Occurrence,spatial and seasonal variation,and environmental risk of pharmaceutically active compounds in the Pearl River basin,South China

The occurrence,fate,and environmental risk of 40 pharmaceutically active compounds(PhACs)from surface waters and sediments were comprehensively investigated in the Beijiang River,Xijiang River,and Maozhou River of the Pearl River basin,South China.Salicylic acid and diclofenac(antiinflammatory drugs),gemfibrozil(a lipid regulator),carbamazepine(an antiepileptic drug),diazepam(a psychoactive drug),and 2-methyl-4-chloro-phenoxyacetic acid(MCPA,a pesticide)were the most ubiquitous compounds in the studied region.The average concentrations of detected PhACs in surface waters and sediments ranged from 0.17 to 19.1 ng/L and 0.10 to 10.4 ng/g,respectively.Meanwhile,PhACs concentration in surface waters and sediments varied greatly among and within the Beijiang River,Xijiang River,and Maozhou River.The largest annual flux of PhACs of the Xijiang River and Beijiang River was more than 11000 kg per annum,whereas only 25.7 kg/a in the Maozhou River.In addition,the estimated emissions of PhACs in the Beijiang River,Xijiang River,and Maozhou River ranged respectively from 0.28 to 4.22 kg/a,0.12 to 6.72 kg/a,and 6.66 to 91.0 kg/a,and the backestimated usage varied with a range from 12.0 to 293 kg/a,6.79 to 944 kg/a,368 to 17459 kg/a.Moreover,the emissions of PhACs showed a close relationship with the gross domestic product(GDP)of each city along the Pearl River.The environmental risk assessment suggested that diazepam and ibuprofen had a moderate risk in this region.

Removal of sulfamethoxazole by nanofiltration membrane

The retention of sulfamethoxazole (SMZ) by nanofiltration (NF) membranes is strongly influenced by the pH value of the solution. The retention of SMZ reaches its peak value when the solution pH rises above its pKa2 value as the compound transforms into a negatively charged species. Charge repulsion is the main mechanism involved in SMZ removal by NF membranes. In this study, the removal of SMZ by NF membranes, as a function of solution chemistry, was examined at pH 8.9 to investigate the effect of solution conditions on charge repulsion. The results show that the retention of negatively charged SMZ is relatively independent of SMZ concentration, and an increase in the ionic strength of the solution causes a relatively small reduction in retention. A small effect of humic acid (HA) on SMZ retention was noticed at pH 8.9, which can be explained by a small but insignificant improvement in the zeta potential of the membrane caused by HA at high pH values. However, it was found that SMZ concentration in the feed decreased significantly in solutions containing tannic acid (TA). The Adams-Bohart model was applied to our experimental data and was found to be suitable for describing the initial part of the breakthrough curves. The adsorptive parameters of the membrane were determined.