John L. Cisar

Evaluating nutrient impacts in urban watersheds: Challenges and research opportunities

This literature review focuses on the prevalence of nitrogen and phosphorus in urban environments and the complex relationships between land use and water quality. Extensive research in urban watersheds has broadened our knowledge about point and non-point pollutant sources, but the fate of nutrients is not completely understood. For example, it is not known how long-term nutrient cycling processes in turfgrass landscapes influence nitrogen retention rates or the relative atmospheric contribution to urban nitrogen exports. The effect of prolonged reclaimed water irrigation is also unknown. Stable isotopes have been used to trace pollutants, but distinguishing sources (e.g., fertilizers, wastewater, etc.) can be difficult. Identifying pollutant sources may aid our understanding of harmful algal blooms because the extent of the relationship between urban nutrient sources and algal blooms is unclear. Further research on the delivery and fate of nutrients within urban watersheds is needed to address manageable water quality impacts.

The occurrence and alleviation by surfactants of soil-water repellency on sand-based turfgrass systems

Even with routine irrigation, soil water-repellency on sand-based turfgrass systems can occur. This study evaluated three commercially available surfactants alone or in combination in 1996, four experimental surfactant formulations in 1997, and four commercially available surfactants and one experimental surfactant in 1998 for their effect on reducing soil-water repellency in mature Cynodon dactylon X Cynodon transvaalensis cv. Tifdwarf sand-based greens. The treatments in 1996 were a commercial standard AquaGro (AG), and two new products, Primer (P) and Aqueduct (AD), applied as liquids at the rates 250, 190 and 250 ml per 100 m 2 , respectively, and a control. Combination treatments of P + AG, and P + AD were also applied at standard rates. Surfactants were evaluated for their effect on turfgrass quality and percent dry spot incidence through a period of drought that induced soil-water repellency symptoms and subsequently through a period of recovery. Water drop penetration time (WDPT). on the soil cores were determined. Data were analyzed for statistical significance (P < 0.05) by automated ANOVA procedures. Results in 1996 demonstrated that during a period of drought, P or AD generally provided both significantly (P < 0.05) higher turfgrass quality and reduced percent dry spotting than AG and the control. Primer or AD significantly (P < 0.05) reduced WDPT. Furthermore, during a recovery period following the drought. P or AD provided significantly (P < 0.05) higher turfgrass quality than untreated controls. Combinations of P + AG or P + AD did not provide significantly higher quality turfgrass or less percent dry spots than individua applications of either P or AD. The second experiment in 1997 consisted of four experimental surfactant formulations of (ACA 1257, ACA 1313, ACA 1455, and ACA 1457), and a control applied at the recommended rate of 250 ml per 100 m 2 , weekly, to plots. As in 1996, surfactants were visually evaluated for turfgrass quality and percent dry spot incidence and soil cores for WDPT. Results demonstrated that ACA treatments generally provided significantly (P < 0.10) higher turfgrass quality and reduced percent dry spotting than the untreated control In 1998, for the third experiment, on a green with extensive soil-water repellency, AD,P, Cascade, LescoFlo, and an experimental surfactant (N-07/05) were applied to alleviate soil water repellency symptoms. The four commercially available surfactants performed well and provided statistically equivalent (P < 0.01) and better turfgrass quality and percent dry spot reduction than the untreated control. The N-07/05 treatment improved turfgrass quality and reduced dry spots compared to the untreated plots as well, but on most dates did not perform as well as the commercial standards.

Role of soil-derived dissolved substances in arsenic transport and transformation in laboratory experiments

Dissolved substances derived from soil may interact with both soil surfaces and with arsenic and subsequently influence arsenic mobility and species transformation. The purpose of this study was to investigate arsenic transport and transformation in porous media with a specific focus on the impact of soil-derived dissolved substances, mainly consisting of inorganic colloids and dissolved organic matter (DOM), on these processes. Arsenic transport and transformation through columns, which were packed with uncoated sand (UC) or naturally coated sand (NC) and fed with arsenate (AsV) or monomethylarsonic acid (MMA) spiked influents, were investigated in the presence or absence of soil-derived dissolved substances. The presence of soil-derived inorganic colloids and/or DOM clearly enhanced As transport through the column, with the fraction of As leached out of column (referring to the total amount added) being increased from 23 to 46% (UC) and 21 to 50% (NC) in AsV experiments while 46 to 64% (UC) and 28 to 63% (NC) in MMA experiments. The association of arsenic with DOM and the competitive adsorption between arsenic and DOM could account for, at least partly, the enhanced As movement. Distinct species transformation of As during transport through soil columns was observed. When AsV was the initial species spiked in the influent solutions, only arsenite (AsIII) was detected in the effluents for UC columns; while both AsIII (dominant) and AsV were present for NC columns, with AsIII being the dominant species. When MMA was initially spiked in the influent solutions, all method detectable As species, AsIII, AsV, MMA, and dimethylarsenic acid (DMA) were present in the effluents for both soil columns. These results indicate that risk assessment associated with As contamination, particularly due to previous organoarsenical pesticide applications, should take into account the role of soil-derived dissolved substances in promoting As transport and As species transformation.

A modified autoanalyzer II method for the determination of NO3-N in water using a hollow-Cd reduction coil

Abstract The Technicon AutoAnalyzer II (AAII) is used routinely by many laboratories for determination of NO3‐N in water. The methodology involves the use of a packed‐Cd column for reduction of NO3‐N to NO2‐N, which subsequently is determined colorimetrically. A newer instrument, the Technicon TRAACS 800, uses a hollow‐Cd coil for NO3 ‐N reduction. A method is described for adapting the hollow‐Cd coil to the AAII for determination of NO3‐N in water samples. This adaptation was found to increase throughput rate and to decrease the time required for column preparation.

Response to Comment on Arsenic Transport and Transformation Associated with MSMA Application on a Golf Course Green

The impact of extensively used arsenic-containing herbicides on groundwater beneath golf courses has become a topic of interest. Although currently used organoarsenicals are less toxic, their application into the environment may produce the more toxic inorganic arsenicals. The objective of this work was to understand the behavior of arsenic species in percolate water from monosodium methanearsonate (MSMA) applied golf course greens, as well as to determine the influences of root-zone media for United State Golf Association (USGA) putting green construction on arsenic retention and species conversion. The field test was established at the Fort Lauderdale Research and Education Center (FLREC), University of Florida. Percolate water was collected after MSMA application for speciation and total arsenic analyses. The results showed that the substrate composition significantly influenced arsenic mobility and arsenic species transformation in the percolate water. In comparison to uncoated sands (S) and uncoated sands and peat (S + P), naturally coated sands and peat (NS + P) showed a higher capacity of preventing arsenic from leaching into percolate water, implying that the coatings of sands with clay reduce arsenic leaching. Arsenic species transformation occurred in soil, resulting in co-occurrence of four arsenic species, arsenite (As(III)), arsenate (As(V)), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in percolate water. The results indicated that substrate composition can significantly affect both arsenic retention in soil and arsenic speciation in percolate water. The clay coatings on the soil particles and the addition of peat in the soil changed the arsenic bioavailability, which in turn controlled the microorganism-mediated arsenic transformation. To better explain and understand arsenic transformation and transport after applying MSMA in golf green, a conceptual model was proposed.