Kemampuan Kerang Hijau (Perna viridis) Mengakumulasi Plutonium Melalui Jalur Air Laut

Operasional fasilitas nuklir yang ada di Serpong memungkinkan melepas radionuklida ke lingkungan. Isotop Pu merupakan radionuklida yang terlepas ke lingkungan. Lepasan tersebut terbawa oleh air sungai atau run off memasuki Teluk Jakarta. Kerang hijau (Perna viridis) mampu mengakumulasi radionuklida tersebut. Studi ini bertujuan untuk memahami kinetika proses bioakumulasi Pu oleh kerang hijau yang dipengaruhi oleh spesiasinya. Percobaan dilakukan melalui tahapan: aklimatisasi, bioakumulasi (242Pu3+ dan 242Pu4+) dan depurasi. Parameter biokinetika diamati meliputi faktor konsentrasi (CF), konstanta laju pengambilan (ku), konstanta laju pelepasan (ke), faktor biokonsentrasi (BCF), dan waktu paruh biologis (tb1/2). Berdasarkan uji statis non parametric menunjukkan spesiasi 242Pu3+ dan 242Pu4+ berpengaruh terhadap kemampuan Perna viridis mengakumulasi Pu. Rerata kemampuan bioakumulasi 242Pu4+ oleh Perna viridis adalah 1,2 kali dibandingkan 242Pu4+. Kata kunci : Bioakumulasi , biokinetika, Perna viridis, plutonium, spesiasi, Perna viridis, plutonium. Operations of nuclear facilities in Serpong have potentially release radionuclides to environment. Pu isotope is one of radionuclide that is released into the environment. The release of this radionuclide was carried by the river water or run off entered the Bay of Jakarta. Green mussels (Perna viridis) can be accumulate this radionuclides. The aims of this study was to understand of the biokinetic of Pu bioaccumulation process by green mussels which are affected by its speciation. The experiment was carried out through stages: acclimatization, bioaccumulation (242Pu3+ and 242Pu4+) and depuration. Biokinetic parameters was observed include concentration factor (CF), uptake rate constant (ku), release rate constant (ke), bioconcentration factor (BCF), and biological half-life (tb1/2). Base on non parametric statistic test shown that speciation of 242Pu3+ and 242Pu4+ had an effect on the ability of Perna viridis to accumulate Pu. Avarage of bioaccumulation capabilities of 242Pu4+ by Perna viridis are 1.2 than 242Pu3+. Keywords: bioaccumulation, biokinetics, plutonium, Perna viridis, speciation.

Kinetics of mercury accumulation by freshwater biofilms

Environmental contextMercury (Hg) is a major environmental contaminant due to its toxicity, accumulation and biomagnification along the food chain. We demonstrate that Hg accumulation by biofilms, one possible entry point for Hg into food webs, is rapid and depends on biofilm structure and composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms. AbstractMercury contamination is of high concern due to its bioaccumulation, toxicity and biomagnification along the food chain. Biofilms can accumulate Hg and contribute to its incorporation in freshwater food webs. Nevertheless, the accumulation kinetics of Hg by biofilms is not well described and understood. The aim of the present study was thus to gain mechanistic understanding of Hg accumulation by biofilms. Kinetics of Hg uptake by biofilms of different ages (e.g. different compositions) was characterised by determining Hg contents in biofilms with and without a cysteine-washing step. Hg accumulation was rapid in both biofilms, with the uptake rate constant of the younger biofilm 10 times higher than that of the older biofilm. Moreover, accumulated Hg reached a plateau at 24h exposure in the younger biofilm, whereas it increased linearly in the older biofilm. The observed difference in Hg uptake by the studied biofilms is likely a result of the difference in biofilm thickness (and thus Hg diffusion inside the biofilm matrix) and microbial composition. These findings have important implications for the understanding of Hg bioavailability and effects towards aquatic microorganisms.

Limited effects of increased CO2 and temperature on metal and radionuclide bioaccumulation in a sessile invertebrate, the oyster Crassostrea gigas

This study investigated the combined effects of reduced pH and increased temperature on the capacities of the Pacific cupped oyster Crassostrea gigas to bioconcentrate radionuclide and metals. Oysters were exposed to dissolved radiotracers (110mAg, 241Am, 109Cd, 57Co, 54Mn, and 65Zn) at three pH (7.5, 7.8, 8.1) and two temperatures (21 and 24°C) under controlled laboratory conditions. Although calcifying organisms are recognized as particularly vulnerable to ocean acidification, the oyster did not accumulate differently the studied metals when exposed under the different pH conditions. However, temperature alone or in combination with pH somewhat altered the bioaccumulation of the studied elements. At pH 7.5, Cd was accumulated with an uptake rate constant twofold higher at 24°C than 21°C. Bioaccumulation of Mn was significantly affected by an interactive effect between seawater pH and temperature, with a decreased uptake rate at pH 7.5 when temperature increased (27 ± 1 vs. 17 ± 1 d−1 at 21 and 24°C, respectively). Retention of Co and Mn tended also to decrease at the same pH with decreasing temperature. Neither pH nor temperature affected strongly the elements distribution between shell and soft tissues. Significant effects of pH were found on the bioaccessibility of Mn, Zn, and 241Am during experimental in vitro simulation of human digestion.

The Kinetic Model of the Uptake and Release of Pollutants by Tubificidae in Sludge Reduction System

Tubificidae is often used in the wastewater treatment systems to minimize the sludge production. A two-compartment kinetic model was applied to simulate the uptake and release of C, N and P-bearing pollutants by Tubificidae in a sludge reduction system. The nonlinear fitting method was used to calculate the uptake rate constantK1and the release rate constantK2for TOC, TN and TP, which were 4.983, 25.764, 10.154 and 3.671, 23.683, 9.023, respectively. The model fitted quite well with the collected data, suggesting that the model was applicable. The results showed that Tubificidae activity would increase the C, N and P concentrations in the system, and the specific release rates of C, N and P-bearing pollutants were 4.31 mg COD/gL. hoffmeisteri· d, 0.722 mg TN/gL. hoffmeisteri· d, and 0.14 mg TP/gL. hoffmeisteri· d,respectively. Ammonia nitrogen contributed up to 70.42% of the released nitrogen.

Biodynamic modelling of the bioaccumulation of arsenic by the polychaete Nereis diversicolor

Environmental context Models that explain the uptake and bioaccumulation of an element in an aquatic ecosystem are valuable for predicting its potential ecotoxicity in coastal areas. Arsenic is a toxic element that is strongly adsorbed to sediments, offering a potential risk to deposit-feeding invertebrates, and ultimately to consumers higher up coastal food chains. This study uses biodynamic modelling to predict the uptake and accumulation of arsenic from water and sediment in a deposit-feeding polychaete worm that is a major source of food to fish and wading birds in estuaries. Abstract Arsenic (AsV) uptake and bioaccumulation from water and ingested sediment by the deposit-feeding polychaete Nereis diversicolor has been investigated using biodynamic modelling. Worms accumulated As from solution linearly at dissolved concentrations from 2 to 20 µg L–1 (uptake rate constant 0.057 l g–1 day–1 at 10°C, 16-psu salinity), and the As assimilation efficiency from ingested sediment was 28.9%. Efflux rate constants of As taken up from water and ingested sediment were 0.0488 and 0.0464 day–1 and did not differ significantly. Sediment As concentrations, ranging from very high to low, were measured at eight estuarine sites, and the model predicted accumulated As concentrations in resident N. diversicolor. Comparisons of predicted against independently measured As concentrations in locally collected worms showed that the model generally performed well, highlighting the potential of biodynamic modelling in predicting the uptake and therefore ecotoxicity of As in estuarine sediments.

Changes of Dopamine Turnover in the Progression of Parkinson's Disease as Measured by Positron Emission Tomography: Their Relation to Disease-Compensatory Mechanisms

An increase in dopamine turnover has been shown to occur early in Parkinson's disease (PD). This study investigated changes of dopamine turnover as a function of PD duration using the effective distribution volume (EDV) for dopamine, determined by positron emission tomography with 6-[18F]-fluoro-L-dopa, and compared them with changes in dopamine synthesis and storage ability, quantified with the fluorodopa uptake rate constant Ki. Six healthy subjects, 9 early PD patients (PD1), and 13 advanced PD patients (PD2) participated in the study. In the caudate, the Ki and EDV for PD1 were not significantly different from the normal values, whereas in the putamen Ki was 63% of normal and EDV was only 35%. Between PD1 and PD2 the decline in EDV was higher than that for Ki (caudate 44% and putamen 46% for EDV vs. 21% and 34%, respectively, for Ki). Turnover was higher in the caudate than the putamen in controls, whereas the PD patients exhibited the reverse pattern. This comparison of changes in Ki and EDV as a function of disease progression indicates that a relatively slower decrease in dopamine synthesis and a relatively faster increase in turnover in early disease likely act as compensatory mechanisms, and that the clinical onset of PD reflects a global failure of dopaminergic compensatory mechanisms.

Effect of Dopamine Loss and the Metabolite 3-O-Methyl-[18F]Fluoro-dopa on the Relation between the 18F-Fluorodopa Tissue Input Uptake Rate Constant Kocc and the [18F]Fluorodopa Plasma Input Uptake Rate Constant Ki

Parkinson disease is characterized by the loss of dopaminergic neurons, thus decreasing the system's ability to produce and store dopamine (DA). Such ability is often investigated using 18F-fluorodopa (FD) positron emission tomography. A commonly used model to investigate the DA synthesis and storage rate is the modified Patlak graphical approach. This approach allows for both plasma and tissue input functions, yielding the respective uptake rate constants Ki and Kocc. This method requires the presence of an irreversible compartment and the absence of any nontrapped tracer metabolite. In the case of Kocc, this last assumption is violated by the presence of the FD metabolite 3- O-methyl-[18F]fluoro-dopa (3OMFD), which makes the Kocc evaluation susceptible to a downward bias. It was found that both Ki and Kocc are influenced by DA loss and thus are not pure measures of DA synthesis and storage. In the case of Kocc, the presence of 3OMFD exacerbates the effect of DA egress, thus introducing a disease-dependent bias in the Kocc determination. These findings imply that Ki and Kocc provide different assessments of disease severity and that, as disease progresses, Ki and especially Kocc become more related to DA storage capacity and less to the DA synthesis rate.

A Reversible Tracer Analysis Approach to the Study of Effective Dopamine Turnover

Changes in dopamine turnover resulting from disease states such as Parkinson's disease may be reflected in corresponding changes in the kinetics of the positron emission tomographic tracer [18F]fluorodopa. The authors had previously refined the conventional irreversible-tracer graphical approach to determine both the uptake rate constant Ki and the rate constant kloss that describes the slow loss of the trapped kinetic component. Because these parameters change in the opposite sense with disease, their ratios may be more powerfully discriminating than either one alone. The ratio kloss/Ki is indicative of effective dopamine turnover. Its inverse, Ki/kloss, can be interpreted as the effective distribution volume (EDV) of the specific uptake compartment referred to the fluorodopa concentration in plasma. Here the authors present a new approach to the estimation of EDV based on reversible-tracer graphical methods. When implemented with a plasma input function, the method evaluates EDV directly. When implemented with a tissue input function, the outcome is proportional to the ratio of the distribution volumes of the specific uptake and precursor compartments. Comparison of the new and previous approaches strongly validates this alternative approach to the study of effective dopamine turnover.