Suitability of magnetic proxies to reflect complex anthropogenic spatial and historical soil heavy metal pollution in the southeast Nile delta

Abstract Magnetic proxy methods are effective tools for detecting anthropogenic heavy metal pollution of the environment. In this study we investigated the viability of using this method in an area of a complex setting where natural geogenic input, interfering land-use, and multiple different industries affect the magnetic signal. For this purpose, we took surface (N = 70) and core (N = 18) samples from an ~80 km2 area in the south-eastern Nile delta that was partly flooded before construction of a major dam, with overlapping agricultural, residential (urbanization and land reclamation), and multiple industrial activities. Using ICP-MS we characterized the spatial pollution pattern and found enrichments in seven potentially toxic heavy metals; Cu, Zn, Pb, As, Sb, Cd, and Hg, located near industrial hotspots, with highly varying pollution levels, high concentrations in the upper soil and clear depletion with depth. Magnetic susceptibility (ϰ) was measured in-situ at 170 sites, and on all samples. Thermomagnetic runs reveal that magnetite and Ti-rich titanomagnetite control the magnetic signal. Despite industrial activities are predominantly located in more sandy areas, and ϰ is found to be strongly related to spatial lithological variation, the magnetic results reasonably outline the industrial areas and show elevated ϰ levels around drains where pollutants are discharged and redistributed by irrigation. In most of these locations, ϰ decreases with depth in parallel with the pollution level, and there is a moderate correlation of ϰ with the pollution load index for the topsoil values of the core samples normalized to their bottom values. Despite the area's complexity, the spatial ϰ pattern matches reasonably well with the chemistry data of cores located in the vicinity of the main industrial spots. Therefore, also for this complex setting, time-efficient ϰ mapping provides a helpful tool as a qualitative approach for detecting key features of the spatial distribution of pollutants, which will be useful for supporting a better-targeted chemical sampling.

[1]  G. Turner,et al.  Environmental Applications of Magnetic Measurements , 1980, Science.

[2]  John A. Dearing,et al.  Frequency-dependent susceptibility measurements of environmental materials , 1996 .

[3]  E. Appel,et al.  Atmospheric pollution history at Linfen (China) uncovered by magnetic and chemical parameters of sediments from a water reservoir. , 2015, Environmental pollution.

[4]  A. H. Weir,et al.  Clay mineralogy of sediments of the western Nile Delta , 1975, Clay Minerals.

[5]  S. Hassan,et al.  Impact of industrial wastewater disposal on surface water bodies in Mostord area, north greater Cairo. , 2001, Journal of environmental sciences.

[6]  A. Fleifle,et al.  Remediation of Agricultural Drainage Water for Sustainable Reuse , 2016 .

[7]  A. Roberts,et al.  Environmental magnetism: Past, present, and future , 1995 .

[8]  E. Appel,et al.  Traffic-Related Pollutants in Roadside Soils of Different Countries in Europe and Asia , 2015, Water, Air, & Soil Pollution.

[9]  Gang Yin,et al.  Magnetic response to air pollution recorded by soil and dust-loaded leaves in a changing industrial environment , 2015 .

[10]  Francis P. Shepard,et al.  Nomenclature Based on Sand-silt-clay Ratios , 1954 .

[11]  R. O. Aly,et al.  Water issue in Egypt: resources, pollution and protection endeavors , 2002 .

[12]  A. A. Abu Khatita,et al.  Anthropogenic particle dispersions in topsoils of the Middle Nile Delta: a preliminary study on the contamination around industrial and commercial areas in Egypt , 2016, Environmental Earth Sciences.

[13]  P. M. Nacheva,et al.  Treatment techniques for the recycling of bottle washing water in the soft drinks industry. , 2004 .

[14]  Heavy Metals Enrichement in Deposited Particulate Matter at Abu Zaabal Industrial Area -Egypt , 2011 .

[15]  J. Beer,et al.  Quantitative estimates of pedogenic ferromagnetic mineral formation in Chinese loess and palaeoclimatic implications , 1993 .

[16]  H. El-Attar,et al.  Mineralogical and chemical composition of the clay fraction of some Nile aluvial soils in Egypt , 1976 .

[17]  Catherine Moore,et al.  Spatial variation in vehicle-derived metal pollution identified by magnetic and elemental analysis of roadside tree leaves. , 2008 .

[18]  R. Hanitsch,et al.  Evaluation of wind energy potential and electricity generation on the coast of Mediterranean Sea in Egypt , 2006 .

[19]  W. P. Miller,et al.  A micro‐pipette method for soil mechanical analysis , 1987 .

[20]  J. King,et al.  SEDIMENTARY MAGNETISM, ENVIRONMENTAL MAGNETISM, AND MAGNETOSTRATIGRAPHY , 1991 .

[21]  J. G. Wilson,et al.  Problems in the assessment of heavy-metal levels in estuaries and the formation of a pollution index , 1980, Helgoländer Meeresuntersuchungen.

[22]  M. Dekkers,et al.  Selected room temperature magnetic parameters as a function of mineralogy, concentration and grain size , 2003 .