Evaluation and optimization of ecological landscape pattern for urban agglomeration in the Pearl River Delta, China.

The evaluation and optimization of landscape ecological pattern has important implications for the accurate improvement of forest quality and high-quality urban development in the Pearl River Delta urban agglomeration. Based on the "one map" data and digital elevation model data of forest resource management in 2021, we evaluated and optimized landscape ecological pattern of the Pearl River Delta urban agglomeration by morphological spatial pattern analysis and minimum cumulative resistance model. The results showed that there were 435861 patches in the Pearl River Delta urban agglomeration that could be used as ecological source area, covering an area of 7346.60 km2 and accounting for 13.4% of the Pearl River Delta area. Thirty patches were selected as the ecological source area of the study area by using the area and patch importance index, covering an area of 2792.59 km2 and accounting for 5.1% of the Pearl River Delta area. The overall natural environment of the Pearl River Delta urban agglomeration was excellent. The ecological resistance level was small. The peripheral ecological resistance was low. The core ecological resistance was high. There was still a large room for adjustment of stand types and landscape patterns, which should be optimized by adjusting the composition and spatial distribution of tree species. The ecological network of the Pearl River Delta urban agglomeration was optimized with 30 ecological sources, 103 key ecological corridors, and 95 ecological nodes. The improvement rates of the optimized probability of connectivity index and integral index of connectivity index were 297.5% and 695.1%, respectively. The optimization results could effectively connect the ecological sources and spread the ecological service functions of ecological sources.

[Pollution Characteristics of Macrolide Antibiotics During Drinking Water Treatment and Their Chlorination Reaction Mechanism].

Antibiotic contamination in drinking water has attracted widespread attention. The pollution condition of six macrolide antibiotics (erythromycin-H2[KG-*2/5]O, clarithromycin, oleandomycin, roxithromycin, leucomycin, and tylosin) in two drinking water treatment plants was monitored, and the reaction mechanism of tylosin, a typical macrolide antibiotic, during chlorination disinfection treatment was investigated. The results showed that the six macrolide antibiotics can be widely detected in the drinking water treatment processes; however, their concentrations were generally very low. The concentrations of macrolide antibiotics in the influents and effluents ranged from 0.18 ng·L-1 to 3.97 ng·L-1 and 0.02 ng·L-1 to 1.91 ng·L-1, respectively. The removal rates of the six macrolides in the drinking water treatment were different, ranging from 18% (oleandomycin) to 100% (erythromycin- H2[KG-*2/5]O). The degradation of the six macrolides during chlorination was slow and greatly affected by water quality parameters. The chlorination degradation of tylosin followed the second-order reaction kinetic mode, with the kinetic rate constant of 0.77 L·(mol·s)-1 at pH 7.0. Nine chlorination degradation products of tylosin were detected, and the reaction pathways primarily included tertiary amine hydroxylation, aromatic oxidation, and epoxy addition.