In-lake alkalinity generation by sulfate reduction: A paleolimnological assessment

The generation of alkalinity by SO₄ reduction and net storage of reduced S in lake sediments has been estimated from an analysis of sediment cores from 16 lakes in ME, VT, NY, MI, MN, and WY. The cores have been dated by ²¹⁰Pb. The rate of pre-1850 (background) storage of S in lake sediments suggests that alkalinity contribution to lake water from this process ranged from 0.2 to 9.3 geq L^?1, with an average of 4 geq L^?1, Background values are similar for all lakes and remain low in the WY lakes up to the present. Maximum alkalinity contributions recorded in sediment, from upper mid-west and eastern lakes, dated between 1850 and 1985 are between 0.4 and 33 geq L^?1, with a lake mean maximum of 9.9 geq L^?1, Significant increases in recent S storage only occur in eastern lakes. Average values for net S accumulation in the sediment of most lakes for post-1850 sediment are typically less than half of maximum values.     

Assessing selenium cycling and accumulation in aquatic ecosystems

We conducted a joint experimental research and modeling study to develop a methodology for assessing selenium (Se) toxicity in aquatic ecosystems. The first phase of the research focused on Se cycling and accumulation. In the laboratory, we measured the rates and mechanisms of accumulation, transformation, and food web transfer of the various chemical forms of Se that occur in freshwater ecosystems. Analytical developments helped define important Se forms. We investigated lower trophic levels (phytoplankton and bacteria) first before proceeding to experiments for each successive trophic component (invertebrates and fish). The lower trophic levels play critical roles in both the biogeochemical cycling and transfer of Se to upper trophic levels. The experimental research provided the scientific basis and rate parameters for a computer simulation model developed in conjunction with the experiments. The model includes components to predict the biogeochemical cycling of Se in the water column and sediments, as well as the accumulation and transformations that occur as Se moves through the food web. The modeled processes include biological uptake, transformation, excretion, and volatilization; oxidation and reduction reactions; adsorption; detrital cycling and decomposition processes; and various physical transport processes within the water body and between the water column and sediments. When applied to a Se-contaminated system (Hyco Reservoir), the model predicted Se dynamics and speciation consistent with existing measurements, and examined both the long-term fate of Se loadings and the major processes and fluxes driving its biogeochemical cycle.     

Mechanisms of humic material adsorption on kaolin clay and activated carbon

Gel permeation chromatography was used for monitoring the changes in humic molecular weight distribution after contact with kaolin clay and activated carbon. The high molecular weight fractions excluded from Sephadex G-50 were less removed by carbon indicating the exclusion effect of pores, but were preferentially adsorbed by clay. The aliphatic portion of humic acids is effectively removed by carbon as suggested by the decrease in E₄: E₆ ratio. The Freundlich and the Langmuir isotherms showed curvilinearity which was resolved into two straight lines. The sorption effect in humic molecular weight distribution suggests the necessity of batch adsorption test with respect to the treated humic material.     

Impact of trace mineral source on beef replacement heifer growth,reproductive development,and biomarkers of maternal recognition of pregnancy and embryo survival

Trace minerals are known to play important roles in early embryo development. The study objective was to determine effects of trace mineral source on heifer reproductive performance. Beef heifers (n = 129) were randomly assigned to one of two treatments. From weaning through breeding, all heifers were individually fed a basal diet supplemented with cobalt (Co), copper (Cu), manganese (Mn), and zinc (Zn) either from organic sources (COMP; Cu, Mn, and Zn amino acid complexes and Co glucoheptonate; Availa-4, Zinpro Corporation, Eden Prairie, MN) or inorganic sources (INORG; Cu, Mn, and Zn hydroxychlorides; Intellibond C, M, and Z, Micronutrients, Indianapolis, IN) and Co as CoSO₄. Blood samples and a reproductive tract score (RTS) were collected to determine pubertal status. All animals were synchronized and artificially inseminated. Pregnancy status was determined by lymphocyte gene expression, circulating concentrations of pregnancy-associated glycoproteins (PAGs), and by transrectal ultrasonography after artificial insemination. Embryonic loss was defined as when a previously pregnant animal was subsequently diagnosed not pregnant. Data were analyzed using the MIXED procedure in SAS. Puberty (P = 0.44), pelvic area (P = 0.74), RTS (P = 0.49), and estrus expression (P = 0.82) were not influenced by treatment. There was no effect of treatment (P = 0.37) or treatment by time (P = 0.19) on pregnancy, but there was a tendency (P = 0.13) for decreased embryonic loss among COMP heifers (27 ± 6%) compared to INORG heifers (38 ± 6%). There was a treatment by pregnancy status by time interaction (P < 0.01) on circulating PAG concentrations with PAG concentrations tending (P = 0.08) to be greater on day 25 among heifers in the COMP treatment compared to heifers in the INORG group. In summary, source of trace mineral did not affect puberty, RTS, pelvic area, or overall pregnancy success, but feeding complexed trace minerals tended to increase circulating PAG concentrations and embryo survival.     

Scheduling irrigation of cabbages using pan evaporation

Summary A plot irrigator was used to develop a response curve relating cabbage yield to watering level on coarse sandy soils in Western Australia. The daily replacement of 120 to 150% of pan evaporation maximised yield of crops harvested during the late summer and early autumn. With summer harvested crops maturing under high moisture stress, watering twice daily at the same percentage evaporation gave optimum yields. Over-watering and too frequent watering were both found to reduce yields, although not as much as insufficient irrigation. The combined crop and pan factors relating actual crop water needs to pan evaporation were found to be much higher than factors hitherto published.Senior Research Officer, Research Officer and Research Officer, respectively     

Asset management modelling framework for irrigation and drainage systems: Principles and case study application

Sustainability of irrigation and drainage infrastructure poses many challenges to many irrigation authorities worldwide due to a mismatch between the actual cost incurred in the provision of irrigation and drainage service and pricing of this service. This shortfall often leads to inadequate expenditure on maintenance in the absence of adequate subsidies from government or other sources.The asset management modelling framework (AMMF) presented in this paper enables the quantification of on-going ownership costs and operation costs. A life cycle cost (LCC) model for the evaluation of alternative irrigation and drainage asset management strategies is also presented. The AMMF is applied to the evaluation of asset ownership costs and LCC for alternative maintenance and interest rate scenarios in the Cu Chi irrigation system, Vietnam. The cost of three renewal strategies was evaluated: linear depreciation, full annuity and partial annuity. The cost ranges between US$ 28.00/ha and US$ 41.00/ha when interest rate varies between 9 and 3%. The average maintenance expenditure during recent years was estimated to be only US$ 1.30/ha which translates into 0.68% of the total asset replacement cost.The application of a simplified LCC model reveals that the least LCC varies with the level of maintenance and interest rate between US$ 353.5/ha for 5% maintenance expenditure and 12% interest rate to US$ 522.3/ha for 3% maintenance expenditure and 6% interest rate. The importance of exercising value judgements in applying the LCC model is also emphasised and discussed.     

The financial viability of irrigation management companies: A case study of Cu Chi irrigation system,Vietnam

A crucial, yet little understood, element in the economic studies of irrigation is the role played by companies who manage the supply of water. Many of these companies are publicly managed as they have the potential to act as monopolists. Possibly as a consequence of their ownership structure, analysts have questioned the economic viability and management of these firms. The case is made that many of these companies do not run profitably, that they rely on government subsidies to survive, that they do not spend enough on maintenance and that they run down their capital base. The purpose in this paper is to specify the measures that allow analysts to examine the financial viability of a publicly owned irrigation management companies and to apply these to a scheme in Vietnam. Of concern and contention in any irrigation scheme is the price that a company should charge for water in order to recover costs in the short-run. It was found that the company under investigation could not operate without subsidies and did run down their assets. It was found that a great disparity exists between what the consumers were charged for water and what the company received for supplying it. To ensure the sustainability of the Irrigation Management Companies in long term, they may have to increase the water fee by 3.75 times the current rate set by the provincial government (US$ 20 per ha).     

Cytologic detection of Toxoplasma gondii in the cerebrospinal fluid of a dog and in vitro isolation of a unique mouse-virulent recombinant strain

Parasites resembling Neospora caninum or Toxoplasma gondii were detected by cytologic examination of cerebrospinal fluid (CSF) from a dog with neurologic disease. The dog became severely ill and was euthanized. Canine tissue homogenates were used for direct parasite isolation in cell culture, bioassay in 2 mouse lineages, and PCR. T. gondii was isolated in monkey kidney cells, and species identity was confirmed by PCR. Inoculated parasites were highly virulent for mice, which developed clinical signs and were euthanized immediately. PCR-RFLP for T. gondii using the cultured isolate (TgDgBA22) was conducted with 12 genetic markers, and a unique recombinant strain was identified. Detection of T. gondii by CSF cytology, although described in humans, had not been reported previously in dogs, to our knowledge, and was crucial for the diagnosis of toxoplasmosis in the examined dog.     

Status of applied biological control of soil-borne plant pathogens

During the last 15 years a great amount of information has been accumulated on the ecology and physiology of soil-borne plant pathogens around the world. Despite this, very few cases of applied biological or cultural control have been reported. Although soil-borne plant pathogens are widely spread and economically important, only a small fraction of plant pathologists and soil microbiologists has devoted full time in the applied phases of biological control. The number of publications on applied control during the last 10 years in two journals surveyed is exceptionally small. The status of applied biological control of root diseases is considerably less favorable than the situation in entomology where much progress has been made during the last 10 years. The status of biological control (narrowly or broadly defined) of soil-borne pathogens is described here and several examples of applied control are cited. Future prospects for research on the ecology and biological control are also discussed.     

Cryopreservation of Paddlefish Polyodon spathula Milt

Abstract.— A practical procedure for cryopreserving milt of paddlefish Polyodon sparhula was developed to obtain thawed spermatozoa that would fertilize eggs and permit hatching of normal larvae. Milt was mixed with a cryoprotectant medium containing DMSO (2.4 M) in a ratio of 3:1(milt: medium; final concentration of DMSO 0.6 M), stored in 5.0-mL freezing straws, and frozen in dry ice (15 min) and then in liquid nitrogen. A total of three replicates were made; the milt of a different male was used in each replicate. Motility of the thawed spermatozoa decreased to 50%-25% as compared to 100% motility of the fresh (control) spermatozoa. Hatching of paddlefish (16.3 ± 2.2%) from eggs fertilized with thawed spermatozoa was significantly lower ( P ≤ 0.01) than the hatch rate (90.8 ± 2.5%) for the control. It was suggested that an increase in viable motile spermatozoa to egg would result in better fertilization and hatching of paddlefish.