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Declining water quality on the south coast of Western Australia has been linked to current agricultural practices. Riparian buffers were identified as a tool available to farmers and catchment managers to achieve water quality improvements. This study compares 10 m wide regenerating grass and Eucalyptus globulus buffer performance. Surface and subsurface water quality were monitored over a 3-year period. Nutrient and sediment transport were both dominated by subsurface flow, in particular through the B-horizon, and this may seriously limit the surface-runoff-related functions of the riparian buffers. Riparian buffer trapping efficiencies were variable on an event basis and annual basis. The grass buffer reduced total phosphorus, filterable reactive phosphorus, total nitrogen and suspended sediment loads from surface runoff by 50 to 60%. The E. globulus buffer was not as effective, and total load reductions in surface runoff ranged between 10 and 40%. A key difference between the grass and E. globulus buffers was the seasonality of sediment and nutrient transport. Surface runoff, and therefore sediment and nutrient transport, occurred throughout the year in the E. globulus buffer, but only during the winter in the grass buffer. As a consequence of high summer nutrient and sediment concentrations, half the annual loads moving via surface runoff pathways through the E. globulus buffer were transported during intense summer storms. This study demonstrates that grass and E. globulus riparian buffers receiving runoff from pasture under natural rainfall can reduce sediment and nutrient loads from surface runoff. However, in this environment the B-horizon subsurface flow is the dominant flowpath for nutrient transport through the riparian buffers, and this subsurface flow pathway carries contaminant loads at least three times greater than surface runoff. Copyright © 2006 John Wiley & Sons, Ltd.

Rainfall takes many flowpaths to reach a stream, and the success of riparian buffers in water quality management is significantly influenced by riparian hydrology. This paper presents results from hydrometric monitoring of riparian buffer hydrology in a pasture catchment. Runoff processes and riparian flowpaths were investigated on two planar hillslopes with regenerating grass and E. globulus buffers. Surface runoff and subsurface flows (A- and B-horizons) were measured for 3 years using surface runoff collectors, subsurface troughs and piezometers. Water volumes moving through the riparian buffers via the measured flowpaths were ranked B-horizon ≫ surface runoff ≈ A-horizon. Runoff volumes through the B-horizon troughs were an order of magnitude greater than those recorded for the most productive surface runoff plots or the A-horizon troughs. Subsurface runoff and saturation-excess overland flow (SOF) were limited to the winter months, whereas infiltration-excess overland flow (IEOF) can occur all year round during intense storms. Surface runoff was recorded on 33 occasions, mostly during winter (late May–early October), and total annual surface runoff volumes collected by the 20 unconfined (2 m wide) runoff plots varied between > 80 and < 20 m3. Subsurface flow only occurred in winter, and the 6 m wide B-horizon subsurface troughs flowed above 1 l s−1 continuously, whereas the A-horizon troughs flowed infrequently (

Human natural killer (NK) lymphocytes play a central role in immune system defense against viral infection and against the formation of primary tumors. Organotin (OT) pesticides have been used in industrial and agricultural applications, and OT contamination has been reported in water, sediment, and fish. Carbamate pesticides are currently used in agricultural chemicals. Two specific carbamates used in agriculture are ziram and maneb; ziram also is used as an additive in rubber products including latex gloves. In previous studies we demonstrated that at concentrations in the 150–200 nM range, the OTs tributyltin (TBT) and triphenyltin (TPT) were capable of disrupting the function of human NK cells after incubations to as short as 24 h. Previously, we also examined the effects of ziram and maneb at higher concentrations on the cytotoxic function of human NK cells. The current study examined the effects of exposure of up to 6 days to lower concentrations of each of these compounds on the cytotoxic function of NK cells. The OTs were studied at concentrations ranging from 200 to 10 nM; ziram was studied at concentrations of 2.5 μM–125 nM and maneb at concentrations of 10–1 μM. These conditions were studied both in highly purified NK cells and in a mixture of lymphocytes containing both T and NK cells. As little as 25 nM TBT decreased the function of purified NK cells after 24 and 48 h, whereas 10 nM TBT was effective after 6 days. The lowest level of TPT that was effective at 24 h was 50 nM whereas the results after 48 h and 6 days were similar to those seen with TBT. The presence of T lymphocytes diminished the effects of both TBT and TPT on NK cytotoxic function. A concentration of ziram as low as 125 nM produced significant loss of cytotoxic function in highly purified NK cells (65% decrease in function after 6 days). The toxicity of each of the compounds studied increased very significantly with length of exposure. © 2004 Wiley Periodicals, Inc. Environ Toxicol 19: 554–563, 2004

Riparian vegetation can trap sediment and nutrients sourced from hillslopes and reduce stream bank erosion. This study presents results from a 10-year stream monitoring program (1991–2000), in a 6 km2 agricultural catchment near Albany, Western Australia. After 6 years, a 1.7 km stream reach was fenced, planted with eucalyptus species and managed independently from the adjacent paddocks. Streamflow, nutrient and sediment concentration data were collected at the downstream end of the fenced riparian area, so there are data for before and after improved riparian management. Suspended sediment (SS) concentrations fell dramatically following improved riparian management; the median event mean concentration (EMC) dropped from 147 to 9.9 mg l−1. Maximum SS concentrations dropped by an order of magnitude. As a result, sediment exports from the catchment decreased following improved riparian management, from over 100 to less than 10 kg ha−1 yr−1. Observations suggest that this was the result of reduced bank erosion and increased channel stability. Riparian management had limited impact on total phosphorus (TP) concentrations or loads, but contributed to a change in phosphorus (P) form. Before improved riparian management, around half of the P was transported attached to sediment, but after, the median filterable reactive P (FRP) to TP ratio increased to 0.75. In addition, the median FRP EMC increased by 60% and the raw median FRP concentration increased from 0.18 to 0.35 mg l−1. These results suggest that there was a change in the dominant P form, from TP to FRP. Changes in total nitrogen (TN) following improved riparian management were less clear. There were reductions in TN concentrations at high flows, but little change in the loads or EMC. This study demonstrates the benefits of riparian management in reducing stream bank erosion, but suggests that in catchments with sandy, low P sorption soils, there may be limitations on the effectiveness of riparian buffers for reducing P and N exports.

Declining water quality on the south coast of Western Australia has been associated with increasing input of nutrients, particularly phosphorus (P), from diffuse agricultural sources. A survey of surface (0–10 cm) soil properties (ammonium oxalate extractable iron, bicarbonate extractable P and K, pH, organic carbon and salinity) from 7950 sites mostly on agricultural land, along with information on fertiliser practices, land use, soil type, rainfall and time since agricultural development reveals patterns of nutrient status and fertiliser practice, and improved understanding of potential nutrient export hazards. Significant increases in soil bicarbonate extractable P and K have been brought about by continued traditional application of P based fertilisers. Soil organic carbon decreased after clearing, but then increased as soil fertility increased. There has been little change in soil pH or salinity. A significant interaction between time since agricultural development and ammonium oxalate extractable Fe indicated that the rate of change and absolute value of soil bicarbonate extractable P increased as time and ammonium oxalate extractable Fe increased. Soils with low ammonium oxalate extractable Fe (400 mg kg −1 ) reach a maximum soil bicarbonate P more quickly ( 30 yr). Optimum land management should be based around the reducing P leaching through sandy soils with low ammonium oxalate extractable Fe (low P retention), and reducing runoff and erosion from soils with high ammonium oxalate extractable Fe (high P retention) and a long fertiliser history. More than half of the soils tested contained sufficient bicarbonate extractable P (high P status) to forego P applications for at least one year; however, 90% received P applications independently of the soil test information. Two thirds of the high P status soils were deficient in S, whilst 25% were deficient in K. Correcting these nutrient deficiencies would reduce the rate of increase in soil P and reduce the P loss export hazard.

Organochlorine pesticides are used worldwide. To our knowledge there have been no studies dealing with the effects of these agents under in vitro conditions on human natural killer (NK) cell cytotoxic function. NK cells play a central role in immune defense against tumor development and viral infections. Thus, any agent that interferes with the ability of NK cells to lyse their targets could increase the risk of tumor incidence and/or viral infections. In this study, we examined the effects of organochlorine pesticides and some of their breakdown products on the ability of human NK cells to lyse tumor cells. A total of 11 compounds were tested. The compounds were tested in both purified NK cells as well as a cell preparation that contained other mononuclear cells (predominantly T cells) and NK lymphocytes (referred to as T/NK cells). Lymphocytes were exposed to the compounds for periods of time ranging from 1 hour to 6 days. Exposure of highly purified NK cells to 5 microM alpha-chlordane, gamma-chlordane, 4,4'-DDT, heptachlor, oxychlordane, or pentachlorophenol (PCP) inhibited their ability to destroy K562 tumor-cells by 88+/-5, 92+/-8, 61+/-13%, 64+/-10%, 69+/-11%, 76+/-12%, respectively, after a 24 h exposure. The loss of cytotoxic function seen with alpha-and gamma-chlordane remained essentially constant out to 6 days, while that seen with 4,4'-DDT, oxychordane and PCP increased with longer exposures (6 d). PCP was the most effective of the compounds tested at decreasing NK function. Of the compounds that caused decreased lytic function when tested in purified NK cells, only PCP and oxychordane decreased the lytic function of the T/NK cell preparation after any exposure. The results provide evidence of relative toxic potential for the 11 compounds and their immunomodulatory effects on other mononuclear cells (such as T-cells, B-cells, and monocytes) as well as NK lymphocyte function.