Origin and spatial distribution of metals in moss samples in Albania: A hotspot of heavy metal contamination in Europe

Highlights

• The origin of trace metals in moss samples is assessed through different methods.

• Mosses are able to reflect the spatial variability of trace elements air pollution.

• Mineral dust particles is the main source of trace elements in present moss samples.

• Geochemical interpretation of current moss data show high local dust emission.

• EF is used to distinguish contributions from atmospheric deposition or substrate soil.

Abstract

This study presents the spatial distribution of 37 elements in 48 moss samples collected over the whole territory of Albania and provides information on sources and factors controlling the concentrations of elements in the moss. High variations of trace metals indicate that the concentrations of elements are affected by different factors. Relations between the elements in moss, geochemical interpretation of the data, and secondary effects such as redox conditions generated from local soil and/or long distance atmospheric transport of the pollutants are discussed. Zr normalized data, and the ratios of different elements are calculated to assess the origin of elements present in the current moss samples with respect to different geogenic and anthropogenic inputs. Factor analysis (FA) is used to identify the most probable sources of the elements. Four dominant factors are identified, i.e. natural contamination; dust emission from local mining operations; atmospheric transport of contaminants from local and long distance sources; and contributions from air borne marine salts.

Mineral particle dust from local emission sources is classified as the most important factor affecting the atmospheric deposition of elements accumulated in the current moss samples. The open slag dumps of mining operation in Albania is probably the main factor contributing to high contents of Cr, Ni, Fe, Ti and Al in the moss. Enrichment factors (EF) were calculated to clarify whether the elements in the present moss samples mainly originate from atmospheric deposition and/or local substrate materials.

Introduction

Air pollution is a global problem and has negative effects on human, animal and plant health (Kanawade et al., 2010). Pollutants emitted into the atmosphere are deposited at the Earth's surface where they accumulate in soil, sediment, and biota of terrestrial and aquatic ecosystems (Schröder et al., 2016). In general, the main emission sources of trace metals in the air are ore and metal processing, and manufacturing, as well as combustion processes (Duffus, 2002). There isincreasing interest in the atmospheric transport of mineral dust that is believed to play an important role in several marine biogeochemical processes (Prospero et al., 2002), geochemical and geophysical processes, and in negative effects on human health (Prospero, 1999).

Soil dust is a major constituent of airborne particles transported over long distances in the global atmosphere (Prospero, 1999). In general, mineral dust particles may be emitted during mobilization and fragmentation of original un-dispersed soil subject to wind erosion (Perlwitz et al., 2015). Windblown dust and aerosol mineral composition depends upon the composition of the parent soil and its size fractionation during mobilization, and in principle, the elements observed in moss samples may therefore originate from geological, biological, and anthropogenic sources.

To improve the understanding and monitoring the effects of air pollutants on ecosystems and to scientifically assess the effectiveness of air pollution control strategies, ecological indicators are needed. Since the 1970s, Scandinavian countries have used mosses as biomonitors of trace metal atmospheric deposition, and since the 1990s, mosses are generally used in Europe as a complementary monitoring tool for atmospheric deposition of trace metals. The use of native terrestrial mosses as biomonitors is now a well-recognized technique in studies of atmospheric deposition (Steinnes et al., 1997a, Steinnes et al., 1997b, Steinnes et al., 2011, Fernandez and Carballeira, 2002, Harmens et al., 2010a, Harmens et al., 2011, Harmens et al., 2013, Harmens et al., 2015). It is a convenient and cheap way of determining the spatial and temporal trends of trace elements in atmospheric deposition (Steinnes et al., 1997a, Steinnes et al., 1997b, Steinnes et al., 2011, Harmens et al., 2015). The specific features of bryophytes such as a weakly developed cuticle (taking nutrients and water directly from the atmospheric deposition, large surface to mass ratio, and their habit of growing in groups) are strong reasons for making them suitable indicators of heavy metal atmospheric deposition (Steinnes et al., 1997a, Steinnes et al., 1997b, Steinnes et al., 2011, Markert et al., 1999, Onianwa, 2001, Schröder et al., 2010). In contrast to measurements with technical deposition samplers, moss surveys allow covering a broad range of spatial scales with the same method at a high spatial density after selecting the proper moss species as biomonitors (Schröder et al., 2016).

Albania is a small country (28,000 km²) positioned in western Balkan in the south-east of Europe. It is characterized by a complex geographic relief and climate, high diversity of geologic setting, and is influenced by different contamination inputs. Activities in ex-industrial sites of copper, chromium, iron-nickel and oil industries have produced several million tons of industrial waste impacting the surrounding environment and has adversely effected natural resources, followed by a potential health risk for people who are continuously exposed to this pollution (UNDP–Albania, 2010). The lack of a national network on air quality monitoring as well as data on morbidity caused by air pollution, makes the assessment of the health impact of air pollution in Albania impossible (UNDP–Albania, 2010).

Moss biomonitoring in Albania started in 2010/2011 when researchers from Albania joined the European Moss Survey conducted within the framework of the International Cooperative Programme on Effects of Air Pollution on Natural Vegetation and Crops, ICP Vegetation (Harmens et al., 2013). Heavy metal concentrations (As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, V) in 2010/2011 moss samples of Albania have been reported in several publications (Qarri et al., 2013, Qarri et al., 2014a, Qarri et al., 2014b, Bekteshi et al., 2015, Allajbeu et al., 2016a, Allajbeu et al., 2016b). The present paper reports on concentrations of 37 elements, their spatial distributions in 2010/2011 moss samples, and possible contributions from different sources and processes.

The European moss survey has demonstrated that the median of heavy metal concentrations in mosses between 1990 and 2010 have declined between 21% and 77% for As, V, Cd, Cr, Zn, Ni, Fe, and Pb, whilst some “hotspots” remained in 2010, particularly in Eastern Europe and Balkan countries (Harmens et al., 2015). The lowest concentrations of heavy metals were generally found in northern Europe and the highest levels in eastern and south-eastern Europe, resulting in a north-west to south-east gradient for many metals in 2010 (Harmens et al., 2015). For Al, Fe, V and Cr, the highest median concentrations in mosses were generally found in Romania, Macedonia, Albania, Ukraine, and Bulgaria. Reported Ni concentrations were generally high in parts of south-eastern European countries and Iceland. The highest levels of Hg were observed in Albania and Macedonia, followed by Italy (Bolzano region), Poland, and France.

The main objective of this work is to identify factors leading to the high levels of some trace metals (Cr, Ni, V, Fe, Al) in 2010/2011 moss samples of Albania and to extend the study to their associations and relationships with other elements. The concentration data for 37 elements in moss samples are used to evaluate the possible relationships between elements, their most important sources of origin, geochemical interpretation of the data, and secondary effects yeilding differences in their contents and distribution patterns. Differences in redox conditions of the area from where the dust originate, may generate differences in the properties of mineral dust particles that may help to distinguish their origin from local and/or long-distance migration of the contaminants.