Environment & Energy
Related: About this forumWidespread Atmospheric Tellurium Contamination in Industrial and Remote Regions of Canada.
The paper in the recent primary scientific literature that I will discuss in this post has the same title as the post itself. It is here:
Widespread Atmospheric Tellurium Contamination in Industrial and Remote Regions of Canada. (Jane Kirk et al, Environ. Sci. Technol., 2018, 52 (11), pp 61376145)
The first sentence of the abstract says it all basically:
The introductory text from the full paper states it more completely:
By the way, if you're concerned about the tellurium in solar cells - most likely you're not because you've heard again and again and again and again and again ad nauseum that solar cells are "green" - don't be. Although the toxicology of tellurium is real, particularly in acid exposure owing to the formation of H2Te gas, it's toxicology is dwarfed by the other component of "green" solar cells, cadmium.
The authors note that a planetary "tellurium cycle" has never been investigated to their knowledge, and so they set out to begin building one so at least in Canada.
They note that in seawater, the concentration of tellurium is on the order of 5-40 nanograms per liter, which is between two and three orders of magnitude smaller than natural concentration of uranium in seawater, generally taken to be 3.4 micrograms per liter.
This is because of the formation of iron and manganese nodules which enrich tellurium by a factor of 50,000 and drop it on the seafloor.
Thus when the world runs out of tellurium, given the extremely low - and thus environmentally suspect - energy to mass ratio of solar cells, cadmium telluride solar cells will lose their "renewable" status, if in fact, they ever had one.
Don't worry, be happy. Solar cells, as I've been hearing my whole adult life - and I'm not young - will save the world: Regrettably long after I, and all the people who have informed of this happy fact with such blithe confidence, will be dead.
The authors note that natural tellurium flows exist, primarily volcanoes and weathering of rocks with riverine transport, but that their estimates of anthropogenic sources effectively doubles the size of the flow:
They then describe their means of measurement:
The obtain sediment cores from the deepest parts of various Canadian Lakes, and date the cores by use of Cesium-137 (nuclear testing fallout).
The samples are microwave digested in hot aqua regia, a mixture of hydrochloric and nitric acid and analyzed using a modern Agilent 7700x ICP/MS.
The map in the paper gives a feel for the findings and the geography of the testing:
The caption:
Some results:
Te concentrations in lake sediment were generally steady and low (<0.020.07 mg kg1) in rural areas of Alberta (Battle, Pigeon; Figure 1a) and in the Athabasca Oil Sands region of Northern Alberta (both near oil sands industrial development: NE20, SW22, far from 2014-Y6A, and RAMP-271; Figure 1b). Near coal mining (post-1880) and combustion activities in Southern Saskatchewan near the city of Estevan (Figure 1c), sediment Te concentrations were only above detection limits after the advent of local, small-scale coal-fired generation (?1910). Increased sediment Te concentrations observed after ?1960 are coincident with the advent of larger generating facilities (950 MW).(28) Like fellow group 16 elements S and Se, Te is highly enriched in coal combustion aerosols (EF ? 104), particularly in the <2 ?m particle fraction (EF ? 106).(15,29) A decline in sediment Te seen in the ?1980s may reflect early experiments in carbon capture, facility downtime due to refurbishments, and capacity reductions due to insufficient cooling water (1988; major drought), which occurred during this period.(30) Overall, the Estevan Te record remains confounded by the high mass accumulation rates, which dilute atmospheric deposition, and incomplete characterization of the natural baseline (Figure 1c).
Near metal smelters at Flin Flon and Thompson, Manitoba anthropogenic atmospheric Te deposition is obvious (Figure 1d-g). At Flin Flon (Figure 1d), with >100-fold increases in Te concentration observed after the opening (1930) of the CuZn smelter. This facility was formerly Canadas largest Hg point source, and as seen for Hg,(19) there is a strong association between proximity to the smelter and higher sediment Te concentrations (Figure 1d, Figure S3). This is not unexpected as Te is often associated with the gold content of volcanogenic massive sulfide deposits mined near Flin Flon.(31) Moreover, world Te production is mainly a byproduct from copper refinery anode sludges,(2,3) with Flin Flon being one of the early producers of Te starting in 1935.(32) Using the method previously used for Hg,(19) we estimate the inventory of anthropogenically sourced Te deposited within a 50 km radius of the Flin Flon smelter at 72.2 t (see Figure S3) over its operational history (19302010). Other major copper refining centers in the world likely show similarly enhanced Te deposition surrounding them.
Twenty-five Flin Flon area mines have contributed ore containing 3.4 × 106 t of copper(33) to the smelter, yielding an emission factor of 21 g of Te atmospherically deposited near Flin Flon per t of Cu processed (72.2 t Te/3.4 × 106 t Cu = 21 g Te/t Cu). As net 19002010 global Cu production(34) (minus production from recycling) is 451 × 106 t, we estimate that 9,500 t of Te has been deposited near Cu smelters globally. As net global refined Te production(2) (19402010) is estimated at 11,000 t, Te emissions to air from Cu smelters is both a large source of Te contamination and a very large loss in potential Te production. This assumes the Flin Flon smelter process and the trace element composition of the Volcanogenic-Massive Sulfide (VMS) deposits exploited at Flin Flon are comparable to other 20th century Cu producers. This appears reasonable considering current information, which while limited indicates porphyry Cu deposits (dominant global Cu and Te source) have an equivalent Te content to VMS Cu deposits.(35)
Some measurement of the enrichment in the lake cores of various elements connected with mining:
The caption:
Average annual depositions into the Experimental Lakes Area, a remote region of Canada:
The caption:
Some conclusions from the paper:
The low apparent settling velocity for Te (similar to macronutrients; C, N, and P) despite its high particulate matter affinity(10,48) implies that some process(s) are acting within the aquatic environment slowing its apparent descent, possibly significant biological Te uptake and reprocessing. While Te is normally rare in the environment, it is highly toxic for most bacteria, with effects seen at concentrations 100× lower than required to produce toxic effects for more common elements of concern (Se, Cr, Hg, and Cu).(7) As Te utilization and potential human and environmental exposure has greatly increased in the past decade and is likely to increase further, it would be prudent to acquire a better understanding of Te interactions within the environment.
I'm not sure it would be "prudent." Couldn't we just declare solar cells "green" and forget about it?
Have a nice day tomorrow.
eppur_se_muova
(36,257 posts)When toxicity of Te in humans is discussed, it's usually in terms of acute toxicity, where, frankly, it doesn't seem so bad. The only occupations likely to result in tellurium exposure (various aspects of metallurgy) would seem likely to result in exposure to greater amounts of selenium, arsenic, and heavy metals as well, possibly masking any effects of chronic low-level exposure to Te. It appears the dangers of chronic Cd toxicity weren't appreciated until after it had claimed a number of victims. It would be a shame for the process to repeat itself with Te when such could be prevented. To some extent, I'm skeptical that will turn out to be the case, but then I wasn't expecting the high toxicity towards bacteria, either.
NNadir
(33,512 posts)...heavily on the chemical form.
The sulfur cogener of water, hydrogen sulfide, is very toxic, and hydrogen telluride is rather nasty, albeit not very stable in air. (Hydrogen selinide is a powerful lachrymator at low ppm levels.)
Potassium tellurate is very toxic, although several people, children, known to have ingested significant quantities and survived, possibly because it's a powerful emetic. An interesting artifact is that in these cases, the victims had a powerful odor of garlic for many months after the event.
A number of organotellurium compounds produce 100% mortality at fairly low levels in mice.
I personally made - a very long time ago - some sterically hindered phenotellerols as metal complexes. If I recall correctly - and it was a long time ago - this involved aromatic grignards reacting with elemental tellurium.
Last I looked, I'm still alive.
I don't expect that it's as toxic as the other component in the solar cells in which it is "distributed," to wit, cadmium, but I think it might well prove to be something like asbestos, a chronic toxin as opposed to an immediate toxin, a hazard to the workers who handle it.
There is some evidence that it inhibits the physiological mechanisms for the management of reactive oxidation species; if I recall correctly it may have some effect on superoxide dismutase, but I'm working from memory here.
Probably the toxicology of the element is so poorly understood because it's such a rare element, which calls into question what the word "renewable" actually mean.
I personally oppose the unrestricted distribution of products containing significant amounts of cadmium telluride, particularly since their lifetime before migrating to landfills is so short, even on a human time scale.
Cadmium selenide is only slightly less terrible. Selenium is a cool element, since it's one of those elements like copper that manages to be essential at one level and quite toxic at higher levels. It's a true "the dose makes the poison" example.
I once worked in a facility where people manufactured kilogram quantities of selenomethionine as a nutritional additive.
I generally stayed out of that lab when I could do so.