Hazardous earth processes in parts of Bauchi State,Nigeria: Their causes and environmental implications

The August 1985 crack has focussed attention on passive earth processes in parts of Bauchi State, Nigeria. These processes, encompassing groundwater solution and roof collapse, soil shrink-swell, and gullying, are widespread in the Akko, Gombe, and Bauchi Local Government Areas (LGAs) of the State. Soils in these areas are rich in montmorillonite clay minerals and possess appreciable shrink-swell capabilities. Surface heave ranges from 8.1 to 11 cm. Preliminary data on plasticity measurement show a plasticity index (PI) of 13.4 to 15%. Consequently, in response to seasonal changes, the soil usually splits, leaving gaping cracks. These cracks, once formed, constitute channels throug which meteoric water easily penetrates the bedrock. The water is chemically acid and the underlying bedrock contains layers of limestone and shale. Systematic solution of these chemically reactive rocks results in the formation of caverns, the roof of which may ultimately collapse leaving randomly distributed sink holes. These cracks and sink holes run through villages, destroying mud buildings, which often collapse overnight, and transforming most modern block buildings into death traps. They affect roads, bridges, and other foundations, and render farmlands waste, swallowing up livestock.The expansive soil processes, solution and roof collapse phenomena currently identified in these places, are passive phenomena and have been overlooked as geologic hazards. Preliminary results of investigations on the physical and chemical properties of the soils and underlying rocks indicate that these areas of Bauchi State of Nigeria need to be monitored closely to avert disaster.     

Sulphate adsorption capacity and pH of upland podzolic soils in Scotland: Effects of parent material,texture and precipitation chemistry

A regional survey of podzol B horizons has been carried out to investigate the effects of parent material and soil texture on sulphate (SO₄²⁻) adsorption capacity and pH in Scottish soils. Sulphate adsorption was measured on equilibration of the soils with 10 and 100 mg 1⁻¹ SO₄²⁻ solutions. The results showed that soil texture and soil parent material had a significant effect on SO₄²⁻ adsorption. Significant correlations were found between sulphur (S) deposition loads and SO₄²⁻ adsorption, and between precipitation pH and soil pH, but not between total hydrogen ion (H⁺) load and soil pH, even on sensitive soils. Relationships between the chemical composition of atmospheric deposition and soil pH could be marginally improved if the possible amelioration of acidification by base cation inputs, especially on sensitive soils, was taken into account.     

Micromorphology and mineralogy of gullied soils in Anambra State,Nigeria

Detailed studies on the micromorphology and mineralogy of two guillied soils in Anambra State of Nigeria were carried out. Thin sections were prepared and point counting technique used in investigating the pedological features. Micromorphological analysis indicates that the S-matrix of the soil have mainly sepic and inundulic with few asepic plasmic fabric. Distribution patterns are agglomeroplasmic to porphyroskelic and granular.Clay mineralogy was determined by x-ray diffractometry and the result reveals that the soils are mostly dominated by kaolinite and quartz.Macromorphologically, the soils are very deep, well drained and coarse to medium textured with granular and medium subangular structures.The occurrence of ferriargillans in the B-horizon is a strong indication of pedotranslocation. Other contemporary processes or regrouping phenomena are pedotranslocation, pedoturbation, pedocompaction and pedotransformation of minerals. The role of clay mineralogy type in soil erosion problems is discussed.     

Influence of parent sediments on the concentration of heavy metals in urban and suburban soils in Turku,Finland

The purpose of this study was to examine the influence of parent sediment material on soil geochemistry and to locate possible pollution sources in the area of Turku town in southwestern Finland. The study area is glaciated terrain and subsurface samples were chosen to represent five different parent sediment materials: glacial till, glaciofluvial or littoral sand, clay, peat and marine mud. Elemental concentrations of surface (100 samples) and background soil (50 samples) were analysed by ICP-AES (Al, Ba, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Sr, Ti, V) and by graphite furnace AAS (As, Cd, Mo, Se). Loss-on-ignition was determined as an indicator of organic matter. Analytical results were examined using multivariate statistical methods. The results indicate that the studied soils are not heavily contaminated; there were only few sample sites with elevated heavy metal concentrations. High Pb concentrations were observed along main traffic routes, and also in places where there has been small-scale use of antifouling paints. However, concentrations of heavy metals in topsoil were in general significantly lower than those measured in large cities elsewhere. The parent material strongly affects the geochemical character of the soils. Clays naturally have a significantly higher concentration of heavy metals than sands or till material. This is also reflected in concentrations in organic topsoil. When assessing target levels for polluted soil, the primary sediment appears to be a more important factor than the amount of organic matter.     

含水率对加筋膨胀土强度的影响

通过室内加筋三轴剪切试验,得出最优含水率附近两种不同含水率的加筋膨胀土的应力-应变关系曲线。分析试验曲线可知,相同含水率时试样的强度随着加筋层数、周围压力的增加而增大;同围压、同加筋层数的试样的含水率略微的减少,引起强度明显的增加,表明加筋膨胀土强度的水敏感性。     

A study of the gully phenomenon in Gombe Town,Bauchi State: Bedrock geology and environmental implications

In Gombe, Bauchi State, Nigeria, gullies are sculptured in the Upper Cretaceous Pindiga Formation and Gombe Sandstones. The former is a sequence of marine shales with limestone interbeds, the later is a sequence of sandstone, siltstone, and shales. Both formations have ironstone cappings. The degree of gully development, the gravity of attendant soil wastage, and environmental hazards are all related to the rock types in which the gully have formed. Hence, the most grievous situations are posed by gullies in the shale/clay member of the Gombe Sandstone and in the shale/clay/limestone units of the Pindiga Formation. An undercut and collapse model is put forward to explain gully initiation and propagation in Gombe.     

Organic matter and nutrient contents of soils under four types of bush fallow vegetation in SW Nigeria

The organic matter and nutrient contents of soils under four types of bush fallow in a part of the forest zone of SW Nigeria were analysed. The soils were formed from the same parent material of sandstone. The fallows studied were: 1) grass, 2) forb, 3) forb/woody and 4) woody fallows. The total nitrogen and organic matter contents and the cation exchange capacity values of soils under the forb/woody and woody fallow on the one hand were higher than those of the grass and forb fallow on the other. This is due to the greater age, biomass and greater capacity of the forb/woody and woody fallows to generate litter and to protect the soil against organic matter diminution through erosion and thermal decomposition. Of the four fallow types, the woody had the highest organic matter and nitrogen contents and cation exchange capacity. The fallows exert differential effects on soil mineral-nutrients. Compared to the woody fallow, there was a build-up of exchageable calcium in the topsoils of the grass and forb fallow. In contrast, there was a marked accumulation of exchageable sodium and potassium in the topsoils of the forb/woody and woody fallows. The woody and the grass or forb fallows appear to complement one another in restoring soil organic matter and nutrient content after cropping. It is suggested that the woody fallow should be alternated with grass or forb fallow in order to maintain the balance of soil nutrients over time.     

Assessing lithologic discontinuities and parent material uniformity within the Texas sandy mantle and implications for archaeological burial and preservation potential in upland settings

Alfisols within the Texas Gulf Coast Plain commonly exhibit textural contrasts between sandy, artifact-bearing A–E horizons (i.e., sandy mantle), and artifact-sterile clay-rich Bt (argillic) horizons. This has invoked debate about parent material uniformity and pedogenic versus geomorphic sandy mantle origins, which has implications for the scientific value of buried archaeological sites. To improve our understanding of archaeological burial in upland settings, we evaluated parent material uniformity within five pedons to distinguish pedogenically derived textural changes from geomorphologically created lithologic discontinuities. Depth trends in clay-free particle size classes and stable/immobile Ti and Zr constituents failed to reveal lithologic discontinuities between the sandy mantle and Bt horizons, and the observed textural differences are interpreted to have resulted from pedogenic processes. This interpretation is supported by clay skins, fine clay increases in Bt horizons, and micromorphological observations. Consequently, artifacts buried in upland summits have likely moved down the soil profile due to biomantle processes. Deep sandy mantle sites, non-parallel contacts between the sandy mantle and Bt horizons, and paleogullies incised into Eocene bedrock are better explained by colluvial/soil creep processes adjacent to summits, where archaeological materials may exhibit preservation potential. No single explanation can account for sandy mantle origins, and we advocate a case-by-case approach.     

长三角湖州市土壤磁化率与铜、锌有效量和全量分布规律

通过对84个地表土样、17个剖面土样和11个基岩样的磁参数与化学分析测试,对湖州市土壤磁化率与重金属元素Cu、Zn有效量和全量分布规律、成因及两者的相关性进行了研究.研究发现:①表层土壤磁化率高值异常区总体上与土壤重金属元素Cu、Zn有效量和全量高值分布区吻合程度非常高;剖面土壤磁化率值与Cu、Zn有效量和全量含量总体上均呈现出向下递减的相同特点.②表层土壤磁化率与Cu、Zn有效量和全量高值异常均系人类经济工程活动影响所致,主要与当地城镇生活垃圾随意堆放、垃圾施肥、工业"三废"排放、农药和化肥的过量使用等有关.③表层土壤磁化率值与重金属元素Cu、Zn有效量和全量含量之间在不同环境条件下相关性存在明显差异.     

The distribution of soil erosion as a function of slope aspect and parent material in Ciskei,Southern Africa

The paper investigates the relationship between geology, soils and slope aspects in four Ciskei catchments. The primary aim of the study was to determine whether any simple bivariate relationship exists between these independent variables and soil erosion. The secondary aim of the study was to determine whether combining the three independent variables and using a multivariate analysis could produce a more lucid picture of spatial variations in soil erosion. The results obtained from the study show that all the three independent variables (geology, soil type and slope aspects) can be used to account for spatial variations in soil erosion in the study catchments. A parent material classification (based on geology and soil type) and a parent material plus slope aspect classification provide more detailed explanation for variations in the extent of soil erosion in the study area. The paper discusses possible reasons for the observed relationships and the need for more detailed multivariate investigations.     

Origin of high Zn contents in Jurassic limestone of the Jura mountain range and the Burgundy: evidence from Zn speciation and distribution

In order to better understand the origin and enrichment mechanisms leading to elevated Zn concentrations in Jurassic limestone of the Jura mountain range (JMR) and the Burgundy (B), we investigated four locations of Bajocian age (JMR: Lausen–Schleifenberg, Gurnigel; B: Vergisson–Davayé, Lucy-le-Bois) and two locations of Oxfordian age (JMR: Dornach, Pichoux) for their Zn distribution and speciation. Measurements of the acid-extractable and bulk Zn contents showed that Zn is stratigraphically and spatially heterogeneously distributed, in association with permeable carbonate levels. Up to 3,580 and 207 mg/kg Zn was detected in Bajocian and Oxfordian limestone, respectively, with numerous limestone samples having Zn contents above 50 mg/kg. Using X-ray absorption near edge structure spectroscopy and micro-X-ray fluorescence spectrometry, the speciation and micro-scale distribution of Zn was investigated for selected limestone samples. In Bajocian limestone sphalerite and/or Zn-substituted goethite and a minor fraction of Zn-bearing carbonates were identified. In contrast, Zn-bearing carbonates (Zn-substituted calcite and hydrozincite) were accounting for most of the total Zn in Oxfordian limestone. The micro-scale distribution of Zn for Bajocian and Oxfordian limestone was however similar with localized Zn-rich zones in the limestone cement and at the rim of oolites. The stratigraphic sporadicity and microscale heterogeneity of the Zn distribution together with the Zn speciation results point to a hydrothermal origin of Zn. Occurence of Zn-goethite is probably linked to the oxidative transformation of framboidal pyrite and hydrothermal sphalerite in contact with meteoritic waters. Difference in speciation between Bajocian limestone and Oxfordian limestone may be related to differences in rock permeability and/or to various hydrothermal events. Isotopic dating of the different mineralizations will be needed to decipher differences in Zn speciation and the precise chronology of hydrothermal episodes.     

Soil parent materials and soil properties in two separate catchment areas on the Jos Plateau, Nigeria

On the Jos Plateau, soils derived from basalt and volcanic ash are much more intensively and extensively utilized for agricultural purposes than the granite soils. This study was carried out to determine the differences that may have contributed to this discrimination. Twenty four soil profiles were dug and described in two separate catchment areas that really portray the variance. Soil samples were analysed using standard procedures. The results show that basalt and volcanic ash-derived soils have relatively deeper profiles, lower bulk density, higher contents of clay, organic matter, exchangeable bases, micro-nutrients (Cu & Zn) and weatherable minerals. They are also higher in their CEC and base saturation percentage while available water capacity, hydraulic conductivity and natural water content are more adequate in them. Hence, the basalt and volcanic ash soils are more favourable for crop growth while the deficiencies in granite soils present more constraints to agricultural land use. Consequently, there are differences between the soil types in their crop-yielding capacities. These differences constitute a reflection of soil parent material influence. Agriculture in the area is mainly low-input. There is the need for improved management practices for the enhancement of soil conditions of granite areas in particular and the whole area in general. This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial distribution mapping and radiological hazard assessment of groundwater and soil gas radon in Ekiti State,Southwest Nigeria

Groundwater constitutes the major source of utility water in Ekiti State with the majority of the population depending on groundwater for drinking and other household uses. Soil in the area is commonly used as a component of building materials, which may produce radon in the indoor environment. Excessive concentrations of radon in water and soil can cause radiological health risks to human as witnessed by the increased cases of lung cancer among non-smokers in Nigeria, which may be traceable to the ingestion and inhalation ²²²Rn in drinking water and indoor air. In the present study, comparative in situ measurements of radon in groundwater and soil gas were carried out at one hundred selected locations across the Ekiti State in southwest Nigeria, using a RAD7 radon detector to generate a radon distribution map and to estimate radiation hazards due to radon. The concentrations of radon in groundwater ranged from 0.9 to 472 Bq L^?1 with a mean of 34.7?±?4.4 Bq L^?1, while those of soil gas ranged from 0.1 to 315 kBq L^?1 with a mean of 38.9?±?1.4 kBq L^?1. The total annual effective dose due to inhalation and ingestion of radon in groundwater amounted to 94.7 µSv year^?1, which is lower than the reference dose of 100 µSv year^?1 recommended by the World Health Organization (WHO). The radon map generated for groundwater and soil gas identified three distinct areas with radon levels ranging from low to high. The results of this study show that some locations (Emure, Gbonyin, Ijero and Ikole) show mean total annual effective doses which are higher than the recommended limit. It can then be inferred that the groundwater samples pose significant radiological hazards to the population and that the noticed increase in lung cancer cases may be attributed to the consumption of groundwater in the area.     

The nature and distribution of Cu,Zn, Hg,and Pb in urban soils of a regional city: Lithgow,Australia

This study investigates the concentration and spatial distribution of Cu, Zn, Hg and Pb in the surface (0–2 cm) soils of a regional city in Australia. Surface soils were collected from road sides and analysed for their total Cu, Zn, Hg and Pb concentrations in the <180 μm and <2 mm grain size fractions. The average metal concentration of surface soils, relative to local background soils at 40–50 cm depth, are twice as enriched in Hg, more than three times enriched in Cu and Zn, and nearly six times as enriched in Pb. Median surface soil metal concentration values were Cu – 39 mg/kg (682 mg/kg max), Zn – 120 mg/kg (4950 mg/kg max), Hg – 44 μg/kg (14,900 μg/kg max) and Pb – 46 mg/kg (3490 mg/kg max). Five sites exceeded the Australian NEPC (1999) 300 mg/kg guideline for Pb in residential soils. Strong positive correlations between Cu, Zn and Pb, coupled with the spatial distribution of elevated soil concentrations towards the city centre and main roads suggest traffic and older housing as major sources of contamination. No spatial relationships were identified between elevated metal loadings and locations of past or present industries.     

Assessment of heavy metal contamination in soils around lead (Pb)-zinc (Zn) mining areas in Enyigba,southeastern Nigeria

Mining activities have been undertaken for over 95 years in Enyigba area of southeastern Nigeria. In this area, thirty-six (36) trace metals including those that are essential for plant and animal nutrition have been analyzed from forty-nine (49) soil samples that were collected from three Pb-Zn mines. The aim of the analysis is to assess the level of contamination of the soils caused by mining activities. Potentially harmful elements which are commonly associated with Pb-Zn mines were of special interest. Such elements included Pb, Zn, As, Cd, Mn, Fe, Se, Sb, Cu and Bi. Generally, the samples analyzed showed elevated concentrations of Pb, Zn, Cd, Cu and Cr when compared with concentrations documented in the international agricultural soil standards. Geo-accumulation indices of soils that occur closer to the mines indicate moderate to extreme level of contamination in Pb and moderate levels in Cd. Enrichment factor (EF) showed very high enrichment to extremely high enrichment in Pb. Cd and Zn enrichment were found to be significant and moderate respectively. Conversely, the geo-accumulation indices for soil samples located away from the mines indicate moderate to heavy contamination in Pb but had moderate to significant enrichment in Cd and moderate in Bi and Cr. In general, soil quality all around the mines were found to have deteriorated as revealed by the pollution load index. Thus the results of this study call for immediate remedial measures to be initiated. In addition, miners and local communities living around the mines need to be enlightened about the dangers of exposure to these heavy metal contaminants.     

Slump debris flows in the Akovolwo Mountains area of Benue State,Nigeria

In September 1979, rain-induced complex landslides occurred in two separate localities along the slopes of the Akovolwo Mountains near Jato-Aka in the Kwande Local Government area of Benue State, Nigeria.The two movements developed on bedrock slopes covered by a veneer of colluvium and (or) residuum no more than 1.5 to 2m deep. Each started as a slump and graduated into a debris flow. The slump, extending downhill a short distance away from the head scarp, had been reconstituted into a debris flow as the initial movement (sliding movement) of the soil mass caused remoulding of the saturated moving mass into viscous debris-laden mud. The resulting mass moved partly along a pre-existing mountain stream channel and partly along a fresh channel it cleared in the savanna forest. At the break of slope, the mass of boulders was dumped and a trail of smaller fragments littered the channels towards the Katsina-Ala River.     

Local coordination of Zn in hydroxy-interlayered minerals and implications for Zn retention in soils

The objective of this study was to determine the local coordination of Zn in hydroxy-interlayered smectite (HIS) as a function of Zn loading and synthesis conditions and to assess the importance of hydroxy-interlayered minerals (HIM) for Zn retention in contaminated soils. Published and newly collected extended X-ray absorption fine structure (EXAFS) spectra of HIS reacted with Zn at molar Zn/hydroxy-Al ratios from 0.013 to 0.087 (corresponding to final Zn contents of 1615-8600 mg/kg Zn) were evaluated by shell fitting. In Zn-HIS, Zn was octahedrally coordinated to oxygen at 2.06-2.08 Å and surrounded by Al atoms at 3.03-3.06 Å in the second-shell. With increasing molar Zn/hydroxy-Al ratio, the coordination number of second-shell Al decreased from 6.6 to 2.1. These results were interpreted as a progressive shift from Zn incorporation in the vacancies of gibbsitic Al-polymers to Zn adsorption to incomplete Al-polymers and finally uptake by cation exchange in the polymer-free interlayer space of HIS with increasing Zn loadings. In a second part, we determined the speciation of Zn in eight contaminated soils (251-1039 mg/kg Zn) with acidic to neutral pH (pH 4.1-6.9) using EXAFS spectroscopy. All soils contained hydroxy-Al interlayered vermiculite (HIV). The analysis of EXAFS spectra by linear combination fitting (LCF) showed that a substantial fraction of total Zn (29-84%) was contained in HIM with high Zn loading. The remaining Zn was adsorbed to organic and inorganic soil components and incorporated into phyllosilicates. In sequential extractions of Zn-HIS spiked into quartz powder and the Zn contaminated soils, Zn was mainly released in the two most resistant fractions, in qualitative agreement with the findings from LCF. Our results suggest that formation of Zn-HIM may strongly retain Zn in pristine and moderately contaminated acidic to neutral soils. Due to their limited sorption capacity, however, HIM do not allow for the accumulation of high levels of Zn in response to continued Zn input into soils.     

Women's status, environmental changes and child health in the riverine area of Ondo State, Nigeria

The viewpoint that most health problems are environmentally related has always been promoted by medical geography. In recent times, concern about environmental degradation has been of high priority for many national and international organizations as ‘we human beings become a threat to our planet’. There is also a need to specifically focus attention on the impact of so-called development efforts on the health of women and children, in particular those living in highly marginalized regions which often contribute substantially to the overall development of their countries. This paper uses the concept of vulnerability as a departure point from which to map the health risks to children in Igbekun area of Ondo State, the ‘transgressive muddy’ oil-rich coastal area of Nigeria. The paper attempts to highlight the poor quality of life and health of children in particular, and how it is becoming much more difficult to practice health intervention programmes, especially oral rehydration therapy (ORT) in the area. The Igbekun area is an unhealthy and harsh environment, complicated by the devastating effects of oil drilling in recent years. The siltation and sedimentation of the creeks and lagoons have serious health dimensions as human faeces float in and around villages because the ‘bush toilets’ can no longer be reached. The on-going environmental crisis has also deprived women of their traditional means of livelihood; fishing. There is a relatively high level of ignorance (compared with other women living in the same local government area (LGA) of causes of the commonest diseases such as diarrhoea, acute respiratory infection (ARI) and measles. A majority of the women have never heard of family planning, immunization against diseases and interventions such as ORT. Promotive health care services, especially those that strive to reduce the high mortality of children have passed the mothers by. It is also becoming impracticable to promote ORT because of the widespread ‘salty and oily’ water supply in the area. The greatest concern of the women now is that oil drilling activities have further amplified their stressful conditions especially their health and that of their children. Unfortunately, their plight is not acknowledged by the Nigerian authorities and the oil companies are least concerned about alleviating the poor health status of the community, in particular the most vulnerable groups, children under the age of five. This revised version was published online in August 2006 with corrections to the Cover Date.     

Distribution of heavy metals in soils of Port Harcourt and its environs,Niger Delta,Nigeria

Geochemical evaluation of the distribution of heavy metals in soils of Port Harcourt and its environs in the Niger Delta region is presented in respect of anthropogenic factor and index of geoaccumulation. Sixteen (16) soil samples were collected from two horizons (0-10 cm and 100 cm) from the various grids and analyzed. The geo-chemical analyses showed the vertical and horizontal distributions of heavy metals. The results showed the ranges of the metals determined as follows: Pb (6.86-2.49)×10-6, with an average of 4.63×10-6; Cd (0.05-0.00)×10-6, with an average of 0.02×10-6, As (0.01-0.00)×10-6, with an average of 0.00×10-6. Cu (15.36-10.80) ×10-6, with an average of 13.36×10-6, and V (1.36-0.20)×10-6, with an average of 0.94×10-6. Quantification of the degree of pollution was carried out using anthropogenic factor (AF) and index of geoaccumulation (Igeo). The Igeo values of 0.06, 0.02 and 0.00 for Pb, Cd and As, respectively indicate low-level contamination while Zn (1.14) and V (1.40) show me-dium-level contamination. The sources of contamination are attributed to urbanized anthropogenic activities. The majority of the samples analyzed show that the AF values are less than 1 with the exception of vanadium (V) whose AF values range from 2.73 to 13.60×10-6. Vanadium is more enriched than As, Cd, Pb, and Cu. The order of degrees of anthropogenic contamination and index of geoaccumulation in the soil is V >Zn >Pb >Cu >Cd >AS. Metals were retained near the top soil and their concentrations in the deepest horizons were lower and normal for uncontaminated soils. Metal concentrations in the top soil horizons were significantly related to distance from the industrial and hu-man activities.     

The stability of the relative content ratios of Cu,Pb and Zn in soils and sediments

The study indicates that the relative content ratios of Cu, Pb and Zn in soils and sediments tend to have stability compared to those in meteorites, rocks and organisms. This stability is considered to be associated with their geochemical properties and has no relationship to the existing environments if it is not disturbed by an anthropogenic factor. In addition, it can serve as a background reference in determining the changes in environmental quality due to human activities.