Nitrate pollution from agriculture in different hydrogeological zones of the regional groundwater flow system in the North China Plain

A survey of the quality of groundwater across a broad area of the North China Plain, undertaken in 1998 to 2000, indicates that nitrate pollution is a serious problem affecting the drinking water for a vast population. The use of nitrogen (N)-fertilizer in agriculture has greatly increased over the past 20 years to meet the food needs of the rapidly expanding population. During the study, 295 water samples were collected from wells and springs to determine the water chemistry and the extent of nitrate pollution. High concentrations of nitrate, especially in a recharge area along the western side, but also in the vicinity of Beijing and locally in other parts of the plain, pose a serious problem for the drinking water supply. In places, the nitrate concentration exceeds the maximum for safe drinking water of 45 mg/L. The intense use of N-fertilizer and the widespread use of untreated groundwater for crop irrigation contribute greatly to the problem, but no doubt the disposal of industrial and municipal waste into streams and infiltrating the aquifer also contribute to the problem; however, the lack of data prevents evaluation of those sources. In the recharge area, nitrate is found at depths of as much as 50 m. Near Beijing, relatively high concentrations of nitrate occur at depths of as much as 80 m. In the discharge area, in the vicinity of the Yellow River, high concentrations of nitrate occur at depths of <8 m.

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Resumen Contaminacíon de nitratos a causa de prácticas agrícolas en diferentes zonas hidrogeológicas del sistema de flujo regional de aguas subterráneas en la planice del norte de China. Un estudio de la calidad del agua subterránea en una zona amplia de la planice del norte de China se llevó a cabo entre 1998 y el año 2000. Este estudio indica que la contaminación de nitratos es un problema grave que afecta el agua potable de una vasta población. El uso de fertilizantes a base de nitratos en la agricultura ha aumentado considerablemente durante los últimos 20 años para satisfacer las necesidades alimentices de la creciente población. Durante el estudio, se tomaron 295 muestras de pozos de agua y manantiales para determinar la química de las aguas y el grado de contaminación por nitratos. Altas concentraciones de nitratos, especialmente en una zona de recarga a lo largo del lado oeste, asì como en la cercanía a Pekín y en zonas locales en otras partes de la planicie, presentan un problema serio al sumunistro de agua potable. En ciertos lugares, la concentracióon de nitratos excede el nivel máximo de seguridad para el agua potable 45 mg NO₃/L. El intenso uso de fertilizantes de nitratos y el abundante uso de agua subterránea sin tratamiento para la irrigación de cultivos contribuyen sustancialmente al problema. Sin embargo, sin lugar a dudas, la descarga de deshechos industriales y municipales en arroyos y en el acuífero también contribuyen al problema. La falta de datos impide la evalución de dichas fuentes. En la zona de recarga se encuentran nitratos hasta los 50 m de profundidad. Cerca a Pekín, concentraciones relativamente altas de nitrato ocurren hasta los 80 m de profunidad. En las zonas de descarga afectadas por el Río Amarillo las concentraciones altas de nitrato se encuentran solamente a menos de 8m de profundidad.

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Resumé Une campagne dévaluation de la qualité de leau souterraine entreprise entre 1998 et 2000 à travers une vaste étendue de la plaine du nord en Chine indique que la pollution par les nitrates est un problème sérieux qui affecte la qualité de leau souterraine pour une abondante population. Lutilisation de fertilisants azotés pour lagriculture a augmenté considérablement durant les 20 dernières années afin de rencontrer les besoins alimentaires dune population à forte croissance. Lors de cette étude, 295 échantillons deau ont été prélevés dans des puits et sources naturelles afin de déterminer la composition chimique de leau souterraine ainsi que létendue de la pollution par les nitrates. Des concentrations élevées de nitrates, en particulier dans une zone de recharge le long de la limite ouest de la plaine, mais aussi dans la région de Beijing et sporadiquement dans la plaine, posent de sérieux problèmes à la consommation de leau souterraine. A certains endroits, la concentration en nitrates excède la valeur maximale acceptée pour la consommation qui est de 45 mg NO₃/L. Lutilisation intensive de fertilisants azotés ainsi que lutilisation répandue deau souterraine non traitée pour lirrigation contribuent pour beaucoup au problème, mais il ne fait pas de doute que le rejet des déchets municipaux et industriels dans les rivières et aquifères y est aussi pour quelque chose. Par contre, le manque de donnés ne permet pas dévaluer la contribution de chacune de ces sources. Dans la zone de recharge, les nitrates se retrouvent à des profondeurs allant jusquà 50 m. Près de Beijing, des concentrations relativement élevées de nitrate ont été mesurées à des profondeurs allant jusquà 80 m. Enfin, dans la zone démergence affectée par la rivière Jaune, les fortes concentrations se retrouvent à une profondeur maximale de 8 m.

     

Precise computation of acceleration due to uniform ring or disk

We describe a precise numerical method to evaluate the acceleration vector of an inverse-square force law caused by a uniform ring or disk. The method consists of two parts. One is rewriting of the analytic expressions of the vector to reduce the loss of information in its computation. The other is a procedure to compute a special linear combination of the complete elliptic integrals of the first and the second kind appeared in the rewritten expressions.     

Use of flood chronology for detailed environmental analysis: a case study of Lake Kizaki in the northern Japanese Alps,central Japan

This paper presents a study of the usefulness of flood layers as a time marker in sediments and a report of a case study of Lake Kizaki in central Japan. A flood layer can be identified as a layer having a higher density, coarser grain size, lower TN content, and higher C/N ratio than those of the upper and lower horizons. It can also be characterized by a hyperpycnal sequence composed of a basal coarsening-upward unit and a top fining-upward unit. When flood layers can be correlated with heavy rains in meteorological records, detailed age markers are well established in the sediment. Five flood layers were identified in the surface sediment of Lake Kizaki, and they could be attributed to the historical heavy rainfalls that took place on July 12, 1995; September 28, 1983; August 25, 1974; September 26, 1959; and September 1, 1949 under the constraint of an age model. A precise age model is essential to clarify the environmental changes such as the pollutant history in detail.     

Fast computation of complete elliptic integrals and Jacobian elliptic functions

As a preparation step to compute Jacobian elliptic functions efficiently, we created a fast method to calculate the complete elliptic integral of the first and second kinds, K(m) and E(m), for the standard domain of the elliptic parameter, 0 < m < 1. For the case 0 < m < 0.9, the method utilizes 10 pairs of approximate polynomials of the order of 9–19 obtained by truncating Taylor series expansions of the integrals. Otherwise, the associate integrals, K(1 − m) and E(1 − m), are first computed by a pair of the approximate polynomials and then transformed to K(m) and E(m) by means of Jacobi’s nome, q, and Legendre’s identity relation. In average, the new method runs more-than-twice faster than the existing methods including Cody’s Chebyshev polynomial approximation of Hastings type and Innes’ formulation based on q-series expansions. Next, we invented a fast procedure to compute simultaneously three Jacobian elliptic functions, sn(u|m), cn(u|m), and dn(u|m), by repeated usage of the double argument formulae starting from the Maclaurin series expansions with respect to the elliptic argument, u, after its domain is reduced to the standard range, 0 ≤ u < K(m)/4, with the help of the new method to compute K(m). The new procedure is 25–70% faster than the methods based on the Gauss transformation such as Bulirsch’s algorithm, sncndn, quoted in the Numerical Recipes even if the acceleration of computation of K(m) is not taken into account.     

Numerical computation of spherical harmonics of arbitrary degree and order by extending exponent of floating point numbers

By extending the exponent of floating point numbers with an additional integer as the power index of a large radix, we compute fully normalized associated Legendre functions (ALF) by recursion without underflow problem. The new method enables us to evaluate ALFs of extremely high degree as 2³² =  4,294,967,296, which corresponds to around 1 cm resolution on the Earth’s surface. By limiting the application of exponent extension to a few working variables in the recursion, choosing a suitable large power of 2 as the radix, and embedding the contents of the basic arithmetic procedure of floating point numbers with the exponent extension directly in the program computing the recurrence formulas, we achieve the evaluation of ALFs in the double-precision environment at the cost of around 10% increase in computational time per single ALF. This formulation realizes meaningful execution of the spherical harmonic synthesis and/or analysis of arbitrary degree and order.     

Differences in organotin accumulation in relation to life history in the white-spotted charr Salvelinus leucomaenis

To examine the accumulation pattern of organotins (OTs) in relation to the migration of diadromous fish, tributyltin (TBT) and triphenyltin (TPT) and their derivatives were determined in the muscle tissue of both sea-run (anadromous) and freshwater-resident (nonanadromous) types of the white-spotted charr Salvelinus leucomaenis. Ontogenic changes in otolith strontium (Sr) and calcium (Ca) concentrations were examined along life history transect to discriminate migration type. Mean Sr:Ca ratio from the core to the edge of the otolith in sea-run individuals was significantly higher than those in freshwater-resident one. There were no significant correlations in S. leucomaenis between OT accumulation and various biological characteristics. It is noteworthy that TBT and TPT concentrations in sea-run type were significantly higher than those in freshwater-resident individuals, although they are both of the same species. These results suggest that sea-run S. leucomaenis have a higher ecological risk of OT exposure than freshwater-residents during their life histories.     

Wide Field Imaging of Ion Tail of Comet C/Hale–Bopp

A sequential imaging observation of the ion tail of Comet C/Hale-Bopp 1995O1 was carried out in February–March 1997 with a wide-field CCD imaging camera using narrow band filters for two ion species; CO⁺ and H₂O⁺ along with those for blue and red continuum. From the surface photometry of the ion tail of two species, we derived a relationship between plasma density and distance from the nucleus. The local velocity of the ion flow as a function of the distance from the nucleus was also estimated on the basis of some assumptions. We report preliminary results of our analysis, and discuss some characteristics of cometary plasma and its interaction with interplanetary magnetic field (IMF). May the source be with you! This revised version was published online in July 2006 with corrections to the Cover Date.     

Factors controlling the acid‐neutralizing capacity of Japanese cedar forest watersheds in stands of various ages and topographic characteristics

Acid‐neutralizing capacity (ANC) is an important index for streamwater acidification caused by external factors (i.e. chronic acid deposition) and internal factors such as soil acidification due to nitrification. In this study, the influence of forest clear‐cutting and subsequent regrowth on internal acidification was investigated in central Japan, where stream pH (near 7·0) and ANC (above 0·1 meq L^?1) are high. pH, the concentrations of major cations (Na⁺, K⁺, Mg²⁺ and Ca²⁺), major anions (NO₃^?, Cl^? and SO₄^2?) and dissolved silica (Si), and ANC were measured in 33 watersheds of various stand ages, during 2002 to 2004. Only NO₃^? concentration decreased with stand age, whereas pH, ANC, and concentrations of the sum of base cations (BC) and Si were negatively correlated with the minimum elevation of the watershed. The correlation between the BC/Si ratio and minimum elevation suggested that factors contributing to acid neutralization changed at 1100 m above sea level. In watersheds at lower elevations (?1100 m), the relatively high contribution of soil water with longer soil contact times should result in higher ANC, and cation exchange reactions should be the dominant process for acid neutralization due to deposition of colluvial soils on the lower slope. In contrast, in higher‐elevation watersheds (≥1100 m), weathered residual soils are thin and the small contribution of deeper groundwater results in lower ANC. These results suggest that the local acid sensitivity is determined by the hydrological and geomorphologic factors generated by steep topography. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of long‐term water balance in the source area of the Yellow River basin

To analyse the long‐term water balance of the Yellow River basin, a new hydrological model was developed and applied to the source area of the basin. The analysis involved 41 years (1960–2000) of daily observation data from 16 meteorological stations. The model is composed of the following three sub‐models: a heat balance model, a runoff formation model and a river‐routing network model. To understand the heat and water balances more precisely, the original model was modified as follows. First, the land surface was classified into five types (bare, grassland, forest, irrigation area and water surface) using a high‐resolution land‐use map. Potential evaporation was then calculated using land‐surface temperatures estimated by the heat balance model. The maximum evapotranspiration of each land surface was calculated from potential evaporation using functions of the leaf area index (LAI). Finally, actual evapotranspiration was estimated by regulating the maximum evapotranspiration using functions of soil moisture content. The river discharge estimated by the model agreed well with the observed data in most years. However, relatively large errors, which may have been caused by the overestimation of surface flow, appeared in some summer periods. The rapid decrease of river discharge in recent years in the source area of the Yellow River basin depended primarily on the decrease in precipitation. Furthermore, the results suggested that the long‐term water balance in the source area of the Yellow River basin is influenced by land‐use changes. Copyright © 2007 John Wiley & Sons, Ltd.