https://ogma.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:36537 Wed 21 Feb 2024 10:03:31 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:46319 2-mm aggregates under dry sieving. Furthermore, the GMean index showed a significant positive relationship with soil OM, TN, and AN under both dry and wet sieving methods.]]> Tue 15 Nov 2022 11:45:54 AEDT ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39230 −1 of As(V)]. Besides, it was observed that available soil phosphorus could positively affect the relative content of water-soluble, exchangeable and carbonate-bound arsenic. In the kinetics experiment, both the Michaelis-Menten constant (K_m) and maximum reaction velocity (V_max) of ALP increased with increasing As(V) concentration under four months ageing for each size aggregate. Multiple linear stepwise regression analysis between k_cat and the relative content of arsenic fraction indicated that carbonate-bound arsenic is the main fraction that inhibited the k_cat for macroaggregates (> 0.25 mm size). For soil aggregates of 0.1–0.25 mm size, k_cat increased with an increase in arsenic residual fraction. As for aggregates <0.1 mm size, Fe and Mn oxide-bound fraction is the main fraction that inhibited the k_cat. Overall, this study suggests carbonate-bound and Fe and Mn oxide-bound arsenic fractions could decrease the ALP activities via a decrease in the catalytic efficiency in macroaggregates and <0.1 mm size aggregates, respectively. Besides, available phosphorus should be considered as the main factor when assessing As biotoxicity and mobility.]]> Tue 09 Aug 2022 14:08:44 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:33556 Tue 03 Sep 2019 18:31:47 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:39536 Mon 08 Aug 2022 11:27:21 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:42230 Fri 19 Aug 2022 11:35:34 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:32983 max) and Michaelis constant (K_m) in unpolluted soils were 0.012-0.267 mM h^-1 and 1.34-3.79 mM respectively. The competitive inhibition constant (K_ic) was 0.17-0.70 mM, which was lower than K_m, suggesting higher enzyme affinity for As than for substrate. The ecological doses, ED₁₀ and ED₅₀ (concentration of As that results in 10% and 50% inhibition on enzyme parameter) for inhibition of catalytic efficiency (V_max/K_m) were lower than those for inhibition of enzyme activity at different substrate concentrations. This suggests that the integrated kinetic parameter, catalytic efficiency is substrate concentration independent and more sensitive to As than ALP activity. Thus, catalytic efficiency was proposed as a more reliable indicator than ALP activity for risk assessment of As pollution.]]> Fri 17 Aug 2018 15:44:20 AEST ]]> https://ogma.newcastle.edu.au/vital/access/ /manager/Repository/uon:32987 m) and maximum reaction velocity (V_max) values of soil ACP ranged from 1.18 to 3.77 mM and 0.025–0.133 mM h⁻¹ in uncontaminated soils. The kinetic parameters of soil ACP in different soils changed differently with As contamination. The K_m remained unchanged and V_max decreased with increase of As concentration in most acid and neutral soils, indicating a noncompetitive inhibition mechanism. However, in alkaline soils, the K_m increased linearly and V_max decreased with increase of As concentration, indicating a mixed inhibition mechanism that include competitive and noncompetitive. The competitive inhibition constant (K_ic) and noncompetitive inhibition constant (K_iu) varied among soils and ranged from 0.38 to 3.65 mM and 0.84–7.43 mM respectively. The inhibitory effect of As on soil ACP was mostly affected by soil organic matter and cation exchange capacity. Those factors influenced the combination of As with enzyme, which resulted in a difference of As toxicity to soil ACP. Catalytic efficiency (V_max/K_m) of soil ACP was a sensitive kinetic parameter to assess the ecological risks of soil As contamination.]]> Fri 17 Aug 2018 15:43:55 AEST ]]>