The impacts of fertilizer manufacturing on groundwater in South Africa

[摘要] English: As a result of the fertilizer industry's rapid growth, and the increasing global awareness concerningenvironmental issues, fertilizer production facilities have come under growing pressure to comply withever more stringent environmental regulations.There are numerous contaminants associated with the fertilizer industry. These may be released intothe environment through dusts, fumes, air emissions, liquid pollutants, or solid wastes. Some of thesecontaminants pose serious potential health and environmental risks.Groundwater is one of the aspects of the environment heavily effected by the fertilizer industry, and theaim of this study is to provide more clarity on the extent of the pollution caused by the fertilizer industryon the quality of groundwater.The site investigated is located in the industrial area of Potchefstroom, South Africa, and includesSasol Nitro Potchefstroom (SNP), the Kynoch Fertilizer Production Facility (KFPF), and thesurrounding area. SNP is a hot and cold blend liquid fertilizer plant, and KFPF manufactured fertilizerson a full scale from 1967 until mid 2006. An in-depth investigation was conducted on the SNP site bythe researcher, and data from the KFPF site were provided by SRK Consulting who carried out a studythere in 2007.The predominant contaminants associated with the fertilizer industry, also found in significantconcentrations the investigated area, are; nitrate (NO3), ammonium (NH4), phosphate (PO4), sulphate(SO4), fluoride compounds (F), chloride (Cl), cadmium (Cd), and zinc (Zn). Various other heavy metalsand radionuclides posing potential health and environmental risks may be released into theenvironment during the processing of phosphate rock; the types and quantities of which depend on thecontent of the phosphate rock.In general, NO3 (the most predominant contaminant found throughout the site), Ca, Mg, Cl, and Mn arefound predominantly in solution in the groundwater (i.e., not adsorbed to soil/rock) in the saturatedzone, except where there is loading from the surface within the bounds of SNP, which means that theyare present in the unsaturated zone as well and leach down to the saturated zone. SO4 and K werefound in little more concentrations in solution than in soil samples (in the saturated zone), but in alesser contrast than for example, NO3 and Ca. Zn and F were found predominantly in soil samples,and primarily in the upper layer of soil. PO4 was almost exclusively found in the upper layer of soil, aswell as NH4, but to a lesser extent.The general distribution of contaminants on site is attributed to their respective solubilitycharacteristics and their tendency to be adsorbed by soil/rock.Many of the contaminants show a consistent peaking at a depth of ca. 6m. This may be attributed tothe fact that pH levels are mildly acidic within the first few meters of soil, after which it increases rapidlyto approximately neutral values throughout the depth of the site. Contaminants' solubility that are pHdependant (lower pH increases solubility) would hence dissolve and leach through the first layer ofsoil/rock and precipitate where pH values increase.Significant chromium (Cr) concentrations were found in all the water samples taken from the boreholeson the eastern side of the site, ranging between 0.4 �?1.925mg/l. The main source of chromium wasfound to be the site on the southern boundary of the SNP plant, which was the location of a tannery inthe past.Due to the evidence of the effectiveness of plants reducing contaminant concentrations in the northeasterncorner of the site, phytoremediation is recommended as a viable option to rehabilitate thearea.

[发布机构] University of the Free State