Distribution and influencing factors of atmospheric nitrogen oxides (NOx) over the east coast of China in spring: Indication of the sea as a sink of the atmospheric NOx.

An integrated observation of NOx that included coastal cities and oceanic cruises covering the Qingdao coastal waters sites (QDCW) and the Yellow Sea and East China Sea sites (YECS) was conducted in spring. The average concentrations of the coastal cities, the QDCW, and the YECS were 5.4 ± 4.1, 4.2 ± 3.5, and 2.9 ± 6.8 ppb for NO while 18.5 ± 7.2, 9.4 ± 5.2, and 4.9 ± 6.4 ppb for NO2, depicting lowest levels in the open seas. Atmospheric NO and NO2 showed similar spatial variations over the seas, the stations where the air masses originated from land or nearshore regions showed higher levels, but the decisive influencing factors were not the same in the different study areas. The calculated NOx flux value in the YECS (-8.7 × 10-17 mol N cm-2) indicated that the sea surface was a net sink of atmospheric NOx.

[Distribution characteristics of COD and DO and its influencing factors in the Daliaohe Estuary].

The concentrations of COD and DO were measured in the Daliaohe Estuary in April, July and November of 2010, and their distribution characteristics and influencing factors were discussed. The results showed that the concentrations of COD were 12.10, 4.42 and 4.38 mg · L(-1) in April, July and November of 2010, respectively. They were mainly influenced by rainfall, runoff and municipal sewage. COD values decreased with the increasing DO from the inner of Daliaohe Estuary to adjacent waters. Spatial distribution of COD was mainly controlled by agriculture and urban sewage and tides. The concentrations of DO were 8.46, 4.23 and 10.30 mg · L(-1) in April, July and November of 2010, respectively, and were mainly influenced by temperature and oxygen consumption of organic matter. Hypoxic zone was found in the low-salinity area in summer, which was mainly controlled by excessive emission of organic matter and nutrients in Yingkou, tidal effects and long residence time of water in the estuary.

[Mixing behavior of arsenic in the Daliaohe Estuary].

Mixing behavior of arsenic in the Daliaohe Estuary was studied. Twenty samples were collected from the Daliaohe Estuary during April, July and November, 2010 and arsenic was determined by HG-AFS. The concentrations of arsenic varied from 2.98-44.1, 1.19-14.6, 1.27-12.4 microg x L(-1) in April, July and November. The seasonal variation of arsenic content was significant. In July, the concentration of arsenic was lower than that in April, and higher than that in November. The data indicated that arsenic did not behave conservatively in April and November, but behaved conservatively in July. An important mobilization of dissolved arsenic was observed from the river up to halfway in the estuary in April and November, 2010. Both input flux (from river to estuary) and output flux (from estuary to coastal zone) of dissolved arsenic were calculated from statistical interpretations of the salinity profiles. Concentration of arsenic in the Daliaohe Estuary is higher than large systems, like the Changjiang Estuary and Zhujiang Estuary.