https://nova.newcastle.edu.au/vital/access/ /manager/Index ${session.getAttribute("locale")} 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:42895 Tue 06 Sep 2022 14:39:21 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:35044 Thu 21 Oct 2021 12:52:34 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:26344 Sat 24 Mar 2018 07:35:54 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:27242 100 nm) of soils, but in the fine colloidal (< 100 nm) and nominally dissolved (< 1 nm) fractions of dripwaters. The concentration of Cu, Ni and Co in dripwater samples across all sites were well correlated (R2 = 0.84 and 0.70, Cu vs. Ni, Cu vs. Co, respectively), indicating a common association. Furthermore, metal ratios (Cu:Ni, Cu:Co) were consistent with NICA-Donnan n1 humic binding affinity ratios for these metals, consistent with a competitive hierarchy of binding affinity (Cu > Ni > Co) for sites in colloidal or dissolved NOM. Large shifts in Cu:Ni in dripwaters coincided with high fluxes of particulate OC (following peak infiltration) and showed increased similarity to ratios in soils, diagnostic of qualitative changes in NOM supply (i.e. fresh inputs of more aromatic/hydrophobic soil organic matter (SOM) with Cu outcompeting Ni for suitable binding sites). Results indicate that at high-flows (i.e. where fracture-fed flow dominates) particulates and colloids migrate at similar rates, whereas, in slow seepage-flow dripwaters, particulates (> 1 μm) and small colloids (1–100 nm) decouple, resulting in two distinct modes of NOM–metal transport: high-flux and low-flux. At the hyperalkaline drip site PE1 (in Poole's Cavern), high-fluxes of metals (Cu, Ni, Zn, Ti, Mn, Fe) and particulate NOM occurred in rapid, short-lived pulses following peak infiltration events, whereas low-fluxes of metals (Co and V > Cu, Ni and Ti) and fluorescent NOM (< ca. 100 nm) were offset from infiltration events, probably because small organic colloids (1–100 nm) and solutes (< 1 nm) were slower to migate through the porous matrix than particulates. These results demonstrate the widespread occurrence of both colloidal and particulate NOM–metal transport in cave dripwaters and the importance of karst hydrology in affecting the breakthrough times of different species. Constraints imposed by soil processes (colloid/particle release), direct contributions of metals and NOM from rainfall, and flow-routing (colloid/particle migration) are expected to determine the strength of correlations between NOM-transported metals in speleothems and climatic signals. Changes in trace metal ratios (e.g. Cu:Ni) in speleothems may encode information on NOM composition, potentially aiding in targeting of compound-specific investigations and for the assessment of changes in the quality of soil organic matter.]]> Sat 24 Mar 2018 07:29:08 AEDT ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:53142 Fri 17 Nov 2023 12:08:21 AEDT ]]>