title: Environmental Assessment of the Effects of Leachate Irrigation and Seepage from the Paokahu Landfill, Gisborne, New Zealand.

authors: Joblin, Mark Hugh

subjects: Landfill

abstract: Paokahu landfill operated near Gisborne from 1977 to 2002. About 1 million cubic metres of mixed domestic and industrial (predominantly food processing) wastes were disposed of at the site.  The Paokahu landfill is located on the Poverty Bay Flats on low lying flat ground, which was originally the base of a tidal lagoon.  A 300m wide band of costal dunes separates the landfill from the Poverty Bay coast.  The landfill covers an area of approximately 20 Ha and is unlined but fully capped.  Leachate is collected in a cut-off drain which surrounds three quarters of the landfill.  Disposal of the leachate is by spray irrigation onto the landfill cap with 13,000 - 15,000 m3 of leachate irrigated annually.  The site is currently used for grazing sheep. 

The overall aim of this study was to improve our understanding of the effect that Paokahu landfill is having on the environment and to determine if the current management practices are sustainable.  Specific objectives were to collate and review all the groundwater and leachate monitoring data held by Gisborne District Council to determine if the landfill was affecting the local groundwater and to investigate the effect of leachate irrigation on the landfill cap's soil and vegetation.

The groundwater monitoring data showed the local groundwater was generally affected by salt water intrusions giving the groundwater high anion and cation concentrations.   There was no evidence of a leachate plume originating from the landfill and no conclusive evidence of leachate contamination in any of the groundwater monitoring bores. 

The leachate had a high electrical conductivity (mean = 9350  Scm-1) and high soluble salts content (mean values, Na = 845 gm-3, K= 496 gm-3, Ca = 240 gm-3, Mg = 127 gm-3, Cl =1346 gm-3).  Heavy metals were present in low concentrations and Semi Volatile Organic Compounds were no longer present in the leachate.  Cation and anion concentrations were generally higher in the groundwater than in the leachate.  The main risk to groundwater quality from leachate contamination was from ammonical nitrogen and nitrate.

The leachate irrigation had caused an increase in soil cation concentrations particularly Na in the landfill cap.  However, the soil Exchangeable Sodium Percentage of 1.5 - 2.9, leachate Sodium Adsorption Ratio (6.5) and Electrical Conductivity of (4317  S cm-1) and silty soil material of the landfill cap indicated that soil swelling and dispersion was unlikely to occur in irrigated areas of the landfill cap.  Dispersion index testing supported this conclusion with no significant increase in aggregate dispersion under the irrigated areas of the landfill compared to the non-irrigated areas.  Soil metal concentrations were low and there was no significant difference in soil heavy metal concentrations between the irrigated and non-irrigated areas of the landfill cap.  Leachate Mn concentrations (mean = 1.39 g m-3) were high enough to be potentially toxic to plants, but the soil pH (7.4) and Ca (46.7 me/100g) content mean that Mn toxicity is unlikely to occur.  Leachate irrigation appears sustainable under current conditions.

text: Environmental Assessment of the Effects of Leachate Irrigation and Seepage from the Paokahu Landfill, Gisborne, New Zealand. Paokahu landfill operated near Gisborne from 1977 to 2002. About 1 million cubic metres of mixed domestic and industrial (predominantly food processing) wastes were disposed of at the site.  The Paokahu landfill is located on the Poverty Bay Flats on low lying flat ground, which was originally the base of a tidal lagoon.  A 300m wide band of costal dunes separates the landfill from the Poverty Bay coast.  The landfill covers an area of approximately 20 Ha and is unlined but fully capped.  Leachate is collected in a cut-off drain which surrounds three quarters of the landfill.  Disposal of the leachate is by spray irrigation onto the landfill cap with 13,000 - 15,000 m3 of leachate irrigated annually.  The site is currently used for grazing sheep. 

The overall aim of this study was to improve our understanding of the effect that Paokahu landfill is having on the environment and to determine if the current management practices are sustainable.  Specific objectives were to collate and review all the groundwater and leachate monitoring data held by Gisborne District Council to determine if the landfill was affecting the local groundwater and to investigate the effect of leachate irrigation on the landfill cap's soil and vegetation.

The groundwater monitoring data showed the local groundwater was generally affected by salt water intrusions giving the groundwater high anion and cation concentrations.   There was no evidence of a leachate plume originating from the landfill and no conclusive evidence of leachate contamination in any of the groundwater monitoring bores. 

The leachate had a high electrical conductivity (mean = 9350  Scm-1) and high soluble salts content (mean values, Na = 845 gm-3, K= 496 gm-3, Ca = 240 gm-3, Mg = 127 gm-3, Cl =1346 gm-3).  Heavy metals were present in low concentrations and Semi Volatile Organic Compounds were no longer present in the leachate.  Cation and anion concentrations were generally higher in the groundwater than in the leachate.  The main risk to groundwater quality from leachate contamination was from ammonical nitrogen and nitrate.

The leachate irrigation had caused an increase in soil cation concentrations particularly Na in the landfill cap.  However, the soil Exchangeable Sodium Percentage of 1.5 - 2.9, leachate Sodium Adsorption Ratio (6.5) and Electrical Conductivity of (4317  S cm-1) and silty soil material of the landfill cap indicated that soil swelling and dispersion was unlikely to occur in irrigated areas of the landfill cap.  Dispersion index testing supported this conclusion with no significant increase in aggregate dispersion under the irrigated areas of the landfill compared to the non-irrigated areas.  Soil metal concentrations were low and there was no significant difference in soil heavy metal concentrations between the irrigated and non-irrigated areas of the landfill cap.  Leachate Mn concentrations (mean = 1.39 g m-3) were high enough to be potentially toxic to plants, but the soil pH (7.4) and Ca (46.7 me/100g) content mean that Mn toxicity is unlikely to occur.  Leachate irrigation appears sustainable under current conditions.

year: 2010

title: Influences of graphical image pairing on product preference

authors: Meng, Xiaosha

abstract: Many advertisements appear to rely on higher-order respondent conditioning to alter preference for a product brand. Given that higher-order conditioning is difficult to achieve, there may be other processes, such as those involved in stimulus equivalence, at work. The current experiment paired six “brand” stimuli with three different types of pictures. Three brands were paired directly with the pictures and the other three paired indirectly, using a stimulus equivalence procedure. The three types of pictures were “negative” (typical consequences of ingesting excessive sugar, such as heart disease, tooth decay, and diabetes), “neutral” (pictures of geometrical shapes) and “positive” pictures (pictures related to health and fitness). This research used a respondent procedure, which is more similar to real marketing methods than operant procedures, as used in previous research in this area. A preference assessment was conducted to evaluate transfer of function from the picture to the brands by investigating whether the pairings influenced participants’ preference for branded soft drinks. The results showed that negative pictures shifted preference more than positive pictures and direct pairing was more effective than an indirect pairing procedure.

text: Influences of graphical image pairing on product preference Many advertisements appear to rely on higher-order respondent conditioning to alter preference for a product brand. Given that higher-order conditioning is difficult to achieve, there may be other processes, such as those involved in stimulus equivalence, at work. The current experiment paired six “brand” stimuli with three different types of pictures. Three brands were paired directly with the pictures and the other three paired indirectly, using a stimulus equivalence procedure. The three types of pictures were “negative” (typical consequences of ingesting excessive sugar, such as heart disease, tooth decay, and diabetes), “neutral” (pictures of geometrical shapes) and “positive” pictures (pictures related to health and fitness). This research used a respondent procedure, which is more similar to real marketing methods than operant procedures, as used in previous research in this area. A preference assessment was conducted to evaluate transfer of function from the picture to the brands by investigating whether the pairings influenced participants’ preference for branded soft drinks. The results showed that negative pictures shifted preference more than positive pictures and direct pairing was more effective than an indirect pairing procedure.

year: 2018

title: Maori & Psychology Research Unit annual report 2006

authors: Rua, Mohi

subjects: Maori and Psychology Research Unit

abstract: Annual report of the Maori and Psychology Research Unit (MPRU) 2006. The unit was established in August of 1997. The unit is designed to provide a catalyst and support network for enhancing research concerning the psychological needs, aspirations, and priorities of Maori people. The MPRU is well situated to draw together skilled and experienced interdisciplinary research groups by networking and establishing working relationships with staff and students within the Faculty of Arts and Social Sciences, the University, and the wider community.

text: Maori & Psychology Research Unit annual report 2006 Annual report of the Maori and Psychology Research Unit (MPRU) 2006. The unit was established in August of 1997. The unit is designed to provide a catalyst and support network for enhancing research concerning the psychological needs, aspirations, and priorities of Maori people. The MPRU is well situated to draw together skilled and experienced interdisciplinary research groups by networking and establishing working relationships with staff and students within the Faculty of Arts and Social Sciences, the University, and the wider community.

year: 2006