The most important global sink process for aerosols is

Correct option is D

Introduction

Aerosols are tiny solid particles or liquid droplets suspended in the atmosphere, ranging in size from a few nanometers to tens of micrometers.
A "sink" refers to the natural processes that remove these particles from the atmosphere, maintaining a balance between emissions and removal.
These removal processes are crucial for determining the atmospheric lifetime of aerosols and their subsequent impact on climate and human health.

Information Booster

Wet deposition is considered the most significant global sink for atmospheric aerosols, accounting for the removal of approximately 80% to 90% of the total aerosol mass.

It involves the scavenging of particles by precipitation (rain, snow, or fog) and their subsequent delivery to the Earth's surface.

Because clouds and precipitation occur throughout the troposphere, wet deposition effectively removes aerosols from various altitudes, making it the dominant cleansing mechanism on a global scale.
Wet deposition consists of two main mechanisms: "in-cloud scavenging" (rain-out), where particles act as cloud condensation nuclei, and "below-cloud scavenging" (wash-out), where falling raindrops collide with particles.
It is the primary process responsible for the removal of fine particles ($PM_{2.5}$) which are otherwise difficult to remove by gravity.
This process significantly influences the residence time of aerosols, which typically ranges from a few days to a week in the lower atmosphere.
Wet deposition helps in the cycling of nutrients and pollutants from the atmosphere to terrestrial and aquatic ecosystems.
The efficiency of this sink depends heavily on regional precipitation patterns and the hygroscopic (water-attracting) nature of the aerosol particles.

Additional Information

Interception, occurs when a particle follows a gas streamline but comes close enough to a surface (like a leaf or fiber) that its physical size causes it to touch and stick to the surface; it is a localized dry deposition mechanism rather than a global sink.
Sedimentation,also known as gravitational settling, is the process where particles fall due to gravity; while important for very large/coarse particles ($>10 \mu m$), it is inefficient for the vast majority of atmospheric aerosol mass which consists of smaller particles.
Impaction, happens when a particle’s inertia prevents it from following a curved streamline around an obstacle, causing it to strike the object; like interception, this is a dry deposition process that is primarily effective near the ground or in industrial filtration, not as the dominant global sink.