tm, U, V, W, Y, Yb, Zn, Zr, temperature, pH, conductivity and alkalinity) with ion chromatography (anions), spectrometry (ICP-OES and ICP-MS, cations) and parameter-specific (e.g. titration) techniques. In terms of European water directives and WHO guidelines, 86% of all wells yield water that fails to pass the quality standards set for drinking water. The most problematic element is fluoride (F), for which 33% of all samples returned values above 1.5 mg/l and up to 11.6 mg/l. The incidence of dental and skeletal fluorosis is well documented in the Rift Valley. Another problematic element may be uranium (U)-47% of all wells yield water with concentrations above the newly suggested WHO maximum acceptable concentration (MAC) of 2 microg/l. Fortunately, only 7% of the collected samples are above the 10 microg/l EU-MAC for As in drinking water.