In the last trading session, U.S. stocks saw rough trading sparked by a slew of weaker-than-expected economic data out of China and Europe that sparked fresh worries over the world’s second-biggest economy and prospects of global growth. Among the top ETFs, investors saw SPY lose 1.8%, DIA shed 2%, and QQQ move lower by 2.4% on the day.Two more specialized ETFs are worth noting as both saw trading volume that was far outside of normal. In fact, both these funds experienced volume levels that were more than double their average for the most recent trading session. This could make these ETFs the ones to watch out for in the days ahead to see if this trend of extra-interest continues:VGSH: Volume 5.72 Times AverageThis short-term Treasury ETF was under the microscope as 4.8 million shares moved hands. This compares with an average trading day of roughly 913,000 shares and came as VGSH added 0.05% in the trading session.The movement can largely be blamed on protection from rising rates as short-duration bond ETFs are less vulnerable and act as a better hedge to rising rates. VGSH has added 0.4% in a month’s time and carries a Zacks ETF Rank #4 (Sell) with a Medium risk outlook.ACWX: Volume 3.11 Times AverageThis world ETF was in the spotlight as around 6.4 million shares moved hands compared with an average of 2.1 million shares a day. We also saw some price movement as ACWX lost 1.3% in the last session.The big move was largely the result of weak economic indicators that can have a big impact on global stocks like what we find in this ETF portfolio. ACWX has lost 3.7% over the past month and carries a Zacks ETF Rank #3 (Hold) with a Medium risk outlook.Want key ETF info delivered straight to your inbox? Zacks’ free Fund Newsletter will brief you on top news and analysis, as well as top-performing ETFs, each week. Get it free >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report SPDR-DJ IND AVG (DIA): ETF Research Reports VANGD-ST GOV BD (VGSH): ETF Research Reports NASDAQ-100 SHRS (QQQ): ETF Research Reports SPDR-SP 500 TR (SPY): ETF Research Reports ISHRS-MSCI ACWX (ACWX): ETF Research Reports To read this article on Zacks.com click here. Zacks Investment Research Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report