Sand from Mongolia carried on the wind is a major contributor to the frequent sandstorms that cause air pollution levels to spike in China, a Chinese scientist said.

To date, the northern part of China has been hit by 21 sandstorm events and the one that occurred in middle and late March is the strongest in the past 10 years, said Li Jianjun, chief scientist with China National Environmental Monitoring Center.

"The frequency, severity and wide-ranging effect of the sandstorms is rarely seen in recent years in China," he noted.

He said what's notable this year is that sandstorms from Mongolia exerted a marked impact on air quality in China.

Data from China's National Meteorological Center shows that the abnormal temperature in Mongolia and the western part of China's Inner Mongolia autonomous region made them major contributors to sand in the extreme weather, he said.

Temperatures 2 C to 6 C higher than normal years in the region since February made snow thaw earlier than usual, leaving land bare without any cover, he continued.

He said the sandstorms resulted in excessive air pollutants in over 240 of the total 337 major Chinese cities. Altogether, they suffered over 3,000 days with excessive air pollutants, which will result in a drop of 2.4 percentage points this year in the proportion of days with fairly good air quality in major Chinese cities.

"The sandstorms from Mongolia contribute 1.5 percentage points to the drop, or 62.5 percent," he noted.