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Sat Jun 24, 2017, 10:38 AM

Fast, accurate determination of cadmium contamination without expensive instrumentation.

According to the comprehensive survey of health risks to which I often refer for a qualitative assessment of environmental risks, A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 19902010: a systematic analysis for the Global Burden of Disease Study 2010 (Lancet 2012; 380: 222460), occupational exposure to cadmium was killing 555 people per year as of 2010, up from 288 people per year in 1990.

The trend suggests that the the death toll may be higher as of 2017 than it was in 2010.

The annual death toll for cadmium exposure, of course, is much greater by two orders of magnitude than people killed by Fukushima, but nobody cares, since the solar industry, one of the largest users of cadmium, often in combination of two other highly toxic elements, selenium and/or tellurium, is "green," and nuclear energy, um, isn't. That's the common perception anyway, completely irrational, but common.

Twenty or thirty years from now, all of the "green" solar cells on this planet will be ready for landfills, although undoubtedly some inoperative examples of this "green" technology will just rot on the roofs on which they were installed, ultimately leaching their contents. Future generations, who are already doomed to pay for our generation's environmental ignorance anyway, will have a much worse risk from cadmium exposure than we do, since cadmium has been distributed to make distributed energy, a very, very, very, very bad idea, but one which is popular, completely irrational, but popular.

With this in mind, I found the following paper in the June issue of ACS Sustainable Chemistry and Engineering to be quite interesting:

ACS Sustainable Chem. Eng. 2017, 5, 4976−4981

The authors, Tianxiang Wu, Jiao Shan, and Zhanfang Ma, are Chinese, which is appropriate because much of the world's cadmium in mined in China. According to a study conducted at Nanjing University in 2007, 10% of the rice crops surveyed in six agricultural regions were contaminated with cadmium. (cf: Lancet 2013; 381: 204453)

Unfortunately, the best current approach to analyzing for cadmium contamination, is to use ICP/MS or ICP/MS/MS, instruments that are expensive to purchase and expensive to operate, usually employing a highly trained analytical chemist to run and interpret the device. This is especially true for complex matrices like soil, rice, and flowerbeds exposed to rain runoff from roofs with old "green" solar cells on them. If one is interested in the speciation of cadmium, one must also utilize a chromatographic system generally.

Wu, Shan and Ma's paper is involved with developing a simple, instrument free, and cheap way to detect and quantify cadmium without the use of expensive instrumentation.

First I'll refer to the author's introductory paragraph describing the hazards of cadmium exposure:

Cadmium is widely used in many fields such as electroplating, agriculture, metallurgy, and so on. However, as a heavy metal ion, Cd[sup]2+[/sup] is extremely toxic and carcinogenic, and excessive intake of Cd[sup]2+[/sup] can damage the liver and kidneys and increase the risk of cardiovascular diseases and cancer mortality.1,2Nowadays, numerous analytical techniques for the detection ofCd[sup]2+[/sup] have been developed, including atomic absorptionspectroscopy,3−5 atomic fluorescence spectrometry,6,7 colorimetricassay,8−11 inductively coupled plasma atomic emissionspectroscopy,12 inductively coupled plasma mass spectrometry,13,14 X-ray fluorescence,15 surface enhanced Ramanscattering,16 and electrochemistry.17,18 Although these methods offer excellent sensitivity and selectivity, sample pretreatment can be time-consuming, and expensive instruments are commonly involved. While colorimetric methods19−23 forCd[sup]2+[/sup] detections have been developed to overcome such disadvantageous, the methods are not sufficient for real-world applications.

The chemistry of the colorometric test employed by the authors utilizes gold nanoparticles, and exploits the capability of gold cadmium alloys to catalyze certain reactions (reduction by sodium borohydride) that change the color of a dye toluidine blue O. Since the amount of gold is so small as to be invisible, the price of gold is trivial to the preparation of analytical kits.

The test is said to be as sensitive as electrochemical testing, having an LOD (limit of detection) of roughly 30 nM (nanomolar), not as sensitive as ICP/MS, but sufficient to identify concentrations of concern. The linear range of quantification is 30 - 480 nM, and in cases where the linear range is exceeded, quantification can be accomplished by serial dilution.

This sort of thing is likely to be important to future generations, especially as we are in an unending race to insure their impoverishment.

Interesting I think, and slightly encouraging since it will help to address an unavoidable bad situation for the current residents of China, who are enduring all sorts of things so Americans can "go green" and future generations who will need to clean up - to the extent they have resources to do so - our mess.

Enjoy the weekend.

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Reply Fast, accurate determination of cadmium contamination without expensive instrumentation. (Original post)
NNadir Jun 2017 OP
eppur_se_muova Jun 2017 #1
NNadir Jun 2017 #2
kristopher Jun 2017 #4
hunter Jun 2017 #3

Response to NNadir (Original post)

Sat Jun 24, 2017, 06:29 PM

1. Wow, I really hadn't kept up with this ...

I was pretty astounded to realize CdTe had become so widespread. Neither Cd nor Te is all that scarce, but neither is all that common, either, and with the toxicity of Cd (plus that fact that some versions added HgTe) I assumed interest would wane. I know a couple of companies dropped all reasearch in CdTe because of the toxicity issues. But if you're going to develop it in China .... well, that's another story, innit ? No lessons learned from the experience of Toyama prefecture.

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Response to eppur_se_muova (Reply #1)

Sat Jun 24, 2017, 09:44 PM

2. The most recent issue of EST reports that 65% of the rice in Southern China exceeds Chinese Cd...

..."safety" limits, which are 20 micrograms per gram.

I just saw it this afternoon after posting the OP.

Here it is: Li et al, Environ. Sci. Technol., 2017, 51 (12), pp 67566764,
"Applying Cadmium Relative Bioavailability to Assess Dietary Intake from Rice to Predict Cadmium Urinary Excretion in Nonsmokers"

Here's the text from the opening paragraph, which is very, very, very, very disturbing:

"Cadmium is a ubiquitous environmental pollutant, posing a threat to human health. Due to rapid industrialization and urbanization, China faces challenges of soil contamination with heavy metals. Recent national survey shows that 19.4% of agricultural soils is contaminated, with Cd being the prioritycontaminant.1 Epidemiological studies have shown the association between prolonged chronic low Cd exposure and cardiovascular disease, decreased bone density, and cancer.2,3 In addition, higher exposure may result in renal damage, proximal tubular reabsorptive dysfunction, and fractures of long bones in the skeleton.4,5

Among different pathways, smoking is an important contributor to Cd exposure in smokers, whereas dietary intake is the primary contributor for nonsmokers. In China, recent studies showed elevated Cd concentrations in dietary staples, including rice, wheat, and vegetables due to anthropogenic impacts on farmland soils and/or alternative cultivation practices...6"

Here's the graphic from the intro, reproduced in the text.

The heat map refers to urinary concentrations in Chinese human beings as analyzed by the researchers.

The figure for contaminated farmland in that huge country is truly astounding, just shy of 20%.

As for reluctance on the part of the solar industry to distribute cadmium telluride widely all over the planet, apparently only some of the researchers had the guts and humanity to restrain themselves from using it. It is now commercially being distributed, and has been distributed including on the street on which I live.

All of the "First Solar" solar cells stupidly installed by PSGE on telephone poles in NJ are CdTe monsters.

It is a matter of some irony that on my block of all places - since I find the entire solar enterprise to be ill thought out, short sighted, dangerous and useless - that one of them was ripped off a telephone pole during Hurricane Sandy and bent and broken. It sat there for several months, untouched, until someone finally came and hauled it away.

This for me is evidence of what will become of this crap when it fails, and be sure, it will fail. They hand out all kinds of bullshit about how they will recycle this toxic crap, but it's just that, bullshit. Future generations will bear the consequences of this dubious scam - which has proved completely useless in addressing climate change - and our farms, water supplies, grain etc, will face the same fate as China's.

Several years back, I confronted David Eaglesham on this point in the Q&A after his talk at the Andlinger Center for Energy and the Environment. He had just been fired from his position as the Chief Scientific Officer at First Solar. His response was unsatisfying, which was, to paraphrase, "Cadmium is mined anyway to obtain zinc, so, it's OK if we distribute it widely."

Solar companies all around the world are failing or are in dire economic straits. Almost none of the current purveyors of this bad idea will be financially solvent enough to clean this crap up, and if some are, they'll fight like hell any legal attempt to make them pay for the clean up.

highlight seminar series: 2011-2012 speakers/dates announced.

Thank you for relating the story of the Toyama prefecture. I wasn't aware of it.

This is even more evidence that the solar industry will never be as safe, as effective, as reliable and as sustainable as the nuclear industry.

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Response to NNadir (Reply #2)

Sun Jun 25, 2017, 05:10 AM

4. About 75% of cadmium used goes to NiCd batteries.

Flow of Cadmium from Rechargeable Batteries in the United States, 1996-2007

By David R. Wilburn


Cadmium metal has been found to be toxic to humans and the environment under certain conditions; therefore, a thorough understanding of the use and disposal of the metal is warranted. Most of the cadmium used in the United States comes from imported products. In 2007, more than 83 percent of the cadmium used in the United States was contained in batteries, mostly in rechargeable nickel-cadmium batteries used in popular consumer products such as cordless phones and power tools. The flow of cadmium contained in rechageable nickel-cadmium batteries used in the United States was tracked for the years 1996 to 2007. The amount of cadmium metal contained in imported products in 2007 was estimated to be about 1,900 metric tons, or about 160 percent higher than the reported cadmium production in the United States from all primary and secondary sources. Although more than 40,000 metric tons of cadmium was estimated to be contained in nickel-cadmium rechargeable batteries that became obsolete during the 12-year study period, not all of this material was sent to municipal solid waste landfills. About 27 percent of the material available for recovery in the United States was recycled domestically in 2007; the balance was discarded in municipal solid waste landfills, exported for recycling, retained in temporary storage, or thrown away.

Most of the agricultural contamination is from cadmium's presence in phosphorous containing fertilizers (about 100mg/kg of phosphorus).

And as for your boogyman, CdTe panels are less than 5% of the solar market.

More on: Perovskite materials for solar, and more
Perovskite materials are emerging as a promising alternative in solar cells to silicon, thin-film cadmium telluride and thin-film cadmium sulphide (CdTe/CdS).

In 2013, Science magazine listed perovskite among the top 10 breakthroughs of the year. This was no coincidence because perovskite is a highly promising material for the solar power industry.
Its efficiency levels have already reached 22.1% and continue to increase, while it is very easy to obtain thin films of these OHPs, just from solutions in conventional organic solvents.
These perovskites in general are full of riddles and mysteries. They have such a unique crystal structure, making it possible to obtain variety of unconventional physical properties I already mentioned the best high-temperature superconductors (in Ba-based inorganic perovskites).
Their structure is so diverse that it offers many other useful properties, including ferroelectricity and non-linear optical activity. If we compare our particular OHP hybrid perovskites with inorganic superconductors, we can see that this material functions in a rather unusual manner, as far as photovoltaics are concerned. Charge carriers live too long and travel too far, after they are photo-generated by light.
And it is still not clear why they can be so easily separated maybe because of tiny internal electric fields, created by organic electric dipoles of CH3NH3 methylamine, or because of ions of iodine, moving in a certain way. All this questions still waiting their resolution, which creates an exciting challenge for researchers.
It has already been proved that perovskite solar cells can surpass currently available silicon-based solar batteries in terms of their efficiency, and that they can probably catch up with gallium arsenide quite soon. Scientists continue to increase their efficiency, to develop ever new methods for obtaining materials. They continue to improve the properties of thin films, but no one can explain their impressive performance for the time being.
There is no need to use rare-earth or other precious metals for making perovskite-based solar cells. Perovskite panels are made using a low-temperature process and inexpensive ordinary-salt solutions known for their low production costs. A 6W perovskite solar battery measuring 15 x 20cm costs about $3....

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Response to NNadir (Original post)

Sun Jun 25, 2017, 12:23 AM

3. Cadmium has a half life of...

...FOREVER, and a biological half life of 38 years.

Suck that, future generations.

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