Environmental Impacts of Acid Leachate Derived from Coal-Storage Piles upon Groundwater

Leachate emanating from a coal-storage area at an electricutility plant in Northwest Indiana (U.S.A.) is impacting groundwater quality. This assessment is based on results of along-term groundwater monitoring program conducted at Purdue University's Wade Utility Plant where a monthly average of 32,000metric tons of both high- and low-sulfur coal are stored. Groundwater from both a perched and major aquifer (the WabashValley Aquifer) as well as surface water from a large retentionpond were sampled monthly for 34 consecutive months. Such a long-term, continuous sampling scheme proved beneficial in identifying seasonal trends and anomalies within the chemistryof ground- and surface waters. Data show elevated concentrationsof sulfate and hardness in the perched zones and the WabashValley Aquifer (WVA). Lead in the WVA has also been reported ata concentration greater than the state maximum contaminant level, while several metals (Be, Cd, Cu, Pb, Ni, Se, and Zn) containedwithin retention-pond sediments have the highest concentrationsin aquatic sediments ever reported within the State of Indiana.Due to the buffering capacity of carbonate minerals in underlyingunconsolidated deposits, the acidic pH of coal-pile leachate is raised to values typical for groundwater in carbonate terrain common in Northwest Indiana. Further ameliorating the input of acid percolation is the dilution capabilities of both the WVA and the recharge pond. Hence, sites without such advantages would exhibit a greater degree of groundwater contamination than what is observed at Purdue's coal-storage facility.     

The behaviour of nitrogen fertilizers in neutral and acid loess soils II. Distribution and balances of 15 N-tagged nitrogen

A study, to investigate the remaining fertilizer-N in undisturbed soil columns from agricultural and forest soils after 60 days of percolation (see part I), was carried out. The columns were fertilized with two 15-N tagged nitrogen fertilizers (Ca(NO₃)₂ and (NH₄)₂SO₄) at a rate of 80kg N/ha. The investigation involved the distribution and fractionation of nitrogen in the soils. The soil columns were therefore cut into 8 segments and nitrogen forms analyzed were: total N, fixed-NH₄-N, exchangeable NH₄-N, NO₃-N and organic N. Consequently, the N-balances were established. It was ascertained that immobilization and gaseous losses from the fertilizers were higher after NH₄- than after NO₃-application in both soils. Immobilization in all treatments was temperature dependent and concentrated at the upper segments of the columns. The forest soil had higher incorporation than the agricultural soil. Nitrification was low in the forest soil while in the agricultural soil there was a fairly high nitrification even at 4°C. The balances showed losses of nitrogen in the range of 10 to 35 %. While this agrees with the findings of other workers in case of the agricultural soil, it leaves however, some questions unanswered in case of the forest soil.     

Pattern of microbial indicators in forest soils along an European transect

Microbial biomass C and activity were determined in six forest soils along a gradient in physical and chemical climate in Europe. Both parameters were measured microcalorimetrically. The upper 22 cm of the soils were sampled in undisturbed columns (24 cm deep). Measurements were made in homogenized samples of the different surface organic horizons (Ol, Of, Oh) and the mineral horizons (Ah, Aeh, Bv) down to 22 cm.On a mass basis values for both the biomass and the activity showed an exponential decrease with depth in all soils. Expressed on a volume basis these relationships varied with soil pH. in the strongly acidified soils most of the microbial biomass and activity was located in the forest floor. In less acidified soils both parameters were highest in the mineral soil.Further relationships between biomass and activity and between soil chemical properties showed significant positive correlations with exchangeable Ca²⁺, Mg²⁺, Ca/Al and negative correlations with Al³⁺. There were no significant correlations with exchangeable cations in less acidified soils. It was calculated that the microbial biomass is more affected by soil chemistry than activity. The caloric quotient (qW) is a good parameter for determining the ecophysiological state of microorganisms in acidified soils.     

Bodenhydrologische Methoden zur Untersuchung ungestörter,skelettreicher Böden

Soil hydrological methods for investigations on undisturbed samples of skeleton-rich soils New methods are proposed, which allow the determination of moisture transmission properties of stony soils. A soil sampling technique is discussed whereby small monoliths are isolated from the surrounding soil and covered with polyester-soaked glassfiber sheets. With use of such irregularly shaped columns the soil moisture characteristic and the unsaturated hydraulic conductivity are determined by laboratory procedures. Starting with a saturated column, suction is applied and the resulting outflow is measured. At the same time the suction in the sample is registered and also the hydraulic gradient within the sample is determined. Also discussed is a procedure to install tensiometers in stony soils. The installation provides reliable data and the maintenance is easy. By building in a heating system in the tensiometers, these can be operated all year round.     

Simultane Bestimmung von N-Transformationsraten in Bodensäulen unter Verwendung von 15-N: Stickstoffmodell für eine Terra fusca-Rendzina

Simultaneous determination of nitrogen transformation rates in soil columns using 15-N: N-Model of a Terra fusca-Rendzina soil Rates of ammonification, nitrification, immobilization, and denitrification were determined in undisturbed columns of a Terra fusca Rendzina soil. A steady input of 15-N labelled ammoniumsulfate with the irrigation water created a steady state of the turnover processes in the soil resulting in a constant output of 15-N-nitrate. In this state the rate constants (8°C) were K₁ = 0.64 for the netto-N-nitrification, K₂ = 0.11 for the netto-N-denitrification, and K₃ = 0.25 for the netto-N-immobilization. 64% of the nitrate was leached, 25% immobilized in organic matter, and 11% denitrified. Relating these rate constants to the turnover of the soil nitrogen one can calculate the mean annual rates for the different processes of a forest soil, using the mean annual temperature. For the Göttinger Wald situation (T = 6.9°C) the following rates were calculated; Ammonification = 183 kg N·ha^?1·a^?1, immobilization = 44 kg N·ha^?1·a^?1, netto N-denitrification = 19 kg N·ha^?1·a^?1, and netto-N-mineralization = 120 kg N·ha^?1·a^?1.     

Microbial community structure and activity in agricultural soils under different management

For the development of management strategies in sustainable agriculture it is necessary to describe and predict the role of soil microbes in different management systems. The classical approach uses the microbial biomass as the key parameter for the entire system, but for ecological purposes the variability of biotic parameters in time and space has to be better described. Moreover, the biomass active in the total soil profile or its most active zones should be used as a basis for the assessment of soil activity. The sum of adenylates was found to be more closely related to the microbial biomass than was ATP, which however appeared to be a better indicator for the microbial activity. Fatty acids from phospholipids were highly correlated with the soil microbial biomass. The pattern of fatty acids from soils under different long-term management indicated a high potential to typify the microbial community in soils and special organism populations. To overcome the problem, that only a small portion of the soil inhabiting microbes can be cultivated, first steps to use serological and genetical methods to directly identify or localize specific populations in the rhizosphere are shown.     

Dynamics of maize (Zea mays L.) leaf straw mineralization as affected by the presence of soil and the availability of nitrogen

An incubation experiment was carried out with maize (Zea mays L.) leaf straw to analyze the effects of mixing the residues with soil and N amendment on the decomposition process. In order to distinguish between soil effects and nitrogen effects for both the phyllospheric microorganisms already present on the surface of maize straw and soil microorganisms the N amendment was applied in two different placements: directly to the straw or to the soil. The experiment was performed in dynamic, automated microcosms for 22 days at 15 °C with 7 treatments: (1) untreated soil, (2) non-amended maize leaf straw without soil, (3) N amended maize leaf straw without soil, (4) soil mixed with maize leaf straw, (5) N amended soil, (6) N amended soil mixed with maize leaf straw, and (7) soil mixed with N amended maize leaf straw. ¹⁵NH₄¹⁵NO₃ (5 at%) was added. Gas emissions (CO₂, ¹³CO₂ and N₂O) were continuously recorded throughout the experiment. Microbial biomass C, biomass N, ergosterol, δ¹³C of soil organic C and of microbial biomass C as well as ¹⁵N in soil total N, mineral N and microbial biomass N were determined in soil samples at the end of the incubation. The CO₂ evolution rate showed a lag-phase of two days in the non-amended maize leaf straw treatment without soil, which was completely eliminated when mineral N was added. The addition of N generally increased the CO₂ evolution rate during the initial stages of maize leaf straw decomposition, but not the cumulative CO₂ production. The presence of soil caused roughly a 50% increase in cumulative CO₂ production within 22 days in the maize straw treatments due to a slower decrease of CO₂ evolution after the initial activity peak. Since there are no limitations of water or N, we suggest that soil provides a microbial community ensuring an effective succession of straw decomposing microorganisms. In the treatments where maize and soil was mixed, 75% of microbial biomass C was derived from maize. We concluded that this high contribution of maize using microbiota indicates a strong influence of organisms of phyllospheric origin to the microbial community in the soil after plant residues enter the soil.     

The behaviour of Nitrogen fertilizers in neutral and acid loess soils I. Transport and transformations of nitrogen

A study to investigate the transport and the transformation of two N¹⁵-tagged N-fertilizers (Ca(NO₃₎₂ and (NH₄₎₂SO₄) was carried out in the laboratory at 4° and 23°C. Undisturbed soil columns from the upper 30 cm of neutral agricultural and acid forest loess soils were used. An unsaturated steady state water flow in the columns was established and maintained by a darcian flow of 5mm of water/day. The effluent collected from each column after two days, was analysed for NO₃- and NH₄+. The data collected were used to obtain the Breakthrough Curves (BTCs). The BTCs after NO_3- fertilizers from agricultural soil approached the ideal symmetrical curves from non-reacting solutes. While those from acid forest soil were somewhat flat and ended with pronounced tails. -Transformation of the applied NH_4- fertilizer to NO_3-N was much higher in agricultural soil than in acid forest soil. Even at lower temperature, nitrification in agricultural soil was active though at a reduced rate while in forest soil, nitrification rate was extremely low and appeared to be independent of temperature.