Identifying the source and transformation of riverine nitrates in a karst watershed, North China: Comprehensive use of major ions, multiple isotopes and a Bayesian model.

Nitrate (NO) contamination of surface water is a globally concern, especially in karstic regions affected by intensive agricultural activities. This study combines hydrochemistry, and environmental isotopes (δH, δO, δN, and δO) with a Bayesian isotope mixing model (Simmr) to reduce the uncertainty in estimating the contributions of different pollution sources. Samples were collected from 32 surface water sites in the Yufu River (YFR) watershed, North China, in September and December 2019.

A sensitive ratiometric fluorescent sensor for zinc(II) with high selectivity.

A new fluorescent Zn²⁺ chemosensor (P1) based on a functionalized porphyrin was synthesized and characterized. P1 displayed dramatic ratiometric variations in absorption and fluorescent emission spectra upon exposure to Zn²⁺ due to the formation of a 1:1 Zn²⁺/P1 complex. The sensor also exhibited high selectivity and sensitivity toward Zn²⁺ over other common metal ions in the physiological pH range with a detection limit of 1.