Judul: Persebaran Fosfor Secara Spasial Di Perairan Waduk Jatigede, Kabupaten Sumedang, Jawa Barat
Abstrak: Akumulasi bahan organik yang tinggi ke dalam ekosistem perairan waduk akan meningkatkan ketersediaan nutrien salah satunya fosfor. Penelitian ini bertujuan menganalisis persebaran fosfor secara spasial dan faktor-faktor yang mempengaruhi keberadaan fosfor di Waduk Jatigede. Pengambilan contoh dilakukan pada bulan Februari hingga April 2021 pada enam stasiun pengamatan. Analisis data terdiri atas sebaran spasial horizontal dengan ArcMap 10.5, sebaran vertikal dengan Ocean Data View, analisis klaster, analisis komponen utama dan korelasi Pearson dengan perangkat lunak R Studio. Zona Waduk Jatigede terdiri dari Zona Riverine, Zona Transisi, dan Zona Lakustrin. Konsentrasi fosfor total berkisar antara 0,075˗0,130 mg L-1, sedangkan ortofosfat berkisar antara 0,004˗0,023 mg L-1. Sebaran fosfor total dan ortofosfat di lapisan epilimnion memiliki sebaran yang tertinggi di Zona Riverine. Sebaran fosfor total di lapisan hipolimnion dan sedimen memiliki sebaran yang tertinggi di Zona Lakustrin. Fosfor tersebar dengan merata, baik secara horizontal maupun vertikal dengan kecenderungan lebih tinggi di Zona Riverine dan lapisan epilimnion. Sebaran fosfor dipengaruhi parameter fisika dan kimia perairan yang terdiri atas parameter suhu, kekeruhan, pH, dan oksigen terlarut., The accumulation of high organic matter into the reservoir water ecosystem will increase the availability of nutrients, one of which is phosphorus. This study aims to analyze the spatial distribution of phosphorus and the factors that influence the presence of phosphorus in the Jatigede Reservoir. Sampling was carried out from February to April 2021 at six observation stations. Data analysis consisted of horizontal spatial distribution using ArcMap 10.5, vertical distribution using Ocean Data View, cluster analysis, principal component analysis and Pearson correlation with R Studio software. The Jatigede Reservoir Zone consists of the Riverine Zone, Transition Zone, and Lacustrin Zone. The total phosphorus concentration ranged from 0.075˗0.130 mg L-1, while orthophosphate ranged from 0.004˗0.023 mg L-1. The distribution of total phosphorus and orthophosphate in the epilimnion layer has the highest distribution in the Riverine Zone. The distribution of total phosphorus in the hypolimnion and sediment layers has the highest distribution in the Lacustrin Zone. Phosphorus is evenly distributed, both horizontally and vertically with the tendency to be higher in the Riverine Zone and the epilimnion layer. The distribution of phosphorus is influenced by physical and chemical parameters of the waters which consist of parameters of temperature, turbidity, pH, and dissolved oxygen
Keyword: fosfor, sebaran spasial, Waduk Jatigede, Zona Riverine

Judul: Keterkaitan Keberadaan Fosfor dalam Sedimen dan Air di Waduk Jatigede, Sumedang, Jawa Barat
Abstrak: Keberadaan fosfor berupa materi yang mengendap pada sedimen dan materi terlarut pada kolom air. Namun faktor yang mempengaruhi keberadaan fosfor sedimen dan air pada dasar perairan belum dapat dipahami dengan baik penyebabnya. Penelitian ini bertujuan menganalisis faktor yang mempengaruhi sebaran fosfor dalam sedimen dan air di Waduk Jatigede. Pengambilan contoh dilakukan pada bulan Febuari, Maret, dan April 2021 di enam stasiun pengamatan. Analisis data terdiri dari uji signifikansi kesamaan antarwaktu, penentuan musim, pengelompokan stasiun, sebaran fosfor sedimen dan air, keterkaitan fosfor sedimen dan air dengan parameter fisika-kimia sedimen dan kualitas air, serta pendugaan pertukaran fosfor antar sedimen dan air. Berdasarkan curah hujan BMKG kondisi musim Waduk Jatigede yaitu musim hujan. Waduk Jatigede terdiri dari Zona Riverin, Zona Transisi, dan Zona Lakustrin. Konsentrasi fosfor sedimen dan air lapisan hipolimnion tertinggi pada Zona Lakustrin. Sebaran fosfor sedimen dan air menunjukan adanya keterkaitan. Faktor yang mempengaruhi keterkaitan tersebut adalah parameter fisika-kimia sedimen (debu, liat, P-tersedia, pH sedimen, dan DO) dan kualitas air (suhu, kekeruhan, TSS, ortofosfat, DO, pH, dan alkalinitas)., The presence of phosphorus in the form of material that settles in the sediment and dissolved material in the water column. However, the factors that affect the presence of phosphorus in sediments and water at the bottom of the water are not well understood. This study aims to analyze the factors that influence the distribution of phosphorus in sediment and water in the Jatigede Reservoir. Sampling was carried out in February, March, and April 2021 on six observation stations. Data analysis consists of testing the the similarity between times, determining the season, grouping stations, distribution of phosphorus in sediment and water, the relationships between phosphorus in sediment and water with the physico-chemical parameters of sediment and water quality, as well as estimation of the exchange of phosphorus between sediment and water. Based on rainfall intensity, the study period in the Jatigede Reservoir occured in the rainy season. Jatigede Reservoir consists of Riverine Zone, Transition Zone, and Lacustrine Zone. Results showed the highest concentration of phosphorus in sediment and water in the hypolimnion layer was in the Lacustrine Zone. There were strong relationships between phosphorus in sediment and water. The most influencing factors of these relationships were physico-chemical parameters of sediment (i.e. dust, clay, available P, sediment pH, and DO) and water quality (i.e. temperature, turbidity, TSS, orthophosphate, DO, pH, and alkalinity).
Keyword: Fosfor, Sedimen, Hipolimnion

Judul: Truncated Stop Loss as a Optimal Solution of Reinsurance Agreement in One-Period Model
Abstrak: Reinsurance is one of risk management efforts of an insurance company, which is called the cedent. Similar with insurance, reinsurance constitutes the cedent to pay the premium. We consider one-period reinsurance model and derive a rule which minimizes the ruin probability of the cedent for a fixed reinsurance premium. Therefore, it is needed to construct an optimal reinsurance agreement for the cedent. The premium is calculated according to four different principles, i.e. economic, generalized zero-utility, Esscher, and mean-variance principles. Stop loss is a reinsurance contract which protect the insurance company for losses that exceed a certain amount. The result of this research shows that a truncated stop loss is an optimal agreement in the class of all reinsurance contracts with various premiums calculated using above mentioned principles.
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