Chunlin Song 2018-02-03T04:38:16+00:00 The loss of permafrost carbon 2018-02-01T00:00:00+00:00 Chunlin Song Permafrost stores large amount of soil carbon that is vulnerable to climate warming. As the warming climate continues, thawed permafrost releases soil carbon in the form of carbon dioxide, methane, or dissolved carbon in fluvial networks. The carbon dioxide and methane, which are greenhouse gases, can potentially enhance the warming and degradation of permafrost. This positive permafrost carbon feedback are making the permafrost region a significant carbon source. Even though increased temperature and carbon dioxide (which is a fertilizer to plant photosynthesis) can make vegetation yield larger primary production, the accumulation of carbon by vegetation are much smaller than the loss of soil carbon. Part of the reason for that is warming environment can also enhance microbe activities, which can decompose organic carbon and release them to the atmosphere.

A recent study by Plaza et al. used a new equivalent ash mass method to quantify permafrost carbon loss in Alaska permafrost. The results show that the total permafrost soil carbon pool significantly declined with time at an average rate of 1.366 kg m-2 yr-1 over five years. That large losses overwhelmed increased plant biomass carbon uptake. Conversely, a study by Ding et al. showed increased soil carbon in Tibetan plateau permafrost region due to enhanced vegetation growth. The carbon loss in pan-arctic permafrost indicates a rapid changing carbon pool, which can be important factors to climate warming.

Reference: Ted Schuur (2016). Thawing Arctic tundra will likely speed up climate change for a century or more. The question is: How drastically? SCIENTIFIC AMERICAN.

Plaza et al. (2018). Rapid changes in the permafrost soil carbon pool in response to warming. unpublished paper.

Ding, J., Chen, L., Ji, C., Hugelius, G., Li, Y., Liu, L., … & Fang, K. (2017). Decadal soil carbon accumulation across Tibetan permafrost regions. Nature Geoscience, 10(6), 420.

Organic Carbon in Natural Waters 2017-12-28T00:00:00+00:00 Chunlin Song I read a book named Organic geochemistry of natural waters. I enjoyed reading this book very much. The following are some notes originally from the book.

  • Ground waters have 100 times more inorganic matter, while lakes and rivers have about 10 times more inorganic matter. Swamps, marshes, and bogs represent the other extreme, where organic matter is greater in concentration than inorganic matter.
  • Dissolved organic carbon varies with the type of water from approximately 0.5 mg/l for ground water and seawater to over 30 mg/l for colored water from swamps. Seawater has the lowest DOC with a median concentration of 0.5 mg/l, and ground water has a median concentration of 0.7 mg/l. Some pristine streams have low concentrations of DOC from 1 to 3 mg/l. Rivers and lakes contain more organic carbon and range in DOC from 2 to 10 mg/l. Finally, swamps, marshes, and bogs have concentrations of DOC from 10 to 60 mg/l and are cases where organic compounds dominate the water chemistry.
  • Large rivers carry substantial amounts of POC, and commonly POC is about one half the concentration of DOC. POC may equal DOC in the largest rivers and during times of high discharge. As the concentration of suspended sediment increases, so does the POC. Generally, POC makes up 2 to 3 percent of the sediment as coatings on mineral grains and as discrete organic detritus.
  • POC increase dramatically with increasing discharge, while DOC varies less.
  • DOC decreased with forest soil depth, O horizon 22 to 36 mg/l, A horizon 23 mg/l, B horizon 10 mg/1, the ground waters below the site had a DOC of 7 mg/l. Reason: biological decay and adsorption.
  • Generally, the combination of primary production of plant matter and decomposition rates control the amount of DOC in water. In general the transport of total organic carbon is approximately one percent of the net primary production, and this is reflected in a climatic effect on DOC.

Reference: Thurman E (1985). Amount of organic carbon in natural waters. Organic geochemistry of natural waters: Springer; p. 7–65.

Old Carbon in Arctic Rivers Utilized by Microbes 2017-01-03T00:00:00+00:00 Chunlin Song The thawing permafrost of the Arctic is releasing old carbon to fluvial systems. But the ancient carbon in the river water was undetectable because of microbes. Researchers found that the old dissolved organic carbon (DOC) is highly biolabile. Microbes can selectively “eat” the old DOC in a very short time.

Climate change has induced permafrost thawing in high latitude regions. It was hypothesis that ancient carbon is released from active soil layer to the river systems associated with permafrost degradation. However, many studies found more young DOC from high-order fluvial systems (downstream, like river mouth) from Arctic rivers. Can these results indicate the old carbon of the permafrost is less vulnerable? The answer is no. A study from the headwaters of Kolyma river found that microbial communities can use millennial-aged carbon (Mann et al., 2015). Mann et al. used bioincubation and carbon isotope analyses methods and shown that thaw stream DOC was utilized by microorganisms during short-term (28 days).

More information: Fellman, J. B., et al. (2014), Dissolved organic carbon biolability decreases along with its modernization in fluvial networks in an ancient landscape. Ecology, 95: 2622–2632. DOI:10.1890/13-1360.1.

Mann, P. J., et al. (2015). Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks. Nat. Commun. 6:7856 DOI: 10.1038/ncomms8856.

Spencer, RGM., et al. (2015). Detecting the signature of permafrost thaw in Arctic rivers. Geophys. Res. Lett., 42, 2830–2835. DOI: 10.1002/2015GL063498.

Vonk, J. E., et al. (2013). High biolability of ancient permafrost carbon upon thaw, Geophys. Res. Lett., 40, 2689–2693, DOI:10.1002/grl.50348.

Climate Control of Riverine Carbon Transport 2016-12-18T00:00:00+00:00 Chunlin Song Climate change is expected to alter the hydrological and biogeochemical processes of aquatic systems.

A 50-year of monitoring data in Finland shows that climate is a more important driver than forestry or acid position on riverine carbon fluxes (Lepistö, A. et al., 2014). Summer total organic carbon (TOC) concentrations were positively correlated with precipitation and soil moisture. While spring TOC concentrations were negatively correlated with max soil frost depth. Drought condition may also lead to higher TOC concentrations and fluxes in the coming years (1998-2000).

Similar results were found in other 30 boreal Finnish rivers (Mattsson et al., 2015). Seasonal variations of TOC were controlled by climate change and changing runoff regime. High fluxes of TOC were observed during rainfall or after snowmelt events, which led to a high flow of river channel.

In Mississippi River Basin, Dynamic Land Ecosystem Model (DLEM) shows that climate variability and extreme events (such as flooding and drought) were primary drivers of the seasonal and interannual carbon export variations (Tian et al., 2015). The maximum of carbon fluxes occurred in wet years.

As the climate keeps warming, the high-latitude regions are considered to be more sensitive to climate change. Thus riverine carbon export in such regions is dominated by climate factors. On the other hand, global climate change will increase the incidence of extreme events, which will significantly modify the riverine carbon transport process. The “pulse” and “shunt” of hydrological events may trigger a large amount of carbon release to aquatic systems (Raymond et al., 2016).

In conclusion, the climate impact on riverine carbon export exists globally. Not only in the sensitive zones, but also in general regions. Climate variations modify hydrological and biogeochemical cycles in different levels and patterns.

More information: Lepistö, A. et al. (2014). Almost 50 years of monitoring shows that climate, not forestry, controls long‐term organic carbon fluxes in a large boreal watershed. Global Change Biology, 20(4), 1225-1237, DOI: 10.1111/gcb.12491.

Mattsson, T. et al. (2015). Spatial and temporal variability of organic C and N concentrations and export from 30 boreal rivers induced by land use and climate. Science of the Total Environment, 508, 145-154, DOI: 10.1016/j.scitotenv.2014.11.091.

Raymond, P. A. et al. (2016). Hydrological and biogeochemical controls on watershed dissolved organic matter transport: pulse‐shunt concept. Ecology, 97(1), 5-16, 10.1890/14-1684.1.

Tian, H. et al. (2015). Climate extremes dominating seasonal and interannual variations in carbon export from the Mississippi River Basin. Global Biogeochemical Cycles, 29(9), 1333-1347, DOI: 10.1002/2014GB005068.

Human Activities and Riverine Carbon Flux 2016-12-02T00:00:00+00:00 Chunlin Song Human activities have greatly changed the exchange of carbon between different carbon pools. Riverine transported carbon is an important flux for carbon cycle accounting. Both anthropogenic and natural factors will affect the riverine export of carbon. Many studies have shown that human activities have a significant influence on the carbon flux of rivers.

Raymond et al. (2008) used a 100-year dataset from the Mississippi River to reveal the drivers of bicarbonate flux. The results showed that agricultural practices clearly increased the export of carbon and discharge of the Mississippi. The authors argued that anthropogenically landscape change is the main driver of inorganic carbon flux of the Mississippi.

A quantitive synthesis of published work estimated that anthropogenic perturbation such as deforestation, agricultural intensification, and the Sewage inputs may have increased the carbon fluxes from land to rivers by 0.2 petagrams per year (Pierre Regnier et al. 2013). Besides, these impacts by human also have led to old carbon release. A study performed by Butman et al. (2014) with global radiocarbon data demonstrated that the age of dissolved organic carbon in rivers positively correlated with population density and the proportion of human-dominated landscapes within a watershed. Human disturbance has introduced the aged carbon to the modern carbon cycle.

Different results were found in China, which is a country that has undergone maybe the most drastic land use change in the world for the past decades. Wang et al. (2015) used 60 years of runoff and sediment load data from the Yellow River over China’s Loess Plateau (which is the source of nearly 90% of Yellow River’s sediment load). The results show that landscape engineering, terracing, dams and reservoirs trapping, and large-scale vegetation restoration projects significantly reduced the sediment load. Although it is not about the carbon transport, I guess the results have strong implications on carbon flux since the sediments and carbon fluxes in river channel are generally positively correlated with each other. Song et al. (2016) analyzed a dataset among Chinese river and concluded that human activities like dam construction and vegetation restoration in recent decades have a greater influence than climate on the transport of riverine carbon across China.

Summing up, human activities have drastically perturbed riverine carbon cycle by increasing or decreasing carbon fluxes in the rivers. They must be considered in carbon cycle accounting and will only be more important in a changing world.

More information: Raymond, P. A. et al. (2008). Anthropogenically enhanced fluxes of water and carbon from the Mississippi River. Nature, 451(7177), 449-452, doi: 10.1038/nature06505.

Regnier, P. et al. (2013). Anthropogenic perturbation of the carbon fluxes from land to ocean. Nature Geoscience 6, 597–607, doi:10.1038/ngeo1830.

Butman, D. E. et al. (2015). Increased mobilization of aged carbon to rivers by human disturbance. Nature Geoscience, 8(2), 112-116, doi:10.1038/ngeo2322.

Shuai Wang et al. (2016). Reduced sediment transport in the Yellow River due to anthropogenic changes. Nature Geoscience 9, 38–41, doi:10.1038/ngeo2602.

Chunlin Song et al. (2016). Control factors and scale analysis of annual river water, sediments and carbon transport in China. Scientific Reports 6, 25963; DOI: 10.1038/srep25963.

Water Erosion affect Carbon Sink 2016-07-29T00:00:00+00:00 Chunlin Song Erosion-affect-Carbon-Sink Water erosion plays an important role in lateral soil carbon transport. This knowledge is easy to understand. However, a recent study conducted in conterminous China shows that water erosion also significantly affect the vertical CO2 fluxes. The paper entitled Lateral transport of soil carbon and land−atmosphere CO2 flux induced by water erosion in China was published on PNAS.

The land of China is suffering water erosion for a long time, which caused 180 ± 80 Mt C⋅y-1 of soil organic carbon transport during the last two decades according to the study. Yue et al. estimated the erosion-induced land−atmosphere CO2 fluxes with national soil surveys on erosion rates. By comparison the difference between CO2 emissions before and after erosion, Yue et al. concluded that the erosion-induced carbon sequestration of atmospheric CO2 is about 45 ± 25 Mt C⋅y-1, which is equivalent to 8–37% of the terrestrial carbon sink in China. Additionally, the study shows the mountainous regions in China are the “hotspots” of carbon sink.

This study highlights the water erosion on carbon sink, and also allow us to achieve better understandings of terrestrial carbon accounting. It’s very inspiring and interesting that water erosion will cause carbon sequestration. Erosion is not as bad as we thought before, at least it brings significant carbon sink.

More information: Yue Yao et al. (2016). Lateral transport of soil carbon and land− atmosphere CO2 flux induced by water erosion in China. Proceedings of the National Academy of Sciences, 113(24), 6617-6622, doi: 10.1073/pnas.1523358113

Organic Carbon Decomposition Correlated with WRT 2016-05-26T00:00:00+00:00 Chunlin Song Nature Geoscience have published an interesting paper entitled Organic carbon decomposition rates controlled by water retention time across inland waters. The main conclusion of this paper is that the decomposition rates of organic carbon in water are negatively correlated with water retention time (WRT). The half-life of organic carbon in inland waters (2.5 ± 4.7 yr) is shorter than terrestrial soils and marine ecosystems. This work is very inspiring, which would be helpful to my Ph.D. work.

The organic carbon in terrestrial soils was transported to oceans through rivers, which is an important component of global carbon cycle. However, the decomposition rates of organic carbon are largely unknown. The quantity of organic carbon mineralized and released to the atmosphere during its transport is unclear. That’s why we need to investigate the factors that control organic carbon decomposition rates.

Catalán et al. compiled 315 measurements of organic carbon decay rates, which include filed studies from the globle scale and bioassay studies. With ordinary least squares correlation analysis, they obtained the relationship between WRT and organic carbon decomposition rates:

\(logk = -4.5 (\pm 0.08) log WRT − 0.96 (\pm 0.03) (r^{2} = 0.41; p < 0.001; n = 315)\)

where k is the organic carbon decomposition rates (sensitive to the effect of temperature), WRT is the WRT (the ratio of the mass of a scalar in a water body to the rate of renewal of the scalar). This model indicates that the longer the WRT, the lower the organic carbon decomposition rates.

In addition, the authors calculated the concomitant changes in WRT of water body in a 2 degrees warmer world. The estimated future redistribution of the organic carbon decay rates shows a decrease in the Mediterranean biome (around −13%) and an increase in the boreal and tundra biomes (around 10%).

More information: Núria Catalán et al. Organic carbon decomposition rates controlled by water retention time across inland waters. Nature Geoscience 9, 501–504 (2016), doi:10.1038/ngeo2720.

Young Water Fractions of Global Rivers 2016-03-29T00:00:00+00:00 Chunlin Song Recently, a paper entitled Substantial proportion of global streamflow less than three months old was published by Nature Geoscience. Jasechko et al. shown that about 1/3 of global streamflow are young water, as defined in the paper, 2.3 ± 0.8 months.

The foundation of this study is based on two newly published companion papers in the journal Hydrology and Earth System Sciences by James W. Kirchner. James criticized the traditional approach of using seasonal cycles in chemical or isotopic tracers to estimate mean transit time (MTT) of stream water. He proved in his long papers with mathematics deduction that these calculations are mostly wrong by several hundred percent because of aggregation bias. So where can we go next? While, James proposed an alternative storage metric, the young water fraction (Fyw). Fyw is a better metric than MTT because Fyw can be accurately estimated from the amplitude ratio of seasonal tracer cycles in precipitation and runoff within a precision of a few percent. Fyw has much less uncertainty than the MTT thus more reliably for the heterogeneous real world catchments.

Jasechko et al. compiled a global precipitation and streamflow isotope database which includes 254 rivers. With solid methodology by James W. Kirchner, they conducted periodic regression analyses with the isotope data to get \(\delta\)18O cycle amplitudes of precipitation and streamwater. After that, they calculated the (Fyw) of each catchment by dividing the river \(\delta\)18O cycle amplitude by the precipitation \(\delta\)18O cycle amplitude. Also, according to the paper, there is a negetive relationship of young water fraction and catchment topographic gradient.

The time spent by river water is crucial for predicting the retention, mobility and fate of solutes, nutrients and contaminants. This study tells us that young streamflow represents roughly one-third of global river runoff. It means even watersheds with long MTT can transmit substantial fractions of soluble contaminant inputs to aquatic systems in very short time spans. Besides, the rivers of plain areas may have more young water than the rivers in mountainous areas. Since young water are mainly derived from a thin layer at the top of the aquifer, this paper conclude that the small fraction of continental aquifer will have disproportionate influence on stream water quality.

More and more deep groundwater is likely to be extracted for expanded population, I’m wondering will this change the young water fraction? Since we already know the older water fraction (one minus Fyw, older than three month) of global river, what are the age composition of the old water fraction? What is the fraction of older water over one year or ten years old? Where is the older water come from? To what extent the older water impact water quality?

More information: Kirchner, J. W. Aggregation in environmental systems – Part 1: Seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments, Hydrol. Earth Syst. Sci., 20, 279-297, doi:10.5194/hess-20-279-2016, 2016.

Kirchner, J. W. Aggregation in environmental systems – Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity, Hydrol. Earth Syst. Sci., 20, 299-328, doi:10.5194/hess-20-299-2016, 2016.

Scott Jasechko et al. Substantial proportion of global streamflow less than three months old. Nature Geoscience 9, 126–129 (2016), doi:10.1038/ngeo2636.

Culture difference between Australia and UK 2016-03-10T00:00:00+00:00 Chunlin Song This post is based on a lecture by Elina Gordon. She works in the Department of Foreign Languages of UCAS as an international instructor.

Australians and English speak the same language, but until today, after listening to Elina Gordon’s speech did I know that the two countries have so much differences. Not only the way they speak, but also many other culture difference between Australia and UK.


Generally, Australian English is more informal and simple than British English. For example, Australians frequently corrupt the language via the use of diminutives such as “uni” instead of “university” or “Oz” instead of “Australia”, it’s unbelievable. Many daily language are simplified in Australia. In England people say “cup of tea”, while in Australia people just say “cuppa”; “black coffee with hot milk” in England become “flat white” in Australia.

Some words have different meanings in the two countries. For example, pants mean trousers in Australia, but it means underwear in UK.

Not only between countries, but different places inside UK have different way to speak English. People in London and Edinburgh have different accents and local dialects. Just like different provinces in China all speak Chinese, but people from north China cannot understand the Chinese from south China people.

Aside from pronunciation, Australian English has been heavily influenced by American English. Most of Australia’s television shows are American and American research dominates Australian universities. Consequently, Australians often use the American spelling for words such as organization. They use both American and English grammar. For example, both the American “the couple is happy” and the British “the couple are happy” are acceptable in Australia.


Since the climate in UK is not proper for agriculture, many foods in UK depend on import. I guess because the food is precious, so the English people cook them very carefully to protect it. That’s why the food in UK is awful. As Elina said, the foods of UK “have no flavor”. In spite of this, Elina highly recommended Scottish deep fried food, she love the deep fried haggis and chips very much.

During the colonial era, the staples of Australian colonial society were wheat, potatoes, beef, milk, eggs, sheep as well as fish and chips. These staples were English staples. Outside of colonial society, Aborigines ate kangaroo, echidna, koala, ants, grubs, snakes, lizards and moths. Because the colonists were starving, they would have eaten the native Australian cuisine if they could, but they didn’t know how to hunt or find it. Furthermore, native produce was not suitable for farming so it could only sustain people living a nomadic existence.

In the last couple of decades, both Australia and England have gained greater access to a diverse range of produce and have had migrants introduce varied recipes of the world. Consequently, both Australia and England have developed fusion cuisines. But foreign recipes always change in UK. As a consequence, Chinese food is not Chinese style; Italian food is also not Italian style. They just changed to satisfy the English taste. By contrast, foreign foods keep their true colors when they migrate to Australia. So we can have really authentic Chinese food in Sydney.


Australian soaps like Neighbors and Home & Away are immensely popular in England. They portray happy neighborhoods populated by good looking teenagers and their loving families. The soaps might appeal because they fit an idealized conception of Australia for the English. For instance, the weather in the Australian TV shows are always looks graceful, but the weather in England are cloudy, chilly and rainy all the time. So the shows provide a beautiful world that English never could have. Alternatively, maybe the episodes are well written. On the contrary, as Elina said, Australian don’t like the shows, they will never tell their native friends they like it.

While Australian programs have been popular on English television, not many English programs are popular on Australian commercial television. For reasons unknown, commercial television in Australia favors American-made programs. However, the government-funded ABC has often showed English programs such as The Bill, Black Adder, Mr. Bean, The Goodies, Dr Who and Little Britain.


Both Australia and UK hate USA, but they don’t refuse to make friends with Americans. They just don’t like the country as a whole; Australia and UK have the same Queen, but their attitudes to the Queen differ; universities of the two countries exchange their students frequently.

The differences between Australia and UK are a good thing, which makes our world more colorful and interesting. There are over 200 countries on this planet; I cannot imagine how many differences between cultures and peoples from these countries. A multicultural world is more beautiful than a single culture world. Cultural differences should be an opportunity to communicate. Actually, people everywhere have much in common, such as a need for affiliation and love, participation, and contribution. When the exterior is peeled off, we are the same.

What Makes Good Writing 2016-02-24T00:00:00+00:00 Chunlin Song When I was a high school student, I thought good writing equals to rhetoric. If I write an essay with beautiful words and expressions, that is an excellent essay. Under this prejudice, my essays looks like beautiful but useless. Too many needless words and expressions makes my writing awful.

After graduated from college, I became a graduate student in the University of the Chinese Academic of Sciences. Then I started take writing seriously. I start a blog and write blog posts frequently. I also publish some of my most satisfying work on Jianshu, I earn a lot of “like” there. This means a lot to me, as a new blogger. I got confidence on writing. What’s more, I understand what makes good writing.

Good writing based on logical thinking. In order to write clearly, I must think clearly and logically. Chaotic logic will make readers confused, that kind of writing is terrible. Here is my trick to write clearly. Every time before I writing, I will think about the big picture of the essay I’m going to compose. I list the ideas as skeleton, then fill the flesh. In this workflow, my works are basic qualified.

Good writing needs patient revision. Unless you are a genius, you cannot write well without revision. Most of us are ordinary people, we make mistakes while writing. To eliminate the flaws, we must revise after finish writing. Check the logic to see if it’s effective. Read the sentence to see if you used the right words. Add necessary ideas you ignored when you were writing.

Good writing needs hard work. Everyone can obtain writing skills through persistent practice. This practice consists two parts: reading and writing. Reading enlarges our scope of knowledge; give us inspiration and materials to write. Only jump into swimming pool can we learn to swim. Writing follows the same rule. Good writer practice over and over.

With hard work, patient revision and logical thinking, I believe my writing ability will be improved.