e., an inheritance. Although this leaves open the possibility that “legacy sediment” simply refers to something from the past, all sediment results from past processes, so legacy sediment would be redundant in that sense. Thus, when the phrase LS is used without definition or contextual explanation, a more specific meaning is implied. In general, an anthropogenic origin may be implicit, JQ1 order given the definition

of legacy as something ‘from an ancestor or predecessor;’ i.e., it may logically follow that human agency was involved. In this sense, and building upon recent usage of the term, LS resulted, at least in part, from anthropically accelerated sediment production. Although “legacy” has been used in different contexts

to describe naturally produced sediment; e.g., a legacy of climate change, the phrase, LS, by itself should be used to imply that humans played a substantial role in the processes that generated the sediment. Definitions that have been given for LS vary but usually indicate a post-colonial age of alluvium in North America (e.g., Niemitz et al., 2013). Many questions about the specific source, physical character, extent, or location of LS have not been addressed. For example, does the definition of LS apply narrowly to agriculturally derived alluvium, or does it include other land uses such as logging and mining? Does it include colluvium on hillslopes and fans? Is LS defined by its lithologic or chronologic characteristics? Roxadustat in vivo If LS is a lithologic unit, is it restricted to the anthropogenic component of the sediment or is the diluted mass considered to be a LS deposit as a whole? Since LS is usually mixed with sediment from other sources, what proportion of anthropogenic sediment is required for the deposit to be considered LS? Or how intensive must land-use change have been in how much of

the catchment? If DNA ligase LS is a chronologic unit that begins with the onset of settlement, does it stop being formed with primary deposition, or does it continue to propagate through reworking? Is there a minimum thickness to LS or are areas of deposits included that pinch out laterally or longitudinally? Is there a minimum extent? Specifying answers to all of these questions is not necessary for a broad concept of LS to be useful, but the questions demonstrate vagueness often associated with the present use of the term and the need for a definition that provides some clear constraints. A Legacy Sediment Workgroup—established by the Pennsylvania Department of Environmental Protection (PDEP) to evaluate historical alluvium in Pennsylvania—generated two definitions of LS for use within the Pennsylvania regional context.