Spatial variability of trace metals in Podzols of northern forest ecosystems: Sampling implications

Abstract

. 2003. Spatial variability of trace metals in Podzols of nothern forest ecosystems: Sampling implications. Can. J. Soil Sci. 83: 581-587. The concentrations of metals in soils are spatially heterogeneous and soil sampling carried out when studying metals in forest ecosystems is often inadequate. We examined the spatial variability of Cd, Cu, Mn, Ni, Pb and Zn in northern forest ecosystems on a transect with distance from two point source emitters with the goal of providing basic information about the distribution and variability of metals in these soils. Samples were taken under six sampling points at four depths from three experimental sites on each of the two transects. Soils were analysed for acid digestible metals, pH and organic carbon content. Standard deviation, coefficients of variation, mean and medians were analysed for each horizon of each site. It was observed that Cu and Mn variability is higher in closer proximity to the point source while the variability of Zn increased with decreasing soil pH. In Sudbury, emitted metals Ni and Cu accumulate together in soils, whereas in Rouyn-Noranda, with the exception of Cd and Zn, metal concentrations were not related in forest floors. Observations suggest that physical factors influencing where metals are deposited as well as the inherent variability in soil chemical characteristics, and the distance from the point source can all act together to result in high variability in soil metal concentrations in a single forest site. Sampling in the interest of relating vegetation metal concentrations or response to soil metals should be carried out on an individual plant basis with multiple samples taken for each individual. Soil samples taken at intervals of 1 to 1.7 m will provide relative error in estimating soil concentrations of 10% or 20%, respectively. Nous avons examiné la variabilité spatiale du Cd, Cu, Mn, Ni, Pb et Zn dans les écosystèmes des forêts nordiques à des distances croissantes à partir de deux sources distinctes dans le but de fournir de l'information de base sur la distribution et la variabilité des métaux dans ces sols. Des échantillons ont été pris en six points d'échantillonnage à quatre profondeurs différentes dans chacun de trois sites expérimentaux sur les deux sections transversales. Les sols ont été analysés pour leur contenu en métal par digestion acide, leur pH et leur concentration en matière organique. Pour chaque paramètre, l'écart type, le coefficient de variation, la moyenne et la médiane ont été estimés dans chaque horizon de chaque point de l'échantillonnage. Nous avons observé que la variabilité de Cu et de Mn est plus haute dans une proximité plus étroite de la source d'émission tandis que la variabilité du Zn augmentait avec une diminution du pH du sol. À Sudbury, les émissions des métaux Ni et Cu s'accumulent ensemble dans les sols, tandis qu'à Rouyn-Noranda, cette tendance n'est pas observée dans la couche organique du sol forestier, sauf dans le cas du Cd et du Zn. Les observations suggèrent que les facteurs physiques qui...

High variability of the metal content of tree growth rings as measured by synchrotron micro x‐ray fluorescence spectrometry

“…The trace metals within the soils at the six sampling sites were studied extensively by MacDonald and Hendershot. 40 Overall, they found that along the transect from the INCO nickel smelter (Sudbury), both copper and nickel were elevated in the soil, with the concentrations of total metal and exchangeable metal decreasing with distance away from the smelter. The site closest to the nickel smelter (S-1) was the only site to have been treated with remedial applications of CaCO 3 , which was used to raise the soil pH.…”

“…Whereas the concentrations of both total and exchangeable copper and nickel in the soil increased with proximity to the nickel smelter near Sudbury, 40 only the elevated nickel was detected in the tree rings ( Fig. 4).…”

“…The pH and spatial variability of the trace metals at these sites have been described by MacDonald and Hendershot. 40 Paper birch, Betula papyrifera Marsh, was selected because it represented the only tree species which was sufficiently abundant at all the sites. Samples were collected at breast height (120 cm) using a Haglof increment borer.…”

Soil Sampling and Sample Preparation

“…Obtaining a representative field sample presents specific problems which, if ignored, may render all subsequent analytical work worthless [5]. The analytical significance that can be associated with spatial heterogeneity in metal distribution is large as recently demonstrated for forest ecosystems [6]. Analytical uncertainty generally develops from inadequate soil sampling strategies.…”

Determination of exchangeable hydrogen ions in boreal shield soils of Quebec

“…One to two F, H or FH samples and one podzolic B sample in each plot were selected randomly for exchangeable H + analysis. The study in Rouyn is also part of a larger study investigating trace metal contamination in soils from anthropogenic point source emitters (MacDonald and Hendershot 2003).…”