Estimating contribution of precipitation scavenging of atmospheric particulate mercury to mercury wet deposition in Japan

Mercury wet deposition is dependent on both the scavenging of divalent reactive gaseous mercury (RGM) and atmospheric particulate mercury (Hg(p)) by precipitation. Estimating the contribution of precipitation scavenging of RGM and Hg(p) is important for better understanding the causes of the regional and seasonal variations in mercury wet deposition. In this study, the contribution of Hg(p) scavenging was estimated on the basis of the scavenging ratios of other trace elements (i.e., Cd, Cu, Mn, Ni, Pb and V) existing entirely in particulate form. Their wet deposition fluxes and concentrations in air, which were measured concurrently from April 2004 to March 2005 at 10 sites in Japan, were used in this estimation. The monthly wet deposition flux of mercury at each site correlated with the amount of monthly precipitation, whereas the Hg(p) concentrations in air tended to decrease during summer. There was a significant correlation (P<0.001) among the calculated monthly average scavenging ratios of trace elements, and the values in each month at each site were similar. Therefore, it is assumed the monthly scavenging ratio of Hg(p) is equivalent to the mean value of other trace elements. Using this scavenging ratio (W), the wet deposition flux (F) due to Hg(p) scavenging in each month was calculated by F=WKP, where K and P are the Hg(p) concentration and amount of precipitation, respectively. Relatively large fluxes due to Hg(p) scavenging were observed at a highly industrial site and at sites on the Japan Sea coast, which are strongly affected by the local sources and the long-range transport from the Asian continent, respectively. However, on average, at the 10 sites, the contribution of Hg(p) scavenging to the annual mercury deposition flux was 26%, suggesting that mercury wet deposition in Japan is dominated by RGM scavenging. This RGM should originate mainly from the in situ oxidation of Hg⁰ in the atmosphere.     

Amphibian recovery after a decrease in acidic precipitation

We here report the first sign of amphibian recovery after a strong decline due to acidic precipitation over many decades and peaking around 1980–90. In 2010, the pH level of ponds and small lakes in two heavily acidified areas in southwestern Scandinavia (Aust-Agder and Østfold in Norway) had risen significantly at an (arithmetic) average of 0.14 since 1988–89. Parallel with the general rise in pH, amphibians (Rana temporaria, R. arvalis, Bufo bufo, Lissotriton vulgaris, and Triturus cristatus) had become significantly more common: the frequency of amphibian localities rose from 33% to 49% (n = 115), and the average number of amphibian species per locality had risen from 0.51 to 0.88. In two other (reference) areas, one with better buffering capacity (Telemark, n = 21) and the other with much less input of acidic precipitation (Nord-Trøndelag, n = 106), there were no significant changes in pH or amphibians.     

Effects of acidic deposition on forest and aquatic ecosystems in New York State

Acidic deposition is comprised of sulfuric and nitric acids and ammonium derived from atmospheric emissions of sulfur dioxide, nitrogen oxides, and ammonia, respectively. Acidic deposition has altered soil through depletion of labile pools of nutrient cations (i.e. calcium, magnesium), accumulation of sulfur and nitrogen, and the mobilization of elevated concentrations of inorganic monomeric aluminum to soil solutions in acid-sensitive areas. Acidic deposition leaches essential calcium from needles of red spruce, making this species more susceptible to freezing injury. Mortality among sugar maples appears to result from deficiencies of nutrient cations, coupled with other stresses such as insect defoliation or drought. Acidic deposition has impaired surface water quality in the Adirondack and Catskill regions of New York by lowering pH levels, decreasing acid-neutralizing capacity, and increasing aluminum concentrations. Acidification has reduced the diversity and abundance of aquatic species in lakes and streams. There are also linkages between acidic deposition and fish mercury contamination and eutrophication of estuaries.     

Factors affecting trace-metal bioaccumulation in Finnish headwater lakes

Fourteen unpolluted Finnish headwater lakes with pH values varying from 4.8 to 7.0 were studied for trace-metal concentrations in water, sediment, aquatic plants (Nuphar luteum L., Sparganium sp.), aquatic insect larvae (Limnophilus sp., Phryganea sp.) and fish (Esox lucius L., Perca fluviatilis L., Coregonus sp., Salvelinus fontinalis L., Salmo trutta L.). Trace-metal deposition was estimated by analysing the snowpack. Non-parametric correlation analysis was carried out between trace metal concentrations in biota and pH, ANC, TOC, CA + Mg concentration in water and a given metal concentration in water and sediment. Bioaccumulation of several trace metals increased with increasing acidity and decreasing ANC in water. This was especially true for Pb and Cd. Aquatic plants were, in general, the best indicator group concerning differences in trace-metal bioaccumulation in lakes with different acidity. There was some evidence that a higher concentration of TOC in water may reduce bioaccumulation of Pb, Cd and Zn in aquatic plants and fish. The copper concentration in sediment was the only background variable explaining Cu concentration in aquatic insects. Multivariate analysis of the whole background data gave comparable preliminary results. Over 80% of the trace metal concentrations in biota of different lakes was explained by the background variables. In general, elevated concentrations of most of these trace metals can be expected to occur in the biota of acidified low calcareous lakes.     

Arsenic and mercury bioaccumulation in the aquatic plant, Vallisneria neotropicalis

Arsenic (As) and mercury (Hg) are among the most toxic metals/metalloids. The overall goal of this study was to investigate the bioaccumulation of these trace elements in Vallisneria neotropicalis, a key trophic species in aquatic environments. For this purpose, As and Hg concentrations were determined in sediments and natural populations of V. neotropicalis in sub-estuaries of Mobile Bay (Alabama, USA), differing with respect to past and present anthropogenic impact. Analyses indicate that the Fish River is the most contaminated among the sub-estuaries investigated; levels of As found in Fish River sediments fall within a range that could potentially cause adverse effects in biota. Sediment As concentrations were only moderately correlated with those in V. neotropicalis; no correlation was found between sediment and plant Hg levels. However, several parameters could have masked such potential relationships (e.g., differences in sediment characteristics and “biological dilution” phenomena). Results presented herein highlight the numerous parameters that can influence metal/metalloids accumulation in aquatic plants as well as species-specific responses to trace element contamination. Finally, this study underscores the need for further investigation into contaminant bioaccumulation in ecologically and economically important coastal environments.     

Trace metals in flounder, Platichthys flesus (Linnaeus, 1758), and sediments from the Baltic Sea and the Portuguese Atlantic coast

Trace metals were examined in the muscle tissue of flatfish species of flounder, Platichthys flesus (Linnaeus, 1758), sediments from two southern Baltic Sea sites (Gdańsk Bay and Ustecko-?ebskie as a reference) and in two areas of the Portuguese Atlantic coast (Douro River estuary and Atlantic fishing ground as a reference) to evaluate spatial differences in trace metals. Additionally, the accumulation of trace metals in flounder of different length classes was assessed. Flounder from the Gdańsk Bay area contained twofold more cupper (Cu), lead (Pb) and mercury (Hg) than did flounder from the Douro River estuary, but zinc (Zn) and cadmium (Cd) were at similar concentrations. The sediments from Gdańsk Bay contained significantly more Zn and threefold more Cd, while concentrations of Cu and Pb were twofold lower. The concentrations of metals in the sediments did not correlate with those in the flounder. Spatial differences were noted in metal concentrations in flounder from the southern Baltic Sea and the Portuguese Atlantic coast as well as within these regions, with higher concentrations in the flounder from the Baltic Sea Gdańsk Bay. The flounder in length class 25–30 cm from Gdańsk Bay contained metal concentrations comparable to those of class 40–45 cm specimens from the Atlantic coast. The accumulation of metals in flounder length classes differed in the two regions.     

Metal accumulation by submerged macrophytes in eutrophic lakes at the watershed scale

Metal concentrations (Al, Ba, Ca, K, Li, Mg, Na, Se, Sr and Ti) in submerged macrophytes and corresponding water and sediments were studied in 24 eutrophic lakes along the middle and lower reaches of the Yangtze River (China). Results showed that these eutrophic lakes have high metal concentrations in both water and sediments because of human activities. Average concentrations of Al and Na in tissues of submerged macrophytes were very high in sampled eutrophic lakes. By comparison, Ceratophyllum demersum and Najas marina accumulated more metals (e.g. Ba, Ca, K, Mg, Na, Sr and Ti). Strong positive correlations were found between metal concentrations in tissues of submerged macrophytes, probably because of co-accumulation of metals. The concentrations of Li, Mg, Na and Sr in tissues of submerged macrophytes significantly correlated with their corresponding water values, but not sediment values.     

Release of trace metals, sulfate and complexed cyanide from soils contaminated with gas-purifier wastes: a microcosm study

Deposited gas-purifier wastes are commonly contaminated with trace metals, sulfate and cyanide (CN) compounds. We investigated their release from three soils contaminated with gas-purifier wastes into solution in microcosm experiments under varying redox conditions (E(H) 170-620 mV). The soils differed in pH (2.2; 4.9; 7.4) and featured low amounts of trace metals, but large amounts of total S and total CN. The pH governed trace metal release in the case of the acidic soil and CN release in the case of the slightly alkaline soil. The redox potential controlled trace metal and CN release in the case of the moderately acidic soil. Sources of dissolved SO(4)(2-) were dissolution of gypsum, desorption from Fe oxides and probably oxidation of elemental S. The geochemical behaviors of trace metals (soluble under acidic and reducing conditions) and CN (soluble under alkaline and oxidizing conditions) were diametrically opposed.     

Dissolved and colloidal transport of Cd, Pb, and Zn in a silt loam soil affected by atmospheric industrial deposition.

As a result of processing of metal ores, trace metals have contaminated large areas of northern France. Metal migration from the soil to groundwater presents an environmental risk that depends on the physico-chemical properties of each contaminated soil. Soil water samples were obtained over the course of 1 year with zero-tension lysimeters from an acidic, loamy, metal contaminated soil. The average trace metal concentrations in the soil water were high (e.g. for Zn 11 mg l-1 under the surface horizon), but they varied during the sampling period. Zn concentrations were not correlated with pH or total organic carbon in the solutions but were correlated with Cd concentrations. On average, 95% of the Zn and Cd but only 50% of Pb was present in a dissolved form. Analytical transmission electron microscopy was used to identify the Zn or Pb carriers. Colloids containing Pb and Zn were biocolloids, whereas colloids containing only Zn were smectites.     

The origin of speciation: trace metal kinetics over natural water/sediment interfaces and the consequences for bioaccumulation

The speciation of heavy metals was measured over a variety of natural and undisturbed water/sediment interfaces. Simultaneously, two benthic species (oligochaete Limnodrilus spp. and the midge Chironomus riparius) were exposed to these sediments. Under occurring redox conditions, free ion activities of trace metals Cd, Cu, Ni, Pb, and Zn were measured with a chelating exchange technique, while geochemical conditions (i.e., redox) remained in tact. Free ion activities were compared with total dissolved concentrations in pore waters and surface waters in order to relate speciation to bioaccumulation. Limnodrilus spp. and C. riparius have accumulation patterns that could be linked to time-dependent exposure concentrations, expressed as chemical speciation, in the surface water and the sediment's pore water. Concentrations of free metal ions in the overlying surface water, rather than in sediment pore water, proved to be the best predictor for uptake. For the first time, measurements are obtained from sediments without disturbing physical-chemical conditions and thus bioavailability, a major restriction of other studies so far.     

Spatial patterns in wet and dry deposition of atmospheric mercury and trace elements in central Illinois,USA

An intensive 1-month atmospheric sampling campaign was conducted concurrently at eight monitoring sites in central Illinois, USA, from June 9 to July 3, 2011 to assess spatial patterns in wet and dry deposition of mercury and other trace elements. Summed wet deposition of mercury ranged from 3.1 to 5.4 μg/m² across sites for the total study period, while summed dry deposition of reactive mercury (gaseous oxidized mercury plus particulate bound mercury) ranged from 0.7 to 1.6 μg/m², with no statistically significant differences found spatially between northern and southern sites. Ratios of summed wet to summed dry mercury deposition across sites ranged from 2.2 to 4.9 indicating that wet deposition of mercury was dominant during the study period. Volume-weighted mean mercury concentrations in precipitation were found to be significantly higher at northern sites, while precipitation depth was significantly higher at southern sites. These results showed that substantial amounts of mercury deposition, especially wet deposition, occurred during the study period relative to typical annual wet deposition levels. Summed wet deposition of anthropogenic trace elements was much higher, compared to summed dry deposition, for sulfur, selenium, and copper, while at some sites summed dry deposition dominated summed wet deposition for lead and zinc. This study highlights that while wet deposition of Hg was dominant during this spring/summer-season study, Hg dry deposition also contributed an important fraction and should be considered for implementation in future Hg deposition monitoring studies.     

Metal bioavailability and toxicity to fish in low-alkalinity lakes: A critical review

Fish in low-alkalinity lakes having pH of 6.0-6.5 or less often have higher body or tissue burdens of mercury, cadmium, and lead than do fish in nearby lakes with higher pH. The greater bioaccumulation of these metals in such waters seems to result partly from the greater aqueous abundances of biologically available forms (CH(3) Hg(+), Cd(2+), and Pb(2+)) at low pH. In addition, the low concentrations of aqueous calcium in low-alkalinity lakes increase the permeability of biological membranes to these metals, which in fish may cause greater uptake from both water and food. Fish exposed to aqueous inorganic aluminum in the laboratory and field accumulate the metal in and on the epithelial cells of the gills; however, there is little accumulation of aluminum in the blood or internal organs. In low-pH water, both sublethal and lethal toxicity of aluminum has been clearly demonstrated in both laboratory and field studies at environmental concentrations. In contrast, recently measured aqueous concentrations of total mercury, methylmercury, cadmium, and lead in low-alkalinity lakes are much lower than the aqueous concentrations known to cause acute or chronic toxicity in fish, although the vast majority of toxicological research has involved waters with much higher ionic strength than that in low-alkalinity lakes. Additional work with fish is needed to better assess (1) the toxicity of aqueous metals in low-alkalinity waters, and (2) the toxicological significance of dietary methylmercury and cadmium.     

Geochemical behaviour of dissolved trace elements in a monsoon-dominated tropical river basin,Southwestern India

The study presents a 3-year time series data on dissolved trace elements and rare earth elements (REEs) in a monsoon-dominated river basin, the Nethravati River in tropical Southwestern India. The river basin lies on the metamorphic transition boundary which separates the Peninsular Gneiss and Southern Granulitic province belonging to Archean and Tertiary–Quaternary period (Western Dharwar Craton). The basin lithology is mainly composed of granite gneiss, charnockite and metasediment. This study highlights the importance of time series data for better estimation of metal fluxes and to understand the geochemical behaviour of metals in a river basin. The dissolved trace elements show seasonality in the river water metal concentrations forming two distinct groups of metals. First group is composed of heavy metals and minor elements that show higher concentrations during dry season and lesser concentrations during the monsoon season. Second group is composed of metals belonging to lanthanides and actinides with higher concentration in the monsoon and lower concentrations during the dry season. Although the metal concentration of both the groups appears to be controlled by the discharge, there are important biogeochemical processes affecting their concentration. This includes redox reactions (for Fe, Mn, As, Mo, Ba and Ce) and pH-mediated adsorption/desorption reactions (for Ni, Co, Cr, Cu and REEs). The abundance of Fe and Mn oxyhydroxides as a result of redox processes could be driving the geochemical redistribution of metals in the river water. There is a Ce anomaly (Ce/Ce*) at different time periods, both negative and positive, in case of dissolved phase, whereas there is positive anomaly in the particulate and bed sediments. The Ce anomaly correlates with the variations in the dissolved oxygen indicating the redistribution of Ce between particulate and dissolved phase under acidic to neutral pH and lower concentrations of dissolved organic carbon. Unlike other tropical and major world rivers, the effect of organic complexation on metal variability is negligible in the Nethravati River water.     

Spatial distribution of trace metals in the Krka River, Croatia: an example of the self-purification

The spatial distribution of dissolved and total trace metals (Zn, Cd, Pb and Cu) in the Krka River (partly located in the Krka National Park) has been studied using a "clean" sampling, handling and analysis technique. Differential pulse anodic stripping voltammetry (DPASV) with a hanging mercury drop electrode (HMDE) has been used for trace metal analysis. The Krka River has been divided into the upper and lower flow region with respect to the metals concentration and main physico-chemical parameters. A significant increase in trace metal concentration as the result of the untreated waste water discharge downstream of Knin Town has been registered in the upper flow region. Due to a specific characteristic of the Krka, the so-called self-purification process, a decrease in the elevated trace metals concentration from the water column takes place at numerous small lakes formed by tufa barriers (at the end of the upper flow region). The clean groundwater input at the beginning of the lower flow region additionally contributes to the observed decrease in trace metals concentration in the Krka, maintaining them at a very low level in the remaining region of fresh-water flow. The determined median total concentrations were zinc 120-7400 ng l(-1), cadmium 3-8 ng l(-1), lead 11-250 ng l(-1) and copper 110-440 ng l(-1). Karst rivers, such as the Krka River, with extremely low natural concentrations of trace metals are highly sensitive to the anthropogenic influence. Therefore, such aquatic systems require implementation of strict protection regimes in the entire catchments area.     

Measurements of Cd, Cu, Pb and Zn in the lower reaches of major Eurasian arctic rivers using trace metal clean techniques

Concentrations of dissolved and particulate Cd, Cu, Pb and Zn were determined in samples collected in summer 1998 from the lower reaches of six major Eurasian arctic rivers: the Onega, Severnaya Dvina, Mezen, Pechora, Ob and Yenisey. These data comprise some of the earliest measurements of trace metals in Eurasian arctic rivers above the estuaries using recognized clean techniques. Significant (α = 0.05) differences were observed among mean concentrations of particulate metals in the individual rivers (F ≤ 0.006), with highest levels overall observed in the Severnaya Dvina and Yenisey. No significant differences were observed among mean concentrations of dissolved metals in the individual rivers (F = 0.10-0.84). Contributions from anthropogenic sources are suggested by comparison of trace metal ratios in the samples to crustal abundances. These results establish a baseline for assessing future responses of Eurasian arctic river systems to climate-related environmental changes and shifting patterns of pollutant discharge.     

The distribution and sea–air transfer of volatile mercury in waste post-desulfurization seawater discharged from a coal-fired power plant

The waste seawater discharged in coastal areas from coal-fired power plants equipped with a seawater desulfurization system might carry pollutants such as mercury from the flue gas into the adjacent seas. However, only very limited impact studies have been carried out. Taking a typical plant in Xiamen as an example, the present study targeted the distribution and sea–air transfer flux of volatile mercury in seawater, in order to trace the fate of the discharged mercury other than into the sediments. Samples from 28 sampling sites were collected in the sea area around two discharge outlets of the plant, daily and seasonally. Total mercury, dissolved gaseous mercury and dissolved total mercury in the seawater, as well as gaseous elemental mercury above the sea surface, were investigated. Mean concentrations of dissolved gaseous mercury and gaseous elemental mercury in the area were 183 and 4.48 ng m^?3 in summer and 116 and 3.92 ng m^?3 in winter, which were significantly higher than those at a reference site. Based on the flux calculation, the transfer of volatile mercury was from the sea surface into the atmosphere, and more than 4.4 kg mercury, accounting for at least 2.2 % of the total discharge amount of the coal-fired power plant in the sampling area (1 km²), was emitted to the air annually. This study strongly suggested that besides being deposited into the sediment and diluted with seawater, emission into the atmosphere was an important fate for the mercury from the waste seawater from coal-fired power plants.     

Modelling the effect of acidity on mercury uptake by walleye in acidic and circumneutral lakes

An association between acidification of lakes and high mercury concentrations in fishes has been reported. In northern Wisconsin (USA), for example, walleye (Stizostedion vitreum) in naturally acidic lakes have higher mercury concentrations than walleye in circumneutral lakes (Weiner, 1983). In this study a bioenergetic based model for mercury uptake is applied to identify potential causes of higher mercury concentrations in fishes living in acidic lakes. Application of the model to walleye populations in northern Wisconsin indicates that higher mercury concentrations in acidic lakes are most likely a result of both increased concentrations in the water and increased efficiencies of uptake from water. Higher concentrations in the water would result in higher concentrations in the food.     

Challenges with tracing the fate and speciation of mine-derived metals in turbid river systems: implications for bioavailability

The fast-flowing and highly turbid Lagaip River (0.5–10 g/L suspended solids) in the central highlands of Papua New Guinea receives mine-derived metal inputs in both dissolved and particulate forms. Nearest the mine, metal concentrations in suspended solids were 360, 9, 90, 740 and 1,300 mg/kg for As, Cd, Cu, Pb and Zn, while dissolved concentrations were 2.7, 0.6, 3.1, 0.1 and 25 μg/L, respectively. This creates a significant metal exposure source for organisms nearer the mine. However, because the Lagaip River is diluted by a large number of tributaries, the extent to which mine-derived metals may affect biota in the lower catchments is uncertain. To improve our understanding of the forms of potentially bioavailable metals entering the lower river system, we studied the partitioning and speciation of metals within the Lagaip River system. Dissolved and particulate metal concentrations decreased rapidly downstream of the mine due to dilution from tributaries. As a portion of the particulate metal concentrations, the more labile dilute acid-extractable forms typically comprised 10–30 % for As and Pb, 50–75 % for Cu and Zn, and 50–100 % for Cd. Only dissolved Cd, Cu and Zn remained elevated relative to the non-mine-impacted tributaries (<0.03, 0.5 and 0.3 μg/L), but the concentrations did not appreciably change with increasing dilution downriver. This indicated that release of Cd, Cu and Zn was likely occurring from the more labile metal phases of the mine-derived particulates. Chelex-labile metal analyses and speciation modelling indicated that dissolved copper and lead were largely non-labile and likely complexed by naturally occurring organic ligands, while dissolved cadmium and zinc were predominantly present in labile forms. The study confirmed that mine-derived particulates may represent a significant source of dissolved metals in the lower river system; however, comparison with water quality guidelines indicates the low concentrations would not adversely affect aquatic life.     

The asiatic clam, Corbicula fluminea: An indicator of trace metal pollution in the Shatt al-Arab River, Iraq

The potential of Corbicula fluminea (Müller) as an indicator for trace metal pollution was investigated. Laboratory experiments show that Corbicula has the capability to accumulate and eliminate trace metals in relation to their concentrations in ambient water. However, an effect of individual size was observed. Seasonal variations in the concentrations of Cd, Co, Cu, Fe, Mn, Ni, Pb, V and Zn in Corbicula, water and particulate matter from the upper section of the Shatt al-Arab River were studied. Sediment samples were also analysed. Metal concentrations were determined by means of flameless AAS. It was found that Corbicula is a suitable bio-indicator for monitoring of trace metal pollution. Metal concentrations in Corbicula tissues correlated better with their corresponding concentrations in particulate matter than with the dissolved form. Temporal variations in metal concentrations were attributed to several factors, including fluctuations in metal inputs, and in geochemical and hydrological characteristics of the water. The obtained levels of trace metals were comparable to those reported for control sites, with the exception of Cd, Cu and Zn whose concentrations were higher in both Corbicula and particulate matter.     

Relationships between lake chemistry and calcium and trace metal concentrations of aquatic invertebrates eaten by breeding insectivorous waterfowl

Ca, P, Al, and trace metal (Cu, Ni, Zn, Cd, and Pb) concentrations were measured in several aquatic invertebrate taxa used as food by breeding insectivorous waterfowl, sampled from three sites in eastern Canada with widely varying water chemistry. Ca concentrations were highest in molluscs (snails and clams), averaging 200-300 mg g(-1) (shells included). Aquatic insects of varying sizes, life stages and habits (caddisfly larvae, dragonfly larvae, adult backswimmers, waterstriders, and whirligig beetles) had much lower mean Ca concentrations, ranging from about 0.6 mg g(-1) (beetles) to 1.8 mg g(-1) (caddisflies). Invertebrate-Ca concentrations decreased with increasing body mass for several taxa, with smaller and larger individuals providing similar absolute amounts of Ca. Ca concentrations in most aquatic insects (but not molluscs) were reduced under acidic, low Ca, high Al, low dissolved organic carbon (DOC) and/or low total phosphorus (TP) conditions. In stepwise multiple regressions, pH was consistently the main factor explaining variability in invertebrate-Ca, after controlling for the negative relationship between invertebrate-Ca and body mass for some taxa. Molluscs were absent from lakes below pH 5.3. In general, concentrations of P and metals in invertebrate taxa were not significantly correlated with lake pH. Levels of Al, Cd, or Pb were not sufficiently high to be considered toxic to potential consumers of these organisms. For waterfowl and other birds breeding in acid-stressed habitats and relying on aquatic invertebrates as a source of food, a reduced availability of dietary Ca is more likely than an increased exposure to toxic metals to negatively affect reproductive success, especially when other adverse effects of acidification (lower diversity of prey) are considered.