To subdivide the large group of kaolinitic soil clays a new empirical index of crystallinity was obtained from the X-ray diffraction patterns of eight standard kaolins.The index used is the ratio of the intensity above background of the peak at 4.46A to the intensity above background at about 2.43A (43.2" 28 CoKo) and ranges from 4.8 for halloysite to 83 for a well-ordered triclinic kaolinite. For the kaolins from a group of soils from S.W. Nigeria, the ratio lies between 4.3 and 13.7 and can be tentatively related to the presence of weatherable minerals in the soil and/or the length of the dry season.

SummaryWe investigated environmental factors influencing the distribution of hookworm infection in KwaZuluNatal, South Africa. Prevalence data were sourced from previous studies and additional surveys carried out to supplement the database. When geo-referenced the data revealed that higher prevalences are limited to areas below 150 m above sea level, and low prevalences to areas above this altitude. Using univariate analysis we investigated the differences in environmental factors in the two areas. The relationship between hookworm prevalence, altitude and climate-derived variables was assessed using Pearson correlation coefficient, and that of soil type using the t-test. Multivariate analysis was used to determine environmental factors that combine best to provide favourable conditions for hookworm distribution. The results revealed that areas £150 m above sea level, i.e. the coastal plain, supported high prevalences ( x x ¼ 45, n ¼ 51), and were characterized by sandy soils with a clay content of less than 15%, warm temperatures and relatively high rainfall. Areas >150 m above sea level, i.e. inland, supported low mean hookworm prevalences ( x x ¼ 6, n ¼ 21), and were characterized by soils with a clay content of more than 45%, variable temperatures and moderate rainfall. Hookworm prevalence also decreased southwards as temperatures became slightly cooler, rainfall remained more-or-less constant and the coastal plain narrowed. In the multivariate model prevalence was most significantly correlated with the mean daily minimum temperature for January followed by the mean number of rainy days for January. This indicates the importance of summer conditions in the transmission of hookworm infection in KwaZulu-Natal and suggests that transmission may be seasonal.

No abstract

No abstract

Land application of water treatment residue (WTR) the by-product from the production of potable water, is becoming the preferred method of disposal, as there are environmental concerns and increasingly high costs associated with other disposal options. However, before WTR can be applied to land, consideration needs to be given to their chemical and physical characteristics to determine potential impacts. Six WTR samples were obtained from five South African water treatment facilities (Faure Water Treatment Plant (two samples), Rand Water, Umgeni Water, Amatola Water and Midvaal Water Company). The Rand Water WTR was a CaO, FeCl 3 , long-chain organic polymer (LCP) residue with activated silica and CO 2 being added. The Umgeni and Amatola Water WTRs were lime and LCP residues. The Midvaal Water WTR was an Al 2 (SO 4 ) 3 .nH 2 0, FeCl 3 , lime and LCP residue and the Faure WTRs were Fe 2 (SO 4 ) 3 , activated charcoal, lime and LCP residues. These WTR samples were analysed for some physical (particle size distribution, particle density and plant available water) and chemical attributes (pH, electrical conductivity, cation exchange capacity, calcium carbonate equivalence, exchangeable acidity, extractable bases and metal cations, total and plant available nutrients, total elemental analysis and metal fractionation) and mineralogical properties, and their potential for application to land considered. The WTRs tended to be neutral to alkaline in pH, with low electrical conductivity. Generally, amounts of N, P and K were low, but some of the WTRs showed potential to supply other plant nutrients (Ca, Mg, S, Zn, Cu and Fe). Their physical characteristics were variable, showing a wide range in particle size distribution as well as plant available water. Heavy metal concentrations tended to be low, but Mn was elevated in some WTRs, especially in the Faure WTRs, which may lead to plant growth problems. Land application of these WTRs appears to be a feasible disposal option, but currently they are regulated by the 'minimum requirements for disposal of hazardous waste'. Delisting would firstly be required for land application and if then permitted by legislation, the application rates would need to be based on existing soil conditions, the characteristics of a particular WTR, and the proposed land use.

No abstract

No abstract

No abstract