Key strategies for managing acid sulphate soil (ASS) problems on the southeastern coast of New South Wales, Australia

摘要

The acidification of Australian coastal waterways as a result of the oxidation of acid sulphate soilrn(ASS) containing appreciable quantities of sulphidic material (e.g. pyrite) has well recognisedrnenvironmental, economic and social effects including the loss of fish, biodiversity and agriculturalrnproductivity as well as the corrosion of concrete and steel infrastructure by acidic drainage. Largescalernartificial drainage and one-way floodgates in low-lying coastal floodplains has lowered therngroundwater table, thus enhancing pyritic oxidation and increasing the distribution, magnitude andrnfrequency of acid generation and release of toxic metals such as aluminium (Al~(3+)) and iron (total Fe)rnfrom ASS. Engineering strategies implemented on the Shoalhaven Floodplain, southeast New SouthrnWales, Australia have been designed to remediate ASS. These include: (1) fixed-level v-notch weirs,rnwhich raise the groundwater table above the pyritic layer and reduce the rate of discharge of acidicrnproducts from the groundwater into the drains; (2) modified two-way floodgates, which allow for tidalrnbuffering of acidic drainage; (3) a subsurface alkaline horizontal impermeable lime-fly ash barrier,rnwhich prevents pyrite oxidation and neutralises acidic groundwater and (4) an alkaline permeablernreactive barrier (PRB) using recycled materials, which significantly increases groundwater pH andrnreduces Al and Fe concentrations within and down-gradient of the PRB. A critical review of each ofrnthese strategies will outline their role in remediating ASS and their respective benefits and limitations.