solutions

• Importance of groundwater

  70% of the earth is covered by water, ground water represents 99% of available freshwater, essential to protect it, in NZ nearly 40% of the community's drinking water supply come from groundwater
• Why soil is important


  Receives large quantities of pollutants, serves many ecosystem functions including growing our food, acts as a filter preventing contamination of groundwater through sorption and degradation
• What can we do about organic pollutants

  Legacy: deal with it through remediation, Present: prevent further/reduce pollution through mitigation, monitoring, find alternatives, Future: predict through risk assessment, regulation
• Traditional remediation approaches


  • Dig and dump (soil excavation and landfill disposal), pump contaminants out of groundwater
• Alternative remediation approaches


  • Take advantage of containment properties, transfer contaminants from one phase to another, promote biodegradation or abiotic degradation
• Alternative/innovative remediation approaches

  • Compost/biopile, soil vapour extraction, reactive barriers, in situ redox manipulation
• PCBs in the Hudson River: 1947-1977 two capacitor manufacturing plants released 590,000 kg PCBs, sediments had 10 ppm (1-2 orders of magnitude > typical), fishing was banned in 1976, many remediation programs since, one of the largest and most complex clean-up projects in US history, 1.5 million m3 of sediments removed through dredging from 2009-2015
• Mitigation, monitoring, find alternatives

  Monitoring: we only find what we look for, what to monitor (sewage, surface water, soil, air, sediments, biota), how (analytical challenges, budget challenges), where and when (high spatial and temporal variations)
• Sewage treatment is controlling the release of chemicals into rivers/sea to remove pathogens, great variability in concentrations and removal of pharmaceuticals like antibiotics in sewage treatment plants in different countries
• Risk assessment and regulation

  Risk = Exposure x Hazard, applied to many substances before they are placed on the market, need to know the sources, what happens and how much is where, how toxic, regulation and restrictions can lower production, use, release and impact
• The situation is much better than 50 years ago, we can see many emerging contaminants we did not see before, our use of novel and unnecessary chemicals tends to increase, good science helps making good decisions, action is needed by scientists, policy makers, industry, consumers