Environmentally relevant concentrations of di(2-ethylhexyl)phthalate exposure alter larval growth and locomotion in medaka fish via multiple pathways.

Di(2-ethylhexyl)phthalate (DEHP) is a commonly used plasticizer, with evidence of ubiquitous human exposure and widespread occurrence in the aquatic environment. It is an emerging environmental pollutant with regulatory priority; however, most studies have focused on the toxicity of DEHP related to endocrine disruption and reproduction in mammals. The ecotoxicological impact of phthalates (e.g., DEHP) on early life stages of fish under environmentally relevant concentrations of chronic exposure remains unclear. In this study, 7-day post-hatching fry of medaka fish (Oryzias latipes) underwent 21-day continuous exposure to DEHP solutions at 20, 100 and 200 µg/L to assess the effects on fish development and locomotion and related toxic mechanisms. Larval mortality was low with DEHP (20-200 µg/L) within 21 days, but such exposure significantly reduced fish body weight and length and altered swimming behavior. At 21 days, DEHP exposure resulted in specific patterns of larval locomotion (e.g., increased maximum velocity and absolute turn angle) and dose-dependently increased the mRNA expression of acetylcholinesterase (ache) but did not alter AChE activity. Transcriptional expression of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase and peroxisome proliferation-activated receptor and retinoid X receptor genes was significantly suppressed with 21-day DEHP exposure (20-200 µg/L), with marginal alteration in reactive oxygen species levels and antioxidant activities within the dosing period. As well, DEHP altered the mRNA expression of p53-regulated apoptosis pathways, such as upregulated p53, p21 and bcl-2 and downregulated caspase-3 expression, with increased enzymatic activity of caspase-3 in larvae. Our results suggest that toxic mechanisms of waterborne DEHP altered fish growth and locomotion likely via a combined effect of oxidative stress, neurotoxicity and apoptosis pathways.

Cu-TiO2 nanorods with enhanced ultraviolet- and visible-light photoactivity for bisphenol A degradation.

In this study, the microwave-assisted sol-gel method and chemical reduction were used to synthesize Cu-TiO2 nanorod composites for enhanced photocatalytic degradation of bisphenol A (BPA) in the presence of UV and visible lights. The electron microscopic images showed that the Cu nanoparticles at 4.5±0.1nm were well-deposited onto the surface of TiO2 nanorods after chemical reduction of Cu ions by NaBH4. The X-ray diffractometry patterns and X-ray photoelectron spectroscopic results indicated that Cu species on the Cu-TiO2 nanorods were mainly the mixture of Cu2O and Cu(0). The Cu-TiO2 nanorods showed excellent photocatalytic activity toward BPA photodegradation under the irradiation of UV and visible lights. The pseudo-first-order rate constant (kobs) for BPA photodegradation by 7wt% Cu-TiO2 nanorods were 18.4 and 3.8 times higher than those of as-synthesized TiO2 nanorods and Degussa P25 TiO2, respectively, under the UV light irradiation. In addition, the kobs for BPA photodegradation by 7wt% Cu-TiO2 nanorods increased by a factor of 5.8 when compared with that of Degussa P25 TiO2 under the irradiation of 460±40nm visible light. Results obtained in this study clearly demonstrate the feasibility of using one-dimensional Cu-TiO2 nanorods for photocatalytic degradation of BPA and other pharmaceutical and personal care products in water and wastewater treatment plants.

Coupled removal of organic compounds and heavy metals by titanate/carbon nanotube composites.

The objective of this study was to fabricate 1-dimensional (1-D) nanocomposite materials with high aspect ratios and specific surface areas for the coupled degradation of refractory organic compounds and heavy metals. The 1-D nanomaterials were composed of various ratios of carbon nanotubes (CNT) and titanate nanotubes (TNT) (CNT/TNT). Alkaline hydrothermal method was used to fabricate TNT under various hydrothermal conditions. The morphology changed from nanoparticles/nanosheets, nanotubes, nanowires and then to nanoribbon as the hydrothermal temperatures increased from 60 to 230 degrees C. In addition, the CNT/TNT nanomaterials have a good capability toward heavy metal adsorption. The Langmuirian maximum adsorption capacities of nanomaterials were in the range 83-124 mg/g for Cu2+ and 192-588 mg/g for Pb2+, which is superior to that of CNT. The removal efficiency of Cu2+ by CNT/TNT decreased when 40 mg/L MX5B was due to the complexation of MX5B with Cu2+. Results obtained in this study clearly show the 1-D CNT/TNT nanomaterials are a promising nano-adsorbent for coupled removal of organic as well as heavy metal ions in solution.