Multi-Metal Distribution Patterns in Soils of the Sacramento River Floodplain and Their Controlling Factors

Abstract

Metal contamination, especially in river floodplain soils, can have detrimental effects on human health. Much research has been conducted to describe the distribution patterns of metals and the factors involved in these patterns. However, most studies focus on the distribution of individual metals in soils, not on the co-occurrence of metals, and on a selection of metals associated with anthropogenic sources known to have especially severe effects; this had led to a lack of knowledge about many other metals with potentially harmful effects. Therefore, this study aimed to identify the multi-metal distribution patterns of 38 metals in the Sacramento River floodplain and find their controlling factors. We found 484 significant correlations between metal distributions. Less commonly studied metals, such as gallium, lanthanum, scandium, and vanadium, had more than 25 correlations each. In total, 13 individual metal patterns described the spatial distribution of 22 metals. Three multi-metal patterns were extracted, explaining 86.9% of the spatial variation of the individual patterns. The most important factors were the distance to specific streams due to emission and transport processes in their watersheds, and local soil properties. We conclude that multi-metal distribution patterns hold more information than individual metal patterns, contributing to the gathering of information about less commonly sampled metals and allowing more specific source identification.