A. Carballeira

Seasonal variation and background levels of heavy metals in two green seaweeds

Seasonal variation in the contents of different metals (Al, Cr, Cu, Fe, Mn, Ni and Zn) in two genera of macroalgae, Ulva and Enteromorpha was studied at 22 sites on the northwest coast of Spain. The seasonal variation in the different metals followed a similar pattern in both seaweeds and appeared to be caused by dilution during the period of maximum growth and concentration during periods of slow growth. Fluvial inputs of Al, Fe and Mn in autumn and winter appeared to accentuate the latter effect: the concentrations of these three metals in both macroalgae and of Cr in Enteromorpha were highest at those sites most influenced by inputs from rivers. The background levels of Cr, Cu, Ni and Zn in the algae in summer and winter were established.

An extended study of heavy metal deposition in Galicia (NW Spain) based on moss analysis

This paper describes the first attempt to determine the levels of heavy metal contamination in Galicia (NW Spain) by analysis of moss species. Samples of Scleropodium purum and Hypnum cupressiforme were collected from 75 sites, in 1995 and 1997, and analysed by atomic absorption spectrophotometry and atomic fluorescence for Al, As, Co, Cr, Cu, Fe, Hg, Ni, Pb and Zn. Comparisons were made between the two moss species used and, for those elements present at different concentrations in the two species, regression lines were made for interspecies calibration. Distribution maps were drawn up for each of the elements according to their concentration in the moss. In certain areas it was possible to relate deposition to the existence of known sources of contamination. The study demonstrates that the highest levels of elements were found in the most heavily industrialised and populated areas. Concentrations of As, Cu, Hg and Ni, recorded during the 1997 sampling were significantly higher than those found in 1995, possibly due to agricultural and industrial activities.

Use of native and transplanted mosses as complementary techniques for biomonitoring mercury around an industrial facility

Terrestrial mosses were used simultaneously in passive (native species, Scleropodium purum and Hypnum cupressiforme) and active (S. purum transplants in moss bags) biomonitoring techniques in a study that aimed to demonstrate the compatibility of the two methods by detailed investigation of the spatial distribution of mercury in the surroundings of a chlor-alkali plant. Native mosses were sampled and transplants exposed (for periods of 30 days) at two different times of the year in order to take into account different environmental conditions (precipitation, temperature, prevailing winds, etc.). The concentrations of Hg in the native mosses ranged between 0.04 and 11.78 microg g(-1) in February and 0.26 and 12.7 microg g(-1) in September; in the transplants the concentrations ranged between 0.39 and 1.9 microg g(-1) in June and 0.036 and 2.75 microg g(-1) in November. These values are all within the ranges reported in the literature. The total concentrations were transformed into either contamination factors (CF) (by taking into account the background levels of Hg in the native mosses) or enrichment factors (EF) (by taking into account the initial concentrations in the transplants). In both cases, there was a clear relationship with the distance from the source of emission, irrespective of the time of year. Within the range of distances for which data were available for natives and transplants, the CF and EF were highly correlated. This implies that transplants sited in the area immediately surrounding the plant, where the density of native mosses was very low, can be used to determine the degree of contamination in this area. The study also illustrated that the native moss appeared to adapt to the surrounding environment because at an equal distance (> 500 m) from the source of emission the value of the CF for native mosses fell to 1, but the EF for transplanted mosses remained still high (5.2).

Moss bag biomonitoring: a methodological review.

Although the moss bag technique has been used for active biomonitoring for the past 40years, there is still no standardized protocol that enables application of the technique as a tool to monitor air quality. The aim of this review paper is to evaluate the degree of standardization of each of the variables that must be considered in applying the technique (i.e. the variables associated with preparation of the moss and moss bags, exposure of the bags, and post-exposure treatment). For this purpose, 112 scientific papers that report the methods used in applying the moss bag technique were consulted. Finally, on the basis of the conclusions reached, we propose a protocol that will enable each of these variables to be investigated separately, with the final aim of developing a standardized methodology.

Ulva and Enteromorpha as indicators of heavy metal pollution

We studied the use of two genera of green macroalgae, Ulva and Enteromorpha, as indicators of heavy metal contamination on the northwest coast of Spain. We evaluated the extent of external contamination by fine particles adhering to the algal thallus and found that although not a problem in Ulva, it may be in Enteromorpha samples. The mean levels of metals in both seaweeds were in accordance with previously reported levels in different species of the genera in clean areas. A large number of significant correlations between levels of metals in macroalgae and in sediment (for both the total and labile fractions) were found. However, almost all of the coefficients of correlation decreased after geochemical normalization of sediment metal concentrations.

Influence of watershed lithology on heavy metal levels in estuarine sediments and organisms in Galicia (North-West Spain)

Abstract The possible influence of watershed lithology on metal levels in estuarine sediments and organisms (macroalgae, phanerogams, molluscs and polychaetes) in Galicia (north-west Spain) was investigated. In sediments, background levels of Fe, Mn, Cu, Cr, Pb and Ni—but not of Co and Zn—are determined by watershed lithology. In contrast, watershed lithology is not a reliable predictor of the metal contents in organisms, although for some metals in some species lithology has a statistically significant influence on metal content.

Nitrogen concentrations in mosses indicate the spatial distribution of atmospheric nitrogen deposition in Europe

In 2005/6, nearly 3000 moss samples from (semi-)natural location across 16 European countries were collected for nitrogen analysis. The lowest total nitrogen concentrations in mosses (<0.8%) were observed in northern Finland and northern UK. The highest concentrations (≥ 1.6%) were found in parts of Belgium, France, Germany, Slovakia, Slovenia and Bulgaria. The asymptotic relationship between the nitrogen concentrations in mosses and EMEP modelled nitrogen deposition (averaged per 50 km × 50 km grid) across Europe showed less scatter when there were at least five moss sampling sites per grid. Factors potentially contributing to the scatter are discussed. In Switzerland, a strong (r(2) = 0.91) linear relationship was found between the total nitrogen concentration in mosses and measured site-specific bulk nitrogen deposition rates. The total nitrogen concentrations in mosses complement deposition measurements, helping to identify areas in Europe at risk from high nitrogen deposition at a high spatial resolution.

Background heavy metal levels in estuarine sediments and organisms in Galicia (northwest Spain) as determined by modal analysis

We investigated metal (Al, Fe, Mn, Co, Cr, Cu, Ni, Zn and Pb) concentrations in surface sediments (107 samples) and intertidal organisms (424 samples of macroalgae, phanerogams, molluscs and polychaetes) from 44 estuarine areas in Galicia (northwest Spain). Three acid extraction procedures (HCl, HNO3 and HNO3 + HF) were used. Following analysis of the effect of sediment particle size distribution on metal contents, Al content was selected as a normalization element. For most species and most metals, there was only minor contamination of the organism samples by particulate matter, confirming the efficiency of the washing and depuration procedures used and thus obviating the need to correct for such contamination on the basis of Fe contents. Background metal levels in the sediments and organisms were estimated by modal analysis. To the best of our knowledge, this is the first time that this method has been used for this purpose.

Is it possible to estimate atmospheric deposition of heavy metals by analysis of terrestrial mosses

Here we present a critical review of diverse research studies involving estimation of atmospheric deposition of heavy metals from the concentrations of the contaminants in terrestrial moss. The findings can be summarized as follows: i) significant correlations between the concentrations of contaminants in moss and bulk deposition were observed in only 40.1% of the cases in which the relationship was studied and in only 14.1% of the cases, the coefficient of correlation was >0.7; ii) some method-related problems were identified (i.e. small sample sizes, elimination of some data from the regression analyses, large distances between the moss sampling sites and the bulk precipitation collectors, differences in times of exposure of the moss samples and collection times for the bulk precipitation), so that the results of the studies may not be completely valid, and iii) evidence was found in the relevant literature that moss does not actually integrate the atmospheric deposition received. We also discuss the reason why, in accordance with the published data, bulk deposition cannot be correctly estimated by determination of the final concentrations of contaminants in the organism, such as the existence of different sources of contamination, the physicochemical characteristics of the sources of deposition, physicochemical processes to which the organism is subjected and the biological processes that take place in the moss. Taking into account the above findings, it was concluded that, except for certain elements and specific cases (i.e. Pb and Cd), atmospheric deposition of elements cannot be accurately estimated from the concentrations of metals and metalloids in moss tissues. However, the analysis of moss does provide information about the presence of contaminants in the atmosphere, their spatial and temporal patterns of distribution and how they are taken up by live organisms. Use of mosses is therefore recommended as a complementary (rather than an alternative) technique in the conventional analysis of bulk deposition of contaminants.

A comparison of indigenous mosses and topsoils for use in monitoring atmospheric heavy metal deposition in Galicia (northwest Spain).

Samples of moss (Scleropodium purum or, in its absence, Hypnum cupressiforme) and of topsoil (0-5 cm) were collected in the spring of 1995, from 75 sites distributed throughout Galicia (northwest Spain) in order to compare the potential usefulness of each in evaluating the atmospheric deposition of contaminants. Analysis was made of the total content of various metals in the moss and of different soil metal fractions (including total metal content, labile metals and metals bound to organic material). We found that the labile fraction most closely resembled the metal content of the moss. Calculation of enrichment factors allowed us to show that the soil was not, except in the case of Cr, the main source of contamination in the moss. By comparing contamination factors of metals in moss and soil fraction samples we found that moss samples were more useful for evaluating the degree of contamination at different sites.