Recycling of clastics in coastal areas inferred from quantitative analysis of reworked radiocarbon samples

Studies of the evolution of coastal lowlands since the Last Glacial Maximum (LGM) typically ignore radiocarbon data from sediment samples that have undergone reworking. However, these samples contain information on their sediment sources and the timing of their redeposition. We analyzed 738 radiocarbon dates obtained from shell and plant material in samples of post-LGM coastal sediment from north of Tokyo Bay, Japan. Of these samples, 245 (33%) were reworked. Furthermore, the percentage of reworked samples and their average age offsets increased with the depth of the water environment (terrestrial, 15% and 360 ± 250 years, respectively; intertidal, 26% and 470 ± 620 years; subtidal, 39% and 550 ± 630 years). Taking these radiocarbon samples as a proxy for clastic material, our results imply that channel erosion accounted for relatively little clastic removal in the terrestrial and intertidal environments over short timescales, whereas ~ 40% of clastics were removed by storm winnowing and transported in stepwise fashion to deeper water over longer timescales and ~ 60% in the subtidal environment were transported by floods directly from river mouths. These findings imply that radiocarbon ages from reworked samples can be used to quantify clastic recycling processes and their history in coastal areas.

Quality Indeks dan Konsentrasi Logam Berat dalam Perairan dan Sedimen di Perairan Kota Makassar

Kota Makassar merupakan pusat kota di Provinsi Sulawesi Selatan yang memiliki aktifitas wilayah pesisir, seperti pemanfataan industri, pariwisata, transportasi laut serta memiliki dua sungai besar yang muara di perairan. Penelitian ini bertujuan untuk mengetahui konsentrasilogam berat dalam air dan sedimen serta menentukan status mutunya. Pengamatan dilakukan pada 10 lokasi strategis sumber pencemar seperti pabrik, hotel, muara sungai serta pelabuhan dengan mengambil sampel air dan sedimen dan selanjutnya dianalisis di laboratorium untuk logam berat Cd, Cr, Hg, Zn, Cu dan Pb. Statistik deskriptif digunakan untuk menganalisis data yang ada. Metode Indeks Pencemar dan Storet (Storage and Retrieval) digunakan untuk menentukan status mutu air dan sedimen dari logam berat untuk biota laut. Hasil penelitian ini menunjukkan perairan Kota Makassar tergolong dalam kategori “Cemar Ringan” berdasarkan hasil perhitungan indeks Pencemar sedangkan status mutu perairan tergolong “Cemar Berat”. Parameter logam berat di kolom perairan yang melampaui baku mutu adalah Krom (0,016±0,005) dan Tembaga (0,112±0,035). Sedangkan untuk parameter logam berat sedimen secara keseluruhan masih berada dalam ambang batas baku mutu yang telah ditentukan. Kondisi tercemar berasal dari aktifitas reklamasi pantai serta sumber alami dan limbah domestik dari aktifitas masyarakat cukup tinggi.ABSTRACTMakassar City is the city center in South Sulawesi Province which has coastal area activities, such as the use of industry, tourism, sea transportation and has two large rivers that estuary into the waters. This study aims to determine the concentration of heavy metals in water and sediment and determine their quality status. Observations were made at 10 strategic locations of pollutant sources such as factories, hotels, river mouths, and ports by taking water and sediment samples and then analyzed in the laboratory for heavy metals Cd, Cr, Hg, Zn, Cu, and Pb. Descriptive statistics are used to analyze the existing data. The Pollutant Index and Storet (Storage and Retrieval) method is used to determine the status of water and sediment quality of heavy metals for marine biota. The results of this study indicate that the waters of Makassar City are classified as "Lightly Polluted" based on the results of the calculation of the Pollutant index while the status of the water quality is classified as "Heavy Polluted". Parameters of heavy metals in the water column that exceed the quality standard are chromium (0,016±0,005) and copper (0,112±0,035). Meanwhile, the parameters of the sediment heavy metals as a whole are still within the specified quality standard. Polluted conditions derived from coastal reclamation activities as well as natural sources and domestic waste from community activities are quite high.

The Main Features of Phosphorus Transport in World Rivers

Data on the geochemistry of phosphorus in the continental runoff of dissolved and solid substances were systematized and generalized, with a separate consideration of the processes of runoff transformation in river mouth areas. It has been established that atmospheric deposition, which many authors consider to be an important source of phosphorus in river runoff and not associated with mobilization processes in catchments, actually contains phosphorus from soil-plant recycling. This is confirmed by the fact that the input of phosphorus from the atmosphere into catchments exceeds its removal via water runoff. An analysis of the mass ratio of phosphorus in the adsorbed form and in the form of its own minerals was carried out. It was shown that the maximum mass of adsorbed phosphorus is limited by the solubility of its most stable minerals. The minimum concentrations of dissolved mineral and total phosphorus were observed in the rivers of the Arctic and subarctic belts; the maximum concentrations were confined to the most densely populated temperate zone and the zone of dry tropics and subtropics. In the waters of the primary hydrographic network, the phosphorus concentration exhibited direct relationships with the population density in the catchments and the mineralization of the river water and was closely correlated with the nitrogen content. This strongly suggests that economic activity is one of the main factors in the formation of river phosphorus runoff. The generalization of the authors’ and the literature’s data on the behavior of phosphorus at the river–sea mixing zone made it possible to draw a conclusion about the nonconservative distribution of phosphorus, in most cases associated with biological production and destruction processes. The conservative behavior of phosphorus was observed only in heavily polluted river mouths with abnormally high concentrations of this element.

Determination of the length of Bogowonto double jetty as the river mouth stabilization

One of the problems around estuaries with the wave-dominated combination of a small tidal range and low river discharges in the dry season was the mouth closed by a sand barrier. Longshore sediment flows silted up the river mouth while river flows were insufficiently large for flushing sand barriers. When the wet season started, river discharge suddenly enlarged. Discharge can’t flow through the river mouth due to being hindered by the sand barrier. The consequence was that the hinterlands were inundated. Yogyakarta International Airport (YIA) is located in a coastal area of Kulon Progo regency, between two river mouths (Bogowonto river and Serang River). The two rivers have unstable river mouths. The double Jetty had been built at the Bogowonto river, but its condition was damaged. Meanwhile, the breakwater was constructed at the river mouth Serang and called Tanjung Adikarto. Double Jetties will be built to stabilize the Bogowonto river mouth. The purpose of this paper is to provide an overview of the length of the Jetty to be more effective in stabilizing the Bogowonto river mouth. Therefore, so that more easily opened by river flow and does not cause excessive erosion on the one side of the Jetty.

Spatial Distributions and Model Selections of Commercial Estuarine Fish (Sciaenidae) Populations Related to Water Quality, Chl-a, and AML in Musi River mouth, South Sumatra

Estuary and river mouth are essential habitats for many commercial estuarine fishes, including the Sciaenidae family. While recently, estuaries have been threatened by anthropogenic marine litter (AML) transported from nearby land and river. An important type of AML is plastic litter since it takes a long degradation time. In the South Sumatra Province, Indonesia, one of the vital estuaries is the Musi estuary. This paper aims to map the spatial distributions of two Sciaenids, including Panna microdon and Otolithoides pama, and Sciaenid’s environmental covariates, including water quality, chlorophyll a, and plastic litters in Musi estuary and model the correlations of Sciaenids with their covariates. The maps were developed using GIS, and the model was validated using AIC methods. The data were collected from 3 river mouths in the west, central, and east of the Musi estuary. The data showed that the populations of both Sciaenids were higher in the east river mouth rather than in the west. Sciaenid populations were positively correlated with high salinity, DO, chlorophyll a, moderate transparency, and low temperature. A high load of AML’s frequency (7.54 items/m2) and weights (36.8 gram/m2) has reduced both Sciaenid populations in the central river mouth of the estuary. In contrast, low AML loads in the east have correlated with high Sciaenid populations. Model selection based on AIC values shows the best model for P.microdon retained an effect of AML weight with AIC values of 22.591 and 28.321 for O. pama. This concludes that the weight of plastic litter in estuary water was the main limiting factor for Sciaenid populations in Musi.

Floating macro marine debris trends in the Banda Aceh estuary environment

Banda Aceh is a city at the western tip of Indonesia and is one of the provinces that has a coastal area that can contribute plastic waste to the sea. The source of plastic waste comes from land and human activities which are then carried through river mouths to end up in the sea. The purpose of this study was to determine the characteristics of marine debris at the mouth of the Krueng Aceh River. Data collection is determined based on the time of the tide. The research was carried out using a boat mounted with a marine debris trap. The results showed that plastic waste dominated the mouth of the river by 90 percent, both during high and low tide conditions. There is a difference in the amount of waste that accumulates at high and low tide in the Krueng Aceh estuary.