==Soil Particle Size Analysis Methods==

[[File:sieve.jpg|left|thumb|caption|US Standard Sieve]]

There are three basic classifications of [[soil]] particle size. They include [[clay]], [[silt]] and [[sand]], from smallest to largest, respectively. There are several different methods to determining how much clay, silt and sand is in a sample of soil, two include sieving, and another which uses a hydrometer. There is another method used in determining the amount of organic mater in soil, to do this one might use the [[Loss on Ignition]] test, however the purpose of this article will be to focus on clay, silt and sand only.

===Sieving===

To begin, the soil sample needs to be dried to a constant weight, for 24 hrs at 120˚F this will eliminate all the moisture held in the soil.
Once the soil is dried to constant weight, the sieving can begin. The sieves come with different size screens and they should be chosen according to the particles that are to be isolated.

There should be one sieve on top with larger holes to accommodate for gravel that is in the soil. Gravel includes any particle larger than 2mm and will be considered as "sand". [1]
[[File:sievestack.jpeg|right|thumb|caption|Stacked Sieve: largest screen size at the top, smallest screen sieve at the bottom]]

Course sand particles range from 1.0 - 2.0 mm while very fine sand particles range from 0.05 - 0.10mm.[1] Choosing two or more sieves within that range might be helpful to account for larger or smaller sand particles; for instance, include a sieve at 2.0mm and one at 0.05mm.
Silt particles ranges from 0.05mm - 0.002 mm [1], therefore a sieve with a corresponding screen hole size of 0.002 mm should suffice.

Lastly, clay particles are anything smaller than 0.002mm. [1] At the bottom of the stack of sieves should be placed a bottom container with a solid bottom to collect the clay particle that will sift past the 0.002mm sieve.

Once the sieves are set up, the soil sample that has been dried to a constant weight will be sifted through the sieves using a sieve shaker. After about 15-20 min of shaking the soil should be separated into gravel, sand, silt and clay. The proportions can then be calculated to determine how much of each particle is one soil sample. For instance, 26g sand/50g total soil = 52% sand.

Soil sieving is a purely mechanical process of determining soil particle size in a sample of soil. [2] A better method to accurately separating clay particles from the soil would be to use a hydrometer.

===Hydrometer===

[[Clay]] particles are made up of either three or four charged ions, because of this they tend to cling to one another [3], this tendency is called flocculation[4]. This can sometimes pose a problem when trying to accurately determine the proportion of clay particles in a sample of soil. Measuring soil samples using a hydrometer will give an accurate reading of sand silt and clay particles.
[[File:hydrometer.jpg|right|thumb]]
To measure using a hydrometer, a solution of water mixed with sodium hexametaphosphate is prepared and poured into a 1000ml graudated cylinder. The soil sample (for example 50g soil) is then poured into the solution and shaken or stirred until evenly distributed. The hydrometer is then placed in the graduated cylinder, and a measurement is read off of it after 40 seconds. The hydrometer is then taken out and the solution of soil, water, and sodium hexmetaphosphate it stirred or shaken again. Another 40 second reading will be taken and then an average of the two readings will be calculated to determine the amount of sand (and gravel) in the sample. The solution, with the hydrometer in it still, will then sit for at least an hour, the reading on the hydrometer will show the amount of clay in the sample, and the remainder of the sample will be silt.

The proportion of clay is able to be determined due to the sodium hexametaphospahte, which acts as a defloccuant, meaning the clay particle ions will now repulse each other instead of clinging to one another. [4,5]

===References===
1. Whiting, David, et al. Estimating Soil Texture. 2003, Estimating Soil Texture, culter.colorado.edu/~kittel/SoilChar(&RibbonTest)_handout.pdf.

2. “Particle Size Analysis (for Soils/Sediments).” UCL Department of Geography, www.geog.ucl.ac.uk/resources/laboratory/laboratory-
methods/particle-size-analysis/particle-size-analysis-for-soils-sediments.

3. “1.8 Clay Mineral Structure.” Fundamentals of Soil Ecology, by David C. Coleman et al., Academic Press, 2018.

4. Tozzi, Nilo. “Deflocculants: A Detailed Overview.” Deflocculants: A Detailed Overview, digitalfire.com/4sight/education/deflocculants_a_detailed_overview_324.html.

5. Andreola, Fernanda, et al. “The Role of Sodium Hexametaphosphate in the Dissolution Process of Kaolinite and Kaolin.” Journal of the European Ceramic Society, Elsevier, 24 Sept. 2003, www.sciencedirect.com/science/article/pii/S0955221903003662.

Soil Particle Size Analysis Methods

2019-05-03T19:27:05Z

Taylorga: /* Sieving */

==Soil Particle Size Analysis Methods==

[[File:sieve.jpg|left|thumb|caption|US Standard Sieve]]

There are three basic classifications of [[soil]] particle size. They include [[clay]], [[silt]] and [[sand]], from smallest to largest, respectively. There are several different methods to determining how much clay, silt and sand is in a sample of soil, two include sieving, and another which uses a hydrometer. There is another method used in determining the amount of organic mater in soil, to do this one might use the [[Loss on Ignition]] test, however the purpose of this article will be to focus on clay, silt and sand only.

===Sieving===

To begin, the soil sample needs to be dried to a constant weight, for 24 hrs at 120˚F this will eliminate all the moisture held in the soil.
Once the soil is dried to constant weight, the sieving can begin. The sieves come with different size screens and they should be chosen according to the particles that are to be isolated.

There should be one sieve on top with larger holes to accommodate for gravel that is in the soil. Gravel includes any particle larger than 2mm and will be considered as "sand". [1]
[[File:sievestack.jpeg|right|thumb|caption|Stacked Sieve: largest screen size at the top, smallest screen sieve at the bottom]]

Course sand particles range from 1.0 - 2.0 mm while very fine sand particles range from 0.05 - 0.10mm.[1] Choosing two or more sieves within that range might be helpful to account for larger or smaller sand particles; for instance, include a sieve at 2.0mm and one at 0.05mm.
Silt particles ranges from 0.05mm - 0.002 mm [1], therefore a sieve with a corresponding screen hole size of 0.002 mm should suffice.

Lastly, clay particles are anything smaller than 0.002mm. [1] At the bottom of the stack of sieves should be placed a bottom container with a solid bottom to collect the clay particle that will sift past the 0.002mm sieve.

Once the sieves are set up, the soil sample that has been dried to a constant weight will be sifted through the sieves using a sieve shaker. After about 15-20 min of shaking the soil should be separated into gravel, sand, silt and clay. The proportions can then be calculated to determine how much of each particle is one soil sample. For instance, 26g sand/50g total soil = 52% sand.

Soil sieving is a purely mechanical process of determining soil particle size in a sample of soil. [2] A better method to accurately separating clay particles from the soil would be to use a hydrometer.

===Hydrometer===

Because [[clay]] particles are made up of either three or four charged ions, they tend to cling to one another [3], this being called flocculation[4]. This can sometimes pose a problem when trying to accurately determine the proportion of clay particles in a sample of soil. Measuring soil samples using a hydrometer will give an accurate reading of sand silt and clay particles.
[[File:hydrometer.jpg|right|thumb]]
To measure using a hydrometer, a solution of water mixed with sodium hexametaphosphate is prepared and poured into a 1000ml graudated cylinder. The soil sample (for example 50g soil) is then poured into the solution and shaken or stirred until evenly distributed. The hydrometer is then placed in the graduated cylinder, and a measurement is read off of it after 40 seconds. The hydrometer is then taken out and the solution of soil, water, and sodium hexmetaphosphate it stirred or shaken again. Another 40 second reading will be taken and then an average of the two readings will be calculated to determine the amount of sand (and gravel) in the sample. The solution, with the hydrometer in it still, will then sit for at least an hour, the reading on the hydrometer will show the amount of clay in the sample, and the remainder of the sample will be silt.

The proportion of clay is able to be determined due to the sodium hexametaphospahte, which acts as a defloccuant, meaning the clay particle ions will now repulse each other instead of clinging to one another. [4,5]

===References===
1. Whiting, David, et al. Estimating Soil Texture. 2003, Estimating Soil Texture, culter.colorado.edu/~kittel/SoilChar(&RibbonTest)_handout.pdf.

2. “Particle Size Analysis (for Soils/Sediments).” UCL Department of Geography, www.geog.ucl.ac.uk/resources/laboratory/laboratory-
methods/particle-size-analysis/particle-size-analysis-for-soils-sediments.

3. “1.8 Clay Mineral Structure.” Fundamentals of Soil Ecology, by David C. Coleman et al., Academic Press, 2018.

4. Tozzi, Nilo. “Deflocculants: A Detailed Overview.” Deflocculants: A Detailed Overview, digitalfire.com/4sight/education/deflocculants_a_detailed_overview_324.html.

5. Andreola, Fernanda, et al. “The Role of Sodium Hexametaphosphate in the Dissolution Process of Kaolinite and Kaolin.” Journal of the European Ceramic Society, Elsevier, 24 Sept. 2003, www.sciencedirect.com/science/article/pii/S0955221903003662.

Annelids

2019-05-03T17:51:24Z

Taylorga:

Annelids, or segmented worms, are segmented bilaterian invertebrates that are very important to a variety of marine and terrestrial environments. All annelids have a central body cavity called a coelom, bristles called setae, and segments called annulations which they are named after. There are three major groups of of annelids; the class Polychaeta which are almost entirely marine in nature and the subclasses of Oligochaeta which are earthworms and their relatives, and Hirudinea which are leeches. Among these groups there are approximately 17,000 described species. Many of the species of annelids reproduce sexually and are hermaphroditic, but some are able to asexually reproduce. Annelids are found across the entire planet in almost every kind of environment imaginable. Annelids are generally soft tissue organisms, but there is evidence of them in the fossil record dating back to the Ordovician period.[[File:Annelida.png|600px|thumb|right|]]

== Classification ==

Annelids belong to the clade Lophotrochozoa. This clade includes the phyla Mollusca, Sipuncula, Brachiopodia, and Phorondia. [1] The two major groups of
annelids are the clitellates and polychaetes. Clitellates include members of the subclasses oligochaeta (eg. earthworms) and hirundinea (leeches). Oligochaetea are primarily terestrial, preferring damp soil, while leeches are mostly made up of freshwater aquatic species. Polychaetes are almost entirely made up of marine species, but a few freshwater species do exist.[1] There are abut 17,000 species of annelid and about 12,000 of them are members of polychaetes. Polychates are then divided into two groups dependent on if they are mostly mobile throughout life or if they live in tubes or burrows for the majority of their existence. There are also about 42 different groups of cilliates[2].[[File:Leech.jpg|200px|thumb|right| ''Haemadipsa picta'' or the Tiger Leech member of the hirundinea subclass]]

----

== Distribution and Habitat ==

Annelids, due to their incredible diversity, live in nearly every habitat on planet, however they have no means of protecting themselves from desiccation, therefore they prefer to live in wet environments. These environments include oceanic sea floors, freshwater systems, and damp soil.[3] The class Polychaeta are primarily benthic [[organisms]] that can live in saline, brackish, or freshwater environments. Their distribution in these areas are primarily controlled by the space available to them, the dissolved oxygen content in the water, the rate of movement of the water, and the relative salinity and temperature of the water to the Polychaeta.[4] Oligochaetes are primarily found in the soil but a few are found in aquatic environments, and leeches are almost entirely aquatic or limited to humid areas.[3]

----

== Morphology/Anatomy ==
Annelids are bilaterally symmetrical [[animals]]. The entire body of an annelid is composed of segments. They are named after the Latin word "anellus" which means little ring.[2] These segments can grow in number as the annelid grows in length, with exception of leeches which can have 34 segments and grow by expanding those 34 segments.[3] Annelids also have setae, or chaetae, which are long filaments or hooked structures made up up many chitinous cylinders held together by sclerotinized proteins.[2] These seatae are important in anchoring the annelids down and to help them move up surfaces.

[[File:EarthwormCrossSection.jpg|200px|thumb|left| Cross section of an earthworm]]

The digestive tract of an annelid is essentially one tube that runs from the mouth of the organism to the anus. The area between the inner cavity and the outside of the annelid is called the coelem. This area is filled with a coelemic fluid that also contains the other organ systems of the animals. This fluid is very important for a variety of functions of the organism such as locomotion, osmoregulation, and multiple metabolic processes among others. In polychaetes this fluid is also used to keep the worm's salt levels similar to the surrounding water. The coelmic fluids of leeches are filled with connective tissue and becomes more so as the leech ages. Oxygen is generally absorbed through the skin of the annelid and passed through the body by a closed circulatory system.[3]

----

== Life Cycle and Reproduction ==
[[File:Earthwormsmating.jpg|200px|thumb|Left|Two earthworms exchanging sperm.]]
====Polychaetes====
Many terrestrial annelids are hermaphroditic however, many polychaetes have defined male and female sexes for spawning[2]. Polychaete spawn near the surface marine environments. When they want to spawn they will swim to the surface and the females will release the eggs and the males will fertilize them.[5] The worms then undergo various stages of development under the protection of their mother until they are fully developed displaying a type of brooding behavior[5]. [[File:Bobbit Worm.jpg|200px|thumb|Right|''Eunice aphroditois''
or the Bobbit Worm, an aquatic predatory polychaete worm that buries beneath sediments to ambush prey]]
====Oligochaetes====
Oligochaetes are also hermaphroditic, each individual posses both male and female reproductive organs. While they may appear to reproduce sexually, they are instead exchanging sperm which is then stored in sperm sacs[7]. The sperm is later released along with the eggs into a cocoon initially located on the clitellum. Other oligochaetes can reproduce parthenogenetically without fertilization by sperm[7]. Oligochaetes do not undergo a larval stage rather they simply exit the cocoon as small oligochaetes and grow larger as they become more mature[3].
====Hirudinea====
----

== Role in Soil ==

[Oligochaetes] are the primary annelids found in [[soil], there are believed to be more than 5,000 earthworm species[7]. Earthworms are considered ecosystem engineers because of the role they play in the structure of soils and the diversity of the soil ecosystem. Earthworms either get their food from the surface leaf litter or the organic residue found in soil.[6] The majority of organics that an earthworm will ingest are from dead plant matter, but they will also consume living animals such as [[nematodes]] and other microfauna.[6] Earthworms prefer foods with a high nitrogen content and they also eat to burrow as well. As they burrow they leave nutrient rich casts which are important for returning nutrients to the soil. This aerates the soil, provides more nutrient for living plants, and helps prevent erosion. These nutrient rich casts are a big reason why earthworms are important to agriculture and why they are sought out when planting an new field.[6]

----

== References ==

1. Parry, L. , Tanner, A. , Vinther, J. and Smith, A. (2014), The origin of annelids. Palaeontology, 57: 1091-1103. doi:10.1111/pala.12129

2. Rouse, G. W. (2001). Annelida (Segmented Worms). In eLS, (Ed.). doi:10.1038/npg.els.0001599

3. Reish, D. J. (2013, December 18). Annelid. Retrieved April 12, 2018, from https://www.britannica.com/animal/annelid

4. Lardicci, C. , Abbiati, M. , Crema, R. , Morri, C. , Bianchi, C. N. and Castelli, A. (1993), The Distribution of Polychaetes Along Environmental Gradients: An Example from the Or betel I o Lagoon, Italy. Marine Ecology, 14: 35-52. doi:10.1111/j.1439-0485.1993.tb00363.x

5. Annie Mercier, Sandrine Baillon, Jean-François Hamel,Life history and seasonal breeding of the deep-sea annelid Ophryotrocha sp. (Polychaeta: Dorvelleidae),Deep Sea Research Part I: Oceanographic Research Papers,Volume 91,2014,Pages 27-35,ISSN 0967-0637,https://doi.org/10.1016/j.dsr.2014.05.007.

6. Lenardt, A. (2014, April 7). The Role of Earthworms in Soil Systems. Retrieved April 14, 2018, from https://blogs.unbc.ca/biol202/2014/04/07/the-role-of-earthworms-in-soil-systems/

[7]“4.4 The Macrofauna.” Fundamentals of Soil Ecology, by David C. Coleman et al., Elsevier ; London, 2018, pp. 132–168.

''Image Sources''

1.Taken By Phynix Davis in Roosevelt Park on 4/14/2018

2.https://imgur.com/gallery/7oQDJ

3. http://www.savalli.us/BIO385/Diversity/09.Annelida.html

4.http://www.soilanimals.com/look/soil-food-web

5. https://www.mnn.com/earth-matters/animals/stories/bobbitt-worm-blue-planet