Seasonal differences in mercury accumulation in Trichiurus lepturus (Cutlassfish) in relation to length and weight in a Northeast Brazilian estuary

Background, aim, and scope  At tropical latitudes, and especially on the semi-arid coasts of the Brazilian Northeast, the rainfall regime governs the water quality of estuaries due to the pronounced difference between the rainy and dry seasons. These changes may be responsible for seasonal changes in bioavailability of mercury (Hg) and other pollutants to the estuarine and coastal biota. Mercury bioaccumulates along estuarine–marine food chains usually result in higher concentrations in tissues of top predators and posing a risk to both marine mammals and humans alike. The Goiana River Estuary (7.5° S) is a typical estuary of the semi-arid tropical regions and supports traditional communities with fisheries (mollusks, fish, and crustacean). It is also responsible for an important part of the biological production of the adjacent coastal waters. Materials and methods   Trichiurus lepturus (Actinopterygii: Perciformes) is a pscivorous marine straggler. Fish from this species (n = 104) were captured in a trapping barrier used by the local traditional population and using an otter trawl net along the main channel of the low estuary during two dry seasons (D1 = November, December 2005, January 2006; D2 = November, December 2006, January 2007) and the end of a rainy season (R = August, September, October 2006). Fish muscle samples were preserved cold and then freeze-dried prior to analysis of its total mercury (Hg-T) contents. Total mercury was determined by cold vapor atomic absorption spectrometry (CV-AAS) with sodium borohydride as a reducing agent. Results  The studied individuals (n = 104) were sub-adult (30–70 cm, 71 ind.) and adult fish (>70 cm, 33 ind.). Weight (W) (204.1 ± 97.9 g, total biomass = 21,229.7 g) and total length (TL) (63.1 ± 10.1 cm, range 29.5–89.0 cm) presented a significant (p < 0.05) correlation. Two-way ANOVA (n = 81) showed that TL and W had significant differences (p < 0.05) among seasons, being higher in D1 than in D2 and R, respectively. Moreover, season vs. month interaction were detected for the variables length and weight. For the variable weight was detected significant difference for the factor month (p < 0.05). It suggests that the fish enter the estuary at the end of the rainy season and increase in length and weight during the time they spend in the estuary. Fish from this estuary are shown to be fit for human consumption (125.3 ± 61.9 μgHg-T kg^–1 w.wt.; n = 104). Fish mercury contents increased with size and weight. Correlations between TL and Hg-T (r = 0.37286) and between W and Hg-T (r = 0.38212) were significant (p < 0.05). Dryer months showed higher mercury concentrations in fish (D1 773.4 ± 207.5 μgHg-T kg^–1 d.wt., n = 27; D2 370.1 ± 78.8 μgHg-T kg^–1 d.wt., n = 27; R 331.2 ± 138.5 μgHg-T kg^–1 d.wt., n = 27). The variable mercury concentration showed differences in relation to the factor season (p < 0.05), where fish captured during the first dry season showed the highest concentration of mercury. The correlation between Hg-T and rainfall (Rf) showed a negative correlation (r = –0.56; p < 0.05). Discussion  The main likely source of mercury to this estuary is diffuse continental run off, including urban and industrial effluents. Since concentration of mercury in fish tissue is negatively correlated to rainfall, but positively correlated with fish length and weight, it suggests that fish growth in this estuary results in mercury uptake and concentration on the fish tissue. In the dry season of 2005–2006, when rainfall remained below the historic average, fish bioaccumulated significantly more mercury than in the dry season 2006–2007, when rainfall was within the predictable historic average. It is suggested that less rainfall, and consequently less particulate matter and less primary production in the estuary, make mercury more available to the higher levels of the estuarine food chain. In the case of higher rainfall, when river flow increases and water quality in the estuary is reduced, mercury probably is quickly exported associated to the particulate matter to the adjacent coastal waters where it then disperses. This species is a potential routine bioindicator for mercury contamination of the biota, but so far was used only with a limited number of individuals and contexts. Conclusions  Fish from the Goiana River estuary can still be safely consumed by the local population. However, any further contamination of this resource might lead to total mercury levels above the recommended limits for pregnant women and small children. The proposed heavy dependency of total mercury levels in fish on water quality indicates that land use and water quality standards must be more closely watched in order to guarantee that best possible practices are in place to prevent bioaccumulation of mercury and its transfer along the food chain. Human interventions and climatic events which affect river water flow are also playing a role in the mercury cycle at tropical semi-arid estuaries. Recommendations and perspectives   T. lepturus is largely consumed by coastal populations of tropical and sub-tropical countries all over the world. It is also consumed by a number of marine mammals over which we have a strong conservation interest. This species is also a link among different ecosystems along the estuarine ecocline. Therefore, knowledge of its degree of contamination might contribute to public health issues as well as marine conservation actions. Studies on mercury and other contaminants using this species as bioindicator (cosmopolitan, readily available) could help elucidating mechanisms through which pollutants are being transferred not only through the food chain, but also from estuarine–coastal–open waters. In addition, using the same species in marine pollution studies, especially as part of a mosaic of species, allows for wide range comparisons of marine food chain contamination.     

The economic impact of sea-level rise on nonmarket lands in Singapore

Sea-level rise, as a result of climate change, will likely inflict considerable economic consequences on coastal regions, particularly low-lying island states like Singapore. Although the literature has addressed the vulnerability of developed coastal lands, this is the first economic study to address nonmarket lands, such as beaches, marshes and mangrove estuaries. This travel cost and contingent valuation study reveals that consumers in Singapore attach considerable value to beaches. The contingent valuation study also attached high values to marshes and mangroves but this result was not supported by the travel cost study. Although protecting nonmarket land uses from sea-level rise is expensive, the study shows that at least highly valued resources, such as Singapore's popular beaches, should be protected.     

A decision framework for possible remediation of contaminated sediments in the River Kymijoki, Finland

Background, aim, and scope  The paper describes the spatial contamination of the River Kymijoki, South-Eastern Finland, and the coastal region of the Gulf of Finland with PCDD/Fs and mercury. The findings of ecotoxicologial and human health studies are also reported, including environmental and human risk assessments. Sediments from the River Kymijoki, draining into the Gulf of Finland, have been heavily polluted by the pulp and paper industry and by chemical industries. A wood preservative, known as Ky-5, was manufactured in the upper reaches of the river between 1940 and 1984 causing severe pollution of river sediments with polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF). Moreover, the sediments have been polluted with mercury (Hg) from chlor-alkali production and the use of Hg as a slimicide in pulp and paper manufacturing. Materials and methods  An extensive sediment survey was conducted as well as sediment transport modeling, toxicity screening of sediment invertebrates, and a survey of contaminant bioaccumulation in invertebrates and fish. Studies on human exposure to PCDD/Fs and the possible effects on hypermineralization of teeth as well as an epidemiological study to reveal increased cancer risk were also conducted. An assessment of the ecological and human health risks with a null hypothesis (no remediation) was undertaken. Results  The sediment survey revealed severe contamination of river and coastal sediments with PCDD/Fs and Hg. The total volume of contaminated sediments was estimated to reach 5 × 10⁶ m³ and hot spots with extremely high concentrations (max 292,000 ng g⁻¹ or 1,060 ng I-TEQ g⁻¹ d.w.) were located immediately downstream from the pollution source (approximately 90,000 m³). Sediment contamination was accompanied by changes in benthic assemblages, but direct effects were masked by many factors. The fish showed only slightly elevated PCDD/F levels in muscle, but orders of magnitude higher in the liver compared with reference freshwater sites and the Baltic Sea. The concentrations in human fat did not reveal high human exposure in the Kymijoki area in general and was lower than in sea fishermen. The relative risk for total cancer among farmers was marginally higher (RR = 1.13) among those living close to the river, compared with farmers living further away, and the possibility of increased cancer risk cannot be ruled out. A conservative risk assessment revealed that the present probability of exceeding the WHO upper exposure limit of 4 pg WHO-TEQ kg⁻¹ d⁻¹ for PCDD/Fs and DL-PCBs was 6%. The probability of exceeding the WHO limit value of 0.23 μg kg⁻¹ d⁻¹ for methyl mercury was estimated to be notably higher at 62%. Based on these studies and the estimated risks connected with different remediation techniques a general remediation plan with cost benefit analysis was generated for several sub-regions in the river. Dredging, on-site treatment, and a close disposal of the most contaminated sediments (90,000 m³) was suggested as the first phase of the remediation. The decision regarding the start of remediation will be made during autumn 2008. Conclusions  The sediments in the River Kymijoki are heavily polluted with PCDD/Fs and mercury from earlier chlorophenol, chlor-alkali, and pulp and paper manufacturing. A continuous transport of contaminants is taking place to the Gulf of Finland in the Baltic Sea. The highly increased PCDD/F and Hg levels in river sediments pose an ecotoxicological risk to benthic fauna, to fish-eating predators and probably to human health. The risks posed by mercury exceed those from PCDD/Fs and need to be evaluated for (former) chlor-alkali sites and other mercury releasing industries as one basis for remediation decision making. Recommendations and perspectives  The studies form the basis of a risk management strategy and a plan for possible remediation of contaminated sediments currently under consideration in the Southeast Finland Regional Environment Centre. It is recommended that a detailed restoration plan for the most seriously contaminated areas should be undertaken. Based on current knowledge, the restoration of the whole river is not feasible, considering the current risk caused by the contaminated sediment in the river and the costs of an extensive restoration project. The experiences gained in the present case should be utilized in the evaluation of PCDD/F- and mercury-contaminated sites in other countries. The case demonstrates that the historic reservoirs are of contemporary relevance and should be addressed, e.g., in the national implementation plans of the Stockholm Convention. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Assessment of Uncertainty in Long-Term Mass Balances for Acidification Assessments: A MAGIC Model Exercise

Long-term (1860–2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47–62 or 42–47 meq m⁻² year⁻¹, depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (ΔANC ca. 10–41 μeq l⁻¹) and pH (ca. ΔpH = 0.1–0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.     

Seasonal patterns of the bacterioplankton community composition in a lake threatened by a pesticide disposal site

Background aim and scope  

The objective of the study was to determine the effects of ca. 35 years of pesticide contamination (pesticide dump—PD) of Lake Szeląg Wielki (located in the north-eastern Poland) on changes in the microbial communities of aquatic ecosystems. In the years 2008–2009, analyses were carried out for seasonal changes in the quantity and composition of bacterioplankton in the lake examined, which is of high significance to the tourism and fishing industries and is located in the vicinity of an area subjected to reclamation after a pesticide dump.     

Estimation of Nitrogen and Phosphorus in Effluent from the Striped Catfish Farming Sector in the Mekong Delta,Vietnam

In this study an attempt is made to estimate nitrogen and phosphorus discharged to the environment from the striped catfish (Pangasianodon hypophthalmus) farming sector in the Mekong Delta (8°33′–10°55′N, 104°30′–106°50′E), South Vietnam. The sector accounted for 687,000 t production in 2007 and 1,094,879 t in 2008, with over 95% of the produce destined for export to over 100 countries. Commercial and farm-made feeds are used in catfish farming, currently the former being more predominant. Nitrogen discharge levels were similar for commercial feeds (median 46.0 kg/t fish) and farm-made feeds (median 46.8 kg/t fish); whilst, phosphorus discharge levels for commercial feeds (median 14.4 kg/t fish) were considerably lower than for farm-made feeds (median 18.4 kg/t fish). Based on the median nutrient discharge levels for commercial feeds, striped catfish production in the Mekong Delta discharged 31,602 t N and 9,893 t P, and 50,364 t N and 15,766 t P in 2007 and 2008, respectively. However, the amount of nutrients returned directly to the Mekong River may be substantially less than this as a significant proportion of the water used for catfish farming as well as the sludge is diverted to other agricultural farming systems. Striped catfish farming in the Mekong Delta compared favourably with other cultured species, irrespective of the type of feed used, when the total amounts of N and P discharged in the production of a tonne of production was estimated.     

DOC removal paradigms in highly humic aquatic ecosystems

Background, aim, and scope  Dissolved humic substances (HS) usually comprise 50–80% of the dissolved organic carbon (DOC) in aquatic ecosystems. From a trophic and biogeochemical perspective, HS has been considered to be highly refractory and is supposed to accumulate in the water. The upsurge of the microbial loop paradigm and the studies on HS photo-degradation into labile DOC gave rise to the belief that microbial processing of DOC should sustain aquatic food webs in humic waters. However, this has not been extensively supported by the literature, since most HS and their photo-products are often oxidized by microbes through respiration in most nutrient-poor humic waters. Here, we review basic concepts, classical studies, and recent data on bacterial and photo-degradation of DOC, comparing the rates of these processes in highly humic ecosystems and other aquatic ecosystems. Materials and methods  We based our review on classical and recent findings from the fields of biogeochemistry and microbial ecology, highlighting some odd results from highly humic Brazilian tropical lagoons, which can reach up to 160 mg C L⁻¹. Results and discussion  Highly humic tropical lagoons showed proportionally lower bacterial production rates and higher bacterial respiration rates (i.e., lower bacterial growth efficiency) than other lakes. Zooplankton showed similar δ¹³C to microalgae but not to humic DOC in these highly humic lagoons. Thus, the data reviewed here do not support the microbial loop as an efficient matter transfer pathway in highly humic ecosystems, where it is supposed to play its major role. In addition, we found that some tropical humic ecosystems presented the highest potential DOC photo-chemical mineralization (PM) rates reported in the literature, exceeding up to threefold the rates reported for temperate humic ecosystems. We propose that these atypically high PM rates are the result of a joint effect of the seasonal dynamics of allochthonous humic DOC input to these ecosystems and the high sunlight incidence throughout the year. The sunlight action on DOC is positive to microbial consumption in these highly humic lagoons, but little support is given to the enhancement of bacterial growth efficiency, since the labile photo-chemical products are mostly respired by microbes in the nutrient-poor humic waters. Conclusions  HS may be an important source of energy for aquatic bacteria in humic waters, but it is probably not as important as a substrate to bacterial growth and to aquatic food webs, since HS consumption is mostly channeled through microbial respiration. This especially seems to be the case of humic-rich, nutrient-poor ecosystems, where the microbial loop was supposed to play its major role. Highly humic ecosystems also present the highest PM rates reported in the literature. Finally, light and bacteria can cooperate in order to enhance total carbon degradation in highly humic aquatic ecosystems but with limited effects on aquatic food webs. Recommendations and perspectives  More detailed studies using C- and N-stable isotope techniques and modeling approaches are needed to better understand the actual importance of HS to carbon cycling in highly humic waters.     

Water-soluble main ions in precipitation over the southeastern Adriatic region: chemical composition and long-range transport

Background, aim and scope  

Precipitation samples collected from 1995 to 2000 at meteorological station in the eastern outskirts of Herceg Novi (Montenegro) were analysed on Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^–, SO₄ ^2–, NO₃ ^– and NH₄ ⁺. Four-day backward trajectory simulations were conducted during the precipitation period to investigate the regional transport of main ions and their deposition in the region of the southeastern Adriatic Sea. The air mass trajectories were classified into six trajectory categories by the origin and direction of their approach to Herceg Novi.     

Temporal,spatial characteristics and uncertainty of biogenic VOC emissions in the Pearl River Delta region,China

Using the Global Biosphere Emissions and Interactions System model (GloBEIS), 3 × 3 km gridded and hourly biogenic volatile organic compound (BVOC) emissions in the Pearl River Delta (PRD) were estimated for the year 2006. The study used newly available land cover database, observed meteorological data, and recent measurements of emission rates for tree species in China. The results show that the total BVOC emission in the PRD region in 2006 was 296 kt (2.2 × 10¹¹ gC), of which isoprene contributes about 25% (73 kt, 6.4 × 10¹⁰ gC), monoterpenes about 34% (102 kt, 8.9 × 10¹⁰ gC), and other VOCs (OVOC) about 41% (121 kt, 6.8 × 10¹⁰ gC). BVOC emissions in the PRD region exhibit a marked seasonal pattern with the peak emission in July and the lowest emission in January, and are mainly distributed over the outlying areas of the PRD region, where the economy and land use are less developed. The uncertainties in BVOC emission estimates were quantified using Monte Carlo simulation; the results indicate high uncertainties in isoprene emission estimates, with a relative error of ?82 to +177%, ranging from 12.4 to 186.4 kt; ?41 to +58% uncertainty for monoterpenes emissions, ranging from 67.7 to 181.9 kt; and ?26 to +30% uncertainty in OVOC emissions, ranging from 88.8 to 156.2 kt on the 95% confidence intervals. The key uncertainty sources include emission factors and the model empirical coefficients α, C_T1, C_L, and E_opt for estimating isoprene emission, and emission factors and foliar density for estimating monoterpenes and OVOC emissions. This implies that determining these empirical coefficient values properly and conducting more field measurements of emission rates of tree species are key approaches for reducing uncertainties in BVOC emission estimates. Improving future BVOC emission inventory work in the PRD region requires giving priority to research on shrub land, coniferous forests, and irrigated cropland and pasture.     

Large-scale risk assessment of polycyclic aromatic hydrocarbons in shoreline sediments from Saudi Arabia: Environmental legacy after twelve years of the Gulf war oil spill

A large-scale assessment of polycyclic aromatic hydrocarbons (PAHs) from the 1991 Gulf War oil spill was performed for 2002-2003 sediment samples (n = 1679) collected from habitats along the shoreline of Saudi Arabia. Benthic sediment toxicity was characterized using the Equilibrium Partitioning Sediment Benchmark Toxic Unit approach for 43 PAHs (ESBTU_FCV,43). Samples were assigned to risk categories according to ESBTU_FCV,43 values: no-risk (≤1), low (>1-≤2), low-medium (>2-≤3), medium (>3-≤5) and high-risk (>5). Sixty seven percent of samples had ESBTU_FCV,43 > 1 indicating potential adverse ecological effects. Sediments from the 0-30 cm layer from tidal flats, and the >30-<60 cm layer from heavily oiled halophytes and mangroves had high frequency of high-risk samples. No-risk samples were characterized by chrysene enrichment and depletion of lighter molecular weight PAHs, while high-risk samples showed little oil weathering and PAH patterns similar to 1993 samples. North of Safaniya sediments were not likely to pose adverse ecological effects contrary to sediments south of Tanaqib. Landscape and geomorphology has played a role on the distribution and persistence in sediments of oil from the Gulf War.     

Biogeochemical dynamics of perfluorinated alkyl acids and sulfonates in the River Seine (Paris, France) under contrasting hydrological conditions

The biogeochemical dynamics of 15 perfluorinated compounds (PFCs) were investigated in a heavily urbanised river (River Seine, Paris, France). The target compounds included C4-C10 sulfonates and C5-C14 acids; eleven PFCs were detected and ∑PFCs ranged between 31 and 91 ng L⁻¹ (median: 47 ng L⁻¹). The molecular pattern was dominated by the perfluoroalkyl sulfonates PFHxS and PFOS (>54% of ∑PFCs), which were the only PFCs quantified in both the dissolved and particulate phases. For these PFCs, the sorbed fraction positively correlated with suspended sediment levels. Total PFC levels negatively correlated with river flow rate, which varied between 150 and 640 m³ s⁻¹. This suggests the predominance of point sources (likely WWTP effluent discharge), but a contribution of non-point sources such as combined sewer overflow could not be excluded. The annual PFC mass flow was estimated at 500 kg, which is less than observed for other large European rivers.     

Vertical transport of ozone and CO during super cyclones in the Bay of Bengal as detected by Tropospheric Emission Spectrometer

Vertical profiles of carbon monoxide (CO) and ozone retrieved from Tropospheric Emission Spectrometer have been analyzed during two super cyclone systems Mala and Sidr. Super cyclones Mala and Sidr traversed the Bay of Bengal (BOB) region on April 24–29, 2006 and November 12–16, 2007 respectively. The CO and ozone plume is observed as a strong enhancement of these pollutants in the upper troposphere over the BOB, indicating deep convective transport. Longitude–height cross-section of these pollutants shows vertical transport to the upper troposphere. CO mixing ratio ~90 ppb is observed near the 146-mb level during the cyclone Mala and near 316 mb during the cyclone Sidr. Ozone mixing ratio ~60–100 ppb is observed near the 316-mb level during both the cyclones. Analysis of National Centers for Environmental Prediction (NCEP) reanalysis vertical winds (omega) confirms vertical transport in the BOB.     

Current State of the Altai Glaciers (Russia) and Trends Over the Period of Instrumental Observations 1952–2008

Results of research into climate and glacier dynamics in the Altai Mountains (Russia) over the period of instrumental observations (1952–2008) are presented in this article. About 1030 glaciers with a total area of 805 km² and volume of 42.5 km³ have been recorded in the Altai Region. The average summer air temperature in different regions of the Altai has increased during the study period from about 0.2°C (Aktru) to 1.1°C (Akkem). The annual atmospheric precipitation rate has also increased, by 8–10%. Since 1952, the glacier area in different regions of the Altai has decreased by 9–27%, and volume by 12–24%. By 2008, as a result of degradation, the total number of glaciers was 953 with an area of 724 km² and volume of 38 km³.     

A field survey—Staroe lake suffering from atmospheric deposition in the region north of the Arctic Circle

Background, aim, and scope  The Arctic holds large stores of minerals, and extracted materials are provided to the world’s economy; in this sense, the Arctic issue associated with mining is not local but global. In a part of the Arctic region (the Kola Peninsula, 66–70° N and 28–41° E), metal levels are generally elevated in the lake sediment. There is a question as to what results in elevated metal levels—a natural process (naturally abundant minerals) or an anthropogenic process (mining and metallurgy). In terms of solving this question, Staroe lake located on the Kola Peninsula was researched as a case study. Materials and methods  The following parameters were determined in relation with Staroe lake: (1) the current quality of the lake’s water—each 1,000-ml sample was collected at a surface point and a deep point (near the bottom layer), and the collected samples were directly analyzed after filtration; (2) atmospheric bulk deposition—bulk deposition was collected using a set of three rainwater samplers near the lake. In addition, bulk deposition was collected in a background site (250 km to the southwest of the smelter complex) as a reference; and (3) sediment profile (plus principal component analysis)—lake-bottom sediment was collected by an open-gravimetric column sampler equipped with an automatic diaphragm. After collection, the sample columns were cut at a 1-cm interval for analysis. Eigenvalues and variances by factor were calculated from the correlation coefficients. Results  The obtained data show that (1) naturally poor elements (Cu, Ni, Si, and SO₄ ²⁻) dominantly influence the lake’s water quality; (2) they are transported from the anthropogenic sources to the study lake through the atmospheric pathway; (3) mainly the contents of Cu, Ni, Sr, and Ca have influenced the sediment quality since the 1950s, corresponding to the industrial movement; and (4) Cu, Ni, and Sr originate from an anthropogenic source (smelter), and Ca originates from both natural and anthropogenic sources. Discussion  As compared with the Russian standard (San Pin 2.1.980–00), the contents of NO₃ ⁻ (50.3 ± 0.1 mg l⁻¹) and particulates (2.3 ± 0.2 mg l⁻¹) exceeded the standard levels (0.7 mg l⁻¹ NO₃ ⁻ and 45 mg l⁻¹ particulates); Staroe lake may be slightly contaminated. However, the contamination factor (comparison with the background data) implies that Staroe lake is considerably contaminated. There is a strong possibility that fine overburden detritus (<0.1 mm diameter) may be transported from an open pit to the study lake by natural forces such as wind. Although it is difficult to suppose that one factor dominantly affects the sediment quality, it follows from a factor analysis that factors 1 and 2 account for about 70% of the total variance: Factor 1 is the most dominant, and factor 2 is the second most dominant in the variability of sediment quality. It is considered that Cu, Sr, and Ni in factor 1 originate from anthropogenic sources because they are poor in sediment rocks. Conclusions  The field survey conducted in Staroe lake can give the following answers to the key objectives: (1) The present water quality is affected by Cu, Ni, Si, and SO₄ ²⁻ in light of the contamination factor, and these elements originate from anthropogenic sources (the smelter and the open pit) and are transported to the lake through the atmospheric pathway; (2) the sediment profile and statistic analysis show that the lake quality has been influenced by deposition of metals since the 1950s; and (3) Cu, Ni, Sr, and Ca have influenced the sediment quality in light of the most dominant factor—Cu, Ni, and Sr originate from an anthropogenic source, whereas Ca comes from both natural and anthropogenic sources. Recommendations and perspectives  The presented lake survey shows that the dispersion of human-related pollutants via the atmospheric pathway takes place in the Arctic region. If the current pollution continues without countermeasures, the high-latitude environment may lose its original characteristics; hence, this subject is important when considering how to implement a wide range of environmental protection measures in the Arctic.     

Simulating Dissolved Organic Carbon Dynamics at the Swedish Integrated Monitoring Sites with the Integrated Catchments Model for Carbon,INCA-C

Surface water concentrations of dissolved organic carbon ([DOC]) are changing throughout the northern hemisphere due to changes in climate, land use and acid deposition. However, the relative importance of these drivers is unclear. Here, we use the Integrated Catchments model for Carbon (INCA-C) to simulate long-term (1996–2008) streamwater [DOC] at the four Swedish integrated monitoring (IM) sites. These are unmanaged headwater catchments with old-growth forests and no major changes in land use. Daily, seasonal and long-term variations in streamwater [DOC] driven by runoff, seasonal temperature and atmospheric sulfate (SO₄ ²⁻) deposition were observed at all sites. Using INCA-C, it was possible to reproduce observed patterns of variability in streamwater [DOC] at the four IM sites. Runoff was found to be the main short-term control on [DOC]. Seasonal patterns in [DOC] were controlled primarily by soil temperature. Measured SO₄ ²⁻ deposition explained some of the long-term [DOC] variability at all sites.     

Spatial trend and pollution assessment of total mercury and methylmercury pollution in the Pearl River Delta soil, South China

Total mercury (THg) and methylmercury (MeHg) were measured in large number of soil samples collected from areas with different types of land use, different depth in the Pearl River Delta (PRD) of South China. THg and MeHg concentrations ranged from 16.7 to 3320 ng g⁻¹ and 0.01 to 1.34 ng g⁻¹, respectively. THg levels are highest in the top 0-20 cm soil layer, and decrease from the surface to bottom layer soil. Spatial variation was observed with different types of land use. Urban parks had the highest concentrations and the other areas tended to decrease in the order of residential areas, industrial areas, vegetable fields, cereal fields, and woodlands. Temporal variation was also noted, and two relatively high THg contamination zones located in the northwestern part of the PRD have significantly expanded over the last two decades. Both THg and MeHg concentrations were correlated significantly with soil organic matter (OM), but not with soil pH. THg pollution status was evaluated using two assessment methods.     

Atmospheric chemistry of HFE-7000 (CF(3)CF (2)CF (2)OCH (3)) and 2,2,3,3,4,4,4-heptafluoro-1-butanol (CF (3)CF (2)CF (2)CH (2)OH): kinetic rate coefficients and temperature dependence of reactions with chlorine atoms

Background, aim, and scope  The adverse environmental impacts of chlorinated hydrocarbons on the Earth’s ozone layer have focused attention on the effort to replace these compounds by nonchlorinated substitutes with environmental acceptability. Hydrofluoroethers (HFEs) and fluorinated alcohols are currently being introduced in many applications for this purpose. Nevertheless, the presence of a great number of C–F bonds drives to atmospheric long-lived compounds with infrared absorption features. Thus, it is necessary to improve our knowledge about lifetimes and global warming potentials (GWP) for these compounds in order to get a complete evaluation of their environmental impact. Tropospheric degradation is expected to be initiated mainly by OH reactions in the gas phase. Nevertheless, Cl atoms reaction may also be important since rate constants are generally larger than those of OH. In the present work, we report the results obtained in the study of the reactions of Cl radicals with HFE-7000 (CF₃CF₂CF₂OCH₃) (1) and its isomer CF₃CF₂CF₂CH₂OH (2). Materials and methods  Kinetic rate coefficients with Cl atoms have been measured using the discharge flow tube–mass spectrometric technique at 1 Torr of total pressure. The reactions of these chlorofluorocarbons (CFCs) substitutes have been studied under pseudo-first-order kinetic conditions in excess of the fluorinated compounds over Cl atoms. The temperature ranges were 266–333 and 298–353 K for reactions of HFE-7000 and CF₃CF₂CF₂CH₂OH, respectively. Results  The measured room temperature rate constants were k(Cl+CF₃CF₂CF₂OCH₃) = (1.24 ± 0.28) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹and k(Cl+CF₃CF₂CF₂CH₂OH) = (8.35 ± 1.63) × 10⁻¹³ cm³ molecule⁻¹ s⁻¹ (errors are 2σ + 10% to cover systematic errors). The Arrhenius expression for reaction 1 was k ₁(266–333 K) = (6.1 ± 3.8) × 10⁻¹³exp[−(445 ± 186)/T] cm³ molecule⁻¹ s⁻¹ and k ₂(298–353 K) = (1.9 ± 0.7) × 10⁻¹²exp[−(244 ± 125)/T] cm³ molecule⁻¹ s⁻¹ (errors are 2σ). The reactions are reported to proceed through the abstraction of an H atom to form HCl and the corresponding halo-alkyl radical. At 298 K and 1 Torr, yields on HCl of 0.95 ± 0.38 and 0.97 ± 0.16 (errors are 2σ) were obtained for CF₃CF₂CF₂OCH₃ and CF₃CF₂CF₂CH₂OH, respectively. Discussion  The obtained kinetic rate constants are related to the previous data in the literature, showing a good agreement taking into account the error limits. Comparing the obtained results at room temperature, k ₁ and k ₂, HFE-7000 is significantly less reactive than its isomer C₃F₇CH₂OH. A similar behavior has been reported for the reactions of other fluorinated alcohols and their isomeric fluorinated ethers with Cl atoms. Literature data, together with the results reported in this work, show that, for both fluorinated ethers and alcohols, the kinetic rate constant may be considered as not dependent on the number of –CF₂– in the perfluorinated chain. This result may be useful since it is possible to obtain the required physicochemical properties for a given application by changing the number of –CF₂– without changes in the atmospheric reactivity. Furthermore, lifetimes estimations for these CFCs substitutes are calculated and discussed. The average estimated Cl lifetimes are 256 and 38 years for HFE-7000 and C₃H₇CH₂OH, respectively. Conclusions  The studied CFCs’ substitutes are relatively short-lived and OH reaction constitutes their main reactive sink. The average contribution of Cl reactions to global lifetime is about 2% in both cases. Nevertheless, under local conditions as in the marine boundary layer, τ _Cl values as low as 2.5 and 0.4 years for HFE-7000 and C₃H₇CH₂OH, respectively, are expected, showing that the contribution of Cl to the atmospheric degradation of these CFCs substitutes under such conditions may constitute a relevant sink. In the case of CF₃CF₂CF₂OCH₃, significant activation energy has been measured, thus the use of kinetic rate coefficient only at room temperature would result in underestimations of lifetimes and GWPs. Recommendations and perspectives  The results obtained in this work may be helpful within the database used in the modeling studies of coastal areas. The knowledge of the atmospheric behavior and the structure–reactivity relationship discussed in this work may also contribute to the development of new environmentally acceptable chemicals. New volatile materials susceptible of emission to the troposphere should be subject to the study of their reactions with OH and Cl in the range of temperature of the troposphere. The knowledge of the temperature dependence of the kinetic rate constants, as it is now reported for the case of reactions 1 and 2, will allow more accurate lifetimes and related magnitudes like GWPs. Nevertheless, a better knowledge of the vertical Cl tropospheric distribution is still required.     

The Effects of Hypoxia on Sediment Nitrogen Cycling in the Baltic Sea

Primary production in the eutrophic Baltic Sea is limited by nitrogen availability; hence denitrification (natural transformation of nitrate to gaseous N₂) in the sediments is crucial in mitigating the effects of eutrophication. This study shows that dissimilatory nitrate reduction to ammonium (DNRA) process, where nitrogen is not removed but instead recycled in the system, dominates nitrate reduction in low oxygen conditions (O₂ <110 μM), which have been persistent in the central Gulf of Finland during the past decade. The nitrogen removal rates measured in this study show that nitrogen removal has decreased in the Gulf of Finland compared to rates measured in mid-1990s and the decrease is most likely caused by the increased bottom water hypoxia.     

NOX fluxes from three kinds of agricultural lands in the Yangtze Delta,China

Static chamber method was adopted to measure the surface exchanges of NO and NO₂ between three kinds of agricultural lands and the atmosphere during spring–summer period in the Yangtze Delta, China. The average NO fluxes were 20.9, 27.4 and 21.4 ng N m⁻² s⁻¹, respectively, for cabbage (CA, cultivation of celery occurred along with cabbage), potato (PO) and soybean (SY) fields. The average NO₂ fluxes were −1.12, 0.93 and −0.68 ng N m⁻² s⁻¹, respectively, for the cabbage, potato and soybean fields. Apparently, negative linear correlation was found between the NO₂ fluxes from the CK plot (tilled conventionally but did not cultivate any seeds) and its ambient concentrations, and the compensation point was calculated to be 0.92 ppbv. The total NO emission from the vegetable lands and SY land in this region during spring–summer period was roughly estimated to be 15.9 Gg N, which accounted for about 11.2% of the estimated value of total NO emissions in the July of 1999 from Chinese agricultural fields.     

Tracking historical lead pollution in the coastal area adjacent to the Yangtze River Estuary using lead isotopic compositions

The rapid economic development in the Yangtze River Delta (YRD), China in the last three decades has had a significant impact on the environment of the East China Sea (ECS). Lead isotopic compositions of a ²¹⁰Pb dated sediment core collected from the coastal ECS adjacent to the Yangtze River Estuary were analyzed to track the Pb pollution in the region. The baseline Pb concentration in the coastal ECS sediments before the industrialization in China was 32 μg g⁻¹, and the corresponding ²⁰⁶Pb/²⁰⁷Pb ratio was 1.195. The high-resolution profiles of Pb flux and ²⁰⁶Pb/²⁰⁷Pb ratios had close relationships with the economic development and the history of the use of leaded gasoline in China, and they were clearly different from those of most European countries and United States.