The evaluation of N/P fate using the SPARROW model: a case study in an arid and semi-arid region, northern China.

The assessment of nutrients' fate from source to sink is critical to water quality control. As an important ecological reserve in the arid and semi-arid regions of China, the Luanhe River Basin (LRB) has suffered from the deterioration of water quality, thus leading to the urgent management and control. However, few studies have devoted to exploring the fate of N/P contaminations for the entire watershed, due possibly to the large drainage area and heterogeneous watershed composition. Here, we attempt to illustrate N/P contaminations delivery and retention processes using the SPAtially Referenced Regression On Watershed attributes (SPARROW) model. The model reveals 97% of the spatial variability in the TN load and 81% in the TP load, verifying its availability and credibility. The results indicate that anthropogenic sources are dominating the N/P load, which account for 68.5% of N and 74.6% of P inputs. The results highlight the significant retention effects of streams and reservoirs, with 16.4% of N and 13.4% of P removals by streams and 24.3% of N and 10.7% of P removals by reservoirs, respectively. Ultimately, only 49,045.2 t yr-1 (or 16.9%) of N and 1668.7 t yr-1 (or 17.1%) of P being transported to the Bohai Sea. In addition, the analysis of influencing factors showed that regional characteristics (e.g., topography, rainfall), stream size, and delivery distance are potential factors affecting the riverine transport, whereas flow rate and surface area are primarily affecting the reservoirs attenuation. In the future, the watershed water quality management should pay more attention to source management and pollution legacy risks to achieve sustainable and healthy watershed development.

Continuous Charge Transport in Carbon Nitride Modulated by Interfacial Chemical Bond and Homophase Junction to Boost Photocatalytic Hydrogen Production.

Efficient separation of photogenerated electrons and holes is of key importance in photocatalysis. Tuning the charge separation pathway is significant but still suffering from low efficiency for the charge extraction from semiconductors. Herein, taking 2D g-C3 N4 (CN) nanosheets as a model photocatalyst, it was found the decoration of homophase junction between brookite TiO2 rods and nanoparticles (BN -BR ) onto CN can effectively modulate photogenerated charge extraction and transfer in BN -BR /CN composites. The BN -BR /CN exhibits a remarkably enhanced photocatalytic H2 evolution under visible light irradiation (λ>420 nm) compared with the single component. A continuous electron transfer channel constructed by an interfacial chemical bond Ti-O-N between CN and brookite rods (BR ) and BN -BR homophase junction between brookite nanoparticles and rods was proposed to benefit the charge extraction and transfer. This work provides a strategy to tune the charge separation and transfer to facilitate the photocatalytic performance in heterogeneous photocatalysis.