Portable XRF (PXRF) Analysis of Agricultural Soils in Central Bangladesh - Approaches to Quantify Anthropogenic Trace Element Inputs

The widespread distribution, non-degradable nature, and detrimental effects of many trace elements (TEs) render a significant ecological and public health issue on a global scale (Zhao et al., 2014). TEs in soil may have geogenic or anthropogenic origins – quantifying the latter may be of considerable utility in (a) identifying sources; and (b) rapid qualitative risk assessments in the absence of detailed mineralogical and petrographic data. Bangladesh, one of the world’s most densely and highly populated countries, though agriculturally intensive, has numerous sources of soil TEs pollution, particularly in the highly urbanised and industrialised Dhaka-Gazipur-Narayanganj corridor (Islam et al., 2024).

In this study, PXRF was used to semi-quantitatively analyse a range of agricultural soils from central Bangladesh, with a view to quantifying and determining the spatial distribution of TEs of anthropogenic origin. Soil samples (n = 102) were collected from agricultural lands in seven districts of central Bangladesh across 8 different river plains (Meghna, Dhaleshwari, Old Brahmaputra, Buriganga, Ichamoti, Kaliganga, Shitalakshya, and Turag River). Soil samples were analysed by PXRF for trace element content, and the method was validated by using Certified Reference Materials (CRMs: NCS DC73309, NIST 2710A and NIST 1646A). The recovery rates for trace elements were within acceptable limits (< 100 ± 20%). Recovery rates for Si and Al were poor, and the estimated SiO₂ and Al₂O₃ were assessed from measured Rb using the relationships identified for Meghna River sediment by Hossain (2019). The concentration range of trace elements (in mg/kg) in agricultural soil were found as 10 – 65 (Pb), 5 – 20 (As), 30 – 300 (Zn), 15 – 70 (Cu), 15 – 75 (Ni), 8 – 25 (Cd), 40 – 150 (Cr), 40 – 200 (V), 10 – 40 (Sb), 8 – 35 (Sn), 21000 – 60000 (Fe), 150 – 1000 (Mn), 2100 – 5700 (Ti), 1600 – 73000 (Ca), 8300 – 27000 (K), 2700 – 17000 (Mg), 125 – 520 (Zr), 30 – 200 (Sr), 70 – 180 (Rb), 10 – 25 (Nb) and 10 – 30 (Th). FAO guideline values for soils (FAO, 2004) were found to be exceeded, notably for Sn (58 % of samples), Cr (47 %), V (32%), Sb (27%), Cd (20%), Ni (15%) and Pb (2%). Preliminary qualitative determination of anthropogenic contributions to the soils was made following corrections for (a) grain size, and (b) river-valley-dependent provenance of geogenic sources and notably identified some soils for which Cr and/or Pb in particular were predominantly of anthropogenic origin.  Further analysis will be carried out to enable more detailed TEs source apportionment.

 

Keywords: Agriculture, Soil quality, Trace elements contamination, Portable XRF.

Acknowledgement: FTA acknowledges a STFT, Ministry of Science and Technology (Bangladesh) scholarship. AR acknowledges a Cookson Scholarship. RC acknowledges a PGRTA Studentship from the University of Manchester (UoM).  We thank all the technical support staff in the Manchester Analytical Geochemistry Unit at the UoM for the PXRF and laboratory facilities. 

References

1. Zhao et al. (2014). https://doi.org/10.1016/j.scitotenv.2013.09.086  
2. Islam et al. (2024).  https://doi.org/10.1016/j.envres.2024.118551    
3. Hossain  (2019). https://doi.org/10.1002/gj.3595   
4. FAO (2004). https://faolex.fao.org/docs/pdf/est97999E.pdf