摘要
The measurement of environmental magnetic properties and metal contents of sands from Nukkai(NKR),Mayo-Gwoi(RMYG)and Lamurde(LR)rivers located in Jalingo,Nigeria are reported.We seek to determine the extent of anthropogenic impact on the river sands using magnetic-proxy-parameters,pollution and ecotoxicological indices and multivariate statistics.Measurements of magnetic susceptibilityχ,frequency-dependentsusceptibilityχfd%,anhystericremanent magnetization,isothernal remanent magnetization and X-ray fluorescence were undertaken.The average values of theχ(in×10^(-8)m^(3)kg^(-1))were 24.53,12.76 and 39.27 for NKR,RMYG and LR sites respectively,implying that the magnetic minerals in the sands were mostly ferrimagnetic.The meanχfd%value of 2.64%,4.85%and 3.53%for NKR,RMYG and LR respectively suggest that the study area was dominated by multi-domain magnetic grain sizes.The value of the S-ratio is~1 in all river samples,suggesting that low coercivity magnetic minerals(e.g.,magnetite)dominated the samples.The mean concentrations of Ti,Zr,Sn,Ba and Pb were higher than the background values in the studied samples.All the estimated pollution indices puts the level of pollution of the river sands between low and moderate pollution with Sn,Ba and Pb as the elements of concern.Multiple sources of metal contents such as fertilizers,pesticides,waste dumps and vehicular sources etc.were found.Significant positive correlations between magnetic parameters(particularly,SIRM)and some heavy metals and pollution/ecotoxicological indices were obtained,showing that magnetic methods could be used as a geochemical proxy for pollution assessment.
