Data relating to carbonaceous components in Songkhla Lake sediments, Thailand

The focus of this research was to present a data article associated with organic carbon (OC) and elemental carbon (EC) preserved in lake sediments. Descriptive statistics were applied in this dataset. Sediment cores were sliced immediately at the following layers: 0–20; 20–40; 40–60; 60–80; 80–100; 100–120; 120–140; 140–160; 160–180; 180–200; 200–220; 220–240; 240–260; 260–280; 280–300; 300–320; 320–340; 340–360; 360–380; 380–400; 440–460; 460–480; 480–500; 500–520; 520–540; 540–560 and 560–580 mm of depth. Chemical analysis of OC (i.e. OC1, OC2, OC3, OC4), EC (i.e. EC1, EC2, EC3), and the pyrolyzed organic carbon (OP) (i.e. OP1, OP2, OP3, OP4, OP5, OP6, Char, Soot) contents was conducted by using a DRI Model 2001 Thermal/Optical Carbon Analyzer. The chemical characterization coupled with statistical analysis reveal that vehicle exhausts are the most prominent factor governing OC/EC data detected in core sediments. These data underline some noticeable concerns associated with ecotoxicology and environmental safety of residents surrounding the Songkhla Lake.

&  Subject area  Environmental Sciences  More specific subject area  Environmental Chemistry  Type of data  Table,  was specifically designed for this study. All materials used for core sectioning were washed carefully with detergent and water, and rinsed successively with methanol and dichloromethane prior to removing the frozen core from the freezer. The freeze dried lake sediment samples were ground and homogenized with an agate mortar and sieved though a 200-mesh sieve. The sample pre-treatment procedure has been clearly described in previous studies [3,4].

Value of the data
Analytical data can be used as a base-line data for OC/EC concentration levels in sediments of Songkhla Lake.
OC/EC data plays a crucial role in governing climate system, therefore, continuous chemical characterization of carbonaceous compositions in lake sediments is undoubtedly essential for atmospheric modellers to reconstruct the paleoclimate.
Data displayed here can be served as benchmarks for other studies highlighting in the field of ecotoxicology to evaluate sediment-water partitioning of POPs by applying OC/EC contents.
Data of OC/EC ratios can be applied to assess the impacts of vehicle exhausts, biomass burnings and volcanic eruptions. This was about giving policy makers the actual tools that will enable them to develop pollution control policy that can also be referred to as scientific evidence-based decisionmaking. Table 1 displays vertical profile of OC1, OC2, OC3, and OC4 in Songkhla Lake sediments. Table 2 shows concentrations of EC1, EC2, and EC3 in different sediment layers. Table 3 illustrates contents of OP1, OP2, OP3, OP4, OP5, and OP6 in Songkhla Lake sediments.

Dataset area
All sediment samples were collected at the Thale Noi Lake (TNL), which is the second largest lagoon lake in Southeast Asia. TNL became internationally regarded as an ecosystem dynamic hotspot in 1975 when the Ministry of National Resources and Environment (MNRE) and in conjunction with the International Union for Conservation of Nature (IUCN) declared it a Protected Area Category III (Natural Monuments). TNL can be further separated into four subareas namely Melaleuca forests (170 km 2 ), Rice Paddies (153 km 2 ), Swamp (109 km 2 ), and Open Water (28 km 2 ). It is also crucial to underline that TNL is located in the northern part of Thale Luang, Thale Sap, and Songkhla Lake. The area around TNL constructs of farmland, forests, and swamps. There is no main river flowing through this area, but sediment loads from many small man-made canals as well as run-off water from the high steep mountains is observed [5]. The sediment core samples of TNL were collected from three sites (Fig. 1).

Sample collection and analytical procedures
A sediment core sampling equipment (i.e. a transparent PVC plastic tube 12 cm in diameter 1.2 m in length) was carefully dropped from a vessel. All sampling equipment employed for sediment sampling were precleaned cautiously with detergent and deionized water, and rinsed continuously with methanol and dichloromethane. Further information related with QA/QC protocols were strictly followed the standard operating procedure for the USGS Reston, Virginia Environmental Organic Geochemistry Laboratory Appendix 3 (https://water.usgs.gov/nrp/biogeochemical-processes-in- groundwater/forms/SOP_LMWOA_05272015_FINAL_Website.pdf). Pre-treatment processes of freezedried core sediment samples were clearly mentioned in earlier investigations and will not be discussed here [3,4]. All core sediment samples were both qualitatively and quantitatively characterized by using a DRI Model 2001 Thermal/Optical Carbon Analyser (Desert Research Institute, Division of Atmospheric Sciences 2215 Raggio Parkway Reno, NV 89506) [1,2]. The application of an analytical equipment is fundamentally relied on the advantageous oxidation of OC and EC components at numerous heating conditions. Its function relies on the fact that organic compounds can be volatilised from the sample deposit in a non-oxidising He atmosphere while EC must be combusted by an oxidiser. According to the IMPROVE_A method, OC1, OC2, OC3, and OC4 represent the quantities of carbon evolved from the filter during each of four non-oxidizing heat ramps at 120°C, 250°C, 450°C, and 550°C, respectively. Four different OC fractions (i.e. OC1, OC2, OC3, and OC4) were carefully selected because of its useful parts of the source fingerprints [1, [6][7][8][9]. Then a 2% O 2 /98% He was introduced, and the oven temperature was raised to 550°C, 700°C and 800°C, producing three EC fractions: EC1, EC2, and EC3. Total carbon (TC, no carbonate carbon included in this study) is the sum of all carbon fractions. Evolved carbon gases were oxidized to CO 2 , then reduced to CH 4 for detection with a flame ionization detector. Some of the organic carbon chars in the inert He environment, as indicated by decreased reflectance or transmittance of the laser from the sample deposit. Once in the oxidizing atmosphere, the pyrolyzed organic carbon (OP) leaves the filter. The quantity of OP is defined as the carbon that evolves to the time at which the laser reflectance or transmittance achieves its initial value. OP1, OP2, and OP3 are reflectance-corrected OP, corresponding the minimum (the beginning of the laser reflectance that achieves its initial value), middle (the stable condition of the laser reflectance that achieves its initial value), and maximum OP (the last point that the laser reflectance start to leave its initial value). Correspondingly, OP4, OP5, and OP6 indicate the transmittance-corrected minimum, middle, and maximum OP. For more details of analytical processes of OC/EC were previously mention in other studies and will not be discussed here [1,2].

Transparency document. Supporting information
Transparency data associated with this article can be found in the online version at https://doi.org/ 10.1016/j.dib.2019.01.039.