Headland bypassing timescales: Processes and driving forces.

In this paper, a natural headland bypassing is investigated in terms of its short (months to years) and long-term (years to decades) variability and its relationship with wave conditions, climate drivers and anthropogenic interventions. The research is focused on Fingal Head (New South Wales, Australia) where nine detailed topo-bathymetric surveys were undertaken between June 2018 and January 2020. To extend the analysis in time, over 30 years of satellite and aerial images were used to describe the headland bypassing variability based on the shoreline and sandbar position changes. Shoreline and sandbar positions presented moderate to strong correlation between updrift and immediate downdrift of the headland highlighting the influence of the bypassing process for the longshore transport on the study area. Results indicate that the headland bypassing around Fingal Head is governed by two distinct processes and their dominance is controlled by waves and sediment availability. The sandbar-driven bypassing scenario requires a storm wave event to trigger the sandbar system and over seven months to complete the full bypassing cycle. A quicker bypassing cycle (i.e. few months) happens when sediment leaks around the headland following a persistent low energy wave condition that largely accretes the updrift upper beach. Headland bypassing cycles occur in multiple timescales, including seasonal variability of the wave climate to interannual and decadal cycles of shoreline progradation and retreat. Shifts in the large-scale climate drivers such as El Niño-Southern Oscillation, Pacific Decadal Oscillation and Interdecadal Pacific Oscillation were observed to influence on changes to the low frequency of variability of the headland bypassing in the study area by affecting the predominant wave direction and updrift beach sand availability. The understanding of this intermittent nature of the headland bypassing process and particularly considering its periodicity and the related driving forces is crucial to predict future coastal hazards and develop management strategies.

(Fluoro)quinolones and quinolone resistance genes in the aquatic environment: A river catchment perspective.

This study provides an insight into the prevalence of (fluoro)quinolones (FQs) and their specific quinolone qnrS resistance gene in the Avon river catchment area receiving treated wastewater from 5 wastewater treatment plants (WWTPs), serving 1.5 million people and accounting for 75% of inhabitants living in the catchment area in the South West of England.. Ofloxacin, ciprofloxacin, nalidixic acid and norfloxacin were found to be ubiquitous with daily loads reaching a few hundred g/day in wastewater influent and tens of g/day in receiving waters. This was in contrast to other FQs analysed: flumequine, nadifloxacin, lomefloxacin, ulifloxacin, prulifloxacin, besifloxacin and moxifloxacin, which were hardly quantified. Enantiomeric profiling revealed that ofloxacin was enriched with the S-(-)-enantiomer, likely deriving from its prescription as the more potent enantiomerically pure levofloxacin, alongside racemic ofloxacin. While ofloxacin's enantiomeric fraction (EF) remained constant, high stereoselectivity was observed in the case of its metabolite ofloxacin-N-oxide. The removal efficiency of quinolones during wastewater treatment at 5 WWTPs utilising either trickling filters (TF) or activated sludge (AS), was compound and wastewater treatment process dependent, with AS providing better efficiency than TF. The qnrS resistance gene was ubiquitous in wastewater. Its removal was WWTP treatment process dependent with TF performing best and resulting in significant removal of the gene (from 28 to 75%). AS underperformed with only 9% removal in the case of activated sludge and actual increase in the gene copy number within sequencing batch reactors (SBRs). Interestingly, the data suggests that higher removal of antibiotics could be linked with high prevalence of the gene (SBR and WWTP E) and vice versa, low removal of antibiotic is correlated with lower prevalence of the gene in wastewater effluent (TF, WWTP B and D). This is especially prominent in the case of ofloxacin and could indicate that AS might be facilitating antimicrobial resistance (AMR) prevalence to higher extent than TF. Wastewater-based epidemiology (WBE) was also applied to monitor any potential misuse (e.g. direct disposal) of FQs in the catchment. In most cases higher use of antibiotics with respect to official statistics (i.e. ciprofloxacin, ofloxacin) was observed, which suggests that FQs management practice require further attention.

An alternative approach to control saltwater intrusion in coastal aquifers using a freshwater surface recharge canal.

Aquifers are a major source of freshwater in many parts of the world. Saltwater intrusion from the sea or saline lakes into freshwater aquifers degrades the potable quality of these resources. Various methods have been introduced to mitigate saltwater intrusion, such as recharge wells and physical subsurface barriers. This paper presents an alternative approach to control saltwater intrusion in coastal aquifers using a surface water recharge canal. In this paper, the effectiveness of a recharge canal at mitigating saltwater intrusion is evaluated numerically using SEAWAT. The results indicate that the recharge canal leads to a reduction in the extent of the saltwater intrusion. Under a fixed hydraulic gradient, the extent of this reduction is dependent on the location of the recharge canal relative to the saltwater source. As the hydraulic gradient increases, with the optimum location of the recharge canal approaches the saltwater source location. The results also indicate that more effective saltwater repulsion is achieved when the recharge canal is located near the toe of the saltwater wedge. The results of a field scale case study indicate that a recharge canal with relatively small dimensions could have a significant effect on reduction in the extent of the saltwater intrusion.