Retardant Chemicals Research Articles

Ground‐Water Sampling and Time‐Series Evaluation Techniques to Determine Vertical Concentration Distributions

AbstractData analysis methodologies are developed for using time‐series measurements of effluent concentrations during continuous sampling to determine the vertical shape and location of a horizontally uniform contaminant plume and to estimate physical/ chemical aquifer parameters such as vertical anisotropy, effective porosity, and retardation factor. Temporal water‐quality variations during constant‐flow sampling are calculated in the form of concentration type curves for a wide variety of plume shapes and positions and are shown to be directly related to the geometry and growth rate of the three‐dimensional capture volume of the well. An analytical type‐curve solution is derived for discrete‐interval sampling in homogeneous and isotropic/anisotropic aquifers containing plumes with complex vertical shapes that are described by the superposition of multiple Gaussian distributions. Results from two‐dimensional, axisymmetric simulations of ground‐water flow and particle transport demonstrate the sensitivity of concentration type curves to sandpack hydraulic conductivity, screen length, well diameter, flow through the well screen during discrete‐interval sampling, aquifer anisotropy and heterogeneities, pumping rate, effective porosity, and chemical retardation. Two applications of the concentration type‐curve method for determining plume and aquifer characteristics are presented. The first illustrates the use of discrete‐interval sampling to evaluate the vertical shape and location of a hypothetical plume in a homogeneous, isotropic aquifer. In the second, extraction‐well effluent data collected during a field experiment were used to evaluate the vertical concentration distribution in a sulfate plume and estimate the vertical anisotropy ratio of the aquifer. The results demonstrate the importance of developing consistency in purge and sample volumes to minimize artificial measurement variability in monitoring programs.

Apparent first-order kinetics in the transformation of 1,1,1-trichloroethane in groundwater following a transient release

A transient release of 1,1,1-trichloroethane (TCA) to an otherwise uncontaminated aquifer at a manufacturing facility presented a useful opportunity to validate the results of previous laboratory and field studies on TCA transformation in groundwater. Abiotic TCA transformation to 1,1-dichloroethylene (DCE) and acetic acid at the site exhibited first-order kinetics with half-life of 2.9 years 15° C. Degradation effects were seen to overwhelm chemical retardation effects on the DCE/TCA concentration ratio in groundwater. The kinetic data was sufficient to date the release to within one week of when it actually occurred. A kinetic approach may be applicable to dating the releases on other contaminated sites where a single transient release is indicated. The transformation of dissolved TCA in groundwater with a half-life of several years can be expected at many contaminated sites.

Patent abstracts

In world patent 9425267 Albany International Res. Co. describes a structural, non‐weight‐bearing element for use in aircraft. A composite element comprises a non‐woven web of glass fibres filled with phenolic resin containing chemical flame retardant such as aluminium trihydrate or zinc borate. There is a further layer of woven cloth or fibrous scrim, such as filament and glass fibres impregnated with phenolic resin. A thin layer of nylon film 0.001–0.002in thick provides air impermeability. A layer of metallic film, such as aluminium, may be added to render the wall impermeable and also to reflect heat. The non‐woven material provides space for the inclusion of fire retardants which reduce the rate of heat release to a peak rate of less than 50kw/sq.m and a two‐minute heat release rate of less than 50kw min./sq.m. Also claimed is a reduction of peak and two‐minute release rates of less than 45kw/sq.m and 45kw min/sq.m. Also claimed is a burn length of less than 1.5 inches in 60 seconds and a specific optical density of 75 or less in accordance with the same requirements. It is for use in aircraft cabin structures such as wall and ceiling panelling, air ducting and the like.

Effect of alternative conceptual models in a preliminary performance assessment for the waste isolation pilot plant

The most appropriate conceptual model for performance assessment (PA) at the waste isolation pilot plant (WIPP) is believed to include gas generation resulting from corrosion and microbial action in the repository, and a dual-porosity (matrix and fracture porosity) representation for the solute transport in the Culebra dolomite member of the Rustler formation. Under these assumptions, complementary cumulative distribution functions (CCDFs) which summarize the radionuclide releases to the accessible environment, resulting from both cuttings removal and groundwater transport, fall substantially below the release limits promulgated by the US Environmental Protection Agency (EPA), with the releases being dominated by cuttings removal. To provide additional views, the following alternative conceptual models were considered as part of a preliminary PA for the WIPP: (1) no gas generation in the repository and a dual-porosity transport model in the Culebra; (2) gas generation in the repository and a single-porosity (fracture porosity) transport model in the Culebra; (3) no gas generation in the repository and a single-porosity transport model in the Culebra; (4) gas generation in the repository and a dual-porosity transport model in the Culebra, without chemical retardation; (5) gas generation in the repository, chemical retardation in the Culebra, and extremes of climatic variation. These variations relate to groundwater transport, so do not affect the releases resulting from cuttings removal. Several of these variations substantially increase the importance of releases resulting from groundwater transport relative to releases resulting from cuttings removal. However, the total amount of releases generally remained small, with the CCDFs which summarize the releases to the accessible environment falling below the EPA release limits.

Diffusion and reaction in rock matrix bordering a hyperalkaline fluid-filled fracture

Multicomponent diffusive and advective-dominant transport-reaction calculations are used to analyze water-rock alteration in rock matrix adjacent to a hyperalkaline fluid-filled fracture. The calculations indicate that rock alteration resulting from diffusive transport may be fundamentally different from that observed in the case of advective-dominant transport. Since advective-dominant and diffusive transport can result in differing reaction products as a function of time and space, the two transport processes may modify the chemical and physical properties of the rock at different rates.We apply reactive transport calculations to an analogue of the Cretaceous and Tertiary marls proposed as host rocks for the Swiss low-level nuclear waste repository. Diffusion-reaction calculations predict that the rock matrix bordering high-pH fluid-filled fractures could be completely cemented within 10 to 500 years. The bulk of the porosity reduction occurs because of the precipitation of calcite resulting from the interdiffusion of Ca2+ and CO2−3. In contrast, advective-dominant transport results in the precipitation of calcite only as a replacement of dolomite. Both advective-dominated and diffusive transport result in a porosity increase within millimeters or less of the fracture wall, an effect which could widen the fracture and thus increase the rate of radionuclide transport along the fracture. Because solute diffusion is coupled to porosity and tortuosity change in the rock matrix, cementation causes the fracture to become physically and chemically isolated from the rock matrix if no expansion of the rock occurs. As a consequence, reaction-induced porosity reduction may potentially decrease the buffering and sorbing capacity of a fractured host rock, thus reducing the physical and chemical retardation of contaminants migrating along fractures. These effects may occur within the time required for radionuclides in the repository to decay to environmentally safe levels.

Modeling mineral dissolution and precipitation in dual-porosity fracture-matrix systems

A dual-porosity chemical transport model is applied to saturated fractured porous media. In this model, transport through fractures is advection-dominated while transport within the matrix and between the matrix and the fractures is diffusion-dominated. Recent studies in the literature indicate that conservative tracers and radionuclides in these systems will be retarded by matrix diffusion even in the absence of chemical reactions. This study examines systems that include chemical reactions (e.g., dissolution/precipitation and aqueous complexation) and examines changes in retardation caused by precipitation. The two-dimensional simulation domain consists of a single fracture and the adjacent permeable matrix. The system is modeled using finite differences and a chemical equilibrium simulator based on the Villars-Cruise-Smith algorithm. A constant flow rate is assumed in the fracture, and diffusion rates are functions of the local matrix porosity. Results from simulations with idealized chemistry are presented and discussed to illustrate basic characteristics of this system. These characteristics include both advection-induced and diffusion-induced sequential dissolution/precipitation waves. Results are contrasted with limiting single porosity cases. An additional simulation using the Pitzer activity coefficient model illustrates the chemical retardation of a contaminant due to contaminant precipitation.

Transport Modeling in a Finite Fractured Rock Domain

ABSTRACTThe Waste Isolation Pilot Plant (WIPP) is a U.S. Department of Energy facility intended to demonstrate the safe disposal of transuranic nuclear waste. The WIPP is located in the thick halite beds of the Salado Formation in the Delaware Basin of southeastern New Mexico. Overlying the repository is the Culebra Dolomite Member of the Rustler Formation, a dolomitic unit containing accessory minerals such as calcite, gypsum, and clays. The Culebra is the predominant continuous water-bearing unit in the area. Part of the scientific demonstration of the safety of WIPP involves understanding and estimating what might happen should the WIPP inadvertently be intruded by exploration boreholes long after the WIPP has been decommissioned. Should such a breach occur, it is possible that dissolved transuranic waste could be transported up a borehole and into the Culebra, through which it could eventually reach the accessible environment. The rates and mechanisms for actinide transport in Culebra Dolomite are being investigated as a component of repository performance assessment.The two primary mechanisms for delaying solute release from a double porosity system are called physical and chemical retardation, both of which retard solute migration relative to bulk water flow. Physical retardation occurs when solutes diffuse out of the advective transport regions (fractures) and into diffusive transport regions (matrix). Results of hydrologic field tests suggest that the Culebra behaves as a double porosity medium. Chemical retardation occurs when chemical interactions between dissolved species and mineral surfaces remove solutes from the aqueous phase. Some fracture surfaces in the Culebra are clay-lined, and, because clays can have a large potential for chemical interactions with solutes (e.g., ion exchange or adsorption), it is possible that fracture linings alone may cause significant retardation of any actinides that could reach the Culebra. This report examines these two features in Culebra transport: delimiting the parameter space where a fully two-dimensional model is needed, and examining the importance of clay linings during transport.Numerical simulations with the FMT (Fracture Matrix Transport) finite difference model in a finite, idealized double porosity system were performed to: 1) delineate parameter values for which a set of two coupled one-dimensional equations is insufficient to describe behavior and a fully two-dimensional representation is needed, 2) compare chemical retardation by ion exchange for fractures with and without a clay lining, and 3) compare physical and chemical retardation by ion exchange as a function of fracture velocity. The simulations differ from others in that the matrix is finite, and thus can become saturated with tracers introduced into the domain. The modeling suggests that the chemical retardation caused by clay linings may not be important in a double porosity system. Over a wide range, a single parameter group essentially determines the complexity of the model.

Modeling the Transport of Inorganic Ions Through Undisturbed Soil Columns from Two Contrasting Watersheds

AbstractThe transport of several inorganic cations and anions (i.e., Mg2+ NH+4, Br−, NO−3), via saturated flow, through large undisturbed soil columns from two contrasting watersheds was investigated. The mobility of nonreactive tracers was described well with the convection‐dispersion (CD) equation using flux‐averaged solute detection in the effluent. Reactive tracers were also modeled well using various linear and nonlinear, equilibrium and nonequilibrium, transport codes based on the CD equation. Appropriate independent estimates of model predicted chemical retardation were possible only through experimental development of “dynamic isotherms” using a steady flow method on small undisturbed soil columns. The latter condition can accurately predict solute retardation on large soil columns, since tracer movement is largely controlled by the physical aspects of the soil (e.g., preferential flow zones). Adsorption isotherms generated on disturbed soils using a batch equilibration method, overestimated the amount of solute retardation from displacement experiments on the large undisturbed soil columns. The use of batch adsorption measurements in curve‐fitting transport models to describe data from saturated column displacement experiments on undisturbed soils, may result in erroneous transport parameter estimates.

Water flow and chemical retardation in soils: A simple effective laboratory demonstration

Water flow and chemical retardation in soils: A simple effective laboratory demonstration

BIOMASS AND PHOTOSYNTHESIS RESPONSES OF ROUGH LEMON (Citrus jambhiri Lush.) TO GROWTH REGULATORS

Four-month-old plants of rough lemon (Citrus jambhiri Lush.) were sprayed, once a week, for 7 consecutive weeks with 100-μM concentrations of abscisic acid (ABA), benzyladenine (BA), gibberellic acid (GA3), naphthaleneacetic acid (NAA), and paclobutrazol (PP333). Leaf photosynthetic rates, photosynthetic carboxylating enzymes, and biomass partitioning were determined for individual treatments. Growth of rough lemon was influenced more with sprays of PP333 and GA3 than with ABA, BA, and NAA. PP333 sprays resulted in about 25, 30, and 33% reductions in both plant height and total plant weight, leaf biomass, and leaf area, respectively. The GA3 treatment, which caused 43 and 38% reductions in leaf biomass and leaf area, respectively, induced increased stem height and thickness, resulting in 48% more stem dry weight. There were no apparent differences in leaf photosynthetic rates and activities of ribulose bisphosphate carboxylase between control plants and plants treated with the growth regulators. The activities of phosphoenolpyruvate carboxylase, however, were depressed from 45 to 60% for the BA, GA3, NAA, and PP333 treatments. This suggests that organic acid metabolism in rough lemon leaves would be affected during repeated sprays of growth regulators.Key words: Plant growth, chemical retardants, carbon assimilation, RuBP carboxylase, PEP carboxylase

Transport of Organic Compounds With Saturated Groundwater Flow: Model Development and Parameter Sensitivity

A model which includes the transport and retardation mechanisms of advective flow, axial dispersion, liquid‐phase mass transfer, diffusion into immobile liquid, and local adsorption equilibrium was developed to describe the migration of nondegradable, organic chemicals through a column of saturated, aggregated soil. A range of simplifying assumptions were explored to assess the relative importance of the various mechanisms. Solutions to the model were either adapted from the literature or derived from mass balances and mass transfer principles. The most general form of the model required the development of numerical solutions which employed orthogonal collocation. Soil column breakthrough predictions in terms of relative concentration as a function of total column pore volumes fed can be characterized by seven independent dimensionless parameters: the Peclet number, the Stanton number, a pore diffusion modulus, a surface diffusion modulus, an adsorbed solute distribution ratio, an immobile fluid solute distribution ratio, and the Freundlich parameter 1/n. For a strongly adsorbed chemical in long soil columns, a fifteen fold decrease of the Peclet number, a fivefold decrease of the Stanton number, or a onefold decrease in either the pore diffusion modulus or the surface diffusion modulus have an equivalent effect on the spreading of the breakthrough curve. The breakthrough curve tends to sharpen for favorably adsorbed chemical species (1/n < 1.0) and spread when adsorption is unfavorable (1/n > 1.0). The movement of chemical is retarded as the solute distribution ratios increase. A sensitivity analysis of model parameters, which were derived from literature correlations, column geometry, soil adsorption isotherms, and breakthrough curves, showed that adsorption capacity, adsorption intensity, and aggregate geometry have the greatest effect on chemical retardation and spreading, while liquid‐phase mass transfer has little effect.

Two-dimensional pollutant migration in soils of finite depth

A technique for analyzing two-dimensional migration of contaminant from a landfill into a homogeneous clayey layer is described. The analysis takes acount of the fact that the concentration of contaminant in the landfill will decrease as contaminant is transported into the soil. The analysis also allows for advective–dispersive transport within a permeable stratum (aquifer), which underlies the homogeneous layer. Consideration is given to chemical retardation arising from sorption/desorption of contaminant in the clayey layer. Some of the more important effects arising from the use of a 2-D analysis are illustrated by means of a limited parametric study. It is shown that the diffusion of contaminant from the aquifer into the clayey layer will substantially reduce the concentrations of contaminant in the groundwater away from the landfill. It is also shown that there is a critical velocity in the aquifer at which the maximum concentration at a point occurs. At greater or lesser velocities, significantly smaller concentrations may result. Thus design for limiting velocities is not necessarily conservative. Finally, the results of the 2-D analysis are compared with those from a 1-D analysis and the applicability of 1-D solutions is discussed. Key words: contaminant migration, analysis, soil, diffusion, advection, pollutant.

Crosslinked Acid Gel

Abstract A new, stable, crosslinked acid gel has been developed jar fracture acidizing applications. This crosslinked acid can be prepared from acid strengths up to 28 per cent hydrochloric acid. Laboratory tests show the fluid possesses high viscosity and shear stability at temperatures up to 93 °C(200 °F). Viscosity of the acid gel can be reduced in a controlled manner by a chemical additive to aid well cleanup. Rheological data were obtained in a newly designed Viscometer, the pressure rheometer. The rheometer used a bob/cup arrangement to measure the fluid rheology and the fluid was fed to the gap between the bob and cup. A desired pressure was directly applied to the test fluid without using a second pressurizing fluid such as mineral oil or nitrogen. In addition to its viscosity characteristics, the acid reactivity of the crosslinked acid gel with limestone specimens, in a dynamic reaction setup, is drastically retarded. The crosslinked fluid is also residue free in live or spent acid minimizing formation damage. This newly developed fracture acidizing fluid possesses other important fracturing fluid properties such as low friction pressure, good proppant transport characteristics, and good fluid loss control. Results from computer simulation of fracture acidizing treatments indicate deeper penetration is achieved by the cross- linked acid compared to unaltered acid. Field results also show that in several carbonaceous formations, production could be substantially improved if stimulated with this crosslinked acid. Introduction Hydrochloric acid, ranging in strength from 3 to 28% has been used to commercially stimulate carbonate formations since 1932(1). However, the reaction of HC1 (hydrochloric acid) with carbonate rock occurs too rapidly resulting in a limited depth of penetration of live acid into the formation. In order to increase the depth of penetration, acids have been retarded by: adding a suitable gelling agent(2), adding chemical retarders(3), foaming the acid(4), emulsifying the acid(3), or by crosslinking suitable acid gelling agents(5). Each method of retardation has limited use in field application. With the exception of cross-linked acid, each of these methods generate fluids of low viscosity and a low degree of viscous stability (viscosity changing with time) with increasing reservoir temperature. If hydrochloric acid can be crosslinked to generate high viscosity and better viscous stability then not only will it be possible to retard the acid spending but it will also produce longer and wider fractures. Furthermore, crosslinked fluids normally have lower leakoff rate to the formation during pumping than uncrosslinked fluids. This paper presents a newly formulated crosslinked acid gel developed for fracture acidizing. Rheology, acid reaction rate, fluid loss, friction pressure and sand fall data obtained from laboratory studies will be presented. Results obtained from field application of this crosslinked acid will also be presented. The Crosslinked Acid System Crosslinked acid was formulated to be easily mixed on the well site. The system is similar to other commercial crosslinked water-based fracturing fluids commonly used for hydraulic fracturing.

The chemical retardation of grass growth

Interest in plant growth regulators is mainly concerned with general or selective stimulation of growth. This is largely true of grass but there are large areas of grassland–-some 9.2 million ha in the United States alone–-where growth has to be controlled for amenity reasons: examples are parks, golf courses, roadside and railway verges, and industrial estates. The rising cost of fuel and labour for mowing favours the development of chemical agents for this purpose. This article reviews progress in this field, with special reference to mefluidide.

Basalt as a Potential Waste Package Backfill Component in a Repository Located Within the Columbia River Basalt

The two major functions of a backfill are considered to be the exclusion of water from the waste package and chemical retardation of radionuclide migration. Preliminary experiments were conducted with Umtanum basalt, water, and various waste forms including simulated spent fuel, supercalcine, and borosilicate glass to determine the feasibility of using basalt as a potential backfill component. Basalt is being evaluated principally as a chemical barrier. Experiments done in the temperature range of 100 to 300/sup 0/C with only waste form and water show nearly complete dissolution of cesium, rubidium, and molybdenum. However, in parallel experiments, where basalt was added to the system, cesium, rubidium, strontium, and molybdenum were almost completely removed from solution. Analyses of solid run products indicate the formation of pollucite ((Cs,Rb,Na)AlSi/sub 2/O/sub 6/ . H/sub 2/O) and powellite (CaMoO/sub 4/). It is suggested that the glass component of the basalt reacts to form the stable solid phases that fix these elements. Also, rubidium is likely to follow cesium into a plagioclase structure and strontium may be found in plagioclase or powellite. Thus, given the ready availability and reactive nature of basalt, it is a recommended candidate backfill material for use at the Hanford Site.

Crosslinked High-Strength Hydrochloric Acid Gel System Rock Mountain Case Histories

Summary A recently developed high-strength crosslinked acid system involving hydrochloric acid (HCl) concentrations of 0.25 to 28% has been used in acidizing a variety of limestone and dolomite formations throughout the Rocky Mountain region. The specialized chemistry of the crosslinked acid polymer in HCl solution as well as the resultant clay stabilizing properties after the acid reacts are noted.Case histories of the well treatments using high-strength crosslinked HCl are presented along with production history before and after the cross-linked acid production history before and after the cross-linked acid jobs. Data on more than 45 crosslinked acid jobs are presented. Some older wells treated with the crosslinked presented. Some older wells treated with the crosslinked acid averaged a two- to sixfold oil production increase, whereas the potential of new wells was much greater than expected after the treatment was compared with neighboring wells treated conventionally, and production usually has been more sustained. production usually has been more sustained. Introduction The technique of acidizing oil and gas wells is a well-known technology. The process of dissolving soluble carbonate or dolomitic rock has been employed since 1938. The technique of gelling HCl to control fluid loss and to prevent it from reacting during pumping is not new; however, the degradation of the gel by the acid has caused the system to be less efficient than anticipated. The crosslinked acid system overcomes the disadvantages of the gelled acid and allows HCl to be pumped, live and strong, farther into the formation than any previously designed system. previously designed system. The effectiveness of the acid treatment is determined by the degree of formation conductivity achieved. The conductivity between the wellbore and the reservoir depends primarily on the depth of penetration of live acid. The acid can be kept live away from the wellbore by retardation of the acid reaction on the formation. Various techniques and compositions are known for retardation: chemical retardation, acid/oil emulsion, foaming, hybrid acids, gelling, the use of alternate stages of pad and acid, etc. All these techniques provide retardation, but by the time acid reaches the provide retardation, but by the time acid reaches the tip of penetration, the concentration of the acid is reduced considerably or the acid is completely spent. However, the unbroken crosslinked HCl acid maintains nearly the same acid concentration at the tip of the penetration as at the wellbore. penetration as at the wellbore. The shear stability and high viscosity of the crosslinked acid are advantageous to fracture-acidizing operations because the acid produces wider and longer fractures in low-permeability limestone and dolomite formations.Laboratory tests indicate the effective retardation for wells having a bottomhole temperature (BHT) up to 350F. Since the stability of the system decreases with the increase in temperature and acid concentration, it is suggested that for high-BHT wells, a suitable preflush to cool the formation be incorporated in the treatment design. By selection of the appropriate polymer concentration and crosslinker quantity according to the BHT and the strength of the HCl acid to be used for the job, the desired viscosities may be obtained. The crosslinked acid system breaks down with time and temperature, as a practically residue-free live acid of less than 7- to 10-cp practically residue-free live acid of less than 7- to 10-cp viscosity to react with the formation. The system is compatible with various additives used in the acid, such as corrosion inhibitors, surfactants, sequestering agents, and suspending agents. However, some of these additives are not compatible and they should be used only after their compatibility is determined in a prejob laboratory test.The experimental data on the crosslinked acid stability, inhibiting clay swelling, sand suspension tests, reaction rate data, rheology data, fluid loss data, etc. have been published in recent literature. JPT p. 2080

Allelopathic Potential of Clerodendrum viscosum Vent. in Relation to Germination and Seedling Growth of Weeds

The activity of decaying plant-parts of Clerodendrum Viscosum and field soils collected beneath Clerodendrum plants have been studied on the seed germination and root and hypocotyl growth of five weeds, viz. Abutilon indicum, Amaranthus spinos, Cassia Sophera, C. tora and Tephrosia hamiltonii . Germination inhibitions are almost uniform in soil samples of both July and December, although the root and hypocotyl growth of A. spinosus is adversely affected by the December soil collection and similar growth of Abutilon indicum and T. hamiltonii strongly inhibited by underground soils of the season. Decaying roots seem to be most inhibitory among the three plant-parts. While no inhibition to A. indicum and C. tora results from mixing decaying leaves and stems with soil, there is inhibition to C. Sophera from the admixture of either plant material and T. hamiltonii from leaf/soil mixture and not stem/soil mixture. As the leaves of Clerodendrum form the most consistent source of the natural chemical retardant, these are analysed and the presence of a terpene compound (clerodin) has been suspected in carrying out the allelopathic effect.

Chemical Retardation of Bermudagrass Turf1

AbstractLittle information is available on the influence of chemical growth regulators on warm season perennial turf grasses. Therefore, greenhouse and field experiments were conducted to evaluate several such compounds for their potential in retarding the growth of common and ‘Sunturf’ bermudagrass [Cynodon dactylon (L.) Pers]. Maleic hydrazide [ 1,2‐dihydro‐3,6 pyridazinedione (MH)] and chlorflurenol [Methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate (CF)] injured both types when applied at 4.5 or 3.4 kg/ha in the greenhouse. Ethephon (2‐chloro‐ethylphosphonic acid) stimulated stem elongation of both bermudagrasses when applied at rates below 6.7 kg/ha in the greenhouse, while higher concentration retarded their growth in the field. Greenhouse plants grown under a wet regime (watered daily) showed no significant difference in chemical retardant effects on plant top growth and internode length from those grown under a dry (watered every three days) regime. Although more plant growth did occur in wet regimes, the growth retardation effect by the chemicals was not nullified by such conditions. Common bermudagrass was less susceptible to injury than Sunturf in the greenhouse, and no significant retardation of Sunturf top growth was obtained in the field. Fluoridamid (N[3‐[(1,1,1‐trifluoromethylsulfonyl) amino]4‐methylphenyl]acetamide), MBR 12325 (N‐[2,4dimethyl‐5‐[ trifluoro‐methyl)‐sulfonyl] ‐amino]‐phenyl acetamide), MH, CF, and ethephon were effective in reducing bermudagrass vegetative growth and seedhead development in the field. Single high rates of these compounds frequently caused bermudagrass injury, while split applications or chemical combinations at low rates provided excellent growth retardation with no undesirable turf appearance.

Chemical Regulation of Grass Growth. I. Field and Greenhouse Studies with Tall Fescue1

AbstractGrowth control of grass and other vegetation has been achieved on a limited scale by the use of chemical retardants on highway roadbanks and similar rough turfgrass areas. A few chemical growth retardants are available commercially and a number of experimental chemicals have been developed recently. Five greenhouse experiments and four field studies were conducted from 1970 to 1972 at Southern Illinois University to evaluate commercial and experimental chemical retardants on ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.), one of the leading grasses used in Illinois for roadbank stabilization. Nineteen chemicals or formulations were tested with potted tall fescue in the greenhouse and several rates of eight different chemicals were evaluated under field conditions. On selected dates after treatment, grass plots were evaluated as to height, color maintenance, stand losses, and weed infestations.In greenhouse trials the most promising results were obtained with Slo‐Gro, a maleic hydrazide (MH) formulation [diethanolamine salt of 6‐hydroxy‐3‐(2H)‐pyridazinone]; MON‐820 (N‐phosphonomethylimino‐diacetic acid); MON‐845 [N,N‐Bis(phosphonomethyl)glycine]; MBR‐6033 (3‐trifluoromethyl‐ sulfonamido‐p‐acetotoluidide); and Maintain CF‐125 (methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate, methyl‐9‐hydroxyfluorene‐9‐carboxylate, methyl‐2, 7 dichloro‐9‐hydroxyfiuorene‐9‐carboxylate). MBR‐6033 showed considerable potential in providing balanced control of growth while enhancing or maintaining a desirable green color. Sustaining color was difficult with other chemicals evaluated when used at rates sufficient to reduce growth over a long time interval.MON‐820, MON‐845, Slo‐Gro (MH), and Maintain CF‐125 reduced grass growth and dry matter yield markedly at selected rates in field studies. However, color deterioration, stand reduction, and weed infestation were serious at higher chemical rates. MON‐814 (ethanolamine‐p‐nitrobenzene‐sulfonylurea), MON‐139 (phosphonomethylglycine, isopropyl‐ammonium salt), and MON‐464 (phosphonomethylglycine, calcium salt) were less consistent in reducing growth while sustaining color. Slo‐Gro, MBR‐6033, and Maintain CF‐125 effectively suppressed tall fescue seedhead development.Information gained from these studies indicates that treatment with selected commercial and experimental growth retardant chemicals can result in effective tall fescue growth control and seedhead suppression. In some instances, chemical treatment of grass resulted in some degree of phytotoxicity and grass color losses. A notable exception was treatment with MBR‐6033 (Sustar), which gave good growth control while maintaining or enhancing grass color.

Chemical Regulation of Grass Growth. II. Greenhouse and Field Studies with Intensively Managedd Turfgrasses1

AbstractChemical growth retardant treatments have been used on a limited scale to decrease vegetative growth and reduce mowing maintenance requirements of turfgrasses. A number of experimental chemical retardants have been developed recently. Three greenhouse experiments and five field studies were conducted from 1970 to 1972 at Southern Illinois University to evaluate experimental and commercial chemical growth retardants on several species and varieties of intensively managed turfgrass. Seven chemical retardants were tested in the greenhouse with potted Kentucky bluegrass (Poa pratensis L.) and in field studies with Kentucky bluegrass and other species. Treated grasses were evaluated weekly as to growth reduction, and on selected dates as to color maintenance, stand losses, and weed infestations.MON‐820 (N‐phosphonomethylimini‐diacetic acid) retarded growth of Kentucky bluegrass more than Slo‐Gro (diethanolamine salt of 6‐hydroxy‐3‐(2H)‐pyridazinone; maleic hydrazide or MH). However, losses of the green color often were greater with MON‐820 treatments than with MH treatments. The responses of MBR‐6033 (3‐trifluoromethyl‐sulfonamido‐p‐acetotoluidide) and MON‐845 [N,N‐Bis (phosphonomethyl) glycine] were similar to those of MON‐820 and MH. MON‐139 (phosphonomethylglycine, isopropylammonium salt) and MON‐464 (phosphonomethylglycine, calcium salt) were phytotoxic and caused pronounced color losses and grass stand reductions. High rates of C‐19490 (chemical configuration not released by CIBA GEIGY Corp.) were required to retard grass growth.Pronounced color losses of the grass, serious stand reductions, and resulting weed infestations occured after use of higher rates of several chemicals. A concurrent herbicide application may be necessary to control weeds in Kentucky bluegrass plots treated with certain growth retardants.Residual chemical‐retarding effects were noted in autumn‐treated plots when they were evaluated in early spring of the next year. However, few effects were observed in autumn evaluations of spring‐treated plots.MON‐820 treatments evoked marked growth reduction of a number of Kentucky bluegrass varieties and with varieties of tall fescue (Festuca arundinacea Schreb.), bermudagrass (Cynodon dactylon L.), and zoysiagrass (Zoysia japonica Steud.). Differential varietal and species responses were noted with a given rate of MON‐820. These responses complicate the process of recommending a general chemical rate for a wide array of turfgrasses.Most experimental and commercial growth retardants tested showed some degree of phytotoxicity on several intensively managed turfgrasses. Their use would be more useful on rough turfgrass areas such as highway roadbanks than on home lawns and similar areas.