Assessment notes – Coursework 2

You are asked to compose a 2000-word digital report corresponding to the following learning outcomes (described in the module brief):

LO2: Understand the processes associated with the evolution of coastal, aeolian and fluvial systems;

LO4: Present, analyze and interpret geomorphic data and set it in the context of published literature in a concise written form.

We will specifically focus on particle size, sedimentation processes on estuaries and methods for sediment analysis (Sieving and PSA lab practical).

Context

Estuaries are important coastal systems that constitute the interface among terrestrial, riverine, and marine environments. They are temporal sedimentary sinks of riverine material, predominantly in the vicinity of the estuarine turbidity maximum area [Liu et al., 2011; Uncles and Stephens, 2010; Woodruff et al., 2001; Xu et al., 2010], a salient estuarine feature.

This material may be re-suspended and subsequently exported to the coastal ocean during periods of high river discharge known as freshets [Geyer et al., 2001]. The fine sedimentary particles found in estuarine waters are in either individual or aggregated (flocculated) form; they provide the surface area for the absorption of heavy metals and other pollutants, as well as nutrients. During periods of intense sedimentation, the particles can be trapped into the seabed through sediment burial, and the attached material may be modified by a number of complicated physical and/ or biochemical processes [Sholkovitz, 1976; Wang, 2002; Zhang, 1999] that affect the biogeochemical cycle, therefore creating different distribution patterns along the estuary.

During the field trip, you have collected surface sediment samples from 4 transects, each subdivided into three quadrats representing, high, mid and low tide. You have also collected a 50cm deep core, within the adjacent salt-marsh.

These samples were taken into the soils lab, at the University of Brighton and the following steps were taken:

• Wet samples were homogenized and approximately 10g was separated and transferred into a labeled beaker to be dried.
• Subsamples were dried at 100°C for 48 hours, or until the dried weight was constant.
• Samples were carefully ground with a pestle and mortar before being transferred into sample bags.
• A small, 2-4g subsample from each bag was mixed with 5ml of Calgon (sodium hexametaphosphate) prior to analysis and then stirred for 5 minutes in order to deflocculate clay particles.
• A small sub-sample (~ 1 – 1.5 g, dependent on laser obscuration related to particle size), was analyzed using a laser particle size analyzer, which improves the dispersion of particles during analysis by breaking up aggregates using vibrating sound waves.
• What is the PCA and what it does? sedimentation process and how it moves

From the provided results dataset, you should be able to calculate the mean (central value) and sorting coefficient (standard deviation) for each sample using a suitable formula from the literature. You should also be able to classify your sediment according to Wentworth’s (1922) grain size scale, and Folk and Ward’s (1957) degree of sorting.

Your report should explore the relationships between sediment grain size, degree of sorting, and tidal influence, sedimentation processes, and depth gradients in order to address the title and follow the report structure presented below.

The Task

Introduction (15% of marks)

• State the problem, why is it important to study sediment processes in estuaries (5%)?
• Elaborate on the terminology of the title (What are estuaries? What can you say about Adur estuary? What type of esturay talk about the river itself What kind of tidal regime is present? (5%)
• Brief Literature review: Can you find papers where people have done similar experiments, how would your results contribute to this field of research? (5%)

Methodology (25% of marks) sieving and PSA and why one is better than the other and in what pca can be better at some cases,

• Evaluation of particle size methods – Compare and discuss both sieving and PSA methods, including pros and cons to their applicability. Which one was used in your experiment and why? (10%)

Which equations did you use to calculate mean grain size and sorting? Why did you choose these and not others? (8%) which and why we use equations for more and letters need to be explained a, mean and sorting

• What type of core we used
• What type of statistical techniques (and software) do you apply for your analysis (7%)?

Results (30% of marks)

• Statistical analysis of the difference between mean or median grain size and sorting coefficient along the transect (high/mid/low tide) virtual lengths and velocities (10%). If there is a difference and what statistical test is ideal for our results, numbers and word result on the graphs
  
  Using existing skills (7%), these can be done using a boxplot. If you want to extend your skills (3% of marks), you may try to create a cumulative density function of the grain size distribution (hence analyzing cumulative values for grain size using percentiles). Histogram of frequency, how much of our sample is bigger or smaller