The role of the 13C isotope of the Tree Ring in Recording of Carbon Cycle Change in Atmosphere

Some natural materials such as tree rings, rocks, sediments, ice cores, coral reefs, shell fish and micro fossil record the chemical, physical and biological changes in atmosphere that had taken place in the past. One of these changes which are recorded in tree rings is C-13 isotope. Through the measurement of ratio of 13C compared to 12C (defined as 13C value), it can be known atmospheric CO2 conditions in the past to reflect the present conditions. Present value of 13C in atmospheric CO2 is -7.5 ‰ that had decreased gradually from -6.69 in 1956. Pre-industrial 13C value in atmospheric CO2 is not available. However, the historical records of those are stored in tree rings. Starting from pre-industrial era about 1850 up to 2000, the records of 13C value in some tree rings which are spread in northern hemisphere showed decreasing value ranging from 0.60/00 to 2.30/00. Major factors contributing to variability of these 13C values are pollution effects and climatic effects. Besides those, some effects such as choice of the wood components, inner ring variability and juvenile stage of trees are also correlated to variability of 13C value. Records of 13C value from tree rings defined that atmospheric CO2 from pre-industrial era were between 240 ppm and 310 ppm then this concentration continuously increase to 340 ppm at present. Integrated biospheric carbon flux calculated for 13C records in tree rings using four models from the year of 1850 to 1975 showed an increasing value between 135 Gt and 345 Gt. Keywords : Tree rings, C-13 isotope, atmospheric CO

Subsurface Flow and Surface Water Interactions Quantification in Gunung Kidul Karst Area Using Hydro- Chemical and Stable Isotopes Data Variations

Subsurface flow is one of the available water sources in the Karsts area such as in GunungKidul. The study of the pattern of the variations of stable isotopes content as a function oftime and its interaction with other water sources such as rain waters, groundwater, riverwater will be a very good tool to assess the potential of the subsurface flow as a water source.For this purpose, the variations of stable isotopes content of subsurface flow around GunungKidul Karsts area and its interactions with other local water sources have been studied for thelast two years. From the comparison of stable isotopes variations pattern of the subsurfaceflow with monthly rain water, the interaction of the subsurface flow with other water sourcesin the area has been quantified. Based on hydro-chemical data, it was found that the rechargearea of subsurface flow were relatively further than other samples and it was also found thatSeropan and Bribin subsurface flow systems originate from different geologic structures.Based on stable isotopes relative contents, it was found Ngobaran and Baron Caves have beenmixed with domestic sewerage water or other surface water.Keywords : Karsts area, stable isotopes, subsurface flo

Penentuan Umur Sedimen Das Cinangka dan Das Cirengit Dengan Geokronologi PB-210

PENENTUAN UMUR SEDIMEN DAS CINANGKA DAN DAS CIRENGIT DENGAN GEOKRONOLOGI PB-210. Pb-210 adalah radioisotop yang biasa digunakan untuk menentukan umur sedimen berdasarkan cacahan sinar alpa. Dengan demikian, geokronologi endapan sedimen yang terjadi di masa lalu dengan skala waktu 150 tahun dapat ditelusuri dengan menggunakan isotop Pb-210. Kehadiran isotop Pb-210 di atmosfer dihasilkan secara alami dari peluruhan radioaktif Rn-222 yang dilepaskan dari bumi. Aplikasi Pb-210 untuk penanggalan sedimen telah dilakukan di muara DAS Cinangka dan Cirengit di Dam Darma – Kabupaten Kuningan. Pengumpulan sampel sedimen dilakukan dengan menggunakan metode coring sedangkan cacahan sinar alpa diukur dengan spektrometer alpa. Hasil penelitian menunjukkan bahwa umur lapisan sedimen dasar yang dikumpulkan pada kedalaman 22-24 cm dari permukaan di DAS Cinangka sekitar 103,34 tahun sedangkan lapisan sedimen dasar yang dikumpulkan pada kedalaman 22-24 cm di DAS Cirengit adalah 103,51 tahun. Oleh karena itu, diperkirakan bahwa  endapan sedimen di DAS Cinangka dan Cirengit terjadi pada tahun 1919 dan 1905

INTERPRETATION OF OXYGEN –18 ISOTOPE IN SULPHATE FROM DEEP GROUNDWATER IN JAKARTA AREA

It has been done a determination of d 18O (SO42-) and d 18O (H2O) value from Jakarta deep groundwater with depth 40-140 m. The aim of this research is to know some procesess influencing the composition of oxygen isotope in groundwater sulphate. A method commonly used to determine d 18O (H2O) value is according to Epstein-Mayeda. CO2 gas resulted from   equilibration process between water sample and CO2 gas standard in which oxygen isotopic reaction has occurred, is injected to mass spectrometer. For determination of d 18O (SO42-) value, Rafter method is used. CO2 gas released from reducing sulphate of water sample with graphite is injected to mass spectrometer. The results of d 18O (H2O) values obtained in this experiment have a narrow range from  -5,04 0/00 to  -6,65 0/00 SMOW whereas their d18O (SO42-) values have a wider range from +8,3 0/00 to +17,4 0/00 SMOW.  The more constant values of d 18O (H2O) performed that evaporation effects might not occur.  Based on the similarity between d18O (SO42-) values of deep groundwater and that of marine evaporite sulphate rocks, it is supposed that sulphate of Jakarta deep groundwater was derived from dissolution of this rocks. There was an indication of seawater intrusion around Pejagalan and Kamal Muara Penjaringan area based on the similarity between their d18O (SO42-) values and d18O (SO42-) of modern seawater.  The contribution of oxygen from water in sulphide oxidation reaction ranged 0% to 12% suggesting that oxygen in deep groundwater sulphate was mainly derived from atmospheric molecular oxygen   Keywords: oxygen isotope, sulphate, groundwate

Study of Susceptibility of Pari Island Groundwater – To Surface Water Using Natural Isotopes and Hydrochemicals

The Pari Island with a total area of 40,32 ha is situated at the southern end of a chain of more than a hundred islands, commonly known as Seribu Islands, in Java Sea.  Its topography is flat land and mainly consists of coral reefs such that fresh water supply for local people is very limited. The scarcity of fresh water to the local people  is still worsen by the intrusion of sea water to the aquifer system. The objective of this study is to get a better understanding of mixing process between sea water and ground water and to trace the sources of salinity in shallow groundwater of Pari Island. The combinations of natural isotopes of 18O and 2H in water and hydrochemical (such as Na+, K+, Ca2+, Mg2+, Cl-, SO42- and HCO3-) content were used in this study. Results of hydrochemicals showed that almost all of the shallow groundwaters of Pari island had undergone mixing process with sea water. Mostly, they were classified as brackish water and gradually changed to saline water along the flowpath of the water. Only two groundwater samples were still characterized as fresh water type. Mixing ratios of seawater-groundwater water were estimated to be between 2% and 38%. Isotopic results of 18O and 2H revealed that slope of groundwater samples had decreased compared to local water meteoric line. Obviously, those distributions a long the mixing line of sea water – rain water, indicated that high salinity of groundwaters in Pari Island  originated from encroachment of sea water. It implied that the salinity was caused by flushing of minerals into soil by direct precipitation could not be taken into consideration. Key words: Pari Island, groundwater, sea water intrusion, natural isotopes, hydrochemical

Karakteristik Air Tanah Dangkal Kota Semarang Pada Musim Penghujan Berdasarkan Pendekatan Isotop Stabil (18O, 2H) dan Kimia Air

Pada bulan Maret 2014 telah dilakukan penelitian air tanah di wilayah Kota Semarang dengan tujuan untuk mengetahui karakteristik air tanah dangkal pada saat musim penghujan melalui pendekatan isotop stabil (18O, 2H) dan kimia air yang didukung dengan data hidrogeologi setempat. Sejumlah sampel air tanah dangkal diambil di beberapa lokasi dengan kedalaman antara 0 — 35 m di bawah permukaan tanah setempat (dbpts). Analisis isotop stabil 18O dan 2H serta kimia air dilakukan di laboratorium Hidrologi, Pusat Aplikasi Isotop dan Radiasi, BATAN Jakarta. Hasil analisis isotop stabil 18O dan 2H menunjukkan bahwa sekitar 63 % air tanah cenderung berada di dekat garis meteorik Semarang dan sekitar 37 % sisanya mengalami evaporasi, interaksi dengan oksida batuan dan sedikit pengaruh interaksi atau mixing dengan air laut. Dari hasil analisis kimia air dengan ionic balancesekitar 3 % menunjukkan bahwa pada saat musim penghujan akuifer air tanah dangkal di wilayah Kota Semarang didominasi oleh ion bikarbonat (HCO3-) dengan tipe air didominasi CaHCO3. Sedangkan dari data parameter Chloride Bicarbonate Ratio, sekitar 24 % air tanah dangkal di wilayah Kota Semarang terindikasi mengalami intrusi air laut dansisanya sekitar 76 % masih menunjukkan karakteristik sebagai air tanah tawar.Kata kunci : karakteristik air tanah, air tanah dangkal, Semarang, musim penghujan, isotopstabil dan kimia ai

INVESTIGATION OF STABLE ISOTOPE OF ¹⁸O AND ²H IN SHALLOW GROUNDWATER FROM KARAWANG AREA

Karawang area is well known as an agriculture area and 2% area is utilized for industries. Clean water demands increase due to developing industry development and population increasement. The origin of groundwater is necessary to keep the sustainability of water resources in this area. Stable isotopes such as 18O and 2H can be used as a parameter to trace the ground water origin. The methods used were Epstein-Mayeda and Zinc reduction for analysis 18O and 2H, respectively. Sampling period was conducted in major dry season in year 2002. The result showed that evaporation effect had influenced to the content of both isotopes in its shallow groundwater that caused a slope shift from its local meteoric line. The origin of its shallow groundwater was from rainwater infiltrating directly in less than 10 m altitude. Citarum River showed more depleted values in both isotopes compared to shallow groundwater and it indicated that its water might originate from spring at the altitude of 600 m.     Keywords: oxygene-18, deuterium, groundwater, isotop

INVESTIGATION OF DISSOLVED SULPHATE IN VARIOUS GEOTHERMAL FIELDS OF SUMATRA USING OXYGEN AND SULPHUR ISOTOPES

There are at least 30 high temperature systems; eleven active volcanoes, five degassing volcanoes and one caldera volcano controlled by Sumatra Fault Zone over a length of 1700 km. To understand this geothermal field system, some information about geochemistry including isotope composition in its fluid is needed. Sulphur-34 and oxygen-18 isotopes in dissolved sulphate pair have been used to determine the origin of acidic fluid of sulphate and to evaluate the process involved. The fluids from eight hot springs, two fumaroles, four deep wells and crater have been collected in along Sumatra geothermal fields. Sulphur-34 (d 34S (SO4), 0/00 CDT) and oxygen-18 (d 18O (SO4), 0/00 SMOW) in sulphate is analyzed according to Robinson-Kusakabe and Rafter method, respectively. The d 34S (SO4) values from Sibayak wells are more enriched of 16.8 0/00 to 18.2 0/0 that may indicate the dissolution of anhydrite minerals or isotope partitioning in hydration of SO2. The d 34S (SO4) values from two fumaroles (Pusuk Bukit - North Sumatra and Rantau Dadap - South Sumatra) are at depleted value of -0.150/00 and 1.80/00, those are close to d 34S from magmatic sulphur.  In general, the d 34S (SO4) of springs spread in a wide range of 5.250/00 to14.20/00 and show a mixing process between atmospheric sulphate and sulphate from deep wells. The d 18O (SO4) from wells exhibits depleted value around -3.60/00 suggesting that 87.5% of sulphate oxygen is derived from groundwater oxygen and 12.5% is derived from atmospheric molecular oxygen in sulphide oxidation reaction. In the other hand, hot springs (except Semurup), crater and fumaroles have enriched value of d 18O (SO4). These enriched values suggest that a higher percentage of atmospherically derived oxygen compared to those from the depth.   Keywords: isotope, geothermal, Sumatr