Biogeochemical Indicators Research Articles

Reduction in mercury bioavailability to Asian clams (Corbicula fluminea) and changes in bacterial communities in sediments with activated carbon amendment

Activated carbon (AC) amendment is considered as one of the alternatives for managing and remediating mercury (Hg) contaminated sediments because of its high sorptive capacity and potential to immobilize the contaminant. For this study, the underlying mechanisms that control the reduction of Hg bioavailability in AC-amended estuarine sediments were investigated in box microcosm set-ups with 28-day Asian clam bioassay experiments. The application of diffusive gradients in thin film technique (DGT) revealed that the total mercury and methylmercury levels in sediment pore water decreased by 60%–75% in 1%–3% AC-amended sediments. This decrease subsequently led to a linear reduction in the Hg body burden in Asian clams, even at 1% sorbent mixing. These observations implied that AC amendment reduced the net flux of Hg into the pore water and overlying water, resulting in reduced Hg bioaccumulation in benthic organisms. The addition of AC to sediment also led to reduced dissolved organic carbon and several biogeochemical indicators (HS−, Mn, and Fe) in the pore water. Furthermore, the 16 S rRNA gene amplicon sequencing analysis revealed noticeable alterations in the microbial communities after AC amendment. The predominant phylum was Firmicutes in control sediment, Bacteroidetes in 1% AC-amended sediment, and Proteobacteria in both 2% and 3% AC-amended sediment samples. The genera-level analysis showed that the relative abundance of the Hg-methylators decreased as the level of AC amendment increased. These observations suggested that AC amendment decreased Hg bioavailability not only by physicochemical sorption but also by changing geochemical species and shifting the microbial community composition.

The influence of thyroid pathology on the course of periodontal disease in children and ways to correct it (Review)

Iodine deficiency diseases constitute an important medical and social problem, since a significant part of the territory of Ukraine is characterized by biogeochemical indicators of low iodine content in the environment, which is the cause of hypothyroidism development. At the same time, there are many other factors that can trigger the thyroid disorders in children. Epidemiological studies carried out in the Carpathian region have shown that iodine deficiency of varying degrees is specific to this area. Professor M.M. Kovalev's in-depth study of the causes of goitre in Bukovyna showed that along with iodine deficiency, macro- and micronutrient deficiencies associated with certain regions play an important role. Iodine deficiency promotes goitrogenesis and decreases the secretory capacity of the thyroid gland. As a result of reduced intrathyroid iodine in the gland, diiodothyrosine synthesis decreases and monoiodothyrosine increases, the hormone ratio increases due to an increase in the more biologically active triiodothyronine. This compensates for the euthyroid state against the background iodine deficiency. An adaptive manifestation of iodine deficiency is goitre, considered being the main sign of iodine deficiency; as iodine deficiency or thyroid hormone requirements increase, goiter size increases and more severe forms of thyroopathology develop. Iodine deficiency is common in many countries of the world. The analysis of the research data has shown the multifactorial nature of the etiology and pathogenesis of periodontal diseases in children, as well as the significant impact of thyroid disorders on the condition of the human dentition. In this regard, the study of cause-effect relationships between the initial manifestations of thyroid pathology and periodontal tissue changes in children seems relevant and promising in terms of improving methods of diagnosis, prevention and treatment. Keywords: periodontium, diffuse non-toxic goitre, children.

Effect of elevation, season and accelerated snowmelt on biogeochemical processes during isolated conifer needle litter decomposition.

Increased drought and temperatures associated with climate change have implications for ecosystem stress with risk for enhanced carbon release in sensitive biomes. Litter decomposition is a key component of biogeochemical cycling in terrestrial ecosystems, but questions remain regarding the local response of decomposition processes to climate change. This is particularly complex in mountain ecosystems where the variable nature of the slope, aspect, soil type, and snowmelt dynamics play a role. Hence, the goal of this study was to determine the role of elevation, soil type, seasonal shifts in soil moisture, and snowmelt timing on litter decomposition processes. Experimental plots containing replicate deployments of harvested lodgepole and spruce needle litter alongside needle-free controls were established in open meadows at three elevations ranging from 2,800–3,500 m in Crested Butte, Colorado. Soil biogeochemistry variables including gas flux, porewater chemistry, and microbial ecology were monitored over three climatically variable years that shifted from high monsoon rains to drought. Results indicated that elevation and soil type influenced baseline soil biogeochemical indicators; however, needle mass loss and chemical composition were consistent across the 700 m elevation gradient. Rates of gas flux were analogously consistent across a 300 m elevation gradient. The additional variable of early snowmelt by 2–3 weeks had little impact on needle chemistry, microbial composition and gas flux; however, it did result in increased dissolved organic carbon in lodgepole porewater collections suggesting a potential for aqueous export. In contrast to elevation, needle presence and seasonal variability of soil moisture and temperature both played significant roles in soil carbon fluxes. During a pronounced period of lower moisture and higher temperatures, bacterial community diversity increased across elevation with new members supplanting more dominant taxa. Microbial ecological resilience was demonstrated with a return to pre-drought structure and abundance after snowmelt rewetting the following year. These results show similar decomposition processes across a 700 m elevation gradient and reveal the sensitivity but resilience of soil microbial ecology to low moisture conditions.

Environmental quality assessment by multiple biogeochemical indicators of an intertidal flat under anthropogenic influence from the southwest of Buenos Aires (Argentina)

Chemical measures combined with biological data (biomarkers) are recommended in monitoring programs of marine environments. In the present research, the use of multiples biogeochemical indicators allowed interrelating different environmental measurements to deepen the knowledge of the quality/status of the intertidal flat from Puerto Rosales (Bahia Blanca estuary, Argentina) subjected to anthropogenic pressure. The sediments from this site presented a eutrophic status and high organic matter concentration with high nutritional value for the benthic community. The TPR/TCH ratio (~ 10) would evidence the untreated sewage discharge contribution and increments in protein content due to the complexation of nitrogen during phytodetritus accumulation and degradation. Trace metals levels in the fine sediments were lower than those recommended by international guides for uncontaminated sites. In the sediments, except Cu, all metals analyzed were rarely associated with adverse biological effects. Finally, metallothioneins levels in the burrowing crab Neohelice granulata were lower than those found in the literature and significantly higher in females than in males. Even though the different analyses and indices performed indicate that this intertidal flat is in good environmental condition, the wastewater discharge influenced it. Thus, it is advisable to continue with this kind of study by applying multi-combined proxies in this and other impacted tidal flats.

Woody artificial plantations as a significant factor of the sustainable development at mining & metallurgical area

The relevance of our research is determined by the need to find practical measures that will be aimed of the sustainable development formation and maintenance at mining and metallurgical areas by used of artificial woody plantation. The main objective of this work was on the standpoint of the ecosystem approach to consider the artificial woody plantations as a significant factor for sustainable development paradigm implementation at Kryvyi Rih mining and metallurgical district (Central Ukraine). During 2015-2020, by classical methods were studied the natural forest ecosystems and the artificial forest plantations, which are located in contrast ecological and environmental conditions. Numerous scientific papers about sustainable development have also served as materials for our work. At Kryvyi Rih mining and metallurgical district the leading characteristics of artificial woody plantations have a clear ecological and environmental conditionality. It is proved that in artificial woody plantations of this district tree species are in a state of stress. Therefore, these species lose stability due to the constant influence of adverse environmental factors of natural and anthropogenic genesis. The authors assume that the biogeochemical parameters of trees fallen can be considered one of the promising markers that determine the vitality / healthy of tree species and forecast the development of artificial woody plantations. It has been suggested that the artificial woody plantations at Kryvyi Rih mining and metallurgical area should acquire the status of one of the key factors that determine the sustainable development of this district and Ukraine as a whole. In practice, to achieve this goal, the following steps must be taken: (i) artificial woody plantation assessment, (ii) ecological and environment conditionality of artificial woody plantation current state ascertainment, (iii) sustainable model of artificial woody plantation development, (iv) sustainable management of artificial woody plantation, (v) sustainable development of artificial woody plantation. In the near future, it is recommended to optimize the Kryvyi Rih forest cover by 8-10%. The first step in streamlining and preliminary assessment of the artificial forest ecosystems sustainability is the use of biogeochemical indicators of the chemical circulation system relationship “Leaf precipitation -soil” as markers and predictors of the artificial forest current state in Kryvyi Rih District.

Specifying the approaches to geoinformation monitoring to assess the development dynamics of mining enterprises as natural-technological systems

Introduction. The article considers problems related to the need in a system of indicators assessing mining technological conditions variation based on mining dynamics monitoring as well as its harmful environmental impact, which is constant over an indefinite period of time. Besides, the introduction of a block of biogeochemical indicators into the general indicative system in order to develop effective methods of environmental rehabilitation is associated with the study of self-healing processes, which will allow managing these processes, thereby accelerating the formation of stable and well-functioning ecosystems. Research aim. Base on the research, the article aims to determine approaches to geoinformation monitoring to assess the dynamics of mining enterprises formation as integrated natural-technological systems in order to choose a strategy for the environmentally safe development of natural deposits and technogenic mineral formations. Methodology. An algorithm for assessing the dynamics of mining enterprises formation as naturaltechnological systems is considered as well as the main directions and tasks of geoinformation monitoring as a tool for controlling technical risks and compensating for environmental risks during the development of solid mineral deposits. Results. The article considers methodological aspects of systematic assessment of natural deposits and man-made formations development projects implementation based on geoinformation monitoring data. Besides, the dynamics of mining enterprises formation as natural-technological systems is proposed to be assessed based on the ideology of modeling transient processes where the object changes its parameters from some initial (initial) to prescribed (final) by the approved design documentation. The transition process at least involves: a transformed natural system, a technological system that changes or affects the natural one, and a socio-economic system being a complex where the organizational, financial and economic activities of the enterprise are implemented in management.

Microbial and Biogeochemical Indicators of Methane in Groundwater Aquifers of the Denver Basin, Colorado.

The presence of methane and other hydrocarbons in domestic-use groundwater aquifers poses significant environmental and human health concerns. Isotopic measurements are often relied upon as indicators of groundwater aquifer contamination with methane. While these parameters are used to infer microbial metabolisms, there is growing evidence that isotopes present an incomplete picture of subsurface microbial processes. This study examined the relationships between microbiology and chemistry in groundwater wells located in the Denver-Julesburg Basin of Colorado, a rapidly urbanizing area with active oil and gas development. A primary goal was to determine if microbial data can reliably indicate the quantities and sources of groundwater methane. Comprehensive chemical and molecular analyses were performed on 39 groundwater well samples from five aquifers. Elevated methane concentrations were found in only one aquifer, and both isotopic and microbial data support a microbial origin. Microbial parameters had similar explanatory power as chemical parameters for predicting sample methane concentrations. Furthermore, a subset of samples with unique microbiology corresponded with unique chemical signatures that may be useful indicators of methane gas migration, potentially from nearby coal seams interacting with the aquifer. Microbial data may allow for more accurate determination of groundwater contamination and improved long-term water quality monitoring compared solely to isotopic and chemical data in areas with microbial methane.

Combined Use of Diagnostic Fumarate Addition Metabolites and Genes Provides Evidence for Anaerobic Hydrocarbon Biodegradation in Contaminated Groundwater.

The widespread use of hydrocarbon-based fuels has led to the contamination of many natural environments due to accidental spills or leaks. While anaerobic microorganisms indigenous to many fuel-contaminated groundwater sites can play a role in site remediation (e.g., monitored natural attenuation, MNA) via hydrocarbon biodegradation, multiple lines of evidence in support of such bioremediation are required. In this study, we investigated two fuel-contaminated groundwater sites for their potential to be managed by MNA. Microbial community composition, biogeochemical indicators, fumarate addition metabolites, and genes diagnostic of both alkane and alkyl-monoaromatic hydrocarbon activation were assessed. Fumarate addition metabolites and catabolic genes were detected for both classes of hydrocarbon biodegradation at both sites, providing strong evidence for in situ anaerobic hydrocarbon biodegradation. However, relevant metabolites and genes did not consistently co-occur within all groundwater samples. Using newly designed mixtures of quantitative polymerase chain reaction (qPCR) primers to target diverse assA and bssA genes, we measured assA gene abundances ranging from 105–108 copies/L, and bssA gene abundances ranging from 105–1010 copies/L at the sites. Overall, this study demonstrates the value of investigating fuel-contaminated sites using both metabolites and genes diagnostic of anaerobic hydrocarbon biodegradation for different classes of hydrocarbons to help assess field sites for management by MNA.

Bacillus cereus, a geobiological marker for gold prospecting isolated from soil from the Jiaodong Gold Mine

An efficient method for new gold deposits exploration is of great interest as the existing deposits depleted. In this paper, we investigated the possibility of using B. cereus in the soil from Jiaodong Gold Mine as a biogeochemical indicator of gold. Cell counting, growth curve assay, SEM/TEM-EDS and X-ray Absorption Near Edge Spectroscopy (XANES) techniques were used to investigate the sporulation characteristics, reducing capability and detoxification mechanisms of the B. cereus strain in the environment containing gold. The results showed that: (1) The frequencies of B. cereus spores were higher in areas where elevated concentrations of Au were detected, which was not observed for other elements, such as As, Cu, Zn, Cd and Pb. (2) B.cereus has the ability to facilitated the solubilization of Au. The dissolved gold subsequently stimulated B.cereus spores formation, and mother cells release the contents of their cytoplasm to ameliorate gold toxicity. (3) Toxic Au (III)-complexe was reduced to nontoxic Au (0) nanoparticles by B. cereus. Before reduced to Au (0), cellular Au was coupled with the formation of AuS intermediate species. The results showed that B.cereus spores were confirmed to exist in the gold mine soil, and the reduction and detoxification of gold were mediated by the cytoplasm released by the mother cells, which led to the formation of gold nanoparticles.

Monitoring and forecasting of the Black Sea state in the international Copernicus programme

The article provides an overview of products created by the Copernicus Marine Environment Monitoring Service (Copernicus programme is coordinated and managed by the European Commission in partnership with the European Space Agency (ESA), EU Member States and EU agencies) and made publicly available. Products derived from numerical model calculations and satellite observations with spatial and temporal characterization for the Black Sea were considered. Examples are given of biogeochemical indicators visualization and physical analysis of the Black Sea region, designed to monitor and predict the state of the region for the rational, safe and efficient use and protection of marine resources.

Ecological Monitoring of the Unal Depression, Northern Ossetiya–Alania, Using Techniques of Biogeochemical Indication

The paper presents analysis of the accumulation of toxic and vital chemical elements in discrete links of the food chain under conditions of a biogeochemical province in relation to the accumulation of phytochelatins and metallothioneins in the leaves of white birch (Betula pubescens). Gradients of metal concentrations are determined in the soils with increasing distance from the Unal tailing dump and the effects of these gradients on the concentrations of the elements in birch leaves. Correlations are determined between the concentrations of toxic elements in the pulp and leaves separately for the native sample and water washout. A strong correlation was found between the total dissolved concentration of all metals and the total metallothionein and glutathione concentrations. It is hypothesized that the biochemical system of glutathione is more closely related to the accumulation of metals by plants than the system of metallothioneins. Estimates are made whether it is possible to apply the method of bioindication of the ecological state of a territory by determining the fluctuating asymmetry of birch leaves. This bioindication parameter was evaluated separately for each of the cardinal points. It is demonstrated that a high total concentrations of the metals in soils and birch leaves is correlated with an increase in the fluctuating asymmetry of the leaves and the concentration level of sulfur-bearing biological active compounds. The bioindication technique is however still far from perfect and is difficult to apply and, hence, requires further studies.

РЕДКОЗЕМЕЛЬНЫЕ И РАДИОАКТИВНЫЕ (TH, U) ЭЛЕМЕНТЫ В КОМПОНЕНТАХ ПРИРОДНОЙ СРЕДЫ НА ТЕРРИТОРИИ ТОМСКОЙ ОБЛАСТИ

Актуальность исследования обусловлена необходимостью рассмотрения взаимосвязей радиоактивных и редкоземельных элементов с точки зрения их высокой индикаторной роли в комплексе компонентов природной среды на локальных территориях, характеризующихся различными природно-техногенными условиями и условиями районирования территории с учетом биогеохимических показателей. Цель: рассмотрение взаимосвязей радиоактивных и редкоземельных элементов в комплексе компонентов природной среды на территории Томской области, характеризующейся различными природно-техногенными обстановками. Методы: основной метод исследования – инструментальный нейтронно-активационный анализ, который осуществлялся на базе исследовательского ядерного реактора Национального исследовательского Томского политехнического университета. Определено содержание двух радиоактивных – тория и урана, а также семи редкоземельных (La, Ce, Sm, Eu, Tb, Yb, Lu) элементов. Результаты. Оценено содержание редкоземельных и радиоактивных элементов в четырех параллельно отобранных и изученных компонентах природной среды на территории Томской области: почва, солевые отложения природных пресных вод (накипь), волосы и кровь человека. Содержание изученных элементов максимально для почв и накипи и значительно ниже в биосубстратах человека. Волосы и кровь человека как живые ткани характеризуются резким цериевым минимумом. В крови выявлен иттербиевый максимум, вероятно, связанный с нахождением этого элемента в виде металлорганических комплексов. Исследованы соотношения химических элементов, которые можно использовать в качестве индикаторов природно-техногенных обстановок. Проведено районирование Томской области по междуречьям бассейна реки Обь по частоте встречаемости аномальных содержаний редкоземельных и радиоактивных элементов во всех изученных компонентах.

Evaluating biogeochemical indicators of methanogenic conditions and thermodynamic constraints in peat

Burial of organic matter in deep peat deposits has already been experimentally demostrated to slow down or even inhibit anaerobic decomposition due to lack of diffusive transport and end-product accumulation. However, so far little is known about potential biogeochemical or thermodynamic indicators for the observed inhibition of further decomposition. For example, theoretical energy yields for methanogenesis, hydrogen partial pressures, stable isotope fractionation factors between CO2 and CH4, and electrochemical properties of dissolved organic matter have been proposed as thermodyamic indicators for such inhibition. To test the applicability and explanatory power of these indicators to identify conditions inhibiting organic matter decomposition, we incubated homogenized ombrotrophic peat for 300 days at 20 °C under diffusive flux conditions as control, and compared the observed effects to a treatment with vertical advective transport by water circulation and to a treatment in which both the unsaturated and water-saturated zone of the peat profile were kept anoxic. Results of energy yields of acetoclastic and hydrogenotrophic methanogenesis were compared to hydrogen partial pressures, to 13C isotope fractionation factors and to redox properties of dissolved organic matter as obtained from mediated electrochemical oxidation and reduction. While CO2 and CH4 production slowed substantially in the deep peat profile, a concomitant decrease of Gibs free energy yields available to hydrogenotrophic and acetoclastic methanogensis and hydrogen and acetate concentrations over time supported a thermodynamic constraint on methanogenesis. Although, energy yields for the hydrogenotrophic pathway were close to or below the theoretical energy minimum levels already after 15 days. Transiently elevated H2 concentrations, not related to actual methanogenesis rates were observed for about 150–225 days. Thereafter, hydrogen concentrations diminished to levels below thresholds to thermodynamically support ongoing methanogenesis. Thus even on incubation timescales of 150–225 days, steady-state hydrogen concentrations as would be expected from thermodynamic considerations did not adjust on the bulk scale of observation. Gibbs free energy estimates for methanogenesis based on hydrogen partial pressures were consequently biased and did not reach the minimum required threshold despite ovious net CH4 production. Ratios between electron accepting (EAC) and donating (EDC) capacity of dissolved organic matter, however, turned out to provide suitable indicators of predominant redox conditions along gradients, stabilizing at low values upon onset of methanogenesis. Thus, our study demonstrated that the thermodynamically driven slow down of decomposition in deep peat deposits, preventing the peat to decompose further, cannot be easily identified based on a single indicator. However, constant and high concentrations of decomposition end-products, indicating zero net turnover and low energy yields, and constantly low EAC/EDC ratios, indicating no further availability of terminal electron acceptors, seem to be characteristic of the onset of conditions inhibiting further significant decomposition of peat.

Changes in infaunal assemblage structure influence nutrient fluxes in sediment enriched by mussel biodeposition.

Although many studies have described the influence of bivalve aquaculture on the benthic environment, effects on benthic functional diversity are poorly known, as are links with ecosystem processes. We investigated the response of a benthic ecosystem in terms of taxonomic and functional diversity (infauna >500 μm), biogeochemical indicators (organic matter content, redox potential, sulfides level, bacteria) and metabolism (nutrient fluxes), subjected to various levels of mussel biodeposition as a general model of organic enrichment. Results show that local benthic conditions may recover fairly quickly depending on environmental conditions whereas modifications of the benthic community structure persist over a longer time scale with an impact on benthic ecosystem functioning. Fauna-mediated oxidation of the sediment likely increased nitrogen recycling through nitrification whereas binding and release of phosphorus to the water column seems to be driven by more complex processes. Results highlight the importance of species identity (ecological traits) on biogeochemical cycling and solute exchange across the sediment-water interface, with implications for the ecological functioning of exploited areas.

Deep-sea megabenthos communities of the Eurasian Central Arctic are influenced by ice-cover and sea-ice algal falls.

Quantitative camera surveys of benthic megafauna were carried out during the expedition ARK-XXVII/3 to the Eastern Central Arctic Basins with the research icebreaker Polarstern in summer 2012 (2 August-29 September). Nine transects were performed for the first time in deep-sea areas previously fully covered by ice, four of them in the Nansen Basin (3571-4066m) and five in the Amundsen Basin (4041-4384m). At seven of these stations benthic Agassiz trawls were taken near the camera tracks for species identification. Observed Arctic deep-sea megafauna was largely endemic. Several taxa showed a substantially greater depth or geographical range than previously assumed. Variations in the composition and structure of megabenthic communities were analysed and linked to several environmental variables, including state of the sea ice and phytodetritus supply to the seafloor. Three different types of communities were identified based on species dominating the biomass. Among these species were the actiniarian Bathyphellia margaritacea and the holothurians Elpidia heckeri and Kolga hyalina. Variations in megafaunal abundance were first of all related to the proximity to the marginal ice zone. Stations located closer to this zone were characterized by relatively high densities and biomass of B. margaritacea. Food supply was higher at these stations, as suggested by enhanced concentrations of pigments, organic carbon, bacterial cell abundances and nutrients in the sediments. Fully ice-covered stations closer to the North Pole and partially under multi-year ice were characterized by lower concentrations of the same biogeochemical indicators for food supply. These stations nevertheless hosted relatively high density and biomass of the holothurians E. heckeri or K. hyalina, which were observed to feed on large food falls of the sea-ice colonial diatom Melosira arctica. The link between the community structure of megafauna and the extent and condition of the Central Arctic sea-ice cover suggests that future climate changes may substantially affect deep ocean biodiversity.

‘Mixing-and-measuring’ surface-enhanced Raman scattering (SERS) detection of Bacillus cereus for potentially aiding gold mine field exploration

Bacillus cereus, a common soil bacterium, has been shown to act as a biogeochemical indicator for concealed mineralisations, e.g., vein-type Au deposits. Field and cultivation-free detection of Bacillus cereus in the presence of Au3+ and other metal ions is significantly important but still almost blank in current biogeochemical prospecting of gold mine system. Herein, a self-established simple approach was slightly improved to make silver nanoparticles (Ag NPs) rapidly concentrated on every bacterial cell, and highly strong and distinct surface-enhanced Raman scattering (SERS) signals of Bacillus cereus free from any native fluorescence have been obtained in a so called ‘mixing-and-measuring’ manner. Furthermore, SERS was used for the first time to our knowledge to investigate the impacts of different concentrations of metal ions on Bacillus cereus, and successfully utilized for distinguishing Au3+ ions from other species. A more convincing multi-Raman criterion based on Raman bands, and further the entire Raman spectrum in combination with statistical analysis (e.g., principal component analysis (PCA)) were found capable of detecting spectral differences of Bacillus cereus in the presence of metal ions (Au3+, Ag+, Cu2+ and Zn2+) with different concentrations. An interesting phenomenon has been found that except for Au3+ ions, the highest permissive concentration of other metal ions for the detected Bacillus cereus is up to 10 μg/mL possibly due to their resistance to Au. The results also indicate that an effective biogeochemical exploration technique of SERS spectral response may be developed, where Bacillus cereus spore counts are measured in the field and used as a pre-screening method to target areas useful for further sampling and complete geochemical analysis.

Migration and Biogeochemical Indication of Persistent Organic Pollutants

This paper addresses the character of migration and the level of ecotoxicity of the most hazardous groups of persistent organic pollutants in the biosphere: polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and organochlorine pesticides. Modern approaches to the monitoring of these compounds in various geospheres were evaluated. Based on new experimental data, methods were proposed for the biogeochemical indication and detoxification of persistent organochlorine pesticides in the organisms of higher mammals.

Isotopic biogeochemical indicators of evapotranspiration and nitrogen flows in a check‐dam catchment in the Loess Plateau, China

AbstractThe increasingly fragile environment and associative nitrogen (N) biogeochemical cycle have become critical environmental and ecological issues in China's Loess Plateau. However, N flow and N source for typical catchments remain poorly understood in the Loess Plateau. In this study, we measured concentrations and isotopic signatures of N, hydrogen (H), and oxygen (O) in both rainfall and river water. Results showed that baseflow variation in total nitrogen (TN) concentrations ranged from 0.16 to 32.70 mg L−1. The monthly TN deposition flux and monthly TN wet deposition concentration to river water were shown significant variations between rainy and dry seasons. The range of variation in δ2H values for rainfall and baseflow was from −90.0‰ to 19.8‰ and from −67.2‰ to −38.4‰, respectively, whereas δ18O–H2O values ranged from −12.1‰ to +2.7‰ and from −9.3‰ to −3.6‰, respectively. The Local Meteoric Water Line in the check‐dam catchment was δ2H = 7.35 δ18O + 2.29 (R2 = 0.93). Furthermore, NO3− δ15N and δ18O values in baseflow ranged from −2.0‰ to +20.5‰ and from +8.0‰ to +15.6‰, respectively. The results indicated that rainfall was affected by below‐cloud secondary evaporation and caused strong isotopic kinetic fractionation to occur during the precipitation process. The NO3− in runoff was mainly derived from the nitrification of soil organic matter and manure or sewage, for which the proportion of manure or sewage was from 50.5% to 83%.

Multiple biogeochemical indicators of environmental quality in tropical estuaries reveal contrasting conservation opportunities

Estuaries are under major impacts from pollution even when managed as conservation units. Here we used multiple biogeochemical indexes of contamination and trophic status, including faecal sterols, biopolymers and trace metals, to determine and compare environmental quality of two tropical estuaries with contrasting conservation status. In the metropolitan estuary, eutrophic/hypereutrophic conditions and high concentrations (>1.0 µg g−1) of coprostanol were spatially correlated to sources of raw sewage input. Unexpected eutrophic sediments were also detected at the estuarine reserve, but with low sewage contamination indicating that high organic availability and burial predominated. The natural or polluted eutrophic sediments were determined by comparing multiple contamination indexes, which indicated sediment contamination within the metropolitan estuary. This study indicates that the long-term conservation of estuarine ecosystems on the Atlantic coast of Brazil are threatened by a typically poor sewage treatment and suggests that estuarine sediment quality need to be evaluated by multiple proxies before estuaries can be included in spatial conservation planning.

Epiphyton Geochemistry in the Ivankovo Reservoir

Epiphyton chemistry was studied in the Ivankovo Reservoir; a large number of micro- and macroelements (Ag, Al, As, Ba, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Nd, Ni, P, Pb, S, Sc, Sr, Ti, V, Y, Yb, Zn, W) were determined with the use of up-to-date analytical methods. Comparative characteristics of the geochemistry of macrophyte epiphyton of different ecological groups is given for the Ivankovo Reservoir. The potential of epiphyton as a biogeochemical indicator of anthropogenic impact on the water body is examined.