Bulk/wet deposition of trace metals to rural, industrial, and urban areas in the Yangtze River Delta, China.

The bulk depositions of trace metals to three land uses in the Yangtze River Delta are investigated based on the collected 154 precipitation samples from August 2015 to May 2017. The volume-weighted mean (VWM) concentrations of Ni, Cu, Zn, Cd, and Pb were 13.28, 5.32, 13.02, 0.33, and 10.53 µg L-1, and 12%, 16%, 3%, 11%, and 26% of precipitation events exceeded the limits in the Central Drinking-Water Source Area (GB3838-2002), respectively. Furthermore, the five metals varied significantly under urban, industrial, and rural land use conditions, indicating that these metal concentrations were greatly determined by local sources; lower concentrations were found in sea and local air masses than in air masses from inland trajectories. Combining the precipitation amounts, the bulk deposition fluxes of the five metals were 25.99, 25.47, 20.60, 10.40, 0.64 mg m-2 yr-1. By comparing the metal deposition fluxes in 98 studies across China, Ni and Pb deposition in the Yangtze River Delta was higher, while that of Cd and Zn was lower than their respective averages across China, indicating that Ni and Pb pollution should receive more attention in the study area. CAPSULE: Bulk/wet deposition fluxes of trace metals varied greatly among rural, industrial, and urban areas, and Pb and Ni showed severe pollution levels in the Yangtze River Delta.

Long-term trends in NO2 columns related to economic developments and air quality policies from 1997 to 2016 in China.

This study detected the long-term trends in NO2 concentrations in China from 1997 to 2016 based on the NO2 columns from GOME, SCIAMACHY, and GOME-2A. Both differences in the time-overlapped NO2 columns from GOME vs. SCIAMACHAY and SCIAMACHAY vs. GOME-2A showed seasonal variations, and the annual NO2 columns from GOME were 0.9% higher than those from SCIAMACHY, which exceeded that from GOME-2A by 14%. The long-term trends of the NO2 columns on a provincial scale could be simulated by cubic models (0.60 < R2 < 0.96, p < 0.05) and presented three shapes: first decreasing then increasing and decreasing again; first decreasing then increasing; and continuously decreasing. The peak years of NO2 columns in 17 provinces occurred in 2011 and 2012. These trends in NO2 columns were determined by the economic developments and enacted air quality policies in nearly all the provinces except for Xizang and Qinghai Provinces, where the trends were determined by natural NOx emission sources. In detail, the panel data analysis showed that the simulated model had fixed effects, and the thermal power generation, consumption of diesel oil in agriculture, passenger traffic by highways, and freight traffic by highways significantly increased NO2, while the air quality policies in the 12th five-year plan decreased NO2 columns from 1997 to 2016. The benefits to decreasing NO2 columns from the air quality policies issued in the 10th and 11th five-year plans were offset by the quickly increasing economies.

Dry Particulate Nitrate Deposition in China.

A limited number of ground measurements of dry particulate nitrate deposition (NO3-) makes it difficult and challenging to fully know the status of the spatial and temporal variations of dry NO3- depositions over China. This study tries to expand the ground measurements of NO3- concentrations at monitoring sites to a national scale, based on the Ozone Monitoring Instrument (OMI) NO2 columns, NO2 profiles from an atmospheric chemistry transport model (Model for Ozone and Related chemical Tracers, version 4, MOZART-4) and monitor-based sources, and then estimates the NO3- depositions on a regional scale based on an inferred model. The ground NO2 concentrations were first derived from NO2 columns and the NO2 profiles, and then the ground NO3- concentrations were derived from the ground NO2 concentrations and the relationship between NO2 and NO3- based on Chinese Nationwide Nitrogen Deposition Monitoring Network (NNDMN). This estimated dry NO3- depositions over China will be helpful in determining the magnitude and pollution status in regions without ground measurements, supporting the construction plan of environmental monitoring in future.