title: Contribution of Dissolved Organic Carbon Leaching to the Annual Carbon Budget of a Dairy Farm

authors: Chibnall, Emma Jayne

subjects: Dissolved Organic Carbon

abstract: Soils are the largest terrestrial store of carbon (C) and changes in this store of C can impact on soil quality and atmospheric CO2 concentrations. Research on C budgets at paddock to national scales has focused most attention on the processes of respiration and photosynthesis in determining the net loss or gain of carbon from an ecosystem. However, leaching of dissolved organic carbon (DOC) is a potentially important component of the carbon budget that is rarely measured when developing carbon budgets, and as a consequence, is often estimated or excluded. Much of the literature indicates that while DOC leaching is important, the loss of DOC from the terrestrial ecosystem may only be small. In the vasose zone DOC that is leached may be adsorbed on to soil and stabilised or may be mineralised, effectively preventing it from leaching from the ecosystem.

The objectives of this thesis were to determine if DOC leaching from the soil of a dairy farm was an important contribution to the carbon budget. To measure this, soil leachate was collected from five paddocks using 100 suction cup lysimeters. These were installed within the footprints of two eddy covariance towers on a dairy farm in Waharoa, Waikato, New Zealand. In general samples were bulked over paddocks, with 10 mL of water from each suction cup contributing to the overall bulked sample. Water extracted from the suction cups was analysed for DOC, total nitrogen, and nitrate. DOC concentration measurements were coupled to the volume of water draining through the soil. The volume of drainage was obtained from a water balance model using measurements of evaporation and precipitation. Leaching from the soil started in mid-May continuing through till mid-November. The total amount of water draining through the soil for the year was calculated to be 990 mm, with a mean concentration of 4.5 ± 0.8 mg L-1 (mean ± SE). The mass of DOC leached was 38 ± 4 kg C ha-1 yr-1 (mean ± SE). The concentration of DOC showed no monthly variation, while the mass of DOC showed a strong seasonal trend, with the greatest mass of DOC leaching during the wet winter period. Ultimately the main driver of DOC leaching at this site was the volume of water draining through the soil, because DOC concentration changed very little. 

In order to understand the suite of processes that influence the fate of DOC the subsoil, internal cycling process including mineralisation and sorption of DOC were investigated in the laboratory. Results showed that DOC leached to a depth of 0.65 m could be mineralised by soil microbes lower in the profile, converting it to CO2. The total C respired over a week (12.81 µg CO2-C-1 g soil-1) was 11 times greater than the C added (1.18 µg C-1 g soil-1). In a repeat of the same study the amount of CO2 respired was 25 times greater than the addition of DOC. Additionally sorption experiments indicated that the concentration of DOC lost to the groundwater would be less than the concentration of DOC measured at 0.65 m. Soil water solution with a concentration of 7 mg L-1 DOC mixed with subsoil had a 50% reduction in concentration when shaken for four hours with Te Puninga soil. Similar results were found in the Piarere soil with a 34% reduction in DOC concentration. In contrast when both soils were shaken with DOC (4 mg L-1) in a second experiment, there was a small amount of net desorption. There was potential for the soils at this site to reduce the concentration of DOC leached from 0.65 m, through adsorption of DOC onto the soil. Subsequently sorption would have caused a reduction in the DOC mass lost. While results from laboratory studies were variable it was clear that both sorption and mineralisation in subsoils will moderate leaching losses of DOC to groundwater.

In the context of a paddock scale C budget, where the atmospheric exchange of C through respiration and photosynthesis was about -880 kg C ha-1yr-1, leaching of 38 kg C ha-1 yr-1, represents 4.5% of the total exchange. Compared to the net ecosystem carbon budget, which included farm inputs and outputs, of a similar intensive grazed system, DOC leaching is equal to 3-15% of the total. However as DOC leaching at 0.65 m does not accurately represent a leaching loss from the system, as sorption and mineralisation can further alter the mass leached, the contribution of DOC loss through leaching to the carbon budget is comparably small and does not represent a significant component of the C budget at this site.

text: Contribution of Dissolved Organic Carbon Leaching to the Annual Carbon Budget of a Dairy Farm Soils are the largest terrestrial store of carbon (C) and changes in this store of C can impact on soil quality and atmospheric CO2 concentrations. Research on C budgets at paddock to national scales has focused most attention on the processes of respiration and photosynthesis in determining the net loss or gain of carbon from an ecosystem. However, leaching of dissolved organic carbon (DOC) is a potentially important component of the carbon budget that is rarely measured when developing carbon budgets, and as a consequence, is often estimated or excluded. Much of the literature indicates that while DOC leaching is important, the loss of DOC from the terrestrial ecosystem may only be small. In the vasose zone DOC that is leached may be adsorbed on to soil and stabilised or may be mineralised, effectively preventing it from leaching from the ecosystem.

The objectives of this thesis were to determine if DOC leaching from the soil of a dairy farm was an important contribution to the carbon budget. To measure this, soil leachate was collected from five paddocks using 100 suction cup lysimeters. These were installed within the footprints of two eddy covariance towers on a dairy farm in Waharoa, Waikato, New Zealand. In general samples were bulked over paddocks, with 10 mL of water from each suction cup contributing to the overall bulked sample. Water extracted from the suction cups was analysed for DOC, total nitrogen, and nitrate. DOC concentration measurements were coupled to the volume of water draining through the soil. The volume of drainage was obtained from a water balance model using measurements of evaporation and precipitation. Leaching from the soil started in mid-May continuing through till mid-November. The total amount of water draining through the soil for the year was calculated to be 990 mm, with a mean concentration of 4.5 ± 0.8 mg L-1 (mean ± SE). The mass of DOC leached was 38 ± 4 kg C ha-1 yr-1 (mean ± SE). The concentration of DOC showed no monthly variation, while the mass of DOC showed a strong seasonal trend, with the greatest mass of DOC leaching during the wet winter period. Ultimately the main driver of DOC leaching at this site was the volume of water draining through the soil, because DOC concentration changed very little. 

In order to understand the suite of processes that influence the fate of DOC the subsoil, internal cycling process including mineralisation and sorption of DOC were investigated in the laboratory. Results showed that DOC leached to a depth of 0.65 m could be mineralised by soil microbes lower in the profile, converting it to CO2. The total C respired over a week (12.81 µg CO2-C-1 g soil-1) was 11 times greater than the C added (1.18 µg C-1 g soil-1). In a repeat of the same study the amount of CO2 respired was 25 times greater than the addition of DOC. Additionally sorption experiments indicated that the concentration of DOC lost to the groundwater would be less than the concentration of DOC measured at 0.65 m. Soil water solution with a concentration of 7 mg L-1 DOC mixed with subsoil had a 50% reduction in concentration when shaken for four hours with Te Puninga soil. Similar results were found in the Piarere soil with a 34% reduction in DOC concentration. In contrast when both soils were shaken with DOC (4 mg L-1) in a second experiment, there was a small amount of net desorption. There was potential for the soils at this site to reduce the concentration of DOC leached from 0.65 m, through adsorption of DOC onto the soil. Subsequently sorption would have caused a reduction in the DOC mass lost. While results from laboratory studies were variable it was clear that both sorption and mineralisation in subsoils will moderate leaching losses of DOC to groundwater.

In the context of a paddock scale C budget, where the atmospheric exchange of C through respiration and photosynthesis was about -880 kg C ha-1yr-1, leaching of 38 kg C ha-1 yr-1, represents 4.5% of the total exchange. Compared to the net ecosystem carbon budget, which included farm inputs and outputs, of a similar intensive grazed system, DOC leaching is equal to 3-15% of the total. However as DOC leaching at 0.65 m does not accurately represent a leaching loss from the system, as sorption and mineralisation can further alter the mass leached, the contribution of DOC loss through leaching to the carbon budget is comparably small and does not represent a significant component of the C budget at this site.

year: 2013

title: Data on coding association rules from an inpatient administrative health data coded by International classification of disease - 10th revision (ICD-10) codes

authors: Peng, Mingkai

subjects: computer science

abstract: Data presented in this article relates to the research article entitled “Exploration of association rule mining for coding consistency and completeness assessment in inpatient administrative health data” (Peng et al. [1]) in preparation). We provided a set of ICD-10 coding association rules in the age group of 55 to 65. The rules were extracted from an inpatient administrative health data at five acute care hospitals in Alberta, Canada, using association rule mining. Thresholds of support and confidence for the association rules mining process were set at 0.19% and 50% respectively. The data set contains 426 rules, in which 86 rules are not nested. Data are provided in the supplementary material. The presented coding association rules provide a reference for future researches on the use of association rule mining for data quality assessment.

text: Data on coding association rules from an inpatient administrative health data coded by International classification of disease - 10th revision (ICD-10) codes Data presented in this article relates to the research article entitled “Exploration of association rule mining for coding consistency and completeness assessment in inpatient administrative health data” (Peng et al. [1]) in preparation). We provided a set of ICD-10 coding association rules in the age group of 55 to 65. The rules were extracted from an inpatient administrative health data at five acute care hospitals in Alberta, Canada, using association rule mining. Thresholds of support and confidence for the association rules mining process were set at 0.19% and 50% respectively. The data set contains 426 rules, in which 86 rules are not nested. Data are provided in the supplementary material. The presented coding association rules provide a reference for future researches on the use of association rule mining for data quality assessment.

year: 2018

title: “This is not a riot, it is a protest”: A discourse analysis of prison violence in New Zealand news media

authors: Membery, Liam

subjects: Prison Violence

abstract: This thesis examines the discourses of prison violence in the New Zealand news media. Prison violence is a pressing social issue that harms those involved and has permeating consequences for the institution. Prison riots, specifically, involve serious instances of disorder and violence that incur physical, psychological, social and economic harm. Despite prisons being private institutions, prison riots are public events that amass large social responses through news media coverage. The public often use news media to co-construct their perceptions of social phenomena, and policymakers use both public opinion and the news media to guide their decisions when shaping policy. Subsequently, the ways in which the news media discursively construct prison riots will have direct consequences for public attitudes and policy relating to prison violence, a phenomenon that exists outside of the public eye. However, there is currently no research that has examined discourses of prison violence and, further, what the consequences of these discourses may be. Therefore, using a Foucauldian approach to discourse analysis, this study examined the discourses in the news media representations of the large-scale prison violence at the Spring Hill Corrections Facility (2013) and Waikeria Prison (2020-2021). The results uncovered three discourses: the riot discourse, the gang discourse, and the protest discourse. The riot discourse was identified as dominant and constructed prison violence as an individualised issue perpetrated by inherently violent prisoners. The gang discourse worked in conjunction with the riot discourse, constructing prison violence as an individualised issue perpetrated by gang members. The protest discourse was identified as a counter-discourse and constructed the unrest at both facilities as protests against living conditions and inhumane treatment. Each discourse has consequences for public attitudes and in turn, penal policy and practice.

text: “This is not a riot, it is a protest”: A discourse analysis of prison violence in New Zealand news media This thesis examines the discourses of prison violence in the New Zealand news media. Prison violence is a pressing social issue that harms those involved and has permeating consequences for the institution. Prison riots, specifically, involve serious instances of disorder and violence that incur physical, psychological, social and economic harm. Despite prisons being private institutions, prison riots are public events that amass large social responses through news media coverage. The public often use news media to co-construct their perceptions of social phenomena, and policymakers use both public opinion and the news media to guide their decisions when shaping policy. Subsequently, the ways in which the news media discursively construct prison riots will have direct consequences for public attitudes and policy relating to prison violence, a phenomenon that exists outside of the public eye. However, there is currently no research that has examined discourses of prison violence and, further, what the consequences of these discourses may be. Therefore, using a Foucauldian approach to discourse analysis, this study examined the discourses in the news media representations of the large-scale prison violence at the Spring Hill Corrections Facility (2013) and Waikeria Prison (2020-2021). The results uncovered three discourses: the riot discourse, the gang discourse, and the protest discourse. The riot discourse was identified as dominant and constructed prison violence as an individualised issue perpetrated by inherently violent prisoners. The gang discourse worked in conjunction with the riot discourse, constructing prison violence as an individualised issue perpetrated by gang members. The protest discourse was identified as a counter-discourse and constructed the unrest at both facilities as protests against living conditions and inhumane treatment. Each discourse has consequences for public attitudes and in turn, penal policy and practice.

year: 2022