Karakteristik Vegetasi di Hutan Alam Dataran Rendah, Hutan Tanaman, dan Lahan Pasca Tambang Nikel di Kabupaten Bombana

Nickel mining in Bombana District is one of the mining activities which generates a very large income for the area. However, mining carried out continuously will certainly cause the environment to be damaged, especially soils and vegetation when mining activities end. Good management of post-mining land is one of the obligations of the mining business unit. Management can include reclamation and replanting land so that exposed land can be reforested. Reforesting ex-mining land is not easy. These efforts need to be carried out with comprehensive treatment concerning the improvement of the vegetation composition as well as the physical, chemical, and biological aspects of the soil used so that the greening plants that are introduced can adapt well. The purpose of this study is to identify and compare the characteristics of vegetation and soil in lowland natural forests, plantations and post-nickel mining in Bombana District. In this study, observations were made at three different locations to look for differences in characteristics caused by the existence of nickel mining activities. From the results of the study showed that there was a decrease in the composition of vegetation due to changes from natural forest to plantations. In addition, the level of soil fertility is also declining due to land clearing for mining. Key words : nickel, mining, Bombana, soil, vegetation

Rotating ring-disk voltammetric investigations on the degradation rate of the nickel(III)-glycylglycyl-L-histidine complex

The voltammetric behavior of the Ni(II)/glycylglycyl-L-histidine complex and the degradation of the electrogenerated Ni(III) species were investigated by cyclic voltammetry. Results of electrochemical and spectrophotometric experiments indicated some differences in the nature and reactivity of Ni(III) complexes formed by two independent routes, i.e., anodic oxidation of Ni(II) and homogeneous oxidation by an autocatalytic reaction in a medium containing oxygen and S(IV) (H2SO3, HSO[Formula: see text], and SO[Formula: see text]). The Ni(III) species formed electrochemically reacts in a fast chemical process (EC mechanism) and the observed rate constant of the degradation (k = 0.17 s–1) was determined by a rotating ring-disk electrode technique measuring kinetic collection efficiency values as a function of the rotation rate. Key words: nickel, glycylglycyl-L-histidine, sulfite, degradation reaction, rotating ring-disk voltammetry.

Nickel essentiality and homeostasis in aquatic organisms

It has been well established that a number of trace metals are essential for various biological functions and are critical in many of the enzymatic and metabolic reactions occurring within an organism. The essentiality of nickel is now generally accepted, based on the numerous symptoms caused by nickel deficiency (mainly in terrestrial vertebrates) and its essential role in various enzymes in bacteria and plants. The information on optimal and deficient concentrations of nickel, however, is limited and the essentiality of nickel to aquatic animals is not established. The purpose of this review is to synthesize the available information on nickel essentiality and homeostasis in aquatic organisms. There is less information on these topics compared to that for other essential metals. Nickel essentiality to aquatic organisms can only be confirmed for plants and (cyano)bacteria due to the documented role of nickel in the urease and hydrogenase metabolism. Deficiency levels ranged from 10-12 M to 2 × 10-6 M Ni in different species. No studies were identified that had the explicit objective of evaluating homeostatic mechanisms for nickel in aquatic life. However, inferences could be made through the evaluation of nickel bioconcentration and tissue distribution data and a comparison to other metals that have been more thoroughly studied. Data suggest active regulation and therefore nickel essentiality, since there are no known examples of active regulation of non-essential metals in invertebrates. Key words: nickel, essentiality, homeostasis, bioconcentration, regulation.

Nucleophilic additions of lactam-derived enol triflates to aldehydes mediated by nickel(II) and chromium(II) salts

Enol trifluoromethanesulfonates (triflates) derived from N-protected lactams undergo nickel(II)-chloride- and chromium(II)-chloride-promoted carbonyl additions to aldehydes. The yields of this process range from 42%–84%.Key words: nickel(II) chloride, chromium(II) chloride, carbonyl addition, lactam-derived enol triflate.

Outer-sphere electron transfer reactions of aqua(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-1-acetato) nickel(II) and (III).

The outer-sphere oxidation of the nickel(II) complex of the deprotonated pendant-arm macrocycle, 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane-1-acetate, [NiL1(OH2)]+ by bis-(1,4,7-triazacyclononane)nickel(III), [Ni(tacn)2]3+ has been studied in aqueous perchlorate media. The reaction displays reversible second-order behaviour and the kinetic study reveals the forward and reverse rate constants for the reaction: [Formula: see text] The kinetics show the forward reaction to be acid dependent, a feature that is attributed to protonation of the acetato group of the nickel(II) complex. Using Marcus theory, the self-exchange rate for the [NiL1(OH2)]+/2+ couple has been calculated. The nickel(II/III) electron transfer is a reversible one electron process with E° = 1.04 V (vs. S.H.E.). The formation of the authentic nickel(III) product has been confirmed by esr spectroscopy. The kinetics of reduction of the [NiL1(OH2)]2+ species by Fe2+(aq) exhibits a second-order rate law, the reaction being independent of acid. Using the calculated self-exchange rate for the nickel complex, its reaction with Fe2+(aq) has been examined in terms of an inner- versus outer-sphere mechanism. Key words: nickel(III), pendant-arm macrocycles, hexaaquairon(II), outer sphere, kinetics, Marcus theory.

Remediating Ni-phytotoxicity of contaminated Quarry muck soil using limestone and hydrous iron oxide

Remediation of excessive soil metals in situ is receiving new attention because the alternative, soil removal and replacement, is very expensive, requires disposal of the removed soil and may achieve no better environmental remediation than the in situ treatments. A factorial pot experiment was conducted with two muck soils contaminated by a Ni refinery; we tested the effectiveness of making the soil calcareous and addition of freshly precipitated hydous ferric oxide (HFO) in reducing soil Ni phytotoxicity to the Ni-sensitive crops, oat and redbeet, and a Ni-resistant crop, wheat. Fertilized but otherwise untreated soil caused significant Ni phytotoxicity to oats and redbeet, but not to wheat, on both soils. Adding limestone reduced the concentration of Ni in shoots of all species and alleviated the symptoms specific to Ni phytotoxicity in oat (banded chlorosis). The addition of HFO was more effective in reducing shoot Ni concentration in the redbeets than in crops from the Poaceae family. Both amendments induced phosphorus and/or manganese deficiency depending on the crop tested. The experiment indicates that some combination of limestone and Fe oxides can readily remediate Ni phytotoxicity of the tested soils, but that Mn and P fertilizers would be needed to achieve practical in situ remediation of Ni phytotoxicity of Quarry muck (Terric Mesisol). Key words: Nickel, soil, plant, phytotoxicity, remediation

Reflectance infrared and UV–visible spectroelectrochemical studies on a series of [Ni3(µ3-L)(µ3-I)(µ2-dppm)3][PF6] (L = CO; CNR, R = alkyl, aryl; dppm = Ph2PCH2PPh2) clusters

The trinuclear nickel clusters [Ni3(µ3-L)(µ3-I)(µ2-dppm)3]+ (L = CO (1); CNR, R = CH3 (2), i-C3H7 (3), C6H11 (4), t-C4H9 (5), CH2C6H5 (6), C6H5 (7), p-C6H4I (8), p-C6H4F (9), p-C6H4CH3 (10), p-C6H4CF3 (11), p-C6H4OCH3 (12), p-C6H4CN (13), 2,6-(CH3)2C6H3 (14); dppm = Ph2PCH2PPh2) all contain a triply bridging π-acceptor (carbonyl or isocyanide) ligand. Compounds 1–14 all undergo single electron reductions over a relatively narrow range of E1/2( +/0) (−1.08 V to –1.18 V vs. SCE in acetonitrile) and are known electrocatalysts for the reduction of carbon dioxide. Specular reflectance infrared spectroelectrochemical (SEC) measurements on 1–14 indicate that the capping isocyanide or carbonyl ligand remains triply bridging (µ3,η1) upon single electron reduction. The magnitude of the ν(C≡O) or ν(C≡N) absorption band shift upon reduction is related to both the electronic and steric properties of the capping π-acceptor ligand. Spectroelectrochemical studies with UV–visible detection revealed a hypsochromic shift upon reduction of the clusters. The SEC cell and spectrometer utilized are extremely versatile and allow for data from 600 to 22 000 cm−1 to be acquired without modifying the SEC cell and making only minor configuration changes to the spectrometer. Key words: nickel, cluster, carbonyl, isocyanide, spectroelectrochemical.