Judul: Pemanfaatan Fe3+ dalam meningkatkan kelarutan Cu pada tanah gambut dari Kalimantan Tengah
Abstrak: Pemanfaatan tanah gambut di Indonesia untuk pertanian dihadapkan pada kendala produktivitas tanah yang tergolong rendah. Di antara penyebab rendahnya produktivitas tanah gambut adalah rendahnya kadar unsur-unsur hara, termasuk hara Cu. Fenomena ini diantaranya disebabkan oleh tingginya kandungan asam-asam organik, khusunya asam-asam fenolat yang memebentuk komplek kelat. Penelitian ini bertujuan untuk mempelajari pengaruh pemberian Fe3+ terhadap kelarutan Cu pada tanah gambut.
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Judul: Peningkatan pelarutan Cu pada tanah gambut pedalaman dari Berengbengkel, Kalimantan Tengah dengan penambahan Fe (III)
Abstrak: Tingkat kemasaman, toksisitas, dan ketersediaan unsur hara yang rendah terutama Cu merupakan masalah utama pada tanah gambut. Bahan koloid tanah gambut yang terdiri dari asam organik terutama asam fenolat memberi pengaruh negatif bagi pertumbuhan tanaman dan ketersediaan unsur hara. Asam-asam fenolat yang dominan dijumpai dalam tanah gambut adalah asam hidroksibenzoat (AHB), asam vanilat (AVN), asam siringat (ASR), asam kurnarat (AKM), dan asam ferulat (AFR). Adanya daya erapan asam-asam organik tersebut terhadap kation-kation menyebabkan ketersediaan unsur hara pada tanah gambut menjadi rendah. Pemberian kation Fe³+ diharapkan dapat rneningkatkan kelarutan Cu dan mengendalikan toksisitas asam fenolat. Bahan penelitian ini berasal dari Berengbengkel, Kalimantan Tengah dengan tingkat kematangan saprik, hemik, dan fibrik. Perlakuan Fe(Ill) diberikan dengan dosis 0 % (Fo), 2.5 % (Fi) dan 5 % (F2) erapan maksimum dan perlakuan Cu(II) diberikan dengan dosis 0 ppm (Co) dan 200 ppm (C1). Penetapan fraksi-fraksi Fe dan Cu tanah gambut dilaksanakan dengan prosedur ekstraksi bertahap yang telah dimodifikasikan. Asam fenolat dan pH diukur untuk melihat kondisi kemasaman dan toksisitas gambut akibat pemberian Fe dan Cu.
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Judul: Thermal Characteristics and Dynamics of Tropical Cyclone over Western North Pacific Ocean: A Case Study of Typhoon Songda (Chedeng) 2011
Abstrak: The frequent occasion of Tropical Cyclone (TC) over Western North Pacific (WNP) Ocean lies from 10˚N to 26˚N and 121˚E to 170˚E. Sources of TC development come from warm ocean temperature where latent heat is released during condensation processes and subsequently concentrated in the boundary layer. Relative humidity at 850-700 hPa is responsible to produce the most intense storm. Meanwhile, weak vertical wind shear between 850-200 hPa is one of the dynamical factors that lead to the development of TC. Pressure level of 850-200 hPa is chosen to minimize the thermodynamic effect in the lower troposphere. Typhoon Songda (Chedeng in the Philippines) or TSC lasted from May 18th to 30th, 2011 and strengthened into powerful Super Typhoon stage between May 24th and 27th. Long curving track and the exhibition of all sequences of TC life cycle, TSC is then considered as an ideal case of TC. The objective of the study with case of TSC is to investigate the role of thermal characteristics and dynamics on TC intensity. The research is carried out by using Advanced Research of Weather Research and Forecasting model (WRF ARW model) version 3.3. Two domains are employed in the model. The first domain situate from 02˚N to 40˚N and 118˚E to 149˚E and cover spatial resolution () of 33.1 km. The second domain situate from 09˚N to 27˚N and 119˚E to 132˚E with of 11 km. Timestep of the model () is 120 seconds. The model is supported by the following physical parameterization, i.e., Yonsei University Scheme (YSU) in the boundary layer, Kain-Fritsch scheme (KF) in the cumulus, and WRF Single-Moment 3-class scheme in the microphysics. Initial meteorological condition prior to the formation of the cyclone is generated using WRF ARW standard-release model. Sensitivity of the model output is obtained from a selected single-parameter change scenarios, namely, 10 % to 20 % decrease and increase of wind shear initial data at 850-200 hPa, and by 10 % to 20 % decrease of relative humidity initial data at 850-700 hPa. The result showed that the negative correlations between wind shear and intensity are found in wind shear scenarios. Wind shears of 10 ms-1 which lead to strengthening of the wind intensity in the early period of Typhoon development are found in wind shear scenarios. The effect of wind shear changes on wind intensity is statistically significant in the 20 % wind shear scenarios. During mature stage, weak wind intensity occurred when wind shear increase as given in the WRF standard-release and the 20 % decreasing scenario. Different situation is found in the 20 % increasing scenario where wind shear tend to weak and lead to strong wind intensity at this stage. Meanwhile, the reduction of moisture supply at 850-700 hPa resulting from 20 % decreasing relative humidity play a major role in the weakening of wind intensity and reduces mechanical energy of the cycle process as much as 300 J kg-1.
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