Air and soil temperature

The optimum temperature for the metaboUc processes within a temperate plant, especially photosynthesis, is about 25 °C. Therefore, in most seasons and especially during autumn and early spring, plants will not be metabohsing at their optimum rate in the UK. Small increases or decreases in temperature from year to year will not have a significant effect on production, but it has been shown that, in very hot summers, e.g. those of 1975 and 1976, the photosynthetic rate and the duration of the Green Area Index (GAI) of crop plants was significantly decreased. These summers were characterised by temperatures above 25 °C. The summer of 2012 was one of the wettest and coldest on record with a mean temperature of 13.9 °C. This also had a detrimental effect on yields of crops. 

The soil temperature may also be affected by colour - dark soils absorb more heat than light-coloured soils. Also, damp soils can absorb more heat than diy soils. The presence of stones can also increase mean soil temperatmes by acting as heat reserves in a similar way to storage radiators in buildings. The average January air 

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The most important factor related to chlorophyll breakdown in citrus peel is cool temperatures. According to Stearns and Young (6 ), a color break results from temperatures below 13°C in Florida. In California studies, the daytime air, the nighttime air and soil temperatures were all found to be important... 

Figure 4. Mean air and soil temperatures and precipitation in study area, 1976-84.

Seeds of Triticum aestivum cv. Bezostaya a winter wheat, were sown in a field plot at the University of Essex (N51°52, E0 57 ) on 26/9/1988. The youngest fully expanded leaves were selected at random and used for all measurements. Some plants were shaded from direct sunlight using plastic screens. Air and soil temperatures and photosynthetic photon flux density (PPFD 400-700nm) were monitored at 10 minute intervals using a Delta-T weather station located next to the plot. 

Sverdrup, H., Warfvinge, P., Rosen, K. (1995). A model for the impact of soil solution Ca Al ratio, soil moisture and temperature on tree base cation uptake. Water, Air and Soil Pollution, 61, 365-383. 

Figure 5.8 Temperatures in ricefields over a year, IRRI, Laguna, Philippines. Values are means over a month air temperature is maximum water and soil temperatures were taken at 1400 h (Roger, 1996). Reproduced by permission of IRRI...

If sediment was collected from a particular waterway, the distribution of the element of interest between different components of the sediment was found to vary with the degree of exposure to air and the temperature of any drying stages (Rapin et al., 1986 Kersten and Foerstner, 1986). The minor elements present in sediments (and soils) are not uniformly distributed. Part can be present as mineral fragments derived from the original parent rock, while other parts can be associated with distinct component phases such as carbonate compounds, hydrous oxides of Fe, Al, Mn and organic matter. Some fractions are loosely sorbed on particle surfaces or are held on ion exchange sites. 

Estimated t,/2 25 to > 201 d under a variety of agronomic conditions in agriculture soils depending on depth of incorporation, soil moisture, soil temperature, sil air, and soil organic matter content (summary of literature data, Grover et al. 1997)... 

In addition to the tetraethyl or tetramethyl lead, both types of antiknock fluids also contained 1,2-dichloroethane and 1,2-dibromoethane (ca. 35% by weight) to react with the lead released on combustion to form lead bromide and lead chloride. These lead halides are volatile at the cylinder combustion temperatures of 800-900°C, and leave the combustion chamber with the exhaust, which prevented the buildup of lead deposits. This was also the final step in the chain of events occurring with the alkylated lead antiknock compounds, which contributed to the widespread dispersal of lead compounds to the air and soil wherever gasoline powered vehicles operated. For this reason, and the toxic exposures during refueling, the alkylated lead addition rate was reduced to not more than 0.5 g of contained lead per U.S. gallon by 1980, even for leaded gasolines [29], and was phased out in the U.S. and Canada by 1985. 

It is translocated relatively slowly from the leaves to the roots and tubers. Depending on temperature, light intensity and air and soil moisture, translocation proceeds in 4-8 days, the effect being manifested by chlorotic symptoms, which develop in 2-4 weeks into necrosis. Combined with other translocatable herbicides, such as 2,4-D, 2,4-DB or silvex, basipetal translocation and thus herbicidal action can be increased, and regrowth from tubers reduced. 

Figure 4.1. General classes of adsorption isotherms. 5 turve, data courtesy of C. S. LeVesque L curve, data from I.C.R. Holford et al. H curve, data from J. Garda-Mirayagaya and A. L. Page, Sorption of trace quantities of cadmium by soils with different chemical and mineralogical composition Water, Air, and Soil Pollution 9 289 (1978) C curve, data from B. Yaron and S. Saltzntan, Influence of water and temperature on adsorption of parathion by soils Soil Sci. Soc. Am, J, 36 583 (1972).

Comparison of native populations, cultivars and fonned complex hybrid populations on diSeient elevation made possible to show the environmental influence on seed set. We took into consideration temperature regime of air and soil, sum of precipitation, humidity and acidity of upper layer of soil (where roots are situated). It was found that on the same elevation, but on different soils seed set was different. For example, on elevation 900 m above sea level seed set was 27.5% on acid soil (pH 4.47) and 46.8% on nearly neutral soil (pH 6.45). On elevation 2000 m above sea level on two plots with pH 6.44 and 6.15 seed set of clover was 49.5 and 47.0%, respectively. It was also determined that the number of weak seeds changed in dependence upon soil acidity with the maximal proportion (above 50%) at pH 4.47. Seed set in inflorescences is higher on 9.5-27.1%, where acidity is 6.0 or above it. 

This simple technique permits the quantitative analysis of volatile compounds in various liquid, semi-liquid or solid foods, in biological fluids and tissues, and environmental contaminants in water, air and soils. The method is very sensitive to the equilibrium solute distribution between phases at the temperature selected for the analysis. Equilibration is greatly dependent on the solubility and viscosity of the samples. This method is particularly suited to highly volatile compounds because they have a favorable equilibrium between liquid (or solid) phase and its headspace, producing a higher concentration of volatile compounds in the headspace. 

Lydersen, E., Salbu, B., Poleo, A.B.S. and I.P.Muniz (1990). The Influence of temperature on aqueous aluminium chemistry. Water, Air, and Soil Pollution (in press). 

More typically, chemical releases have an impact over a long period of time. An example is the release of dioxins into the air and soil at Seveso, Italy, in July 1976. The release was related to the production of trichlorophenol at a plant about twenty miles north of Milan. No explosion occurred. Instead, the release occurred more than six hours after a chemical reaction within a chemical reactor at the plant had been completed. The chemical reaction produced heat, which raised the temperature of the contents of the reactor. This rise in temperature led to additional, spontaneous chemical reactions that increased pressure within the reactor. The increased pressure ruptured a seal, which led to release of the reactor contents into the atmosphere. The resulting toxic cloud of vapors released from the plant contaminated several thousemd acres of a densely populated cu ea of Seveso. Vegetation, birds, and animals near the plant were affected within days of the release. Many herbivorous animals (e.g., rabbits, sheep) died from eating contaminated plants. Nine days cifter the release, dioxins were found to be present in the plants, cmimals, and soils of the ctfea. Skin lesions were reported by residents, especially in children who had more direct contact with the contaminated soils than adults. Two... 

Volatilization. The susceptibility of a herbicide to loss through volatilization has received much attention, due in part to the realization that herbicides in the vapor phase may be transported large distances from the point of application. Volatilization losses can be as high as 80—90% of the total applied herbicide within several days of application. The processes that control the amount of herbicide volatilized are the evaporation of the herbicide from the solution or soHd phase into the air, and dispersal and dilution of the resulting vapor into the atmosphere (250). These processes are influenced by many factors including herbicide application rate, wind velocity, temperature, soil moisture content, and the compound s sorption to soil organic and mineral surfaces. Properties of the herbicide that influence volatility include vapor pressure, water solubility, and chemical stmcture (251). 

In pure dry air at normal temperatures a thin protective oxide film forms on the surface of polished mild steel. Unlike that formed on stainless steels it is not protective in the presence of electrolytes and usually breaks down in air, water and soil. The anodic reaction is ... 

Other data such as light intensity, percentage cloud cover, and soil moisture may also be recorded. The use of meteorological equipment, which can measure critical climatic information such as wind speed (current, maximum and average), humidity, air temperature, and dew-forming point, is preferable in the field. Historic weather data in the form of 10-year averages must be reported and are required for comparison of the trial specific data with the normal weather data. 

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