John H. Peverly

Movement of heavy metals through undisturbed and homogenized soil columns

When sewage sludge is applied to land for disposal or intended beneficial use, heavy metals accumulate in the soil. Because of environmental concerns, many studies have been undertaken in an attempt to clarify the different factors that contribute to metal solubility, plant uptake, and leachability. This study attempted to determine if two independent factors - soluble organic chelators and preferential flow paths - enhance metal mobility through soil. Dilute solutions containing CdCl{sub 2}, ZnCl{sub 2}, CuCl{sub 2}, and Pb(NO{sub 3}){sub 2} were applied to soil columns with a rainmaker, and leachate metals and chloride concentrations were measured. For four columns, the input metal concentrations (mg L{sup {minus}1}) were 7.25 Cd, 4.55 Zn, 3.51 Cu, and 13.85 Pb. In other four other columns, the solution also contained dissolved organic matter so that the metals were organically complexed, and input metal concentrations (mg L{sup {minus}1}) were 6.30 Cd, 4.11 Zn, 3.19 Cu, and 12.55 Pb. For each treatment, two soil columns were undisturbed and two were constructed from homogenized soils. The continuous solution application rate was approximately 3 cm/day. The undisturbed soil columns treated with organically complexed metals had peak effluent concentrations of 30, 26, 28, and 27% for Cd, Zn, Cu,morexa0» and Pb, respectively. Peak effluent concentrations for undisturbed columns treated with metals in water were 30 and 23% of influent concentrations for Cd and Zn, but only 15 and 12% for Cu and Pb, respectively. However, the four homogenized soil columns retained all added metals, whether the metals were added in water or as organic complexes. The results indicate that previous laboratory metal leaching studies performed on homogenous soils might have greatly underestimated metal mobility in the field and that preferential flow, both alone and in combination with organic-facilitated transport, can accelerate metal leaching through soils. 32 refs., 4 figs., 5 tabs.«xa0less

Growth and trace metal absorption by Phragmites australis in wetlands constructed for landfill leachate treatment

Phragmites australis (common reed) grew well in the presence of high concentrations of NH4+-N (300 mg/1), BOD (300 mg/1), Fe (30 mg/1), Mn (1.5 mg/1) and K (500 mg/1). Other metals were not particularly elevated with the pH of the landfill leachate being 7-7.2. Reed standing crop continued to increase in the two years after leachate applications began, ranging to about 1100, 100, and 1000 g/m2 dry wt. for shoots, roots and rhizomes, respectively. Nutrient elements like N, K, Ca, and Mg were absorbed to normally sufficient levels, while tissue P was low at 0.04%. Metals were not translocated to and accumulated by shoots or rhizomes, but exhibited elevated levels in roots. Fe, Cu, Zn, Pb, and Cd were at levels of 3700, 65, 45, 12 and 0.2 mg/kg respectively, but the roots acted as effective filters for transport of metals to the shoots and rhizomes. Only P and Zn accumulation by plants approached total amounts in leachate entering the constructed beds. SEM and X-ray microanalysis showed Fe accumulation on root surfaces, with Fe and other metals at lower concentrations inside the root tissue. The rhizosphere may provide a particularly effective, locally oxidized environment for metal precipitation and adsorption outside the root.

Effect of sludge-processing mode, soil texture and soil pH on metal mobility in undisturbed soil columns under accelerated loading.

The effect of sludge processing (digested dewatered, pelletized, alkaline-stabilized, composted, and incinerated), soil type and initial soil pH on trace metal mobility was examined using undisturbed soil columns. Soils tested were Hudson silt loam (Glossaquic Hapludalf) and Arkport fine sandy loam (Lamellic Hapludalf), at initial pH levels of 5 and 7. Sludges were applied during four accelerated cropping cycles (215 tons/ha cumulative application for dewatered sludge; equivalent rates for other sludges), followed by four post-application cycles. Also examined (with no sludge applications) were Hudson soil columns from a field site that received a heavy loading of sludge in 1978. Romaine (Lactuca sativa) and oats (Avena sativa) were planted in alternate cycles, with oats later replaced by red clover (Trifolium pratense). Soil columns were watered with synthetic acid rainwater, and percolates were analyzed for trace metals (ICP spectroscopy), electrical conductivity and pH. Percolate metal concentrations varied with sludge and soil treatments. Composted sludge and ash had the lowest overall metal mobilities. Dewatered and pelletized sludge had notable leaching of Ni, Cd and Zn in Arkport soils, especially at low pH. Alkaline-stabilized sludge had the widest range of percolate metals (relatively insensitive to soils) including Cu, Ni, B and Mo. Old site column percolate concentrations showed good agreement with previous field data. Little leaching of P was observed in all cases. Cumulative percolate metal losses for all treatments were low relative to total applied metals. Leachate and soil pH were substantially depressed in dewatered and pelletized sludge soil columns and increased for alkaline-stabilized and ash treatments.

Metal mobility at an old, heavily loaded sludge application site.

This study was undertaken to determine the present distribution and mobility of sludge-applied metals at an old land application site. Trace metals concentrations were determined for soils (using 4 M HNO3 extracts), soil leachates (collected with passive wick lysimeters over a 2.5-year period), and plant tissue from a field site which received a heavy loading of wastewater sludge in 1978 and an adjacent control plot. Blue dye was used to indicate preferential percolate flowpaths in the sludge plot soil for sampling and comparison with bulk soil metals concentrations. After nearly 20 years, metals in the sludge plot leachate were found at significantly greater concentrations than in the control plot, exceeding drinking water standards for Cd, Ni, Zn, and B. Annual metals fluxes were only a fraction of the current soil metal contents, and do not account for the apparent substantial past metals losses determined in a related study. Elevated Cd, Cu, and Ni levels were found in grass growing on the sludge plot. Despite heavy loadings, fine soil texture (silty clay loam) and evidence of past and ongoing metals leaching, examination of the bulk subsoil indicated no statistically significant increases in metals concentrations (even in a calcareous subsoil horizon with elevated pH) when comparing pooled sludge plot soil profiles with controls. Sampling of dyed preferential flow paths in the sludge plot detected only slight increases in several metals. Preferential flow and metal complexation with soluble organics apparently allow leaching without easily detectable readsorption in the subsoil. The lack of significant metal deposition in subsoil may not be reliable evidence for immobility of sludge-applied metals.

Hydraulic conductivity of gravel and sand as substrates in rock-reed filters

Abstract Long-term use of a constructed wetland to treat landfill leachate requires that the saturated hydraulic conductivity be maintained and clogging avoided to prevent overland flow, which bypasses the treatment process. This paper describes the application of an equation developed for prediction of cumulative drainage volume from hillslopes to measure the saturated hydraulic conductivity ( K s ) of substrates used in rock-reed filters. Outflow was measured at five intervals during the first 26 months of operation. The values of K s ) obtained by the drainage equation compared favorably with values calculated from a more dificult method based on Darcys law. Results indicate that the finest substrate (a sand-and-gravel mixture) became almost completely clogged, and that the presence of reeds ( Phragmites australis ) did not maintain or increase the conductivity. Hydraulic conductivity of pea-gravel (0.5-cm diameter) and coarse-gravel (3-cm diameter) substrates with reeds did decrease in the 26-month period.

Changes in submerged plants at the South end of Cayuga Lake following Tropical Storm Agnes

Tropical Storm Agnes produced increased suspended sediments and decreased water transparency at the southern end of Cayuga Lake for a sustained period during the early summer of 1972. The 1972 community of submerged vascular plants was severely affected. Standing crops were drastically reduced and the species composition of the plant community changed compared to 1970. In 1973, standing crop values had increased to 87% of those of 1970. However, shifts in spatial distribution had occurred and the community had further changed to one highly dominated by Myriophyllum sp. with the virtual exclussion of some previously abundant forms, especially Heteranthera dubia.

Flow characteristics of rock-reed filters for treatment of landfill leachate

Abstract To characterize the flow patterns of wastewater through subsurface-flow rock-reed filters, a combination of tracer studies and specific conductance measurements were used. Neither the tracer study nor the specific conductance measurements alone provided the necessary information to understand the flow of wastewater through the system. However, the data taken together indicate that preferential flow occurred due to density effects and surface flow. In gravel substrates, dense wastewater flowed beneath the less dense rainwater and influent, resulting in a decrease in the residence time. Sand-and-gravel substrates, which experienced a great deal of surface flow as a result of clogging, were shown to have very little, if any, flow through the subsurface. The results of this study indicate that both preferential and overland flow should be taken into account for the proper design of rock-reed filters.

Elemental distribution and macrophyte growth downstream from an organic soil

Abstract Little Conesus Creek, which drains a cultivated organic soil deposit in central New York State, was monitored at several sites for over a year (March 1975–June 1976) for flow, concentrations of dissolved N, P, K, O 2 , minor elements, pH, alkalinity, sediment characteristics, aquatic plant growth and tissue content. The stream was well-oxygenated and near saturation with CO 2 most of the time. Dissolved concentrations ranged from 0.003 to 7 mg l −1 for N, 0.05–1 mg l −1 for P, 2–5 mg l −1 for K, 70–90 mg/l −1 for Ca, 0.04–0.5 mg l −1 for Fe, and 0.001–0.006 mg l −1 for Zn. Concentrations generally increased as flows increased, so that by far the greatest quantity of nutrients was carried by the water in spring and early summer when the aquatic macrophytes were growing at the maximum rate. Phosphorus levels exceeded N levels in the late summer and autumn. Maximum standing crop (387 g dry wt. m −2 ) was achieved by a pure stand of Myriophyllum spicatum L. in October. Mineral content of the aquatic macrophyte tissue peaked in early summer, but total nutrients in the plants peaked at the time of maximum standing crop. High nutrient levels in the water, sediments and plant tissues indicated the nutrient-rich status of this stream. Plant growth was limited by physical factors, not nutrient availability. Of the major nutrients at least 20 times more was transported down the stream than was absorbed during the period of maximum growth. Absorption of nutrients by roots may have occurred, as interstitial water concentrations of all plant nutrients were higher than in the stream. Sediments probably acted as a sink for most nutrients. When flow and stream concentrations are low, such as in autumn, the N, P, and Zn released by macrophyte senescence could be a large fraction of total stream load. Cadmium and Pb were not concentrated by macrophytes to any great extent.

Fluorescence and reflectance characteristics of manganese deficient soybean leaves: effects of leaf age and choice of leaflet

Leaf reflectance and fluorescence characteristics of soybean (Glycine max cv ‘Bragg’) are influenced strongly by Mn availability. This report evaluates the effects of leaflet choice, leaf age, and leaf nodal position on several spectral characteristics. Leaves were obtained from soybeans grown hydroponically under controlled environmental conditions with wide differences in Mn supply. The ratio of ‘constant yield’ fluorescence (Fo) to ‘variable yield’ fluorescence (Fv), the ratios of reflectance at 750 nm to 550 nm and that at 650 nm to 550 nm, the position of the red edge near 700 nm, and an index of leaf yellowness were measured periodically. Increasing leaf age caused increases in the red edge and in both reflectance ratios. Leaf yellowness and the fluorescence ratio Fo/Fv decreased with leaf age and increased with leaf nodal position, primarily in Mn deficient leaves. Effects arising from leaf choice were smaller than those caused by Mn deficiency.

POTASSIUM IN POLYPHOSPHATE BODIES OF CHLORELLA PYRENOIDOSA (CHLOROPHYCEAE) AS DETERMINED BY X-RAY MICROANALYSIS1

Potassium is an important component information of polyphosphate bodies (PB) by Chlorella pyrenoidosa Chick. However, it was not detected in PB by X‐ray energy dispersive microanalyses when the specimens were subjected to a standard preparation procedure for transmission electron microscopy. Intact cells were incinerated at 350 C on stainless steel grids coated with silicon monoxide. X‐ray spectra from PB showed conspicuous peaks of energy counts in the Kα lines for phosphorus and potassium. It is proposed that potassium is a major cationic component of PB in C. pyrenoidosa grown in potassium sufficient medium.