Nurul Farahana Kamaludin

Characterization of rainwater chemical composition after a Southeast Asia haze event: insight of transboundary pollutant transport during the northeast monsoon

Open biomass burning in Peninsula Malaysia, Sumatra, and parts of the Indochinese region is a major source of transboundary haze pollution in the Southeast Asia. To study the influence of haze on rainwater chemistry, a short-term investigation was carried out during the occurrence of a severe haze episode from March to April 2014. Rainwater samples were collected after a prolonged drought and analyzed for heavy metals and major ion concentrations using inductively coupled plasma mass spectroscopy (ICP-MS) and ion chromatography (IC), respectively. The chemical composition and morphology of the solid particulates suspended in rainwater were examined using a scanning electron microscope coupled with energy-dispersive X-ray spectroscopy (SEM-EDS). The dataset was further interpreted using enrichment factors (EF), statistical analysis, and a back trajectory (BT) model to find the possible sources of the particulates and pollutants. The results show a drop in rainwater pH from near neutral (pH 6.54) to acidic (<pH 4.00) during the haze to non-haze transitional period, suggesting that the deposition rate of sulfate and nitrate in the atmosphere via the precipitation process was relatively lower compared to the mineral components. Zinc, nitrate, and calcium, which were the predominant elements in the first rainwater samples. Besides, the results of the SEM-EDS indicated that the zinc was possibly originated from anthropogenic activities which are consistent with the results obtained from EF. The BT model showed that pollutants transported from the mainland of Indo-China and the marine region in the South China Sea were responsible for the high pollution event in the study area. These findings can be useful in identifying contributions of pollutants from single or multiple sources in rainwater samples during haze episodes.

Di-n-butyl­bis­[N-(2-meth­oxy­eth­yl)-N-methyl­dithio­carbamato-κ2S,S′]tin(IV): crystal structure and Hirshfeld surface analysis

A skew trapezoidal bipyramidal coordination geometry based on a C2S4 donor set is found in the structure of (C6H5)2Sn[S2CN(Me)CH2CH2OMe]2, with the SnIV atom lying on a mirror plane.

Di-n-butyl-bis-(N-ethyl-N-phenyl-dithio-carbamato-κS)tin(IV).

The title compound, [Sn(C4H9)2(C9H10NS2)2], features a tetrahedrally coordinated SnIV atom; the dithiocarbamate ligands coordinate in a monodentate fashion, accompanied by two n-butyl chains. The non-coordinating thione S atoms are each proximate to the SnIV atom [3.0136 (7) and 2.9865 (8) Å], giving rise to distortions from the ideal geometry as evident in the wide C—Sn—C bond angle of 139.06 (12) °. In the crystal, C—H⋯S interactions lead to the formation of a linear supramolecular chain along the b axis. The chains are aligned into layers by C—H⋯π interactions, and the layers stack along [001]. One of the ethyl groups is statistically disordered over two sets of sites.

Crystal structures and Hirshfeld surface analyses of bis­[N,N-bis­(2-meth­oxy­eth­yl)di­thio­carbamato-κ2S,S′]di-n-butyl­tin(IV) and [N-(2-meth­oxy­eth­yl)-N-methyl­dithio­carbamato-κ2S,S′]tri­phenyl­tin(IV)

The coordination geometry in (n-Bu)2Sn[S2CN(CH2CH2OCH3)2]2, (I), is based on a skewed trapezoidal bipyramid, while that in (C6H5)3Sn[S2CN(CH3)CH2CH2OCH3], (II), is based on a tetrahedron. In the crystal of (I), supramolecular layers parallel to (10-1) are sustained by methylene-C—H⋯O(methoxy) interactions, while in (II), centrosymmetric dimers are formed via pairwise weak phenyl-C—H⋯π(phenyl) contacts.

(N-Ethyl-N-phenyldithiocarbamato-κS)-triphenyltin(IV)

The title compound, [Sn(C6H5)3(C9H10NS2)], has two independent molecules in the asymmetric unit and each features a tetrahedrally coordinated SnIV atom as the dithiocarbamate ligand coordinates in a monodentate fashion. As the non-coordinating thione S atom is proximate to the Sn atom [Sn⋯S(thione) = 3.1477 (6) and 2.9970 (5) Å for the independent molecules], distortions from the ideal geometry are evident [the widest angle being 120.48 (5)°]. The most notable feature of the crystal packing is the formation of C—H⋯π interactions that lead to the formation of supramolecular layers parallel to (2).

(N-Butyl-N-phenyl­dithio­carbamato-κS)triphenyl­tin(IV)

The title compound, [Sn(C6H5)3(C11H14NS2)], features a tetrahedrally coordinated Sn atom, as the dithiocarbamate ligand coordinates in a monodentate fashion. Due to the proximity of the non-coordinating thione S atom, distortions from ideal tetrahedral geometry about the metal atom are evident with the widest C—Sn—S angle being 117.26 (5)°. In the crystal, molecules are linked by C—H⋯S interactions, which generate helical supramolecular chains along the b axis.

Crystal structures and Hirshfeld surface analyses of (N-hexyl-N-methyl­dithio­carbamato-κ2S,S′)triphenyl­tin(IV) and [N-methyl-N-(2-phenyl­ethyl)­dithio­carbamato-κ2S,S′]tri­phenyl­tin(IV)

The metal coordination geometry in each of the title molecules, [Sn(C6H5)3(C8H16NS2)] (I) and [Sn(C6H5)3(C10H12NOS2)] (II), is based on a heavily distorted tetrahedron owing to the asymmetric mode of coordination of the dithiocarbamate ligand. The persence of C—H⋯π(phenyl) interactions in the crystals lead to dimeric aggregates in (I) and supramolecular chains (II).

Genotoxic Effects on buccal Cells of Workers Exposed toFogging Sprays during Fogging Operation

The number of death due to dengue fever in Malaysia is at an alarming level with 109 deaths reported from 3rd January 2016 to 14th May 2016 [1]. The Government in collaboration with the Ministry of Health Malaysia have been conducting fogging operation to control the spread of dengue in hotspot areas in Malaysia. Thermal fogging spray is recommended as a control measure to kill the mosquitoes at their adult stage [2]. A few chemicals are frequently used in thermal fogging operations, such asmalathion, fenitrothion, fenthion, and some other pyrethroid pesticides [3]. These pesticides, especially malathion, are associated with a genotoxic effect as they could worsen the damage on chromosomal structure in cells [4]. Research by Koutros et al. [5] also found out that there is an increased and aggressive prostate cancer among workers who use a combination of a few pesticides such as malathion, terbufos, and fonofos.

[N-Benzyl-N-(2-phenyl­eth­yl)di­thio­carbamato-κ2S,S′]tri­phenyl­tin(IV) and [bis­(2-meth­oxy­eth­yl)di­thio­carbamato-κ2S,S′]tri­phenyl­tin(IV): crystal structures and Hirshfeld surface analysis

Heavily distorted trigonal–pyramidal coordination geometries, each based on a C3S2 donor set and with the loosely bound S atom approximately trans to one of the ipso-C atoms, are found in the title compounds (C6H5)3Sn[S2CN(Ben)CH2CH2Ph] and (C6H5)3Sn[S2CN(CH2CH2OMe)2].

Triphenyltin(IV) and [bis(2-methoxyethyl)dithiocarbamato-κ2 S,S′]triphenyltin(IV): Crystal structures and Hirshfeld surface analysis

Heavily distorted trigonal–pyramidal coordination geometries, each based on a C3S2 donor set and with the loosely bound S atom approximately trans to one of the ipso-C atoms, are found in the title compounds (C6H5)3Sn[S2CN(Ben)CH2CH2Ph] and (C6H5)3Sn[S2CN(CH2CH2OMe)2].