Losses of nitrogen,phosphorus and potassium from agricultural watersheds of minor rivers in the Oka Valley

The losses of nitrogen (NH₄, NO₃, N_org), phosphorus (P_ortho, P_poly, P_org) and potassium (K⁺) from watershed areas of minor rivers, draining regions of different agricultural land use in the Oka Valley, U.S.S.R., were investigated. No N, P, and K pollution was shown in these watersheds, even though the rate of losses was found to be highly correlated with the amounts of mineral fertilizers and FYM applied. The losses were also determined by the natural soil fertility, erosion processes and soil texture under the similar level of fertilization.     

Calculation and Mapping of Sulfur Critical Loads for Terrestrial Ecosystems of Thailand

The essential parameters needed for the calculation of critical load of sulfur, CL(S), are base cation weathering rate, base cation uptake, acid neutralizing capacity leaching and base cation deposition. These parameters are estimated and mapped for the most area of terrestrial ecosystems of Thailand using data of national data soil survey. The values of CL(S) range from <200 to 2,225 eq.ha^?1yr^?1 and about 70% of terrestrial ecosystems are characterized by low values (<200 eq.ha^?yr^?1). These CL values reflect the sensitivity of Thai ecosystems to sulfur deposition.     

Input of atmospheric precipitation nitrogen to the Baltic sea from its catchment

Input of atmospheric precipitation nitrogen (N) to the Baltic sea aquatorium from its drainage basin has been estimated. The deposition of nitrogen compounds on the catchment has been shown to be 5 times higher than their enter directly into the sea. An assessment of this input has been carried out by two methods (direct and indirect) and the results of calculations showed relatively high similarity. It has been demonstrated that the main source of data uncertainty is related to the values of nitrogen runoff and retention in different landuse types. Depending on the subregions the values of atmospheric nitrogen deposition runoff to the Baltic sea changed from 5 up to 16%, the minimum values were obtained for northern subregions and the maximum — for south-western ones. For the whole basin of the Baltic Sea during the 1987–1991 period these runoff values were 8–10% from the total amount of atmospheric nitrogen deposition input (1341–1401 kt) at catchment. The mean value was 122 kt in 1990 yr or 14% of total nitrogen input into the Baltic Sea from all sources. The given values must undoubtedly be taken into account in various scenarios of Transboundary Air Abatement Strategy.     

Ecological Risk Assessment of Riverine Contamination in the Caspian Sea Basin: A Conceptual Model for Persistent Organochlorinated Compounds

A conceptual model of the ecological risk assessment for persistent organochlorinated compounds (POCs), like DDT, HCH, and PCBs, which contaminate reservoirs and river waters entering into the Caspian Sea is presented. The model can be used to evaluate the toxicity of POCs in these environments. Examples of this model application using POCs monitoring data for water and bottom sediments of different reservoirs and rivers of the Caspian Sea basin are presented.     

Study of landscape-agrogeochemical balance of nutrients in agricultural regions: Part III. Nitrogen

On the basis of the analysis of lands cape-agrogeochemical balance of N carried out in watersheds of four small rivers the input values were shown to be considerably higher than output values during the 10-yr period. This was due to an increase in mineral fertilizer application with no commensurate rise in the export of agricultural production from the regions.     

Behaviour of 2,4-D Herbicide in Coastal Area of Oka River,Russia

Laboratory and field experiments werecarried out with 2,4-D herbicide(2,4-Dichlorophenoxyacetic acid) to evaluate itstransformation and migration in the coastal waterprotection zones of the Oka river, Russia. In thefirst laboratory experiment, the transformation of2,4-D was studied in various soil samples from coastalslopes (1–0°) of 480 m length soil-geochemicalcatena on the right side of the Oka river incomparison with watershed and floodplain soils. Thetransformation of 2,4-D was the lowest in soil sampleswith minimal pH values and was independent of eitherslope values or vicinity to the Oka river channel.Using indirect estimates, the surface runoff potentialwas calculated for this herbicide. In the second fieldexperiment, the vertical migration and transformationof 2,4-D was carried out in soddy sand soil (EutricArenosol) placed in the left side of the Oka river(0-100 cm) under `soft' (40 mm 2 hr<sup>-1</sup>) and `hard'(40 mm 15 min^-1) irrigation regimes. Furthermore, thetransformation of this herbicide was studied in 0–20and 40–50 cm soil layers under various temperature andmoisture regimes. After 1 day of irrigation, the mainherbicide quantity was found in the 0–30 cm layerunder both irrigation regimes. The transformation ofthe herbicide was faster in the surface, 0–20 cmlayer, than in the deeper, 40–50 cm layer.     

Sulfur Acidity Loading in South Korean Ecosystems

The applicability of critical load (CL) methodology for thedetermination of natural terrestrial ecosystem sensitivity to sulfur acidity loading in South Korea was investigated.The sulfur critical load values, CL_maxS, were calculated for the terrestrial ecosystems of South Korea using the steady-state mass balance approach. The corresponding mapping of CL_maxS was carried out on the scale of 11 × 14 km grid cells. The estimated CL_maxS values depend on the low rate of soil chemical base cation weathering (mainly, 200–400 eq ha^-1 yr^-1), relativelylow base cation depositions (mainly less than 450 eq ha^-1 yr^-1) and base cation uptake (predominantly 300–400 eq ha^-1 yr^-1), and in significant degree on high valuesof acid neutralizing capacity. The latter in turn is connectedwith relatively high values of surface runoff (maximum 9000 m³ ha^-1 yr^-1). It has been shown that about 75%of CL_maxS values are in the range of 1000–2000 eq ha^-1 yr^-1 and about 15% are relatively low values(<1000 eq ha^-1 yr^-1). About 10% of ecosystems haveCL values more than 2000 eq ha^-1 yr^-1. The sensitiveand very sensitive ecosystems occur in the southeastern part of the country whereas the sustainable ecosystems are wide spread in the northeastern part. In accordance with sulfur critical load and sulfur deposition patterns, in 1994–1997 the CL_maxS values were found to be exceeded in about 40% of total number of Korean ecosystems, mainly in the southeastern part of the country. The average yearly valuesof exceedances varied from 176 to 3100 eq ha^-1 yr^-1.     

Uncertainty analysis of critical loads for terrestrial ecosystems in Russia

The goal of this study is to give a comprehensive and quantitative estimation of the uncertainty of computed in different scale nitrogen (N) and sulphur (S) critical loads (CL) values for terrestrial ecosystems of the Northern Asia, European part and the North-Western regions of Russia. The CL values are used to set goals for future deposition rates of acidifying compounds so that the environment is protected. In this research CL values for terrestrial ecosystems are determined using the expert-modelling geoinformation system (EM GIS) approach. UNCSAM software package is used as the tool for uncertainty analysis. The analysis presented here focuses on the estimation and effect of the input source uncertainties and sensitivities on the CL values in various regions under study. In spite of the region, nitrogen uptake by vegetation, nitrogen leaching from terrestrial ecosystems and the difference between deposition and uptake by plants of base cations (BC) are the most influential factors for all terrestrial ecosystems of Russia.     

Comparison of Heavy Metal Adsorptions by Thai Kaolin and Ballclay

The adsorption characteristics of heavy metals: cadmium(II), chromium(III), copper(II), nickel(II), lead(II), and zinc(II) ions by kaolin (kaolinite) and ballclay (illite) from Thailand were studied. This research was focussed on the pH, adsorption isotherms of single-metal solutions at 30–60 °C by batch experiments, and on ion selectivityin mixed and binary combination solutions. It was found that, except Ni, metal adsorption increased with increased pH of the solutions and their adsorption followed both Langmuir and Freundlich isotherms. Adsorption of metals in the mixture solutions by kaolin was: Cr > Zn > Cu ≈ Cd ≈ Ni > Pb, and for ballclay was: Cr > Zn > Cu > Cd ≈ Pb > Ni. The adsorption of metals was endothermic, with the exception of Cd, Pb and Zn for kaolin, Cu and Zn for ballclay. Kaolin and ballclay exhibited relatively hard Lewis base adsorption site. The presence of other metals may reduce or promote the adsorption of heavy metals. The presence of Cr³⁺ induced the greatest reduction of metal adsorptiononto kaolin, as did the presence of Cu²⁺ for ballclay.     

Nitrogen balance in small river basins under agricultural and forestry use

The N balance has been studied in detail in the basins of small rivers under agricultural management and forest use. The N content of the watershed territory of large forests was found to be practically balanced. In the river basin where the land was intensively farmed for 10 yr, N input increased five times through mineral fertilizers, and one-and-a-half times through organic fertilizers. Consequently, the amount of N returned to the atmosphere as a result of denitrification increased by one-and-a-half times, and that leached into the ground water, increased from 0.8 to 6.5 mg 1^?1 N.