Patterns of urban settlements in Somalia

In this research paper attempts have been made to analyze the distribution of 68 urban settlements in 14 regions of the country. The value of near-neighbour statistic (R) shows nearly random pattern of urban settlements in some regions and approachingly uniform distribution of urban settlements in other regions. Regional distribution of urban settlements and their growth have been explained in context of region's geographical, economic and industrial frameworks.     

CO2 feedbacks and the 100 K year cycle in climate

Summary In an earlier paper (Lindzen, 1986), it was shown that allowing CO₂ to vary with snow/sea ice position could lead to a greatly enhanced response in glaciation to 100 K year orbital forcing—even when 20 K year forcing was much stronger. In that model, snow/sea ice position (SSIP) and glaciation were different: the former was the forcing for the latter. However, SSIP and glaciation were not decorrelated. Observations (Berner et al., 1979; Lorius et al., 1985; Neftel et al., 1982) suggest that CO₂ may be independently related to both SSIP and glaciation. In the present paper, we allow (in a highly simplified manner) such independent dependence, and show how it alters the earlier results. Briefly, the dependence of CO₂ on glaciation can contribute to and even cause a highly enhanced response to the 100 K year component of the forcing. However, the CO₂ dependence on SSIP is, on the whole, more effective in this regard. Thus, we expect time series of CO₂ to show variation on the faster time scales than does glaciation.With 5 Figures     

Groundwater recharge in natural dune systems and agricultural ecosystems in the Thar Desert region, Rajasthan, India

Water and nutrient availability for crop production are critical issues in (semi)arid regions. Unsaturated-zone Cl tracer data and nutrient (NO₃ and PO₄) concentrations were used to quantify recharge rates using the Cl mass balance approach and nutrient availability in the Thar Desert, Rajasthan, India. Soil cores were collected in dune/interdune settings in the arid Thar Desert (near Jaisalmer) and in rain-fed (nonirrigated) and irrigated cropland in the semiarid desert margin (near Jaipur). Recharge rates were also simulated using unsaturated zone modeling. Recharge rates in sparsely vegetated dune/interdune settings in the Jaisalmer study area are 2.7–5.6 mm/year (2–3% of precipitation, 165 mm/year). In contrast, recharge rates in rain-fed agriculture in the Jaipur study area are 61–94 mm/year (10–16% of precipitation, 600 mm/year). Minimum recharge rates under current freshwater irrigated sites are 50–120 mm/year (8–20% of precipitation). Nitrate concentrations are low at most sites. Similarity in recharge rates based on SO₄ with those based on Cl is attributed to a meteoric origin of SO₄ and generally conservative chemical behavior in these sandy soils. Modeling results increased confidence in tracer-based recharge estimates. Recharge rates under rain-fed agriculture indicate that irrigation of 20–40% of cultivated land with 300 mm/year should be sustainable.     

Magnetic properties of soils from sites with different geological and environmental settings

Measurements of magnetic susceptibility of soils, reflecting magnetic enhancement of topsoils due to atmospherically deposited magnetic particles of industrial origin, are used recently in studies dealing with outlining polluted areas, as well as with approximate determination of soil contamination with heavy metals. One of the natural limitations of this method is magnetic enhancement of soils caused by weathering magnetically rich parent rock material. In this study we compare magnetic properties of soils from regions with different geological and environmental settings. Four areas in the Czech Republic and Austria were investigated, representing both magnetically rich and poor geology, as well as point-like and diffuse pollution sources. Topsoil and subsoil samples were investigated and the effect of geology and pollution was examined. Magnetic data including mass and volume magnetic susceptibility, frequency-dependent susceptibility, and main magnetic characteristics such as coercivity (Hc and Hcr) and magnetization (Ms and Mrs) parameters are compared with heavy metal contents. The aim of the paper is to assess the applicability of soil magnetometry under different geological-environmental conditions in terms of magnetic discrimination of dominant lithogenic/anthropogenic contributions to soil magnetic signature. Our results suggest that lithology represents the primary effect on soil magnetic properties. However, in case of significant atmospheric deposition of anthropogenic particles, this contribution can be clearly recognized, independent of the type of pollution source (point-like or diffuse), and discriminated from the lithogenic one. Different soil types apparently play no role. Possible effects of climate were not investigated in this study.