Trees on City Streets Cope with Drought by Drinking From Leaky Pipes

For gasoline, all production had to be centralized in a few refineries. The lead would have been shipped in, and would have been largely the same quality and age, likely coming from the same mine, or geographically close mines. Plus the absolute quantity of lead added to gasoline is relatively small. In the 60 years the US used TEL, we processed about 8 million tons of lead. Averaged out, it's 133 thousand tons a year. It would only take a few mines to provide that much. Probably not more than five or ten, but I can't immediately find good data on this.

One would expect that the lead used in gasoline is pretty homogeneous across time, and that intensive lead use (as in casting into solid metal object like pipes) would use the nearest available source, and use that source for as long as possible.

Not all leaded gasoline was the same either:

> 206Pb/207Pb ratios commonly found in Pb ores throughout the world range between 16.0–18.5 and 1.19–1.25, respectively (Hansmann and Köppel, 2000). Exception to this rule is the commonly used Pb ore from the Broken Hill deposit, Australia, which is characterised by extremely low 206Pb/207Pb ratios (1.03–1.10). On the other hand, Pb originating from the Mississippi Valley ore deposit, USA, exhibits significantly more radiogenic Pb isotopic composition (206Pb/204Pb N20.0; 206Pb/207Pb= 1.31–1.35) (Doe and Delevaux, 1972). American leaded gasoline reflected therefore significantly higher 206Pb/207Pb ratios compared to European gasoline (Fig. 1). The introduction of the European leaded gasoline around 1945 resulted in a steep decrease of the 206Pb/207Pb ratio of atmospheric Pb (Weiss et al., 1999; data from peat deposits). The isotopic composition of leaded gasoline was to some extent dependent on economical factors, such as the availability and price of Pb ores and has evolved due to the different Pb ores used. For example, Pb used for French leaded gasoline originated from Australian, Moroccan and Swedish ores and the contribution of the separate ores changed during time (Véron et al., 1999). It is therefore indispensable to gather data concerning the origin of gasoline used in studied regions.

[from https://sci-hub.ru/https://doi.org/10.1016/j.envint.2007.10....]

1: https://en.m.wikipedia.org/wiki/Tetraethyllead

Considering the difficulty and cost of repairing underground anything, most of which will be there for many many decades, it's never going to be perfect, but there's a lot of resources that do go into improving this.

Contamination rarely happens outside of the source of supply, and not somewhere along the pipeline.

Not much, because the water mains pressure keeps nasty things from entering the pipe.

However, when the system is depressurized due to a power outage or due to running out of water, nasty things can happen (stuff entering the water pipes, oxygen from air bubbles causing rust), and that's why after such events boil-off orders are issued for a few weeks afterwards until it can be reasonably assumed that all pipes have been flushed and all air bubbles have gone.

  >Since street trees can’t get much of this from rainwater, which falls on concrete and drains into the city’s sewers, Poirier says the most likely explanation is ...

  I feel like this is burying the lede. What can be done to reduce leakage?

This is hardly a pipe dream. Village Homes demonstrated the concept[0] over five decades ago.

[0] https://www.youtube.com/watch?v=zZ7RmsJOlgc&t=980s

Do we really want that? Thousands of people are being killed each year by heat strokes. Keeping those trees alive by its environmental services is much more valuable in terms of lives and also energy saved. Maples have soft big leaves but also reduce the asphalt temperature by 5-10 degrees. If required just plant a tree species that can live with less water.

In my region, the street trees are usually getting sewer water. Residential service in older houses are usually clay pipes with lead solder that the tree infiltrates. It’s not a problem until the clay pops and roots clog it.

It varies a lot by region and jurisdiction. One of the cities near me made the mistake of using riveted pipe from rolled steel to save money 75 years ago, and regularly has catastrophic main breaks as the rivets aren’t as robust as a regular pipe.

https://www.kxan.com/investigations/city-of-austin-pipes-lea...

One morning in spring, after I'd been living there about 15 years, the neighborhood streets flooded. There were geysers of water shooting up from manholes. Turns out, the willows had been planted over an irrigation ditch[1]. The willows had driven their tap roots into the pipeline and plugged it about 10' underground. When the water authority opened gates miles upstream, the water pressure blew water up the manholes into the streets and a few yards.

Farmers are very motivated to get their water. They, and the ditch company, rapidly cleared the plug and removed the trees.

Before this happened I had no idea the irrigation system ran through the property. I knew about an easement, but I thought it was for sewage, because the developer used an iron manhole cover from the local municipal waste management operation when they covered the irrigation ditch: it literally had "Sewer" cast into the iron.

[1] Formerly an actual ditch, later made into a pipeline and covered over, but still technically a "ditch" for purposes of water management.

Trees have led the humans to channel water and irrigate them so they survive even in dry and isolated soil, and provide shade for urban areas in exchange.