Anomalous Gadolinium,Cerium, and Yttrium Contents in the Adige and Isarco River Waters and in the Water of Their Tributaries (Provinces Trento and Bolzano/Bozen,NE Italy)

Rare earth patterns of surface and groundwaters near big cities often show anthropogenic Gd (Gd_ant) anomalies in addition to geogenic Ce and Y anomalies. The Gd_ant anomaly is caused by very stable organic complexes, one of which is gadopentetic acid, Gd‐DTPA. Derivatives of this and similar compounds are used as contrast agents in magnetic resonance imaging (MRI) of the human blood system. The organic Gd complexes are stable enough to pass nearly unaffected through sewage treatment plants and are, thereafter, discharged into surface water systems. Water of the rapidly flowing Isarco/Eisack and Adige/Etsch rivers (Provinces of Trento and Bolzano/Bozen, NE Italy) and their tributaries show remarkable variations in anthropogenic Gd contents (Gd_ant). Low Gd_ant values are found on Monday and Tuesday, whereas high values are observed during the remaining weekdays. Reliable Gd_ant balances are calculated for the river system at the confluence of the Adige and its tributaries. At two places local decrease of Gd_ant indicates exfiltration of groundwater. It is demonstrated that Gd_ant can be used as a reliably conservative tracer to study the water budget in rapidly flowing alpine river systems. The studied different river waters show considerable negative Ce and positive Y anomalies. Negative Ce anomalies are caused by scavenging of Ce(III) by FeO(OH) precipitates and subsequent oxidation to CeO₂. Y anomalies are attributed to less sorption of Y than REE onto particulate matter. Thus, Y moves faster than REE. Both, Ce and Y anomalies, are of geogenic origin.     

Implementation of European marine policy: New water quality targets for German Baltic waters

A full re-calculation of Water Framework Directive reference and target concentrations for German coastal waters and the western Baltic Sea is presented, which includes a harmonization with HELCOM Baltic Sea Action Plan (BSAP) targets. Further, maximum allowable nutrient inputs (MAI) and target concentrations in rivers for the German Baltic catchments are suggested. For this purpose a spatially coupled, large scale and integrative modeling approach is used, which links the river basin flux model MONERIS to ERGOM-MOM, a three-dimensional ecosystem model of the Baltic Sea. The years around 1880 are considered as reference conditions reflecting a high ecological status and are reconstructed and simulated with the model system. Alternative approaches are briefly described, as well. For every WFD water body and the open sea, target concentrations for nitrogen and phosphorus compounds as well as chlorophyll a are provided by adding 50% to the reference concentrations. In general, the targets are less strict for coastal waters and slightly stricter for the sea (e.g. 1.2 mg/m³ chl.a summer average for the Bay of Mecklenburg), compared to current values. By taking into account the specifics of every water body, this approach overcomes the inconsistencies of earlier approaches. Our targets are well in agreement with the BSAP targets, but provide spatially refined and extended results. The full data are presented in Appendix A1 and A2.To reach the targets, German nitrogen inputs have to be reduced by 34%. Likely average maximum allowable concentrations in German Baltic rivers are between 2.6 and 3.1 mg N/l. However, the concrete value depends on the scenario and uncertainties with respect to atmospheric deposition. To our results, MAI according to the BSAP may be sufficient for the open sea, but are not sufficient to reach a good WFD status in German coastal waters.     

Organic carbon concentrations and transport in small mountain rivers,Panama

Tropical small mountainous rivers (SMRs) are increasingly recognized for their role in the global export of dissolved organic carbon (DOC) to the oceans. Here we utilize the Isthmus of Panama as an ideal place to provide first-order estimates of DOC yields across a wide assemblage of bedrock lithologies and land cover practices. Samples for dissolved organic carbon (DOC) analysis were collected across Panama along an E–W transect from the central Panama area to the Costa Rican border for 24 mainstem rivers, 3 large tributary rivers, and one headwater stream. Sampling occurred during both the wet and the dry seasons. DOC concentrations during the wet season are higher than during the dry season in all but three of the rivers. Concentrations vary greatly from river to river and from season to season, with values as low as 0.64 mg l⁻¹ to greater than >25 mg l⁻¹ with the highest concentrations observed for the rivers draining Tertiary marine sedimentary rocks in the Burica and Azuero peninsulas. DOC yields from Panamanian rivers (2.29–7.97 tons/km²/y) are similar to or slightly lower than those determined for other tropical SMR systems. Areas underlain by Tertiary aged sediments exhibited significantly higher mean DOC yields compared to their igneous counterparts, despite maintaining substantially lower aboveground carbon densities, suggesting the important influence of lithology. Finally, regression analyses between DOC yields and select watershed parameters revealed a negative and statistically significant relationship with maximum and mean gradient suggesting lower soil retention times may be linked to lower DOC yields.     

Temporal and spatial variability of dissolved organic carbon concentration in the Xijiang River, South China

A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological...     

The contribution of agricultural and urban activities to inorganic carbon fluxes within temperate watersheds

The lateral transport of bicarbonate as dissolved inorganic carbon (DIC) to the oceans is an integral component of the global carbon budget and can represent the sequestration of CO₂ from the atmosphere. Recently studies have implicated land use change, in particular agricultural development, as an accelerator of bicarbonate export. However, due to the co-variation of land use, bedrock and surficial geologies, and the relationship between bicarbonate export and climate, the impact of anthropogenic activities on DIC export remains an important research question. In order to examine the land use controls on DIC export from small temperate watersheds we sampled 19 streams draining catchments of varying land uses with similar bedrock and surficial geologies. In addition to an agricultural effect, there was a strong correlation between the percent of watershed in urban development and DIC concentrations and DIC yields. Urban watersheds exported 7.8 times more DIC than their nearby forested counterparts and 2.0 times more DIC than nearby agricultural catchments. Isotopic data suggest that excess DIC export from altered systems results from increased chemical weathering, enhanced CO₂ production within urban green spaces, and as a result of organic matter loading from septic systems and leaky sewer lines. Furthermore, we found that nitrogen additions (e.g. fertilizers and manure) are aiding in the dissolution of lime, increasing the total export of DIC from agricultural watersheds. Calculated anthropogenic loading rates ranged from 0.43 to 0.86 mol C m^− 2 yr^− 1. These loading rates suggest that a significant portion of global DIC export might be attributable to human activities, although the impacts on CO₂ sequestration are difficult to determine.     

Historical variations in the stable isotope composition of mercury in a sediment core from a riverine lake: Effects of dams,pulp and paper mill wastes,and mercury from a chlor-alkali plant

The Wabigoon River (Ontario, Canada) was affected by dams starting in 1898 and was polluted with pulp and paper mill wastes starting in 1913 and mercury from a chlor-alkali plant from 1962 to 1975. A dated sediment core from a riverine lake was analysed to investigate resultant changes in the biogeochemistry of mercury as revealed by variations in mercury isotope ratios and sediment chemistry. A total mercury maximum formed by the mercury pollution coincided with minimums in the δ-values of the ¹⁹⁸Hg/²⁰²Hg, ¹⁹⁹Hg/²⁰²Hg, ²⁰⁰Hg/²⁰²Hg, and ²⁰¹Hg/²⁰²Hg ratios, and the δ-values decreased in the order δ²⁰¹Hg > δ²⁰⁰Hg > δ¹⁹⁹Hg > δ¹⁹⁸Hg. Thus, mass-dependent fractionation caused depletion in lighter isotopes, implying evaporation of Hg(0) and pollution of the atmosphere as well as the river-lake system. Concurrently, mass-independent fractionation caused ¹⁹⁹Hg enrichment, possibly reflecting an independently documented upsurge in methylmercury production, and ²⁰¹Hg depletion, suggesting removal of methylmercury with anomalously high ²⁰¹Hg/¹⁹⁹Hg ratios by aquatic organisms and accumulation of ²⁰¹Hg-depleted inorganic Hg(II) in sediments. The δ²⁰¹Hg/δ¹⁹⁹Hg ratio rose abruptly when mercury pollution began, reflecting the resultant increase in methylmercury production, and remained high but gradually declined as the pollution abated, paralleling trends shown by methylmercury in aquatic organisms. The δ²⁰¹Hg/δ¹⁹⁹Hg ratio of pre-1962 background mercury increased ca. 1898 and ca. 1913–1929, suggesting accelerated methylmercury production due to stimulation of microbial activities by the damming of the river and the input of pulp and paper mill wastes, respectively. Other variations were linked to economic and technological factors that affected pulp and paper manufacture.     

Scales of heterogeneity of water quality in rivers: Insights from high resolution maps based on integrated geospatial, sensor and ROV technologies

While the spatial heterogeneity of many aquatic ecosystems is acknowledged, rivers are often mistakenly described as homogenous and well-mixed. The collection and visualization of attributes like water quality is key to our perception and management of these ecosystems. The assumption of homogeneity can lead to the conclusion that data collection from discrete, discontinuous points in space or time provide a comprehensive estimate of condition. To counter this perception, we combined high-density data collection with spatial interpolation techniques to created two-dimensional maps of water quality. Maps of four riverine transitions and habitats - wetland to urban, river to reservoir, river to estuary and a groundwater intrusion - were constructed from the continuous data. The examples provided show that the most basic water quality parameters - temperature, conductivity, salinity, turbidity, and chlorophyll florescence - are heterogeneous at spatial scales smaller than those captured by common point sampling statistical strategies. The 2-dimensional, interpolation-based maps of the Hillsborough River (Tampa, FL) show significant influences of a variety of geographic features including tributary confluences, submarine groundwater inflow, and riparian interfaces. We conclude that many sampling strategies do not account for the type of patchy heterogeneity observed. The integration of existing in-situ sensors, inexpensive autonomous sampling platforms, and geospatial mapping techniques provides high resolution visualization that can adds a more comprehensive geographic perspective needed for environmental monitoring and assessment programs.     

Adsorbable Organic Halogens (AOX) in Polish Rivers – Levels and Changes

This paper presents results of a study on the concentration of adsorbable organic halogens (AOX) in water samples of the Oder River and its tributaries collected from 1998 to 2002. The Vistula River water for AOX was analysed in the period 2001–2002. The investigated waters of the Vistula near the mouth (Kiezmark) were more contaminated with AOX than the Oder near the mouth (Widuchowa, Krajnik Dolny). In general, AOX levels in the Polish rivers are comparable to the values found in the European rivers, e.g. the Rhine and the Ton. The research has shown that AOX were correlated with pH, total suspended solids, and the riverine flow. No relation between dissolved oxygen and redox potential and AOX was found out. During the flood period AOX, inorganic halogens (TIX), and mineral substances (sulfates) were analysed.     

Aggregation of riverine colloidal iron in estuaries: A new kinetic study using stopped-flow mixing

The kinetics of aggregation of riverine colloidal iron have been examined using a stopped-flow technique which probes the first few seconds of mixing between river and sea water end members. A significant fraction, up to 80%, of the colloidal iron is aggregated during the first 1–2 s of mixing, indicating that the aggregation process is much faster than previously thought. Most of the aggregation induced by seawater results from the divalent cations Mg²⁺ and Ca²⁺, with the overall ionic strength having little influence. At equal concentrations of 27 mM, the rate of aggregation by alkaline earth cations increased with ionic size Mg²⁺ < Ca²⁺ < Sr²⁺ < Ba²⁺. The aggregation rates were indifferent to the anion (Cl⁻ or SO₄²⁻) present. Very high aggregation rates were also induced by the common water treatment coagulant Al₂(SO₄)₃ at concentrations in the range 20–30 µM Al(III), several orders of magnitude lower that those used for the seawater cations. Our results support the view that specific chemical interactions between the cations and the colloid particle surface, rather than simple electrical effects, control the colloid stability.     

沿海地区复合洪水危险性研究进展

沿海地区频繁遭受洪水灾害,往往并非单一灾种驱动,而是多种致灾因子相互影响的综合结果.文中梳理了沿海地区复合洪水的主要驱动机理,归纳了复合洪水危险性研究中统计模型和动力数值模型两类主要研究方法,并分别阐述了近年来主要进展.复合洪水是极端高潮位(包括天文潮位、风暴潮和海浪)、河流洪水和强降水过程的两两组合或者是三者同时发生...