This paper reviews the effects of wastewater sodium on soil physical properties, particularly wit... more This paper reviews the effects of wastewater sodium on soil physical properties, particularly with respect to irrigation systems. Fundamental sodicity concepts are examined including (i) sodicity definitions, (ii) the effects of sodium on soil properties, (iii) a discussion of factors that impede the infiltration rate and hydraulic conductivity, (iv) the changes that occur in ionic strength of percolating water in soil, and (v) consideration of the wastewater and soil constituents that modify the effective sodium adsorption ratio. Importantly, the ability for soils to assimilate wastewater over time changes, but these changes are not often considered prior to the planning of such irrigation systems, or after the irrigation systems are operating. The general lack of understanding of sodicity is in part due to the considerable variation in sodicity definitions. Exchangeable sodium percentage (ESP) values that are reported to pose a sodicity problem vary around the world due to the different mineralogy of the soils investigated, but variations in threshold ESP values have also been caused by a lack of consideration of the solution electrolyte concentration when determining ESP. In practice, the effects of sodicity may be evident in soils that are well under reported threshold values. When the effects of sodicity are identified, the landholder at least has the opportunity to implement remediation practices. However, more often than not, the effects of sodium from irrigation water are latent, leading to considerable problems following the cessation of effluent irrigation and changed land use.
Soil, soil water and overland flow were measured on border-check irrigation bays that had receive... more Soil, soil water and overland flow were measured on border-check irrigation bays that had received various levels of soil disturbance (i.e. cultivation) aimed at reducing potential P mobilisation from surface soil (0-20 mm) over a four year period. In general, increasing levels of soil disturbance lowered surface soil Olsen P, Colwell P, Organic P and Calcium Chloride Extractable P although the strength of the relationships diminished with time. Increasing levels of soil disturbance also lowered soil water Dissolved Reactive P (DRP) and Total Dissolved P (TDP). However, these effects did not translate to overland flow. In the first year there was an apparent reduction in overland flow DRP, TDP and Total P with increasing soil disturbance (P=0.041, P=0.012, P=0.025) but that trend dissipated quickly with time (P=0.05). There was no such trend in subsequent years. These experiments were undertaken on commercial farms. It would appear that while cultivation lessened background or ‘syst...
Dairy factory wastewaters are increasingly being considered a valuable resource. However, these w... more Dairy factory wastewaters are increasingly being considered a valuable resource. However, these waters may also contain contaminants, natural or artificial, that may adversely affect the land to which they are applied. This review investigates dairy wastewaters, factors affecting their composition, some probable effects on land and compounds that may be used to trace the migration of pollutants. Dairy factory wastewaters differ depending on the types of products made by the factory and the treatment afforded wastewaters. In addition to milk and milk by-products, dairy factory wastewaters contain cleaning chemicals that contribute to the salt load, and synthetic compounds. From the limited studies where the effects on dairy processing wastewaters on land have been measured, the consensus of the literature results acknowledges the utility to agriculture can be highly variable and depends on the land to which it was applied and wastewater characteristics including concentrations of phosphorus, nitrogen, carbon and sodium. Excessive applications of nutrients such as nitrogen and phosphorus have resulted in runoff to nearby watercourses. Even fewer studies have investigated the use of organic marker compounds in the dairy industry. Lipids, terpenes and sterols found in the plants consumed by livestock would be useful for identifying pollutants from the dairy industry. However, a library of biological marker compounds and their likely sources is needed before such a technology could be applied more widely. The latest account of water use in Australia (2004-05) found that the agricultural industry used approximately 65% of this resource [3]. The dairy industry is Australia's third largest rural industry supplying 11% of the world dairy trade and directly employing approximately 40, 000 people [4]. Australia's 1.7 million cows produce more than 9, 200 ML of milk annually that is processed into a range of valueadded products including whole milk, milk powder, butter and cheese [4]. These processing facilities are commonly located in regional areas close to their suppliers, consuming on average 386 ML of potable water per annum (p.a.) and producing 452 ML p.a. of wastewater [5]. The variability in water use between processing facilities would suggest that improved in-factory water use efficiency may be one way to lessen the demand on domestic supplies [5]. However, wastewaters are themselves a resource that can be used to
Nutrient exports from agriculture are an important environmental issue in many countries. In some... more Nutrient exports from agriculture are an important environmental issue in many countries. In some production systems phosphorus (P) and nitrogen (N) accumulate at or near the soil surface and cultivation is one option for addressing the legacies of previous nutrient applications. This study aimed to compare the effects of cultivation (mouldboard ploughing), pasture type (ryegrass or ryegrass-clover) and P fertiliser application rate (10, 35 or 100 kg P/ha per annum) on P and N in soil and soil water from dairy pastures over a three year period. The results are generally consistent with inversion of organic matter and P rich surface soil (i.e. 0-140 mm). Cultivation lowered surface soil (0-20 mm) P and N concentrations. Surface soil P concentrations also increased with increasing P fertiliser rate but organic matter and P buffering did not. The effects of vegetation were more equivocal. Ploughing lowered most P and N species in surface soil water. The concentrations of P in soil water increased with increasing fertiliser rates as did ammonia concentrations where pastures included clovers. Analyses of trends with time suggests that, for pasture re-establishment, cultivation reduced the risk of N exports through surface pathways. Moreover, analyses of P export risk measured as the dissolved reactive P concentration in surface soil water (0-20 mm) suggests that where there is no predisposition to erosion, mouldboard ploughing not only reduces the risks of P exports, but that effect is likely to be more enduring where paddocks are in positive P balance. It follows that the use of cultivation as part of pasture renovation activities may reduce catchment-scale P exports, particularly in critical source areas where the risks of erosion and subsurface exports of N are low. 2014 Elsevier B.V. All rights reserved.
Clean wastewater streams from a milk processing dairy factory are reused for irrigation of a near... more Clean wastewater streams from a milk processing dairy factory are reused for irrigation of a nearby recreation oval in SouthEastern Australia. The wastewaters and drainage from both irrigation and rainfall events were analysed for general wastewater constituents and trace level, semi-volatile organic compounds. Samples were pre-concentrated using SPE cartridges, derivatised and analysed using GC-MS. Initially, phenol and nitrogen containing compounds that may adversely affect receiving waters were investigated. These compounds could originate from the wastewaters, irrigation infrastructure or the soil itself. The results tentatively suggest that there are few compounds in either the wastewaters or drainage that are of concern for receiving waters. Importantly there appear to be a range of compounds that originate from the soil.
Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affectin... more Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affecting water resources worldwide. The effects of soil disturbance on P exports have not been widely reviewed. In February 2004, four established and four recently laser ...
Organic phosphorus (P) in grazed pastures/grasslands could sustain production systems that histor... more Organic phosphorus (P) in grazed pastures/grasslands could sustain production systems that historically relied on inorganic P fertiliser. Interactions between inorganic P, plants and soils have been studied extensively. However, less is known about the transformation of organic P to inorganic orthophosphate. This paper investigates what is known about organic P in pasture/grassland soils used for agriculture, as well as the research needed to utilise organic P for sustainable plant production. Organic P comprises N50% of total soil P in agricultural systems depending on location, soil type and land use. Organic P hydrolysis and release of orthophosphate by phosphatase enzymatic activity is affected by a range of factors including: (a) the chemical nature of the organic P and its ability to interact with the soil matrix; (b) microorganisms that facilitate mineralisation; (c) soil mineralogy; (d) soil water electrolytes; and (e) soil physicochemical properties. Current biogeochemical knowledge of organic P processing in soil limits our ability to develop management strategies that promote the use of organic P in plant production. Information is particularly needed on the types and sources of organic P in grassland systems and the factors affecting the activity of enzymes that mineralise organic P. Integrated approaches analysing the soil matrix, soil water and soil biology are suggested to address this knowledge gap.
Solid Phase Microextraction (SPME) is an evolving technique invented in the early 1990's. This re... more Solid Phase Microextraction (SPME) is an evolving technique invented in the early 1990's. This review discusses SPME use in the food processing industry, in particular industries that produce their products in liquid form: the milk industry, wine industry, and from processors that use fruits and vegetables to produce juices. Milk and its associated products and wastes were examined with an emphasis on how to overcome the difficult and complex matrices that milk, cheese and whey present for SPME analyses. Despite this, compounds such as aldehydes have been detected in dairy products at only 12 ng/g. Wine is a simpler matrix for SPME analyses with a range of compounds detected from 0.2 mg/L for pesticides up to 5701 mg/L for furans. SPME analyses of fruit and vegetable also detected a range of different compounds with a range from 2 pg/g for pyrazines in grapes all the way up to 1762 mg/L for terpenes in citrus fruits. A study of canned foodstuff that encompassed over 100 different foods found furans at just 0.003 ng/g using SPME technology. The review describes the typical classes of compound found in food products including volatile and semi-volatile aromas, taste molecules, degradation products and contaminants. For all three industries there were similar analytes, whether due to the same input, biosynthetic pathways or contaminants.
Untilled dairy pasture has the potential to release more phosphorus to the environment than a reg... more Untilled dairy pasture has the potential to release more phosphorus to the environment than a regularly ploughed pasture. In this paper we report the initial results of a study comparing the effects of cultivation, phosphorus (P) fertiliser (10, 35, and 100 kg P/ha), and two types of vegetation (ryegrass (Lolium perenne) or ryegrass mixed with clover (Trifolium repens)) in a randomised complete block design. Phosphorus was measured in soil samples taken from depths of 0–20 mm and 0–100 mm. Waters extracted from the 0–20 mm samples were also analysed. In all cases, the P concentrations (Olsen P, Colwell P, Total P, CaCl2extractable P, Dissolved Reactive P, and Total Dissolved P) in the top 20 mm declined with ploughing. Dissolved Reactive P measured in the soil water was 70% less overall in the ploughed plots compared with the unploughed plots, and by 35 weeks after P treatments the decrease in Dissolved Reactive P was 66%. The effects of the fertiliser and pasture treatments were in...
Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in... more Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in our water supplies is often the first step in taking effective remedial action. Organic chemicals can be used to trace the sources of contaminants such as sediments, agrochemicals and nutrients because living organisms, like their wastes and decomposition products, are chemically unique. Using chemical characteristics to trace organic compounds to broad classes (i.e. animal, higher plant or bacteria) is a relatively simple task. For example, detection of a sterol unique to animals would identify animals as being present. Other studies (Leeming et al., 1994) have used faecal sterols to distinguish human and animal faeces in receiving waters. Faecal sterols are source specific due to the intake of the species, metabolic production of sterols and the biota present in the gut. Tracing of organic compounds to species specific sources is more difficult. In this study the organic chemical profiles ('fingerprints') from animal and plant species present in grazing systems were investigated. These chemical profiles were used to identify the source of materials in overland flow from an irrigated dairy farm in the Macalister Irrigation District.
For many years, Australia, like the rest of the world, has suffered the adverse impacts of excess... more For many years, Australia, like the rest of the world, has suffered the adverse impacts of excessive nutrients, particularly phosphorus (P), in our surface waters. Major algal blooms have occurred in all the mainland states and have resulted in both human ...
Field-based toxicity of Cu and Zn to wheat can be modelled using soil properties. Laboratory-base... more Field-based toxicity of Cu and Zn to wheat can be modelled using soil properties. Laboratory-based models should not be used to estimate toxicity in the field.
For essential elements, such as copper (Cu) and zinc (Zn), the bioavailability in biosolids is im... more For essential elements, such as copper (Cu) and zinc (Zn), the bioavailability in biosolids is important from a nutrient release and a potential contamination perspective. Most ecotoxicity studies are done using metal salts and it has been argued that the bioavailability of metals in biosolids can be different to that of metal salts. We compared the bioavailability of Cu and Zn in biosolids with those of metal salts in the same soils using twelve Australian field trials. Three different measures of bioavailability were assessed: soil solution extraction, CaCl 2 extractable fractions and plant uptake. The results showed that bioavailability for Zn was similar in biosolid and salt treatments. For Cu, the results were inconclusive due to strong Cu homeostasis in plants and dissolved organic matter interference in extractable measures. We therefore recommend using isotope dilution methods to assess differences in Cu availability between biosolid and salt treatments.
Environmental Context. Cadmium is a potentially toxic metal that is an unwanted contaminant in ur... more Environmental Context. Cadmium is a potentially toxic metal that is an unwanted contaminant in urban wastewater biosolids, and has the potential to accumulate through the food chain. This study found that the accumulation of cadmium in wheat grain from application of urban biosolids to soils in Australia was less than when cadmium was applied in a water-soluble form. The critical soil cadmium concentration, above which wheat grain would exceed food contaminant limits, could also be simply predicted using soil pH (acidity) and clay content. . One of the pathways for transfer of cadmium (Cd) through the food chain is addition of urban wastewater solids (biosolids) to soil, and many countries have restrictions on biosolid use to minimize crop Cd contamination. The basis of these restrictions often lies in laboratory or glasshouse experimentation of soil–plant transfer of Cd, but these studies are confounded by artefacts from growing crops in controlled laboratory conditions. This study...
Irrigated dairy farms in Australia contain extensive surface drainage networks that transport wat... more Irrigated dairy farms in Australia contain extensive surface drainage networks that transport water and nutrients off the property into community drains, rivers and lake systems. These drainage networks are an important hydro-chemical link between the paddock, farm and catchment scales. This paper presents a preliminary investigation into phosphorus transfer in two drains from an irrigated dairy farm in southeastern Australia. The effects of drain condition (bare earth vs. grazed pasture) and management (weed growth and herbicide application) are investigated over four drainage events. The results show that farm drains (160 m long) significantly alter the phosphorus concentrations in drainage water. The changes in phosphorus concentration and to a lesser extent phosphorus form appear to be affected by the condition as well as the management of the drain. For example the wetting front concentrations increased by 4.4 mg P/l down a pasture-based drain and decreased by 1.2 mg P/l down an earthen drain. Understanding the transport of phosphorus between the paddock and farm boundary appears to be an important step in developing strategies to minimise the potential export of phosphorus from irrigated dairy farms.
Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and co... more Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 • C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 • C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
Assessing pollutant concentrations can be hampered by the complex matrices found in the dairy sup... more Assessing pollutant concentrations can be hampered by the complex matrices found in the dairy supply/processing chain. Matrix effects were examined using solid-phase microextraction (SPME) used to sample haloacetic acid methyl esters (HAAMe) and para-cresol. In general, HAAMe were more difficult to detect with a polydimethylsiloxane fibre than with carboxen-polydimethylsiloxane fibre. Headspace sampling generally provided better detection of HAAMe than direct immersion with the reverse true for para-cresol. For para-cresol, equivalent ratios up to 18.8 were detected. Other compounds detected included sulphides, VOC's, phenols and indoles. For milk samples, most compounds collected by SPME were found using direct immersion.
Phosphorus (P) exports from agricultural land are a problem world-wide and soil tests are often u... more Phosphorus (P) exports from agricultural land are a problem world-wide and soil tests are often used to identify high risk areas. A recent study investigated changes in soil (0–20 mm), soil water and overland flow in 4 recently laser-graded (<1 year) and 4 established (laser-graded >10 years) irrigated pastures in south-eastern Australia before and after 3 years of irrigated dairy production. We use the results from that study to briefly examine the relationships between a series of ‘agronomic’ (Olsen P, Colwell P), environmental (water-extractable P, calcium chloride extractable P, P sorption saturation, and P sorption), and other (total P, organic P) soil P tests. Of the 2 ‘agronomic’ soil P tests, Colwell P explained 91% of the variation in Olsen P, and Colwell P was better correlated with the other soil tests. With the exception of P sorption, all soil P tests explained 57% or more of the total variation in Colwell P, while they explained 61% or less of Olsen P possibly du...
This paper reviews the effects of wastewater sodium on soil physical properties, particularly wit... more This paper reviews the effects of wastewater sodium on soil physical properties, particularly with respect to irrigation systems. Fundamental sodicity concepts are examined including (i) sodicity definitions, (ii) the effects of sodium on soil properties, (iii) a discussion of factors that impede the infiltration rate and hydraulic conductivity, (iv) the changes that occur in ionic strength of percolating water in soil, and (v) consideration of the wastewater and soil constituents that modify the effective sodium adsorption ratio. Importantly, the ability for soils to assimilate wastewater over time changes, but these changes are not often considered prior to the planning of such irrigation systems, or after the irrigation systems are operating. The general lack of understanding of sodicity is in part due to the considerable variation in sodicity definitions. Exchangeable sodium percentage (ESP) values that are reported to pose a sodicity problem vary around the world due to the different mineralogy of the soils investigated, but variations in threshold ESP values have also been caused by a lack of consideration of the solution electrolyte concentration when determining ESP. In practice, the effects of sodicity may be evident in soils that are well under reported threshold values. When the effects of sodicity are identified, the landholder at least has the opportunity to implement remediation practices. However, more often than not, the effects of sodium from irrigation water are latent, leading to considerable problems following the cessation of effluent irrigation and changed land use.
Soil, soil water and overland flow were measured on border-check irrigation bays that had receive... more Soil, soil water and overland flow were measured on border-check irrigation bays that had received various levels of soil disturbance (i.e. cultivation) aimed at reducing potential P mobilisation from surface soil (0-20 mm) over a four year period. In general, increasing levels of soil disturbance lowered surface soil Olsen P, Colwell P, Organic P and Calcium Chloride Extractable P although the strength of the relationships diminished with time. Increasing levels of soil disturbance also lowered soil water Dissolved Reactive P (DRP) and Total Dissolved P (TDP). However, these effects did not translate to overland flow. In the first year there was an apparent reduction in overland flow DRP, TDP and Total P with increasing soil disturbance (P=0.041, P=0.012, P=0.025) but that trend dissipated quickly with time (P=0.05). There was no such trend in subsequent years. These experiments were undertaken on commercial farms. It would appear that while cultivation lessened background or ‘syst...
Dairy factory wastewaters are increasingly being considered a valuable resource. However, these w... more Dairy factory wastewaters are increasingly being considered a valuable resource. However, these waters may also contain contaminants, natural or artificial, that may adversely affect the land to which they are applied. This review investigates dairy wastewaters, factors affecting their composition, some probable effects on land and compounds that may be used to trace the migration of pollutants. Dairy factory wastewaters differ depending on the types of products made by the factory and the treatment afforded wastewaters. In addition to milk and milk by-products, dairy factory wastewaters contain cleaning chemicals that contribute to the salt load, and synthetic compounds. From the limited studies where the effects on dairy processing wastewaters on land have been measured, the consensus of the literature results acknowledges the utility to agriculture can be highly variable and depends on the land to which it was applied and wastewater characteristics including concentrations of phosphorus, nitrogen, carbon and sodium. Excessive applications of nutrients such as nitrogen and phosphorus have resulted in runoff to nearby watercourses. Even fewer studies have investigated the use of organic marker compounds in the dairy industry. Lipids, terpenes and sterols found in the plants consumed by livestock would be useful for identifying pollutants from the dairy industry. However, a library of biological marker compounds and their likely sources is needed before such a technology could be applied more widely. The latest account of water use in Australia (2004-05) found that the agricultural industry used approximately 65% of this resource [3]. The dairy industry is Australia's third largest rural industry supplying 11% of the world dairy trade and directly employing approximately 40, 000 people [4]. Australia's 1.7 million cows produce more than 9, 200 ML of milk annually that is processed into a range of valueadded products including whole milk, milk powder, butter and cheese [4]. These processing facilities are commonly located in regional areas close to their suppliers, consuming on average 386 ML of potable water per annum (p.a.) and producing 452 ML p.a. of wastewater [5]. The variability in water use between processing facilities would suggest that improved in-factory water use efficiency may be one way to lessen the demand on domestic supplies [5]. However, wastewaters are themselves a resource that can be used to
Nutrient exports from agriculture are an important environmental issue in many countries. In some... more Nutrient exports from agriculture are an important environmental issue in many countries. In some production systems phosphorus (P) and nitrogen (N) accumulate at or near the soil surface and cultivation is one option for addressing the legacies of previous nutrient applications. This study aimed to compare the effects of cultivation (mouldboard ploughing), pasture type (ryegrass or ryegrass-clover) and P fertiliser application rate (10, 35 or 100 kg P/ha per annum) on P and N in soil and soil water from dairy pastures over a three year period. The results are generally consistent with inversion of organic matter and P rich surface soil (i.e. 0-140 mm). Cultivation lowered surface soil (0-20 mm) P and N concentrations. Surface soil P concentrations also increased with increasing P fertiliser rate but organic matter and P buffering did not. The effects of vegetation were more equivocal. Ploughing lowered most P and N species in surface soil water. The concentrations of P in soil water increased with increasing fertiliser rates as did ammonia concentrations where pastures included clovers. Analyses of trends with time suggests that, for pasture re-establishment, cultivation reduced the risk of N exports through surface pathways. Moreover, analyses of P export risk measured as the dissolved reactive P concentration in surface soil water (0-20 mm) suggests that where there is no predisposition to erosion, mouldboard ploughing not only reduces the risks of P exports, but that effect is likely to be more enduring where paddocks are in positive P balance. It follows that the use of cultivation as part of pasture renovation activities may reduce catchment-scale P exports, particularly in critical source areas where the risks of erosion and subsurface exports of N are low. 2014 Elsevier B.V. All rights reserved.
Clean wastewater streams from a milk processing dairy factory are reused for irrigation of a near... more Clean wastewater streams from a milk processing dairy factory are reused for irrigation of a nearby recreation oval in SouthEastern Australia. The wastewaters and drainage from both irrigation and rainfall events were analysed for general wastewater constituents and trace level, semi-volatile organic compounds. Samples were pre-concentrated using SPE cartridges, derivatised and analysed using GC-MS. Initially, phenol and nitrogen containing compounds that may adversely affect receiving waters were investigated. These compounds could originate from the wastewaters, irrigation infrastructure or the soil itself. The results tentatively suggest that there are few compounds in either the wastewaters or drainage that are of concern for receiving waters. Importantly there appear to be a range of compounds that originate from the soil.
Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affectin... more Agricultural systems contribute to excessive phosphorus (P) additions that are adversely affecting water resources worldwide. The effects of soil disturbance on P exports have not been widely reviewed. In February 2004, four established and four recently laser ...
Organic phosphorus (P) in grazed pastures/grasslands could sustain production systems that histor... more Organic phosphorus (P) in grazed pastures/grasslands could sustain production systems that historically relied on inorganic P fertiliser. Interactions between inorganic P, plants and soils have been studied extensively. However, less is known about the transformation of organic P to inorganic orthophosphate. This paper investigates what is known about organic P in pasture/grassland soils used for agriculture, as well as the research needed to utilise organic P for sustainable plant production. Organic P comprises N50% of total soil P in agricultural systems depending on location, soil type and land use. Organic P hydrolysis and release of orthophosphate by phosphatase enzymatic activity is affected by a range of factors including: (a) the chemical nature of the organic P and its ability to interact with the soil matrix; (b) microorganisms that facilitate mineralisation; (c) soil mineralogy; (d) soil water electrolytes; and (e) soil physicochemical properties. Current biogeochemical knowledge of organic P processing in soil limits our ability to develop management strategies that promote the use of organic P in plant production. Information is particularly needed on the types and sources of organic P in grassland systems and the factors affecting the activity of enzymes that mineralise organic P. Integrated approaches analysing the soil matrix, soil water and soil biology are suggested to address this knowledge gap.
Solid Phase Microextraction (SPME) is an evolving technique invented in the early 1990's. This re... more Solid Phase Microextraction (SPME) is an evolving technique invented in the early 1990's. This review discusses SPME use in the food processing industry, in particular industries that produce their products in liquid form: the milk industry, wine industry, and from processors that use fruits and vegetables to produce juices. Milk and its associated products and wastes were examined with an emphasis on how to overcome the difficult and complex matrices that milk, cheese and whey present for SPME analyses. Despite this, compounds such as aldehydes have been detected in dairy products at only 12 ng/g. Wine is a simpler matrix for SPME analyses with a range of compounds detected from 0.2 mg/L for pesticides up to 5701 mg/L for furans. SPME analyses of fruit and vegetable also detected a range of different compounds with a range from 2 pg/g for pyrazines in grapes all the way up to 1762 mg/L for terpenes in citrus fruits. A study of canned foodstuff that encompassed over 100 different foods found furans at just 0.003 ng/g using SPME technology. The review describes the typical classes of compound found in food products including volatile and semi-volatile aromas, taste molecules, degradation products and contaminants. For all three industries there were similar analytes, whether due to the same input, biosynthetic pathways or contaminants.
Untilled dairy pasture has the potential to release more phosphorus to the environment than a reg... more Untilled dairy pasture has the potential to release more phosphorus to the environment than a regularly ploughed pasture. In this paper we report the initial results of a study comparing the effects of cultivation, phosphorus (P) fertiliser (10, 35, and 100 kg P/ha), and two types of vegetation (ryegrass (Lolium perenne) or ryegrass mixed with clover (Trifolium repens)) in a randomised complete block design. Phosphorus was measured in soil samples taken from depths of 0–20 mm and 0–100 mm. Waters extracted from the 0–20 mm samples were also analysed. In all cases, the P concentrations (Olsen P, Colwell P, Total P, CaCl2extractable P, Dissolved Reactive P, and Total Dissolved P) in the top 20 mm declined with ploughing. Dissolved Reactive P measured in the soil water was 70% less overall in the ploughed plots compared with the unploughed plots, and by 35 weeks after P treatments the decrease in Dissolved Reactive P was 66%. The effects of the fertiliser and pasture treatments were in...
Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in... more Water pollution is a major environmental problem worldwide. Tracing the source of contaminants in our water supplies is often the first step in taking effective remedial action. Organic chemicals can be used to trace the sources of contaminants such as sediments, agrochemicals and nutrients because living organisms, like their wastes and decomposition products, are chemically unique. Using chemical characteristics to trace organic compounds to broad classes (i.e. animal, higher plant or bacteria) is a relatively simple task. For example, detection of a sterol unique to animals would identify animals as being present. Other studies (Leeming et al., 1994) have used faecal sterols to distinguish human and animal faeces in receiving waters. Faecal sterols are source specific due to the intake of the species, metabolic production of sterols and the biota present in the gut. Tracing of organic compounds to species specific sources is more difficult. In this study the organic chemical profiles ('fingerprints') from animal and plant species present in grazing systems were investigated. These chemical profiles were used to identify the source of materials in overland flow from an irrigated dairy farm in the Macalister Irrigation District.
For many years, Australia, like the rest of the world, has suffered the adverse impacts of excess... more For many years, Australia, like the rest of the world, has suffered the adverse impacts of excessive nutrients, particularly phosphorus (P), in our surface waters. Major algal blooms have occurred in all the mainland states and have resulted in both human ...
Field-based toxicity of Cu and Zn to wheat can be modelled using soil properties. Laboratory-base... more Field-based toxicity of Cu and Zn to wheat can be modelled using soil properties. Laboratory-based models should not be used to estimate toxicity in the field.
For essential elements, such as copper (Cu) and zinc (Zn), the bioavailability in biosolids is im... more For essential elements, such as copper (Cu) and zinc (Zn), the bioavailability in biosolids is important from a nutrient release and a potential contamination perspective. Most ecotoxicity studies are done using metal salts and it has been argued that the bioavailability of metals in biosolids can be different to that of metal salts. We compared the bioavailability of Cu and Zn in biosolids with those of metal salts in the same soils using twelve Australian field trials. Three different measures of bioavailability were assessed: soil solution extraction, CaCl 2 extractable fractions and plant uptake. The results showed that bioavailability for Zn was similar in biosolid and salt treatments. For Cu, the results were inconclusive due to strong Cu homeostasis in plants and dissolved organic matter interference in extractable measures. We therefore recommend using isotope dilution methods to assess differences in Cu availability between biosolid and salt treatments.
Environmental Context. Cadmium is a potentially toxic metal that is an unwanted contaminant in ur... more Environmental Context. Cadmium is a potentially toxic metal that is an unwanted contaminant in urban wastewater biosolids, and has the potential to accumulate through the food chain. This study found that the accumulation of cadmium in wheat grain from application of urban biosolids to soils in Australia was less than when cadmium was applied in a water-soluble form. The critical soil cadmium concentration, above which wheat grain would exceed food contaminant limits, could also be simply predicted using soil pH (acidity) and clay content. . One of the pathways for transfer of cadmium (Cd) through the food chain is addition of urban wastewater solids (biosolids) to soil, and many countries have restrictions on biosolid use to minimize crop Cd contamination. The basis of these restrictions often lies in laboratory or glasshouse experimentation of soil–plant transfer of Cd, but these studies are confounded by artefacts from growing crops in controlled laboratory conditions. This study...
Irrigated dairy farms in Australia contain extensive surface drainage networks that transport wat... more Irrigated dairy farms in Australia contain extensive surface drainage networks that transport water and nutrients off the property into community drains, rivers and lake systems. These drainage networks are an important hydro-chemical link between the paddock, farm and catchment scales. This paper presents a preliminary investigation into phosphorus transfer in two drains from an irrigated dairy farm in southeastern Australia. The effects of drain condition (bare earth vs. grazed pasture) and management (weed growth and herbicide application) are investigated over four drainage events. The results show that farm drains (160 m long) significantly alter the phosphorus concentrations in drainage water. The changes in phosphorus concentration and to a lesser extent phosphorus form appear to be affected by the condition as well as the management of the drain. For example the wetting front concentrations increased by 4.4 mg P/l down a pasture-based drain and decreased by 1.2 mg P/l down an earthen drain. Understanding the transport of phosphorus between the paddock and farm boundary appears to be an important step in developing strategies to minimise the potential export of phosphorus from irrigated dairy farms.
Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and co... more Phosphorus lost in runoff from agricultural land leads to the enrichment of surface waters and contributes to algal blooms. Fertilisers are one source of this P. To compare the water available P of different fertiliser formulations in the laboratory it is necessary to control environmental conditions, temperature, relative humidity and soil water content, prior to simulating rainfall. Two chambers were designed in which relative humidity and soil water content were controlled using salt solutions. An initial design comprising a sealed chamber with three layers of soil samples over a salt bath was found to be inferior to a single layer design. The changes in water content of soil samples were used to test the single layer chamber in a constant temperature environment (15 • C) using a saturated KCl solution (90% relative humidity). Based on the final soil water content of the samples, the spatial variation within the chamber was within tolerable limits. The single layer chamber was used for a simulation experiment comparing the water available P of two commercial fertilisers. Using a saturated resorcinol solution (95% relative humidity) soil samples were equilibrated at 15 • C for 21 days, fertiliser added, and the water available P measured up to 600 h after fertiliser application. The results indicate that the amount of water available P was related to the fertiliser compound and exponentially related to the time since fertiliser application. It was concluded that the single layer chamber is suitable for controlling relative humidity and soil water content in trials such as these where the water available P of fertilisers are being compared.
Assessing pollutant concentrations can be hampered by the complex matrices found in the dairy sup... more Assessing pollutant concentrations can be hampered by the complex matrices found in the dairy supply/processing chain. Matrix effects were examined using solid-phase microextraction (SPME) used to sample haloacetic acid methyl esters (HAAMe) and para-cresol. In general, HAAMe were more difficult to detect with a polydimethylsiloxane fibre than with carboxen-polydimethylsiloxane fibre. Headspace sampling generally provided better detection of HAAMe than direct immersion with the reverse true for para-cresol. For para-cresol, equivalent ratios up to 18.8 were detected. Other compounds detected included sulphides, VOC's, phenols and indoles. For milk samples, most compounds collected by SPME were found using direct immersion.
Phosphorus (P) exports from agricultural land are a problem world-wide and soil tests are often u... more Phosphorus (P) exports from agricultural land are a problem world-wide and soil tests are often used to identify high risk areas. A recent study investigated changes in soil (0–20 mm), soil water and overland flow in 4 recently laser-graded (<1 year) and 4 established (laser-graded >10 years) irrigated pastures in south-eastern Australia before and after 3 years of irrigated dairy production. We use the results from that study to briefly examine the relationships between a series of ‘agronomic’ (Olsen P, Colwell P), environmental (water-extractable P, calcium chloride extractable P, P sorption saturation, and P sorption), and other (total P, organic P) soil P tests. Of the 2 ‘agronomic’ soil P tests, Colwell P explained 91% of the variation in Olsen P, and Colwell P was better correlated with the other soil tests. With the exception of P sorption, all soil P tests explained 57% or more of the total variation in Colwell P, while they explained 61% or less of Olsen P possibly du...
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Papers by David Nash