Geochemical fingerprints and controls in the sediments of an urban river: River Manzanares, Madrid (Spain)

Abstract

The geochemical fingerprint of sediment retrieved from the banks of the River Manzanares as it passes through the City of Madrid is presented here. The river collects the effluent water from several Waste Water Treatment (WWT) plants in and around the city, such that, at low flows, up to 60% of the flow has been treated. A total of 18 bank-sediment cores were collected along the course of the river, down to its confluence with the Jarama river, to the south-east of Madrid. Trace and major elements in each sample were extracted following a double protocol: (a) "Total" digestion with HN0 3 , HC10 4 and HF; (b) "Weak" digestion with sodium acetate buffered to pH=5 with acetic acid, under constant stirring. The digests thus obtained were subsequently analysed by ICP-AES, except for Hg which was extracted with aqua regia and sodium chloride-hydroxylamine sulfate, and analysed by Cold Vapour-AAS. X-ray diffraction was additionally employed to determine the mineralogical composition of the samples. Uni-and multivariate analyses of the chemical data reveal the influence of Madrid on the geochemistry of Manzanares' sediments, clearly manifested by a marked increase in the concentration of typically "urban" elements Ag, Cr, Cu, Pb and Zn, downstream of the intersection of the river with the city's perimeter. The highest concentrations of these elements appear to be associated with illegal or accidental dumping of waste materials, and with the uncontrolled incorporation of untreated urban runoff to the river. The natural matrix of the sediment is characterised by fairly constant concentrations of Ce, La and Y, whereas changes in the lithology intersected by the river cause corresponding variations in Ca-Mg and Al-Na contents. In the final stretch of the river, the presence of carbonate materials seems to exert a strong geochemical control on the amount of Zn and, to a lesser extent, Cu immobilised in the sediments. This fact suggests that a variable but significant proportion of both elements may be susceptible to reincorporation in the aqueous phase under realistic environmental conditions.

Assessment of heavy metal concentration in the Khoshk River water and sediment, Shiraz, Southwest Iran

“…Urban rivers are often canalized, the flow of water is regulated in them, some sections of a river can be isolated, and the water in them may be removed for remediation purposes during which sediments are dredged and/or exposed to the atmosphere, etc. (Miguel et al 2005). Contaminants generally enter the rivers through two pathways: (1) identifiable point sources such as municipal and industrial wastewater effluents and (2) diffuse sources, closely related to the meteorological factors.…”

A complex investigation of the extent of pollution in sediments of the Sava River. Part 1: Selected elements

“…In addition, chemical analysis of sediments are commonly applied since they reflect spatial and temporal variation of contaminant concentrations of elements (Loring and Rantala 1992;Grosbois et al 2006;Santos Bermejo et al 2003;Tomiyasu et al 2006;de Miguel et al 2005;Meybeck et al 2007;Škrbić andČupić 2004;Woitke et al 2003). Among elements, Cd, Pb, Cu, Zn, Cr, Ni, Hg, and As are often accumulated in sediments as a consequence of industrial (Karadede-Akin and Ünlü 2007; Giusti and Taylor 2007;Sin et al 2001), municipal (Grosbois et al 2006;de Miguel et al 2005), and mining activities (Svete et al 2000;Covelli et al 2001;Hines et al 2006), while intensive rural land use and domestic sewage are a major source of P deposition in sediments (House and Denison 2002;Nguyen 1999). In many cases, the extent of pollution cannot be estimated solely on the basis of the determination of the total content of chemical substances in sediments because bioavailability and toxicity to organisms depend on their chemical forms.…”

A review of the distribution of particulate trace elements in urban terrestrial environments and its application to considerations of risk

“…The application of this compost on urban soil re-introduces Ag, resulting in median concentrations of this element nearly five times higher in compost amended soils than in nonamended urban soils. Data published by De Miguel et al (2005) strongly suggest that not all the Ag that enters the urban water system is confined in sewage sludge to re-enter the urban cycle. Concentrations of up to 16 ug g~ and a strong association with typically anthropogenic elements like Cu, Pb, and Zn in the sediments of the River Manzanares that runs through Madrid implies that a fraction of this Ag is stored in the river sediments.…”