Local scale interventions dominate over catchment scale controls to accelerate the recovery of a degraded stream

A premise of stream restoration theory and practice is that it is often futile to attempt to restore a stream at the reach scale (101–103 metres) until catchment scale problems have been addressed. This study considers reach scale restoration actions undertaken in Bryan Creek, a sand bed river in south east Australia impacted by a sediment pulse, after catchment sediment sources have been addressed. Local scale interventions, which were in-stream sand extraction, fencing to exclude stock and riparian revegetation, were evaluated by quantifying cross-section and thalweg variability, mapping in-stream and riparian vegetation and by classifying the morphology that emerged following each intervention. Following intervention channel reaches moved to one of three distinct states: simple clay bed, eroding reaches dominated by Juncus acutus, and reaches with deep pools and Phragmites australis. Boundaries between the intervention reaches were sharp, suggesting local scale interventions dominate over catchment scale processes. The magnitude and spread of variability metrics were similar between all reaches and differences in variability bore no relation to intervention type, despite the stark difference in post-intervention morphology. These findings suggest that cross-section and thalweg variability metrics are an inadequate proxy for the effectiveness of local scale interventions in accelerating the recovery of sand bed reaches from a bedload pulse. The most important implications for river managers is that local scale interventions can lead to substantial and rapid improvements in condition, and the change in condition of these reaches is almost independent of other reaches. In this case, the key to the pattern of reach scale geomorphic recovery is excluding stock from waterways so that a specific macrophyte can establish, trap sediment and develop pools.

Phytochemical screening, antioxidant and antilithiasis activities of Juncus acutus

The objective of this work was to perform a phytochemical screening of Juncus acutus and to evaluate its antioxidant activity and antilithiasis activity. Phytochemical screening has demonstrated the presence of catechin, tannins and alkaloids in the various extracts studied. The antioxidant activity of the methanolic and ethyl acetate extracts by ultrasound and maceration was evaluated by the method of DPPH, FRAP and phosphomolybdate. The ethyl acetate extract by ultrasound, the methanolic extract by maceration and ultrasound respectively showed IC 50 with DPPH of 1,449mg / ml, 1,535mg / ml and 4,771mg / ml and a reducing power was observed at concentrations of 419,561mgBHA /100g, 207,143mgBHA /100g and 142,20mgBHA /100g by FRAP and at concentrations of 839,470mgAAE/100g, 283,260mgAAE/100g and 141,018mgAAE/100g by the phosphomolybdate test. The determination of the total polyphenols of the ethyl acetate extract by ultrasound, the methanolic extract by maceration and by ultrasound presented respectively contents of 2,428 mg GAE / g, 1,960mg GAE / g and 1,172mg GAE / g, likewise, the flavonoid assay showed respectively concentrations of 14,469mg EQ/g, 6,466 mg EQ/g and 3,143 mg EQ/g. Antilithiasis activity was evaluated on carbapatite, cystine and uric acid stones. The mass loss of uric acid, carbapatite and cystine stones was respectively 42%, 7% and 16%.

XRD-Thermal Combined Analyses: An Approach to Evaluate the Potential of Phytoremediation, Phytomining, and Biochar Production

A method for evaluating the potential of reuse of biomasses for economic purposes is here presented starting from a case study. Juncus acutus plants and rhizospheres were harvested from abandoned Zn–Pb mine areas of southwest Sardinia (Italy). Thermogravimetry and Differential Thermal analyses were performed to evaluate the temperatures at which significant reactions occur. X-ray Diffraction (XRD) analysis was carried out on raw samples and on samples heated ex-situ (by a conventional diffractometer) or in-situ (by synchrotron-based diffraction). Raw samples mainly consist of quartz, phyllosilicates, and feldspars with minor amounts of sulfides, sulfates, and Fe, Pb, and Zn carbonates, concentrated in the rhizosphere. After heating, Zn and Fe oxides and willemite are observed in internal roots and stems, revealing the presence of these metals in the plant tissues. In-situ heating was less effective than ex-situ in revealing minor phases in organic samples, probably because the scarcity of oxygen within the sample holder did not allow the degradation of organic compounds and the oxidation of sulfides, resulting in a low quality XRD signal even if obtained with the high resolution ensured by a synchrotron light source. This method can be applied to plants from polluted sites for metal exploitation, and/or to biomasses from unpolluted sites for biochar production, since both applications take advantage of the knowledge of the minerals formed after heating.