Leukocyte Esterase. Leukocyte esterase is an enzyme present in most white blood cells (WBCs). A few white blood cells are normally present in urine and usually give a negative chemical test result. When the number of WBCs in urine increases significantly, this screening test will become positive.
Land subsidence occurs when large amounts of groundwater have been withdrawn from certain types of rocks, such as fine-grained sediments. The rock compacts because the water is partly responsible for holding the ground up. When the water is withdrawn, the rocks falls in on itself.
Upwelling occurs when winds blowing across the ocean surface push water away from an area and subsurface water rises up to replace the diverging surface water. Upwelling occurs in the open ocean and along coastlines. The reverse process, called downwelling, also occurs when wind causes surface water to build up along a coastline. The surface water eventually sinks toward the bottom. Subsurface water that rises to the surface as a result of upwelling is typically colder, rich in nutrients, and biologically productive.