you should see mine...
basically that's one good reason to have a snorkel (contrary to the popular opinion that it is used for water wading). Sand will always be there. And at the bottom of your oil pan too, which shows that the fine sand actually gets into the engine causing slow but visible damage to bearings. The only way to reduce that is to remember to change your air filter (cleaning alone is also good, but that does not mean you can keep the air filter for 10kkm - not in these conditions!), clean your intake after heavy drives and don't follow regular 15kkm oil change, keep it as short as you can: 6-7kkm for those who run extreme drives is a must. And don't even think about any sport or cone filters...