A glimpse at short-term controls of evapotranspiration along the southern slopes of Kilimanjaro

Future climate characteristics of the southern Kilimanjaro region, Tanzania, are mainly determined by local land-use and global climate change. Reinforcing increasing dryness throughout the twentieth century, ongoing land transformation processes emphasize the need for a proper understanding of the regional-scale water budget and possible implications on related ecosystem functioning and services. Here, we present an analysis of scintillometer-based evapotranspiration (ET) covering seven distinct habitat types across a massive climate gradient from the colline savanna woodlands to the upper-mountain Helichrysum zone (940 to 3960 m.a.s.l.). Random forest-based mean variable importance indicates an outstanding significance of net radiation (R _net) on the observed ET across all elevation levels. Accordingly, topography and frequent cloud/fog events have a dampening effect at high elevations, whereas no such constraints affect the energy and moisture-rich submontane coffee/grassland level. By contrast, long-term moisture availability is likely to impose restrictions upon evapotranspirative net water loss in savanna, which particularly applies to the pronounced dry season. At plot scale, ET can thereby be approximated reasonably using R _net, soil heat flux, and to a lesser degree, vapor pressure deficit and rainfall as predictor variables (R ² 0.59 to 1.00). While multivariate regression based on pooled meteorological data from all plots proves itself useful for predicting hourly ET rates across a broader range of ecosystems (R ² = 0.71), additional gains in explained variance can be achieved when vegetation characteristics as seen from the NDVI are considered (R ² = 0.87). To sum up, our results indicate that valuable insights into land cover-specific ET dynamics, including underlying drivers, may be derived even from explicitly short-term measurements in an ecologically highly diverse landscape.     

Modeling biodegradation and kinetics of glyphosate by artificial neural network

An artificial neural network (ANN) model was developed to simulate the biodegradation of herbicide glyphosate [2-(Phosphonomethylamino) acetic acid] in a solution with varying parameters pH, inoculum size and initial glyphosate concentration. The predictive ability of ANN model was also compared with Monod model. The result showed that ANN model was able to accurately predict the experimental results. A low ratio of self-inhibition and half saturation constants of Haldane equations (< 8) exhibited the inhibitory effect of glyphosate on bacteria growth. The value of K(i)/K(s) increased when the mixed inoculum size was increased from 10(4) to 10(6) bacteria/mL. It was found that the percentage of glyphosate degradation reached a maximum value of 99% at an optimum pH 6-7 while for pH values higher than 9 or lower than 4, no degradation was observed.     

A Comparative Study of Environmental Tobacco Smoke Particulate Mass Measurements in an Environmental Chamber

Particulate mass concentration measurements have been made on environmental tobacco smoke (ETS) for the purpose of assessing the relative accuracy of several measurement procedures. ETS over a range of concentrations was generated in an environmental chamber by three methods. Mass concentration was measured by a gravimetric/spectrophotometric collection procedure, piezoelectric particle mass monitors, two nephelometry-based mass monitors, and a particle counting and sizing system. Two-hour average mass concentrations were determined by each method for concentrations ranging from very low levels up to those achieved by smoking one entire cigarette in the chamber. Statistical comparisons were made among procedures employing the gravimetric filter measurement as the basis for comparison. One nephelometry-based procedure gave significantly higher and the other significantly lower values than the filter determination. In one case, a correction for the difference between the particle mass density of the calibrating aerosol and that of ETS brought the nephelometry-based procedure into reasonable agreement with the filter measurement, while for the other, the correction did not resolve the discrepancy between methods. Statistically significant differences between the responses of two supposedly identical piezoelectric mass monitors were found, as was some slight dependence of the nephelometry- based procedures on method of ETS generation. In summary, the results indicate that significant errors can be expected if the instruments studied are used “off the shelf,” even for ETS generated under controlled laboratory conditions. Caution should be employed in field measurements where numerous sources and types of particulate matter can be encountered.     

On the Determination of Odor Thresholds in Air Pollution Control—An Experimental Field Study on Flue Gases from Sulfate Cellulose Plants

From the hygienic point of view, not only the health hazards caused by air pollutants but also the odor from emitted flue gases should be reduced to a minimum. An effective control of the risk of odor at ground level presupposes knowledge of the source concentration of the odoriferous gas as well as its odor threshold. This threshold has to be estimated empirically, as the flue gases often contain a complex mixture of different odoriferous substances, the odor thresholds of which are in most cases unknown. For this purpose a method has been developed for estimating the odor thresholds of flue gases emitted, from different industrial processes. The method, afield method, is based on an exposure procedure, a number of subjects compare different concentrations of the flue gas with samples of fresh air and decide at what concentration the flue gas is no longer noticeable. The gas samples used are neither compressed, nor absorbed or heated before the exposure test. The method has been used in two studies on gases from Swedish sulfate cellulose plants. In order to estimate the effect on the odor threshold of different deodorizing measures, gas samples were taken not only from the stack but also from different phases in the production process. The results and a brief discussion on the practical applications of the method are given.     

Control of Malodors from Kraft Recovery Operations by Pyrolysis

The major source of malodorous emissions which emanate from kraft mills is the recovery furnace and its associated direct contact evaporator. The primary reasons for this problem are gross furnace overloading and/or inadequate design. Existing recovery furnaces are incapable of carrying out, to an acceptable degree of completion, the complex sequence of physical and chemical steps which describe combustion. These steps are evaporation, sublimination, pyrolysis, recombination, and oxidation. A simplified odor model is presented which establishes the constraints which must be placed on the combustion phase of the recovery operation if environmental concentrations of malodorous compounds are to be held below their respective threshold odor levels. The pyrolysis and recombination steps of combustion have been isolated for study because they encompass the reaction mechanisms responsible for malodorous compound production. The findings of the steady state pyrolysis study indicate that the optimization of pyrolysis appears to be a very desirable process technique for abating alodorous emissions from kraft mills. The comprehensive data obtained in the study has engendered the current design and construction efforts toward a pilot plant operation.     

Analysis of Trace Metal Particulates in Atmospheric Samples Using X-Ray Fluorescence

Trace metals collected on filter paper by a hi-volume air sampler for 24 hours were analyzed using the X-ray fluorescence method. A gamma ray exciting source (²⁴¹Am) and a bremsstrahlung exciting source (¹⁴⁷Pm) were both used to produce the X-rays, the latter being more efficient. For the samples collected in Dayton, several metals were detected, viz.: Ti, Fe, Cu, Zn, Pb, Cd, and Sn. Elements in the periodic table between Ti and Cs were seen to have a sensitivity limit of 0.5 micrograms/m³ of air.     

Determination of Sulfur Oxides in the Flue Gases of the Pulping Processes

The body of information presented in this paper is directed to the operating personnel and process engineers employed in the power and recovery departments of a chemical pulping operation. The proper evaluation of the total analytical and sampling system (TASS), to be used in the determination of sulfur oxides is as important as a proper analytical and recording system (ARS). The presence of other sulfur gaseous compounds and particulates could greatly influence the results of the determination.

The analytical method employed determines sulfur dioxide and trioxide from an aliquot of the trapping solution, 3% hydrogen peroxide and 8 0% isopropyl alcohol respectively. The aliquot is titrated with barium perchlorate in the presence of Thorin indicator. The results of evaluating the method indicated negligible interference from the presence of hydrogen sulfide, mercaptans and nitrogen oxides. A blank correction of 15 parts per million (ppm) is recommended whenever 100 ppm of hydrogen sulfide or more are simultaneously present in the gas stream. Particulaies are shown to interfere either by addition or subtraction. Sulfate particulates that will add to the determination must be removed, but in doing so, care must be exerted to avoid surface-contacting conditions that promote reaction between carbonates and the sulfur oxides. The integrated method of sampling and analysis will permit determinations from a flue gas with sulfur oxides concentrations of 30 ppm and above. The relative standard deviation improves from 10% at 100 ppm SO₂ to 2.6% at 1000 ppm SO₂. In both cases, sulfides were present.     

Reproducibility of the HI-VOL Sampling Method Under Field Conditions

Pairs of standard NASN Hi-Vol suspended particulate samplers were operated biweekly at 25 stations (22 urban, 3 nonurban) from August to December 1969 to determine the comparability of paired samples collected under field conditions. The average of each pair of concentration values is taken as the best estimate of the true value; half the difference between each pair of sample values represents the deviation of the pair from that true value. A cumulative distribution of the individual percent deviations from the corresponding true values shows that half the measurements differ from their true value by less than ±4.5%. 90% of the measurements differ from the true value by less than ± 14%.