Gold nanoparticles are exciting materials because of their potential applications in optics, electronics, biomedical, and pharmaceutical fields. In recent years, environmentally friendly, low-cost biosynthesis methods with bio-applicable features have continued to be developed for the synthesis of gold nanoparticles. In the present study, an actinobacterial strain was isolated from the Petrosia ficiformis (Poiret 1798) sponge, which was collected from a marine environment, and the gold nanoparticle synthesis was performed for the first time from the bacteria type belonging to the Citricoccus genus. The synthesis conditions were optimized using the Box–Behnken experimental design, with a statistical method that included three independent variables (temperature, time, and mixture ratio) to affect the synthesis at three levels (+1, 0, and −1). Accordingly, the conditions proposed for the biosynthesis of gold nanoparticles at the maximum optical density values that are specific for the Citricoccus sp. K1D109 strain were estimated as 35°C temperature, 24 h, and 1/5 mixture ratio (cell-free extract/HAuCl₄ · 3H₂O). When recommended conditions were applied, it was determined that the maximum absorbance of the synthesized gold nanoparticles is 1.258 at 545 nm, and their sizes are in the range of 25–65 nm, according to transmission electron microscopy (TEM) data.

Tunceli, Turkey is one of the small cities in the Eastern Anatolian Region with substantial natural, cultural and historical heritage that is suitable to be a slow city. Water sources are abundant in the area due to rain and heavy snowfall in the mountains, which seeps into the ground or flows into the rivers. Therefore monitoring and conservation of city’s drinking water quality is one of the main issues in the city. The present study was conducted to investigate several heavy metals and cyanide, arsenic, and selenium concentrations of drinking water samples taken from 100 different locations in the city and towns of Tunceli, Turkey during the years 2011 and 2012. In three locations, high levels of copper was found with a range of 2.1–11.5 mg/L, and high levels of arsenic was detected in five locations with a range of 10.5–78.0 μg/L, exceeding the action levels for copper and arsenic. For health risk assessment, the average daily dose and hazard quotient (HQ) were calculated. The region mean values of HQ were found above 1 for arsenic in the samples collected from Mazgirt, while HQ values were below 1 in the rest of the samples.