Nutrient removal from farm effluents.

The objectives of the study were: (i) to examine the efficiency of nutrient removal during the treatment of dairy farm effluent in a two-pond system, and (ii) to produce an inexpensive but effective nutrient trap which could be recycled as a nutrient source or soil mulch. The concentration of chemical oxygen demand (COD), biological oxygen demand (BOD), nitrogen (N), phosphorus (P) and potassium (K) in a two-pond system used to treat dairy farm effluent was monitored over a period of 7 months. The retention of nutrients by two porous materials was examined both in the laboratory batch (zeolite and bark) and pilot-scale field (bark) experiments. The results indicated that biological treatment of farm effluents using the two-pond system was not effective in the removal of nutrients, which are likely to become pollutant when discharged to waterways. Both the bark and zeolite materials were effective in the removal of N, P and K from effluent. These materials can be placed in the second (i.e., aerobic) pond to treat effluents, which can then be discharged to streams with minimum impact on water quality. The nutrient-enriched porous materials can be recycled as a source of nutrients and soil conditioner.

Design and assessment of a chamber to expose plants to simulated aerosol and rain.

Increased reports of contaminants in atmospheric aerosols necessitate the development of exposure systems that can accurately simulate aerosols for research purposes. This study outlines the design, construction, cost, and performance of a simple plexiglass chamber equipped with nozzles for rain and aerosol generation. The chamber occupies approximately 152 cm x 125 cm (height x width) space and can be used to expose six large (625 cm2) plants or twelve smaller (144 cm2) ones. The total cost of the materials used in construction, including nozzles, was less than 700 dollars. Repeated analysis of the quantity and particle size distribution of the simulated aerosol and rain showed them to be highly predictable. By adjusting the volume and/or concentration of the spray, and the position of plants within the chamber, particle sizes typical of environmental aerosols (< or = 20 microm) and rains (0.7 to 1.2 mm) could be applied to experimental plants. This sample, economical system will allow for precise simulations of important aerosols and rain events in the study of their impingement on plants.

Influence of zeolite, apatite and Fe-oxide on Cd and Pb uptake by crops.

Natural zeolite (clinoptilolite), hydroxyapatite and an iron-oxide waste by-product (Fe-rich, a trademark name of E.I. du Pont de Nemours) were added to an artificially contaminated Appling soil to immobilize and limit the uptake of metals by crops. A greenhouse pot study employed spiking the soil with Cd and Pb from metal flue dust. Maize (Zea mays) and barley (Hordeum vulgare) were planted in 7-kg potted soil to determine the effects of Cd and Pb on plant growth and uptake. Sequential extraction of soil indicates the substantial influence of soil pH and type of ameliorant on the chemical form and bioavailability of the metals. Data indicates that a dose of 50 g/kg of soil of iron-oxide appears to be very effective, based on the yields, metal contents of plant tissues and available forms of Cd and Pb in the soil. Lower doses of zeolite and apatite (15 g/kg and 4 g/kg soil, respectively) in most cases also reduced significantly the uptake of Cd and Pb by crops.

Distribution and bioavailability of copper in farm effluent.

Effluent and sludge samples from a number of dairy and piggery units in the North Island of New Zealand were collected and analysed for free ionic-copper (Cu(2+)) and organically-complexed Cu. The bioavailability of sludge-Cu was examined using microbial respiration and plant growth experiments. Microbial respiration was measured at various levels of Cu (0-1000 mg kg(-1)), added as copper sulfate (CuSO(4)) and sludge-Cu, using a Gilson differential respirometer. A glass house experiment was conducted to examine the transformation of Cu in soils and its subsequent uptake by ryegrass pasture. Three Cu sources were used that included fast-release CuSO(4), slow-release copper oxide (CuO) and Cu-enriched sludge. The pasture samples were analysed for Cu concentration. The transformation of Cu in the soil was monitored by analysing the soil samples for various fractions of Cu. The effluent and sludge samples collected from farms which regularly used Cu to treat lameness in dairy cattle and as a growth promoter in swine contained higher concentration of Cu. The total Cu concentration ranged from approximately 0.1 to 1.55 mg l(-1) and from 0.5 to 10.5 mg l(-1) in the piggery and diary effluent, respectively. The corresponding values for the sludge samples were 3.0-526 and 25-105 mg kg(-1). Most of the Cu in both the effluent and solid sludge material was organically complexed. The respiration measurements indicated that sludge-Cu was less toxic to soil microbial activity than CuSO(4). The results from the glass house experiment indicated that increasing the level of Cu applied through fertilisers and sludge increased Cu concentration in plants. At the same rate of application, plants took up less Cu from sludge and CuO than from CuSO(4). There was, however, a greater translocation of Cu from root to shoot at the highest rate of Cu through sludge application. The Cu fractionation study indicated that there was greater accumulation of organic bound Cu in the sludge-treated soil than the fertiliser-treated soil.

Influence of fly ash on soil physical properties and turfgrass establishment.

A field study (1993-96) assessed the benefits of applying unusually high rates of coal fly ash as a soil amendment to enhance water retention of soils without adversely affecting growth and marketability of the turf species, centipedegrass [Eremochloa ophiuroides (Munro) Hack.]. A Latin Square plot design was employed that included 0 (control, no ash applied), 280, 560, and 1120 Mg ha-1 application rates of unweathered precipitator fly ash. The fly ash was spread evenly over each plot area, rototilled, and allowed to weather under natural conditions for 8 mo before seeding. High levels of soluble salts, indicated by the electrical conductivity (EC) of soil extracts, in tandem with an apparent phytotoxic effect from boron (B), apparently inhibited initial plant establishment as shown by substantially lower germination counts in treated soil. However, plant height and rooting depth were not adversely affected, as were the dry matter (DM) yields throughout the study period. Ash treatment did not significantly influence water infiltration rate, bulk density, or temperature of the soil, but substantially improved water-holding capacity (WHC) and plant-available water (PAW). Enhanced water retention capacity improved the cohesion and handling property of harvested sod.

Effect of flue gas desulfurization residue on plant establishment and soil and leachate quality.

Effects on soil quality and crop establishment after incorporation of flue gas desulfurization by-product (FGD) into soil as an amendment was assessed in a mesocosm study. Mesocosm units received applications equivalent to 0, 2.5, 5.0, 7.5, and 10% FGD residue [0, 25, 50, 75, and 100 tons acre(-1)]. Germination, biomass production, and elemental composition of corn (Zea mays L. var. Dekalb DK-683), soybean [Glycine max (L.) Merr. var. Haskell Pupa 94], radish (Raphanus sativus L. var. Sparkler), and cotton (Gossypius hirsutus L. var. Deltapine 51) were determined. The quality of leachates and soil were also determined periodically. Flue gas desulfurization residue did not affect germination and all application rates stimulated aboveground biomass. Plants grown in FGD-amended soil contained significantly elevated tissue concentrations of As, B, Se, and Mo. The FGD residue elevated surface soil pH from 5.5 (Control) to 8.1 (at 10% FGD). Leachate pH was unaffected by FGD, but salinity rose sharply with increasing application rates of FGD. Leachates contained higher concentrations of B, with small increases in Se and As. Flue gas desulfurization residue application caused an increase in total B, As, Mo, Se, and extractable Ca in the soil, but decreased Mn and Zn. Using FGD residues could have beneficial effects on crop establishment without detrimental effects on soil or leachate quality, at an optimum rate of approximately 2.5%. This material could alleviate surface acidity, and B and Mo deficiencies in plants.

Effects of organic amendments on the reduction and phytoavailability of chromate in mineral soil.

In this study, seven organic amendments (biosolid compost, farm yard manure, fish manure, horse manure, spent mushroom, pig manure, and poultry manure) were investigated for their effects on the reduction of hexavalent chromium [chromate, Cr(VI)] in a mineral soil (Manawatu sandy soil) low in organic matter content. Addition of organic amendments enhanced the rate of reduction of Cr(VI) to Cr(III) in the soil. At the same level of total organic carbon addition, there was a significant difference in the extent of Cr(VI) reduction among the soils treated with organic amendments. There was, however, a significant positive linear relationship between the extent of Cr(VI) reduction and the amount of dissolved organic carbon in the soil. The effect of biosolid compost on the uptake of Cr(VI) from the soil, treated with various levels of Cr(VI) (0-1200 mg Cr kg(-1) soil), was examined with mustard (Brassica juncea L.) plants. Increasing addition of Cr(VI) increased Cr concentration in plants, resulting in decreased plant growth (i.e., phytotoxicity). Addition of the biosolid compost was effective in reducing the phytotoxicity of Cr(VI). The redistribution of Cr(VI) in various soil components was evaluated by a sequential fractionation scheme. In the unamended soil, the concentration of Cr was higher in the organic-bound, oxide-bound, and residual fractions than in the soluble and exchangeable fractions. Addition of organic amendments also decreased the concentration of the soluble and exchangeable fractions but especially increased the organic-bound fraction in soil.

Apatite and phillipsite as sequestering agents for metals and radionuclides.

Laboratory and greenhouse studies were conducted to quantify apatite and phillipsite (zeolite) sequestration of selected metal contaminants. The laboratory batch study measured the sorption of aqueous Co2+, Ba2+, Pb2+, Eu3+, and UO2(2+). Apatite sorbed more Co2+, Pb2+, Eu3+, and UO2(2+) from the spike solution than phillipsite, resulting in distribution coefficients (Kd values) of >200,000 L kg(-1). Phillipsite was more effective than apatite at sorbing aqueous Ba2+. Results from the laboratory study were used to design the greenhouse study that used a soil affected by a Zn-Pb smelter from Pribram, Czech Republic. Two application rates (25 and 50 g kg(-1)) of phillipsite and apatite and two plant species, maize (Zea mays L.) and oat (Avena sativa L.), were evaluated in this study. There was little (maize) to no (oat) plant growth in the unamended contaminated soil. Apatite and, to a slightly lesser extent, phillipsite additions significantly enhanced plant growth and reduced Cd, Pb, and Zn concentrations in all analyzed tissues (grain, leaves, and roots). The sequestering agents also affected some essential elements (Ca, Fe, and Mg). Phillipsite reduced Fe and apatite reduced P and Fe concentrations in oat tissues; however, the level of these elements in oat leaves and grains remained sufficient. Sequential extractions of the soil indicated that the Cd, Pb, and Zn were much more strongly sorbed onto the amended soil, making the contaminants less phytoavailable.

The accuracy of some simple models for predicting particulate interception and retention in agricultural systems.

The accuracy of three radionuclide transfer models for predicting the interception and retention of airborne particles by agricultural crops was tested using Pu-bearing aerosols released to the atmosphere from nuclear fuel facilities on the U.S. Department of Energy's Savannah River Plant, near Aiken, SC. The models evaluated were: 1) NRC, the model defined in U.S. Nuclear Regulatory Guide 1.109; 2) FOOD, a model similar to the NRC model that also predicts concentrations in grains; and 3) AGNS, a model developed from the NRC model for the southeastern United States. Plutonium concentrations in vegetation and grain were predicted from measured deposition rates and compared to concentrations observed in the field. Crops included wheat, soybeans, corn and cabbage. Although predictions of the three models differed by less than a factor of 4, they showed different abilities to predict concentrations observed in the field. The NRC and FOOD models consistently underpredicted the observed Pu concentrations for vegetation. The AGNS model was a more accurate predictor of Pu concentrations for vegetation. Both the FOOD and AGNS models accurately predicted the Pu concentrations for grains.

Uptake of 137Cs in vegetable crops grown on a contaminated lakebed.

Mean concentrations and plant:soil concentration ratios of 137Cs were determined for six vegetable crops grown on an exposed, contaminated lakebed of a former reactor cooling reservoir in South Carolina. Each crop species was grown with or without potassium fertilizer. Selected crops were also irrigated with either reservoir water or groundwater. Subsamples of crops were prepared for human consumption before analysis to determine the extent of any loss. Plant:soil concentration ratios (dry basis) ranged from 0.22 to 6.82, values which were substantially higher than those used in generic assessment models. While there was no statistically significant effect of irrigation source or culinary preparation, the effect of potassium-fertilizer was dramatic. In many cases, concentrations of 137Cs in those plants receiving potassium were less than half of the concentrations in plants that did not receive potassium. Significant differences among species and plant parts for 137Cs concentrations were observed. Dose/risk calculations for the ingestion of these vegetables by a hypothetical 30-y resident indicates the possibility of a lifetime fatal cancer risk well-above the U.S. Environmental Protection Agency's regulatory guideline of 10(-4).

Atmospheric deposition, resuspension, and root uptake of Pu in corn and other grain-producing agroecosystems near a nuclear fuel facility.

Plutonium released to the environment may contribute to dose to humans through inhalation or ingestion of contaminated foodstuffs. Plutonium contamination of agricultural plants may result from interception and retention of atmospheric deposition, resuspension of Pu-bearing soil particles to plant surfaces, and root uptake. Plutonium on vegetation surfaces may be transferred to grain surfaces during mechanical harvesting. Data obtained from corn grown near the U.S. Department of Energy's H-Area nuclear fuel chemical separations facility on the Savannah River Site were used to estimate parameters of a simple model of Pu transport in agroecosystems. The parameter estimates for corn were compared to those previously obtained for wheat and soybeans. Despite some differences in parameter estimates among crops, the relative importances of atmospheric deposition, resuspension, and root uptake were similar among crops. For even small deposition rates, the relative importances of processes for Pu contamination of corn grain should be: transfer of atmospheric deposition from vegetation surfaces to grain surfaces during combining greater than resuspension of soil to grain surfaces greater than root uptake. Approximately 3.9 X 10(-5) of a year's atmospheric deposition is transferred to grain. Approximately 6.2 X 10(-9) of the Pu inventory in the soil is resuspended to corn grain, and a further 7.3 X 10(-10) of the soil Pu inventory is absorbed and translocated to grains.

The interception and retention of 238Pu deposition by orange trees.

Radioisotope thermoelectric generators (RTG) transform the heat produced during the alpha decay of 238Pu into electrical energy for use by deep-space probes, such as the Voyager spacecraft, which have returned images and other data from Jupiter, Saturn and Uranus. Future missions involving RTGs may be launched aboard the space shuttle, and there is a remote possibility that an explosion of liquid-hydrogen and liquid-oxygen fuel could rupture the RTGs and disperse 238Pu into the atmosphere over central Florida. Research was performed to determine the potential transport to man of atmospherically dispersed Pu via contaminated orange fruits. The results indicate that the major contamination of oranges would result from the interception and retention of 238Pu deposition by fruits. The resulting surface contamination could enter human food chains through transfer to internal tissues during peeling or in the reconstituted juices and flavorings made from orange skins. The interception of 238Pu deposition by fruits is especially important because the results indicate no measurable loss of Pu from fruit surfaces through time or with washing. Approximately 1% of the 238Pu deposited onto an orange grove would be harvested in the year following deposition.

Uptake of 244Cm, 238Pu and other radionuclides by trees inhabiting a contaminated flood plain.

The plant uptake of 244Cm, 137Cs, 238Pu and 90Sr was measured for trees in a flood plain forest whose soils were contaminated by aqueous discharges from a nuclear-fuel chemical separations facility. Uptake of the naturally occurring radionuclide 226Ra was also measured. The relative availability of the nuclides was 238Pu less than 244Cm less than 137Cs less than 226Ra less than or equal to 90Sr. The concentration ratios for 238Pu and 244Cm, 3 X 10(-4) and 3.6 X 10(-3), respectively, were similar to those reported for other plant-soil systems. The ratios for 137Cs and 90Sr, 0.11 and 3.9, were similar to those reported for other southeastern soils. However, the ratio for 226Ra, 2.1, was greater than that normally reported. These ratios, which were determined in the field, were generally similar to those reported for greenhouse studies on the same soil.

Plutonium contents of broadleaf vegetable crops grown near a nuclear fuel chemical separations facility.

Among agricultural crops, broadleaf vegetables are particularly prone to intercept and retain aerially released contaminants. The plutonium concentration of four broadleaf crops (broccoli, cabbage, lettuce and turnip greens) was determined, when grown in close proximity to a nuclear-fuel chemical-separations facility. Concentrations varied among species, apparently influenced by the crop morphology, with Pu concentrations increasing in the sequence: cabbage less than broccoli less than turnip greens less than lettuce. Washing of the crops significantly reduced the Pu concentration of lettuce, but had no effect on Pu concentration of broccoli and cabbage. The vast majority of Pu found in the crops was due to direct deposition of recently released Pu and resuspension of Pu-bearing soil particles, and was not due to root uptake. Resultant doses from consumption are small relative to the annual background dose.

The relative importance of uptake and surface adherence in determining the radionuclide contents of subterranean crops.

The adherence of Pu-bearing particles to external surfaces of carrots, turnips, red potatoes, and sweet potatoes accounted for greater than or equal to 93% of their total Pu content. Uptake, which was measured as Pu content in peeled crops, accounted for less than or equal to 7%. Plutonium concentrations in most peeled crops were below background, and consequently, uptake could not be conclusively demonstrated. However, uptake accounted for most of the 137Cs, 40K, and 226Ra contents of subterranean crops. Concentration ratios for total radionuclide contents (i.e. surface adherence plus uptake) ranged from 3.9 X 10(1) for 40K, to 1.1 X 10(-2) for 239, 240Pu. Approximately 1.5 X 10(-3) pCi 239, 240Pu adhered per cm2 of subterranean crop surface per 1 pCi Pu/g of soil.