我想指定列的宽度，同时保持内容居中。我该怎么做？
这是我的代码
\begin{tabular}{p{6cm} c c p{2cm} p{3cm}}
\Xhline{3\arrayrulewidth}\hline
Location& Tailings& Years& Dominant metal or mineral& Source\\
\midrule
Freda-Redridge, Keweenaw Peninsula, Michigan, U.S.A.& 39.2 Tg& 1901-1947& Copper& Kerfoot et al. 2009\\
Gay, Keweenaw Peninsula, Michigan, U.S.A.& 22.5 Tg& 1901-1932& Copper& Kerfoot et al. 2009\\
Silver Bay, Minnesota, U.S.A.& 500 Tg& 1955-1980& Iron& Cook et al. 1974\\
Rupert Inlet, British Columbia, Canada& 353 Tg& 1971-1995& Copper& Burd 2002\\
Britannia Beach, Howe Sound, north of Vancouver, British Columbia, Canada& 44 Tg& 1904-1974& Copper, zinc& Chretien 1997\\
Ensenada Chapaco Bay, north-central Chile& 2,612,103 kg d$^{-1}$& 1978-1994& Iron tailings (pelletization)& Lancellotti and Stotz 2004\\
Chanaral Bay, Atacama Region, Chile& 150 Tg& 1938-1974& Copper, arsenic& Castilla and Nealler 1978; Andrade et al. 2006\\
Qaumaujuk and Agfardlikavsa Fjords, Greenland& 11.8 Tg& 1973-1990& Lead, zinc, silver& Asmund et al. 1994\\
Rize, Black Sea, Turkey& 2,880,103 kg d$^{-1}$& 1994-2000& Copper, arsenic, lead& Berkun 2005\\
Chameis Bay, Namibia, Africa& 366 Tg& 1970-2006& Diamonds& Smith 2006\\
Elizabeth Bay, Namibia, Africa& 7 Tg& 1991-1998& Diamonds& Smith et al. 2002\\
Calancan Bay, Marinduque Island, Luzon, Philippines& 200 Tg& 1975-1991& Copper& Marges et al. 2011\\
Buyat Bay, North Sulawesi, Indonesia& 1,841,103 kg d$^{-1}$& 1996-present& Gold& Edinger et al. 2008\\
Toga, Melanesia, Western Pacific& 2.5 Tg yr21& 1990s& Phosphate; Cd, Pb, Cu in tailings& Gnandi\\
\bottomrule
\end{tabular}
\label{T5C3}
\end{table}
\end{spacing}
\end{landscape}