Extent Of Leaching Research Articles

Leaching of Diethylhexyl Phthalate from Polyvinyl Chloride Containers by Selected Drugs and Formulation Components

The extent of leaching of diethylhexyl phthalate (DEHP) from polyvinyl chloride (PVC) bags by several organic solvents and surfactants used as formulation components and by 12 drug products containing these solvents and surfactants was studied. The organic solvents ethanol, polyethylene glycol, and propylene glycol, the surfactants polysorbate 80 and polyoxyethylated castor oil, and the 12 drugs were admixed separately in PVC bags of 5% dextrose injection. At the time of preparation and after 4, 8, and 24 hours at 24 degrees C, the concentration of DEHP in duplicate samples was determined in duplicate by high-performance liquid chromatography. Ethanol, polyethylene glycol, and propylene glycol at concentrations of 25% and the drugs containing these components did not leach DEHP within the study period. Polysorbate 80 1% to 25% leached detectable amounts of DEHP in as little as one hour at the high concentration and within four hours at the lower concentrations; at 24 hours, DEHP concentrations ranged from 36 micrograms/mL for 1% polysorbate 80 to 237 micrograms/mL for 25% polysorbate 80. Similar results were observed for polysorbate 80 plus ethanol and for polyoxyethylated castor oil plus ethanol. Drug products containing surfactants, including cyclosporine, miconazole, and teniposide, and the vehicles used in formulating taxol and taxotere, leached relatively large amounts of DEHP in 24 hours. Smaller amounts were leached by chlordiazepoxide hydrochloride and etoposide. DEHP was leached from PVC containers by a variety of surfactants and drug products containing these surfactants. Drugs that leach DEHP should be prepared in non-PVC containers and administered through non-PVC tubing.

The leachability of elements in solid wastes

Landfills and waste disposal sites are now routinely used for disposal of solid wastes and their incinerator ashes. Trace elements from these ashes are leached by rain and acid rain into nearby waterways providing a pathway for toxic elements to re-enter the food chain and the human life cycle. This paper examines the mechanism and the extent of leaching of 20 elements viz. Ag, Al, As, Ba, Br, Ca, Cd, Co, Cr, Fe, Hg, La, Sb, Sc, Ce, Sm, Ta, V, W and Zn. Instrumental neutron activation analysis (INAA) was used for the assay. The solid wastes studied are municipal refuse incinerator ash, coal fly ash, hospital incinerator ash, raw sewage sludge and its incinerator ash.

Recharge mechanisms and geochemical processes in a semi-arid sedimentary basin, Eastern Cape, South Africa

Stable isotope ( 18O and 2H) and geochemical signatures are used to gain some insight into recharge processes and groundwater salinization mechanisms in a semi-arid rangeland catchment. The 665 km 2 catchment is underlain by fractured lower Beaufort sandstones and mudstones and is intruded by several dolerite dykes. Chloride and isotopic relationships suggest that chloride ions in ground water are of meteoric origin. The hypothesized recharge and salinization mechanism is that large storm events periodically dissolve accumulated surficial meteoric salts and, after a period of evaporative enrichment at or near the soil surface, leach them into the ground water. Geochemical variations imply that spatial differences exist in recharge volumes, in evaporative enrichment or in the extent of leaching of surficial salts. Meteoric sodium chloride contributes greater than 90% of the dissolved sodium, except at low salinities, where cation exchange processes yield additional sodium inputs in exchange for dissolved calcium and magnesium. At high salinities this process reverses and sodium is adsorbed, releasing calcium and magnesium. This process accounts for up to 40% of the dissolved calcium and magnesium. Contributions from geochemical weathering are relatively uniform in spite of highly variable salinities, which implies that residence times are also relatively uniform.

Lead contamination during domestic preparation and cooking of potatoes and leaching of bone-derived lead on roasting, marinading and boiling beef.

Lead concentrations were measured in boiled, mashed potatoes and in baked potatoes that had been prepared and cooked in domestic kitchens. Levels of lead in the boiled, mashed potatoes ranged from below the 1 microgram/kg limit of detection up to 18 micrograms/kg with a mean of 6 micrograms/kg (wet weight). In the large majority of cases the lead in the tap water was the predominant source of the metal. Higher amounts of lead (range 11 micrograms/kg to 56 micrograms/kg, mean 27 micrograms/kg) were present in baked potatoes and this was attributed to soil adhering to the potato skin. The extent of leaching of lead from bone during cooking has also been investigated. For beef stocks there was little evidence to suggest that significant migration of bone lead occurred. For beef casseroles, marinaded in red wine, some leaching did occur from beef joints containing elevated amounts of bone lead; however the levels were all below 350 micrograms/kg and, on average, less than double that found in casseroles prepared from normal joints where the bone lead levels were an order of magnitude less.

Stability, compatibility, and plasticizer extraction of taxol (NSC-125973) injection diluted in infusion solutions and stored in various containers

The stability of taxol (NSC-125973) in various diluents and containers was determined, and the extent of leaching of di(2-ethylhexyl) phthalate (DEHP) from polyvinyl chloride (PVC) bags caused by the taxol formulation was measured. A taxol formulation consisting of a 6-mg/mL solution of taxol in 50% polyoxyethylated castor oil and 50% dehydrated ethanol was added to 50- and 100-mL glass bottles, PVC infusion bags, and polyolefin containers containing 5% dextrose injection or 0.9% sodium chloride injection to give initial nominal taxol concentrations of 0.3, 0.6, 0.9, and 1.2 mg/mL. The containers were maintained at 20-23 degrees C for 12-24 hours. Samples were assayed by stability-indicating high-performance liquid chromatography, and clarity was determined visually. An experiment was run to ascertain whether DEHP would leach from a PVC administration set during a simulated infusion. There was no substantial loss of taxol over 24 hours. Filtration through a membrane resulted in no loss of taxol. All the solutions initially appeared hazy. Solutions stored in PVC bags became more hazy with time than solutions stored in glass or polyolefin containers. The haze seen in PVC bags was traced to leaching of DEHP. Agitation had no effect on the extent of leaching. Leaching was also seen during simulated delivery through PVC administration sets. No DEHP was detected when solutions were stored in glass or polyolefin containers and infused through polyethylene-lined sets. At the dilutions studied, taxol was visually and chemically stable for up to 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective and non-selective bioleaching of manganese from a manganese-containing silver ore

Batch culture experiments showed that manganese could be leached from a manganese-containing silver ore by bacterial strain SSW 22, by a mixed culture derived from unsterilized ore, and by a Penicillium strain isolated from the mixed culture. The extent of leaching was influenced by the kinds of electrolytes and their concentration in the culture medium. The Penicillium strain was the most active. It leached manganese by a nonenzymatic mechanism. Leaching studies with Penicillium in a stirred reactor showed that at low chloride concentration (equivalent to 0.06% NaCl) manganese was leached selectively from the ore, whereas at high chloride concentration (equivalent to 3% NaCl or synthetic seawater) both manganese and silver were readily leached from the ore. Reactor leaching of ore showed the greatest promise for possible commercial exploitation.

Effects of water acidification on the decomposition of Juncus bulbosus L.

Several field and laboratory experiments were performed to study the impact of acidification on the decomposition of Juncus bulbosus L. The breakdown of coarse detritus of this aquatic macrophyte appeared to be very slow. After 7 weeks of incubation in an acidified and a circumneutral moorland pool the remaining fraction of Juncus leaves varied between 46 and 75% of the original organic weight. Differences in decay patterns were observed among both systems. Furthermore, the breakdown rates were highly dependent on the season. Highest weight loss rates were recorded at high pH during the summer period. In acidified water and during the winter period the breakdown rates were reduced. Nutrient dynamics of detritus in the circumneutral soft water and the acidified system differed remarkably. In litter bags laid down on the bottom surface of the acidified moorland pool the density and diversity of macroinvertebrate assemblages was generally lower than in the bags immersed in the non-acidified body of water. In particular, the abundance of detritivores and herbivores at low pH was strongly reduced. However, in winter qualitative and quantitative differences in the macrofauna in the litter bags did not significantly affect decay rates of detritus. Laboratory studies revealed that the pH, bicarbonate concentration and aluminium content of the water particularly influenced the rate of decomposition of the pre-dried Juncus material. The extent of leaching and autolysis and the relative importance of fungi and bacteria in the decomposition of fresh Juncus leaves were studied using antifungal and antibacterial agents. In the laboratory leaching and autolysis accounted for 28–32% of the organic weight loss of coarse detritus. Leaching and autolysis caused the highest weight loss in the strongly acid medium. After 37 days of incubation in control media with pH 3.5 and 5.6 total organic weight loss was 55 and 59%, respectively. At pH 3.5 and 5.6 microbial decomposition accounted for organic weight losses of 23 and 31%, respectively. At low pH microbial decomposition was dominated by fungi, whereas, at pH 5.6 both fungi and bacteria played an important role in the breakdown processes. The contribution of macroinvertebrates to the breakdown of Juncus detritus seemed to be of minor importance.

Phosphorus leaching in sandy soils .I. Short-term effects of fertilizer applications and environmental conditions

The consequences of previous as well as current environmental conditions and management practices on the potential for phosphorus (P) to be lost by drainage from sandy soils in the short term (< 1 year) were studied in the laboratory and the field. The potential for P losses by drainage was estimated by measuring soil solution P levels and rapidly released P. Rapidly released P was measured by determining the concentration of dissolved inorganic P contained in filtered (<0.45 pm) soil solutions after incubating soil at saturation for 15 min at ambient temperature. In the laboratory, sandy soils were incubated with ordinary superphosphate, coastal superphosphate (a granulated mixture of equal parts of superphospate, rock phosphate and elemental sulfur) or lime-superphosphate (a lime-reverted superphosphate with 18% kiln dust) and sequentially desorbed with deionized water. The effects of the extent of leaching, fertilizer type, application rate and the time of contact with the soil on soil solution P levels were investigated. The influence of annual pasture death and summer rainfall on rapidly released P in soils that had been pre-treated by leaching were also investigated. Phosphorus concentrations decreased logarithmically in the successive supernatants of the sequentially desorbed soils. More P was desorbed from soils incubated with superphosphate and lime-superphosphate than soil incubated with coastal superphosphate. At each level of pre-leaching, the P concentrations in the soil solution increased with increasing time. The level, to which the P concentration in the soil solution increased at each time, decreased with increased extent of pre-leaching. The addition of P fertilizers increased the concentration of P in the soil solution. The concentrations increased with increasing application rate and were much higher for superphosphate than for coastal superphosphate; however, there was little effect of contact time on soil solution P levels. Rapidly released P levels after leaching increased during a period of no further leaching. Additional moisture or plant material during this period of no further leaching increased the rate and extent to which rapidly released P increased. Monitoring of rapidly released P in the 0-2, 2-5, 5-10 and 10-20 cm layers of field plots, with and without applications of superphosphate, showed that sampling depth, water flow path, fertilizer management, rainfall pattern and background P levels would affect the estimate of short-term P losses. Rapidly released P in the 0-2 cm layer varied markedly with time and was higher (P < 0.05) than that in lower soil layers. Rapidly released P increased after the winter and spring rains diminished and then decreased after the rains commenced again at the end of the summer. A possible annual cycle of P in sandy soils in a mediterranean climate is postulated by considering the laboratory and field data in combination.

Mass transfer and problems of secondary porosity creation in deeply buried hydrocarbon reservoirs

Secondary porosity created by the post-depositional leaching of detrital grains and cements can be of great economic importance. The term secondary porosity is only descriptive and does not give any information on whether the porosity of the rock has been enhanced. In reality, there are two end member volumetric outcomes to the leaching process. Firstly, the mineral can be completely dissolved and its components transported out of the system. In such an instance the porosity of the rock will be enhanced. Secondly, it is possible that a mineral will decompose and by-product minerals will be precipitated which will occupy approximately the same volume as the original mineral. The latter case is more likely where the pore waters are close to equilibrium with the majority of the minerals of the rock. This will occur at elevated temperatures and/or where the pore waters have been in contact with the rock for a long time. These conditions are commonly met during intermediate to deep burial. Many metastable minerals such as high temperature feldspars, probably decompose in this way. A consequence of the decomposition of such metastable minerals is that primary porosity will be swapped for secondary and that older and more deeply buried rocks will contain a higher proportion of secondary porosity. The mass-transport equation may be used to examine the physico-chemical environment where enhanced porosities most likely occur during leaching. By using a simple non-equilibrium mass-transport model based on the silica system it is possible to demonstrate the relative importance of flow rate, reaction rates, specific surfaces and temperature in controlling the areal extent of leaching. Wide leaching zones are related to high flow rates, which, in turn, promote a high throughput of undersaturated fluid and dispersion. Leaching over a wide area is also favoured by low reaction rates, which will occur at low temperatures. Although it is true to say that less of a given silicate mineral can be dissolved by an undersaturated pore water at low temperature than at high temperature, it is probable that pore fluids from deeply buried sediments are more likely to be close to equilibrium with a given mineral than, for instance, meteoric water. Thus the most likely environment for the production of widespread enhanced porosity is in the shallow subsurface. The lower flow rates and higher temperatures that are encountered during deep burial diagenesis will result in far narrower, more intense leaching zones. As a result, providing sufficient reactive mineral is present any undersaturated pore water will approach equilibrium in a short distance. In order to transport undersaturated pore waters appreciable distances in the deep subsurface, it is necessary to minimize their interaction with the host rock. This could occur if the pore fluid were to move through a fracture system where it would interact with a far smaller surface area of reactive mineral than if it moved through the pore network.

Silica-immobilised amine-platinum complexes as hydrosilylation catalysts

A simple method has been used to assess the efficiency of a variety of platinumamine compexes anchored to silica and anionic complexes supported on a silica-based ion-exchanger in the catalysis of the hydrosilylation of dec-1-ene by (Me 3SiO) 2Si(H)Me. In all cases, platinum was leached from the support, so that the catalyst became less active on each re-use. A rough correlation between extent of leaching and activity suggested that the effective catalysis was actually occurring homogeneously. The silane was responsible for the leaching.

The absence of leaching of molybdenum in acidic soils from Western Australia

A glasshouse experiment was conducted to estimate the extent of leaching of molybdenum on acidic sandy soils from Western Australia. Sodium molybdate, at a rate equivalent to 40 g of molybdenum per hectare, was added to pots of soil either before or after leaching a column of the soil with the equivalent of 500 mm water. Molybdenum concentrations were determined in the leachate and in the wheat plants grown on the soils in pots after leaching. Approximately 10% of added molybdenum was removed with leaching from two grey sands, while negligible quantities were removed from three more acidic sandy soils. Leaching does not appear to be an important factor in the occurrence and recurrence of molybdenum deficiency on the yellow-brown acidic sandplain soils of the Western Australian wheatbelt.

A lysimeter study of the fate of fertilizer nitrogen in spring barley crops grown on shallow soil overlying Chalk: crop uptake and leaching losses

SUMMARYThe objective of this work was to determine the fate of fertilizer nitrogen (labelled with nitrogen‐15) applied to an undisturbed shallow soil overlying Chalk contained in 10 lysimeters (80 cm diameter, 135 cm deep). Measurements are reported of the nitrogen uptake by four spring barley crops and the rate and extent of leaching of nitrate beyond the roots. The crops were fertilized with 0, 80 or 120 kg N ha−1 in each of four years, but only the first application in 1977 was labelled with nitrogen −15. Rainfall and irrigation approximated to the long‐term average, but in two treatments dry or wet spring conditions were imposed for the 10 weeks after sowing the first crop in 1977. The dry matter and grain yields of the spring barley crops varied from year to year in the ranges 8.7–14.0 t ha−1 and 3.5–6.1 t ha−1 respectively. The total nitrogen harvested in the crop approximated to the amount of nitrogen applied in each year with an apparent recovery of fertilizer in the range 38–76%. The recovery of nitrogen derived from fertilizer (labelled with nitrogen‐15) was 46–54% in the first crop and after 2 years rapidly declined to below 1%. The total amount of nitrogen‐15 labelled fertilizer recovered in four barley crops was 49–57% of that applied.Mean annual nitrate concentrations in water draining from the base of the lysimeters were in the range 11.8–26.7 mg N 1−1 and did not differ significantly between nitrogen fertilizer treatments (0, 80 and 120 kg N ha−1 a−1). In all treatments nitrate concentrations varied considerably within each growing season, with a cycle of peaks and troughs. Annual losses of nitrate were in the range 39–128 kg N ha−1, and the mean annual losses over the 4 years varied between lysimeters from 65 to 83 kg N ha−1. Nitrogen‐15 labelled nitrate was detected in the first drainage water collected in autumn following its spring application, 5 months earlier. Recovery of fertilizer‐derived nitrogen in drainage water was greatest during the winter following the second barley crop, and was 3.4–3.7% of the nitrogen‐15 applied. Over the 4 years of the experiment 6.3–6.6% of labelled fertilizer was accounted for in drainage water, representing 2–3% of the total nitrogen lost by leaching.

Effects of Freezing, Thawing, and Cooking on the Appearance of Highbush Blueberries

Abstract Increases in the darkness and redness of both thawed and cooked highbush blueberries (Vaccinium corymbosum L.), indicated by tristimulus measurements, were cultivar-related but not dependent on blueberry pH or anthocyanin content. Waxy bloom was retained in thawed berries but lost during cooking. Pigmented exudate appeared with some cultivars during thawing. Differences among cultivars in exudate formation and reddening during thawing are explained in terms of changes in epidermal cells, cuticle, and wax structure which were observed by light and electron microscopy. The color of blueberry cooking water depended primarily on the berry anthocyanin content, acidity, and the extent of leaching.

Selection of Containers and Closure Systems for Injectable Products

Factors related to the choice of appropriate container and closure systems for injectable drug products are discussed. The primary packaging system of an injectable product must ensure that the contents are protected against both loss from and entry into the system. Additionally, there must be no physicochemical incompatibility between the system and its contents. Containers in current use are either glass or plastic. Glass, a noncrystalline mixture of oxides, is reasonably resistant to chemical degradation, but its components will leach into solutions under appropriate conditions. Plastics commonly used include vinyls (polyvinyl chloride and ethylene vinyl acetate) and olefins (polyethylene and polypropylene). Various additives to these plastics will also leach into solutions under appropriate conditions. The final component of primary packaging systems is the closure, which is often rubber. Rubber, being natural in origin, contains many compounds in variable quantities, and these may leach into solutions. Three types of evaluations should determine which components are chosen for a packaging system. Functional evaluations assess sterilizability, puncture-reseal capability, and system integrity. Physicochemical screening tests for closures and plastic formulations measure the extent of leaching. Biologic screening tests are used to assess toxicity. An appropriate expiration date can be assigned after these screening tests are completed and stability data are obtained. Similar factors must be assessed by pharmaceutical scientists and hospital pharmacists in choosing packaging materials for injectable products.

Properties of aluminated silica sols

The properties of colloidal dispersions of “Positive Sol 130M” (E. I. du Pont de Nemours and Co.), which contains silica particles coated with alumina, have been studied in detail. Drifts of pH, leaching of aluminum species, and changes of electrokinetic mobility occurred during aging at room temperature for periods of up to a month, and were attributed to surface reactions. Despite its name, the sol has a point of zero charge (PZC) at pH 9, and consequently the particles carry a positive charge only below this pH. The alumina of the coating dissolves in acidic environments; the extent of leaching of aluminum species is dependent upon pH and length of aging at room temperature. The effect of different anions on this process was examined by using various inorganic acids; it was shown that phosphate and sulfate ions exhibit the strongest effects.

Effects of Solution Chemistry and Atmosphere on Leaching of Alkali Borosilicate Glass

ABSTRACTThe leaching behavior of two alkali-borosilicate glasses containing 9 wt% simulated fission products and 1.6 wt% uranium oxide has been studied. Samples were exposed to one of eight types of leachants including doubly distilled water, simulated ground silicate water, a brine solution, and solutions containing various concentrations of iron, aluminium or sodium maintained at either 25°C, 40°C or 90°C for up to 182 days. The most aggressive leachants were the solutions containing sodium (excluding brine) and simulated ground silicate water. These solutions increased the extent of leaching by a factor of 2–3 over that for distilled water for one of the glasses. A partially protective surface film rich in magnesium potassium and chlorine was formed on the glasses exposed to the brine solution.In order to evaluate the effects of atmosphere on leaching, samples were also immersed in doubly distilled water over which the relative concentrations of oxygen, nitrogen and carbon dioxide were varied. Increasing the carbon dioxide concentration from 0 to 50% resulted in a factor of 3 increase in the leaching rate.

Moisture absorption and its effect on the electrical properties of high silica fabric

High silica fabric with a silica content >98% can be prepared by removing the non-siliceous ions from the E-glass fabric using HCl as the leachant. The presence of Si-OH groups makes the material hydrophilic. The extent of moisture absorption depends on the extent of leaching. The moisture present in the leached fabric decreases the volume and surface resistivity values.

Distribution and recovery of nitrogen from legume residues decomposing in soils sown to wheat in the field

Unground 15N-labelled medic material ( Medicago littoralis) was mixed with topsoils at 3 field sites in South Australia, allowed to decompose for about 8 months before sowing wheat, and then for a further 7 months until crop maturity. The site locations were chosen to permit comparisons of recoveries and distribution of 15N in soils (organic N and inorganic N to 90 cm depth) and wheat (grain, straw and roots to 20 cm depth) in areas where rainfall (and wheat yields) differed greatly. Soils differed also in their texture and organic matter contents. Recoveries of applied 15N in wheat plus soil were 93.1% from a sandy loam (Caliph) and 92.3% from a sandy soil (Roseworthy) despite differences in rainfall and extent of leaching of the 15NO 3 − formed from the decomposing medic residues. From a heavy clay soil (Northfield), which received the highest rainfall, the 15N recovery was 87.7%. The loss of 15N at this site was not due to leaching, as judged by 15NO 3 − distribution in the soil profile at seeding and crop maturity. Wheat plants took up only 10.9–17.3% of the 15N added as legume material. Percentage uptakes of 15N were not related to grain yields. The proportions of wheat N derived from decomposing medic residues were 9.2% at Caliph (input medic, N, 38 kg N ha −1), 10.5% at Roseworthy (input medic N, 57 kg N ha −1), and only 4.6% at Northfield (input medic N, 57 kg N ha −1). Most (51–70%) of the 15N recovered in wheat was accounted for in the grain. Inorganic 15N in the soil profiles was depleted during the cropping phase, and at wheat harvest represented from 0.6 to 3.1% only of 15N inputs. The major 15N pool was soil organic 15N accounting for 71.9–77.7% of 15N inputs. We conclude that, in the context of N supply from decomposing medic tissues to wheat crops, the main value of the legume is long-term, i.e. in maintaining soil organic N concentrations to ensure adequate delivery of N to future cereal crops. The N of the wheat was not uniformly labelled, root N being generally of the highest atom% enrichmensts, and straw N of the lowest. Nevertheless, at the Roseworthy site, the enrichments of wheat N were similar to those of NO 3 − N in the profile at seeding, indicating that the proportions of 14N and 15N in the inorganic N pool did not change appreciably during the cropping period. By assuming equilibrium at this site, we calculate that during 15 months decomposition the soil plus legume delivered about 189 kg N ha −1, of which 93.2 kg ha −1 (49.3%) was taken up by the wheat, 37.2 kg ha −1 (19.7%) was immobilized or remained as fine root residues, and 17.3 kg ha −1 (9.2%) remained as inorganic N in the soil profile; 41.7 kg ha −1 (22.1%) was unaccounted for in the soil-plant system, and was probably lost via inorganic N. Thus about 6.5 kg inorganic N ha −1 was supplied by the soil plus medic residues per 100 kg dry matter ha −1 removed as wheat grain.

Waste Glass/Repository Interactions

ABSTRACTThe effects of repository material and a tailored backfill or overpack on the leaching behavior of glass have been studied. Two types of glasses were used in this investigation: 1) Model glasses comprised of 33 mol% alkali oxide-67 mol% SiO2 , and 2) alkali borosilicate glasses with and without simulated wastes. Several types of repository material were placed in the same containers as the glasses to determine if their presence would alter the extent of leaching. A backfill material consisting of phosphate slime/sand mixtures was evaluated with the same procedure. The results indicate that the leaching behavior of the glass may be influenced by the presence of some materials. Preliminary results of a 16½ month burial experiment in Florida are also discussed.

Nutrients in Subsurface and Runoff Waters of the Holland Marsh, Ontario

AbstractConcurrent with a limnological investigation of the Holland River, Ontario, an attempt was made to determine relative contributions to the river of nutrients (NO3−‐N, NO2−‐N, total and soluble reactive phosphorus) and total electrolyte (specific conductance) in surface runoff water pumped from both cultivated and uncultivated plots of muck soil within the Holland Marsh. In addition, subsurface water from piezometers installed in both cultivated and uncultivated marsh soil was analyzed throughout the growing season to determine fundamental differences in water chemistry and the extent of leaching of N and P under both cultivated and uncultivated conditions.The present study has shown that the time and amount of rainfall was important in determining nitrate‐N and to a lesser extent, soluble reactive P concentrations in subsurface water beneath the cultivated plot but not beneath the uncultivated plot. The mean concentration (0.75 mg/liter) of inorganic N (NO3−‐N + NO2−‐N + NH3‐N) in subsurface water under the cultivated plot was about 10 times higher than under uncultivated marsh during the growing season.The combined effects of fertilization, drainage and hence oxidizing and nitrifying conditions yielded 4 to 5 times more P (1.56 kg P/ha) and 40 to 50 times more nitrate‐N (4.1 kg N/ha) runoff water from the cultivated over the uncultivated plot. The significance of the loading from the cultivated plot is that the nutrients are lost to the river during a 5 to 6 week pumping period during the spring and that more than 90% of the total P in runoff is in the soluble reactive form (as opposed to only 45% from the uncultivated marsh) and is, therefore, readily available for algae and aquatic plant growth in the lower Holland River and Cook Bay of Lake Simcoe.