Seasonal variations and spatial distributions of perfluoroalkyl substances in the rivers Elbe and lower Weser and the North Sea

Abstract

The spatial distributions and seasonal variations of perfluoroalkyl substances (PFASs) in surface waters were investigated for the German rivers Elbe and lower Weser, and the North Sea. ∑PFAS concentrations ranged from 4.1 to 250 ng L⁻¹ in the River Elbe, from 3.8 to 16 ng L⁻¹ in the lower Weser, and from 0.13 to 10 ng L⁻¹ in the North Sea. The most abundant compound was perfluorobutanesulfonate (PFBS) with a proportion of 24% in river water and 31% in seawater samples. The concentrations of perfluorohexanoic acid (PFHxA) and perfluorooctanoic acid (PFOA) in Elbe River water showed significant seasonal variation in 2011. The seasonal variations might be related to the variations of water discharge. The highest concentrations of PFOA and PFHxA were detected in August. Pearson correlations showed that perfluorobutanoic acid (PFBA) and PFBS had different sources from other PFASs, and the current manufacturing and use of C₄-based products could explain the distinction. The estimated fluxes of individual substances and ∑PFASs in the River Elbe showed no significant seasonal variation. The annual fluxes of PFASs to the North Sea were estimated to be 335 ± 100 kg year⁻¹ from the River Elbe and 102 ± 22 kg year⁻¹ from the River Weser.

Introduction

Perfluoroalkyl substances (PFASs) have been produced for more than 50 years and are globally ubiquitous in air (Dreyer and Ebinghaus, 2009), water (Yamashita et al., 2005), sediment (Bao et al., 2010), and organisms (Kannan et al., 2006). Perfluorooctane sulfonic acid (PFOS) and related substances were restricted by EU Directive 2006/122/EC in 2008 and listed in the Stockholm Convention in 2009 (EPC, 2006, Secretariat, 2009). Subsequently, a decreasing trend is predicted both for production and emission to the environment (Paul et al., 2009). As for another C₈-PFAS perfluorooctanoic acid (PFOA), national programs in the United States and Canada are aiming to eliminate this substance, its salts, and its precursors (Vierke et al., 2012). In Norway, PFOA is to be phased out in consumer products from 2013, but no regulatory activities are implemented in other European countries. Short-chained PFASs (e.g., perfluorobutane sulfonic acid (PFBS) and perfluorobutanoic acid (PFBA)) were introduced as substitute compounds for C₈-PFASs (3M, 2011), and relatively high concentrations of PFBS and PFBA were reported in German environment i.e. the River Rhine water (Möller et al., 2010), drinking water sources (Eschauzier et al., 2012), and precipitation (Dreyer et al., 2010). PFASs concentrations in the River Elbe and North Sea were previously investigated in 2003 and 2006 (Ahrens et al., 2009b, Ahrens et al., 2009c), and this study presents the latest data for PFASs within a similar area.

Riverine levels of PFASs could reflect the emission of PFASs from a watershed, and the estimation of the discharge flux is useful to investigate the transport of PFASs (McLachlan et al., 2007, Pistocchi and Loos, 2009). The primary sources of riverine PFASs were waste water treatment plants (WWTPs), local runoff, and dry and wet deposition, and PFAS concentrations were found to vary with water flow. To our best knowledge, few studies were related to the seasonal variations of PFASs in river water as well as its adjacent coastal water.

The River Elbe has a length of 1165 km with a drainage area of 144 000 km². The Hamburg port at the downstream is the largest port in Germany. Hamburg City is the second largest city in Germany with prosperous industry and economy. The River Weser is the second longest river in Germany, with a length of 733 km and a drainage area of 46 300 km². Both of the rivers discharge water into the North Sea, where the current transports North Atlantic water to the German coast. Studies about the River Elbe, Weser and the North Sea could reflect the contamination of PFASs in northwest Germany and the influence of rivers to the North Sea.

In this study, the concentrations of PFASs were detected in surface water samples from the rivers Elbe and lower Weser and from the North Sea. The spatial and temporal trends of PFASs were investigated with reference to the previous studies conducted in the same area (Ahrens et al., 2009b, Ahrens et al., 2009c). Sources of individual compounds were discussed. Sampling campaigns were conducted at the same stations in different seasons. Seasonal variations were investigated in river and marine surface waters for the first time. The fluxes of PFASs from the River Elbe to the North Sea were estimated in different seasons and the annual discharge was calculated.