Research bulletins abstracts 151 through 175
Bulletin 151
Abstract: A rainfall simulator was used to evaluate the effectiveness of vegetative filter strips for the removal of sediment and phosphorus from feedlot runoff. Simulated rainfall was applied to nine experimental field plots with a 5.5 m by 18.3m bare source area (simulated feedlot) and either a 0, 4.6m or 9.1m filter located at the lower end of each plot. Fresh dairy manure was applied and compacted into the bare portions of the plots at rates of 7,500 kg/ha and 15,000 kg/ha. Water samples were collected from the base of each plot and analyzed for sediment and nutrient content. One set of plots was constructed so that flow through the filters was concentrated rather than shallow and uniform. The 9.1m and 4.6m vegetative filter strips with shallow uniform flow removed 91 percent and 81 percent of the incoming suspended solids, and 69 percent and 58 percent of the incoming phosphorus, respectively. Soluble phosphorus in the filter effluent was sometimes greater than the incoming soluble phosphorus load, presumably due to lower removal efficiencies for soluble phosphorus and the release of phosphorus previously trapped in the filters. Vegetative filters with concentrated flow were much less effective than the shallow uniform flow plots, removing 40 percent to 60 percent less sediment and 70 percent to 95 percent less phosphorus than plots characterized by shallow uniform flow. Observation of existing filter strips on cropland found that in filter strips were not likely to be as effective as the experimental field plots because of problems with flow concentration.
Bulletin 152
Abstract: Reliable methods are urgently needed for recommending minimum instream flows to protect aquatic life. For statewide or basinwide planning purposes simple methods which require little or no field investigations are required. We applied the instream flow incremental methodology (IFIM) on four streams in the Upper James River Basin using nine target fish species in the analyses. Flows which optimize habitat for these target species were identified for four seasons. Flow recommendations were also developed using IFIM for meeting lower habitat maintenance objectives. The recommended flows for a given habitat maintenance objective increased with increased stream size but the rate of increase was not constant; lower proportions of average discharge were required to maintain optimum habitat as stream size increased. Equations are presented for applying these results to develop flow recommendations for other streams in the Upper James River Basin based on the average discharge.
Bulletin 153
Abstract: Vegetative filter strips (VFS) on 33 Virginia farms were visited and observed over a 13 month period to evaluate their long term effectiveness for water quality improvement. Operational problems observed during the site visits were documented and design or maintenance procedures to alleviate the problems were evaluated. Of the VFS observed, 36% were judged to be totally ineffective, were no longer in existence, or were simply extensions of pastures although all were, or had been, part of the state cost share program. Most of the sites visited had topographic limitations which severely limited VFS performance. Accumulation of surface runoff in natural drainageways within fields before it reached the VFS was the most common and critical problem. Runoff from the drainage ways crossed the VFS in a few narrow areas, totally inundating the filters and rendering them ineffective for sediment and nutrient reduction. This situation is difficult to control and VFS are probably not appropriate for fields with extensive internal drainageways unless the VFS extend up into the fields and parallel the drainageways forming wide grassed waterways. Vegetative filter strips were judged to be beneficial even when they could not filter sediments and nutrients from runoff because they provided localized erosion protection in critical areas along streambanks. They did not act as filters, however, and should therefore be referred to as vegetative buffer strips or critical area plantings.
Bulletin 154
Abstract: Research was conducted during 1984 and 1985 to determine Cd, Cu, N, Ni, P and Zn availabilities to barley (Hordeum vulgare L.) and corn (Zea mays) grown om four sludge amended soils. Field studies were conducted on Acredale silt loam (Typic Ochraqualf), Bojac loamy sand (Typic Hapludult), Davidson clay loam (Rhodic Paleudult), and Groseclose silt loam (Typic Hapludult). An aerobically digested sewage sludge, which was dewatered for approximately 2 years on sandbeds, was obtained from a sewage treatment plant with major industrial inputs. In the spring of 1984, this sludge was applied at rates of 0, 42, and 84 dry Mg/ha to the poorly drained Acredale soil and at rates of 0, 42, 84, 126, 168, and 210 dry Mg/ha to the well drained Bojac, Davidson, and Groseclose soils. The 210 dry Mg/ha sludge rate supplied 4.5 kg Cd, 750 kg Cu, 3350 kg N, 43 kg Ni, 6900 kg P, and 600 kg Zn/ha. A 14 day anaerobic N incubation study indicated that mineralization of sludge organic N varied from 9.2 % at the 42 Mg/ha sludge to 4.2% at the 210 Mg/ha rate. This relatively low percentage of N mineralized from the sludge may reflect the inhibitory effects of the high sludge metal levels on N transformations and the changes in sludge composition during long term dewatering on sandbeds. Sludge application increased crop yields, except where the amounts of N mineralized from the sludge was inadequate to supply the N requirement of the crop. Crop yields were not decreased by either metal phytotoxicity or P deficiency on the four sludge amended soils. On the three well drained soils, Cu and Zn phytotoxicity did not occur where these metals were applied in excess of USEPA guidelines of 280 kg Cu and 560 kg Zn/ha. Although there were increases in Cd, Cu, Ni, and Zn in plants grown on the sludge amended soils, the metal concentrations were within the ranges of those reported for nonsludged soils. Levels of DTPA extractable metals in the Ap horizon of the soils provided a good indication of the amounts of metals in the soils from sludge application. Relatively low correlations occurred between DTPA extractable Cd, Cu, Ni, and Zn and the respective metal concentrations in plant tissue. These low correlations were attributed to the small increases in metal concentrations in tissue from metals supplied by sludge application. The DTPA extractable Cd, Cu, Ni, and Zn concentrations in soils sampled from various depths indicated no downward movement ofthose metals in the sludge amended soils, except for virtually negligible downward movement of Cu in the Groseclose soil. Dilute double acid extractable P in these samples indicated a small amount of P movement in only the sludge amended Bojac and Davidson soils. The limited N mineralization of the sludge under study substantially reduced the potential for No(3) contamination of groundwater.
Bulletin 155
Abstract: Contamination of soils at toxic and hazardous waste sites can adversely affect groundwater and surface water. Water soluble materials can move in soil by leaching and percolation and by runoff. This project evaluated the toxicity of leachable toxicants from seven soils, five of which were obtained from designated toxic or hazardous waste sites. Acidified, dechlorinated tap water was used to extract toxic materials from surface soils. Extracts were used as complex mixtures in acute toxicity tests using Daphnia and in chronic effect tests using microcosms. Three classes of effects were observed. Some leachates (including control soils) showed no toxicity. Some soil leachates had moderate acute toxicity (50 80% diluted leachate) and no chronic toxicity. Very toxic soils showed both acute and chronic toxicity at less than 3% leachate. Toxicological evaluations of contaminants in waste site soils can provide information not available from chemical analyses and may be useful in verifying the effectiveness of cleanup effort.
Bulletin 156
Abstract: This study was designed to evaluate the performance of current formulations of three types of laundry detergents in soft (60 ppm) and hard (172 ppm) water using home laundry equipment. Standard loads were washed with two brands from each of three types of detergents (phosphate built and carbonate built granular, and unbuilt liquid) to measure soil removal, soil deposition, and carbonate deposition. For the 5 replications of the soil removal test, swatches of soiled test cloth in 100% cotton, 50% cotton/50% polyester with no finish, and 50% cotton/50% polyester with permanent press finish were used. Untreated swatches of the same fabrics were used for the 10 replications of the soil deposition and soil was introduced via a solution of Bandy black research clay and hot water. Swatches of the test cloth were attached to items in the test load. Carbonate deposition was observed after 5, 10, and 15 washings of a load composed of nine dark blue items (three 100% cotton terry washcloths, three men's 100% cotton T shirts, and three boy's 50% cotton/50% polyester sport shirts) plus sufficient filler clothes of unbleached muslin to complete the load. Numerous significant interactions indicate that the results are not clear cut. However, the following conclusions were reached. The unbuilt liquid detergent was most effective in soil removal, especially in hard water, and the carbonate built granular product was the least effective. The phosphate detergent was the best of the three types in holding soil in suspension. Soil deposition increased with the number of washings and the increase was greater in hard water than in soft water. The appearance of "tattletale gray", which results as suspended soil is deposited on fabrics, was most noticeable for fabrics of untreated 100% cotton. Carbonate deposition was more apparent in hard water than in soft, but the buildup of the white precipitate occurred in both soft and hard water. Deposition of the carbonate precipitate was progressive and occurred at a faster rate in hard water than in soft. Items washed in hard water felt harsher than those washed in soft water, and the presence of the precipitate was more noticeable in areas with irregular surface texture or thickness. Detergent formulations change frequently and the differences in detergent types are becoming increasingly blurred. Therefore, when purchasing and using laundry detergents, consumers need to be aware of the properties of their water supply, laundry detergent, and washing machine, plus the articles to be washed, including types of soil. Laundering clothes is a complex process; satisfactory results depend on appropriate combinations of variables in the laundry system. At present, unbuilt liquid products are a practical and effective alternative to phosphate built laundry detergents.
Bulletin 157
Abstract: A rainfall simulator was used to study the effectiveness of three best management practices no till, residue level and fertilizer application technique for reducing sediment, phosphorus, and pesticide losses from agricultural lands. Simulated rainfall was applied to 12 experimental field plots, each 0.01 ha in size. The plots were divided into conventional and no till systems. During phase I, the effectiveness of two fertilizer methods subsurface injection and surface application were investigated for the two tillage systems. In phase II, three crop residue levels 0, 750, and 1500 kg/ha were studied within each tillage system. Granular fertilizer was applied 24 to 48 hours before the start of rain simulation. Water samples were collected from the base of each plot and analyzed for sediment, nutrient, and pesticide content. No till was found to be very effective in reducing runoff and sediment losses. No till with high residue level produced the greatest reductions in runoff and sediment losses, and the highest reduction for both runoff and sediment occurred with no till and 1500 kg/ha crop residue level. No till reduced sediment loss by 98% and total runoff volume by 92%. The injection fertilization method reduced OP losses by 39% for no till and 35% for conventional tillage. Reductions in TP losses due to no till practice were 89% and 91% for surface and injection fertilizer application methods, respectively, compared to the conventional system. Averaged across all fertilizer treatments, an equivalent of 0.9% and 8.9% of the total P fertilizer applied to the plots was lost from no till and conventional tillage plots, respectively. Concentrations of atrazine and 2,4 D in runoff and sediment were greater from the no till plots than from the conventional plots, but total losses were less. Water was the major carrier for both herbicides, although the concentration of 2,4 D in sediment was higher than that of water. Averaged over all plots, the atrazine losses were 2.9% of the applied amount for conventional tillage and 0.3% for no till. The corresponding values for 2,4D were 0.3% ad 0.02%.
Bulletin 158
Abstract: Recognition of the importance of nonpoint source (NPS) pollution to water quality has required broadening of Virginia's water quality management program. Although the state had adopted a voluntary program of best management practices and has implemented a cost sharing program to encourage NPS control in parts of the state, much of the authority to impose land use controls as a management strategy continues to rest with local governments. Because of recent development of concern for NPS management, effectiveness of the existing institutional framework has not been established; this study provides a preliminary assessment. It analyzes the relationship between the different levels of government in the area of land use control, presents the results of case studies of local program implementation, describes alternative institutional arrangements for NPS management as employed in other states, and presents recommendations for modifications to enhance the state's ability to address the problem. Recommended changes focus on strengthening local land use controls to achieve environmental protection goals and increasing state oversight capabilities to ensure adequate control of NPS pollution occuring across local political boundaries. Implementation of institutional changes must be coordinated with expanded federal involvement in stormwater management and NPS pollution control. Since recent changes in federal requirements provide for increased state control (subject to federal approval), the recommended changes to the state's NPS management program are generally consistent with federal institutional changes.
Bulletin 159
Abstract: The Illinois Drainage Area Simulator (ILLUDAS) has been modified for continuous simulation and a water quality module has been added to it. The continuous simulation model updates the Antecedent Moisture Condition (AMC) based on the rainfall information up to 120 hours prior to the beginning of a storm and the information on the number of dry days between storms is utilized to compute the pollutant build-up which also depends on the street sweeping interval. The water quality module utilizes the dust and dirt method of STORM to compute pollutant accumulated on the watershed surface. Pollutant washoff is then computed based on the assumption of first-order kinetics. Features have been added to simulate the effect of BMP structures. Infiltration trenches and detention ponds have been considered in this study. An optimization scheme has been adopted to optimally size and locate the detention structures within the watershed. The model has been verified using the observed data from the Upper Holmes Run Watershed in Northern Virginia, and a hypothetical watershed, basin Alpha, originally described in ILLUDAS. An institutional framework for urban stormwater management is delineated. The role of federal, state, and local agencies in urban stormwater management is discussed.
Bulletin 160
Abstract: Alternative technologies are examined for the disposal of disused underground storage tanks that once contained petroleum products or other hazardous chemicals and the effects of hazardous waste laws on disposal are discussed. Disposal options for the large population of old vessels are considered in terms of currently required and available technologies, the benefits and problems associated with various strategies, and the means available to a tankowner for utilizing these options through either a full or partial contracting of commercial services. Actual disposal costs charged by firms offering the service in or near Virginia are compared and the environmental impacts associated with cleaning wastes and tanks discarded according to each strategy are addressed. Additional information about pertinent regulations and the characteristics of the national UST population are provided in the Appendices.
Bulletin 161
Abstract: Under the provisions of recent federal and state legislation, the owners and operators of underground storage tanks containing petroleum products are required to maintain evidence of financial responsibility. The requirements as they presently stand, different ways of meeting them, and associated issues are examined. The regulated community is described as well as proposed financial responsibility regulations under RCRA Title I, their relevance to the situation in Virginia and to any state regulatory initiatives, and a suggested set of criteria for judging these initiatives. The next section describes allowable financial responsibility assurance mechanisms, and reviews the advantages and disadvantages associated with each. A critique follows of financial responsibility legislation recently enacted In Virginia. Conclusions and recommendations are intended to assist state decision makers in designing and implementing an effective set of financial responsibility regulations for underground storage tanks.
Bulletin 162
Abstract: A rainfall simulator was used to study the effects of tillage system and sludge application method and rate on runoff, sediment, phosphorus (P), and nitrogen (N) losses from agricultural lands. Surface application and incorporation of sludge were studied. Anaerobically digested sewage sludge was applied at rates supplying 0, 75, and 150 kg/ha of plant-available N. These rates resulted in applications of 0, 115, and 230 kgP/ha, respectively. A total of 90 mm of rainfall, with an intensity of 40-45 mm/hr, was applied to sixteen 0.01 ha plots, on a silt loam soil. Runoff water samples were collected from plot discharge and later analyzed for sediment and nutrient contents. No-till was found to be effective in reducing runoff and sediment losses. Runoff and sediment losses decreased as sludge application rates increased, regardless of the tilage system. The surface application of sludge was more effective in reducing sediment losses than sludge incorporation. Nutrient concentations and yields were greater from conventional tillage plots than from no-till plots. Surface application of sludge to conventional tillage plots resulted in higher concentrations and yields of most forms of P and N, relative to incorporated sludge treatments. Sediment-bpund and total-P yields were less from sludge-runoff as a result of sludge application. With respect to sediment and nutrient yields in surface runoff, no-till appears to be a safer alternative for disposal of sewage sludge than conventional tillage.
Bulletin 163
Abstract: Urbanization increases peak flow and total volume of surface runoff as compared to predeveloped conditions. Infiltration trenches in unsaturated soil, one of the best management practices employed to control excessive runoff in urban areas, are examined in this report. A two-dimensional finite element model has been developed to simulate the transient flow in a variable saturated porous medium. Parameters such as soil properties, water table location, initial soil moisture condition, trench geometry, and surface runoff hydrograph at the facility site are specified, and routing is performed to find infiltration rate, water depth and storage in the trench, and overflow, if any. A laboratory model also has been used to test the validity of the finite element model for loam soil and sandy loam to determine the various effects of such parameters. Sands are recommended for use in an infiltration facility while clays are not. Saturated soil conductivity and the (Lambda) parameter from van Genuchten's model are found to have the greatest effect on infiltration rate. Where geometry is concerned, a wide, shallow trench is recommended for a given trench length and trench volume. The depth of the water table has been shown to have a greater effect in silt than in sand. There exists a limit for each soil beyond which the water table has no effect on infiltration. The limit is about 10 feet for sand, 30 feet for loamy sand, and 60 feet for sandy loam. In the design of an infiltration trench, geometries vary considerably and water depth in the trench varies with time. The water flux across the bottom and sides of the trench is an important factor in sizing the trench. The finite element model has the capability to change geometries and to calculate the flux and water level in the trench. It is a useful tool in the design of infiltration facilities.
Bulletin 164
Abstract: Nonpoint source pollution from agricultural areas is a major water quality concern in the rivers, lakes and estuaries of Virginia. It has also been identified as a major problem in the Chesapeake Bay with the Environmental Protection Agency estimating that agricultural nonpoint sources account for 40 to 70 percent of the phosphorus and nitrogen loading to the bay. To address this problem, the use of conservation tillage and other best management practices (BMPs) is being promoted in Virginia. In fact, a state cost-sharing program has been implemented to encourage farmers to install BMPs specifically for water quality improvement. Since funds are severely limited, it is essential that some mechanism be developed to target cost-sharing funds to the farms and fields which have the most significant impact on downstream water quality. This will greatly improve the cost effectiveness of the program and would result in far greater water quality improvements. One possible means for targeting BMPs is identifying the portions of watersheds that are responsible for generating runoff since runoff is the primary transport vehicle for pollutants from watersheds. A general methodology has been developed to identify the critical areas within a watershed that contribute to surface and subsurface runoff and thus to pollutant transport. The surface runoff is viewed as an extension of the surface saturation process which occurs because of the soil's inability to transmit subsurface flow further downstream. The subsurface flow emerging to the surface (return flow), combined with rainfall, generates the surface runoff. In the absence of surface saturation, no surface runoff is generated but subsurface flow may still contribute to runoff. The methodology was applied to Pony Mountain Branch watershed in Virginia. It was found that subsurface flow does account for a significant part of total runoff. The critical areas were identified based on their relative contributions to total runoff production. To account for its variability, hydraulic conductivity was treated as a lognormally distributed random variable. A Monte Carlo simulation procedure was adopted to compute water content values for varying hydraulic conductivities. The saturated water content values at different times decide the expansion and contraction of critical areas. The mean growth pattern for the critical areas from the simulations was adopted as the required critical region. It is also found that deterministic simulation may not be representative of the critical area growth pattern where large standard deviations in hydraulic conductivity occur.
Bulletin 165
Abstract: The purpose of this research was to evaluate the rates, patterns, and pathways involved in the biodegradation of organic contaminants in subsurface environments. Subsurface material was obtained from several sites representing diverse environmental conditions. The overall goal was to gain a general understanding of biodegradative mechanisms rather thanmaking site-specific measurements. The biodegradation rates of methanol, phenol, and t-butanol (TBA) were evaluated in static soil/water microcosms. Biodegradation assays were conducted under ambient anoxic conditions, and with the addition of potential electron acceptors ( nitrate, nitrite, sulfate) or metabolic inhibitors (molybdate, BESA) to promote different pathways of anaerobic microbial metabolism (nitrate respiration/denitrification, sulfate reduction, or methanogenesis). In unamended systems, biodegradation rates varied considerably between sites. Methanol and phenol were degraded fairly readily. Rates generally ranged from 0.5 to 1.0 mgl(1) d(1) for 20 degrees C incubation. Disappearance of methanol and phenol followed zero-to-first-order kinetics and was usually immediate requiring no acclimation period. TBA was relatively recalcitrant in subsurface soils, disappearing at a rate of of 0.1-0.3 mgl(1) d(1) (20 degrees C). No biodegradation was evident_relative to sterile controls, incertain soils. The pattern of TBA degradation was typically biphasic: a long lag period of slow, linear removal was followed by an abrupt increase in removal rate (albeit still slow). Biodegration rates were positively correlated with bacterial density for 12 soil samples from 3 sites within a localized area at Blacksburg, Virginia. However, this relationship did not exist between soils from diverse locations. The prevailing electron acceptor conditions govern the catabolic pathways utilized in the anarobic respiration of organic contaminants. The effects of the added electron acceptors and inhibitors on biodegradation rates varied between sites. Two general types of systems are indicated by relative biodegradation rates, characteristic responses to electron acceptor/inhibitor amendments, and general environmental conditions. "Fast" soils are characterized by a higher flux of water and nutrients, higher biodegradation rates, and rate enhancement upon adding nitrate or sulfate.. In "slow" soils, organic contaminanats are degraded at lower rates, rates are decreased by adding nitrare, sulfate, or BESA (which inhibits methanogenesis), and rates are increased by adding molybaste (which inhibits sulfate reduction). Nearly all soils tested were capable of sulfate-reducing and methanogenic metabolism, but those populations were more active, and competition between the two groups was less severe, in "fast" soils. In contrast, "fast" soils appeared to harbor an active population of nitrate respirating/denitrifying bacteria, whereas in "slow" soils that metabolic group was inactive, or susceptible to toxicity.
Bulletin 166
Abstract: The current U.S. Environmental Protection Agency (EPA) method for analysis of organic chemicals and metals leached from solid waste is the Extraction Procedure (EP) Toxicity Test. Due to limitations of the EP, the EPA has developed and plans to implement the Toxicity Characteristic Leaching Procedure (TCLP), which is capable of analyzing more organics, including volatile organic chemicals. This research investigated the ability of the EP and TCLP test procedures to quantitatively recover added surrogate standards and qualitatively identify trace organic chemicals in domestic wastewater sludges. Sludges from three (approximately 1 MGD) municipal wastewater treatment plants that land apply their sludges were analyzed. Recoveries of surrogate standards were low and highly variable for both tests. There was no statistically significant difference between the TCLP and EP tests with respect to recovery of any semivolatile or nonvolatile surrogate standard added to the sludges. The mean recovery of the volatile surrogate standards by the TCLP was slightly better than by the EP. Sample site (wastewater treatment plant) exhibited a more statistically significant impact on recovery of the individual sludge surrogates than did test, i.e., TCLP and EP. No distinct relationship could be established between certain physical/chemical characteristics of the surrogates and recovery at a particular treatment plant.
Bulletin 167
Abstract: Research was conducted in soils of the Chesapeake Bay area to determine the effects of tillage practice and nitrogen (N) fertilizer application rates on N leaching from corn fields. Three well known computer models (NTRM, CERESMaize, and VTMAIZE) were tested to determine their ability to predict the distribution of N in (a) soil and crop, (b) the components of the N cycle, and (c) corn yields. To accomplish the above objectives, two field sites were selected on agronomically important soils for either a corn (Zea mays L.)wheat (Triticum aestivum L.)soybean (Glycine max [L.] Merr.) or a continuouscorn rotation. The cornwheatsoybean rotation was lcoated on a Suffolk sandy loam soil (coarse loamy, siliceous, thermic Typic Hapludult) in the immediate Chesapeake Bay drainage basin. The continuouscorn rotation was located on a Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludult) typical of finertextured soils located in the upper reaches of tributaries that drain into the Chesapeake Bay. Management practices evaluated included tillage system and rate, source, and time of N application. Specifically, we looked at conventional vs. notill; inorganic N vs. sewage sludge; preplant vs. split application of N; and a variety of N application rates. The N treatments for corn were 0, 75, 150, and 225 kg N / ha applied preplant; 150 kg N / ha applied 4 weeks after emergence; and 150 kg of mineralizable N / ha from anaerobically digested and either lime or polymerconditioned sewage sludge. The N treatments for wheat were 20 kg N / ha applied in the fall and 30, 60, or 90 kg N / ha applied in the spring; 60 kg N / ha split application; and 80 kg of mineralizable N / ha applied in the fall from either lime or polymerconditioned sewage sludge. In the Groseclose soil, there was an increase in total yield and N uptake when sewage sludge was applied compared to the split and preplant application of inorganic N. There was no difference between polymer or limeconditioned sewage sludge application. Also, there were no differences between preplant and split application of N. Where notill was used, there was an increase in both yield and N uptake compared with conventional till. In the Suffolk soil, tillage management did not influence yield or N uptake where time and source of N application were studied. This lack of response on the Suffolk soil is attributed to severe moisture deficits that were present during the growing season on this coursetextured soil. Nitrogen losses from the soil profile were directly related to the quantity of N remaining in the upper 1 m of the soil profile after the crop was harvested. Larger quantities of N were lost from the Groseclose soil where conventional till was employed during the first year of the study. This was attributed to enhanced mineralization where notill was converted to conventional till and to lower yields and lower N recovery with conventional till. Losses of N tended to be higher from the conventionaltill plots because of the larger quantities remaining at the end of the growing season. It should be noted that the years during which these studies were extremely dry, and the additional moisture in the Groseclose soil where notill management was employed resulted in increased N recovery. This study also emphasizes the need for better methods for making N recommendations for crop production. The model performances varied from year to year & from one tillage practice to another. Because they were written for average soil & climatic conditions, they didn't make satis factory predictions in many instances. Such models require adjustment to reflect the moisture conditions that prevail in this region for corn production.
Bulletin 168
Abstract: The development and use of a new helium microwave induced plasma for the spectrometric determination of metals and nonmetals in aqueous and organic samples is described. Studies concerning the operation and analytical utility of this plasma are presented. The He plasma is shown to be free from interferences that plague argonbased plasmas in elemental determinations. Limits of detection for metals are below the ng/mL (ppb) level and below the ug/mL (ppm) level for nonmetals determined with the He plasma. With the use of a desolvation system, a limit of detection of 30 ng/mL can be obtained. A minimum detectable quantity of 50 ng is achieved when this plasma is used as a detector for chromatography.
Bulletin 169
Abstract: An extensive compilation and review of research literature on the effectiveness of agricultural best management practices (BMPs) produced three specific products: databases, annotated bibliographies, and brief reports about BMPs. The databases contain citation, keywords, and a summary of the article or report and can be searched to locate sources addressing particular aspects of BMP research. An annotated bibliography provides a quick reference and review of many of the citations contained in the BMP literature database. The third component of this project is a brief report in which the current knowledge on specific BMPs, the stateoftheart assessments on the effectiveness of BMPs in terms of improved water quality and resource conservation, the factors affecting BMP adoption and implementation, and current research needs are summarized and reviewed. The focus of all components is on BMPs and BMP research applicable to Virginia. A systems approach to BMP implementation must consider agricultural management, soil conservation, surface and groundwater quality, efficient crop production, farming system needs and constraints, and socioeconomic factors. Continuing research needs include 1) monitoring studies to provide information for characterizing systems and improving management and to support modeling needs and 2) model development and validation to improve management and assessment tools. Important topics requiring additional research in Virginia are supplying crop nutrient needs efficiently, fate and transport of nutrients and pesticides through the soil to groundwater, and pollutant transport from field to stream.
Bulletin 170
Abstract: Passage of the 1986 amendments to the Safe Drinking Water Act (SDWA) reflects increasing knowledge of the occurrence and consequences of contaminants in the nation's drinking water supplies. Implementation of the original SDWA enacted in 1974 was slower than mandated in the legislation, and the amendments were an attempt to facilitate the development and application of controls by streamlining regulatory processes and establishing a more rigid timetable for implementation. Full implementation of the amendments will have major impacts on the water supply industry. Many waterworks will be required to adopt new treatment processes involving substantial construction costs and increased operating costs, and to expand other activities, such as monitoring. These economic impacts will be particularly severe for small waterworks because of the small number of customers to absorb the costs and the inability to achieve economies of scale available to large operations. The difficulties of small waterworks are important because of the large number of such facilities in the industry. A large portion of the population of the United States is served by a relatively small number of large waterworks, but the water supply industry itself is made up of a disproportionate number of small operations that individually serve a small number of customers. The costs of administering the SDWA program, a responsibility that can be delegated to the states, also will increase as a result of the amendments because of greater need for review and approval of facilities and increased demand for services such as technical assistance and water sample analysis. The primary objective of this report is to facilitate preliminary cost estimates for the implementation of the 1986 amendments. Information on treatment technologies for complying with the various requirements is provided, along with associated costs for large and small waterworks. The report concludes with consideration of the broader management implications of the 1986 amendments. One of the fundamental implications is the need for a strong state government role in the implementation of the program. State government is in a unique position to coordinate program activities and to provide technical assistance to waterworks operators in understanding and implementing the requirements. Implementation of the amendments also will require attention to funding, both for the state management program and for waterworks where necessary improvements would result in substantial burdens on system customers if costs are covered by rate increases alone. Proposals for raising needed funds by taxing water withdrawals have merit and should be given serious consideration.
Bulletin 171
Abstract: The effects of effluent type, effluent loading rate, dosing interval, and temperature on denitrification in onsite wastewater treatment and disposal systems (OSWTDSs) were evaluated in this study. The variables were soil horizon, effluent type, effluent loading rate, dosing interval, and temperature. Surface and subsurface soil cores were collected from a Groseclose silt loam soil (clayey, mixed, mesic Typic Hapludult) and subjected to the following treatments: aerobic and anaerobic effluent, loading rates of 0.5, 1.0, and 1.5 times the Virginia Department of Health (VDH)-recommended levels, 24-hour and 48-hour dosing rates, and summer and winter temperatures. The effects of the treatments on denitrification were evaluated based on analyses of leachate from the cores, soil chemical analyses, and microcosm studies to estimate actual denitrification activity. From the study, a model was developed that predicted the mean nitrous oxide (N20) production for each combination of the experimental treatments. The results of the study and the model indicate that denitrification can be enhanced in OSWTDSs by the application of anaerobic effluent at the VDH-recommended effluent loading rate to surface soil horizons using a 48-hour dosing interval. A field study was conducted on a Lowell silt loam soil (fine, mixed, mesic Typic Hapludalf). Denitrification was measured at this site using acetylene blocking, and the results compared to those predicted by the denitrification model developed from the laboratory data. The field measurements of denitrification based on N20 concentration in the soil atmosphere were almost three orders of magnitude higher than that predicted by the model.
Bulletin 172
Abstract: Small amounts of applied pesticide chemicals eventually can end up in nontarget areas such as wetlands, sediments, and groundwater where anaerobic conditions often predominate. Runoff and leaching are major means by which pesticides move away from application sites. Pesticides also can find their way into nontarget areas as a result of inappropriate disposal and accidental spills. We evaluated the biodegradability of atrazine, cyanazine, and dicamba in wetland soils under nitratereducing and methanogenic conditions. Wetland soil samples were collected from three different sites in the Chesapeake Bay watershed region. These sites represented both tidal (Lawnes and Levy soils) and nontidal (Myatt soil) wetlands. Tidal wetlands are water-saturated throughout the year, whereas nontidal wetlands are saturated only during certain times of the year. Herbicide fate studies were conducted in wetland soil microcosms consisting of serum bottles filled with soil slurry and containing either atrazine, cyanazine, or dicamba. Atrazine was extremely stable in wetland soil microcosms regardless of incubation temperature, redox status (nitrate-reducing versus methanogenic conditions), or soil type. Neither temperature nor redox status affected cyanazine stability in Myatt wetland soil microcosms. We observed a significant decrease in cyanazine concentration in Lawnes wetland microcosms incubated under methanogenic and nitratereducing conditions. Losses were more pronounced at 25° than at 15°C. Results from enrichment culture studies suggest that cyanazine was cometabolized (i.e., cyanazine could not be used as a carbon and energy source by the microorganisms) in Lawnes soil microcosms. Dicamba was readily biodegraded in the wetland soils tested, although total mineralization was not achieved.
Bulletin 173
Abstract: The major portion of far southwestern Virginia is drained by four major river systems: the Powell, the Clinch, the Holston, and the Big Sandy. The purpose of this study was to evaluate changes in water quality within these four river systems over a 20-year period extending from 1970 through 1989. Data collected by the Virginia Water Control Board (VWCB) and the Tennessee Valley Authority (TVA) at 38 water quality monitoring stations were analyzed to identify long-term trends. Specific water quality variables analyzed were dissolved oxygen (DO), biochemical oxygen demand (BOD), pH, filterable residue (FR), nonfilterable residue (NFR), total Kjeldahl nitrogen (TKN), total phosphorous (TP), and fecal coliforms (FC). Statistical analyses to identify and characterize trends were conducted using the seasonal Kendall test for trend. To quantify trend, the rate of change (slope) of each water quality variable was estimated. Where flow data were available, the water quality data were adjusted for flow. The flow-adjusted data (with the effect of flow removed) then were analyzed for trend. A comparison of median values to available VWCB standards indicate regional water quality to be good with respect to the majority of the variables studied. One exception is FR (an indicator of dissolved solids) concentrations in the Big Sandy basin, where medians approach VWCB standards for drinking water at some stations and increasing trends prevailed. Another exception is FC concentrations. Although declining trends were common and widespread, 10 stations with median FC concentrations exceeding the VWCB 200-per-100-ml standard failed to exhibit declining trends. Marked water quality improvements were observed with respect to BOD and NFR (an indicator of suspended solids), both of which exhibited declining trends at a number of stations throughout the region. Numerous pH increases were detected in the Big Sandy and Powell basins, while high incidences of declining pH trends were detected in the Clinch and Holston basins. TKN concentrations exhibited increasing trends at a high proportion of the Holston basin monitoring stations and at half the Clinch basin stations; rising TP trends were detected at 6 of 14 Holston basin stations. Median values for both TP and TKN concentrations were generally low. DO concentrations appeared to be generally stable throughout the region-six stations exhibited increases; eight stations exhibited declines. Water quality trends occurred in association with land-use practices and other influences. Monitoring stations were classified according to four primary influences: land use in coal-mining areas, land use in agricultural areas, mixed land use (both agricultural and coal mining), and urban and point sources. Monitoring stations in agriculture-influenced locations showed high frequencies of pH and BOD declines, and TP and TKN increases. Stations influenced by coalfield land uses showed high frequencies of pH increases, BOD declines, NFR declines, and FR increases. Stations monitoring point-source and urban discharges showed high frequencies of BOD declines and DO increases. Interpretation of these trends as general indicators of regional water quality must be made with caution, because monitoring station locations were not chosen for the specific purpose of establishing a network to monitor regional water quality.
Bulletin 174
Abstract: A field study of teractions of groundwater and surface water during both baseflow and stormflow conditions was performed at the Reedy Creek watershed in the Virginia Coastal Plain. Several watershed and hillslope scale experiments (including an investigation of the watershed's hydrogeological setting) indicated that surface-water baseflow is supported entirely by drainage of shallow groundwater from a relatively thin (1-6 m thick) water-table aquifer. This relatively permeable surficial aquifer was found to be underlain by dark, olive-gray, clay-silt and diatomaceous Miocene deposits of low permeability known as the Calvert Formation, which is believed to function as an aquiclude in the area. Estimates of the mean saturated hydraulic conductivity (K,) of the water-table aquifer using three different methods were in reasonable agreement (within about a factor of three of 10-2 cm/sec), suggesting that Reedy Creek baseflow can be attributed solely to shallow groundwater discharge. A chemical hydrograph separation technique was used to resolve the contributions of old and new water to stormflow. Results from six rainfall events indicated that old water dominated the stormflow response of the watershed, although the new-water contribution often approached 40% at the hydrograph peak. Computed newwater flow contributing areas were in reasonable agreement with estimated areas of likely saturation (channels, ponds, floodplains) based on digitized topographic maps. These results suggested that stormflow at Reedy Creek is primarily generated by a saturation overland flow mechanism from variable source areas that usually include the stream channels and some signifiicant proportion of the riparian wetland area. Additional field studies of runoff generation, including observations of surface saturation behavior and water-table responses within riparian zones and topographically convergent sideslopes, would be useful in further testing of this hypothesis.
Bulletin 175
Abstract: The fate and transport of atrazine, metolachlor, and bromide as a tracer, were characterized through surface runoff monitoring and soil core sampling on no-till and conventionally tilled field plots planted with corn. A rainfall simulator was used to generate a surface runoff event within 48 hours of pesticide application. In comparison with the conventional-tillage plot, the no-till plot yielded 32% of the runoff volume, 8% of the sediment, and 50% of the pesticide mass. Total losses of atrazine and metolachlor in surface runoff were 0.5-1.5% of the amount applied, with the greatest losses associated with conventional tillage. Significant precipitation in the early stages of the study resulted in rapid leaching of the chemicals in both plots. Statistical tests show that chemicals moved deeper in the no-till plot, as compared to the conventional-tillage plot, in the first two weeks after application. However, statistical analysis of the remaining period shows no consistent differences in pesticide concentrations in the soil profile based on tillage practice. Atrazine dissipation was higher in the no-till plot, and there was a significant carryover of the pesticide in both plots at the end of the 157-day period.