Effects of commercial diazinon and imidacloprid on microbial urease activity in soil and sod

Diazinon [O,O-diethyl O-2-isopropyl-6-methyl(pyrimidine-4-yl) phosphorothioate] and imidacloprid [1-(1-[6-chloro-3-pyridinyl]methyl)-N-nitro-2-imidazolidinimine] are applied to lawns for insect control simultaneously with nitrogenous fertilizers such as urea, but their potential effect on urease activity and nitrogen availability in turfgrass management has not been evaluated. Urease activity in enzyme assays, washed cell assays, and soil slurries was examined as a function of insecticide concentration. Intact cores from field sites were used to assess the effect of insecticide application on urease activity in creeping bentgrass (Agrostis palustris Huds.) and bluegrass (Poa pratensis L.) sod. Bacterial urease from Bacillus pasteurii and plant urease from jack bean [Canavalia ensiformis (L.) DC.] were unaffected by the insecticides. Both insecticides inhibited the growth of Proteus vulgaris, a urease-producing bacterium, but only diazinon significantly reduced urease activity in washed cells; neither insecticide inhibited urease activity in sonicated cells. Neither diazinon nor imidacloprid inhibited urease activity in Woolper soil (fine, mixed, mesic Typic Argiudoll) slurries, but diazinon slightly inhibited urease activity in Maury soil (fine, mixed, semiactive, mesic Typic Paleudalf) slurries. Imidacloprid had no effect on urease activity in creeping bentgrass or bluegrass sod at up to 10 times the commercial application rate. Diazinon briefly, but significantly, reduced urease activity in bluegrass sod. Co-application of imidacloprid and urea appears to be benign with respect to urease activity in soil and sod. Diazinon, in contrast, appears to have a significant, short-term, inhibitory effect on the microbial urease-producing community, but that effect depends on soil type.     

The hardrock minerals industry and the landscape architect

The landscape architecture profession is a source of creative thinking and planning which is relatively untapped within the mining industry in the United States of America. The landscape architect has been active in European operations for years as indicated by the four examples presented. The landscape architect can provide an important interface with mine design and engineering and environmental affairs. To initiate this interface within the United States, and increase its effectiveness, six objectives are presented and discussed.     

Fertilizer, tillage, and dairy manure contributions to nitrate and herbicide leaching

Few studies have examined the water quality impact of manure use in no-tillage systems. A lysimeter study in continuous corn (Zea mays L.) was performed on Maury silt loam (fine, mixed, semiactive, mesic Typic Paleudalf) to evaluate the effect(s) of tillage (no-till [NT] and chisel-disk [CD]), nitrogen fertilizer rate (0 and 168 kg N ha(-1)), and dairy manure application timing (none, spring, fall, or fall plus spring) on NO3-N, atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and alachlor [2-chloro-2'-6'-diethyl-N-(methoxymethyl)acetanilide] concentrations in leachate collected at a 90-cm depth. Herbicides were highest immediately after application, declining to less than 4 mug L(-1) in about two months. Manure and manure timing by tillage interactions had little effect on leachate herbicides; rather, the data suggest that macropores rapidly transmitted atrazine and alachlor through the soil. Tillage usually did not significantly affect leachate NO3-N, but no-tillage tended to cause higher NO(3)-N. Manuring caused higher NO3-N concentrations; spring manuring had more impact than fall, but fall manure contained about 78% of the N found in spring manure. Nitrate under spring "only fertilizer" treatment exceeded 10 mg L(-1) 38% of the time, compared with 15% for spring only manure treatment. After three years, manured soil leachate NO3-N exceeded that for soil receiving only N fertilizer. Soil profile (90 cm) NO3-N after corn harvest exceeding 22 kg N ha(-1) was associated with winter leachate NO3-N greater than 10 mg N L(-1). Manure can be used effectively in conservation tillage systems on this and similar soils. Accounting for all N inputs, including previous manure applications, will be important.     

A Processing,Characterization and Marine Biodegradation Study of Melt-Extruded Polyhydroxyalkanoate (PHA) Films

A series of polyhydroxyalkanoates (PHA), all containing 1% nucleating agent but varying in structure, were melt-processed into films through single screw extrusion techniques. This series consisted of three polyhydroxybutyrate (PHB) and three polyhydroxybutyrate-valerate (PHBV) resins with varying valerate content. Processing parameters of temperature in the barrel (165–173 °C) and chill rolls (60 °C) were optimized to obtain cast films. The gel-permeation chromatography (GPC) results showed a loss of 8–19% of the polymer’s initial molecular weight due to extrusion processing. Modulated differential scanning calorimetry (MDSC) displayed glass transition temperatures of the films ranging from −4.6 to 6.7 °C depending on the amount of crystallinity in the film. DSC data were also used to calculate the percent crystallinity of each sample and slightly higher crystallinity was observed in the PHBV series of samples. X-ray diffraction patterns did not vary significantly for any of the samples and crystallinity was confirmed with X-ray data. Dynamic mechanical analysis (DMA) verified the glass transition trends for the films from DSC while loss modulus (E′) reported at 20 °C showed that the PHBV (3,950–3,600 MPa) had the higher E′ values than the PHB (3,500–2,698 MPa) samples. The Young’s modulus values of the PHB and PHBV samples ranged from 700 to 900 MPa and 900 to 1,500 MPa, respectively. Polarized light microscopy images revealed gel particles in the films processed through single-screw extrusion, which may have caused diminished Young’s modulus and tensile strength of these films. The PHBV film samples exhibited the greatest barrier properties to oxygen and water vapor when compared to the PHB film samples. The average oxygen transmission rate (OTR) and water vapor transmission rate (WVTR) for the PHBV samples was 247 (cc-mil/m²-day) and 118 (g-mil/m²-day), respectively; while the average OTR and WVTR for the PHB samples was 350 (cc-mil/m²-day) and 178 (g-mil/m²-day), respectively. Biodegradation data of the films in the marine environment demonstrated that all PHA film samples achieved a minimum of 70% mineralization in 40 days when run in accordance with ASTM 6691. For static and dynamic incubation experiments in seawater, microbial action resulting in weight loss as a function of time showed all samples to be highly biodegradable and correlated with the ASTM 6691 biodegradation data.     

Use of selected chemical markers in combination with a multiple regression model to assess the contribution of domesticated animal sources of fecal pollution in the environment

Human and animal wastes are major sources of environmental pollution. Reliable methods of identifying waste sources are necessary to specify the types and locations of measures that best prevent and mitigate pollution. This investigation demonstrates the use of chemical markers (fecal sterols and bile acids) to identify selected sources of fecal pollution in the environment. Fecal sterols and bile acids were determined for pig, horse, cow, and chicken feces (10-26 feces samples for each animal). Concentrations of major fecal sterols (coprostanol, epicoprostanol, cholesterol, cholestanol, stigmastanol, and stigmasterol) and bile acids (lithocholic acid, deoxycholic acid, cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and hyodeoxycholic acid) were determined using a gas chromatography and mass spectrometer (GC-MS) technique. The fecal sterol and bile acid concentration data were used to estimate parameters of a multiple linear regression model for fecal source identification. The regression model was calibrated using 75% of the available data validated against the remaining 25% of the data points in a jackknife process that was repeated 15 times. The regression results were very favorable in the validation data set, with an overall coefficient of determination between predicted and actual fecal source of 0.971. To check the potential of the proposed model, it was applied on a set of simulated runoff data in predicting the specific animal sources. Almost 100% accuracy was obtained between the actual and predicted fecal sources. While additional work using polluted water (as opposed to fresh fecal samples) as well as multiple pollution sources are needed, results of this study clearly indicate the potential of this model to be useful in identifying the individual sources of fecal pollution.     

Soil microbial community response to hexavalent chromium in planted and unplanted soil

Theories suggest that rapid microbial growth rates lead to quicker development of metal resistance. We tested these theories by adding hexavalent chromium [Cr(VI)] to soil, sowing Indian mustard (Brassica juncea), and comparing rhizosphere and bulk soil microbial community responses. Four weeks after the initial Cr(VI) application we measured Cr concentration, microbial biomass by fumigation extraction and soil extract ATP, tolerance to Cr and growth rates with tritiated thymidine incorporation, and performed community substrate use analysis with BIOLOG GN plates. Exchangeable Cr(VI) levels were very low, and therefore we assumed the Cr(VI) impact was transient. Microbial biomass was reduced by Cr(VI) addition. Microbial tolerance to Cr(VI) tended to be higher in the Cr-treated rhizosphere soil relative to the non-treated systems, while microorganisms in the Cr-treated bulk soil were less sensitive to Cr(VI) than microorganisms in the non-treated bulk soil. Microbial diversity as measured by population evenness increased with Cr(VI) addition based on a Gini coefficient derived from BIOLOG substrate use patterns. Principal component analysis revealed separation between Cr(VI) treatments, and between rhizosphere and bulk soil treatments. We hypothesize that because of Cr(VI) addition there was indirect selection for fast-growing organisms, alleviation of competition among microbial communities, and increase in Cr tolerance in the rhizosphere due to the faster turnover rates in that environment.     

Satellite telemetry reveals behavioural plasticity in a green turtle population nesting in Sri Lanka

Satellite transmitters were deployed on ten green turtles (Chelonia mydas) nesting in Rekawa Sanctuary (RS-80.851°E 6.045°N), Sri Lanka, during 2006 and 2007 to determine inter-nesting and migratory behaviours and foraging habitats. Nine turtles subsequently nested at RS and demonstrated two inter-nesting strategies linked to the location of their residence sites. Three turtles used local shallow coastal sites within 60 km of RS during some or all of their inter-nesting periods and then returned to and settled at these sites on completion of their breeding seasons. In contrast, five individuals spent inter-nesting periods proximate to RS and then migrated to and settled at distant (>350 km) shallow coastal residence sites. Another turtle also spent inter-nesting periods proximate to RS and then migrated to a distant oceanic atoll and made forays into oceanic waters for 42 days before transmissions ceased. This behavioural plasticity informs conservation management beyond protection at the nesting beach.