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.

Detecting Sulfuric and Nitric Acid Rain Stresses on Quercus glauca through Hyperspectral Responses.

Acid rain, which has become one of the most severe global environmental issues, is detrimental to plant growth. However, effective methods for monitoring plant responses to acid rain stress are currently lacking. The hyperspectral technique provides a cost-effective and nondestructive way to diagnose acid rain stresses. Taking a widely distributed species (Quercus glauca) in Southern China as an example, this study aims to monitor the hyperspectral responses of Q. glauca to simulated sulfuric acid rain (SAR) and nitric acid rain (NAR). A total of 15 periods of leaf hyperspectral data under four pH levels of SAR and NAR were obtained during the experiment. The results showed that hyperspectral information could be used to distinguish plant responses under acid rain stress. An index (green peak area index, GPAI) was proposed to indicate acid rain stresses, based on the significantly variations in the region of 500-660 nm. Light acid rain (pH 4.5 SAR and NAR) promoted Q. glauca growth relative to the control groups (pH 5.6 SAR and NAR); moderate acid rain (pH 3.0 SAR) firstly promoted and then inhibited plant growth, while pH 3.0 NAR showed mild inhibitory effects during the experiment; and heavy acid rain (pH 2.0) significantly inhibited plant growth. Compared with NAR, SAR induced more serious damages to Q. glauca. These results could help monitor acid rain stress on plants on a regional scale using remote sensing techniques.

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.

A Review of Spatial Variation of Inorganic Nitrogen (N) Wet Deposition in China.

Atmospheric nitrogen (N) deposition (Ndep), an important component of the global N cycle, has increased sharply in recent decades in China. Although there were already some studies on Ndep on a national scale, there were some gaps on the magnitude and the spatial patterns of Ndep. In this study, a national-scale Ndep pattern was constructed based on 139 published papers from 2003 to 2014 and the effects of precipitation (P), energy consumption (E) and N fertilizer use (FN) on spatial patterns of Ndep were analyzed. The wet deposition flux of NH4(+)-N, NO3(-)-N and total Ndep was 6.83, 5.35 and 12.18 kg ha(-1) a(-1), respectively. Ndep exhibited a decreasing gradient from southeast to northwest of China. Through accuracy assessment of the spatial Ndep distribution and comparisons with other studies, the spatial Ndep distribution by Lu and Tian and this study both gained high accuracy. A strong exponential function was found between P and Ndep, FN and Ndep and E and Ndep, and P and FN had higher contribution than E on the spatial variation of Ndep. Fossil fuel combustion was the main contributor for NO3(-)-N (86.0%) and biomass burning contributed 5.4% on the deposition of NO3(-)-N. The ion of NH4(+) was mainly from agricultural activities (85.9%) and fossil fuel combustion (6.0%). Overall, Ndep in China might be considerably affected by the high emissions of NOx and NH3 from fossil fuel combustion and agricultural activities.