China's sulfur benchmark fell 10.1 percent between October 9 and October 17 as the post-holiday market absorbed heavier coastal stocks and weaker phosphate-chain demand.
Shengyishe put its national benchmark at 7,402.33 yuan per metric tonne on October 9, down 3.89 percent on the day, then printed 6,652.33 yuan at the October 17 close. The eight-day loss was 750 yuan per tonne.
The Shandong refinery board moved with the benchmark. Shengyishe reported Dongming liquid sulfur at 6,400 yuan per tonne and solid sulfur at 7,300 yuan on October 15, cuts of 350 yuan and 500 yuan respectively from the previous postings.
Supply arriving at the coast gave buyers room to wait. Shengyishe's October 15 tally put monitored port stocks at 1,123,500 tonnes, up 103,800 tonnes from 1,019,700 tonnes on October 8, with Zhanjiang rising to 360,000 tonnes from 260,000 tonnes.
The correction spread into acid. SunSirs put China's industrial-grade 98 percent sulfuric acid reference at 1,557.50 yuan per tonne on October 17, down 120 yuan, or 7.2 percent, from 1,677.50 yuan on October 14. Shengyishe separately quoted Shandong Jincheng's 98 percent acid at 1,460 yuan per tonne on October 9 while its 250,000 tonne-a-year unit was stopped for maintenance.
Middle East monthly contracts had already turned lower into the period. Shanghai Metals Market's October 8 producer notice put QatarEnergy at 835 dollars per tonne FOB and Kuwait Petroleum Corporation at 820 dollars, both down 45 dollars month on month, while ADNOC set 890 dollars FOB Ruwais, down 70 dollars.
Vancouver followed the seaborne correction during the week. ChemPriceHub's October 16 open market roundup reported transactions at 830 to 840 dollars per tonne FOB, down 50 dollars on the week, and said at least two vessels left Vancouver for Santos during October.
The same roundup quoted Vancouver-origin material at 880 dollars per tonne CFR Indonesia early in the week, with November shipments trading near the upper end of buyer indications at 850 to 870 dollars. Those cargo points show Canadian tonnes pressing into markets where Gulf suppliers were also cutting offers.
Alberta's physical buffer remains large but is drawing. The Alberta Energy Regulator's ST3 file, run September 28, put August closing sulfur inventory at 11,042,851.4 tonnes, down 66,759.5 tonnes from July, with August production at 328,937.3 tonnes and removals from Alberta at 178,425.2 tonnes.
The Atlantic contract book is moving on a slower clock. Green Markets' public October 16 index said fourth-quarter Tampa molten sulfur negotiations remained unsettled, leaving the confirmed third-quarter contract at 705 dollars per long ton as the current public anchor.
For fertilizer buyers, the immediate change is a lower replacement-cost signal from China, Vancouver and the Gulf producer contracts while Tampa waits for a quarterly settlement. Acid's 120 yuan fall over three sessions also shows weaker sulfur costs reaching a downstream feedstock used across phosphate and industrial markets.
The North American read is a faster Pacific repricing against an Alberta stockpile that fell modestly in August. Vancouver cargoes are clearing at lower levels as Chinese inventories rise, while Tampa buyers still face the 705 dollar third-quarter liquid benchmark.