RESUMEN
The study of trace and major elements in the biosphere has traditionally focused on the transition and basic metals; the rare earth (REMs), alkaline earth (AEMs) and alkali metals (AMs) that equally constitute environmental contaminants are rarely considered especially in the tropics. The levels and spatial variation of some REMs, AEMs and AMs in the 0-50-cm layer of agricultural soils of Ikwo in southeastern Nigeria typing a humid tropical environment were studied. Soil sampling was undertaken at five zones namely north, south, east, west and centre (covering over 60% of the land area) in the 2017 dry season. Four soil samples were collected from each of the four cardinal points (with evidence of mining and agricultural activities), and two from the centre (serving as reference zone), totalling 18. Metal concentrations were determined using inductively coupled plasma atomic emission spectroscopy. The metals were grouped into REMs (Ce, La, Sm), AEMs (Ba, Ca, Mg, Sr) and AMs (Cs, K, Na, Rb). All metals increased in concentration from the north, or the south (for Ce and Sm only), towards the centre. Overall, they were reasonably similar in distribution pattern among the five zones. Cationic ratios did not vary markedly, reflecting the greater role of pedogenesis than anthropogenic activities in the area. Nevertheless, their variations showed more K, Ca, Sr and La enrichments over the other metals. Enrichment factor and pollution index of the REMs showed healthy levels of these elements in the soils. The data from this preliminary study may add to the data pool on levels and occurrence of REMs, AEMs and AMs in largely disturbed ecosystems of the humid tropics.
Asunto(s)
Metales Alcalinos , Metales Pesados/análisis , Contaminantes del Suelo/análisis , Ecosistema , Monitoreo del Ambiente , Nigeria , Rizosfera , SueloRESUMEN
An imbalance in the environment's composition leads to significant effect on human activities such as farming. Of importance are heavy metals which are introduced anthropogenically or naturally. This calls for environmental monitoring and subsequent remediation if needed. An environmental monitoring exercise was conducted on Ikwo soils of Ebonyi State, eastern Nigeria with the aim of determining concentration levels for possible remediation. A total of 18 soil composite samples taken at 0-50 cm below soil surface from fallowed and cultivated soils not fertilized were subjected to heavy metal analyses and fertility indices like: organic matter (OM), cation exchange capacity (CEC), % total nitrogen (%TN), organic carbon (OC), and salinity. A correlation at 95% confidence level between geo-accumulations (Igeo) of the various heavy metals with salinity, OM, and CEC of the sampled soils reveals that Igeo could be a contributing factor to the fertility status of the soils. With the aid of inductively coupled plasma atomic emission spectrophotometer (ICP-AES), the distribution pattern was determined as Mn> Fe> Zn>Cu> Mo> Cd> V>Hg>Ti> Ni>Bi> Pb> Co>Ag>Au> Cr>Pd>Pt. The Igeo of the heavy metals in the study area varied from heavily to extremely contaminated levels. A remediation exercise was recommended on Ikwo soils due to their high salinity level and low CEC.