Weathering and accumulation of trace elements in the soils of the Porali Plain, Balochistan: repercussions in agriculture

Abstract

This study is the first attempt to assess the nature of the soil, especially on the western side of the Porali Plain in Balochistan; a new emerging agriculture hub, using weathering and pollution indices supplemented by multivariate analysis based on geochemical data. The outcomes of this study are expected to help farmers in soil management and selecting suitable crops for the region. Twenty-five soil samples were collected, mainly from the arable land of the Porali Plain. After drying and coning-quartering, soil samples were analyzed for major and trace elements using the XRF technique; sieving and hydrometric methods were employed for granulometric analysis. Estimated data were analyzed using Excel, SPSS, and Surfer software to calculate various indices, correlation matrix, and spatial distribution. The granulometric analysis showed that 76% of the samples belonged to loam types of soil, 12% to sand type, and 8% to silt type. Weathering indices: CIA, CIW, PIA, PWI, WIP, CIX, and ICV were calculated to infer the level of alteration. These indices reflect moderate to intense weathering; supported by K₂O/AI₂O₃, Rb/K₂O, Rb/Ti, and Rb/Sr ratios. Assessment of the geo-accumulation and Nemerow Pollution indices pinpoint relatively high concentrations of Pb, Ni, and Cr concentration in the soils. The correlation matrix and Principal Component Analysis show that the soil in this study area is mainly derived from the weathering of igneous rocks of Bela Ophiolite (Cretaceous age) and Jurassic sedimentary rocks of Mor Range having SEDEX/MVT type mineralization. Weathering may result in the undesirable accumulation of certain trace elements which adversely affects crops.