Constant Rate Of Supply Model Research Articles

Application of Constant Rate of Supply Model for the Determination of Sediment Accumulation Rates and Chronology of Bukit Merah Reservoir Perak, Malaysia

The Constant Rate of Supply (CRS) model is used to measure the continuous influx of unsupported 210Pb into the sediment, allowing for the assessment of changes in the rate of sediment accumulation due to anthropogenic impacts over time. Thus, the CRS model was used to analyze a 25 cm bottom sediment core extracted from Bukit Merah Reservoir. Results revealed a high sedimentation rate in the reservoir, which ranged from 0.14 to 0.37 gcm-2 yr-1, with a mean sedimentation rate of 0.31 cm yr-1. The presence of 137Cs was not observed in the core, while the activity of 241Am was detected in two isolated samples but was insufficient for use as a marker. The constant rate of 210Pb supply (CRS) model dated the oldest sediments (22.5-24.5 cm) to AD 1985 ± 34 years of human influences. Overall, the sedimentation rate in the reservoir experienced a rapid increase from the 1980s to the 2000s and fluctuated to the top of the core indicating continuous anthropogenic impacts on the reservoir. The study identified continuous increases in agricultural activities, expansion in the tourism industry, population growth, and changes in land use, as the main cause of heightened sedimentation and sediment particles delivery into the reservoir. Therefore, urgent measures are needed to address the current siltation state of the reservoir.

Use of 210Pb dating models for estimating sedimentation rate of a typical sediment core taken in the Ba Lat coastal area (Red River)

Sediment cores were taken in the coastal area of Ba Lat estuary (Red River), in the Xuan Thuy national park. Each core was cut into slices of 4 cm in thickness, numbered from top to bottom and then analyzing for radionuclides (226Ra, 137Cs and 210Pb). Computational dating models were used to determine the age and sedimentation rate for each sediment core. This report presents the results of applying computational models to the sediment core BL13 that could provide a general methodology for determining the age and the sedimentation rate of the sediment cores taken in the coastal area of Ba Lat estuary. Results show that Constant rate of supply (CRS) model is probably the best model for determining the sedimentation rate. For the sediment core BL13, the use of the Composite model by adjusting the results of the CRS model in combination with the time marker of August 1971 (the time of the historical flood event on the Red River) seems to give the most reasonable results. The average sedimentation rate at the BL13 site before 1960 was about 0.5 cm/year. The rate had increased significantly from 1960, up to the highest value of 1.5 cm year-1 in the 1970s and then decreased to about 1.0 to 1.2 cm/year from the 1980s to the present. The change in the sedimentation rate could be caused by the main flow changes and large floods of the Red River from 1960 to 1980.

Comparison of 14C and 210Pb - 137Cs - 241Am dating methods of a recent bat guano deposit (Lot, SW France)

Bat guano deposits are increasingly used as records of past environmental changes, an approach that requires a precise chronology of the guano layers. This paper presents a comparison between the well-established 14 C dating method and methods based on natural 210 Pb excesses, ( 210 Pb) ex , and artificial radionuclides 137 Cs and 241 Am. The studied example is a bat guano deposit from a cave in SW France (the Brantites III cave), which is currently investigated for paleo-environmental reconstructions using stable isotopes. 14 C data show that the upper part of the guano deposit accumulated during the last 150 years with a marked increase in accumulation rates after around 1960 AD. While the incorporation of atmospheric 14 C in guano is a well-understood process, the origin of 210 Pb excesses is more complex. Based on consideration of 137 Cs and ( 210 Pb) ex inventories recorded in undisturbed soils in France, and the measured inventories in the guano deposit, we suggest that most of the 210 Pb excess is produced by 222 Rn decay in the cave air and then adsorbed onto the guano. As Radon concentrations in caves can vary significantly on both short and long-term timescales, one needs to be cautious before applying the often-used CRS (constant rate of supply of 210 Pb excess) model to guano dating. Our ( 210 Pb) ex data are best interpreted by two successive periods of roughly constant, but widely different accumulation rates (0.3 cm/y and 2.6 cm/y before and after 1960, respectively) and ( 210 Pb) ex fluxes. We suggest that these relatively abrupt variations result from a change in cave ventilation leading to a more favourable shelter for bats after 1960. The upper 40 cm of the deposit shows evidence of 210 Pb mobility, adding a further complexity to the interpretation of ( 210 Pb) ex profiles in guano deposits. However, the existence of well-defined 137 Cs and 241 Am peaks allows a precise identification of the year of maximum atmospheric fallouts (∼1963–1964). When the ages provided by artificial radionuclides are combined with the 210 Pb-derived accumulation rates, an age model can be built, which is in good agreement with the 14 C age model. This example shows that the ( 210 Pb) ex method, when associated with 137 Cs ( 241 Am) data, can be used to date recent guano deposit, although its application is not as straightforward as the 14 C method.

Carbon sequestration potential in montane wetlands of Korea

Montane wetlands are important carbon sinks for mitigating climate change. In this study, we estimated carbon sequestration rates and carbon storage in montane fen wetlands of the Odaesan National Park of Korea. We measured the depth of the organic layer at the three wetlands using a probe and collected 12 cores from four sites with different dominant plant species. The physicochemical characteristics of the cores were analyzed, and the 4 cores were dated with 210 Pb using the constant rate of supply model. Based on physicochemical analyses and 210 Pb dating, the carbon sequestration rate and carbon storage were calculated, ranging from 58.29 to 125.31 g C m −2 y −1 and 14.13–138.00 t C, respectively. Among the four sites studied, the carbon storage was highest at the Phragmites australis and Sphagnum palustre dominant site and the carbon sequestration rate was highest at the Salix koriyanagi and Sphagnum palustre dominant site. The carbon sequestration rate was substantially different before and after 1980 in montane wetlands in Korea ( p < 0.01). The depth of the organic layer and the organic matter density were significantly different among the four sites ( p < 0.01), with Jilmoe-neup showing the lowest value with recorded disturbance. We recommend that the dominant plant species and presence of disturbance be taken into account when estimating carbon sequestration rates and carbon storage for assessment of wetland restoration. The presence of S. palustre is an important factor in increasing carbon sequestration by diminishing carbon emissions. Disturbance is a factor that reduces the carbon sequestration rate and carbon storage, highlighting the importance of wetland conservation. Further studies are needed on the factors controlling carbon sequestration. • Carbon sequestration rate should be assessed based on dominant species. • Organic layer depths may differ among the same type of wetlands. • Organic layer depth is important when calculating the carbon amount per unit area. • Sphagnum palustre is important factor in increasing carbon sequestration by diminishing carbon emissions. • Quantify carbon sequestration potential using short-term carbon sequestration rate.

Geochronology of Recent Sediments from the Upper Bonny Estuary (Niger Delta) Using Naturally Occurring Radionuclides

The research evaluated temporal trends of naturally occurring radionuclides and their vertical distributions in sediment cores collected from three sites of diverse sedimentation regimes in Bonny Estuary, and developed and implemented sediment dating with unsupported lead-210. Radium (Ra) isotopes exhibited a very similar distribution throughout all sampled cores in each month, with 228Ra, while 226Ra displayed some variability with generally lower specific activities in dry months than in wet months. The values found in the study were all less than unity ranging from 0.3 to 0.8, which suggested sediment accretion and that the study area corresponded to zones with different sedimentation regimes. Temporal distribution of total 210Pb in the sampled cores determined via its daughter 210Po by alpha spectrometry assumed that the secular equilibrium between both radionuclides was achieved. However, the activities in Station 3 were found to be lower than those in Station 1, with Station 2 having the lowest activity registered in the samples collected in December month. The specific activities of 228Ac (228Ra), 212Pb (228Th) and 40K against depth in the sampled cores were observed to be almost equal to one another at each stratigraphic interval. The average sedimentation rate throughout the core obtained from Constant Rate of Supply model (0.068 ± 0.015g.cm-2.y-1) was nearly the same as that obtained from the Constant Initial Concentration model (0.065 ± 0.004). However, the estimated ages were quite variable with depths of various stratigraphic layers. The age of the sediment core was dated approximately 80 years, which was qualitatively validated using 137CS whose activity was definitely undetected in the basal part of the core. The sedimentation rates calculated suggested low sedimentation characterized by low energy environment dominated by weak tidal currents.

The off-site implications of deforestation on sedimentation rates and pollution in Abkenar open water (Anzali Lagoon, Caspian Sea) using radionuclide techniques and sediment quality indices

Abkenar open water (AOW) has a 35 km2 distribution and is the largest part of the Anzali Lagoon in the southern coastal zone of the Caspian Sea. The effects of deforestation in the upstream basin of the AOW were assessed by measuring the rate of sedimentation, sediment contamination, and ecological risk for aquatic life and end-users using radioisotopes Cesium-137 and Lead-210. The chronology of the AOW sediment column was studied using the Constant Rate of Supply model. Correlations between environmental changes and the sedimentary regime of the study area highlight the contribution of the AOW authorized international and local wood harvesting companies pre-and-post 1950 in the catchment in terms of the rate of sediment supply and the influx of toxic metals. Historical evidence shows that two specific layers formed during World Wars I and II with the mean rates of 0.185 ± 0.04 (±STD) and 0.32 ± 0.02 kg/(m·y), respectively. The highest influx of alkali elements and toxic metals (nickel, cadmium, lead, zinc, and copper) into the basin occurred in 1945. Two layers of gray mud (16–50 cm) and organic-rich dark loss mud (0–16 cm) correlated well with the programmed wood harvesting projects. These layers accumulated from 1953 to 2000 with a mean rate of 0.6 ± 0.2 and 2 ± 0.7 kg/(m2·y). Thus, aquatic life and end-users have been exposed to moderate to extremely high levels of toxic metals and a moderate level of contamination since the 1950s.

Emerging dominance of Paratrochammina simplissima (Cushman and McCulloch) in the northern Gulf of Mexico following hydrologic and geomorphic changes

Grand Bay estuary in coastal Mississippi and Alabama (USA) has undergone significant geomorphic changes over the last few centuries as a result of anthropogenic (bridge, road, and hardened shoreline construction) and climatic (extreme storm events) processes, which reduce freshwater input, sediment supply, and degrade barrier islands. To investigate how geomorphic changes may have altered the Grand Bay estuary, sediment push cores were collected for foraminiferal, sedimentological (organic matter content, grain-size distribution), and radiochemical (210Pb,137Cs, and 7Be) analyses. Clay normalized geochronologies were determined with a constant rate of supply model. Based on downcore age-depth relationships, select intervals were analyzed for foraminifera in order to assess alterations in the microfossil assemblage in Grand Bay estuary over the 20th Century. All estuarine samples were low diversity (species richness: 1–10; Fisher's alpha diversity: 0.14–1.75); two species, Ammotium salsum and Paratrochammina simplissima, dominated all downcore assemblages. Paratrochammina simplissima increased in abundance up-core from a minor subsidiary species (median = 4.7% at 19–20 cm) to dominant or co-dominant with A. salsum over the 20th and early 21st Centuries in six cores, comprising up to 60.7% of a single sample. The emerging dominance of P. simplissima since ~1950 along with the reduction of brackish-estuarine taxa and introduction of calcareous species signifies increased salinity and less marsh organic matter preserved in the sediments. While seasonal dissolution limits our ability to chronologically constrain the introduction of calcareous species, P. simplissima, a species not referenced in taxonomic data from the northern Gulf of Mexico until 2012, is well constrained, following its first occurrence in the 1930s.

Influence of sedimentation rate on the environmental capacity of total nitrogen in the water of Bohai Bay, China

Measuring environmental capacity of total nitrogen (TN) in marine water has become an effective indicator of how much TN is entering the ocean from various sources. However, the TN environmental capacity balance is affected not only by external input but also by removal of TN from water. This removal occurs by numerous mechanisms, among which sedimentation is one that should not be ignored. The influence of sedimentation rates on the environmental capacity of TN in the water body in the northern area of Bohai Bay was studied by investigating the total nitrogen contents of both water and sediments independently. The radioactivity of lead and cesium isotopes (i.e., 210Pb and 137Cs) that were present in columnar sediment samples was measured for time periods ranging from 48 to 72 h using a high-purity germanium detector. A constant rate of supply model (CRS) was used to calculate sedimentation rates. The results indicate that 5.81 × 106 t of sediment are removed from the water column annually through precipitation. Based on the concentration of TN in the studied sediment samples, we calculate that a total of 3.34 × 103 t of nitrogen are removed from the water via sedimentation every year. According to the target TN concentrations for the marine environment that were adopted for the study area for 2025 and 2030, the amount of TN removed from water by sedimentation could remove 62.08% and 64.85%, respectively, of the TN introduced to the marine environment by allowable amounts of anthropogenic discharge into the northern area of Bohai Bay in 2025 and 2030. The high sedimentation rate in Bohai Bay can be expected to remove half of all nitrogen currently entering the water in this area. This demonstrates that when the environmental capacity of TN in ocean water is used to determine the total amount of nitrogen that can be permissibly discharged from land sources, the capacity of the environment to “self-purify” via sedimentation should be considered.

Implementación de la datación mediante 210Pb - 137Cs en Uruguay para el reconocimiento de la variabilidad climático-ambiental del Holoceno superior. Caso de estudio: Laguna de las Nutrias - Rocha - Uruguay

Geochronology constitutes a fundamental tool for the study of historical events. Its development in Uruguay has been closely linked with archaeological studies. In the last 20 years, dating techniques have expanded into other disciplines, leading to methodological changes and improvements. The most widely used method to study the chronology of most recent Holocene climatic and environmental events is 210Pb-137Cs. The objective of this manuscript is the development in Uruguay of the 210Pb-137Cs geochronological method and its application to a study case. For this, a vertical sediment core was taken from Laguna de las Nutrias (Rocha), which was sub-sampled, and the sections were measured by gamma spectrometry, determining the 210Pb, 226Ra and 137Cs radionuclides. The 210Pb concentration was mathematically modeled, finding that the best fit model is the constant rate of supply model. This model was positively corroborated against the historical profile of 137Cs activity from nuclear events. The annual sedimentation rate was calculated to be 3.1 ± 1.5 mm/year-1 from 1870 to 1986 AD and 4.7 ± 0.8 mm.year-1 after 1986 AD. Likewise, an extreme event possibly associated to the inherent climatic variability of Little Ice Age was inferred.

Assessment and timing of the anthropogenic imprint and fisheries richness in marine sediments from Ría de Muros (NW Iberian Peninsula)

Textural, geochemical and geochronological analyses on two gravity and two box cores recovered from the outer and inner sectors of the Ría de Muros allowed reconstructing and timing the anthropogenic imprint on the sedimentary record from this ría. The chronological framework for the last 8 kyr was built based on Pb-210 dating (Constant Rate of Supply model) and C-14 dating. Recent sedimentation rates were an order of magnitude higher than those of the oldest analyzed sediments, and the periods of upwelling enhancement were constrained.Assessing the human influence on sediment metal contents required the establishment of local background levels. Since the 16th century the enrichment factors of copper, zinc and lead increased (up to 2.7, 1.5 and 2.1, respectively, at or close to present), and a remarkable increase in the fine-grained particles’ content happened in the outer ría sector, due to deforestation. The anthropogenic signature identified in the sedimentary record is assigned to fishing, harbor activities, mining, salting, and, or canning activities, depending on the considered period, which caused a local demographic increase since the 16th century in the region. Such population growth caused a rise in the marine signature of the organic matter, which likely results from enhanced primary production due to eutrophication caused by increased soil erosion and human and livestock waste inputs. Furthermore, the metal enrichment trend during the 20th century, which was more significant in the inner than in the outer ría sector, follows the different demographic evolution of the villages (related to urban and industrial development).The present study highlights the need for conjunction of varying dating techniques when reconstructing the anthropization trends in coastal environments.

Typical pesticides diffuse loading and degradation pattern differences under the impacts of climate and land-use variations

Riverine sediment can reconstruct the history of organic pollution loads and can provide reliable temporal information for pesticide metabolite dynamics in watershed. Sediment core samples were collected from two riverine sections of a cold watershed base in the presence land use change under agricultural development, and the vertical concentrations of four pesticides (atrazine, prometryn, isoprothiolane, and oxadiazon) and two atrazine metabolites (deisopropyl-atrazine and deethyl-atrazine) were determined by gas chromatography–mass spectrometry. The presence of pesticides and metabolites was detected at different depths (11–17 cm) at 1-cm intervals along the two sediment cores, and the flux was calculated with a constant rate of supply model based on the observed concentrations and 210Pb isotope radioactivity chronology. By comparing the concentrations and fluxes of pesticides between the two sediment sections, significant differences in accumulation under different land-use patterns were found. Redundancy analysis further indicated that temporal watershed farmland variance was the dominant factor for pesticide loading. The lower concentration of atrazine and the higher concentration of the other pesticides in the estuarine sediment was closely related to the decreasing upland in the upstream area and the increase in paddy fields in the downstream area. The analysis of atrazine and the metabolites indicated that atrazine is more likely degraded to deethyl-atrazine and the metabolites have similar migration processes in the sediments, which can easily migrate downward. Moreover, the ratio of metabolites to atrazine showed that atrazine degradation was intensive during the transport process, but the metabolites efficiency was lower in this area due to the cold temperature. The results provide insights for the management of pesticide pollution control in watersheds and the potential effects of low temperature on the degradation of pesticides.

Watershed diffuse pollution dynamics and response to land development assessment with riverine sediments

Sediment cores can reflect diffuse pollution history due to the accumulation of pollutants over time, therefore, the quantitative relationship between the sedimentation flux of pollutants and diffuse loads can identify the historical change. Sediment cores were collected from two river reaches in a small agricultural watershed (143 km2), and the total nitrogen (TN) and total phosphorus (TP) concentrations were determined. The sediments were dated using 210Pb isotope radioactivity and the TN and TP sedimentation flux was calculated with Constant Rate of Supply (CRS) and Constant Initial Concentration (CIC) models. Watershed loss loads were simulated using the Soil and Water Assessment Tool (SWAT) in the same temporal period. As the similar natural condition in the post-depositional period of sediments, a linear regression model was used to analyze the relationship between TN and TP sedimentation flux and the hindcast model data. The TP sedimentation flux showed a clear positive relationship with its simulated load (R2 = 0.600 and 0.664) using the CRS model, and better reflected long-term diffuse pollution loss dynamics than nitrogen. The impacts of land use change on diffuse pollution loading were identified with the combination of sedimentation flux from different reaches and watershed modeling. During the expansion of paddy land in the lower reach, the difference of TP sedimentation flux between upper and lower reaches narrowed, while gap of TN sedimentation flux increased. Base on the lateral correlations of two sections, the sediment concentration of TP was more reliable for the long term diffuse pollution assessment under land development.

Radiometric dating of recent sediments: On the performance of 210Pb-based CRS chronologies under varying rates of supply

Abstract Radiometric dating was a revolutionary contribution to the study of sedimentary processes. Empirical data from varved sediments show that unsupported 210Pb (210Pbexc) fluxes vary over time while they statistically correlate with sediment accumulation rates (SAR). This contradicts the basic assumption of the Constant Rate of Supply (CRS) model, which is the most widely used technique for recent sediments. This work is aimed at assessing the CRS model-errors by quantifying the effects on chronologies of various patterns of temporal variability of fluxes. Results are discussed through applications with synthetic and real cores for which and independent varve chronology or a set of reference dates are available. Periodic harmonic and random fluctuations in fluxes tend to cancel out positive and negative deviations in CRS ages, but they produce spurious variability in SARs. Persistent changes in fluxes lead to cumulated and unacceptable deviations of the CRS ages, which cannot be satisfactorily compensated by the use of a piecewise CRS model. The raw and piecewise CRS models can still be powerful tools of widespread use when the conditions for their applicability are well understood. The paper shows how the analysis of clusters in the 210Pbexc vs mass depth profile, along with the estimation of equivalent constant fluxes pre and post-dating a known reference date, are powerful methods to prevent misapplications of the CRS model.

Determination of geochronology and sedimentation rates of shallow lakes in the middle Yangtze reaches using 210Pb, 137Cs and spheroidal carbonaceous particles

Accurate chronologies for recent sediments of shallow lakes in the Yangtze floodplain are critical to calibrate proxy records for reconstructing environmental changes during the past century. This study presents the results of detailed 210Pb analysis from eight lake sediment cores collected from the middle Yangtze reaches, southeast China. Unsupported 210Pb activities generally declined exponentially with mass depth in the eight cores. The chronologies and sedimentation rates for the sediment cores were calculated using different 210Pb-based mathematical models. The 137Cs chronomarker (i.e. the 1963 fallout peak) and the spheroidal carbonaceous particle (SCP) chronomarker (i.e. the start of the rapid increase in 1970 CE) were selected to validate the 210Pb dating. Sedimentation rates derived from different models were validated using historical data including lake area, arable land area, sediment discharge and reservoir volume in the Yangtze basin. The SCP-corrected CRS (constant rate of supply) model performs better than other models, based on validation using historical documents in the Yangtze basin. The 137Cs chronomarker might be erroneous due to catchment-driven 137Cs inputs from soil erosion and post-depositional diffusion. Both SCPs and 137Cs are susceptible to inputs from catchment soil erosion, but SCPs show no apparent degradation and post-depositional changes in lake sediments. The SCP profile provides a relatively reliable chronomarker, which can be used for validating 210Pb chronologies in these floodplain lakes. Generally, sedimentation rates in the eight lakes were <0.2 g cm−2 yr−1 before the 1930s, and then increased to a peak in the 1960s. Afterwards, sedimentation rates decreased and remained low after the 1980s.

Reconstructing recent changes in sediment yields from a typical karst watershed in southwest China

Southwest China is characterized by shallow soils with low soil loss tolerance (30–68 t km−2 yr-1), and this region is one of the largest contiguous karst areas in the world, notorious for its highly eroded landscapes. However, reliable information on soil erosion rates in these karst watersheds is limited due to the highly heterogonous landscape. Karst depressions are a unique geomorphologic pattern in southwest China which can trap eroded sediment similar to a reservoir or dam, and may provide a great opportunity for sediment yield estimation if the sediment chronology can be properly determined. This study used karst depression sediment deposits to reconstruct the changes in sediment yields over the past 60 years from a typical karst watershed in southwest China. Three sediment cores were collected from the depression to measure the changes in 137Cs and 210Pbex, clay, silt, and sand contents, and soil organic carbon at different depths. The results indicated that the three common 210Pbex dating models - Constant Sedimentation (CFCS), Constant Initial Concentration (CIC), and Constant Rate of Supply (CRS) - were not applicable to karst depressions, while a modified CRS model that used 137Cs age marker as reference improved determination of the sediment chronology. From 1949 to 2015, the sediment yields initially increased and then sharply decreased to a low value, which might represent a general trend of soil erosion dynamics in karst watershed of southwest China. It was noteworthy that the mean soil erosion rate after the “Grain for Green” project of 1999 was only 80 t km−2 yr-1, which also is greater than the soil loss tolerance in karst regions. This study demonstrates the potential for use of 137Cs and 210Pbex to evaluate the temporal variation in sediment yield in a typical karst watershed of southwest China and may improve karst watershed management.

Recent Changes in Sedimentation Rate in Three Lakes of Ishikari Wetland, Northern Japan Determined by 210Pb Dating

Historical changes in lake sedimentation for the last 150 years and the lifetime of lakes of Ishikari Wetland are reconstructed in this study. The floodplain wetlands surrounding the lakes have gradually converted to farmlands since the 1890s. 210Pb activity in lake profiles was found to have a non-exponential decrease with depth due to increased and variable sediment flux from agricultural activities. 210Pb dates of these lakes were calculated in this study using constant rate of supply model, which was in good agreement with the date based on 137Cs method. The average total sediment mass in the lakes under natural conditions were 54–112 ton/year until 1890s. It was increased to 111–1055 ton/year after 1890s due to conversion of floodplain to agricultural lands. Especially, lakes after the 1940s had the highest sediment accumulations due to sediment influx resulting from intensification of agriculture via increasing farm size and destroying swamp buffers surrounding the lakes. The time forecasted for filling lakes based on post-1940s sediment accumulation mass was about 15 to 23 years. Restoring swamp buffers surrounding the lakes and converting to low intensity agricultural activities are needed to restrict lake shallowing.

Applying of Modified Constant Rate of Supply Model to Lake Sediments in &lt;sup&gt;210&lt;/sup&gt;Pb Dating and Assessment of Some Heavy Metals

In present study, Lead-210 (Polonium-210) activity concentrations were indirectly obtained by utilizing alpha spectrometry. Sediment chronology was determined by using modified CRS model. Average sediment accumulation rates are 0.351, 0.324, 0.222 g cm -2 y -1 in S-1, S-2, S-3 stations respectively. With reference to atmospheric 210 Pb flux (29 mBq cm -2 y -1 ) Lake Karagol has extra outer 210 Pb input (soil erosion) from the catchment area. In terms of Enrichment Factor (EF), heavy metal concentrations are lower than the anthropogenic values. So it can be said that the elements except Au originate from the continental supply. Au has unexpectedly too high level EF value (58.22) in northern station (S-1) of the Lake Karagol. It corresponds to time interval from 2004 to nowadays. However Pollution Load Index (PLI) says different consequences from the EF values. PLI value has only baseline levels of pollutants in northern part of the Lake Karagol as it shows progressive deterioration of the site for southern part of the Lake Karagol.

Characteristics of Sediments Deposition in Karimata Strait

Karimata strait connects South China Sea and Indonesia territorial seas where the strait current pattern is affected by west and east monsoon. This condition influences particles depositing sedimentation process in the strait. Lack information about sediment depositing rate at the straits dozens years ago makes this research is important to be conducted. This research was to estimate sediment depositing rate in the strait in two areas, near shore and off shore of Borneo. The research was conducted on June to September 2015 used coring sediment samples. Those samples were derived from Baruna Jaya VIII Ship Cruise on June 2015 that was collaborative research between Ministry of Marine and Fisheries Affairs of Indonesia and National Nuclear Center of Indonesia (BATAN).Samples were analyzed in the laboratory of Chemical and Ocean, Department of Environmental and Natural Resources, Center of Radiation and Isotope, National Nuclear Center of Indonesia (BATAN). Estimation of sediment depositing rate used natural isotope 210Pb. The study shows that the depositing rate of the nearest to Borneo area is about 0.92 kg.m-2.y-1 (1965) and increases to be 3.31 kg.m-2.y-1 (2009). The other area is about 0.08 kg.m-2.y-1 (1840) and increases to be 1.78 kg.m-2.y-1 (2010). This result implies that the sediment depositing rate at the nearest area to Borneo is higher than the off shore. Keywords: Near shore, off shore, Natural Isotop 210Pb, CRS (Constant Rate of Supply) model

Using river sediments to analyze the driving force difference for non-point source pollution dynamics between two scales of watersheds

The formation and transportation processes of non-point source (NPS) pollution varied among the studied watersheds in the Northeastern China, so we hypothesized that the driving force behind NPS pollution followed the spatial scale effect. With a watershed outlet sedimentary flux analysis and a distributed NPS pollution loading model, we investigated the temporal dynamics of NPS and the differences in driving forces. Sediment core samples were collected from two adjacent watersheds, the smaller Abujiao watershed and the larger Naoli watershed. The natural climatic conditions, long-term variations in the distribution of land use, soil properties and tillage practices were the same in the two watersheds. The vertical distributions of total nitrogen, total phosphorus, Zn and As at 1-cm intervals in the section showed clear differences between the watersheds. There were higher concentrations of total nitrogen and total phosphorus in the larger watershed, but the heavy metals were more concentrated in the smaller watershed. Lead-210 (210Pb) analyses and the constant rate of supply model provided a dated sedimentary flux, which was correlated with the corresponding yearly loading of NPS total nitrogen and total phosphorus in the two watersheds. The total phosphorus showed a stable relationship in both watersheds with an R2 value that ranged from 0.503 to 0.682. A rose figure comparison also demonstrated that the pollutant flux in the sediment was very different in the two watersheds, which had similar territorial conditions and different hydrological patterns. Redundancy analysis further indicated that expanding paddy areas had a large impact on the sedimentary flux of nitrogen and phosphorus in the smaller watershed, but precipitation had a direct impact on NPS loading in the larger watershed. We concluded that the spatial scale effect affected the NPS pollution via the transport processes in the waterway, which was mainly influenced by branch length and drainage density.

Determination of sedimentation rates in Izmir Bay using 210Pb radionuclide

In this study, using the constant rate of supply model, sedimentation rates of Izmir Bay were calculated and discussed. For this purpose, eight sediment cores were collected from inner part of the bay and sedimentation rates were calculated from vertical distribution of 210Pb. 210Pb activities were determined indirectly from 210Po activities. Sedimentation rates ranged from 0.10 to 0.52 cm/year. The highest sedimentation rates were determined in stations close to the Poligon stream. It was concluded that main transporting mechanism for sediments is river and streams in the area. In addition, sediment cores taken from the harbor were mixed due to bioturbation, water circulation and/or other factors.