Levels of Arsenic and Other Trace Elements in Southern Libyan Agricultural Irrigated Soil and Non-irrigated Soil Projects

Abstract

The levels of As and various other trace elements found in the irrigated agricultural soil (T soil ) of southern Libya were compared with non-irrigated soil (C soil ) from the same sampling campaign collected between April and May 2008. The soil samples represented agronomic practice in the southern Libyan regions of Maknwessa (MAK), Aril (ARL) and Taswaa (TAS), and were analyzed by Inductively coupled plasma mass spectrometry (ICP-MS) for Co, Ni, Cu, Se, Mo, Zn, As, Pb, Cd and P. Concentrations of P and As in TAS and MAK were found to be higher in T soil compared to C soil , while the opposite was true for ARL. In general, As concentrations in these areas were 2-3 times lower than the global average. In ARL, the average P concentrations of the C soil samples were significantly higher than those of T soil samples: this site is composed mainly of pasture for animal production, where phosphate fertilizers are used regularly. Distance from the source of irrigation was found to be of an important influence on the heavy metal concentration of the soil, with greater concentrations found closer to the irrigation source. It can be concluded from the results that irrigation water contains elevated levels of As, which finds its way into the soil profile and can lead to accumulation of As in the soil over time.

Understanding arsenic dynamics in agronomic systems to predict and prevent uptake by crop plants

“…Outputs include leaching into water bodies (vertically and horizontally), soil erosion 25 and biovolatilization 27 . In arid regions surface evaporation of water can lead to arsenic enrichment from the draw up of subsurface water 25 and from waters used in crop irrigation 28 . Mass-balances (accounting for all inputs and outputs for a particular ecosystem) are rarely conducted for arsenic fluxes within catchment areas, but a good example is from a mining-impacted catchment area 29 , where chemical weathering, followed by mechanical weathering dominated arsenic inputs, which were primarily from arsenopyrite.…”