tone or lime are used to neutralize some acidified lakes and surrounding soil—the only cleanup approach now being used. However, this expensive and temporary remedy usually must be repeated annually. Also, it can kill some types of plankton and aquatic plants and can harm wetland plants that need acidic water. And it is difficult to know how much lime to put where (in the water or at selected locations on the ground). In 2002, researchers in England found that adding a small amount of phosphate fertilizer can neutralize excess acidity in a lake. The effectiveness of this approach is being evaluated.