Martin M. Larsen

Transfer of mercury in the marine food web of West Greenland

Total mercury (THg), methylmercury (MeHg) and stable isotopes of nitrogen (delta(15)N) and carbon (delta(13)C) were measured in three invertebrate, five fish, three seabird and three marine mammal species of central West Greenland to investigate trophic transfer of mercury in this Arctic marine food web. The food web magnification factor (FWMF) estimated as the slope of the regression between the natural logarithm of THg or MeHg concentrations (mg kg(-1) dw) and tissue delta(15)N ( per thousand) was estimated to 0.183 (SE = 0.052) for THg and 0.339 (SE = 0.075) for MeHg. The FWMFs were not only comparable with those reported for other Arctic marine food webs but also with quite different food webs such as freshwater lakes in the sub-Arctic, East Africa and Papua New Guinea. This suggests similar mechanisms of mercury assimilation and isotopic (delta(15)N) discrimination among a broad range of aquatic taxa and underlines the possibility of broad ecosystem comparisons using the combined contaminant and stable isotope approach.

A heavy metal monitoring-programme in Denmark

Abstract A monitoring programme for the concentrations of heavy metals in Danish arable soils and on nature areas was initiated in 1990 by the Danish EPA. The monitoring programme comprises 393 sampling points scattered in a regular grid over the country and in addition 20 sampling points on agricultural fields fertilised with sewage sludge. Samples taken from the top 25 cm of the soil at each sampling point have been analysed for the heavy metals Pb, Cd, Cu, Cr, Hg, Ni and Zn and for the metalloid As. The content of Ni, Zn and Cr and to some extent Cu and As, are well correlated with soil texture. Differences are not found between soils with different land use, atmospheric deposition, etc. that renders it possible, that the soil content of heavy metals in general is determined by anthropogenic sources. It is, however, possible, that the concentrations at some points with high values of As, Cd, Cu, Pb and Hg are affected by anthropogenic sources. The measured concentrations are comparable to what have been found in earlier Danish investigations and typically lower than levels found in neighbouring countries. It is concluded that the levels of heavy metals found in Danish arable soils and on nature areas in general do not give rise to concern. The levels are generally low compared to Danish soil quality criteria and the current load is modest compared to the content in the soil.

Passive Sampling in Regulatory Chemical Monitoring of Nonpolar Organic Compounds in the Aquatic Environment

We reviewed compliance monitoring requirements in the European Union, the United States, and the Oslo-Paris Convention for the protection of the marine environment of the North-East Atlantic, and evaluated if these are met by passive sampling methods for nonpolar compounds. The strengths and shortcomings of passive sampling are assessed for water, sediments, and biota. Passive water sampling is a suitable technique for measuring concentrations of freely dissolved compounds. This method yields results that are incompatible with the EUs quality standard definition in terms of total concentrations in water, but this definition has little scientific basis. Insufficient quality control is a present weakness of passive sampling in water. Laboratory performance studies and the development of standardized methods are needed to improve data quality and to encourage the use of passive sampling by commercial laboratories and monitoring agencies. Successful prediction of bioaccumulation based on passive sampling is well documented for organisms at the lower trophic levels, but requires more research for higher levels. Despite the existence of several knowledge gaps, passive sampling presently is the best available technology for chemical monitoring of nonpolar organic compounds. Key issues to be addressed by scientists and environmental managers are outlined.

Mussels as a tool for mitigation of nutrients in the marine environment.

Long-line mussel farming has been proposed as a mitigation tool for removal of excess nutrients in eutrophic coastal waters. A full-scale mussel farm optimized for cost efficient nutrient removal was established in the eutrophic Skive Fjord, Denmark where biological and economic parameters related to nutrient removal was monitored throughout a full production cycle (1 yr). The results showed that it was possible to obtain a high area specific biomass of 60 t WW ha(-1) eqvivalent to a nitrogen and phosphorus removal of 0.6-0.9 and 0.03-0.04 t ha(-1)yr, respectively. The analysis of the costs related to establishment, maintenance and harvest revealed that mussel production optimized for mitigation can be carried out at a lower cost compared to mussel production for (human) consumption. The costs for nutrient removal was 14.8 € kg(-1)N making mitigation mussel production a cost-efficient measure compared to the most expensive land-based measures.

Bioremediation of reject water from anaerobically digested waste water sludge with macroalgae (Ulva lactuca, Chlorophyta)☆

Phosphorus and biologically active nitrogen are valuable nutrient resources. Bioremediation with macroalgae is a potential means for recovering nutrients from waste streams. In this study, reject water from anaerobically digested sewage sludge was successfully tested as nutrient source for cultivation of the green macroalgae Ulva lactuca. Maximal growth rates of 54.57±2.16% FW d(-1) were achieved at reject water concentrations equivalent to 50 μM NH4(+). Based on the results, the growth and nutrient removal was parameterised as function of NH4(+) concentration a tool for optimisation of any similar phycoremediation system. Maximal nutrient removal rates of 22.7 mg N g DW(-1) d(-1) and 2.7 mg P g DW(-1) d(-1) were achieved at reject water concentrations equivalent to 80 and 89 μM NH4(+), respectively. A combined and integrated use of the produced biomass in a biorefinery is thought to improve the feasibility of using Ulva for bioremediation of reject water.

Sediment baseline study of levels and sources of polycyclic aromatic hydrocarbons and heavy metals in Lake Nicaragua

Selected metals and polycyclic aromatic hydrocarbons (PAHs) were analyzed in sediment samples from 24 sites in Lake Nicaragua sampled May 2010 to provide a baseline of pollution levels. Cu exceeded the Consensus-Based Sediment Quality Guideline (CBSQG) Threshold Effect Concentrations (TECs) at 21 sites while Ni exceeded the value at one site. Comparison of the sampling sites showed that the south-eastern shore and a central part of the lake contained the highest levels of As, Cd, Cr, and Ni, while the western part of the lake contained the highest levels of Cu, Pb, and Zn. Analysis of PAH levels showed that the CBSQG TECs were exceeded by naphthalene at five sites. The sum concentrations of the 16 US EPA priority PAHs (∑PAH16) ranged from 0.01 mg kg(-1) dw to 0.64 mg kg(-1) dw. The highest ∑PAH16 concentration was found upstream in River Mayales and the PAH composition revealed a heavy PAH fraction (e.g., creosote). The main sources of PAHs in Lake Nicaragua were determined as of diffuse petrogenic and pyrogenic origin as well as diagenetic produced perylene. The relative importance of these PAH sources was determined by interpretation of loading and score plots from a principal component analysis. This study concluded that areas of Lake Nicaragua represent an important pollution baseline for future studies in this lake and other tropical lakes.

Endocrine-Disrupting Effects of Compounds in Danish Streams

Effluents from municipal wastewater-treatment plants and scattered dwellings, as well as runoff from agricultural fields, are sources of endocrine-disrupting compounds (EDCs) in the aquatic environment. The present study investigated the correlation between the occurrence of EDCs in nine Danish streams using passive samplers (polar organic integrative samplers and silicone membranes) and determined their possible biological effects as assessed by mammal cell cultures and the mussel (Unio tumidus). The passive samplers and mussels were exposed simultaneously at the study sites. The extracts from the passive samplers were used to measure the concentrations of EDCs and the biological effects on the estrogen (ER), androgen (AR), and aryl hydrocarbon (AhR)-receptor transactivation. Male mussels were investigated for biomarkers of endocrine effects, such as the levels of vitellogenin-like proteins measured as alkali-labile phosphate (ALP). EDC concentrations, hormone-receptor transactivation (ER, AR, AhR), and level of ALP were greater downstream of wastewater-treatment plants compared with upstream sites and sites supposed to be relatively nonimpacted by wastewater. Furthermore, there was a significant positive correlation between in vitro AhR transactivation and frequency of ALP of male mussels. We conclude that wastewater effluent is an important source of endocrine-disrupting effects in the aquatic environment and that the combination of biological effect measurements and chemical analyses based on passive sampling is useful in the assessment of the ecological state of the aquatic environment.

Polychlorinated biphenyls, organochlorine pesticides and polycyclic aromatic hydrocarbons in a one-off global survey of bivalves.

During the Danish Galathea 3 expedition, bivalve samples were collected at the Faroe Islands, Greenland, Ghana, South Africa, Australia, Solomon Islands, New Zealand, Chile, US Virgin Islands, Boston, Newfoundland and Shetland Islands and analysed for organochlorines and PAHs. Concentration differences of up to three orders of magnitude were observed, with the highest concentrations at Boston harbour (SPCB 338 ng g(-1) dw, ΣSPAH 5966 ng g(-1) dw) and the Sydney estuary (ΣSPCB 282 ng g(-1) dw, SPAH 1453 ng g(-1) dw). Local impacts were also found for the Greenland capital Nuuk in terms of PCB and PAH levels, while other Greenland samples came closest to representing PAH background levels. Several locations had undetectable organochlorine levels, including Hobart and Chile, which had the lowest SPAH concentrations (<200 ng g(-1) dw). It was possible to group the stations according to their pyrogenic/petrogenic influence using Principal Component Analyses, and indications of petroleum sources were found at Nuuk.

National monitoring study in Denmark finds increased and critical levels of copper and zinc in arable soils fertilized with pig slurry.

The increasing consumption of copper and zinc in modern farming is linked to their documented benefit as growth promoting agents and usefulness for controlling diarrhoea. Copper and zinc are inert and non-degradable in the slurry and the environment and thereby introducing new challenges and concern. Therefore, a follow-up to pervious national soil monitoring programs on heavy metals was initiated in 2014 with special focus on the historical trends in soil concentrations of copper and zinc in Danish arable soils. Hereby it is possible to analyse trends for a 28 year period. Data shows that: 1) Amendment of soils with pig slurry has led to a significant increase in soil concentrations of copper and zinc, especially in the latest monitoring period from 1998 to 2014; 2) Predicted no-effect concentrations for soil dwelling species published by the European Union is exceeded for zinc in 45% of all soil samples, with the highest proportion on sandy soils; 3) The current use of zinc and copper in pig production may lead to leaching of metals, especially zinc, from fields fertilized with pig slurry in concentrations that may pose a risk to aquatic species.

Trace elements determination in seawater by ICP-MS with on-line pre-concentration on a Chelex-100 column using a 'standard' instrument setup.

Graphical abstract