Shanghai Metals Market published its sulphuric acid weekly review for the week ending September 18 on Thursday, anchoring China's copper smelting acid index at 1,351 yuan per metric tonne.
The index was down 67 yuan or 4.7 percent versus the prior Friday close of 1,418 yuan in the open table.
The week began with a 43 yuan decline on September 15 before flat to slight adjustments through the balance of the period.
Shanxi smelting acid fell a further 330 yuan per tonne on September 15 in the same release, extending regional weakness beyond Shandong sulphur-burning units.
Shandong elemental sulphur EXW was quoted at 7,257 to 7,650 yuan per tonne, averaging 7,453.5 yuan, down 575 yuan or 7.2 percent week on week.
That elemental move aligns with Shengyishe's September 18 national benchmark at 7,685.67 yuan per tonne, down 0.24 percent on the day and 7.95 percent month to date from the September 1 open.
Middle East FOB sulphur averaged 855 dollars per tonne flat in SMM's sulphur table while CIF Indonesia averaged 1,005 dollars per tonne, down 20 dollars from the prior week.
CFR India was cut 25 dollars to an average near 1,050 dollars per tonne from 1,075 dollars, matching the lower end of ranges BC Insight and SunSirs have quoted for India and granular China imports.
Asia sulphuric acid FOB Korea averaged 300 dollars per tonne in a 280 to 320 dollar band, FOB India averaged 325 dollars in a 300 to 350 dollar band, and CFR Indonesia averaged 315 dollars.
MAP and DAP margins remained inverted in SMM's fertilizer commentary while autumn procurement lagged, echoing demand-destruction themes in US phosphate reporting the same day.
UkrAgroConsult cited Mosaic running near 50 percent rates in Florida and Louisiana as Tampa delivered sulfur stayed above 1,100 dollars per tonne since May.
For Alberta desks, acid weakness in Shanxi and smelting indices does not restore Middle East seaborne tonnes while Hormuz backlogs near 600,000 tonnes on thirteen vessels in BC Insight's September 18 count.
Vancouver FOB sulphur firmed to 1,100 to 1,200 dollars per tonne on a confirmed Southern Africa sale in BC Insight Price Trends, supporting Pacific netbacks even as Chinese domestic indices fall.
Desk read: SMM week-ending 18 September is a coordinated down week for elemental and acid in China with fertilizer demand still soft. Watch whether smelting acid can hold 1,350 yuan if Shandong EXW stabilizes near 7,450 yuan.