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Chemical and emission spectrographic analyses of three Apollo 11 samples, 10017-29, 10020-30, and 10084-132, are given. Major and minor constituents were determined both by conventional rock analysis methods and by a new composite scheme utilizing a lithium fluoborate method for dissolution of the samples and atomic absorption spectroscopy and colorimetry. Trace constituents were determined by optical emission spectroscopy involving a d-c arc, air-jet controlled. 相似文献
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A total of 763 faecal samples were collected from western grey kangaroos (Macropus fuliginosus) in Western Australia and screened for the presence of Cryptosporidium by PCR at the 18S ribosomal RNA (rRNA) locus. Samples that were positive at the 18S locus were also amplified at the actin locus. The overall prevalence was 9.3% (71/763). At the 18S rRNA locus, sequences were obtained for 28 of the 71 positives. Sequence analysis identified four species; Cryptosporidium fayeri in seven isolates, Cryptosporidium marcopodum in four isolates, Cryptosporidium xiaoi in six isolates and a novel genotype (kangaroo genotype I) in eleven isolates. Analysis at the actin locus confirmed the genetic distinctness of the novel genotype. The results of the present study indicate that in addition to C. fayeri and C. marcopodum, kangaroos may be capable of being infected with a wider range of Cryptosporidium species and genotypes including livestock species such as C. xiaoi. The novel genotype identified in the kangaroos most likely represents a cryptic species that requires further analyses to confirm its species status. 相似文献
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Soil salinization may negatively affect microbial processes related to carbon dioxide(CO_2) and nitrous oxide(N_2O) emissions. A short-term laboratory incubation experiment was conducted to investigate the effects of soil electrical conductivity(EC) and moisture content on CO_2 and N_2O emissions from sulfate-based natural saline soils. Three separate 100-m long transects were established along the salinity gradient on a salt-affected agricultural field at Mooreton, North Dakota, USA. Surface soils were collected from four equally spaced sampling positions within each transect, at the depths of 0–15 and 15–30 cm. In the laboratory, artificial soil cores were formed combining soils from both the depths in each transect, and incubated at 60% and 90% water-filled pore space(WFPS) at 25?C. The measured depth-weighted EC of the saturated paste extract(EC_e) across the sampling positions ranged from 0.43 to 4.65 dS m~(-1). Potential nitrogen(N) mineralization rate and CO_2 emissions decreased with increasing soil EC_e, but the relative decline in soil CO_2 emissions with increasing ECe was smaller at 60% WFPS than at 90% WFPS. At 60% WFPS, soil N_2O emissions decreased from 133 μg N_2O-N kg~(-1) soil at EC_e 0.50 dS m~(-1) to 72 μg N_2O-N kg~(-1) soil at EC_e = 4.65 dS m~(-1). In contrast, at 90% WFPS,soil N_2O emissions increased from 262 μg N_2O-N kg~(-1) soil at EC_e = 0.81 dS m~(-1) to 849 μg N_2O-N kg~(-1) soil at EC_e = 4.65 dS m~(-1), suggesting that N_2O emissions were linked to both soil ECe and moisture content. Therefore, spatial variability in soil EC_e and pattern of rainfall over the season need to be considered when up-scaling N_2O and CO_2 emissions from field to landscape scales. 相似文献
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Abbey F. Wick Jean Haley Caley Gasch Terry Wehlander Lee Briese Susan Samson‐Liebig 《Soil Use and Management》2019,35(1):177-184
Farmer adoption of practices to build soil health can be enhanced using a knowledge network supported by programs and resources that incorporate technical, social and experiential learning pathways. University Extension plays a critical role in building and supporting the knowledge network by serving as (a) a boundary organization to create space for conversations to occur, (b) network manager to facilitate learning and (c) builder of social capital to encourage trust in the network. The North Dakota State University (NDSU) Soil Health Program was used to illustrate the above approach. Between 2014 and 2016, 32 informal discussion groups, called Soil Health Café Talks, reached 156 individuals. A knowledge network of all participants was developed using NodeXL. The 10 most influential individuals in the network included two scientists, five farmers, one crop consultant and two Extension specialists. All non‐NDSU participants received an evaluation form. Respondents increased their frequency of discussing cover crops with other individuals and increased sharing equipment across farming operations (i.e., vertical tillage implements and no‐till drills). Of the topics discussed, over 25% of respondents adopted practices using cover crops (interseeding and using cover crops for weed control and adjusting rotations to incorporate cover crops) as a result of attending Café Talks. Respondents also increased their use of NDSU Soil Health online resources such as Twitter (22%), YouTube (23%) and the web page (21%) as follow‐up information to Café Talks. Network‐based approaches have proven to be successful in encouraging on‐farm adoption of soil health‐building practices. 相似文献
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Abbey F. Wick W. Lee Daniels Whitney L. Nash James A. Burger 《Land Degradation \u0026amp; Development》2016,27(4):965-972
Sustainability of mined‐land reclamation is of growing importance, with over 600,000 ha of the Appalachian coal region disturbed since 1977. Long‐term evaluation of soil under various reclamation strategies is also important. Aggregation and organic matter (OM) influence both soil structure and function and can be of use in evaluating reclaimed systems. The objective of this study was to examine these two parameters in a long‐term experiment (27 years) where various types (control‐CON, topsoil‐TS, sawdust‐SD and biosolids‐BS) and rates of soil amendments (biosolids: BS‐22, BS‐56, BS‐112 and BS‐224 Mg ha−1) have been applied. Macroaggregates (>250 µm) comprised >95% of total aggregation across all treatments, indicating the importance of this size class for soil development. Macroaggregate carbon (C) and nitrogen (N) pools contributed more to stabilization of OM in these soils than microaggregate pools. All BS treatments contained higher concentrations of aggregate C (96·8–127 g C kg−1 aggregate) and N (6·80–8·22 g N kg−1 aggregate) relative to CON; however, mass of C and N did not vary among application rates. Though few differences were expressed in C and N pool sizes among treatments, there was some indication that amendments impact reclaimed sites early in soil development (~ < 10 years), while vegetation may exert more dominance in subsequent years. It is important to select appropriate management strategies to favor not only the establishment of desirable vegetation but also preservation of soil macroaggregate structure to improve long‐term nutrient supply, physical soil properties and potential C‐sequestration in reclaimed soils. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Clair Thomas A. Ehrman James M. Ouellet Abbey J. Brun Guy Lockerbie David Ro Chul-Un 《Water, air, and soil pollution》2002,135(1-4):335-354
Sixty-three lakes were sampled semi-annually for acid precipitation – related variables in Canada's Atlantic Provinces,Nova Scotia and Newfoundland from 1983 to 1997. A further 31 sites were sampled beginning in 1989 in Nova Scotia. We analyzedthe water chemistry data for trends in pH, acid neutralization capacity, sulfate and base cations using the whole data set for the original 63 sites and the most recent eight years' data for all sites. We also analyzed acid deposition at two CAPMoN precipitation chemistry sites located at the two extremes of thesampling region for trends. We found that hydrogen deposition decreased by 20% in Newfoundland and 30% in Nova Scotia, and sulfate decreased by 36 and 34%, respectively. Sulfate and basecations in lake waters showed decreases as expected, though lakeacidity and acid neutralization capacity did not show improvements. The conflicting trends in chemical variables suggest that though anthropogenically-induced weathering is diminishing in this region, conditions have not returned to `natural' background conditions. 相似文献
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Soil and microbiological properties of a tropical rain forest soil were evaluated 17 years after oil spillage to access the chronic effects of, and interrelationship between population of petroleum hydrocarbon utilizing and nitrifying microorganisms. The spatial distribution of petroleum hydrocarbons (oil), the nutrient status and the abundance of heterotrophic microbes along soil transect lines in the contaminated zones served as the index for corroborating the results. The pH status of soil in the contaminated (Heavy impact — HI, and moderate inpact — MI) zones varied from acidic, that is 4.0 to near neutral PH, that is 6.0. The C content of soils decreased from 3.6% at the HI zones to 2.84% at the MI zones. Total N in the HI and MI zones differed by a factor of 0.10%. Available P was higher at the MI than HI zone, while CEC decreased from a combined mean of 6.48 at the HI zones to 4.46 at the MI zones. Although residual oil content was higher in the HI zones than MI zone, the soil nutrient status within these two zones did not vary significantly (P=0.05). However, soil microbes responded differently. For instance, petroleum hydrocarbon utilizers correlated positively with the distribution of oil in the environment. But, not the nitrifying microorganisms. Aerobic nitrifiers were abundant at the HI than MI zones, while anaerobic nitrifiers were higher at the MI than HI zones. With the presence of petroleum hydrocarbon utilizers anf nitrifying microbes. It is possible to enhance the degradation of oil in the 17 yr old spillage by adopting bioremediation. 相似文献
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L. Abbey R. Kanton H. Braimah 《The Journal of Horticultural Science and Biotechnology》2013,88(6):803-805
SummaryThe study investigated the response of shallots to different levels of defoliation at different growth stages. The effect of cutting off 50%, 75%, and 100% of leaves of four, six, and eight week old shallot plants was assessed. Defoliation at an early stage of growth, i.e. three-leaf stage imposed stressful conditions, and initially reduced growth rate. Whilst lateral bud numbers increased with the severity of defoliation in four week old shallots, lateral shoots and bulb number decreased. There was significant delay in maturity and a reduction in bulb size and weight in shallots defoliated at six weeks. Six weeks old shallots defoliated at 100% recorded the lowest sucrose content of 6%. Numbers of fresh bulb scales was significantly decreased with increasing defoliation and growth. The effect of defoliation on growth, yield and quality depended on the growth stage of the crop. However, 50% defoliation at all growth stages gave appreciable yield and bulb quality compared with the undefoliated control in this trial. 相似文献
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