Cindy Rianti Priadi

Spatio-temporal variability of solid, total dissolved and labile metal: passive vs. discrete sampling evaluation in river metal monitoring

In order to obtain representative dissolved and solid samples from the aquatic environment, a spectrum of sampling methods are available, each one with different advantages and drawbacks. This article evaluates the use of discrete sampling and time-integrated sampling in illustrating medium-term spatial and temporal variation. Discrete concentration index (CI) calculated as the ratio between dissolved and solid metal concentrations in grab samples are compared with time-integrated concentration index (CI) calculated from suspended particulate matter (SPM) collected in sediment traps and labile metals measured by the diffusive gel in thin films (DGT) method, collected once a month during one year at the Seine River, upstream and downstream of the Greater Paris Region. Discrete CI at Bougival was found to be significantly higher than at Triel for Co, Cu, Mn, Ni and Zn, while discrete metal partitioning at Marnay was found to be similar to Bougival and Triel. However, when using time-integrated CI, not only was Bougival CI significantly higher than Triel CI, CI at Marnay was also found to be significantly higher than CI at Triel which was not observed for discrete CI values. Since values are time-averaged, dramatic fluctuations were smoothed out and significant medium-term trends were enhanced. As a result, time-integrated concentration index (CI) was able to better illustrate urbanization impact between sites when compared to discrete CI. The impact of significant seasonal phenomenon such as winter flood, low flow and redox cycles was also, to a certain extent, visible in time-integrated CI values at the upstream site. The use of time-integrated concentration index may be useful for medium- to long-term metal studies in the aquatic environment.

X-ray absorption fine structure evidence for amorphous zinc sulfide as a major zinc species in suspended matter from the Seine River downstream of Paris, Ile-de-France, France.

Zinc is one of the most widespread trace metals (TMs) in Earth surface environments and is the most concentrated TM in the downstream section of the Seine River (France) due to significant anthropogenic input from the Paris conurbation. In order to better identify the sources and cycling processes of Zn in this River basin, we investigated seasonal and spatial variations of Zn speciation in suspended particulate matter (SPM) in the oxic water column of the Seine River from upstream to downstream of Paris using synchrotron-based extend X-ray absorption fine structure (EXAFS) spectroscopy at the Zn K-edge. First-neighbor contributions to the EXAFS were analyzed in SPM samples, dried and stored under a dry nitrogen atmosphere or under an ambient oxygenated atmosphere. We found a sulfur first coordination environment around Zn (in the form of amorphous zinc sulfide) in the raw SPM samples stored under dry nitrogen vs an oxygen first coordination environment around Zn in the samples stored in an oxygenated atmosphere. These findings are supported by scanning electron microscopy and energy dispersive X-ray spectrometry observations. Linear combination fitting of the EXAFS data for SPM samples, using a large set of EXAFS spectra of Zn model compounds, indicates dramatic changes in the Zn speciation from upstream to downstream of Paris, with amorphous ZnS particles becoming dominant dowstream. In contrast, Zn species associated with calcite (either adsorbed or incorporated in the structure) are dominant upstream. Other Zn species representing about half of the Zn pool in the SPM consist of Zn-sorbed on iron oxyhydroxides (ferrihydrite and goethite) and, to a lesser extent, Zn-Al layered double hydroxides, Zn incorporated in dioctahedral layers of clay minerals and Zn sorbed to amorphous silica. Our results highlight the importance of preserving the oxidation state in TM speciation studies when sampling suspended matter, even in an oxic water column.

Urbanization impact on metals mobility in riverine suspended sediment: Role of metal oxides

Spatial and temporal fractionation of trace metals and major elements in suspended particulate matter in the Seine River was investigated to study the impact of the increasing urbanization in the Greater Paris Region. Suspended sediments in the Seine River were collected between December 2008 to August 2009 upstream and downstream of Paris. They were subjected to total digestion and sequential extraction procedure certified by the Bureau Communautaire de Référence and trace metals along with major elements were analyzed with inductively coupled plasma mass spectroscopy. Metal enrichment factors increased up to eight folds after the Seine River downstream of the Greater Paris Region showing a significant contribution of urbanization. Enrichment of copper, lead and zinc downstream of Paris are followed by the increase of their reducible fraction of at least 10% implicating an increase in metals associated with iron oxides. The exchangeable fraction, which includes the carbonate-associated metals, is only significant for cadmium, nickel and zinc (more than 2 %) while the oxidisable fraction accounts for less than 20 % for the anthropogenic metals downstream except for copper. The metals can be divided to (a) “reducible” group including cadmium, lead, and zinc, associated with more than 60 % of the total Bureau Communautaire de Référence extractable metals to the reducible fraction containing mostly iron oxide phases for the downstream sites. (b) A “distributed” group including chromium, copper, and nickel that are associated to at least 3 different phase-groups: (1) oxides, (2) organic matter and sulphides and (3) mineral phases.

Bioavailability of particulate metal to zebra mussels: Biodynamic modelling shows that assimilation efficiencies are site-specific

This study investigates the ability of the biodynamic model to predict the trophic bioaccumulation of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and zinc (Zn) in a freshwater bivalve. Zebra mussels were transplanted to three sites along the Seine River (France) and collected monthly for 11 months. Measurements of the metal body burdens in mussels were compared with the predictions from the biodynamic model. The exchangeable fraction of metal particles did not account for the bioavailability of particulate metals, since it did not capture the differences between sites. The assimilation efficiency (AE) parameter is necessary to take into account biotic factors influencing particulate metal bioavailability. The biodynamic model, applied with AEs from the literature, overestimated the measured concentrations in zebra mussels, the extent of overestimation being site-specific. Therefore, an original methodology was proposed for in situ AE measurements for each site and metal.

Remanence of lead pollution in an urban river system: a multi-scale temporal and spatial study in the Seine River basin, France

Total lead (Pb) concentration and Pb isotopic ratio (206Pb/207Pb) were determined in 140 samples from the Seine River basin (France), covering a period of time from 1945 to 2011 and including bed sediments (bulk and size fractionated samples), suspended particulate matter (SPM), sediment cores, and combined sewer overflow (CSO) particulate matter to constrain the spatial and temporal variability of the lead sources at the scale of the contaminated Seine River basin. A focus on the Orge River subcatchment, which exhibits a contrasted land-use pattern, allows documenting the relation between hydrodynamics, urbanization, and contamination sources. The study reveals that the Pb contamination due to leaded gasoline that peaked in the 1980s has a very limited impact in the river nowadays. In the upstream Seine River, the isotopic ratio analysis suggests a pervasive contamination which origin (coal combustion and/or gasoline lead) should be clarified. The current SPM contamination trend follows the urbanization/industrialization spatial trend. Downstream of Paris, the lead from historical use originating from the Rio Tinto mine, Spain (206Pb/207Pb = 1.1634 ± 0.0001) is the major Pb source. The analysis of the bed sediments (bulk and grain size fractionated) highlights the diversity of the anthropogenic lead sources in relation with the diversity of the human activities that occurred in this basin over the years. The “urban” source, defined by waste waters including the CSO samples (206Pb/207Pb = 1.157 ± 0.003), results of a thorough mixing of leaded gasoline with “historical” lead over the years. Finally, a contamination mixing scheme related to hydrodynamics is proposed.

Silver and thallium historical trends in the Seine River basin.

Records on pollution by metals of minor economic importance (e.g. silver and thallium) but which prove to be toxic are rarely documented in river sediment. This study used two sediment cores collected downstream of the Seine River to describe the temporal evolution of Ag and Tl concentrations in an urban catchment. Radionuclide analysis (i.e. Cs-137 and Pb-210) allowed dating sediment deposition within the cores (1933-2003). Ag concentration reached maximum values of 14.3-24.6 mg kg(-1) in the 1960s and 1970s, before gradually decreasing up to values which approximated 4 mg kg(-1) in 2003. In contrast, Tl concentrations remained roughly constant throughout the core (median value of 0.86 mg kg(-1)). Suspended solids was collected at upstream locations in the catchment to derive the background concentrations in Ag and Tl. Very high Ag concentrations were measured in the upstream Seine River sites (0.33-0.59 mg kg(-1)), compared to the values reported in the literature (0.055 mg kg(-1)). This suggests the presence of a widespread and ancient Ag pollution in the Seine River basin, as demonstrated by the very high Ag enrichment ratios recorded in the cores. Annual flux of particulate Ag in the Seine River was estimated at 1.7 t yr(-1) in 2003. In contrast, Tl concentrations remained in the same order of magnitude as the natural background signal (0.3-0.5 mg kg(-1)). This study suggests that the Seine River basin is free of Tl contamination. Future concerns should hence mostly rely on Ag contamination, in a context of increasing Ag uses and possible releases to the environment.

Chitosan-praseodymium complex for adsorption of fluoride ions from water

Abstract Engineering of chitosan by praseodymium has been investigated to improve the adsorption properties as well as physical characteristics of chitosan. Modification of chitosan changes the original properties of chitosan so that it can be more suitable for adsorption of fluoride ions. In this study, chitosan-praseodymium (Chi-Pr) was synthesized by impregnation method. The Chi-Pr complex was characterized by scanning electron microscopic-energy dispersive X-ray spectroscopy (SEM-EDX), Fourier transform infrared (FTIR) and employed as an adsorbent for removal of fluorides ions from water in the batch system. The variables such as contact time, concentration of Pr, adsorbent dose, initial concentration of fluoride ions, and competitor anions were studied. The adsorption efficiency of fluoride ions (η) with increasing Pr loading into chitosan (5 wt.%, 10 wt.%, 15 wt.%, 20 wt.% and 25 wt.%) were 35.5%, 56.1%, 72.0%, 68.5% and 62.5%, respectively. The Chi-Pr (15 wt.%) complex had the highest fluoride removal efficiency (72.0%). The experimental data fitted well to the Langmuir isotherm with maximum adsorption capacity (qmax) of 15.87 mg/g and an equilibrium constant (kL) of 0.15 mg. Kinetic study revealed that the adsorption of fluoride ions from water followed pseudo-second-order model with a maximum adsorption capacity (q2) of 8.20 mg/g and a rate constant (k2) of 0.01 g/mg·min. Adsorption efficiency of fluoride ions in the simulated drinking water was diminished with the changes in pH levels. The presence of Pr3+ in chitosan increased chitosans performance as an adsorbent for adsorption of fluoride ions.

The nitrogen cycle in highly urbanized tropical regions and the effect of river–aquifer interactions: The case of Jakarta and the Ciliwung River

Groundwater is extensively used in Jakarta to compensate for the limited public water supply network. Recent observations show a rise in nitrate (NO3(-)) levels in the shallow aquifer, thus pointing at a potential risk for public health. The detected levels are still below national and international regulatory limits for drinking water but a strategy is necessary to contain the growing problem. We combine 3years of available data in the Ciliwung River, the major river flowing through Jakarta, with a distributed river-aquifer interaction model to characterise the impact of urbanisation on the N-cycle of both surface and groundwater systems. Results show that the N-cycle in the river-aquifer system is heterogeneous in space, seasonal dependent (i.e. flow regime) and strongly affected by urban pollution. Results suggest also that although the main sources of N related groundwater pollution are leaking septic tanks, the aquifer interaction with the Ciliwung River may locally have a strong effect on the concentrations. In the general context of pollution control in urban areas, this study demonstrates how advanced process-based models can be efficiently used in combination with field measurements to bring new insights into complex contamination problems. These are essential for more effective and integrated management of water quality in river-aquifer systems.

Occurrence, Sources and Pathways of Antimony and Silver in an Urban Catchment

The recently introduced and increasing uses of silver (Ag) and antimony (Sb) have resulted in an increasing concern on their impacts to the environment. Nevertheless, little information can be found about anthropogenic impacts on the geochemical behaviour of such trace metals in urban river. In the course of our studies dedicated to the Seine River basin, France (67,400 km2), a large set of data was collected. Silver and antimony inputs to the Seine River Basin were estimated using three relevant sources: atmospheric deposition, waste water treatment plants effluents and combined sewer overflows. The Ag and Sb dissolved/solid partition in the river was also estimated on an annual basis. Results showed that Ag output river flux cannot be balanced with the input fluxes, unless to consider another source, which could be the erosion of contaminated soils. In opposite, the Sb budget is well balanced, with atmospheric deposition dominating the input fluxes to the river. The Ag and Sb geochemical behaviors (i.e., their dissolved/solid partition) are highly contrasted, especially for Sb, which dissolved/solid partition is even more fluctuant depending on the emission route.

Methane enrichment on biogas generated from anaerobic digester using coconut shell-based activated carbon

This study evaluates methane enrichment on biogas generated from Anaerobic Digester (AD) through CO2 adsorption process so that biogas can be used as fuel for vehicle engines, power plants, and natural gas substitutes. The experiment was observed by passing biogas synthesis (45% CH4 + 55% CO2) and biogas from cattle manure ±59.7% CH4, ± 37.1% CO2 and ±3.2% other gases) in spontaneously pressurized adsorption column. In addition, observation of CO2 adsorption capacity at various pressure and fixed temperature (27oC) was performed using pure CO2 (±98%). Methane in biogas has been successfully purified to 92% at 0.5 L/min flowrate and 79.6 seconds retention time. The adsorbent will be saturated after gas flowing for 60 and 80 minutes for synthesis biogas and biogas from AD on the amount of adsorbent of 266 grams. A change of surface area of activated carbon (AC) after thermal regeneration at 160oC for 2 hours was 7.51% and regeneration efficiency was 67%. The adsorption process followed Freundlich isothermal. This process can be feasible alternative technology to meet the need for biogas with high levels of methane in small-scale AD.This study evaluates methane enrichment on biogas generated from Anaerobic Digester (AD) through CO 2 adsorption process so that biogas can be used as fuel for vehicle engines, power plants, and natural gas substitutes. The experiment was observed by passing biogas synthesis (45% CH4 + 55% CO 2 ) and biogas from cattle manure ±59.7% CH 4 , ± 37.1% CO 2 and ±3.2% other gases) in spontaneously pressurized adsorption column. In addition, observation of CO 2 adsorption capacity at various pressure and fixed temperature (27°C) was performed using pure CO 2 (±98%). Methane in biogas has been successfully purified to 92% at 0.5 L/min flowrate and 79.6 seconds retention time. The adsorbent will be saturated after gas flowing for 60 and 80 minutes for synthesis biogas and biogas from AD on the amount of adsorbent of 266 grams. A change of surface area of activated carbon (AC) after thermal regeneration at 160°C for 2 hours was 7.51% and regeneration efficiency was 67%. The adsorption process followed Freundlich isothermal. This process can be feasible alternative technology to meet the need for biogas with high levels of methane in small-scale AD.