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The role of biochar in sequestration of carbon, reducing the emission of greenhouse gases, and improving the soil fertility is increasingly being recognised and is leading to the recommendations of biochar amendment of soils. However, the implications of such amendments to the environmental fate and efficacy of pesticides are not well understood. The published work on the role of black carbon (which includes charcoal, soot, and other pyrolytic carbon materials) in the environmental fate and effect of organic contaminants is reviewed here, together with the studies on bioavailability and efficacy of some herbicides in soils amended with freshly produced biochars. Biochars, due to their unique properties especially their highly carbonaceous and aromatic nature and high specific surface area, have been reported to be up to >2000 times more effective than soil in sorbing pesticides. The incorporation of relatively small amounts of fresh biochars in soil (0.05% by wt) has also been shown to inhibit the microbial degradation of organic compounds including pesticides as well as reduce their plant availability and efficacy. Based on limited published research on biochars and related research on black carbon reviewed here, biochar amendments to soils are likely to reduce the bioavailability and efficacy of pesticides. Furthermore, these amendments can influence the potential accumulation and ecotoxicological impact of pesticides and other organic contaminants in the soil environment. The implications of heterogeneity and ageing of biochars applied to soils for sorption and desorption processes and in turn for other environmental fate processes need to be understood to seek the appropriate balance between carbon sequestration and pesticide efficacy. While biochar amendment of soil holds appeal from a carbon accounting and soil conditioning perspective, further research is urgently required to determine how biochar influences the efficacy and environmental fate of agrochemicals such as pesticides. Additional keywords: biochar, black carbon, pesticides, efficacy, carbon sequestration, ecosystem health., Introduction The potential role of biochar in carbon sequestration, reduction in the emission of greenhouse gases, and improving the soil fertility has led to the establishment of the International Biochar [...]

Off-site movement of pesticides from furrow-irrigated agriculture has been a concern in the Ord River Irrigation Area, Western Australia. After consultation with growers a range of management strategies were tested to assess the effectiveness of various practices to minimise off-site movement of pesticides during irrigation. This paper reports on the effectiveness of the additions of high molecular weight, anionic, polyacrylamide (PAM) to irrigation water to minimise off-site movement of endosulfan, chlorothalonil, bupirimate, and atrazine. Water leaving from 4 separate irrigation bays, which consisted of 25 furrows per irrigation bay (Expt 1) or 39 furrows per irrigation bay (Expt 2), was monitored over time. The average concentration of endosulfan α and β and bupirimate leaving the irrigation bays for the duration of the single irrigation event was generally always less for the PAM-treated irrigation bays than the control (control treatment). The addition of PAM to the irrigation water significantly decreased the cumulative runofflosses (g) of total endosulfan by 54% from 11.41 to 5.19 g/ha (P < 0.05), and of chlorothalonil by 49% from 53.65 to 27.32 g/ha (P < 0.001). There was no statistical difference in the load of atrazine or bupirimate leaving either treatment. Although the addition of PAM to irrigation water effectively decreased the off-site movement of 2 fairly strongly sorbed pesticides, endosulfan and chlorothalonil, it did not decrease the total load moving offsite of the more weakly sorbed pesticides, bupirimate and atrazine. The addition of PAM as a liquid to irrigation water was not found to increase the infiltration of a soluble pesticide, atrazine, into the soil profile. The mode of application of PAM, however, may affect water infiltration and hence vertical movement of soluble pesticides and requires further investigation. Additional keywords: bupirimate, endosulfan, chlorothalonil, atrazine., Introduction The Ord River Irrigation Area (ORIA), located around the township of Kununurra in the tropical north of Western Australia near the Northern Territory border, is one of the main [...]

Researchers measured the soil organic matter (SOM) structural composition of 27 diverse soils in Pakistan and Australia. Researchers believe that the aromatic quality of the soil organic matter will tell whether or not the soil can bind to nonionic pesticides. Tables illustrate soil quality and research findings.

The effects of wastewater treatment plant (WWTP) discharge on the ecology of bacterial communities in the sediment of a small, low-gradient stream in South Australia are examined. The results have suggested the cause and effect between nutrients loading into the creek, shift in bacterial communities through habitat change and alteration of capacity for biogeochemical cycling of N.

A chromatographic model (VARLEACH) and a process-based model (LEACHM) were evaluated under low and high water input regimes (`rainfall' and `rainfall + irrigation', respectively) using experimental data for a non-reactive tracer (KBr), and 3 sulfonylurea herbicides: triasulfuron, metsulfuron-methyl, and chlorsulfuron. Both qualitative and quantitative comparisons of predicted and measured water contents revealed that both models performed well under `rainfall', but prediction was less satisfactory under the treatment of `rainfall + irrigation'. Both models failed to simulate the bimodal distribution of [Br.sup.-] and the herbicides observed under `rainfall + irrigation' treatment. Distribution of [Br.sup.-] and the 3 herbicides in the profile was over- or under-estimated at certain depths and times, probably due to the limitations inherent to the models (e.g. inability to deal with the macropore flow), and to simplifications associated with some input data. Simulations for a dry (1 decile), median (5 decile), and wet year (9 decile) with LEACHM and VARLEACH models using long-term weather data for the site showed that leaching and persistence of the herbicides are highly dependent on the amount of rainfall the site receives. The results indicate that the risk of injury to herbicide-sensitive crops in the following year of application of herbicides is likely to be greater when the herbicides are applied in a drier rather than a wetter year. Additional keywords: simulation, herbicide persistence, transport, modelling efficiency., Introduction Computer simulation models are useful in understanding the behaviour of agricultural chemicals in the soil and their movement into the groundwater (Khakural et al. 1995) under a range of [...]