Toxic emissions produced during operation can be either gaseous (H2S, CH4, CO2) and result from degassing of the produced fluids with high gas content or it can also be in liquid and solid form (e.g. radioactive water or deposit materials or heavy metals). The nature of the toxic emission depends on the content of the geothermal fluid and can vary from place to place
More information is available on the project deliverable (link), or navigate on the online version.