Lead isotopic and metallic pollution record in tree rings from the Copperbelt mining-smelting area, Zambia

Martin Mihaljevič,

Vojtěch Ettler, Ondřej Šebek, Ondra Sracek,Bohdan Kříbek, Tomáš Kyncl, Vladimír Majer, František Veselovský

Windhoek 2012

Goals

This work was performed in order to determine, through comparison

of dendrochemistry and the soil composition, whether the source of these

substances in the pine-tree xylem is interception or root uptake and the degree

to which the studied tree species are affected by industrial activities, transportation

or natural processes.

Introduction

Extraction and processing of Cu ores in the Zambian part of the Copperbelt is

accompanied by significant emissions of Cu, Co, Pb and SO2. Air-borne dust

released from the mines, smelters and transport of concentrates and SO2

from the smelter cause contamination, especially of the surface layers of the

soils, plants and biomass.

Sampling locations of tree rings I, II and III are located in the direction of prevailing winds and, according to the distribution of 6 metals (Kříbek et al, 2010), are affected by the ore processing.

Location IVlow contents of metals in upper soil layers

Material and methods

Tree rings – Pinus LatteriHaglof Incremental Borer (diameter 5 mm), 3-year segments, digestion of the individual segments (weights in the range of 0.03-0.2 g) in Savillex beakers in concentrated HNO3 at 150°C

Soilssieving (2mm), milling, pH, TC, TS, dissolution in HF, HClO4.

Analysis of solutions trace elements, and 206Pb/207Pb 208Pb/206Pb ICP MS (X Series 2, Thermoscientific)

Conclusions I

Contamination of the wood by Mn, Co, Cu, and Pb are statistically different at all the sites (p <0,05 one-way ANOVA).

Copper in the tree rings varies in the range 2 – 40 mg kg-1 and is clearly higher in the tree rings in the vicinity of the smelter, showing an increase after 1975.

Cobalt in the tree rings varied in the range 0.05 – 0.07 mg kg-1, is highest close to the smelter, lower close to the highway and lowest in the remote area. Manganese in the pine tree rings varies in the range 5 – 125 mg kg-1.

The maximum Mn content was found close to the highway in the tree rings formed in the period from the mid-1980’s to the mid-1990’s.

The maximum Mn content close to the smelter occurs in the tree rings from the mid-1970’s to the beginning of the 1990’s.

The Pb content in the tree rings is very low and varies in the range 0.02 – 0.7 mg kg-1.

Conclusions II

The isotopic composition of Pb in the soils is different at the contaminated and remote sites.

The effect of Pb with low 206Pb/207Pb derived from combustion of leaded petrol on the composition of the upper soil layers is apparent at the contaminated site.

The soil composition is not affected by automobile lead at the remote (IV) site.

In contrast, the tree rings at all sites have Pb with low 206Pb/207Pb ratio in the youngest parts.

It thus follows that the source of the Pb is probably interception (foliar, bark) uptake of this pollutant by trees.

Lead with low 206Pb/207Pb ratio is not contained in the soil at the remote (IV) site, probably because of frequent fires of biomass litter, plants and bush undergrowth of the studied pine trees.

Acknowledgements:

This work was performed with financial support from the project of the Ministry of Education, Youth and Sports (MSM 0021620855) and the Czech Science Foundation (GA ČR 205/08/0321/1).

Thank you for your attention.

Thanks to Marie Fayadová, Roman Businský, for assistance withlaboratory work and pine determination.