I think in industry terms you're describing a dump. Landfills have liner systems on the sides and bottom, sumps to collect and dispose of trash juice, gas collectors, they're compacted, netted, covered daily to prevent trash from blowing away, then capped and sealed with clay when full, and (in the US) required to be monitored for 30 years for environmental problems and to ensure the decomposition is going as expected.

The microplastics in your air and water probably aren't coming from landfills, in fact the solution to that is very likely to be more landfills. Those plastics come from coastal countries lacking good waste management who dump plastic into rivers and oceans, and the solution is painfully boring— municipal waste management.