Will Limits of the Earth's Resources Control Human Numbers?

The current world population is 6 billion people. Even if we adopted a worldwide policy resulting in only 2.1 children born per couple, more than 60 years would pass before the world population stabilized at approximately 12 billion. The reason stabilization would take more than 60 years is the population momentum – the young age distribution – of the world population. Natural resources are already severely limited, and there is emerging evidence that natural forces already starting to control human population numbers through malnutrition and other severe diseases. At present, more than 3 billion people worldwide are malnourished; grain production per capita has been declining since 1983; irrigation per capita has declined 12% during the past decade; cropland per capita has declined 20% during the past decade; fish production per capita has declined 7% during the past decade; per capita fertilizer supplies essential for food production have declined 23% during the past decade; loss of food to pests has not decreased below 50% since 1990; and pollution of water, air, and land has increased, resulting in a rapid increase in the number of humans suffering from serious, pollution-related diseases. Clearly, human numbers cannot continue to increase.     

Composting olive mill pomace and other residues from rural southeastern Spain

The costly disposal of the semisolid residual pomace generated in the two phase extraction used in modern olive mills is causing serious problems to the small oil producers of rural southeastern Spain. Composting may be a viable alternative since complementary residues are usually available in these areas to prepare an adequate starting mixture. In this work, four different combinations of residues (pomace+rabbit manure, pomace+sheep manure, pomace+rabbit manure+rice straw, pomace+rabbit manure+almond shells) were composted in 3 ton piles aerated by turnings, using technology available to any small community of oil producers. During the four long processes (9-10 months), a steady decrease of organic matter and increases in the concentrations of nutrient and humic substances were observed, together with large increases in pH and salinity which may reduce the agronomic value of the final products.     

Use of co-combustion bottom ash to design an acoustic absorbing material for highway noise barriers

The present study aims to determine and evaluate the applicability of a new product consisting of coal bottom ash mixed with Portland cement in the application of highway noise barriers. In order to effectively recycle the bottom ash, the influence of the grain particle size of bottom ash, the thickness of the panel and the combination of different layers with various particle sizes have been studied, as well as some environmental properties including leachability (EN-12457-4, NEN-7345) and radioactivity tests. Based on the obtained results, the acoustic properties of the final composite material were similar or even better than those found in porous concrete used for the same application. According to this study, the material produced presented no environmental risk.     

Effect of long-term fertilization on soil nitrate distribution

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Nitrogen critical loads and management alternatives for N-impacted ecosystems in California

Empirical critical loads for N deposition effects and maps showing areas projected to be in exceedance of the critical load (CL) are given for seven major vegetation types in California. Thirty-five percent of the land area for these vegetation types (99,639 km²) is estimated to be in excess of the N CL. Low CL values (3–8 kg N ha^?1 yr^?1) were determined for mixed conifer forests, chaparral and oak woodlands due to highly N-sensitive biota (lichens) and N-poor or low biomass vegetation in the case of coastal sage scrub (CSS), annual grassland, and desert scrub vegetation. At these N deposition critical loads the latter three ecosystem types are at risk of major vegetation type change because N enrichment favors invasion by exotic annual grasses. Fifty-four and forty-four percent of the area for CSS and grasslands are in exceedance of the CL for invasive grasses, while 53 and 41% of the chaparral and oak woodland areas are in exceedance of the CL for impacts on epiphytic lichen communities. Approximately 30% of the desert (based on invasive grasses and increased fire risk) and mixed conifer forest (based on lichen community changes) areas are in exceedance of the CL. These ecosystems are generally located further from emissions sources than many grasslands or CSS areas. By comparison, only 3–15% of the forested and chaparral land areas are estimated to be in exceedance of the NO₃^? leaching CL. The CL for incipient N saturation in mixed conifer forest catchments was 17 kg N ha^?1 yr^?1. In 10% of the CL exceedance areas for all seven vegetation types combined, the CL is exceeded by at least 10 kg N ha^?1 yr^?1, and in 27% of the exceedance areas the CL is exceeded by at least 5 kg N ha^?1 yr^?1. Management strategies for mitigating the effects of excess N are based on reducing N emissions and reducing site N capital through approaches such as biomass removal and prescribed fire or control of invasive grasses by mowing, selective herbicides, weeding or domestic animal grazing. Ultimately, decreases in N deposition are needed for long-term ecosystem protection and sustainability, and this is the only strategy that will protect epiphytic lichen communities.     

Bacterial leaching of metals from sewage sludge by indigenous iron-oxidizing bacteria

Bioleaching of metals can be achieved in sewage sludge using Thiobacillus ferrooxidans, which obtains its energy requirements from the oxidation of added ferrous iron. The purpose of this study was to verify the presence of indigenous T. ferroxidans and to evaluate their adaptive capacity and leaching potential. Nineteen sludges (primary, secondary, aerobically and anaerobically digested, oxidation pond) were tested and all of them contained indigenous iron-oxidizing bacteria. The acclimation of these organisms by successive transfers allowed a rise of sludge redox potential over 450 mV and a decrease of sludge pH between 3.8 and 2.2 over a 10-day incubation period. The metal solubilization efficiencies were Cd: 55-98%, Cr: 0-32%, Cu: 39-94%, Mn: 71-98%, Ni: 37-98%, Pb: 0-31% and Zn: 66-98%, were reached with these indigenous strains. The results obtained show that the metal bioleaching may be easily realized by direct acclimation of sludge microflora.     

Root growth responses of Anagallis arvensis L., primulaceae to air pollution

The root growth response to air pollution in populations of Anagallis arvensis growing about 0.5, 2, 6, 12 and 20 km leeward from a power plant complex varied with the level of pollution, age of the stand and meteorological conditions. The roots were more affected by the pollutants at a young stage and the loss in net primary productivity was proportional to the pollution level. The populations up to 2 km from the source of pollution completed their life cycle quickly. The coal consumption rate at the power plant, relative humidity, wind direction and other environmental factors were found to influence the degree of growth response to air pollution.