User:Ebhughes20/sandbox

Evaluating Content
The opening paragraph to this section is excellent, giving a broad overview of the geological and biological uses of silica. The article then immediately discusses silica origins and abundances, and silicifying organisms. Marine silica cycling is discussed in detail. Finally, the climate regulation element of silica cycling, in relation to the carbon and carbonate-silicate cycle, is discussed. Overall, the information is accurate, linked to other Wikipedia articles, and robust. One flaw might be that it's slightly too jargon-y, although again much of the jargon is linked to other Wikipedia articles. The information appears mostly up to date and extensive.

Evaluating Tone
The tone of this article is neutral. The article does a good job avoiding clearly biased language, and no viewpoints appear to be over or underrepresented.

Evaluating Sources
The sourcing could probably use a little additional work; there are some uncited sentences that do not clearly have relational citations in the paragraph. This sentence: "Isotope ratios of oxygen (O18:O16) and silicon (Si30:Si28) are analysed from biogenic silica preserved in lake and marine sediments to derive records of past climate change and nutrient cycling (De La Rocha, 2006; Leng and Barker, 2006)." includes names of citations but no clear links; it should be linked. Having checked on a couple of links, they do take you to the appropriate page. The main thing would be cleaning up citations in the text. The sources appear to go to reputable, unbiased journal articles.

Evaluating Content
The content of this article is generally reasonable. It would benefit from a more thorough investigation of the geologic cycle particularly on longer timescales; this section focuses almost entirely on calcium-44 and is very short. Likewise much of the content focuses on human biological usage of calcium, which is interesting but difficult to place in context of wider biogeochemical cycles. However, the focus on biological activity generally, including plant usage of calcium, was thorough and interesting. The article does link to many other Wikipedia articles and does avoid jargon; information also appears to be up-to-date.

Evaluating Tone
The tone of this article is neutral. There are no very obviously biased sentences or statements. For example, the article discusses ocean acidification—which might be a generally controversial topic—in a very neutral and relevant way.

Evaluating Sources
This sentence: "Ocean acidity due to carbon dioxide has already increased by 25% since the industrial revolution" does not have a citation attached. There are a number of sentences in the "Changes in global climate and the calcium cycle" section that do not have citations. Likewise, under "The importance of the calcium cycle and future predictions" section, many of the opening sentences are not cited, all of which are statements about the role of calcium in hormone and enzyme activities. The links I clicked in the reference section appeared to work, but this article should do a more consistent job of citing statements within the body text. The sources appear to go to reputable, unbiased journal articles.

Evaluating Content
The first sentence is: "The selenium cycle is a biological cycle of selenium similar to the cycles of carbon, nitrogen, and sulfur." This feels like too broad of a statement potentially. There is a cycle but much of the content of the cycle is not discussed in the text and no chemical reactions are in the text. Selenium in terrestrial ecosystems is scantly discussed. Generally, the content of the article is lacking; there should be more robust discussion of the terrestrial system and the language overall could be more precise. One small complaint is selenate, selenite and selenide are all mentioned and linked to other Wikipedia articles, but the chemical formula for these is missing. That should be a given in this article.

Evaluating Tone
The tone of this article is neutral; nothing is obviously biased in the language. It does not appear to lean one way or another on any controversial issues, which appear generally lacking in the article. Overall, it appears to be scientific and objective.

Evaluating Sources
Within the first three paragraphs, there is only one citation. In total there are four citations in the entire article, only one of which was published in this century. The entire "immobilization processes" section contains no citations whatsoever. The article ought to be much more extensively cited.

Goldich Dissolution Series
The Goldich dissolution series is a method of predicting the relative stability or weathering rate of common igneous minerals on the Earth's surface, with minerals that form at higher temperatures and pressures less stable on the surface than minerals that form at lower temperatures and pressures.

Chemical Weathering Processes
S. S. Goldich derived this series in 1938 after studying soil profiles and their parent rocks. Based on sample analysis from a series of weathered localities, Goldich determined that the weathering rate of minerals is controlled at least in part by the order in which they crystallize from a melt. This order meant that the minerals that crystallized first from the melt were the least stable under earth surface conditions, while the minerals that crystallized last were the most stable. This is not the only control on weathering rate; this rate is dependent on both intrinsic (qualities specific to the minerals) and extrinsic (qualities specific to the environment) variables. Climate is a key extrinsic variable, controlling the water to rock ratio, pH, and alkalinity, all of which impact the rate of weathering. The Goldich Dissolution Series concerns intrinsic mineral qualities, which were proven both by Goldich as well as preceding scientists to also be important for constraining weathering rates.

Earlier work by Steidtmann demonstrated that the order of ionic loss of a rock as it weathers is: CO32-, Mg2+, Na+, K+, SiO2-, Fe2+/3+, and finally Al3+. Goldich furthered this analysis by noting the relative mineral stability order, which is related to the relative resistance of these ions to leaching. Goldich notes that overall, mafic (rich in iron and magnesium) minerals are less stable than felsic (rich in silica) minerals. The order of stability in the series echoes Bowen’s Reaction Series very well, leading Goldich to suggest that the relative stability at the surface is controlled by precipitation order.

While Goldich’s original order of mineral weathering potential was qualitative, later work by Michal Kowalski and J. Donald Rimstidt placed in the series in quantitative terms. Kowalski and Rimstidt performed an analysis of mechanical and chemical grain weathering, and demonstrated that the average lifetime of chemically weathered detrital grains quantitatively fit the Goldich sequence extremely well. This helped to supplement the real-world applicability of the dissolution series. The difference in chemical weathering time can span millions of years. For example, quickest to weather of the common igneous minerals is apatite, which reaches complete weathering in an average of 105.48 years, and slowest to weather is quartz, which weathers fully in 108.59 years.

Bowen’s Reaction Series
The Goldich Dissolution Series follows the same pattern of the Bowen's reaction series, with the minerals that are first to crystallize also the first the undergo chemical weathering. The Bowen’s reaction series dictates that during fractional crystallization, olivine and Ca-plagioclase feldspars are the first to crystalize out of a melt, after which follows pyroxene, amphibole, biotite, Na-plagioglase, orthoclase feldspar, muscovite, and finally, quartz. This order is controlled by the temperature of the melt and its composition. Because earlier crystallizing minerals are more stable at higher temperatures and pressures, these weather the fastest under surface conditions.

Common Secondary Minerals
Chemical weathering of igneous minerals leads to the formation of secondary minerals, which constitute the weathering products of the parent minerals. Secondary weathering minerals of igneous rocks can be classified mainly as iron oxides, salts, and phyllosilicates. The chemistry of the secondary minerals is controlled in part by the chemistry of the parent rock. Mafic rocks tends to contain higher proportions of magnesium and ferric and ferrous iron, which can lead to secondary minerals high in abundance of these cations, including serpentine, Al-, Mg- and Ca-rich clays , and iron oxides such as hematite. Felsic rocks tends to have relatively higher proportions of potassium and sodium, which can lead to secondary minerals rich in these ions, including Al-, Na- and K-rich clays such as kaolinite, montmorillonite and illite.



Goldich Series Application to Soil Profiles
The Goldich Dissolution Series can be applied to Lithosequences, which are a way characterizing of a soil profile based on its parent material. Lithosequences include soils that have undergone relatively similar weathering conditions, so variations in composition are based on the relative weathering rates of parent minerals. Therefore, the weathering rates of these soils and their compositions are primarily influenced by the relative proportion of minerals in the Goldrich Dissolution Series.

Limitations of the Series
Experimental work by White and Brantley (2003) highlighted some of the limitations of the Goldich Dissolution series, most notably that some variations in weathering rates of different minerals are not as pronounced as Goldich argues. According to the Goldich dissolution series,  anorthite, a plagioclase feldspar, should weather quickly, with a lifetime of 105.62 years quantified by Kowalski and Rimstidt. Conversely, the lifetime of K-feldspar should be much longer, at 108.53 years based again on Kowalski and Rimstidt’s work. However, White and Brantley’s experimental results demonstrate that the relative weathering rates of K-feldspar and plagioclase feldspar are quite similar, and mainly moderated by the extent to which the minerals had already been weathered (in an exponentially decreasing function). This demonstrates that the Goldich series may not apply across all kinds of weathering processes, and likewise does not take into account the effect of exponential decay in weathering rate of a surface.

The Sulfur Cycle
Evaluating content.

Much of the article appears relevant to the topic at hand. The article focuses on the ionic states of sulfur (which can both lose and gain electrons) and focuses heavily on the redox reactions related to sulfur, which in turn are central to its cycling. Sources and sinks are described. The sulfur cycle through geologic time is also explored.

The article appears relatively up-to-date. The descriptions of the economic importance of and human impact on sulfur cycling are explored, and this includes the production of SO2 as an air pollutant, the subsequent formation of sulfuric acid, and the increased impact of acid rain. Sulfur release in coordination with fossil fuel usage is also described.

The major missing element of the article is the in-depth description of sulfur cycling in a cyclical, source-to-sink process. While sources and sinks, biological and thermochemical reduction, and human impacts are described, there is not a section that evaluates all of these elements in coordination with one another. There is no model figure that shows the relative relational processes (i.e., something like river input leading to oceanic oxidation leading to evaporation and sulfate production).

The article is, however, free of jargon and is clear, and it does link to other Wikipedia articles.

Evaluating tone.

The biologic and thermochemical drivers of sulfate reduction may be overrepresented in this article—though this is an important process, so it's hard to say definitively that it's taking up too much space. Sulfur-oxidation may be given too little time in this article (underrepresented). The article appears relatively neutral aside from these respective prioritization and deprioritization.

Evaluating sources.

This article primarily links to peer reviewed articles related to the course of study. All the links that I checked worked and brought me to the appropriate article. The articles all appeared to be peer reviewed and in reputable journals; many of them were also review articles, which contained summations of the state of science around the subject at hand. These review articles in turn were composed of decades of experimental, observational and modeling studies of the behavior of sulfur across geologic time.

In checking the relationship between the cited source and the written material, in the case of distinguishing the thermal regimes of sulfur reduction for example, the source text was accurately represented by the quoted material. This seemed consistent across the cited texts. A review article on the thermal environments for bacterial and thermochemical sulfate reduction seemed to be nearly directly paraphrased from the abstract.

The sources appear primarily neutral, without apparent bias. The peer review process is a good indication that the quoted sources are sufficiently reliable.

The Iron Cycle
Evaluating content.

The biogeochemical iron cycle figure is key to understanding the processes and movement of iron throughout the environmental systems. This figure is a central element of the article, but it is not sufficiently explained and explored step-by-step.

The article is not sufficiently descriptive. It glosses over redox reactions (key to the understanding of iron cycling) and does not touch nearly enough on the interactions between biological processes and iron cycling, focusing instead (briefly) on iron in terrestrial and oceanic systems, without extensive description.

The article does not contain too much jargon, and is fairly readable. It also does not contain particularly distracting sections and stayed relatively on theme, if it was terse about key subject areas. The article does link to other relevant Wikipedia articles.

Evaluating tone.

The article appears to be neutral and unbiased. There is no obvious bias toward a particular viewpoint. Underrepresented viewpoints may be less viewpoints and just missing content.

Evaluating sources.

The sources seem to be relatively correctly cited, linking to the correct pages, and relatively well-paraphrased. However, there are some exceptions. A source portending to describe the role iron plays in hydrothermal vents actually leads to an article on the role of “airborne volcanic ash for the surface ocean biogeochemical iron-cycle,” which is unrelated to hydrothermalism. The article may also be undersourced, with some key information lacking citations.

The sources appear to be neutral. They are (as far as I could tell) all from peer-reviewed journals, which should be well-vetted for bias.

The Mercury Cycle
Evaluating content.

The central problem with this article is that it is too short. It focuses only on modern mercury cycling (unlike the iron and sulfur cycling pages, which go through the geologic history of these cycles, discussing banded iron formations, e.g.). The article only briefly describes the processes of mercury cycling, without much detailed description of sinks and processes of volatilization or deposition. Everything in the article appears to be relevant to the topic at hand, but that is almost inherent to the dearth of content.

A figure detailing the overall cycle of mercury is provided, but is not explored in sufficient detail. Many of the steps in the cycles are omitted from the text of the article.

The description of secondary sources of mercury into the cycle is not nearly sufficient, describing only briefly the vegetation, biomass burning and forest fires, but not going into detail on how these processes work, or on how they free mercury. There is minimal scientific description of the process at hand.

The article does sufficiently avoid jargon and is fairly clear, if terse. The article does link to additional Wikipedia articles.

Evaluating tone.

The article does not appear to have overrepresented viewpoints, again almost as a consequence of its terseness.

Evaluating sources.

Having checked the source on total annual mercury emissions, the source appears to be accurate, if slightly outdated (from 2010, though it is possible mercury emission has not changed substantially in the last decade). An article cited for the abundance of mercury in cinnabar does not obviously argue that cinnabar is the greatest mineralogical source of mercury, but this could be later in the text. One non-peer reviewed website, Geology.com, is cited again in the context of cinnabar. This is not a fatal flaw, but it would be preferable to have a peer reviewed article.

There are not obviously biased sources sourced, or noted.